,transcrib]'s ,note3 ,text & ,text repres5t italic & bold text respectively4 ,subscripts are display$ z an und]score foll[$ by ! numb] or text 9 braces3 ,si,o#b4 99 99 99 99 99 ,illu/ration3 ,a ,valley ) ,rocky ,l$ges cut 9 ! ,horizontal ,/rata1 ,scotl& ,,! ,,elem5ts ,,( ,,geology ,,by ,,william ,,h>mon ,,norton ,,pr(essor ,,( ,,geology ,,9 ,,cornell ,,college ,,g9n ,,company ,,bo/on 99 ,,new ,,york 99 ,,*icago 99 ,,london ,copyright1 #aije1 #aiba1 by ,,william ,,h>mon ,,norton ,,all ,,rights ,,res]v$ #eeaa ,! ,a!neum ,press ,,g9n ,,company ,,proprietors ,,bo/on 99 ,u4,s4,a4 ,,preface ,geology is a sci5ce ( su* rapid gr[? t no apology is expect$ :5 f "t to "t a new text-book is add$ to ^? already 9 ! field4 ,! pres5t "w1 h[ev]1 is ! outcome ( ! ne$ ( a text-book ( v simple outl9e1 9 :i* causes & _! consequ5ces %\ld be knit toge!r z closely z possible1--a ne$ long felt by ! au?or 9 8 tea*+1 & p]haps by o!r tea*]s also4 ,! au?or has v5tur$1 !re=e1 to dep>t f ! common usage :i* subdivides geology into a numb] ( dep>tm5ts1--dynamical1 /ructural1 physiographic1 & hi/orical1--& to treat 9 imm$iate connection ) ea* geological process ! l& =ms & ! rock /ructures :i* x has produc$4 ,x is hop$ t ! facts ( geology & ! inf]5ces drawn f !m h be5 s pres5t$ z to af=d an effici5t discipl9e 9 inductive reason+4 ,typical examples h be5 us$ to introduce _m topics1 & x has be5 ! au?or's aim to give due proportion to bo? ! wide g5]alizations ( our sci5ce & to ! concrete facts on :i* !y re/4 ,!re h be5 add$ a numb] ( practical ex]cises su* z ! au?or has us$ = sev]al ye>s 9 ! class room4 ,^! are n made s num]\s z to displace ! problems :i* no d\bt _m tea*]s pref] to h _! pupils solve impromptu dur+ ! recitation1 b may1 x is hop$1 sugge/ _! use4 ,9 hi/orical geology a broad view is giv5 ( ! developm5t ( ! ,nor? ,am]ican cont95t & ! evolution ( life ^u ! planet4 ,only ! lead+ types ( plants & animals are m5tion$1 & special att5tion is giv5 to ^? :i* m>k ! l9es ( desc5t ( =ms n[ liv+4 ,by omitt+ mu* te*nical detail ( a m9]alogical & palontological nature1 & by conf9+ ! field ( view almo/ :olly to our own cont95t1 space has be5 obta9$ to give to :at are deem$ = beg9n]s ! ess5tials ( ! sci5ce a full] treatm5t ?an p]haps is common4 ,x is assum$ t field "w w be introduc$ ) ! comm5cem5t ( ! /udy4 ,! common rocks are !re=e briefly describ$ 9 ! op5+ *apt]s4 ,! drift also receives e>ly m5tion1 & tea*]s 9 ! nor!rn /ates :o beg9 geology 9 ! fall may pref] to take up ! *apt] on ! ,plei/oc5e imm$iately aft] ! *apt] on glaci]s4 ,simple diagrams h be5 us$ freely1 n only because !y are (t5 cle>] ?an any v]bal /atem5t1 b also because !y readily l5d !mselves to reproduction on ! blackbo>d by ! pupil4 ,! text w sugge/ o!rs :i* ! pupil may inv5t4 ,x is hop$ t ! photographic views may also be us$ = ex]cises 9 ! class room4 ,! g5]\s aid ( _m fri5ds is recogniz$ ) special pleasure4 ,to ,pr(essor ,w4 ,m4 ,davis ( ,h>v>d ,univ]sity !re is ow+ a l>ge obligation = ! broad conceptions & lum9\s /atem5ts ( geologic facts & pr9ciples ) :i* he has enri*$ ! lit]ature ( our sci5ce1 & = 8 /imulat+ influ5ce 9 education4 ,x is hop$ t bo? 9 subject-matt] & 9 me?od ! book itself makes evid5t ?is debt4 ,b besides a g5]al obligation %>$ by geologi/s ev]y:]e1 & 9 v>y+ degrees by p]haps all au?ors ( rec5t ,am]ican text-books 9 e>? sci5ce1 !re is ow+ a debt direct & p]sonal4 ,! plan ( ! book1 ) its use ( problems & treatm5t ( l& =ms & rock /ructures 9 imm$iate connection ) ! processes :i* produce !m1 0 submitt$ to ,pr(essor ,davis1 &1 receiv+ 8 approval1 0 c>ri$ into effect1 al?\gh )\t ! sanction ( prec$5t at ! "t4 ,pr(essor ,davis also k9dly cons5t$ to read ! manuscript ?r\gh\t1 & 8 _m helpful criticisms & sugge/ions are ackn[l$g$ ) s9c]e gratitude4 ,p>ts ( ! manuscript h be5 review$ by ,dr4 ,samuel ,calv9 & ,dr4 ,frank ,m4 ,wild] ( ! ,/ate ,univ]sity ( ,i[a2 ,dr4 ,s4 ,w4 ,bey] ( ! ,i[a ,college ( ,agriculture & ,me*anic ,arts2 ,dr4 ,u4 ,s4 ,grant ( ,nor?we/]n ,univ]sity2 ,pr(essor ,j4 ,a4 ,udd5 ( ,augu/ana ,college1 ,ill9ois2 ,dr4 ,c4 ,h4 ,gordon ( ! ,new ,mexico ,/ate ,s*ool ( ,m9es2 ,pr9cipal ,maurice ,rick] ( ! ,high ,s*ool1 ,burl+ton1 ,i[a2 & ! foll[+ =m] /ud5ts ( ! au?or :o are engag$ 9 ! e>? sci5ces3 ,dr4 ,w4 ,c4 ,ald5 ( ! ,unit$ ,/ates ,geological ,survey & ! ,univ]sity ( ,*icago2 ,mr4 ,joseph ,sniff51 in/ructor 9 ! ,academy ( ! ,univ]sity ( ,*icago1 ,morgan ,p>k2 ,pr(essor ,m>t9 ,iorns1 ,=t ,wor? ,univ]sity1 ,texas2 ,pr(essor ,a4 ,m4 ,jayne1 ,dakota ,univ]sity2 ,pr(essor ,g4 ,h4 ,bretnall1 ,monm\? ,college1 ,ill9ois2 ,pr(essor ,h[>d ,e4 ,simpson1 ,colby ,college1 ,ma9e2 ,mr4 ,e4 ,j4 ,cable1 in/ructor 9 ! ,i[a ,/ate ,normal ,college2 ,pr9cipal ,c4 ,c4 ,gray ( ! ,high ,s*ool1 ,f>go1 ,nor? ,dakota2 & ,mr4 ,*>les ,p]sons ( ! ,high ,s*ool1 ,hannibal1 ,miss\ri4 ,a l>ge numb] ( ! diagrams ( ! book 7 drawn by ,mr4 ,w4 ,w4 ,:ite ( ! ,art ,s*ool ( ,cornell ,college4 ,to all ^! fri5ds1 & to ! _m :o h k9dly suppli$ ! illu/rations ( ! text1 ^: names are m5tion$ 9 an app5d$ li/1 ! writ] returns 8 he>tfelt ?anks4 ,,william ,,h>mon ,,norton ,cornell ,college1 ,m\nt ,v]non1 ,i[a ,july1 #aije ,,introductory ,,note ,dur+ ! prep>ation ( ?is book ,pr(essor ,norton has frequ5tly discuss$ its plan ) me by correspond5ce1 & we h consid]$ toge!r ! matt]s ( scope1 arrangem5t1 & pres5tation4 ,z to scope1 ! ne$s ( ! "y /ud5t & n ( ! exp]t h be5 our guide2 ! book is !re=e a text-book1 n a ref]5ce volume4 ,9 arrangem5t1 ! tw(old division ( ! subject 0 *os5 because ( its simplicity & effectiv5ess4 ,! pr9ciples ( physical geology come fir/2 ! sev]al *apt]s are arrang$ 9 :at is believ$ to be a natural ord]1 appropriate to ! greate/ "p ( our c\ntry1 s t f a simple beg9n+ a logical sequ5ce ( topics leads ?r\gh ! :ole subject4 ,! hi/orical view ( ! sci5ce comes second1 ) _m specific illu/rations ( ! physical processes previ\sly /udi$1 b n[ set =? z "p ( ! /ory ( ! e>?1 ) its _m *anges ( aspect & its succession ( inhabitants4 ,special att5tion is "h giv5 to ,nor? ,am]ica1 & c>e is tak5 to avoid ov]load+ ) details4 ,) respect to me?od ( pres5tation1 x mu/ n be =gott5 t ! text-book is only "o factor 9 good tea*+1 & t 9 geology1 z 9 o!r sci5ces1 ! tea*]1 ! laboratory1 & ! local field are o!r factors1 ea* ( :i* %\ld play an appropriate "p4 ,! text sugge/s obs]vational me?ods1 b x _c replace obs]vation 9 field or laboratory2 x (f]s c]ta9 ex]cises1 b space _c be tak5 to make x a laboratory manual z well z a book = /udy2 x expla9s _m problems1 b its /atem5ts are necess>ily m t]se ?an ! illu/rative descriptions t a good & exp]i5c$ tea*] %\ld supply4 ,frequ5t use is made ( induction & inf]5ce 9 ord] t ! /ud5t may come to see h[ reasonable a sci5ce is geology1 & t he may avoid ! too common error ( ?9k+ t ! op9ions ( au?orities are rea*$ by a private road t is clos$ to him4 ,! fur!r ext5sion ( ?is me?od ( pres5tation is urg$ ^u ! tea*]1 s t ! "y geologi/ may always le>n ! evid5ce t leads to a conclusion1 & n only ! conclusion itself4 ,w4 ,m4 ,,davis ,h>v>d ,univ]sity1 ,cambridge1 ,mass4 ,july1 #aije ,,ackn[l$gm5t ,,( ,,illu/rations ,adams1 ,pr(essor ,f4 ,d41 ,mc,gill ,univ]sity1 ,canada1 #bda4 ,ald51 ,dr4 ,w4 ,c41 ,wa%+ton1 ,d4,c41 #cec4 ,am]ican ,museum ( ,natural ,hi/ory1 ,new ,york1 #cdd4 ,a%1 ,h4 ,c41 ,galesburg1 ,ill41 #acc4 ,bey]1 ,dr4 ,s4 ,w41 ,i[a ,college ( ,agriculture1 #cfc4 ,calv91 ,dr4 ,samuel1 ,i[a ,/ate ,univ]sity1 #de1 #bie1 #cag1 #cbe1 #cga4 ,c>ney1 ,frank1 ,i?aca1 ,n4,y41 #cef4 ,cl>k1 ,dr4 ,wm4 ,b41 ,m>yl& ,geological ,survey1 #dc4 ,borne1 ,dr4 ,georg v4 d41 ,j5a1 ,g]many1 #e1 #f4 ,daly1 ,dr4 ,r4 ,a41 ,ottawa1 ,canada1 #afd4 ,defieux1 ,c4 ,a41 ,liv]pool1 ,engl&1 #aed4 99 ,detroit ,photographic ,co41 #bce1 #bcf4 99 ,ellis1 ,w4 ,m41 ,edna1 ,kan41 #ac4 ,fair*ild1 ,pr(essor ,h4 ,l41 ,univ]sity ( ,ro*e/]1 #ada1 #ceg4 ,field ,columbian ,museum1 ,*icago1 #hg4 ,=/]1 ,dr4 ,a4 ,e41 ,univ]sity ( ,vi5na1 #cb4 ,g>dn]1 ,j4 ,l41 ,bo/on1 #ab1 #adj1 #ceb4 ,geological ,survey ( ,canada1 #bef4 ,gilb]t1 ,dr4 ,g4 ,k41 by c\rtesy ( ! ,am]ican ,book ,company1 #ci4 99 ,ha9es1 ,b51 ,new ,albany1 ,ind41 #cc4 99 ,haynes1 ,f4 ,j41 ,/4 ,paul1 ,m9n41 #eb1 #ie1 #bcc4 ,h5d]son1 ,judge ,julius1 ,b\ld]1 ,col41 #id4 ,james1 ,george ,:>ton1 ,pasad5a1 ,cal41 #af1 #abg1 #bae1 #bbi4 ,john/on-,lavis1 ,pr(essor ,h4 ,j41 ,beaulieu1 ,france1 #baf4 ,k+1 ,j4 ,h>d+1 ,/\rbridge1 ,engl&1 #aai4 ,lawson1 ,dr4 ,&rew ,c41 ,univ]sity ( ,cali=nia1 #aac4 ,le ,conte1 ,pr(essor ,j4 ,n41 ,univ]sity ( ,cali=nia1 #h4 ,libbey1 ,dr4 ,william1 ,pr9ceton ,univ]sity1 #ib4 99 ,mc,allister1 ,t4 ,h41 ,new ,york1 #bdb4 99 ,mey]s1 ,h4 ,c41 ,boise1 ,id41 #ai4 ,mills1 ,pr(essor ,h4 ,a41 ,cornell ,college1 #bjh1 #cjd4 ,norton1 ,pr(essor ,w4 ,h41 ,cornell ,college1 #ad1 #ce1 #ei1 #hh1 #abh1 #ahc1 #bbf1 #bcd1 #bee1 #cdj1 #cfd1 #cfg4 99 ,notman1 ,wm4 ,son1 ,montreal1 ,canada1 #ih1 #aha4 ,obruts*ew1 ,dr4 ,w41 ,tomsk ,te*nological ,in/itute1 ,sib]ia1 #gc4 ,oldham1 ,dr4 ,r4 ,d41 ,geological ,survey ( ,india1 #abj4 99 ,peabody1 ,h4 ,c41 ,pasad5a1 ,cal41 #ed4 99 ,pi]ce1 ,c4 ,c4 ,co41 ,los ,angeles1 ,cal41 #ae4 ,pillsbury1 ,ar?ur1 ,san ,francisco1 ,cal41 4#aae4 99 ,rau1 ,wm41 ,philadelphia1 #ah1 #ba1 #abb1 #abc1 #bah4 ,reus*1 ,dr4 ,hans1 ,geological ,survey ( ,norway1 #aab4 ,reynolds1 ,pr(essor ,s4 ,h41 ,univ]sity ,college1 ,bri/ol1 ,engl&1 #bjb4 ,rick]1 ,pr9cipal ,maurice1 ,burl+ton1 ,i[a1 #dh1 #hi4 99 ,%ep>d1 ,e4 ,a41 ,m9neapolis1 ,m9n41 #aje4 ,smi?1 ,w4 ,s4 ,tangi]1 ,los ,gatos1 ,cal41 #ahf4 99 ,s\le ,photographic ,co41 ,bo/on1 #aca4 ,u4 ,s4 ,geological ,survey1 #c1 #d1 #bc1 #be1 #cd1 #da1 #fc1 #fi1 #gh1 #gi1 #hj1 #aaj1 #aaa1 #aad1 #abe1 #abf1 #abi1 #acj1 #adb1 #aea1 #aec1 #afi1 #agb1agg1 #agh1 #ahh1 #baa1 #bab1 #bad1 #bbh1 #bcg1 #bch1 #bci1 #bdc1 #bdd1 #bed1 #beg1 #cdj1 #cda1 #cec1 #cee4 ,u4 ,s4 ,national ,museum1 #adi1 #bbj1 #bba1 #bbb1 #bbe1 #ccb4 99 ,val5t9e ,sons1 ,dundee1 ,scotl&1 #dj1 #acf1 #bbg4 ,vroman1 ,a4 ,c41 ,pasad5a1 ,cal41 #ag4 99 ,w>d's ,natural ,sci5ce ,e/abli%m5t1 ,ro*e/]1 ,n4,y41 #aeb4 99 ,wel*1 ,r41 ,belfa/1 ,irel&1 #a1 #cg4 99 ,we/gate1 ,dr4 ,l4 ,g41 ,ohio ,wesleyan ,univ]sity1 #ff4 ,:ymp]1 ,edw>d1 ,london1 ,engl&1 #ajf4 99 ,wilcox1 ,w4 ,d41 ,wa%+ton1 ,d4,c41 #bj4 99 ,wilson1 ,dr4 ,a4 ,w4 ,g41 ,mc,gill ,univ]sity1 ,canada1 #fh4 99 ,wilson1 ,g4 ,w41 ,co41 ,ab]de51 ,scotl&1 #hb1 #bac4 99 ,worsley-,b5ison1 ,f4 ,h41 ,*eap/[1 ,engl&1 #agj4 99 ,deal] 9 photographs or lant]n slides4 ,,cont5ts ,page ,introduction4--,! ,scope ,& ,aim ,( ,geology #a ,,"p ,i ,,ext]nal ,,geological ,,ag5cies ,*apt] ,i4 ,! ,"w ,( ,! ,wea!r #e ,,ii4 ,! ,"w ,( ,gr\nd ,wat] #ci ,,iii4 ,riv]s ,& ,valleys #ed ,,iv4 ,riv] ,deposits #ic ,v4 ,! ,"w ,( ,glaci]s #aac ,,vi4 ,! ,"w ,( ,! ,w9d #add ,,vii4 ,! ,sea ,& ,its ,%ores #aee ,,viii4 ,(f%ore ,& ,deep-,sea ,deposits #agd ,,"p ,,ii ,,int]nal ,,geological ,,ag5cies ,,ix4 ,movem5ts ,( ,! ,e>?'s ,cru/ #aie ,x4 ,e>?quakes #bcc ,,xi4 ,volcanoes #bch ,,xii4 ,und]gr\nd ,/ructures ,( ,igne\s ,orig9 #bfe ,,xiii4 ,metamorphism ,& ,m9]al ,ve9s #bha ,,"p ,,iii ,,hi/orical ,,geology ,,xiv4 ,! ,geological ,record #bia ,,xv4 ,! ,pre-,cambrian ,sy/ems #cjd ,,xvi4 ,! ,cambrian #cae ,,xvii4 ,! ,ordovician ,& ,silurian #cbg ,,xviii4 ,! ,devonian #cda ,,xix4 ,! ,c>bonif]\s #cej ,,xx4 ,! ,mesozoic #cfh ,,xxi4 ,! ,t]ti>y #cid ,,xxii4 ,! ,quat]n>y #daf ,,index #dea ,,! ,,elem5ts ,,( ,,geology ,,introduction ,,! ,,scope ,,& ,,aim ,,( ,,geology ,geology deals ) ! rocks ( ! e>?'s cru/4 ,x le>ns f _! composition & /ructure h[ ! rocks 7 made & h[ !y h be5 modifi$4 ,x asc]ta9s h[ !y h be5 br\ght to _! pres5t places & wr\ght to _! v>i\s topographic =ms1 su* z hills & valleys1 pla9s & m\nta9s4 ,x /udies ! ve/iges :i* ! rocks pres]ve ( anci5t organisms :i* once inhabit$ our planet4 ,geology is ! hi/ory ( ! e>? & its inhabitants1 z read 9 ! rocks ( ! e>?'s cru/4 ,to obta9 a g5]al idea ( ! nature & me?od ( our sci5ce be=e beg9n+ its /udy 9 detail1 we may visit "s valley1 su* z t illu/rat$ 9 ! frontispiece1 on ^: sides are rocky l$ges4 ,"h ! rocks lie 9 horizontal lay]s4 ,al?\gh only _! edges are expos$1 we may inf] t ^! lay]s run into ! upl& on ei!r side & und]lie ! entire di/rict2 !y are "p ( ! f\ndation ( solid rock :i* ev]y:]e is f\nd b5ea? ! loose mat]ials ( ! surface4 ,! l$ges ( ! valley ( our illu/ration are ( s&/one4 ,look+ closely at ! rock we see t x is compos$ ( myriads ( gra9s ( s& cem5t$ toge!r4 ,^! gra9s h be5 worn & r\nd$4 ,!y are sort$ also1 ^? ( ea* lay] be+ ab\t ( a size4 ,by "s means !y h be5 br\ght hi!r f "s m anci5t s\rce4 ,surely ^! gra9s h _h a hi/ory be=e !y "h f\nd a re/+ place1--a hi/ory :i* we are to le>n to read4 ,! successive lay]s ( ! rock sugge/ t !y 7 built "o aft] ano!r f ! bottom upw>d4 ,we may be z sure t ea* lay] 0 =m$ be=e ^? above x z t ! bottom c\rses ( /one 9 a wall 7 laid be=e ! c\rses :i* re/ ^u !m4 ,we h no reason to believe t ! l[e/ lay]s :i* we see "h 7 ! e>lie/ ev] =m$4 ,inde$1 "s deep bor+ 9 ! vic9ity may prove t ! l$ges re/ ^u o!r lay]s ( rock :i* ext5d d[nw>d = _m hundr$s ( feet bel[ ! valley floor4 ,nor may we conclude t ! highe/ lay]s "h 7 ! late/ ev] laid2 = else:]e we may f9d /ill lat] lay]s ly+ ^u !m4 ,a %ort se>* may f9d 9 ! rock relics ( animals1 su* z ! impr9ts ( %ells1 :i* liv$ :5 x 0 deposit$2 & z ^! are ( k9ds ^: ne>e/ liv+ relatives n[ h _! home 9 ! sea1 we inf] t x 0 on ! flat sea floor t ! s&/one 0 laid4 ,its pres5t position hundr$s ( feet above sea level proves t x has s9ce em]g$ to =m "p ( ! l&2 :ile ! flatness ( ! b$s %[s t ! movem5t 0 s uni=m & g5tle z n to break or /rongly b5d !m f _! orig9al attitude4 ,! surface ( "s ( ^! lay]s is ripple-m>k$4 ,h5ce ! s& mu/ once h be5 z loose z t ( %all[ sea bottoms & sea bea*es to-day1 :i* is ?r[n into simil> ripples by movem5ts ( ! wat]4 ,9 "s way ! gra9s h s9ce become cem5t$ into firm rock4 ,note t ! lay]s on "o side ( ! valley agree ) ^? on ! o!r1 ea* mat*+ ! "o opposite at ! same level4 ,once !y 7 cont9u\s across ! valley4 ,:]e ! valley n[ is 0 once a cont9u\s upl& built ( horizontal lay]s2 ! lay]s n[ %[ _! edges1 or outcrop1 on ! valley sides because !y h be5 cut by ! valley tr5*4 ,! rock ( ! l$ges is crumbl+ away4 ,at ! foot ( ea* /ep ( rock lie fragm5ts :i* h fall54 ,?us ! valley is sl[ly wid5+4 ,x has be5 n>r[] 9 ! pa/2 x w be wid] 9 ! future4 ,?r\gh ! valley runs a /ream4 ,! wat]s ( ra9s :i* h fall5 on ! upp] p>ts ( ! /ream's bas9 are n[ on _! way to ! riv] & ! sea4 ,rock fragm5ts & gra9s ( s& creep+ d[n ! valley slopes come )9 rea* ( ! /ream & are wa%$ along by ! runn+ wat]4 ,"h & !re !y lodge = a "t 9 banks ( s& & gravel1 b soon] or lat] !y are tak5 up aga9 & c>ri$ on4 ,! gra9s ( s& :i* 7 br\ght f "s anci5t s\rce to =m ^! rocks are on _! way to "s new goal4 ,z !y are wa%$ along ! rocky b$ ( ! /ream !y sl[ly rasp & we> x deep]4 ,! valley w be deep] 9 ! future2 x has be5 less deep 9 ! pa/4 ,9 ?is little valley we see sl[ *anges n[ 9 progress4 ,we f9d also 9 ! composition1 ! /ructure1 & ! attitude ( ! rocks1 & ! l& =ms to :i* !y h be5 sculptur$1 ! record ( a long succession ( pa/ *anges involv+ ! orig9 ( s& gra9s & _! ga!r+ & deposit ^u ! bottom ( "s anci5t sea1 ! cem5tation ( _! lay]s into solid rock1 ! uplift ( ! rocks to =m a l& surface1 &1 la/ ( all1 ! c>v+ ( a valley 9 ! upl&4 ,ev]y:]e1 9 ! fields1 along ! riv]1 among ! m\nta9s1 by ! sea%ore1 & 9 ! des]t1 we may discov] sl[ *anges n[ 9 progress & ! record ( simil> *anges 9 ! pa/4 ,ev]y:]e we may cat* glimpses ( a process ( gradual *ange1 :i* /ret*es backw>d into ! pa/ & =w>d into ! future1 by :i* ! =ms & /ructures ( ! face ( ! e>? are cont9ually built & cont9ually de/roy$4 ,! sci5ce :i* deals ) ?is long process is geology4 ,geology treats ( ! natural *anges n[ tak+ place ^u ! e>? & )9 x1 ! ag5cies :i* produce !m1 & ! l& =ms & rock /ructures :i* result4 ,x /udies ! *anges ( ! pres5t 9 ord] to be able to read ! hi/ory ( ! e>?'s *anges 9 ! pa/4 ,! v>i\s ag5cies :i* h fa%ion$ ! face ( ! e>? may4 be divid$ into two g5]al classes4 ,9 ,"p ,i we %all consid] ^? :i* "w ^u ! e>? f )\t1 su* z ! wea!r1 runn+ wat]1 glaci]s1 ! w9d1 & ! sea4 ,9 ,"p ,,ii we %all treat ( ^? ag5cies ^: s\rces are )9 ! e>?1 & among ^: manife/ations are volcanoes & e>?quakes & ! v>i\s movem5ts ( ! e>?'s cru/4 ,z we /udy ea* ag5cy we %all notice n only h[ x does its "w1 b also ! records :i* x leaves 9 ! rock /ructures & ! l& =ms :i* x produces4 ,) ?is prep>ation we %all be able 9 ,"p ,,iii to read 9 ! records ( ! rocks ! hi/ory ( our planet & ! successive =ms ( life :i* h dwelt ^u x4 ,"p ,i ,,ext]nal ,,geological ,,ag5cies ,,*apt] ,i ,,! ,,"w ,,( ,,! ,,wea!r ,9 our excursion to ! valley ) s&/one l$ges we witness$ a process :i* is go+ =w>d 9 all l&s4 ,ev]y:]e ! rocks are crumbl+ away2 _! fragm5ts are creep+ d[n hillsides to ! /ream ways & are c>ri$ by ! /reams to ! sea1 :]e !y are rebuilt into rocky lay]s4 ,:5 aga9 ! rocks are lift$ to =m l& ! process w beg9 anew2 aga9 !y w crumble & creep d[n slopes & be wa%$ by /reams to ! sea4 ,let u beg9 our /udy ( ?is long cycle ( *ange at ! po9t :]e rocks dis9tegrate & decay "u ! action ( ! wea!r4 ,9 /udy+ n[ a few outcrops & qu>ries we %all le>n a little ( "s common rocks & h[ !y wea!r away4 ,/ratification & jo9t+4 ,at ! s&/one l$ges we saw t ! rock 0 divid$ into p>allel lay]s4 ,! ?ick] lay]s are kn[n z /rata1 & ! ?9 leaves into :i* ea* /ratum may sometimes be split are t]m$ lam94 ,to a great] or less degree ^! lay]s diff] f ea* o!r 9 f95ess ( gra91 %[+ t ! mat]ial has be5 sort$4 ,! planes :i* divide !m are call$ b$d+ planes4 ,besides ! b$d+ planes !re are o!r division planes1 :i* cut across ! /rata f top to bottom4 ,^! are f\nd 9 all rocks & are kn[n z jo9ts 7,fig4 #a74 ,two sets ( jo9ts1 runn+ at ab\t "r angles to ea* o!r1 toge!r ) ! b$d+ planes1 divide ! s&/one into quadrangul> blocks4 ,illu/ration3 ,fig4 #a4 ,cliff ( ,s&/one1 ,irel& ,s&/one4 ,exam9+ a piece ( s&/one we f9d x compos$ ( gra9s q l ^? ( riv] s& or ( sea bea*es4 ,mo/ ( ! gra9s are ( a cle> glassy m9]al call$ qu>tz4 ,^! qu>tz gra9s are v h>d & w scrat* ! /eel ( a knife blade4 ,!y are n affect$ by acid1 & _! brok5 surfaces are irregul> l ^? ( brok5 glass4 ,! gra9s ( s&/one are held toge!r by "s cem5t4 ,?is may be calc>e\s1 consi/+ ( soluble c>bonate ( lime4 ,9 br[n s&/ones ! cem5t is commonly f]rug9\s1--hydrat$ iron oxide1 or iron ru/1 =m+ ! bond1 some:at z 9 ! case ( iron nails :i* h ru/$ toge!r4 ,! /ronge/ & mo/ la/+ cem5t is silice\s1 & s& rocks ^: gra9s are closely cem5t$ by silica1 ! *emical sub/ance ( :i* qu>tz is made1 are kn[n z qu>tzites4 ,we are n[ prep>$ to und]/& h[ s&/one is affect$ by ! action ( ! wea!r4 ,on l$ges :]e ! rock is expos$ to view its surface is m or less discolor$ & ! gra9s are loose & may be rubb$ (f ) ! f+]4 ,on g5tle slopes ! rock is cov]$ ) a soil compos$ ( s&1 :i* evid5tly is crumbl$ s&/one1 & d>k c>bonace\s matt] d]iv$ f ! decay ( vegetation4 ,cle>ly x is by ! dissolv+ ( ! cem5t t ! rock ?us breaks d[n to loose s&4 ,a piece ( s&/one ) calc>e\s cem5t1 or a bit ( old mort>1 :i* is really an artificial /one also made ( s& cem5t$ by lime1 may be treat$ 9 a te/ tube ) hydro*loric acid to illu/rate ! process4 ,illu/ration3 ,fig4 #b4 ,section ( ,lime/one ,qu>ry ,scale1 #a 94 #cj ft4 a1 r$ residual clay2 mn1 pitt$ surface ( rott$ lime/one2 bb1 lime/one divid$ into ?9 lay]s2 c1 ?ick lay]s ( lam9at$ lime/one1 ! lam9 be+ firmly cem5t$ toge!r2 j1 j1 j1 jo9ts4 ,is bb ?9-lay]$ because orig9ally s laid1 or because x has be5 brok5 up by wea!r+1 al?\gh once l c ?ick-lay]$8 ,a lime/one qu>ry4 ,"h also we f9d ! rock /ratifi$ & jo9t$ 7,fig4 #b74 ,on ! qu>ry face ! rock is di/9ctly se5 to be alt]$ = "s di/ance f its upp] surface4 ,bel[ ! alt]$ zone ! rock is s\nd & is qu>ri$ = build+2 b ! alt]$ upp] lay]s are too s(t & brok5 to be us$ = ?is purpose4 ,if ! lime/one is lam9at$1 ! lam9ae "h h split ap>t1 al?\gh bel[ !y hold fa/ toge!r4 ,ne> ! surface ! /one has become rott5 & crumbles at ! t\*1 :ile on ! top x has completely brok5 d[n to a ?9 lay] ( lime/one meal1 on :i* re/s a f9e r$di% clay4 ,lime/one is made ( m9ute gra9s ( c>bonate ( lime all firmly held toge!r by a calc>e\s cem5t4 ,a piece ( ! /one plac$ 9 a te/ tube ) hydro*loric acid dissolves ) brisk eff]vesc5ce1 leav+ ! insoluble impurities1 :i* 7 dissem9at$ ?r\gh x1 at ! bottom ( ! tube z a little clay4 ,we c n[ und]/& ! *anges 9 ! upp] lay]s ( ! qu>ry4 ,at ! surface ( ! rock ! lime/one has completely dissolv$1 leav+ ! insoluble residue z a lay] ( r$di% clay4 ,imm$iately bel[ ! clay ! rock has dis9tegrat$ into meal :]e ! cem5t betwe5 ! lime/one gra9s has be5 remov$1 :ile b5ea? ?is ! lam9ae are split ap>t :]e ! cem5t has be5 dissolv$ only along ! planes ( lam9ation :]e ! /one is m por\s4 ,z ^! *anges 9 ! rock are greate/ at ! surface & dim9i% d[nw>d1 we inf] t !y h be5 caus$ by ag5ts work+ d[nw>d f ! surface4 ,at c]ta9 po9ts ^! ag5cies h be5 m effective ?an else:]e4 ,! upp] rock surface is pitt$4 ,jo9ts are wid5$ z !y approa* ! surface1 & along ^! seams we may f9d t ! rock is alt]$ ev5 d[n to ! qu>ry floor4 ,a %ale pit4 ,let u n[ visit "s pit :]e %ale--a lam9at$ & some:at h>d5$ clay--is qu>ri$ = ! manufacture ( brick4 ,! lam9ae ( ?is f9e-gra9$ rock may be z ?9 z c>dbo>d 9 places1 & close jo9ts may break ! rock into small rhombic blocks4 ,on ! upp] surface we note t ! %ale has wea!r$ to a clayey soil 9 :i* all traces ( /ructure h be5 de/roy$4 ,! clay & ! upp] lay]s ( ! %ale b5ea? x are r$di% or yell[1 :ile 9 _m cases ! color ( ! unalt]$ rock b5ea? is blue4 ,! s$im5t>y rocks4 ,! ?ree k9ds ( lay]$ rocks ^: acqua9tance we h made--s&/one1 lime/one1 & %ale--are ! lead+ types ( ! great gr\p ( /ratifi$1 or s$im5t>y1 rocks4 ,?is gr\p includes all rocks made ( s$im5ts1 _! mat]ials hav+ settl$ ei!r 9 wat] ^u ! bottoms ( riv]s1 lakes1 or seas1 or on dry l&1 z 9 ! case ( deposits made by ! w9d & by glaci]s4 ,s$im5t>y rocks are divid$ into ! fragm5tal rocks--:i* are made ( fragm5ts1 ei!r co>se or f9e--& ! f> less common rocks :i* are con/itut$ ( *emical precipitates4 ,illu/ration3 ,fig4 #c4 ,conglom]ate ,! s$im5t>y rocks are divid$ accord+ to _! composition into ! foll[+ classes3 #a4 ,! ar5ace\s1 or qu>tz rocks1 includ+ b$s ( loose s& & gravel1 s&/one1 qu>tzite1 & conglom]ate 7a rock made ( cem5t$ r\nd$ gravel or pebbles74 #b4 ,! calc>e\s1 or lime rocks1 includ+ lime/one & a s(t :ite rock =m$ ( calc>e\s p[d] kn[n z *alk4 #c4 ,! argillace\s1 or clay rocks1 includ+ muds1 clays1 & %ales4 ,^! ?ree classes pass by mixture into "o ano!r4 ,?us !re are limy & clayey s&/ones1 s&y & clayey lime/ones1 & s&y & limy %ales4 ,granite4 ,?is famili> rock may be /udi$ z an example ( ! second great gr\p ( rocks1--! un/ratifi$1 or igne\s rocks4 ,^! are n made ( cem5t$ s$im5t>y gra9s1 b ( int]lock+ cry/als :i* h cry/alliz$ f a molt5 mass4 ,exam9+ a piece ( granite1 ! mo/ conspicu\s cry/als :i* meet ! eye are ^? ( feldsp>4 ,!y are commonly p9k1 :ite1 or yell[1 & break along smoo? cleavage planes :i* reflect ! light l t9y panes ( glass4 ,mica may be recogniz$ by its glitt]+ plates1 :i* split into ?9 ela/ic scales4 ,a ?ird m9]al1 h>d] ?an /eel1 break+ along irregul> surfaces l brok5 glass1 we id5tify z qu>tz4 ,h[ granite alt]s "u ! action ( ! wea!r may be se5 9 outcrops :]e x =ms ! b$ rock1 or c\ntry rock1 und]ly+ ! loose =mations ( ! surface1 & 9 _m p>ts ( ! nor!rn /ates :]e granite b[ld]s & pebbles m or less decay$ may be f\nd 9 a surface %eet ( /ony clay call$ ! drift4 ,( ! diff]5t m9]als compos+ granite1 qu>tz alone rema9s unalt]$4 ,mica wea!rs to deta*$ flakes :i* h lo/ _! ela/icity4 ,! feldsp> cry/als h lo/ _! lu/] & h>dness1 & ev5 h decay$ to clay4 ,:]e long-wea!r$ granite =ms ! c\ntry rock1 x (t5 may be cut ) spade or tr[el = sev]al feet f ! surface1 s rott5 is ! feldsp>1 & "h ! rock is se5 to break d[n to a clayey soil conta9+ gra9s ( qu>tz & flakes ( mica4 ,^! are a few simple illu/rations ( ! surface *anges :i* "s ( ! common k9ds ( rocks und]go4 ,! ag5cies by :i* ^! *anges are br\ght ab\t we w n[ take up "u two divisions1--*emical ag5cies produc+ rock decay & me*anical ag5cies produc+ rock dis9tegration4 ,! ,*emical ,"w ,( ,wat] ,z wat] falls on ! e>? 9 ra9 x has already absorb$ f ! air c>bon dioxide 7c>bonic acid gas7 & oxyg54 ,z x s9ks into ! gr\nd & becomes :at is t]m$ gr\nd wat]1 x takes into solution f ! soil humus acids & c>bon dioxide1 bo? ( :i* are con/antly be+ g5]at$ !re by ! decay ( organic matt]4 ,s bo? ra9 & gr\nd wat] are *>g$ ) active *emical ag5ts1 by ! help ( :i* !y corrode & ru/ & decompose all rocks to a great] or less degree4 ,we notice n[ ?ree ( ! *ief *emical processes conc]n$ 9 wea!r+1--solution1 ! =mation ( c>bonates1 & oxidation4 ,solution4 ,lime/one1 al?\gh s little affect$ by pure wat] t five ?\s& gallons w\ld be ne$$ to dissolve a s+le p\nd1 is easily dissolv$ 9 wat] *>g$ ) c>bon dioxide4 ,9 lime/one regions well wat] is !re=e h>d4 ,on boil+ ! wat] = "s "t ! c>bon dioxide gas is expell$1 ! :ole ( ! lime c>bonate c no long] be held 9 solution1 & mu* ( x is ?r[n d[n to =m a cru/ or scale 9 ! kettle or 9 ! tubes ( ! /eam boil]4 ,all wat]s :i* fl[ ov] lime/one rocks or soak ?r\gh !m are con/antly engag$ 9 dissolv+ !m away1 & 9 ! c\rse ( "t de/roy b$s ( va/ ext5t & great ?ickness4 ,illu/ration3 ,fig4 #d4 ,surface ( ,lime/one furr[$ by ,wea!r+1 ,montana ,! upp] surface ( lime/one rocks becomes deeply pitt$1 z we saw 9 ! lime/one qu>ry1 & :]e ! mantle ( wa/e has be5 remov$ x may be f\nd s intricately furr[$ t x is difficult to trav]se 7,fig4 #d74 ,b$s ( rock salt buri$ among ! /rata are dissolv$ by seep+ wat]1 :i* issues 9 salt spr+s4 ,gypsum1 a m9]al compos$ ( hydrat$ sulphate ( lime1 & s s(t t x may be scrat*$ ) ! f+] nail1 is readily tak5 up by wat]1 giv+ to ! wat] ( wells & spr+s a peculi> h>dness difficult to remove4 ,! dissolv+ action ( moi/ure may be not$ on m>ble tomb/ones ( "s age1 m>ble be+ a lime/one alt]$ by heat & pressure & compos$ ( cry/all9e gra9s4 ,by assum+ t ! date on ea* monum5t m>ks ! ye> ( its erection1 "o may e/imate h[ _m ye>s on ! av]age x has tak5 = wea!r+ to loos5 f9e gra9s on ! poli%$ surface1 s t !y may be rubb$ (f ) ! f+]1 to de/roy ! poli%1 to r\nd ! %>p edges ( tool m>ks 9 ! lett]+1 & at la/ to op5 cracks & seams & break d[n ! /one4 ,we may notice also :e!r ! grave/ones wea!r m rapidly on ! sunny or ! %ady side1 & on ! sides or on ! top4 ,! wea!r$ surface ( granul> lime/one conta9+ %ells %[s !m /&+ 9 relief4 ,z ! %ells are made ( cry/all9e c>bonate ( lime1 we may inf] :e!r ! c>bonate ( lime is less soluble 9 its granul> or 9 its cry/all9e condition4 ,! =mation ( c>bonates4 ,9 attack+ m9]als wat] does m ?an m]ely take !m into solution4 ,x decomposes !m1 =m+ new *emical comp\nds ( :i* ! c>bonates are among ! mo/ important4 ,?us feldsp> consi/s ( ! insoluble silicate ( alum9a1 toge!r ) c]ta9 alkal9e silicates :i* are brok5 up by ! action ( wat] conta9+ c>bon dioxide1 =m+ alkal9e c>bonates4 ,^! c>bonates are freely soluble & contribute pota% & soda to soils & riv] wat]s4 ,by ! removal ( ! soluble +r$i5ts ( feldsp> !re is left ! silicate ( alum9a1 unit$ ) wat] or hydrat$1 9 ! condition ( a f9e pla/ic clay :i*1 :5 :ite & pure1 is kn[n z kaol9 & is us$ 9 ! manufacture ( porcela94 ,feldspa?ic rocks :i* conta9 no iron comp\nds ?us wea!r to :iti% cru/s1 & ev5 app>5tly s\nd cry/als ( feldsp>1 :5 gr\nd to ?9 slices & plac$ "u ! microscope1 may be se5 to be milky 9 color ?r\gh\t because an int]nal *ange to kaol9 has begun4 ,illu/ration3 ,fig4 #e4 ,b[ld] split by ,heat & ,cold1 ,we/]n ,texas ,oxidation4 ,rocks conta9+ comp\nds ( iron wea!r to r$di% cru/s1 & ! seams ( ^! rocks are (t5 l9$ ) ru/y films4 ,oxyg5 & wat] h "h unit$ ) ! iron1 =m+ hydrat$ iron oxide4 ,! effects ( oxidation may be se5 9 ! alt]ation ( _m k9ds ( rocks & 9 r$ & yell[ colors ( soils & subsoils4 ,pyrite is a v h>d m9]al ( a pale brass color1 f\nd 9 scatt]$ cry/als 9 _m rocks1 & is compos$ ( iron & sulphur 7iron sulphide74 ,"u ! attack ( ! wea!r x takes up oxyg51 =m+ iron sulphate 7gre5 vitriol71 a soluble comp\nd1 & insoluble hydrat$ iron oxide1 :i* z a m9]al is kn[n z limonite4 ,sev]al l>ge masses ( iron sulphide 7 plac$ "s ye>s ago on ! lawn 9 front ( ! ,national ,museum at ,wa%+ton4 ,! m9]al *ang$ s rapidly to gre5 vitriol t en\gh ( ?is poison\s comp\nd 0 wa%$ into ! gr\nd to kill ! roots ( ! surr\nd+ grass4 ,ag5ts ,( ,me*anical ,dis9tegration ,heat & cold4 ,rocks expos$ to ! direct rays ( ! sun become /rongly heat$ by day & exp&4 ,aft] sunset !y rapidly cool & contract4 ,:5 ! diff]5ce 9 temp]ature betwe5 day & night is consid]able1 ! repeat$ /ra9s ( sudd5 expansion & contraction at la/ become great] ?an ! rocks c be>1 & !y break1 = ! same reason t a glass cracks :5 plung$ into boil+ wat] 7,fig4 #e74 ,rocks are poor conductors ( heat1 & h5ce _! surfaces may become pa9fully hot "u ! full blaze ( ! sun1 :ile ! int]ior rema9s comp>atively cool4 ,by day ! surface %ell exp&s & t5ds to break loose f ! mass ( ! /one4 ,9 cool+ 9 ! ev5+ ! surface %ell sudd5ly contracts on ! unyield+ int]ior & 9 "t is =c$ (f 9 scales 7,fig4 #f74 ,illu/ration3 ,fig4 #f4 ,b[ld]s scal+ (f "u ,heat & ,cold1 ,we/]n ,texas ,_m rocks1 su* z granite1 are made up ( gra9s ( v>i\s m9]als :i* diff] 9 color & 9 _! capacity to absorb heat1 & :i* !re=e contract & exp& 9 diff]5t ratios4 ,9 heat+ & cool+ ^! gra9s cr[d aga9/ _! neighbors & te> loose f !m1 s t f9ally ! rock dis9tegrates into s&4 ,! conditions = ! de/ructive action ( heat & cold are mo/ fully met 9 arid regions :5 vegetation is want+ = lack ( suffici5t ra94 ,! soil n be+ held toge!r by ! roots ( plants is bl[n away ov] l>ge areas1 leav+ ! rocks b>e to ! blaz+ sun 9 a cl\dless sky4 ,! air is dry1 & ! heat receiv$ by ! e>? by day is !re=e rapidly radiat$ at night into space4 ,!re is a %>p & sudd5 fall ( temp]ature aft] sunset1 & ! rocks1 /rongly heat$ by day1 are n[ *ill$ p]haps ev5 to ! freez+ po9t4 ,9 ! ,sah>a ! !rmomet] has be5 kn[n to fall #aca ,f4 )9 a few h\rs4 ,9 ! light air ( ! ,pamir plateau 9 c5tral ,asia a rise ( #ij ,f4 has be5 record$ f sev5 o'clock 9 ! morn+ to "o o'clock 9 ! aft]noon4 ,on ! m\nta9s ( s\?we/]n ,texas !re are frequ5tly he>d crackl+ noises z ! rocks ( t arid region ?r[ (f scales f a fraction ( an in* to f\r in*es 9 ?ickness1 & l\d reports are made z huge b[ld]s split ap>t4 ,des]t pebbles weak5$ by long exposure to heat & cold h be5 %iv]$ to f9e %>p-po9t$ fragm5ts on be+ plac$ 9 s& heat$ to #ahj degrees ,f4 ,b$s half a foot ?ick1 =m+ ! floor ( lime/one qu>ries 9 ,wiscons91 h be5 kn[n to buckle & ar* & break to fragm5ts "u ! heat ( ! summ] sun4 ,fro/4 ,by ?is t]m is meant ! freez+ & ?aw+ ( wat] conta9$ 9 ! pores & crevices ( rocks4 ,all rocks are m or less por\s & all conta9 m or less wat] 9 _! pores4 ,work]s 9 /one call ?is qu>ry wat]1 & speak ( a /one z gre5 be=e ! qu>ry wat] has dri$ out4 ,wat] also seeps along jo9ts & b$d+ planes & ga!rs 9 all seams & crevices4 ,wat] exp&s 9 freez+1 t5 cubic in*es ( wat] freez+ to ab\t elev5 cubic in*es ( ice4 ,z wat] freezes 9 ! rifts & pores ( rocks x exp&s ) ! irresi/ible =ce illu/rat$ 9 ! freez+ & break+ ( wat] pipes 9 w9t]4 ,! fir/ rift 9 ! rock1 p]haps too n>r[ to be se51 is wid5$ little by little by ! w$ges ( successive fro/s1 & f9ally ! rock is brok5 into deta*$ blocks1 & ^! into angul> *ip-/one by ! same process4 ,x is on m\nta9 tops & 9 high latitudes t ! effects ( fro/ are mo/ pla9ly se54 ,e summit says ,:ymp]1 among/ ! rock summits ^u :i* ,i h /ood has be5 no?+ b a pil$-up heap ( fragm5ts 7,fig4 #g74 ,9 ,icel&1 9 ,spitzb]g51 9 ,kam*atka1 & 9 o!r frigid l&s l>ge areas are ?ickly /rewn ) %>p-edg$ fragm5ts into :i* ! rock has be5 %att]$ by fro/4 ,illu/ration3 ,fig4 #g4 ,rocks brok5 by ,fro/1 ,summit ( ! ,eggis*horn1 ,switz]l& ,organic ag5ts4 ,we mu/ reckon ! roots ( plants & trees among ! ag5ts :i* break rocks into pieces4 ,! t9y rootlet 9 its se>* = food & moi/ure ins]ts itself into "s m9ute rift1 & z x gr[s sl[ly w$ges ! rock ap>t4 ,moreov]1 ! acids ( ! root corrode ! rocks ) :i* !y are 9 contact4 ,"o may sometimes f9d 9 ! soil a block ( lime/one wrapp$ 9 a me% ( roots1 ea* ( :i* lies 9 a little furr[ :]e x has eat5 into ! /one4 ,rootless plants call$ li*5s (t5 cov] & corrode rocks z yet b>e ( soil2 b :]e li*5s are de/roy+ ! rock less rapidly ?an does ! wea!r1 !y s]ve 9 a way z a protection4 ,conditions favor+ dis9tegration & decay4 ,! dis9tegration ( rocks "u fro/ & temp]ature *anges goes on mo/ rapidly 9 cold & arid climates1 & :]e vegetation is scant or abs5t4 ,on ! contr>y1 ! decay ( rocks "u ! *emical action ( wat] is favor$ by a w>m1 moi/ climate & abundant vegetation4 ,fro/ & heat & cold c only act )9 ! few feet f ! surface to :i* ! necess>y temp]ature *anges are limit$1 :ile wat] p5etrates & alt]s ! rocks to great dep?s4 ,! pupil may expla94 ,9 :at ways ! pres5ce ( jo9ts & b$d+ planes assi/s 9 ! break+ up & decay ( rocks "u ! action ( ! wea!r4 ,:y x is a good rule ( /one masons nev] to lay /ones on edge1 b always on _! natural b$d+ planes4 ,:y /ones fre% f ! qu>ry sometimes g to pieces 9 e>ly w9t]1 :5 /ones :i* h be5 qu>ri$ = "s mon?s rema9 un9jur$4 ,:y qu>rym5 9 ! nor!rn /ates (t5 keep _! qu>ry floors flood$ dur+ w9t]4 ,:y lam9at$ lime/one %\ld n be us$ = curb/one4 ,:y rocks compos$ ( lay]s diff]+ 9 f95ess ( gra9 & 9 ratios ( expansion d n make good build+ /one4 ,f9e-gra9$ rocks ) pores s small t capill>y attraction keeps ! wat] :i* !y conta9 f readily dra9+ away are m apt to hold _! pores t5 elev5?s full ( wat] ?an are rocks ^: pores are l>g]4 ,:i*1 !re=e1 are m likely to be injur$ by fro/8 ,:i* is subject to great] temp]ature *anges1 a d>k rock or "o ( a light color8 ! nor? side or ! s\? side ( a valley8 ,! ,mantle ( ,rock ,wa/e ,we h se5 t rocks are ev]y:]e sl[ly wa/+ away4 ,!y are brok5 9 pieces by fro/1 by tree roots1 & by heat & cold4 ,!y dissolve & decompose "u ! *emical action ( wat] & ! v>i\s corrosive sub/ances :i* x conta9s1 leav+ _! insoluble residues z residual clays & s&s ^u ! surface4 ,z a result !re is ev]y:]e =m+ a mantle ( rock wa/e :i* cov]s ! l&4 ,x is well to imag9e h[ ! c\ntry w\ld appe> 7 ?is mantle ) its soil & vegetation all scrap$ away or _h x nev] be5 =m$4 ,! surface ( ! l& w\ld !n be ev]y:]e ( b>e rock z unbrok5 z a qu>ry floor4 ,! ?ickness ( ! mantle4 ,9 any locality ! ?ickness ( ! mantle ( rock wa/e dep5ds z mu* on ! rate at :i* x is con/antly be+ remov$ z on ! rate at :i* x is =m+4 ,on ! face ( cliffs x is abs5t1 = "h wa/e is remov$ z fa/ z x is made4 ,:]e wa/e is c>ri$ away m sl[ly ?an x is produc$1 x accumulates 9 "t to great dep?4 ,! granite ( ,pikes ,peak is dis9tegrat$ to a dep? ( tw5ty feet4 ,9 ! city ( ,wa%+ton granite rock is s s(t5$ to a dep? ( eighty feet t x c be remov$ ) pick & %ovel4 ,ab\t ,atlanta1 ,georgia1 ! rocks are completely rott$ = "o hundr$ feet f ! surface1 :ile ! beg9n+s ( decay may be notic$ at ?rice t dep?4 ,9 places 9 s\!rn ,brazil ! rock is decompos$ to a dep? ( f\r hundr$ feet4 ,9 s\?we/]n ,wiscons9 a r$di% residual clay has an av]age dep? ( ?irte5 feet on broad upl&s1 :]e x has be5 remov$ to ! lea/ ext5t4 ,! c\ntry rock on :i* x re/s is a lime/one ) ab\t t5 p] c5t ( insoluble impurities4 ,at lea/ h[ ?ick1 !n1 0 t portion ( ! lime/one :i* has rott$ d[n to ! clay8 ,di/+ui%+ *>act]i/ics ( residual wa/e4 ,we mu/ le>n to di/+ui% wa/e =m$ 9 place by ! action ( ! wea!r f ! products ( o!r geological ag5cies4 ,residual wa/e is un/ratifi$4 ,x conta9s no sub/ances :i* h n be5 d]iv$ f ! wea!r+ ( ! p>5t rock4 ,!re is a gradual transition f residual wa/e into ! unwea!r$ rock b5ea?4 ,wa/e re/+ on s\nd rock evid5tly has be5 %ift$ & 0 n =m$ 9 place4 ,9 c]ta9 regions ( s\!rn ,miss\ri ! l& is cov]$ ) a lay] ( brok5 fl9ts & r$ clay1 :ile ! c\ntry rock is lime/one4 ,! lime/one conta9s nodules ( fl9t1 & we may inf] t x has be5 by ! decay & removal ( ?ick masses ( lime/one t ! residual lay] ( clay & fl9ts has be5 left ^u ! surface4 ,fl9t is a =m ( qu>tz1 dull-lu/]$1 usually gray or blacki% 9 color1 & opaque except on ?9ne/ edges1 :]e x is transluc5t4 ,ov] mu* ( ! nor!rn /ates !re is spread an un/ratifi$ /ony clay call$ ! drift4 ,x (t5 re/s on s\nd rocks4 ,x conta9s gra9s ( s&1 pebbles1 & b[ld]s compos$ ( _m diff]5t m9]als & rocks t ! c\ntry rock _c furni%4 ,h5ce ! drift _c h be5 =m$ by ! decay ( ! rock ( ! region4 ,a %ale or lime/one1 = example1 _c wa/e to a clay conta9+ granite pebbles4 ,! orig9 ( ! drift w be expla9$ 9 subsequ5t *apt]s4 ,! diff]5ces 9 rocks are due m to _! soluble ?an to _! insoluble con/itu5ts4 ,! latt] are few 9 numb] & are mu* ! same 9 rocks ( widely diff]5t nature1 be+ *iefly qu>tz1 silicate ( alum9a1 & iron oxide4 ,by ! removal ( _! soluble p>ts v _m & widely diff]5t rocks rot d[n to a residual clay gritty ) p>ticles ( qu>tz & color$ r$ or yell[ ) iron oxide4 ,9 a broad way ! *anges :i* rocks und]go 9 wea!r+ are an adaptation to ! environm5t 9 :i* !y f9d !mselves at ! e>?'s surface1--an environm5t diff]5t f t 9 :i* !y 7 =m$ "u sea or "u gr\nd4 ,9 op5 air1 :]e !y are attack$ by v>i\s de/ructive ag5ts1 few ( ! rock-mak+ m9]als are /able comp\nds except qu>tz1 ! iron oxides1 & ! silicate ( alum9a2 & s x is to "o or m ( ^! comp>atively insoluble sub/ances t mo/ rocks are r$uc$ by long decay4 ,:i* produces a mantle ( f9] wa/e1 fro/ or *emical decay8 :i* a ?ick] mantle8 ,9 :at respects w\ld y expect t ! mantle ( wa/e w\ld diff] 9 w>m humid l&s l ,india1 9 froz5 c\ntries l ,alaska1 & 9 des]ts su* z ! ,sah>a8 ,! soil4 ,! same ag5cies :i* produce ! mantle ( wa/e are cont9ually at "w ^u x1 break+ x up into f9] & f9] p>ticles & caus+ its m complete decay4 ,?us on ! surface1 :]e ! wa/e has wea!r$ longe/1 x is gradually made f9e en\gh to support ! gr[? ( plants1 & is !n kn[n z soil4 ,! co>s] wa/e b5ea? is sometimes spok5 ( z subsoil4 ,soil usually conta9s m or less d>k1 c>bonace\s1 decay+ organic matt]1 call$ humus1 & is !n (t5 t]m$ ! humus lay]4 ,soil =ms n only on wa/e produc$ 9 place f ! rock b5ea?1 b also on mat]ials :i* h be5 transport$1 su* z %eets ( glacial drift & riv] deposits4 ,until rocks are r$uc$ to residual clays ! "w ( ! wea!r is m rapid & effective on ! fragm5ts ( ! mantle ( wa/e ?an on ! rocks f :i* wa/e is be+ =m$4 ,:y8 ,any fre% excavation ( cell> or ci/]n1 or cut = road or railway1 w %[ ! *>act]i/ics ( ! humus lay]4 ,x may =m only a gray film on ! surface1 or we may f9d x a lay] a foot or m ?ick1 d>k1 or ev5 black1 above1 & gr[+ gradually light] 9 color z x passes by ins5sible gradations into ! subsoil4 ,9 "s way ! decay+ vegetable matt] cont9ually =m+ on ! surface has become m+l$ ) ! mat]ial b5ea? x4 ,h[ humus & ! subsoil are m+l$4 ,! m+l+ ( humus & ! subsoil is br\ght ab\t by sev]al means4 ,! roots ( plants p5etrate ! wa/e1 & :5 !y die leave _! decay+ sub/ance to f]tilize x4 ,leaves & /ems fall+ on ! surface are turn$ "u by sev]al ag5ts4 ,e>?worms & o!r animals ^: home is 9 ! wa/e drag !m into _! burr[s ei!r = food or to l9e _! ne/s4 ,trees ov]?r[n by ! w9d1 roots & all1 turn ov] ! soil & subsoil & m+le !m toge!r4 ,bact]ia also "w 9 ! wa/e & contribute to its enri*m5t4 ,! animals liv+ 9 ! mantle d mu* 9 o!r ways t[>d ! mak+ ( soil4 ,!y br+ ! co>s] fragm5ts f b5ea? to ! surface1 :]e ! wa/e wea!rs m rapidly4 ,_! burr[s all[ air & wat] to p5etrate ! wa/e m freely & to affect x to great] dep?s4 ,ants4 ,9 ! tropics ! mantle ( wa/e is work$ ov] *iefly by ants4 ,!y excavate und]gr\nd gall]ies & *amb]s1 ext5d+ sometimes z mu* z f\rte5 feet bel[ ! surface1 & build m\nds :i* may rea* z high above x4 ,9 "s p>ts ( ,p>aguay & s\!rn ,brazil ^! m\nds1 l gigantic potato hills1 cov] tracts ( consid]able area4 ,9 se>* = its food--! dead wood ( trees--! s-call$ :ite ant con/ructs runways ( e>? ab\t ! size ( gas pipes1 rea*+ f ! base ( ! tree to ! topmo/ bran*es4 ,on ! plateaus ( c5tral ,africa explor]s h walk$ = miles ?r\gh =e/s e tree ( :i* 0 pla/]$ ) ^! gall]ies ( mud4 ,ea* gra9 ( e>? us$ 9 _! con/ruction is moi/5$ & cem5t$ by slime z x is laid 9 place by ! ant1 & is ?us act$ on by organic *emical ag5ts4 ,soon] or lat] ^! gall]ies are beat5 d[n by heavy ra9s1 & _! f]tiliz+ sub/ances are scatt]$ widely by ! w9ds4 ,e>?worms4 ,9 temp]ate regions ! wa/e is work$ ov] l>gely by e>?worms4 ,9 mak+ _! burr[s worms swall[ e>? 9 ord] to extract f x any nutritive organic matt] :i* x may conta94 ,!y treat x ) _! dige/ive acids1 gr9d x 9 _! /ony gizz>ds1 & void x 9 ca/+s on ! surface ( ! gr\nd4 ,x 0 e/imat$ by ,d>w9 t 9 _m p>ts ( ,engl& ea* ye>1 on e acre1 m ?an t5 tons ( e>? pass ?r\gh ! bodies ( e>?worms & are br\ght to ! surface1 & t e few ye>s ! entire soil lay] is ?us work$ ov] by !m4 ,9 all ^! ways ! wa/e is made f9e & /irr$ & enri*$4 ,gra9 by gra9 ! subsoil ) its fre% m9]al +r$i5ts is br\ght to ! surface1 & ! ri* organic matt] :i* plants & animals h tak5 f ! atmosph]e is pl[$ "u4 ,?us ,nature pl[s & h>r[s on ! great _w's f>m to make ready & ev] to r5ew a soil fit = ! endless succession ( h] crops4 ,! _w processes by :i* rocks are cont9ually wa/+ away are ?us indisp5sable to ! life ( plants & animals4 ,! organic _w is built on ! ru9s ( ! inorganic1 & because ! solid rocks h be5 brok5 d[n into soil m5 are able to live ^u ! e>?4 ,sol> en]gy4 ,! s\rce ( ! en]gy :i* accompli%es all ?is necess>y "w is ! sun4 ,x is ! radiant en]gy ( ! sun :i* causes ! dis9tegration ( rocks1 :i* lifts vapor into ! atmosph]e to fall z ra91 :i* gives life to plants & animals4 ,consid]+ ! e>? 9 a broad way1 we may view x z a globe ( solid rock1--! li?osph]e1--surr\nd$ by two mobile envelopes3 ! envelope ( air1--! atmosph]e2 & ! envelope ( wat]1--! hydrosph]e4 ,"u ! action ( sol> en]gy ^! envelopes are 9 con/ant motion4 ,wat] f ! hydrosph]e is cont9ually ris+ 9 vapor into ! atmosph]e1 ! air ( ! atmosph]e p5etrates ! hydrosph]e1--= its gases are dissolv$ 9 all wat]s1--& bo? air & wat] ent] & "w ^u ! solid e>?4 ,by _! action ^u ! li?osph]e !y h produc$ a ?ird envelope1--! mantle ( rock wa/e4 ,?is envelope also is 9 movem5t1 n inde$ z a :ole1 b p>ticle by p>ticle4 ,! causes :i* set its p>ticles 9 motion1 & ! diff]5t =ms :i* ! mantle comes to assume1 we w n[ proce$ to /udy4 ,movem5ts ( ! ,mantle ( ,rock ,wa/e ,at ! s&/one l$ges :i* we fir/ visit$ we saw n only t ! rocks 7 crumbl+ away1 b also t gra9s & fragm5ts ( !m 7 creep+ d[n ! slopes ( ! valley to ! /ream & 7 c>ri$ by x onw>d t[>d ! sea4 ,?is process is go+ on ev]y:]e4 ,sl[ly x may be1 & ) _m int]ruptions1 b surely1 ! wa/e ( ! l& moves d[nw>d to ! sea4 ,we may divide its c\rse into two p>ts1--! pa? to ! /ream1 :i* we w n[ consid]1 & its c>riage onw>d by ! /ream1 :i* we w def] to a lat] *apt]4 ,gravity4 ,! *ief ag5t conc]n$ 9 ! movem5t ( wa/e is gravity4 ,ea* p>ticle ( wa/e feels ! unceas+ d[nw>d pull ( ! e>?'s mass & foll[s x :5 free to d s4 ,all ag5cies :i* produce wa/e t5d to set its p>ticles free & 9 motion1 & !re=e cop]ate ) gravity4 ,on cliffs1 rocks fall :5 w$g$ (f by fro/ or by roots ( trees1 & :5 deta*$ by any o!r ag5cy4 ,on slopes ( wa/e1 wat] freezes 9 *9ks betwe5 /ones1 & 9 pores betwe5 p>ticles ( soil1 & w$ges !m ap>t4 ,animals & plants /ir ! wa/e1 heat exp&s x1 cold contracts x1 ! /rokes ( ! ra9drops drive loose p>ticles d[n ! slope & ! w9d lifts & lets !m fall4 ,( all ^! movem5ts1 gravity assi/s ^? :i* are d[nhill & ret>ds ^? :i* are uphill4 ,on ! :ole1 !re=e1 ! d[nhill movem5ts prevail1 & ! mantle ( wa/e1 block by block & gra9 by gra91 creeps along ! d[nhill pa?4 ,a slab ( s&/one laid on ano!r ( ! same k9d at an angle ( #ag & left 9 ! op5 air 0 f\nd to creep d[n ! slope at ! rate ( a little m ?an a millimet] a mon?4 ,expla9 :y x did s4 ,ra94 ,! mo/ effici5t ag5t 9 ! c>riage ( wa/e to ! /reams is ! ra94 ,x moves p>ticles ( soil by ! =ce ( ! bl[s ( ! fall+ drops1 & wa%es !m d[n all slopes to )9 rea* ( p]man5t /reams4 ,on surfaces unprotect$ by vegetation1 z on pl[$ fields & 9 arid regions1 ! ra9 we>s furr[s & gullies bo? 9 ! mantle ( wa/e & 9 exposures ( unalt]$ rock 7,fig4 #ag74 ,at ! foot ( a hill we may f9d t ! soil has accumulat$ by creep & wa% to ! dep? ( sev]al feet2 :ile :]e ! hillside is /eepe/ ! soil may be exce$+ly ?91 or q abs5t1 because remov$ ab\t z fa/ z =m$4 ,aga9/ ! walls ( an abbey built on a slope 9 ,wales sev5 hundr$ ye>s ago1 ! creep+ wa/e has ga!r$ on ! uphill side to a dep? ( sev5 feet4 ,! sl[-fl[+ %eet ( wa/e is (t5 damm$ by f5ces & walls1 ^: uphill side ga!rs wa/e 9 a few ye>s s z to %[ a di/9ctly high] surface ?an ! d[nhill side1 especially 9 pl[$ fields :]e ! movem5t is lea/ *eck$ by vegetation4 ,talus4 ,at ! foot ( cliffs !re is usually to be f\nd a slope ( rock fragm5ts :i* cle>ly h fall5 f above 7,fig4 #h74 ,su* a heap ( wa/e is kn[n z talus4 ,! am\nt ( talus 9 any place dep5ds bo? on ! rate ( its =mation & ! rate ( its removal4 ,talus =ms rapidly 9 climates :]e me*anical dis9tegration is mo/ effective1 :]e rocks are readily brok5 into blocks because closely jo9t$ & ?9ly b$d$ r ?an massive1 & :]e !y are firm en\gh to be deta*$ 9 fragm5ts ( "s size in/ead ( 9 f9e gra9s4 ,talus is remov$ sl[ly :]e x decays sl[ly1 ei!r because ( ! climate or ! resi/ance ( ! rock4 ,x may be rapidly remov$ by a /ream fl[+ along its base4 ,illu/ration3 ,fig4 #h4 ,talus at ,foot ( ,granite ,cliffs1 ,si]ra ,nevada ,m\nta9s ,9 a moi/ climate a soluble rock1 su* z massive lime/one1 may =m talus little if any fa/] ?an ! talus wea!rs away4 ,a loose-textur$ s&/one breaks d[n into incoh]5t s& gra9s1 :i* 9 dry climates1 :]e unprotect$ by vegetation1 may be bl[n away z fa/ z !y fall1 leav+ ! cliff b>e to ! base4 ,cliffs ( su* sl[-decay+ rocks z qu>tzite & granite :5 closely jo9t$ accumulate talus 9 l>ge am\nts4 ,illu/ration3 ,fig4 #i4 ,diagram ,illu/rat+ ,retreat ( ,cliff1 c1 & ,talus1 t ,talus slopes may be s /eep z to rea* ! angle ( repose1 i4e4 ! /eepe/ angle at :i* ! mat]ial w lie4 ,?is angle v>ies ) diff]5t mat]ials1 be+ great] ) co>se & angul> fragm5ts ?an ) f9e r\nd$ gra9s4 ,soon] or lat] a talus rea*es t equilibrium :]e ! am\nt remov$ f its surface j equals t suppli$ f ! cliff above4 ,z ! talus is remov$ & wea!rs away its slope retreats toge!r ) ! retreat ( ! cliff1 z se5 9 ,figure #i4 ,grad$ slopes4 ,:]e rocks wea!r fa/] ?an _! wa/e is c>ri$ away1 ! wa/e comes at la/ to cov] all rocky l$ges4 ,on ! /eep] slopes x is co>s] & 9 m rapid movem5t ?an on slopes m g5tle1 b m\nta9 sides & hills & pla9s alike come to be mantl$ ) %eets ( wa/e :i* ev]y:]e is creep+ t[>d ! /reams4 ,su* unbrok5 slopes1 worn or built to ! lea/ incl9ation at :i* ! wa/e suppli$ by wea!r+ c be urg$ onw>d1 are kn[n z grad$ slopes4 ,( f> less importance ?an ! sil5t1 gradual creep ( wa/e1 :i* is go+ on at all times ev]y:]e ab\t u1 are ! />tl+ local & spasmodic movem5ts :i* we are n[ to describe4 ,avalan*es4 ,on /eep m\nta9 sides ! accumulat$ sn[s ( w9t] (t5 slip & slide 9 avalan*es to ! valleys bel[4 ,^! ru%+ torr5ts ( sn[ sweep _! tracks clean ( wa/e & are "o ( ,nature's normal me?ods ( mov+ x along ! d[nhill pa?4 ,illu/ration3 ,fig4 #aj4 ,a ,l&slide1 ,quebec ,l&slides4 ,ano!r common & abrupt me?od ( deliv]+ wa/e to /reams is by slips ( ! wa/e mantle 9 l>ge masses4 ,aft] long ra9s & aft] w9t] fro/s ! cohesion betwe5 ! wa/e & ! s\nd rock b5ea? is loos5$ by seep+ wat] und]gr\nd4 ,! wa/e slips on ! rock surface ?us lubricat$ & plunges d[n ! m\nta9 side 9 a swift ro>+ torr5t ( mud & /ones4 ,illu/ration3 ,fig4 #aa4 ,diagram ,illu/rat+ ,conditions favorable to a ,l&slide lm1 lime/one dipp+ t[>d valley ( riv]1 r2 %1 %ale ,we may conv5i5tly m5tion "h a second type ( l&slide1 :]e masses ( solid rock z well z ! mantle ( wa/e are involv$ 9 ! sudd5 movem5t4 ,su* slips occur :5 valleys h be5 rapidly deep5$ by /reams or glaci]s & _! sides h n yet be5 grad$4 ,a favorable condition is :]e ! /rata dip 7i4e4 incl9e d[nw>ds7 t[>ds ! valley 7,fig4 #aa71 or are brok5 by jo9t planes dipp+ 9 ! same direction4 ,! upp] lay]s1 includ+ p]haps ! entire m\nta9 side1 h be5 cut across by ! valley tr5* & are left support$ only on ! incl9$ surface ( ! und]ly+ rocks4 ,wat] may p]colate und]gr\nd along ?is surface & loos5 ! cohesion betwe5 ! upp] & ! und]ly+ /rata by conv]t+ ! upp] surface ( a %ale to s(t wet clay1 by dissolv+ lay]s ( a lime/one1 or by remov+ ! cem5t ( a s&/one & conv]t+ x into loose s&4 ,:5 ! incl9$ surface is ?us lubricat$ ! ov]ly+ masses may be laun*$ into ! valley bel[4 ,! solid rocks are brok5 & cru%$ 9 slid+ & conv]t$ into wa/e consi/+1 l t ( talus1 ( angul> unsort$ fragm5ts1 blocks ( all sizes be+ m+l$ pell-mell ) rock meal & du/4 ,! pr9cipal effects ( l&slides may be ga!r$ f ! foll[+ examples4 ,at ,gohna1 ,india1 9 #ahic1 ! face ( a spur f\r ?\s& feet high1 ( ! l[] ranges ( ! ,himalayas1 slipp$ into ! gorge ( ! headwat]s ( ! ,ganges ,riv] 9 successive rock falls :i* la/$ = ?ree days4 ,blocks ( /one 7 project$ = a mile1 & cl\ds ( lime/one du/ 7 spread ov] ! surr\nd+ c\ntry4 ,! dbris =m$ a dam "o ?\s& feet high1 ext5d+ = two miles along ! valley4 ,a lake ga!r$ beh9d ?is b>ri]1 gradually ris+ until x ov]topp$ x 9 a little less ?an a ye>4 ,! upp] portion ( ! dam !n broke1 & a t]rific ru% ( wat] swept d[n ! valley 9 a wave :i*1 tw5ty miles away1 rose "o hundr$ & sixty feet 9 height4 ,a n>r[ lake is /ill held by ! /rong base ( ! dam4 ,9 #ahif1 aft] =ty days ( incessant ra91 a cliff ( s&/one slipp$ into ! ,yangtse ,riv] 9 ,*9a1 r$uc+ ! wid? ( ! *annel to eighty y>ds & caus+ =midable rapids4 ,illu/ration3 ,fig4 #ab4 ,b[ld]s ( ,wea!r+1 ,granite ,qu>ry1 ,cape ,ann1 ,massa*usetts ,at ,flims1 9 ,switz]l&1 a prehi/oric l&slip flung a dam eighte5 hundr$ feet high across ! headwat]s ( ! ,rh9e4 ,if spread ev5ly ov] a surface ( tw5ty-eight squ>e miles1 ! mat]ial w\ld cov] x to a dep? ( six hundr$ & sixty feet4 ,! b>ri] is n yet entirely cut away1 & sev]al lakes are held 9 %all[ bas9s on its hummocky surface4 ,a slide f ! precipit\s riv] front ( ! citadel hill ( ,quebec1 9 #ahhi1 da%$ across ,*ampla9 ,/reet1 wreck+ a numb] ( h\ses & caus+ ! dea? ( =ty-five p]sons4 ,! /rata "h are compos$ ( /eeply dipp+ slate 7,fig4 #aj74 ,9 l(ty m\nta9 ranges !re may n be a s+le valley )\t its traces ( l&slides1 s common !re is ?is me?od ( ! movem5t ( wa/e1 & ( build+ to grade ov]-/eep5$ slopes4 ,rock ,sculpture ,by ,wea!r+ ,we are n[ to consid] a few ( ! =ms into :i* rock masses are c>v$ by ! wea!r4 ,illu/ration3 ,fig4 #ac4 ,diff]5tial ,wea!r+ on a ,monum5t1 ,colorado ,b[ld]s ( wea!r+4 ,9 _m qu>ries & outcrops we may see t ! blocks into :i* "o or m ( ! upp]mo/ lay]s h be5 brok5 along _! jo9ts & b$d+ planes are no long] angul>1 z are ^? ( ! lay]s bel[4 ,! edges & corn]s ( ^! blocks h be5 worn away by ! wea!r4 ,su* r\nd$ cores1 kn[n z b[ld]s ( wea!r+1 are (t5 left to /rew ! surface4 ,diff]5tial wea!r+4 ,?is t]m cov]s all cases 9 :i* a rock mass wea!rs diff]5tly 9 diff]5t portions4 ,any weak] spots or lay]s are et*$ out on ! surface1 leav+ ! m resi/ant 9 relief4 ,?us massive lime/ones become pitt$ :]e ! wea!r drills out ! weak] portions4 ,9 ^! pits1 :5 once !y are =m$1 moi/ure ga!rs1 a little soil collects1 vegetation takes root1 & ?us !y are fur!r enl>g$ until ! lime/one may be deeply honeycomb$4 ,illu/ration3 ,fig4 #ad4 ,honeycomb$ ,lime/one1 ,i[a ,illu/ration3 ,fig4 #ae4 ,cliffs & ,slopes on ,nor? ,wall ( ! ,gr& ,canyon ( ! ,colorado ,riv]1 ,arizona ,on ! sides ( canyons1 & else:]e :]e ! edges ( /rata are expos$1 ! h>d] lay]s project z cliffs1 :ile ! s(t] wea!r back to slopes cov]$ ) ! talus ( ! h>d] lay]s above !m4 ,x is conv5i5t to call ! =m] cliff mak]s & ! latt] slope mak]s 7,fig4 #ae74 ,diff]5tial wea!r+ plays a l>ge "p 9 ! sculpture ( ! l&4 ,areas ( weak rock are wa/$ to pla9s1 :ile areas ( h>d rock adjac5t are /ill left z hills & m\nta9 ridges1 z 9 ! valleys & m\nta9s ( ea/]n ,p5nsylvania4 ,b 9 su* in/ances ! l[]+ ( ! surface ( ! weak] rock is also due to ! we> ( /reams1 & especially to ! removal by !m f ! l& ( ! wa/e :i* cov]s & protects ! rocks b5ea?4 ,illu/ration3 ,fig4 #af4 ,tav]lone ,mesa1 ,new ,mexico ,rocks owe _! weakness to sev]al diff]5t causes4 ,"s1 su* z b$s ( loose s&1 are s(t & easily worn by ra9s2 "s1 z lime/one & gypsum = example1 are soluble4 ,ev5 h>d insoluble rocks are weak "u ! attack ( ! wea!r :5 !y are closely divid$ by jo9ts & b$d+ planes & are ?us readily brok5 up into blocks by me*anical ag5cies4 ,illu/ration3 ,fig4 #ag4 ,monum5ts1 ,arizona ,note ! ra9 furr[s on ! slope at ! foot ( ! monum5ts4 ,9 ! =egr\nd are se5 fragm5ts ( petrifi$ trunks ( trees1 compos$ ( silica & extremely resi/ant to ! wea!r4 ,on ! removal ( ! rock lay]s 9 :i* ^! fragm5ts 7 imb$d$ !y are left to /rew ! surface 9 ! same way z are ! residual fl9ts ( s\!rn ,miss\ri4 ,outli]s & monum5ts4 ,z cliffs retreat "u ! attack ( ! wea!r1 portions are left beh9d :]e ! rock is m resi/ant or :]e ! attack = any reason is less sev]e4 ,su* remnant masses1 if l>ge1 are kn[n z outli]s4 ,:5 flat-topp$1 because ( ! protection ( a resi/ant horizontal capp+ lay]1 !y are t]m$ mesas 7,fig4 #af71--;a t]m appli$ also to ! flat-topp$ portions ( dissect$ plateaus 7,fig4 #abi74 ,retreat+ cliffs may fall back a numb] ( miles beh9d _! outli]s be=e ! latt] are f9ally consum$4 ,illu/ration3 ,fig4 #ah4 ,und]cut ,monum5ts1 ,colorado ,monum5ts are small] masses & may be b p>tially deta*$ f ! cliff face4 ,9 ! break+ d[n ( %eets ( horizontal /rata1 outli]s gr[ small] & small] & are r$uc$ to massive rectangul> monum5ts resembl+ ca/les 7,fig4 #ag74 ,! rock ca/le falls into ru91 leav+ "h & !re an isolat$ t[]2 ! t[] crumbles to a lonely pill>1 soon to be ov]?r[n4 ,! v>i\s & (t5 picturesque %apes ( monum5ts dep5d on ! k9d ( rock1 ! attitude ( ! /rata1 & ! ag5t by :i* !y are *iefly c>v$4 ,?us pill>s may h a capital =m$ ( a resi/ant /ratum4 ,monum5ts may be und]cut & come to re/ on n>r[ p$e/als1 :]ev] !y wea!r m rapidly ne> ! gr\nd1 ei!r because ( ! great] moi/ure !re1 or--9 arid climates--because worn at _! base by drift+ s&s4 ,/ony clays dis9tegrat+ "u ! ra9 (t5 conta9 b[ld]s :i* protect ! s(t] mat]ial b5ea? f ! v]tical bl[s ( ra9drops1 & ?us come to /& on p$e/als ( "s height 7,fig4 #ai74 ,"o may sometimes see on ! gr\nd b5ea? dripp+ eaves pebbles left 9 ! same way1 protect+ t9y p$e/als ( s&4 ,m\nta9 peaks & ridges4 ,mo/ m\nta9s h be5 c>v$ out ( great broadly uplift$ folds & blocks ( ! e>?'s cru/4 ,runn+ wat] & glaci] ice h cut ^! folds & blocks into masses divid$ by deep valleys2 b x is by ! wea!r1 = ! mo/ "p1 t ! masses ?us sep>at$ h be5 sculptur$ to ! pres5t =ms ( ! individual peaks & ridges4 ,illu/ration3 ,fig4 #ai4 ,roosevelt ,column1 ,idaho ,an erosion pill> #gj feet high4 ,h[ 0 x produc$8 ,:y quadrangul>8 ,:at does x %[ z to ! rec5t height ( ! hillside surface8 ,fro/ & heat & cold sculpture high m\nta9s to %>p1 tusklike peaks & ragg$1 s]rate cre/s1 :]e _! wa/e is readily remov$ 7,fig4 #h74 ,! ,matt]horn ( ! ,alps is a fam\s example ( a m\nta9 peak ^: c>v+ by ! fro/ & o!r ag5ts is 9 active progress4 ,on its face sc>cely a rock any:]e is firmly atta*$1 & ! fall ( loos5$ /ones is incessant4 ,m\nta9 climb]s :o h camp$ at its base tell h[ huge rocks f "t to "t come leap+ d[n its precipices1 foll[$ by tra9s ( dislodg$ small] fragm5ts & rock du/2 & h[ at night "o may trace ! c\rse ( ! b[ld]s by ! sp>ks :i* !y /rike f ! m\nta9 walls4 ,m\nt ,ass9ibo9e1 ,canada 7,fig4 #bj71 resembles ! ,matt]horn 9 =m & has be5 c>v$ by ! same ag5cies4 ,! ,ne$les ( ,arizona are examples ( %>p m\nta9 peaks 9 a w>m arid region sculptur$ *iefly by temp]ature *anges4 ,*emical decay1 especially :5 c>ri$ on b5ea? a cov] ( wa/e & vegetation1 favors ! production ( r\nd$ knobs & dome-%ap$ m\nta9s4 ,! wea!r curve4 ,we h se5 t wea!r+ r$uces ! angul> block qu>ri$ by ! fro/ to a r\nd$ b[ld] by *ipp+ (f its corn]s & smoo?+ away its edges4 ,9 mu* ! same way wea!r+ at la/ r$uces to r\nd$ hills ! e>? blocks cut by /reams or =m$ 9 any o!r way4 ,high m\nta9s may at fir/ be sculptur$ by ! wea!r to savage peaks 7,fig4 #aha71 b t[>d ! end ( _! life hi/ory !y we> d[n to r\nd$ hills 7,fig4 #ahb74 ,! wea!r curve1 :i* may be se5 on ! summits ( l[ hills 7,fig4 #ba71 is convex upw>d4 ,illu/ration3 ,fig4 #bj4 ,m\nt ,ass9ibo9e1 ,canada ,illu/ration3 ,fig4 #ba4 ,big ,r\nd ,top & ,little ,r\nd ,top1 ,gettysburg1 ,p5nsylvania ,9 ,figure #bb1 repres5t+ a cubic block ( /one ^: faces are a y>d squ>e1 h[ _m squ>e feet ( surface are expos$ to ! wea!r by a cubic foot at a corn] a2 by "o situat$ 9 ! middle ( an edge b2 by "o 9 ! c5t] ( a side c8 ,h[ mu* fa/] w a & b wea!r ?an c1 & :at w be ! effect on ! %ape ( ! block8 ,illu/ration3 ,fig4 #bb ,! cop]ation ( v>i\s ag5cies 9 rock sculpture4 ,= ! sake ( cle>ness x is necess>y to describe ! "w ( ea* geological ag5t sep>ately4 ,we mu/ n =get1 h[ev]1 t 9 ,nature no ag5t works indep5d5tly & alone2 t e result is ! outcome ( a long *a9 ( causes4 ,?us1 9 ord] t ! m\nta9 peak may be c>v$ by ! ag5ts ( dis9tegration1 ! wa/e mu/ be rapidly remov$1--a "w done by _m ag5ts1 includ+ "s :i* we are yet to /udy2 & 9 ord] t ! wa/e may be remov$ z fa/ z =m$1 ! region mu/ fir/ h be5 rais$ well above ! level ( ! sea1 s t ! ag5ts ( transportation c\ld d _! "w effectively4 ,! sculpture ( ! rocks is accompli%$ only by ! cop]ation ( _m =ces4 ,! con/ant removal ( wa/e f ! surface by creep & wa% & c>riage by /reams is ( ! highe/ importance1 because x all[s ! de/ruction ( ! l& by means ( wea!r+ to g on z long z any l& rema9s above sea level4 ,if wa/e 7 n remov$1 x w\ld gr[ to be s ?ick z to protect ! rock b5ea? f fur!r wea!r+1 & ! processes ( de/ruction :i* we h /udi$ w\ld be br\ght to an end4 ,! v pres5ce ( ! mantle ( wa/e ov] ! l& proves t on ! :ole rocks wea!r m rapidly ?an _! wa/e is remov$4 ,! de/ruction ( ! l& is go+ on z fa/ z ! wa/e c be c>ri$ away4 ,we h n[ le>n$ to see 9 ! mantle ( wa/e ! record ( ! de/ructive action ( ! ag5cies ( wea!r+ on ! rocks ( ! l& surface4 ,simil> records we %all f9d buri$ deeply among ! rocks ( ! cru/ 9 old soils & 9 rocks pitt$ & decay$1 tell+ ( old l& surfaces long wa/$ by ! wea!r4 ,ev] s9ce ! dry l& appe>$ ^! ag5cies h be5 z n[ quietly & unceas+ly at "w ^u x1 & h ev] be5 ! *ief means ( ! de/ruction ( its rocks4 ,! va/ bulk ( ! /ratifi$ rocks ( ! e>?'s cru/ is made up almo/ :olly ( ! wa/e ?us worn f anci5t l&s4 ,illu/ration3 ,fig4 #bc4 ,m\nt ,sneffels1 ,colorado ,describe & acc\nt = :at y see 9 ?is view4 ,:at *anges may ! m\nta9 be expect$ to und]go 9 ! future f ! ag5cies n[ at "w ^u x8 ,9 /udy+ ! v>i\s geological ag5cies we mu/ rememb] ! almo/ inconceivable times 9 :i* !y "w4 ,! sl[e/ process :5 multipli$ by ! imm5se "t 9 :i* x is c>ri$ on produces great results4 ,! geologi/ looks ^u ! l& =ms ( ! e>?'s surface z monum5ts :i* record ! sl[ action ( wea!r+ & o!r ag5ts dur+ ! ages ( ! pa/4 ,! m\nta9 peak1 ! r\nd$ hill1 ! wide pla9 :i* lies :]e hills & m\nta9s once /ood1 tell cle>ly ( ! great results :i* sl[ processes w rea* :5 giv5 long "t 9 :i* to d _! "w4 ,we %\ld accu/om ourselves also to ?9k ( ! results :i* wea!r+ w soon] or lat] br+ to pass4 ,! tomb/one & ! b[ld] ( ! field1 :i* ea* ye> lose f _! surfaces a few cry/all9e gra9s1 mu/ 9 "t be :olly de/roy$4 ,! hill ^: rocks are sl[ly rott+ und]nea? a cov] ( wa/e mu/ become l[] & l[] z ! c5turies & mill5niums come & g1 & w f9ally disappe>4 ,ev5 ! m\nta9s are crumbl+ away cont9ually1 & !re=e are b fleet+ features ( ! l&scape4 ,,*apt] ,,ii ,,! ,,"w ,,( ,,gr\nd ,,wat] ,l& wat]s4 ,we h se5 h[ l>ge is ! "p t wat] plays at & ne> ! surface ( ! l& 9 ! processes ( wea!r+ & 9 ! sl[ movem5t ( wa/e d[n all slopes to ! /ream ways4 ,we n[ take up ! "w ( wat] z x desc5ds b5ea? ! gr\nd1--a corrosive ag5t /ill1 & c>ry+ 9 solution z its load ! invisible wa/e ( rocks d]iv$ f _! soluble p>ts4 ,l& wat]s h _! imm$iate s\rce 9 ! ra9fall4 ,by ! heat ( ! sun wat] is evaporat$ f ! res]voir ( ! ocean & f moi/ surfaces ev]y:]e4 ,m+l$ z vapor ) ! air1 x is c>ri$ by ! w9ds ov] sea & l&1 & cond5s$ x returns to ! e>? z ra9 or sn[4 ,t "p ( ! ra9fall :i* desc5ds on ! ocean does n conc]n u1 b t :i* falls on ! l& accompli%es1 z x returns to ! sea1 ! mo/ important "w ( all surface geological ag5cies4 ,! ra9fall may be divid$ into ?ree p>ts3 ! fir/ dries up1 be+ dis*>g$ into ! air by evaporation ei!r directly f ! soil or ?r\gh vegetation2 ! second runs (f ov] ! surface to flood ! /reams2 ! ?ird soaks 9 ! gr\nd & is h5ce=? kn[n z gr\nd or und]gr\nd wat]4 ,! desc5t ( gr\nd wat]4 ,seep+ ?r\gh ! mantle ( wa/e1 gr\nd wat] soaks into ! pores & crevices ( ! und]ly+ rock4 ,all rocks ( ! upp] cru/ ( ! e>? are m or less por\s1 & all dr9k 9 wat]4 ,imp]vi\s rocks1 su* z granite1 clay1 & %ale1 h pores s m9ute t ! wat] :i* !y take 9 is held fa/ )9 !m by capill>y attraction1 & none dra9s ?r\gh4 ,p]vi\s rocks1 on ! o!r h&1 su* z _m s&/ones1 h pore spaces s l>ge t wat] filt]s ?r\gh !m m or less freely4 ,besides its seepage ?r\gh ! pores ( p]vi\s rocks1 wat] passes to l[] levels ?r\gh ! jo9ts & cracks by :i* all rocks1 ne> ! surface are brok54 ,ev5 ! close/-gra9$ granite has a pore space ( #a 9 #djj1 :ile s&/one may h a pore space ( #a 9 #d4 ,s& is s por\s t x may absorb a ?ird ( its volume ( wat]1 & a loose loam ev5 z mu* z "o half4 ,illu/ration3 ,fig4 #bd4 ,diagram ,illu/rat+ ! ,relation ( ! ,gr\nd-,wat] ,surface to ! ,surface ( ! ,gr\nd ,! dott$ l9e repres5ts ! gr\nd-wat] surface1 & ! arr[s indicate ! direction ( ! movem5ts ( gr\nd-wat]4 m1 m>%2 w1 well2 r1 riv] ,! gr\nd-wat] surface is ! "n giv5 ! upp] surface ( gr\nd wat]1 ! level bel[ :i* all rocks are saturat$4 ,9 dry seasons ! gr\nd-wat] surface s9ks4 ,= gr\nd wat] is con/antly seep+ d[nw>d "u gravity1 x is evaporat$ 9 ! wa/e & its moi/ure is c>ri$ upw>d by capill>ity & ! roots ( plants to ! surface to be evaporat$ 9 ! air4 ,9 wet seasons ^! con/ant losses are m ?an made good by fre% supplies f t "p ( ! ra9fall :i* soaks into ! gr\nd1 & ! gr\nd-wat] surface rises4 ,9 moi/ climates ! gr\nd-wat] surface 7,fig4 #bd7 lies1 z a rule1 )9 a few feet ( ! l& surface & con=ms to x 9 a g5]al way1 al?\gh ) slopes ( less incl9ation ?an ^? ( ! hills & valleys4 ,9 dry climates p]man5t gr\nd wat] may be f\nd only at dep?s ( hundr$s ( feet4 ,gr\nd wat] is held at its height by ! fact t its circulation is con/antly imp$$ by capill>ity & friction4 ,if x 7 z free to dra9 away z are surface /reams1 x w\ld s9k soon aft] a ra9 to ! level ( ! deepe/ valleys ( ! region4 ,wells & spr+s4 ,excavations made 9 p]meable rocks bel[ ! gr\nd-wat] surface fill to its level & are kn[n z wells4 ,:]e valleys cut ?is surface p]man5t /reams are =m$1 ! wat] ei!r ooz+ =? along ill-def9$ areas or issu+ at def9ite po9ts call$ spr+s1 :]e x is conc5trat$ by ! /ructure ( ! rocks4 ,a level tract :]e ! gr\nd-wat] surface co9cides ) ! surface ( ! gr\nd is a swamp or m>%4 ,by /udy+ a spr+ "o may le>n mu* ( ! ways & "w ( gr\nd wat]4 ,spr+ wat] diff]s f t ( ! /ream into :i* x fl[s 9 sev]al respects4 ,if we te/ ! spr+ ) a !rmomet] dur+ successive mon?s1 we %all f9d t its temp]ature rema9s mu* ! same ! ye> r\nd4 ,9 summ] x is m>k$ly cool] ?an ! /ream2 9 w9t] x is w>m] & rema9s unfroz5 :ile ! latt] p]haps is lock$ 9 ice4 ,?is means t its und]gr\nd pa? mu/ lie at su* a di/ance f ! surface t x is little affect$ by summ]'s heat & w9t]'s cold4 ,:ile ! /ream is (t5 turbid ) surface wa/e wa%$ into x by ra9s1 ! spr+ rema9s cle>2 its wat] has be5 filt]$ dur+ its sl[ movem5t ?r\gh _m small und]gr\nd passages & ! pores ( rocks4 ,commonly ! spr+ diff]s f ! /ream 9 t x c>ries a f> l>g] load ( dissolv$ rock4 ,*emical analysis proves t /reams conta9 v>i\s m9]als 9 solution1 b ^! are usually 9 quantities s small t !y are n p]ceptible to ! ta/e or feel4 ,b ! wat] ( spr+s is (t5 well *>g$ ) soluble m9]als2 9 its sl[1 long j\rney und]gr\nd x has se>*$ out ! soluble p>ts ( ! rocks ?r\gh :i* x seeps & has dissolv$ z mu* ( !m z x c\ld4 ,:5 spr+ wat] is boil$ away1 ! invisible load :i* x has c>ri$ is left beh9d1 & 9 composition is f\nd to be practically id5tical ) t ( ! soluble +r$i5ts ( ! c\ntry rock4 ,al?\gh to "s ext5t ! soluble wa/e ( rocks is wa%$ d[n surface slopes by ! ra91 by f> ! l>g] "p is c>ri$ d[nw>d by gr\nd wat] & is deliv]$ to /reams by spr+s4 ,9 lime/one regions spr+s are *>g$ ) calcium c>bonate 7! c>bonate ( lime71 & :]e ! lime/one is magnesian !y conta9 magnesium c>bonate also4 ,su* wat]s are h>d2 :5 us$ 9 wa%+1 ! m9]als :i* !y conta9 comb9e ) ! fatty acids ( soap to =m insoluble curdy comp\nds4 ,:5 spr+s rise f rocks conta9+ gypsum !y are h>d ) calcium sulphate4 ,9 granite regions !y conta9 m or less soda & pota% f ! decay ( feldsp>4 ,! fl[ ( spr+s v>ies mu* less dur+ ! diff]5t seasons ( ! ye> ?an does t ( surface /reams4 ,s sl[ is ! movem5t ( gr\nd wat] ?r\gh ! rocks t ev5 dur+ long dr\ghts l>ge am\nts rema9 /or$ above ! levels ( surface dra9age4 ,movem5ts ( gr\nd wat]4 ,gr\nd wat] is 9 con/ant movem5t t[>d its outlets4 ,its rate v>ies accord+ to _m conditions1 b always is extremely sl[4 ,ev5 ?r\gh loose s&s b5ea? ! b$s ( riv]s x sometimes does n exce$ a fif? ( a mile a ye>4 ,illu/ration3 ,fig4 #bf4 ,geological ,conditions favorable to ,/rong ,spr+s a1 lime/one2 b1 %ale2 c1 co>se s&/one2 d1 lime/one2 e1 s&/one2 f1 fissure4 ,! /rata dip t[>d ! ,s\?1 ,s4 ,r$raw ! diagram1 m>k+ ! po9ts at :i* /rong spr+s 7ss7 may be expect$4 ,9 any region two zones ( fl[ may be di/+ui%$4 ,! upp] zone ( fl[ ext5ds f ! gr\nd-wat] surface d[nw>d ?r\gh ! wa/e mantle & any p]meable rocks on :i* ! mantle re/s1 z f> z ! fir/ imp]meable lay]1 :]e ! desc5d+ movem5t ( ! wat] is /opp$4 ,! deep zones ( fl[ occupy any p]vi\s rocks :i* may be f\nd bel[ ! imp]vi\s lay] :i* lies ne>e/ to ! surface4 ,! upp] zone is a va/ %eet ( wat] saturat+ ! soil & rocks & sl[ly seep+ d[nw>d ?r\gh _! pores & int]/ices along ! slopes to ! valleys1 :]e 9 "p x dis*>ges 9 spr+s & (t5 unites also 9 a wide und]fl[+ /ream :i* supports & fe$s ! riv] 7,fig4 #bd74 ,illu/ration3 ,fig4 #bg4 ,diagram ( ,well :i* goes dry 9 ,dr\ght1 a1 & ( ( ,unfail+ ,well1 b ,r$raw ! diagram1 %[+ by dott$ l9e ! normal gr\nd-wat] surface & by brok5 l9e ! gr\nd-wat] surface at times ( dr\ght ,illu/ration3 ,fig4 #bh4 ,diagram ( ,wet ,wea!r ,/ream1 a1 & ( ,p]man5t ,/ream1 b ,r$raw ! diagram1 %[+ gr\nd-wat] surface by dott$ l9e ,a city 9 a region ( copi\s ra9s1 built on ! n>r[ flood pla9 ( a riv]1 ov]look$ by hills1 dep5ds = its wat] supply on driv5 wells1 )9 ! city limits1 sunk 9 ! s& a few y>ds f ! edge ( ! /ream4 ,are ^! wells f$ by wat] f ! riv] p]colat+ ?r\gh ! s&1 or by gr\nd wat] on its way to ! /ream & possibly contam9at$ ) ! sewage ( ! t[n8 ,at :at height does und]gr\nd wat] /& 9 ! wells ( y\r region8 ,does x v>y ) ! season8 ,h y ev] kn[n wells to g dry8 ,x may be possible to get data f diff]5t wells & to draw a diagram %[+ ! gr\nd-wat] surface z comp>$ ) ! surface ( ! gr\nd4 ,fissure spr+s & artesian wells4 ,! deep] zones ( fl[ lie 9 p]vi\s /rata :i* are ov]la9 by "s imp]vi\s /ratum4 ,su* lay]s are (t5 c>ri$ by _! dip to great dep?s1 & wat] may circulate 9 !m to f> bel[ ! level ( ! surface /reams & ev5 ( ! sea4 ,:5 a fissure crosses a wat]-be>+ /ratum1 or aquif]1 wat] is =c$ upw>d by ! pressure ( ! weight ( ! wat] conta9$ 9 ! high] p>ts ( ! /ratum1 & may rea* ! surface z a fissure spr+4 ,a bor+ :i* taps su* an aquif] is kn[n z an artesian well1 a "n d]iv$ f a prov9ce 9 ,france :]e wells ( ?is k9d h be5 long 9 use4 ,! rise ( ! wat] 9 artesian wells1 & 9 fissure spr+s also1 dep5ds on ! foll[+ conditions illu/rat$ 9 ,figure #bi4 ,! aquif] dips t[>d ! region ( ! wells f high] gr\nd1 :]e x outcrops & receives its wat]4 ,x is inclos$ betwe5 an imp]vi\s lay] above & wat]-tight or wat]-logg$ lay]s b5ea?4 ,! weight ( ! column ( wat] ?us inclos$ 9 ! aquif] causes wat] to rise 9 ! well1 precisely z ! weight ( ! wat] 9 a /&pipe =ces x 9 connect$ pipes to ! upp] /ories ( build+s4 ,illu/ration3 ,fig4 #bi4 ,section across ,s\? ,dakota f ! ,black ,hills to ,si\x ,falls 7,s71 ,illu/rat+ ! ,conditions ( ,artesian ,wells a1 cry/all9e imp]vi\s rocks2 b1 s$im5t>y rocks1 %ales1 lime/ones1 & s&/ones2 c1 p]vi\s s&/one1 ! aquif]2 d1 imp]vi\s %ales2 w1 w1 w1 artesian wells4 ,:i* w supply ! l>g] region ) artesian wells1 an aquif] ^: dip is /eep or "o ^: dip is g5tle8 ,:i* ( ! two aquif]s1 _! ?ickness be+ equal1 w h ! l>g] outcrop & !re=e be able to draw ^u ! l>g] am\nt ( wat] f ! ra9fall8 ,illu/rate ) diagrams4 ,! zone ( solution4 ,ne> ! surface1 :]e ! circulation ( gr\nd wat] is mo/ active1 x oxidizes1 corrodes1 & dissolves ! rocks ?r\gh :i* x passes4 ,x lea*es soils & subsoils ( _! lime & o!r soluble m9]als ^u :i* plants dep5d = _! food4 ,x takes away ! soluble cem5ts ( rocks2 x wid5s fissures & jo9ts & op5s w9d+ passages along ! b$d+ planes2 x may ev5 remove :ole b$s ( soluble rocks1 su* z rock salt1 lime/one1 or gypsum4 ,! "w ( gr\nd wat] 9 produc+ l&slides has already be5 notic$4 ,! zone 9 :i* ! "w ( gr\nd wat] is ?us = ! mo/ "p de/ructive we may call ! zone ( solution4 ,illu/ration3 ,fig4 #cj4 ,diagram ( ,cav]ns & ,s9k ,holes ,caves4 ,9 massive lime/one rocks1 gr\nd wat] dissolves *annels :i* sometimes =m l>ge caves 7,fig4 #cj74 ,! necess>y conditions = ! excavation ( caves ( great size are well %[n 9 c5tral ,k5tucky1 :]e an upl& is built ?r\gh\t ( ?ick horizontal b$s ( lime/one4 ,! abs5ce ( lay]s ( insoluble or imp]vi\s rock 9 its /ructure all[s a free circulation ( gr\nd wat] )9 x by ! way ( all natural op5+s 9 ! rock4 ,^! wat] ways h be5 gradually enl>g$ by solution & we> until ! upl& is honeycomb$ ) caves4 ,five hundr$ op5 cav]ns are kn[n 9 "o c\nty4 ,mammo? ,cave1 ! l>ge/ ( ^! cav]ns1 consi/s ( a labyr9? ( *amb]s & w9d+ gall]ies ^: total l5g? is said to be z mu* z ?irty miles4 ,"o passage f\r miles long has an av]age wid? ( ab\t sixty feet & an av]age height ( =ty feet4 ,"o ( ! great halls is ?ree hundr$ feet 9 wid? & is ov]hung by a solid ar* ( lime/one "o hundr$ feet above ! floor4 ,gall]ies at diff]5t levels are connect$ by well-l pits1 "s ( :i* measure two hundr$ & tw5ty-five feet f top to bottom4 ,?r\gh "s ( ! l[e/ ( ^! tunnels fl[s ,e*o ,riv]1 /ill at "w dissolv+ & we>+ away ! rock :ile on its d>k way to appe> at ! surface z a great spr+4 ,natural bridges4 ,z a cav]n enl>ges & ! surface ( ! l& above x is l[]$ by wea!r+1 ! ro( at la/ breaks d[n & ! cave becomes an op5 rav9e4 ,a portion ( ! ro( may = a :ile rema91 =m+ a natural bridge4 ,s9k holes4 ,9 lime/one regions *annels "u gr\nd may become s well develop$ t ! wat] ( ra9s rapidly dra9s away ?r\gh !m4 ,gr\nd wat] /&s l[ & wells mu/ be sunk deep to f9d x4 ,little or no surface wat] is left to =m brooks4 ,illu/ration3 ,fig4 #ca4 ,s9k ,holes 9 ! ,k>/1 ,au/ria ,?us across ! lime/one upl& ( c5tral ,k5tucky "o meets b ?ree surface /reams 9 a hundr$ miles4 ,betwe5 _! valleys surface wat] f9ds its way und]gr\nd by means ( s9k holes4 ,^! are pits1 commonly funnel %ap$1 =m$ by ! enl>gem5t ( crevice or jo9t by p]colat+ wat]1 or by ! breakd[n ( "s portion ( ! ro( ( a cave4 ,by clogg+ ( ! outlet a s9k hole may come to be fill$ by a pond4 ,c5tral ,florida is a lime/one region ) its dra9age l>gely subt]ranean & 9 "p bel[ ! level ev5 ( ! sea4 ,s9k holes are common1 & _m ( !m are occupi$ by lakelets4 ,great spr+s m>k ! po9t ( issue ( und]gr\nd /reams1 :ile "s rise f b5ea? ! sea4 ,silv] ,spr+1 "o ( ! l>ge/1 dis*>ges f a bas9 eight hundr$ feet wide & ?irty feet deep a little riv] navigable = small /eam]s to its s\rce4 ,ab\t ! spr+ !re are no surface /reams = sixty miles4 ,illu/ration3 ,fig4 #cb4 ,und]gr\nd ,/ream ,issu+ f ,base ( ,cliff1 ! ,k>/1 ,au/ria ,! ,k>/4 ,along ! ea/]n coa/ ( ! ,adriatic1 z f> s\? z ,mont5egro1 lies a belt ( lime/one m\nta9s s+ul>ly worn & honeycomb$ by ! solv5t action ( wat]4 ,:]e =e/s h be5 cut f ! m\nta9 sides & ! r$ soil has wa%$ away1 ! surface ( ! :ite lime/one =ms a pa?less des]t ( rock :]e ea* squ>e rod has be5 corrod$ into an intricate bran* "w ( %all[ furr[s & %>p ridges4 ,great s9k holes1 "s ( !m six hundr$ feet deep & m1 pockm>k ! surface ( ! l&4 ,! dra9age is *iefly subt]ranean4 ,surface /reams are r>e & a portion ( _! c\rses is (t5 "u gr\nd4 ,fragm5t>y valleys come sudd5ly to an end at walls ( rock :]e ! riv]s :i* occupy ! valleys plunge into d>k tunnels to reappe> "s miles away4 ,gr\nd wat] /&s s f> bel[ ! surface t x _c be rea*$ by wells1 & ! inhabitants dep5d on ra9 wat] /or$ = h\sehold uses4 ,! f9e/ cav]n ( ,europe1 ! ,adelsb]g ,grotto1 is 9 ?is region4 ,k>/1 ! "n ( a "p ( ?is c\ntry1 is n[ us$ to designate any region or l&scape ?us sculptur$ by ! *emical action ( surface & gr\nd wat]4 ,we mu/ rememb] t ,k>/ regions are r>e1 & /rik+ z is ! "w ( _! subt]ranean /reams1 x is f> less important ?an ! "w done by ! %eets ( und]gr\nd wat] sl[ly seep+ ?r\gh all subsoils & por\s rocks 9 o!r regions4 ,ev5 :5 ga!r$ into def9ite *annels1 gr\nd wat] does n h ! erosive p[] ( surface /reams1 s9ce x c>ries ) x little or no rock wa/e4 ,regions ^: und]gr\nd dra9age is s p]fect t ! developm5t ( surface /reams has be5 ret>d$ or prev5t$ escape to a l>ge ext5t ! level+ action ( surface runn+ wat]s1 & may !re=e /& high] ?an ! surr\nd+ c\ntry4 ,! hill honeycomb$ by ,luray ,cav]n1 ,virg9ia1 has be5 attribut$ to ?is cause4 ,illu/ration3 ,fig4 #cc4 ,/alactites & ,/alagmites1 ,m>5go ,cav]n1 ,indiana ,cav]n deposits4 ,ev5 9 ! zone ( solution wat] may "u c]ta9 circum/ances deposit z well z erode4 ,z x trickles f ! ro( ( cav]ns1 ! lime c>bonate :i* x has tak5 into solution f ! lay]s ( lime/one above is deposit$ by evaporation 9 ! air 9 icicle-l p5dants call$ /alactites4 ,z ! drops spla% on ! floor !re are built up 9 ! same way ?ick] masses call$ /alagmites1 :i* may gr[ to jo9 ! /alactites above1 =m+ pill>s4 ,a /alagmitic cru/ (t5 seals ) rock ! e>? :i* accumulates 9 cav]ns1 toge!r ) :atev] relics ( cave dwell]s1 ei!r animals or m51 x may conta94 ,c y expla9 :y sl5d] /alactites =m$ by ! drip ( s+le drops are (t5 holl[ pipes8 ,! zone ( cem5tation4 ,) increas+ dep? subt]ranean wat] becomes m & m sluggi% 9 its movem5ts & m & m highly *>g$ ) m9]als dissolv$ f ! rocks above4 ,at su* dep?s x deposits ^! m9]als 9 ! pores ( rocks1 cem5t+ _! gra9s toge!r1 & 9 crevices & fissures1 =m+ m9]al ve9s4 ,?us bel[ ! zone ( solution :]e ! "w ( wat] is to dissolve1 lies ! zone ( cem5tation :]e its "w is *emical deposit4 ,a "p ( ! invisible load ( wa/e is ?us transf]r$ f rocks ne> ! surface to ^? at great] dep?s4 ,z ! l& surface is gradually l[]$ by wea!r+ & ! "w ( ra9 & /reams1 rocks :i* h la9 deep )9 ! zone ( cem5tation are br\ght )9 ! zone ( solution4 ,?us !re are expos$ to view lime/ones1 ^: cracks 7 fill$ ) calcite 7cry/alliz$ c>bonate ( lime71 ) qu>tz or o!r m9]als1 & s&/ones ^: gra9s 7 well cem5t$ _m feet bel[ ! surface4 ,cavity fill+4 ,small cavities 9 ! rocks are (t5 f\nd m or less completely fill$ ) m9]als deposit$ f solution by wat] 9 its con/ant circulation und]gr\nd4 ,! process may be illu/rat$ by ! deposit ( salt cry/als 9 a cup ( evaporat+ br9e1 b 9 ! latt] in/ance ! solution is n r5ew$ z 9 ! case ( cavities 9 ! rocks4 ,a cavity ?us l9$ ) inw>d-po9t+ cry/als is call$ a geode4 ,concretions4 ,gr\nd wat] seep+ ?r\gh ! pores ( rocks may ga!r m9]als dissem9at$ ?r\gh\t !m into nodul> masses call$ concretions4 ,?us silica dissem9at$ ?r\gh lime/one is ga!r$ into nodules ( fl9t4 ,:ile geodes gr[ f ! outside inw>ds1 concretions gr[ outw>ds f ! c5t]4 ,nor are !y =m$ 9 already exi/+ cavities z are geodes4 ,9 s(t clays concretions may1 z !y gr[1 press ! clay aside4 ,9 _m o!r rocks concretions are made by ! process ( replacem5t4 ,molecule by molecule ! rock is remov$ & ! m9]al ( ! concretion sub/itut$ 9 its place4 ,! concretion may 9 ?is way pres]ve intact ! lam9ation l9es or o!r /ructures ( ! rock 7,fig4 #cd74 ,clays & %ales (t5 conta9 concretions ( lime c>bonate1 ( iron c>bonate1 or ( iron sulphide4 ,"s fossil1 su* z a leaf or %ell1 frequ5tly =ms ! nucleus ar\nd :i* ! concretion gr[s4 ,:y are build+ /ones m easily work$ :5 gre5 ?an aft] _! qu>ry wat] has dri$ out8 ,illu/ration3 ,fig4 #cd4 ,concretions 9 ,s&/one1 ,wyom+ ,deposits ( gr\nd wat] 9 arid regions4 ,9 arid l&s :]e gr\nd wat] is drawn by capill>ity to ! surface & !re evaporates1 x leaves z surface incru/ations ! m9]als held 9 solution4 ,:ite limy incru/ations ( ?is nature cov] consid]able tracts 9 nor!rn ,mexico4 ,evaporat+ b5ea? ! surface1 gr\nd wat] may deposit a limy cem5t 9 b$s ( loose s& & gravel4 ,su* firmly cem5t$ lay]s are n uncommon 9 we/]n ,kansas & ,nebraska1 :]e !y are kn[n z mort> b$s4 ,!rmal spr+s4 ,:ile ! l[] limit ( surface dra9age is sea level1 subt]ranean wat] circulates mu* bel[ t dep?1 & is br\ght aga9 to ! surface by hydro/atic pressure4 ,9 _m in/ances spr+s h a high] temp]ature ?an ! av]age annual temp]ature ( ! region1 & are !n kn[n z !rmal spr+s4 ,9 regions ( pres5t or rec5t volcanic activity1 su* z ! ,yell[/one ,national ,p>k1 we may believe t ! heat ( !rmal spr+s is d]iv$ f uncool$ lavas1 p]haps n f> bel[ ! surface4 ,b :5 hot spr+s occur at a di/ance ( hundr$s ( miles f any volcano1 z 9 ! case ( ! hot spr+s ( ,ba?1 ,engl&1 x is probable t _! wat]s h ris5 f ! heat$ rocks ( ! e>?'s int]ior4 ,! spr+s ( ,ba? h a temp]ature ( #abj ,f41 #gj above ! av]age annual temp]ature ( ! place4 ,if we assume t ! rate ( increase 9 ! e>?'s int]nal heat is "h ! av]age rate1 #a ,f4 to e sixty feet ( desc5t1 we may conclude t ! spr+s ( ,ba? rise f at lea/ a dep? ( =ty-two hundr$ feet4 ,wat] may desc5d to dep?s f :i* x c nev] be br\ght back by hydro/atic pressure4 ,x is absorb$ by highly heat$ rocks deep bel[ ! surface4 ,f "t to "t "s ( ?is deep-seat$ wat] may be return$ to op5 air 9 ! /eam ( volcanic eruptions4 ,illu/ration3 ,fig4 #ce4 ,calc>e\s ,deposits f ,hot ,spr+s1 ,yell[/one ,national ,p>k ,surface deposits ( spr+s4 ,:]e subt]ranean wat] returns to ! surface highly *>g$ ) m9]als 9 solution1 on exposure to ! air x is commonly compell$ to lay d[n mu* ( its invisible load 9 *emical deposits ab\t ! spr+4 ,^! are ?r[n d[n f solution ei!r because ( cool+1 evaporation1 ! loss ( c>bon dioxide1 or ! "w ( algae4 ,_m spr+s h be5 *>g$ "u pressure ) c>bon dioxide f subt]ranean s\rces & are able !re=e to take up l>ge quantities ( lime c>bonate f ! lime/one rocks ?r\gh :i* !y pass4 ,on rea*+ ! surface ! pressure is reliev$1 ! gas escapes1 & ! lime c>bonate is ?r[n d[n 9 deposits call$ trav]t9e4 ,! gas is sometimes )drawn & ! deposit produc$ 9 l>ge "p by ! action ( algae & o!r humble =ms ( plant life4 ,at ! ,mammo? ,hot ,spr+s 9 ! valley ( ! ,g>d9] ,riv]1 ,yell[/one ,national ,p>k1 beautiful t]races & bas9s ( trav]t9e 7,fig4 #ce7 are n[ build+1 *iefly by means ( algae :i* cov] ! bottoms1 rims1 & sides ( ! bas9s & deposit lime c>bonate ^u !m 9 successive %eets4 ,! rock1 sn[-:ite :]e dry1 is coat$ ) r$ & orange gelat9\s mats :]e ! algae ?rive 9 ! ov]-fl[+ wat]s4 ,simil> t]races ( trav]t9e are f\nd to a height ( f\rte5 hundr$ feet up ! valley side4 ,we may inf] t ! spr+s :i* =m$ ^! anci5t deposits dis*>g$ ne> :at 0 !n ! bottom ( ! valley1 & t z ! valley has be5 deep5$ by ! riv] ! gr\nd wat] ( ! region has f\nd l[] & l[] po9ts ( issue4 ,9 _m p>ts ( ! c\ntry calc>e\s spr+s occur :i* coat ) lime c>bonate mosses1 twigs1 & o!r objects ov] :i* _! wat]s fl[4 ,su* are popul>ly kn[n z petrify+ spr+s1 al?\gh !y m]ely incru/ ! objects & d n conv]t !m into /one4 ,silica is soluble 9 alkal9e wat]s1 especially :5 ^! are hot4 ,hot spr+s ris+ ?r\gh alkal9e silice\s rocks1 su* z lavas1 (t5 deposit silica 9 a :ite spongy =mation kn[n z silice\s s9t]1 bo? by evaporation & by ! action ( algae :i* secrete silica f ! wat]s4 ,x is 9 ?is way t ! cones & m\nds ( ! geys]s 9 ! ,yell[/one ,national ,p>k & 9 ,icel& h be5 =m$ 7,fig4 #bcd74 ,:]e wat] oozes f ! e>? "o may sometimes see a ru/y deposit on ! gr\nd1 & p]haps an iridesc5t scum ^u ! wat]4 ,! scum is (t5 mi/ak5 = oil1 b at a t\* x cracks & breaks1 z oil w\ld n d4 ,x is a film ( hydrat$ iron oxide1 or limonite1 & ! spr+ is an iron1 or *alybeate1 spr+4 ,comp\nds ( iron h be5 tak5 into solution by gr\nd wat] f soil & rocks1 & are n[ *ang$ to ! insoluble oxide on exposure to ! oxyg5 ( ! air4 ,9 wet gr\nd iron comp\nds lea*$ by gr\nd wat] f ! soil (t5 collect 9 r$di% deposits a few feet bel[ ! surface1 :]e _! d[nw>d progress is arre/$ by "s imp]vi\s clay4 ,at ! bottom ( bogs & %all[ lakes iron ores sometimes accumulate to a dep? ( sev]al feet4 ,decay+ organic matt] plays a l>ge "p 9 ^! *anges4 ,9 its pres5ce ! insoluble iron oxides :i* give color to mo/ r$ & yell[ rocks are decompos$1 leav+ ! rocks ( a gray or blui% color1 & ! soluble iron comp\nds :i* result are readily lea*$ out1--effects se5 :]e r$ or yell[ clays h be5 blea*$ ab\t "s decay+ tree root4 ,! iron ?us dissolv$ is laid d[n z limonite :5 oxidiz$1 z ab\t a *alybeate spr+2 b out ( contact ) ! air & 9 ! pres5ce ( c>bon dioxide suppli$ by decay+ vegetation1 z 9 a peat bog1 x may be deposit$ z iron c>bonate1 or sid]ite4 ,total am\nt ( und]gr\nd wat]s4 ,9 ord] to realize ! va/ "w 9 solution & cem5tation :i* und]gr\nd wat]s are n[ do+ & h done 9 all geological ages1 we mu/ ga9 "s conception ( _! am\nt4 ,at a c]ta9 dep?1 e/imat$ at ab\t six miles1 ! weight ( ! cru/ becomes great] ?an ! rocks c be>1 & all cavities & pores 9 !m mu/ be completely clos$ by ! enorm\s pressure :i* !y su/a94 ,bel[ a dep?1 !re=e1 wat] _c g4 ,above x all rocks are wat]-soak$1 up to ! limit ( _! capacity1 to )9 a few feet ( ! surface4 ,e/imat+ ! av]age pore space ( ! rocks above a dep? ( six miles at f two & a half p] c5t to five p] c5t ( _! volume1 x is f\nd t ! total am\nt ( gr\nd wat] may be great en\gh to cov] ! entire surface ( ! e>? to a dep? ( f eight hundr$ to sixte5 hundr$ feet4 ,,*apt] ,,iii ,,riv]s ,,& ,,valleys ,! run-(f4 ,we h trac$ ! hi/ory ( t portion ( ! ra9fall :i* soaks into ! gr\nd2 let u n[ return to t "p :i* wa%es along ! surface & is kn[n z ! run-(f4 ,f$ by ra9s & melt+ sn[s1 ! run-(f ga!rs into c\rses1 p]haps b fa9tly m>k$ at fir/1 :i* jo9 m def9ite & deeply cut *annels1 z twigs _! /ems4 ,9 a humid climate ! l>g] rav9es ?r\gh :i* ! run-(f fl[s soon desc5d bel[ ! gr\nd-wat] surface4 ,"h spr+s dis*>ge along ! sides ( ! little valleys & p]man5t /reams beg94 ,! wat] suppli$ by ! run-(f "h jo9s t "p ( ! ra9fall :i* _h soak$ into ! soil1 & bo? n[ proce$ toge!r by way ( ! /ream to ! sea4 ,riv] floods4 ,/reams v>y greatly 9 volume dur+ ! ye>4 ,at /ages ( flood !y fill _! imm$iate banks1 or ov]run !m & inundate any l[ l&s adjac5t to ! *annel2 at /ages ( l[ wat] !y dim9i% to b a fraction ( _! volume :5 at flood4 ,at times ( flood1 riv]s are f$ *iefly by ! run-(f2 at times ( l[ wat]1 l>gely or ev5 :olly by spr+s4 ,h[1 !n1 w ! wat] ( /reams diff] at ^! times 9 turbidity & 9 ! relative am\nt ( solids c>ri$ 9 solution8 ,9 p>ts ( ,engl& /reams h be5 kn[n to cont9ue fl[+ aft] eighte5 mon?s ( local dr\ght1 s great is ! volume ( wat] :i* 9 humid climates is /or$ 9 ! rocks above ! dra9age level1 & s sl[ly is x giv5 (f 9 spr+s4 ,9 ,ill9ois & ! /ates adjac5t1 riv]s rema9 l[ 9 w9t] & a spr+ fre%et foll[s ! melt+ ( ! w9t]'s sn[s4 ,a ,june rise is produc$ by ! heavy ra9s ( e>ly summ]4 ,l[ wat] foll[s 9 ,july & ,augu/1 & /reams are aga9 swoll5 to a mod]ate degree "u ! ra9s ( autumn4 ,! dis*>ge ( /reams4 ,! p] c5t ( ra9fall dis*>g$ by riv]s v>ies ) ! am\nt ( ra9fall1 ! slope ( ! dra9age area1 ! texture ( ! rocks1 & o!r factors4 ,) an annual ra9fall ( fifty in*es 9 an op5 c\ntry1 ab\t fifty p] c5t is dis*>g$2 :ile ) a ra9fall ( tw5ty in*es only fifte5 p] c5t is dis*>g$1 "p ( ! rema9d] be+ evaporat$ & "p pass+ und]gr\nd beyond ! dra9age area4 ,?us ! ,ohio dis*>ges ?irty p] c5t ( ! ra9fall ( its bas91 :ile ! ,miss\ri c>ries away b fifte5 p] c5t4 ,a numb] ( ! /reams ( ! semi-arid l&s ( ! ,we/ d n dis*>ge m ?an five p] c5t ( ! ra9fall4 ,o!r ?+s be+ equal1 :i* w af=d ! l>g] proportion ( run-(f1 a region und]la9 ) granite rock or ) co>se s&/one8 grass l& or =e/8 /eep slopes or level l&8 a well-dra9$ region or "o ab\nd+ 9 m>%es & ponds8 froz5 or unfroz5 gr\nd8 ,w !re be a l>g] proportion ( run-(f aft] long ra9s or aft] a season ( dr\ght8 aft] long & g5tle ra9s1 or aft] ! same am\nt ( precipitation 9 a viol5t ra98 dur+ ! mon?s ( gr[+ vegetation1 f ,june to ,augu/1 or dur+ ! autumn mon?s8 ,illu/ration3 ,fig4 #cf4 ,rise ( ,gr\nd-,wat] ,surface 7brok5 l9e7 b5ea? ,valley 7,v7 9 ,arid ,region ,des]t /reams4 ,9 arid regions ! gr\nd-wat] surface lies s l[ t = ! mo/ "p /ream ways d n int]sect x4 ,/reams !re=e are n f$ by spr+s1 b in/ead lose volume z _! wat]s soak into ! ?ir/y rocks ov] :i* !y fl[4 ,!y contribute to ! gr\nd wat] ( ! region in/ead ( be+ increas$ by x4 ,be+ suppli$ *iefly by ! run-(f1 !y )] at times ( dr\ght to a m]e trickle ( wat]1 to a *a9 ( pools1 or g :olly dry1 :ile at long int]vals ra9s fill _! du/y b$s ) sudd5 rag+ torr5ts4 ,des]t riv]s !re=e p]iodically %ort5 & l5g!n _! c\rses1 )]+ back at times ( dr\ght = scores ( miles1 or ev5 = a hundr$ miles f ! po9t rea*$ by _! wat]s dur+ seasons ( ra94 ,! geological "w ( /reams4 ,! "w ( /reams is ( ?ree k9ds1--transportation1 erosion1 & deposition4 ,/reams transport ! wa/e ( ! l&2 !y we>1 or erode1 _! *annels bo? on b$ & banks2 & !y deposit portions ( _! load f "t to "t along _! c\rses1 f9ally lay+ x d[n 9 ! sea4 ,mo/ ( ! "w ( /reams is done at times ( flood4 ,transportation ,! invisible load ( /reams4 ,( ! wa/e :i* a riv] transports we may consid] fir/ ! invisible load :i* x c>ries 9 solution1 suppli$ *iefly by spr+s b also 9 "p by ! run-(f & f ! solution ( ! rocks ( its b$4 ,m ?an half ! dissolv$ solids 9 ! wat] ( ! av]age riv] consi/s ( ! c>bonates ( lime & magnesia2 o!r sub/ances are gypsum1 sodium sulphate 7,glaub]'s salts71 magnesium sulphate 7,epsom salts71 sodium *loride 7common salt71 & ev5 silica1 ! lea/ soluble ( ! common rock-mak+ m9]als4 ,! am\nt ( ?is invisible load is surpris+ly l>ge4 ,! ,mississippi1 = example1 transports ea* ye> #aac1jjj1jjj tons ( dissolv$ rock to ! ,gulf4 ,! visible load ( /reams4 ,?is consi/s ( ! silt :i* ! /ream c>ries 9 susp5sion1 & ! s& & gravel & l>g] /ones :i* x pu%es along its b$4 ,especially 9 times ( flood "o may note ! muddy wat]1 its silt be+ kept f settl+ by ! roll+1 eddy+ curr5ts2 & (t5 by plac+ 8 e> close to ! bottom ( a boat "o may he> ! clatt] ( pebbles z !y are hurri$ along4 ,9 m\nta9 torr5ts ! rumble ( b[ld]s z !y cla% toge!r may be he>d "s di/ance away4 ,! am\nt ( ! load :i* a /ream c transport dep5ds on its velocity4 ,a curr5t ( two ?irds ( a mile p] h\r c move f9e s&1 :ile "o ( f\r miles p] h\r sweeps along pebbles z l>ge z h5's eggs4 ,! transport+ p[] ( a /ream v>ies z ! six? p[] ( its velocity4 ,if its velocity is multipli$ by two1 its transport+ p[] is multipli$ by ! six? p[] ( two3 x c n[ move /ones sixty-f\r times z l>ge z x c\ld be=e4 ,/ones weigh f two to ?ree times z mu* z wat]1 & 9 wat] lose ! weight ( ! volume ( wat] :i* !y displace4 ,:at proportion1 !n1 ( _! weight 9 air d /ones lose :5 subm]g$8 ,measurem5t ( /ream loads4 ,to obta9 ! total am\nt ( wa/e transport$ by a riv] is an important b difficult matt]4 ,! am\nt ( wat] dis*>g$ mu/ fir/ be f\nd by multiply+ ! numb] ( squ>e feet 9 ! av]age cross section ( ! /ream by its velocity p] second1 giv+ ! dis*>ge p] second 9 cubic feet4 ,! am\nt ( silt to a cubic foot ( wat] is f\nd by filt]+ samples ( ! wat] tak5 f diff]5t p>ts ( ! /ream & at diff]5t times 9 ! ye>1 & dry+ & weigh+ ! residues4 ,! av]age am\nt ( silt to ! cubic foot ( wat]1 multipli$ by ! numb] ( cubic feet ( wat] dis*>g$ p] ye>1 gives ! total load c>ri$ 9 susp5sion dur+ t "t4 ,add+ to ?is ! e/imat$ am\nt ( s& & gravel roll$ along ! b$1 :i* 9 _m swift riv]s greatly exce$s ! light] mat]ial held 9 susp5sion1 & add+ also ! total am\nt ( dissolv$ solids1 we rea* ! exce$+ly important result ( ! total load ( wa/e dis*>g$ by ! riv]4 ,divid+ ! volume ( ?is load by ! area ( ! riv] bas9 gives ano!r result ( ! greate/ geological int]e/1--! rate at :i* ! region is be+ l[]$ by ! comb9$ action ( wea!r+ & erosion1 or ! rate ( d5udation4 ,! rate ( d5udation ( riv] bas9s4 ,?is rate v>ies widely4 ,! ,mississippi bas9 may be tak5 z a repres5tative l& surface because ( ! v>ieties ( surface1 altitude & slope1 climate1 & und]ly+ rocks :i* are includ$ 9 its great ext5t4 ,c>eful measurem5ts %[ t ! ,mississippi bas9 is n[ be+ l[]$ at a rate ( "o f\r-?\s&? ( a foot a ye>1 or "o foot 9 f\r ?\s& ye>s4 ,tak+ ?is z ! av]age rate ( d5udation = ! l& surfaces ( ! globe1 e/imates h be5 made ( ! l5g? ( "t requir$ at ?is rate to wa% & we> ! cont95ts to ! level ( ! sea4 ,z ! av]age elevation ( ! l&s ( ! globe is reckon$ at #bdaa feet1 ?is result w\ld occur 9 n9e or t5 million ye>s1 if ! pres5t rate ( d5udation %\ld rema9 un*ang$4 ,b ev5 if no movem5ts ( ! e>?'s cru/ %\ld lift or depress ! cont95ts1 ! rate ( we> & ! removal ( wa/e f _! surfaces w n rema9 ! same4 ,x mu/ con/antly decrease z ! l&s are worn ne>] to sea level & _! slopes become m g5tle4 ,! l5g? ( "t requir$ to we> !m away is !re=e f> 9 excess ( t j /at$4 ,! dra9age area ( ! ,potomac is #aa1jjj squ>e miles4 ,! silt br\ght d[n 9 susp5sion 9 a ye> w\ld cov] a squ>e mile to ! dep? ( f\r feet4 ,at :at rate is ! ,potomac bas9 be+ l[]$ f ?is cause alone8 ,x is e/imat$ t ! ,upp] ,ganges is l[]+ its bas9 at ! rate ( "o foot 9 #hbc ye>s1 & ! ,po "o foot 9 #gbj ye>s4 ,:y s mu* fa/] ?an ! ,potomac & ! ,mississippi8 ,h[ /reams get _! loads4 ,! load ( /reams is d]iv$ f a numb] ( s\rces1 ! l>g] "p be+ suppli$ by ! wea!r+ ( valley slopes4 ,we h notic$ h[ ! mantle ( wa/e creeps & wa%es to ! /ream ways4 ,wat*+ ! run-(f dur+ a ra91 z x hurries muddy ) wa/e along ! gutt] or wa%es d[n ! hillside1 we may see ! beg9n+ ( ! r\te by :i* ! l>g] "p ( _! load is deliv]$ to riv]s4 ,/reams also secure "s ( _! load by we>+ x f _! b$s & banks1--a process call$ erosion4 ,erosion ,/reams erode _! b$s *iefly by means ( _! bottom load1--! /ones ( v>i\s sizes & ! s& & ev5 ! f9e mud :i* !y sweep along4 ,) ^! tools !y smoo?1 gr9d1 & rasp ! rock ( _! b$s1 us+ !m 9 mu* ! fa%ion ( s&pap] or a file4 ,illu/ration3 ,fig4 #cg4 ,po?ole 9 ,b$ ( ,/ream1 ,irel& ,wea!r+ ( riv] b$s4 ,! erosion ( /ream b$s is greatly help$ by ! "w ( ! wea!r4 ,especially at l[ wat] m or less ( ! b$ is expos$ to ! action ( fro/ & heat & cold1 jo9ts are op5$1 rocks are pri$ loose & brok5 up & made ready to be swept away by ! /ream at "t ( flood4 ,po?oles4 ,9 rapids /reams also drill out _! rocky b$s4 ,:]e "s slight depression gives rise to an eddy1 ! pebbles :i* ga!r 9 x are :irl$ r\nd & r\nd1 &1 act+ l ! bit ( an aug]1 bore out a cyl9drical pit call$ a po?ole4 ,po?oles sometimes rea* a dep? ( a score ( feet4 ,:]e !y are num]\s !y aid mat]ially 9 deep5+ ! *annel1 z ! walls betwe5 !m are worn away & !y coalesce4 ,wat]falls4 ,"o ( ! mo/ effective means ( erosion :i* ! riv] possesses is ! wat]fall4 ,! plung+ wat] dislodges /ones f ! face ( ! l$ge ov] :i* x p\rs1 & (t5 und]m9es x by excavat+ a deep pit at its base4 ,slice aft] slice is ?us ?r[n d[n f ! front ( ! cliff1 & ! cat>act cuts its way up/ream leav+ a gorge beh9d x4 ,illu/ration3 ,fig4 #ch4 ,map ( ! ,gorge ( ! ,niag>a ,riv] ,niag>a ,falls4 ,! ,niag>a ,riv] fl[s f ,lake ,erie at ,buffalo 9 a broad *annel :i* x has cut b a few feet bel[ ! level ( ! region4 ,"s ?irte5 miles f ! outlet x plunges ov] a l$ge "o hundr$ & sev5ty feet high into ! head ( a n>r[ gorge :i* ext5ds = sev5 miles to ! esc>pm5t ( ! upl& 9 :i* ! gorge is cut4 ,! /rata :i* compose ! upl& dip g5tly up/ream & consi/ at top ( a massive lime/one1 at ! ,falls ab\t eighty feet ?ick1 & bel[ ( s(t & easily wea!r$ %ale4 ,b5ea? ! ,falls ! und]ly+ %ale is cut & wa%$ away by ! desc5d+ wat] & retreats also because ( wea!r+1 :ile ! ov]hang+ lime/one breaks d[n 9 huge blocks f "t to "t4 ,niag>a is divid$ by ,goat ,isl& into ! ,horse%oe ,falls & ! ,am]ican ,falls4 ,! =m] is suppli$ by ! ma9 curr5t ( ! riv]1 & f ! semicircul> sweep ( its rim a %eet ( wat] 9 places at lea/ fifte5 or tw5ty feet deep plunges into a pool a little less ?an two hundr$ feet 9 dep?4 ,"h ! =ce ( ! fall+ wat] is suffici5t to move ab\t ! fall5 blocks ( lime/one & use !m 9 ! excavation ( ! %ale ( ! b$4 ,at ! ,am]ican ,falls ! less] bran* ( ! riv]1 :i* fl[s along ! ,am]ican side ( ,goat ,isl&1 p\rs ov] ! side ( ! gorge & breaks ^u a high talus ( lime/one blocks :i* its small] volume ( wat] is unable to gr9d to pieces & remove4 ,a s]ies ( surveys h det]m9$ t f #ahdb to #ahij ! ,horse%oe ,falls retreat$ at ! rate ( #b4ah feet p] ye>1 :ile ! ,am]ican ,falls retreat$ at ! rate ( #j4fd feet 9 ! same p]iod4 ,we _c d\bt t ! same ag5cy :i* is n[ l5g!n+ ! gorge at ?is rapid rate has cut x back its entire l5g? ( sev5 miles4 ,:ile ,niag>a ,falls h be5 cutt+ back a gorge sev5 miles long & f two hundr$ to ?ree hundr$ feet deep1 ! riv] above ! ,falls has erod$ its b$ sc>cely bel[ ! level ( ! upl& on :i* x fl[s4 ,l all /reams :i* are ! outlets ( lakes1 ! ,niag>a fl[s out ( ,lake ,erie cle> ( s$im5t1 z f a settl+ bas91 & c>ries no tools ) :i* to abrade its b$4 ,we may inf] f ?is in/ance h[ slight is ! erosive p[] ( cle> wat] on h>d rock4 ,illu/ration3 ,fig4 #ci4 ,longitud9al ,section ( ,niag>a ,gorge ,black1 wat]2 ,f1 falls2 ,r1 rapids2 ,w1 :irlpool2 ,e1 esc>pm5t2 ,n1 nor?2 ,s1 s\? ,assum+ t ! rate ( recession ( ! comb9$ volumes ( ! ,am]ican & ,horse%oe ,falls 0 ?ree feet a ye> bel[ ,goat ,isl&1 & assum+ t ?is rate has be5 uni=m 9 ! pa/1 h[ long is x s9ce ! ,niag>a ,riv] fell ov] ! edge ( ! esc>pm5t :]e n[ is ! m\? ( ! pres5t gorge8 ,! pr(ile ( ! b$ ( ! ,niag>a along ! gorge 7,fig4 #ci7 %[s alt]nat+ deeps & %all[s :i* _c be acc\nt$ =1 except 9 a s+le in/ance1 by ! relative h>dness ( ! rocks ( ! riv] b$4 ,! deeps d n exce$ t at ! foot ( ! ,horse%oe ,falls at ! pres5t "t4 ,:5 ! gorge 0 be+ cut along ! %all[s1 h[ did ! ,falls comp>e 9 excavat+ p[]1 9 =ce1 & volume ) ! ,niag>a ( to-day8 ,h[ did ! rate ( recession at ^? times comp>e ) ! pres5t rate8 ,is ! assumption made above t ! rate ( recession has be5 uni=m correct8 ,! fir/ /ret* ( %all[s bel[ ! ,falls causes a tumultu\s rapid impossible to s\nd4 ,its dep? has be5 e/imat$ at ?irty-five feet4 ,f :at data c\ld su* an e/imate be made8 ,sugge/ a reason :y ! ,horse%oe ,falls are convex up/ream4 ,at ! pres5t rate ( recession :i* w rea* ! head ( ,goat ,isl& ! soon]1 ! ,am]ican or ! ,horse%oe ,falls8 ,:at w be ! fate ( ! ,falls left beh9d :5 ! o!r has pass$ beyond ! head ( ! isl&8 ,! rate at :i* a /ream erodes its b$ dep5ds 9 "p ^u ! nature ( ! rocks ov] :i* x fl[s4 ,w a /ream deep5 its *annel m rapidly on massive or on ?9-b$d$ & close-jo9t$ rocks8 on horizontal /rata or on /rata /eeply incl9$8 ,illu/ration3 ,fig4 #dj4 ,a ,/ream 9 ,scotl& ,9 :at ways is ! b$ n[ be+ deep5$8 ,deposition ,:ile ! riv] c>ries its invisible load ( dissolv$ rock on )\t /op to ! sea1 its load ( visible wa/e is subject to _m delays en r\te4 ,n[ & aga9 x is laid aside1 to be pick$ up lat] & c>ri$ "s di/ance f>!r on its way4 ,"o ( ! mo/ /rik+ features ( ! riv] !re=e is ! wa/e accumulat$ along its c\rse1 9 b>s & isl&s 9 ! *annel1 b5ea? its b$1 & 9 flood pla9s along its banks4 ,all ?is alluvium1 to use a g5]al t]m = riv] deposits1 ) :i* ! valley is cumb]$ is really en r\te to ! sea2 x is only tempor>ily laid aside to resume its j\rney lat] on4 ,con/antly ! riv] is de/roy+ & rebuild+ its alluvial deposits1 "h cutt+ & !re deposit+ along its banks1 "h erod+ & !re build+ a b>1 "h excavat+ its b$ & !re fill+ x up1 & at all times c>ry+ ! mat]ial pick$ up at "o po9t "s di/ance on d[n/ream be=e deposit+ x at ano!r4 ,illu/ration3 ,fig4 #da4 ,s& ,b> deposit$ by ,/ream1 %[+ ,cross ,b$d+ ,^! deposits are laid d[n by slack5+ curr5ts :]e ! velocity ( ! /ream is *eck$1 z on ! inn] side ( curves1 & :]e ! slope ( ! b$ is dim9i%$1 & 9 ! lee ( isl&s1 bridge pi]s & project+ po9ts ( l&4 ,h[ slight is ! *eck requir$ to cause a curr5t to drop a l>ge "p ( its load may be inf]r$ f ! law ( ! relation ( ! transport+ p[] to ! velocity4 ,if ! velocity is decreas$ "o half1 ! curr5t c move fragm5ts b "o sixty-f\r? ! size ( ^? :i* x c\ld move be=e1 & mu/ drop all ^? ( l>g] size4 ,w a riv] deposit m at l[ wat] or at flood8 :5 ris+ or :5 fall+8 ,/ratification4 ,riv] deposits are /ratifi$1 z may be se5 9 any fre% cut 9 banks or b>s4 ,! wa/e ( :i* !y are built has be5 sort$ & deposit$ 9 lay]s1 "o above ano!r2 "s ( f9] & "s ( co>s] mat]ial4 ,! sort+ action ( runn+ wat] dep5ds on ! fact t its transport+ p[] v>ies ) ! velocity4 ,a curr5t ^: dim9i%+ velocity compels x to drop co>se gravel1 = example1 is /ill able to move all ! f9] wa/e ( its load1 & sep>at+ x f ! gravel1 c>ries x on d[n/ream2 :ile at a lat] "t sl[] curr5ts may deposit on ! gravel b$ lay]s ( s&1 &1 /ill lat]1 slack wat] may leave on ^! a lay] ( mud4 ,9 case ( mat]ials light] ?an wat] ! transport+ p[] does n dep5d on ! velocity1 & logs ( wood1 = in/ance1 are float$ on to ! sea on ! sl[e/ z well z on ! mo/ rapid curr5ts4 ,illu/ration3 ,fig4 #db4 ,longitud9al ,section ( a ,riv] ,b> ,cross b$d+4 ,a section ( a b> expos$ at l[ wat] may %[ t x is =m$ ( lay]s ( s&1 or co>s] /uff1 incl9$ d[n/ream z /eeply (t5 z ! angle ( repose ( ! mat]ial4 ,f a boat an*or$ ov] ! l[] end ( a subm]g$ s& b> we may obs]ve ! way 9 :i* ?is /ructure1 call$ cross b$d+1 is produc$4 ,s& is cont9ually pu%$ ov] ! edge ( ! b> at b 7,fig4 #db7 & comes to re/ 9 successive lay]s on ! slop+ surface4 ,at ! same "t ! b> may be worn away at ! upp] end1 a1 & ?us sl[ly advance d[n /ream4 ,:ile ! deposit is ?us cross b$d$1 x con/itutes z a :ole a /ratum ^: upp] & l[] surfaces are ab\t horizontal4 ,9 sections ( riv] banks "o may (t5 see a v]tical succession ( cross-b$d$ /rata1 ea* built 9 ! way describ$4 ,wat] we>4 ,! co>s] mat]ial ( riv] deposits1 su* z cobble/ones1 gravel1 & ! l>g] gra9s ( s&1 are wat] worn1 or r\nd$1 except :5 ne> _! s\rce4 ,roll+ along ! bottom !y h be5 worn r\nd by impact & friction z !y rubb$ aga9/ "o ano!r & ! rocky b$ ( ! /ream4 ,exp]im5ts h %[n t angul> fragm5ts ( granite lose ne>ly half _! weight & become well r\nd$ aft] travel+ fifte5 miles 9 rotat+ cyl9d]s p>tly fill$ ) wat]4 ,m>bles are *eaply made 9 ,g]many out ( small lime/one cubes set revolv+ 9 a curr5t ( wat] betwe5 a rotat+ b$ ( /one & a block ( oak1 ! process requir+ b ab\t fifte5 m9utes4 ,x has be5 f\nd t 9 ! upp] rea*es ( m\nta9 /reams a desc5t ( less ?an a mile is suffici5t to r\nd pebbles ( granite4 ,illu/ration3 ,fig4 #dc4 ,wat]-,worn ,pebbles1 ,upp] ,potomac ,riv]1 ,m>yl& ,l& ,=ms ,due ,to ,riv] ,erosion ,riv] valleys4 ,9 _! c\rses to ! sea1 riv]s foll[ valleys ( v>i\s =ms1 "s %all[ & "s deep1 "s n>r[ & "s wide4 ,s9ce riv]s are kn[n to erode _! b$s & banks1 x is a fair presumption t1 aid$ by ! wea!r1 !y h excavat$ ! valleys 9 :i* !y fl[4 ,moreov]1 a bird's-eye view or a map ( a region %[s ! significant fact t ! valleys ( a sy/em unite ) "o ano!r 9 a bran* "w1 z twigs meet _! /ems & ! bran*es ( a tree its trunk4 ,ea* valley1 f t ( ! smalle/ rivulet to t ( ! ma/] /ream1 is proportionate to ! size ( ! /ream :i* occupies x4 ,) a few expla9able exceptions ! valleys ( tribut>ies jo9 t ( ! trunk /ream at a level2 !re is no sudd5 desc5t or break 9 ! b$ at ! po9t ( juncture4 ,^! are ! natural consequ5ces :i* mu/ foll[ if ! l& has long be5 work$ ^u by /reams1 & no o!r process has ev] be5 sugge/$ :i* is compet5t to produce !m4 ,we mu/ conclude t valley sy/ems h be5 =m$ by ! riv] sy/ems :i* dra9 !m1 aid$ by ! "w ( ! wea!r2 !y are n gap+ fissures 9 ! e>?'s cru/1 z e>ly obs]v]s imag9$1 b are ! furr[s :i* runn+ wat] has drawn ^u ! l&4 ,z valleys are made by ! sl[ we> ( /reams & ! action ( ! wea!r1 !y pass 9 _! developm5t ?r\gh successive /ages1 ea* ( :i* has its own *>act]i/ic features4 ,we may !re=e classify riv]s & valleys accord+ to ! /age :i* !y h rea*$ 9 _! life hi/ory f infancy to old age4 ,"y ,riv] ,valleys ,infancy4 ,! ,r$ ,riv] ( ! ,nor?4 ,a region 9 nor?we/]n ,m9nesota & ! adjac5t portions ( ,nor? ,dakota & ,manitoba 0 s rec5tly cov]$ by ! wat]s ( an ext9ct lake1 kn[n z ,lake ,agassiz1 t ! surface rema9s mu* z x 0 left :5 ! lake 0 dra9$ away4 ,! flat floor1 spread smoo? ) lake-laid silts1 is /ill a pla91 to ! eye z level z ! sea4 ,across x ! ,r$ ,riv] ( ! ,nor? & its bran*es run 9 n>r[1 dit*-l *annels1 /eep-sid$ & %all[1 n exce$+ sixty feet 9 dep?1 _! gradi5ts diff]+ little f ! g5]al slopes ( ! region4 ,! trunk /reams h b few tribut>ies2 ! riv] sy/em1 l a sapl+ ) few limbs1 is /ill undevelop$4 ,along ! banks ( ! trunk /reams %ort gullies are sl[ly l5g!n+ headw>ds1 l gr[+ twigs :i* are sometime to become l>ge bran*es4 ,illu/ration3 ,fig4 #dd4 ,a ,"y ,lacu/r9e ,pla92 ! ,r$ ,riv] ( ! ,nor? ,scale #e in*es ab\t #aa miles4 ,cont\r int]val1 #bj feet ,! flat int]/ream areas are z yet b little scor$ by dra9age l9es1 & 9 wet wea!r wat] l+]s 9 ponds 9 any initial depressions on ! pla94 ,illu/ration3 ,fig4 #de4 ,a ,"y ,riv]1 ,i[a ,note t x has h>dly begun to cut 9 ! pla9 ( glacial drift on :i* x fl[s ,cont\rs4 ,9 ord] to read ! topographic maps ( ! text-book & ! laboratory ! /ud5t %\ld "k t cont\rs are l9es drawn on maps to repres5t relief1 all po9ts on any giv5 cont\r be+ ( equal height above sea level4 ,! cont\r int]val is ! uni=m v]tical di/ance betwe5 two adjac5t cont\rs & v>ies on diff]5t maps4 ,to express regions ( fa9t relief a cont\r int]val ( t5 or tw5ty feet is commonly select$2 :ile 9 m\nta9\s regions a cont\r int]val ( two hundr$ & fifty1 five hundr$1 or ev5 "o ?\s& feet may be necess>y 9 ord] t ! cont\rs may n be too cr[d$ = easy read+4 ,:e!r a riv] beg9s its life on a lake pla91 z 9 ! example j cit$1 or ^u a coa/al pla9 lift$ f b5ea? ! sea or on a spread ( glacial drift left by ! retreat ( cont95tal ice %eets1 su* z cov]s mu* ( ,canada & ! nor!a/]n p>ts ( ! ,unit$ ,/ates1 its infantile /age pres5ts ! same *>act]i/ic features1--a n>r[ & %all[ valley1 ) undevelop$ tribut>ies & undra9$ int]/ream areas4 ,gr\nd wat] /&s high1 &1 exud+ 9 ! undra9$ initial depressions1 =ms m>%es & lakes4 ,illu/ration3 ,fig4 #df4 ,a ,"y ,drift ,region 9 ,wiscons9 ,describe ?is area4 ,h[ high are ! hills8 ,are !y su* 9 =m & position z w\ld be left by /ream erosion8 ,consult a map ( ! entire /ate & notice t ! ,fox ,riv] f9ds its way to ,lake ,mi*igan1 :ile ! ,wiscons9 empties into ! ,mississippi4 ,describe t portion ( ! divide "h %[n betwe5 ! ,mississippi & ! ,/4 ,lawr5ce sy/ems4 ,:i* is ! l>g] riv]1 ! ,wiscons9 or ! ,fox8 ,o!r ?+s be+ equal1 :i* may be expect$ to deep5 its b$ ! m rapidly8 ,:at *anges are likely to occur :5 "o ( ^! riv]s comes to fl[ at a l[] level ?an ! o!r8 ,:y h n ^! *anges occurr$ already8 ,lakes4 ,lakes are p]haps ! mo/ obvi\s ( ^! fleet+ features ( infancy4 ,!y are %ort-liv$1 = _! de/ruction is soon accompli%$ by sev]al means4 ,z a riv] sy/em advances t[>d maturity ! deep5+ & ext5d+ valleys ( ! tribut>ies l[] ! gr\nd-wat] surface & invade ! undra9$ depressions ( ! region4 ,lakes hav+ outlets are dra9$ away z _! bas9 rims are cut d[n by ! outfl[+ /reams1--a sl[ process :]e ! rim is ( h>d rock1 b a rapid "o :]e x is ( s(t mat]ial su* z glacial drift4 ,lakes are effac$ also by ! fill+ ( _! bas9s4 ,infl[+ /reams & ! wa% ( ra9s br+ 9 wa/e4 ,waves abrade ! %ore & /rew ! dbris worn f x ov] ! lake b$4 ,%all[ lakes are (t5 fill$ ) organic matt] f decay+ vegetation4 ,does ! outfl[+ /ream1 f a lake c>ry s$im5t8 ,h[ does ?is fact affect its erosive p[] on h>d rock8 on loose mat]ial8 ,lake ,g5eva is a well-kn[n example ( a lake 9 process ( oblit]ation4 ,! infl[+ ,rhone has already displac$ ! wat]s ( ! lake = a l5g? ( tw5ty miles ) ! wa/e br\ght d[n f ! high ,alps4 ,= ?is di/ance !re ext5ds up ! ,rhone ,valley an alluvial pla91 :i* has gr[n lakew>d at ! rate ( a mile & a half s9ce ,roman times1 z prov$ by ! di/ance inl& at :i* a ,roman port n[ /&s4 ,illu/ration3 ,fig4 #dg4 ,a ,small ,lake be+ broad5$ & %oal$ by ,wave ,we> ls1 lake surface2 dott$ l9e1 initial %ore2 b1 fill made ( mat]ial tak5 f a ,h[ rapidly a lake may be silt$ up "u exceptionally favorable conditions is illu/rat$ by ! fact t ov] ! bottom ( ! artificial lake1 ( ?irty-five squ>e miles1 =m$ beh9d ! great dam across ! ,colorado ,riv] at ,au/91 ,texas1 s$im5ts ?irty-n9e feet deep ga!r$ 9 sev5 ye>s4 ,lake ,m5dota1 "o ( ! _m beautiful lakes ( s\!rn ,wiscons91 is rapidly cutt+ back ! s(t glacial drift ( its %ores by means ( ! abrasion ( its waves4 ,:ile ! %all[ bas9 is ?us broad5$1 x is also be+ fill$ ) ! wa/e2 & ! "t is br\ght ne>] :5 x w be s %oal$ t vegetation c complete ! "w ( its effacem5t4 ,illu/ration3 ,fig4 #dh4 ,a ,lake well-nigh effac$1 ,montana ,by :at means is ! lake b$ be+ fill$8 ,along ! m>g9 ( a %all[ lake mosses1 wat] lilies1 grasses1 & o!r wat]-lov+ plants gr[ luxuriantly4 ,z _! decay+ rema9s accumulate on ! bottom1 ! r+ ( m>% broad5s inw>ds1 ! lake n>r[s gradually to a small pond set 9 ! mid/ ( a wide bog1 & f9ally disappe>s4 ,all /ages 9 ?is process ( ext9ction may be se5 among ! c\ntless lakelets :i* occupy sags 9 ! rec5t %eets ( glacial drift 9 ! nor!rn /ates2 & m num]\s ?an ! lakes :i* /ill rema9 are ^? already ?us fill$ ) c>bonace\s matt] d]iv$ f ! c>bon dioxide ( ! atmosph]e4 ,su* fossil lakes are m>k$ by swamps or level mead[s und]la9 ) muck4 ,illu/ration3 ,fig4 #di4 ,a ,level ,mead[1 ,scotl& ,expla9 its orig94 ,:at w be its future8 ,! advance to maturity4 ,! infantile /age is brief4 ,z a riv] advances t[>d maturity ! initial depressions1 ! lake bas9s ( its area1 are gradually effac$4 ,by ! furr[+ action ( ! ra9 wa% & ! head w>d l5g!n+1 ( tribut>ies a bran*work ( dra9age *annels gr[s until x cov]s ! entire area1 & n an acre is left on :i* ! fall5 ra9drop does n f9d already cut = x an un9t]rupt$ d[nw>d pa? :i* leads x on by way ( gully1 brook1 & riv] to ! sea4 ,! initial surface ( ! l&1 by :atev] ag5cy x 0 model$1 is n[ :olly de/roy$2 ! region is all r$uc$ to valley slopes4 ,illu/ration3 ,fig4 #ej4 ,dra9age ,maps ,a1 an area 9 its infancy1 ,bu5a ,vi/a ,c\nty1 ,i[a2 ,b1 an area 9 its maturity1 ,r+gold ,c\nty1 ,i[a ,illu/ration3 ,fig4 #ea4 ,successive ,longitud9al ,pr(iles ( a ,/ream am1 initial pr(ile1 ) wat]fall at w1 & bas9s at l & l1 :i* at fir/ are occupi$ by lakes & lat] are fill$ or dra9$2 b1 c1 d1 & e1 pr(iles e/abli%$ 9 succession z ! /ream advances f infancy t[>d old age4 ,note t ^! pr(iles are concave t[>d ! sky4 ,?is is ! erosion curve4 ,:at contra/+ =m has ! wea!r wea!r curve 7p4 #cd78 ,! longitud9al pr(ile ( a /ream4 ,?is at fir/ corresponds ) ! initial surface ( ! region on :i* ! /ream beg9s to fl[1 al?\gh its way may lead ?r\gh bas9s & d[n /eep desc5ts4 ,! successive pr(iles to :i* x r$uces its b$ are illu/rat$ 9 ,figure #ea4 ,z ! gradi5t1 or rate ( desc5t ( its b$1 is l[]$1 ! velocity ( ! riv] is decreas$ until its less5+ en]gy is :olly consum$ 9 c>ry+ its load & x c no long] erode its b$4 ,! riv] is n[ at grade1 & its capacity is j equal to its load4 ,if n[ its load is increas$ ! /ream deposits1 & ?us builds up1 or aggrades1 its b$4 ,on ! o!r h&1 if its load is dim9i%$ x has en]gy to sp>e1 & resum+ its "w ( erosion1 degrades its b$4 ,9 ei!r case ! /ream cont9ues aggrad+ or degrad+ until a new gradi5t is f\nd :]e ! velocity is j suffici5t to move ! load1 & "h aga9 x rea*es grade4 ,illu/ration3 ,fig4 #eb4 ,a ,v-,valley1--! ,canyon ( ! ,yell[/one ,note ! /eep sides4 ,:at processes are at "w ^u !m8 ,h[ wide is ! valley at ! base comp>$ ) ! wid? ( ! /ream8 ,d y see any riv] deposits along ! banks8 ,is ! /ream fl[+ swiftly ov] a rock b$1 or quietly ov] a b$ :i* x has built up8 ,is x grad$ or ungrad$8 ,note t ! canyon walls project 9 int]lock+ spurs ,v-,valleys4 ,vigor\s riv]s well arm$ ) wa/e make %ort "w ( cutt+ _! b$s to grade1 & ?us erode n>r[1 /eep-sid$ gorges only wide en\gh at ! base to accommodate ! /ream4 ,! /eepness ( ! valley slopes dep5ds on ! relative rates at :i* ! b$ is cut d[n by ! /ream & ! sides are worn back by ! wea!r4 ,9 resi/ant rock a swift1 well-lad5 /ream may saw out a gorge ^: sides are ne>ly or ev5 q v]tical1 b z a rule "y valleys ^: /reams h n yet rea*$ grade are ,v-%ap$2 _! sides fl>e at ! top because "h ! rocks h longe/ be5 op5$ up to ! action ( ! wea!r4 ,"s ( ! deepe/ canyons may be f\nd :]e a ris+ l& mass1 ei!r m\nta9 range or plateau1 has long ma9ta9$ by its cont9u$ uplift ! riv]s ( ! region above grade4 ,illu/ration3 ,fig4 #ec4 ,section ( ! ,yell[/one ,canyon ,?is canyon is #ajj feet deep1 #bejj feet wide at ! top1 & ab\t #bej feet wide at ! bottom4 ,neglect+ any cutt+ ( ! riv] aga9/ ! banks1 e/imate :at "p ( ! excavation ( ! canyon is due to ! v]tical erosion ( its b$ by ! riv] & :at to wea!r+ & ra9 wa% on ! canyon sides ,9 ! nor!rn hemisph]e ! nor? sides ( riv] valleys are sometimes ( m g5tle slope ?an ! s\? sides4 ,c y sugge/ a reason8 ,! ,gr& ,canyon ( ! ,colorado ,riv] 9 ,arizona4 ,! ,colorado ,riv] tr5*es ! high plateau ( nor!rn ,arizona ) a colossal canyon two hundr$ & eighte5 miles long & m ?an a mile 9 greate/ dep? 7,fig4 #ae74 ,! rocks 9 :i* ! canyon is cut are = ! mo/ "p flat-ly+1 massive b$s ( lime/ones & s&/ones1 ) "s %ales1 b5ea? :i* 9 places h>d] cry/all9e rocks are disclos$4 ,:]e ! canyon is deepe/ its walls h be5 pr(\ndly dissect$4 ,lat]al rav9es h wid5$ into imm5se amphi!at]s1 leav+ betwe5 !m long ridges ( m\nta9 height1 buttress$ & rebuttress$ ) flank+ spurs & c>v$ into maje/ic ar*itectural =ms4 ,f ! extremity ( "o ( ^! promontories x is two miles or m across ! gulf to ! po9t ( ! "o opposite1 & ! heads ( ! amphi!at]s are ?irte5 miles ap>t4 ,illu/ration3 ,fig4 #ed4 ,gr& ,canyon ( ! ,colorado ,riv]1 ,arizona ,! l[] portion ( ! canyon is mu* n>r[] 7,fig4 #ed7 & its walls ( d>k cry/all9e rock s9k /eeply to ! edge ( ! riv]1 a swift1 p[]ful /ream a few hundr$ feet wide1 turbid ) r$di% silt1 by means ( :i* x cont9ually rasps its rocky b$ z x hurries on4 ,! ,colorado is /ill deep5+ its gorge4 ,9 ! ,gr& ,canyon its gradi5t is sev5 & "o half feet to ! mile1 b1 z 9 all ungrad$ riv]s1 ! desc5t is f> f uni=m4 ,grad$ rea*es 9 s(t rock alt]nate ) /eep] declivities 9 h>d rock1 =m+ rapids su* z1 = example1 a /ret* ( t5 miles :]e ! fall av]ages tw5ty-"o feet to ! mile4 ,because ( ^! dang]\s rapids ! few explor+ p>ties :o h trav]s$ ! ,colorado canyon h done s at ! haz>d ( _! lives4 ,! canyon has be5 %ap$ by sev]al ag5cies4 ,its dep? is due to ! riv] :i* has saw$ its way f> t[>d ! base ( a l(ty ris+ plateau4 ,act+ alone ?is w\ld h produc$ a slitlike gorge little wid] ?an ! bread? ( ! /ream4 ,! impressive wid? ( ! canyon & ! magnific5t ar*itectural masses :i* fill x are ow+ to two causes4 ,runn+ wat] has gul*$ ! walls & wea!r+ has ev]y:]e attack$ & driv5 !m back4 ,! horizontal h>d] b$s /& out 9 long l9es ( v]tical cliffs1 (t5 hundr$s ( feet 9 height1 at ^: feet talus slopes conceal ! outcrop ( ! weak] /rata 7,fig4 #ae74 ,z ! upp] cliffs h be5 sapp$ & driv5 back by ! wea!r1 broad plat=ms are left at _! bases & ! sides ( ! canyon desc5d to ! riv] by gigantic /eps4 ,f> up & d[n ! canyon ! eye traces ^! horizontal lay]s1 l ! flut+s ( an elaborate mold+1 di/+ui%+ ea* by its cont\r z well z by its color & ?ickness4 ,illu/ration3 ,fig4 #ee4 ,diagrams illu/rat+ ,conditions :i* produce ,falls or ,rapids ,a1 v]tical succession ( h>d] & s(t] rocks2 ,b1 horizontal succession ( ! same4 ,9 ,a ! /ream ab 9 s9k+ its b$ ?r\gh a mass ( /rata ( diff]5t degrees ( h>dness has discov]$ ! weak lay] s b5ea? ! h>d lay] h4 ,x rapidly cuts its way 9 s1 :ile 9 ,a its "w is delay$4 ,?us ! pr(ile afb is soon rea*$1 ) falls at f4 ,9 ,b ! initial pr(ile is %[n by dott$ l9e4 ,! ,gr& ,canyon ( ! ,colorado is (t5 & rightly cit$ z an example ( ! /up5d\s erosion :i* may be accompli%$ by a riv]4 ,& yet ! ,colorado is a "y /ream & its "w is no m ?an well begun4 ,x has n yet :olly rea*$ grade1 & ! great task ( ! riv] & its tribut>ies--! task ( level+ ! l(ty plateau to a l[ pla9 & ( transport+ x gra9 by gra9 to ! sea--/ill lies almo/ entirely 9 ! future4 ,illu/ration3 ,fig4 #ef4 ,longitud9al ,section ( ,yell[/one ,riv] at ,l[] ,fall1 ,f1 & ,upp] ,fall1 ,f1 ,yell[/one ,national ,p>k la1 lava deeply decay$ ?r\gh action ( !rmal wat]s2 m & m1 masses ( decay$ lavas to ^: h>dness ! falls are due4 ,:i* fall w be worn away ! soon]8 ,h[ f> up/ream w ea* fall migrate8 ,draw pr(ile ( ! riv] :5 "o fall has disappe>$ ,illu/ration3 ,fig4 #eg4 ,diagram illu/rat+ ,migration ( a ,fall due to a ,h>d ,lay] ,h1 9 ! ,mid/ ( ,s(t ,lay]s ,s & ,s1 all dipp+ up/ream a1 b1 c1 d1 & e1 successive positions ( ! fall2 r1 rapid to :i* ! fall is r$uc$4 ,draw diagram %[+ migration ( fall 9 /rata dipp+ d[n/ream4 ,"u :at conditions ( incl9ation ( ! /rata w a fall migrate ! f>!/ & h ! longe/ life8 ,"u :at conditions w x migrate ! lea/ di/ance & soone/ be de/roy$8 ,wat]falls & rapids4 ,be=e ! b$ ( a /ream is r$uc$ to grade x may be brok5 by abrupt desc5ts :i* give rise to wat]falls & rapids4 ,su* breaks 9 a riv]'s b$ may belong to ! initial surface ov] :i* x began its c\rse2 /ill m commonly are !y develop$ 9 ! rock mass ?r\gh :i* x is cutt+ its valley4 ,?us1 :]ev] a /ream leaves h>d] rocks to fl[ ov] s(t] ones ! latt] are quickly worn bel[ ! level ( ! =m]1 & a %>p *ange 9 slope1 ) a wat]fall or rapid1 results4 ,at "t ( flood "y tribut>ies ) /eep] c\rses ?an t ( ! trunk /ream may br+ d[n /ones & f9] wa/e1 :i* ! g5tl] curr5t _c move along1 & ?r[ !m z a dam across its way4 ,! rapids ?us =m$ are also ephem]al1 = z ! gradi5t ( ! tribut>ies is l[]$ ! ma9 /ream becomes able to h&le ! small] & f9] load :i* !y dis*>ge4 ,a r>e class ( falls is produc$ :]e ! m9or tribut>ies ( a "y riv] are n able to keep pace ) _! ma/] /ream 9 ! erosion ( _! b$s because ( _! small] volume1 & ?us jo9 x by plung+ ov] ! side ( its gorge4 ,b z ! riv] approa*es grade & slack5s its d[n cutt+1 ! tribut>ies soon] or lat] ov]take x1 & effac+ _! falls1 unite ) x on a level4 ,illu/ration3 ,fig4 #eh4 ,maturely ,dissect$ ,plateau ne> ,*>le/on1 ,we/ ,virg9ia ,comp>e ! numb] ( /reams 9 any giv5 numb] ( squ>e miles ) ! numb] on an area ( ! same size 9 ! ,r$ ,riv] ,valley 7,fig4 #dd74 ,:at is ! %ape ( ! ridges8 ,are _! summits broad or n>r[8 ,are _! cre/s ev5 or brok5 by knobs & cols 7! depressions on ! cre/ l9e78 ,if ! latt]1 h[ deeply h ! cols be5 worn b5ea? ! summits ( ! knobs8 ,wat]falls & rapids ( all k9ds are evanesc5t features ( a riv]'s y\?4 ,l lakes !y are soon de/roy$1 & if any long "t _h already elaps$ s9ce _! =mation !y w\ld h be5 oblit]at$ already4 ,local baselevels4 ,t balanc$ condition call$ grade1 :]e a riv] nei!r degrades its b$ by erosion nor aggrades x by deposition1 is fir/ atta9$ along rea*es ( s(t rocks1 ungrad$ outcrops ( h>d rocks rema9+ z b>ri]s :i* give rise to rapids or falls4 ,until ^! b>ri]s are worn away !y con/itute local baselevels1 bel[ :i* level ! /ream1 up valley f !m1 _c cut4 ,!y are erod$ to grade "o aft] ano!r1 beg9n+ ) ! lea/ /rong1 or ! "o ne>e/ ! m\? ( ! /ream4 ,9 a simil> way ! surface ( a lake 9 a riv]'s c\rse con/itutes = all infl[+ /reams a local baselevel1 :i* disappe>s :5 ! bas9 is fill$ or dra9$4 ,illu/ration3 ,fig4 #ei4 ,a ,maturity ,dissect$ ,region ( ,slight ,relief1 ,i[a ,mature ,& ,old ,riv]s ,maturity is ! /age ( a riv]'s complete developm5t & mo/ effective "w4 ,! riv] sy/em n[ has well "u way its great task ( we>+ d[n ! l& mass :i* x dra9s & c>ry+ x p>ticle by p>ticle to ! sea4 ,! relief ( ! l& is n[ at its greate/2 = ! ma9 *annels h be5 sunk to grade1 :ile ! divides rema9 b little worn bel[ _! initial altitudes4 ,gr\nd wat] n[ /&s l[4 ,! run-(f wa%es directly to ! /reams1 ) ! lea/ delay & loss by evaporation 9 ponds & m>*es2 ! dis*>ge ( ! riv] is !re=e at its height4 ,! entire region is dissect$ by /ream ways4 ,! area ( valley slopes is n[ l>ge/ & %$s to ! /reams a heavi] load ( wa/e ?an ev] be=e4 ,at maturity ! riv] sy/em is do+ its greate/ am\nt ( "w bo? 9 erosion & 9 ! c>riage ( wat] & ( wa/e to ! sea4 ,illu/ration3 ,fig4 #fj4 ,successive ,/ages1 ,a1 ,b1 ,c1 & ,d1 9 ,valley-,wid5+ by ,planation ,describe valley ,a4 ,:at *anges h tak5 place 9 ,b1 ,c1 & ,d8 ,d ! riv] b5ds rema9 /ation>y or move up or d[n valley8 ,) :at effect on ! project+ spurs ( ! valley sides8 ,draw diagrams %[+ a /ill lat] /age ?an ,d ,lat]al erosion4 ,on rea*+ grade a riv] ceases to sc\r its b$1 & x does n aga9 beg9 to d s until "s *ange 9 load or volume enables x to f9d grade at a l[] level4 ,on ! o!r h&1 a /ream erodes its banks at all /ages 9 its hi/ory1 & ) grad$ riv]s ?is process1 call$ lat]al erosion1 or planation1 is specially important4 ,! curr5t ( a /ream foll[s ! out] side ( all curves or b5ds 9 ! *annel1 & on ?is side x excavates its b$ ! deepe/ & cont9ually we>s & saps its banks4 ,on ! inn] side deposition takes place 9 ! m %all[ & sl[]-mov+ wat]4 ,! inn] bank ( b5ds is ?us built out :ile ! out] bank is worn away4 ,by sw++ its curves aga9/ ! valley sides a grad$ riv] cont9ually cuts a wid] & wid] floor4 ,! ,v-valley ( y\? is ?us *ang$ by planation to a flat-floor$ valley ) fl>+ sides :i* gradually become subdu$ by ! wea!r to g5tle slopes4 ,:ile wid5+ _! valleys /reams ma9ta9 a con/ant wid? ( *annel1 s t a wide-floor$ valley does n signify t x ev] 0 occupi$ by a riv] ( equal wid?4 ,! gradi5t4 ,! gradi5ts ( grad$ riv]s diff] widely4 ,a l>ge riv] ) a light load rea*es grade on a fa9t slope1 :ile a small] /ream heavily burd5$ ) wa/e requires a /eep slope to give x velocity suffici5t to move ! load4 ,! ,platte1 a grad$ riv] ( ,nebraska ) its headwat]s 9 ! ,rocky ,m\nta9s1 is enfeebl$ by ! semi-arid climate ( ! ,great ,pla9s & sur*>g$ ) ! wa/e br\ght d[n bo? by its bran*es 9 ! m\nta9s & by ^? ^: tracks lie ov] ! s(t rocks ( ! pla9s4 ,x is compell$ to ma9ta9 a gradi5t ( eight feet to ! mile 9 we/]n ,nebraska4 ,! ,ohio rea*es grade ) a slope ( less ?an f\r in*es to ! mile f ,c9c9nati to its m\?1 & ! p[]ful ,mississippi wa%es along its load ) a fall ( b ?ree in*es p] mile f ,cairo to ! ,gulf4 ,o!r ?+s be+ equal1 :i* ( grad$ /reams w h ! /eep] gradi5t1 a trunk /ream or its tribut>ies8 a /ream suppli$ ) gravel or "o ) silt8 ,o!r factors rema9+ ! same1 :at *anges w\ld occur if ! ,platte %\ld increase 9 volume8 ,:at *anges w\ld occur if ! load %\ld be increas$ 9 am\nt or 9 co>s5ess8 ,illu/ration3 ,fig4 #fa4 ,successive ,cross ,sections ( a ,region z x advances f ,infancy a1 to ,old ,age e ,! old age ( riv]s4 ,z riv]s pass _! prime1 z d5udation l[]s ! relief ( ! region1 less wa/e & f9] is wa%$ ov] ! g5tl] slopes ( ! l[]+ hills4 ,) small] loads to c>ry1 ! riv]s n[ deep5 _! valleys & f9d grade ) fa9t] declivities ne>] ! level ( ! sea4 ,?is limit ( ! level ( ! sea b5ea? :i* !y _c erode is kn[n z baselevel4#a ,z /reams gr[ old !y approa* m & m closely to baselevel1 al?\gh !y are nev] able to atta9 x4 ,"s slight slope is ne$$ t wat] may fl[ & wa/e be transport$ ov] ! l&4 ,mean:ile ! relief ( ! l& has ev] less5$4 ,! ma/] /reams & _! ma9 tribut>ies n[ w&] ) sluggi% curr5ts ov] ! broad valley floors :i* !y h plan$ away2 :ile "u ! erosion ( _! innum]able bran*es & ! we> ( ! wea!r ! divides ev]y:]e are l[]$ & subdu$ to m & m g5tle slopes4 ,m\nta9s & high plateaus are ?us r$uc$ to roll+ hills1 & at la/ to pla9s1 surm\nt$ only by su* hills z may /ill be unr$uc$ to ! common level1 because ( ! h>d] rocks ( :i* !y are compos$ or because ( _! di/ance f ! ma9 erosion *annels4 ,su* regions ( fa9t relief1 worn d[n to ne> base level by subarial ag5cies1 are kn[n z p5epla9s 7almo/ pla9s74 ,any residual masses :i* rise above !m are call$ monadnocks1 f ! "n ( a conical peak ( ,new ,hamp%ire :i* ov]looks ! n[ uplift$ p5epla9 ( s\!rn ,new ,engl&4 #a ,! t]m baselevel is also us$ to designate ! close approximation to sea level to :i* /reams are able to subdue ! l&4 ,9 its old age a region becomes mantl$ ) ?ick %eets ( f9e & wea!r$ wa/e1 sl[ly mov+ ov] ! fa9t slopes t[>d ! wat] ways & unbrok5 by l$ges ( b>e rock4 ,9 o!r words1 ! wa/e mantle also is n[ grad$1 & z wat]falls h be5 effac$ 9 ! riv] b$s1 s n[ any l$ges 9 ! wide /reams ( wa/e are worn away & cov]$ b5ea? smoo? slopes ( f9e soil4 ,gr\nd wat] /&s high & may exude 9 areas ( swamp4 ,9 y\? ! l& mass 0 r\ghhewn & cut deep by /ream erosion4 ,9 old age ! fa9t reliefs ( ! l& dissolve away1 *iefly "u ! action ( ! wea!r1 b5ea? _! cloak ( wa/e4 ,illu/ration3 ,fig4 #fb4 ,p5epla9 surr\nd$ by ,monadnocks1 ,pi$mont ,belt1 ,virg9ia ,f ,davis' ,elem5t>y ,physical ,geography ,! cycle ( erosion4 ,! successive /ages ?r\gh :i* a l& mass passes :ile x is be+ level$ to ! sea con/itute toge!r a cycle ( erosion4 ,ea* /age ( ! cycle f infancy to old age leaves1 z we h se51 its *>act]i/ic records 9 ! =ms sculptur$ on ! l&1 su* z ! %apes ( valleys & ! cont\rs ( hills & pla9s4 ,! geologi/ is ?us able to det]m9e by ! l& =ms ( any region ! /age 9 ! erosion cycle to :i* x n[ belongs1 & kn[+ :at are ! e>li] /ages ( ! cycle1 to read some?+ ( ! geological hi/ory ( ! region4 ,int]rupt$ cycles4 ,s long a "t is ne$$ to r$uce a l& mass to baselevel t ! process is seldom if ev] complet$ dur+ a s+le un9t]rupt$ cycle ( erosion4 ,( all ! v>i\s int]ruptions :i* may occur ! mo/ important are gradual movem5ts ( ! e>?'s cru/1 by :i* a region is ei!r depress$ or elevat$ relative to sea level4 ,illu/ration3 ,fig4 #fc4 ,"y ,inn] ,gorge 9 ,wide ,old] ,valley1 ,alaska ,! depression ( a region ha/5s its old age by decreas+ ! gradi5t ( /reams1 by de/roy+ _! p[] to excavate _! b$s & c>ry _! loads to a degree correspond+ to ! am\nt ( ! depression1 & by less5+ ! am\nt ( "w !y h to d4 ,! slack5$ riv] curr5ts deposit _! wa/e 9 ,hood pla9s :i* increase 9 height z ! subsid5ce cont9ues4 ,! l[] c\rses ( ! riv]s are invad$ by ! sea & become e/u>ies1 :ile ! l[] tribut>ies are cut (f f ! trunk /ream4 ,elevation1 on ! o!r h&1 increases ! activity ( all ag5cies ( wea!r+1 erosion1 & transportation1 re/ores ! region to its y\?1 & inaugurates a new cycle ( erosion4 ,/reams are giv5 a /eep] gradi5t1 great] velocity1 & increas$ en]gy to c>ry _! loads & we> _! b$s4 ,!y cut ?r\gh ! alluvium ( _! flood pla9s1 leav+ x on ei!r bank z successive t]races1 & intr5* !mselves 9 ! und]ly+ rock4 ,9 _! old] & wid] valleys !y cut n>r[1 /eep-wall$ inn] gorges1 9 :i* !y fl[ swiftly ov] rocky floors1 brok5 "h & !re by falls & rapids :]e a h>d] lay] ( rock has be5 discov]$4 ,w9d+ /reams on pla9s may ?us incise _! me&]s 9 solid rock z ! pla9s are gradually uplift$4 ,/reams :i* are ?us re/or$ to _! y\? are said to be reviv$4 ,illu/ration3 ,fig4 #fd4 ,incis$ ,me&]s ( ,oneota ,riv]1 ,i[a ,z /reams cut deep] & ! valley slopes are /eep5$1 ! mantle ( wa/e ( ! region und]go+ elevation is set 9 m rapid movem5t4 ,x is n[ remov$ p>ticle by p>ticle fa/] ?an x =ms4 ,z ! wa/e mantle ?9s1 wea!r+ attacks ! rocks ( ! region m en]getically until an equilibrium is rea*$ aga92 ! rocks wa/e rapidly & _! wa/e is z rapidly remov$4 ,dissect$ p5epla9s4 ,:5 a rise ( ! l& br+s "o cycle to an end & beg9s ano!r1 ! *>act]i/ic l& =ms ( ea* cycle are f\nd toge!r & ! topography ( ! region is composite until ! second cycle is s f> advanc$ t ! l& =ms ( ! fir/ cycle are entirely de/roy$4 ,! contra/ betwe5 ! l& surfaces ( ! lat] & ! e>li] cycles is mo/ /rik+ :5 ! e>li] _h advanc$ to age & ! lat] is /ill 9 y\?4 ,?us _m p5epla9s :i* h be5 elevat$ & dissect$ h be5 recogniz$ by ! remnants ( _! anci5t erosion surfaces1 & ! l5g? ( "t :i* has elaps$ s9ce _! uplift has be5 measur$ by ! /age to :i* ! new cycle has advanc$4 ,illu/ration3 ,fig4 #fe4 ,describe ! valley ( /ream a4 ,is x "y or old8 ,h[ does ! valley ( b diff] f t ( a8 ,comp>e z to =m & age ! inn] valley ( b ) ! out] valley & ) ! valley ( a4 ,acc\nt = ! inn] valley4 ,:y does x n ext5d to ! upp] portion ( ! c\rse ( b8 ,w x ev] d s8 ,draw longitud9al pr(ile ( b1 %[+ ! diff]5t gradi5t ( upp] & l[] portions ( its c\rse n "h se54 ,z ! inn] valley ( tribut>y c ext5ds headw>d x may invade ! valley ( a be=e ! inn] valley ( a has work$ up/ream to ! area se5 9 ! diagram4 ,) :at results8 ,! ,pi$mont ,belt4 ,z an example ( an anci5t p5epla9 uplift$ & dissect$ we may cite ! ,pi$mont ,belt1 a broad upl& ly+ betwe5 ! ,appala*ian ,m\nta9s & ! ,atlantic coa/al pla94 ,! surface ( ! ,pi$mont is g5tly roll+4 ,! divides1 :i* are (t5 smoo? areas ( consid]able wid?1 rise to a common plane1 & f !m "o sees 9 e direction an ev5 sky l9e except :]e 9 places "s lone hill or ridge may lift itself above ! g5]al level 7,fig4 #fb74 ,! surface is an anci5t "o1 = ! mantle ( residual wa/e lies deep ^u x1 soils are r$d5$ by long oxidation1 & ! rocks are rott$ to a dep? ( scores ( feet4 ,at pres5t1 h[ev]1 ! wa/e mantle is n =m+ s rapidly z x is be+ remov$4 ,! /reams ( ! upl& are actively engag$ 9 its de/ruction4 ,!y fl[ swiftly 9 n>r[1 rock-wall$ valleys ov] rocky b$s4 ,?is contra/ betwe5 ! "y /reams & ! ag$ surface :i* !y are n[ s vigor\sly dissect+ c only be expla9$ by ! !ory t ! region once /ood l[] ?an at pres5t & has rec5tly be5 uprais$4 ,if n[ we imag9e ! valleys refill$ ) ! wa/e :i* ! /reams h swept away1 & ! upl& l[]$1 we re/ore ! ,pi$mont region to ! condition 9 :i* x /ood be=e its uplift & dissection1--a g5tly roll+ pla91 surm\nt$ "h & !re by isolat$ hills & ridges4 ,illu/ration3 ,fig4 #ff4 ,dissect$ ,p5epla9 ( ,s\!rn ,new ,engl& ,! surface ( ! anci5t ,pi$mont pla91 z x may be re/or$ f ! remnants ( x f\nd on ! divides1 is n 9 accordance ) ! /ructures ( ! c\ntry rocks4 ,:]e ^! are expos$ to view !y are se5 to be f> f horizontal4 ,on ! walls ( riv] gorges !y dip /eeply & 9 v>i\s directions & ! /reams fl[ ov] _! upturn$ edges4 ,z %[n 9 ,figure #fg1 ! rocks ( ! ,pi$mont h be5 fold$ & brok5 & tilt$4 ,illu/ration3 ,fig4 #fg4 ,section 9 ,pi$mont ,belt ,m1 a monadnock ,x is n reasonable to believe t :5 ! rocks ( ! ,pi$mont 7 ?us fold$ & o!rwise de=m$ ! surface ( ! region 0 a pla94 ,! upturn$ lay]s h n always /opp$ abruptly at ! ev5 surface ( ! ,pi$mont pla9 :i* n[ cuts across !m4 ,!y are ! bases ( great folds & tilt$ blocks :i* mu/ once h ris5 high 9 air4 ,! complex & disord]ly /ructures ( ! ,pi$mont rocks are ^? se5 9 great m\nta9 ranges1 & !re is e reason to believe t ^! rocks aft] _! de=mation rose to m\nta9 height4 ,illu/ration3 ,fig4 #fh4 ,! area ( ! ,laur5tian ,p5epla9 7%ad$7 ,! anci5t ,pi$mont pla9 cuts across ^! upturn$ rocks z indep5d5tly ( _! /ructure z ! ev5 surface ( ! saw$ /ump ( "s great tree is indep5d5t ( ! direction ( its fib]s4 ,h5ce ! ,pi$mont pla9 z x 0 be=e its uplift 0 n a coa/al pla9 =m$ ( /rata spread 9 horizontal %eets b5ea? ! sea & !n uplift$2 nor 0 x a /ructural pla91 due to ! resi/ance to erosion ( "s h>d1 flat-ly+ lay] ( rock4 ,ev5 surfaces develop$ on rocks ( discordant /ructure1 su* z ! ,pi$mont %[s1 are produc$ by long d5udation1 & we may consid] ! ,pi$mont z a p5epla9 =m$ by ! we>+ d[n ( m\nta9 ranges1 & rec5tly uplift$4 ,! ,laur5tian p5epla94 ,?is is ! "n giv5 to a d5ud$ surface on v anci5t rocks :i* ext5ds f ! ,arctic ,ocean to ! ,/4 ,lawr5ce ,riv] & ,lake ,sup]ior1 ) small areas also 9 nor!rn ,wiscons9 & ,new ,york4 ,?r\gh\t ?is ,u-%ap$ area1 :i* incloses ,hudson ,bay )9 its arms1 ! c\ntry rocks h ! complicat$ & contort$ /ructures :i* *>act]ize m\nta9 ranges 7see ,fig4 #agi1 ,p4 #baa74 ,b ! surface ( ! area is by no means m\nta9\s4 ,! sky l9e :5 view$ f ! divides is unbrok5 by m\nta9 peaks or rugg$ hills4 ,! surface ( ! arm we/ ( ,hudson ,bay is g5tly undulat+ & t ( ! ea/]n arm has be5 r\gh5$ to l[-roll+ hills & dissect$ 9 places by su* deep riv] gorges z ^? ( ! ,ottawa & ,sagu5ay4 ,?is imm5se area may be reg>d$ z an anci5t p5epla9 truncat+ ! bases ( long-vani%$ m\nta9s & dissect$ aft] elevation4 ,9 ! examples cit$ ! uplift has be5 a broad "o & to comp>atively little height4 ,:]e p5epla9s h be5 uplift$ to great height & h s9ce be5 well dissect$1 & :]e !y h be5 upfold$ & brok5 & uptilt$1 _! recognition becomes m difficult4 ,yet rec5t obs]v]s h f\nd evid5ces ( anci5t l[l& surfaces ( erosion on ! summits ( ! ,allegh5y ridges1 ! ,cascade ,m\nta9s 7,fig4 #fi71 & ! we/]n slope ( ! ,si]ra ,nevadas4 ,illu/ration3 ,fig4 #fi4 ,view 9 ! ,cascade ,m\nta9s1 ,wa%+ton ,! g5]al level to :i* ^! ridges rise may be acc\nt$ = by ! uplift & dissection ( a once l[-ly+ p5epla9 ,! s\!rn ,appala*ian region4 ,we h "h an example ( an area ! latt] "p ( ^: geological hi/ory may be deciph]$ by means ( its l& =ms4 ,! g5]aliz$ section ( ,figure #gj1 :i* passes f we/ to ea/ across a portion ( ! region 9 ea/]n ,t5nessee1 %[s on ! we/ a "p ( ! broad ,cumb]l& plateau4 ,on ! ea/ is a r\gh5$ upl& plat=m1 f :i* rise 9 ! di/ance ! peaks ( ! ,great ,smoky ,m\nta9s4 ,! plateau1 consi/+ ( /rata b little *ang$ f _! orig9al flat-ly+ attitude1 & ! plat=m1 develop$ on rocks ( disord]$ /ructure made cry/all9e by heat & pressure1 bo? /& at ! common level ( ! l9e ,,ab4 ,!y are sep>at$ by ! ,appala*ian valley1 =ty miles wide1 cut 9 /rata :i* h be5 fold$ & brok5 into long n>r[ blocks4 ,! valley is trav]s$ l5g?wise by long1 l[ ridges1 ! outcropp+ edges ( ! h>d] /rata1 :i* rise to ab\t ! same level1--t ( ! l9e cd4 ,betwe5 ^! ridges /ret* valley l[l&s at ! level ef excavat$ 9 ! weak] rocks1 :ile some:at bel[ !m lie ! *annels ( ! pres5t /reams n[ busily engag$ 9 deep5+ _! b$s4 ,! valley l[l&s4 ,7 !y plan$ by grad$ or ungrad$ /reams8 ,h ! pres5t /reams rea*$ grade8 ,:y did ! /reams cease wid5+ ! floors ( ! valley l[l&s8 ,h[ long s9ce8 ,:5 w !y beg9 anew ! "w ( lat]al planation8 ,:at effect w ?is h on ! ridges if ! pres5t cycle ( erosion cont9ues long un9t]rupt$8 ,illu/ration3 ,fig4 #gj4 ,g5]aliz$ ,section ( ! ,s\!rn ,appala*ian ,region 9 ,ea/]n ,t5nessee ,! ridges ( ! ,appala*ian valley4 ,:y d !y /& above ! valley l[l&s8 ,:y d _! summits lie 9 ab\t ! same plane8 ,refill+ ! valleys int]v5+ betwe5 ^! ridges ) ! mat]ial remov$ by ! /reams1 :at is ! nature ( ! surface ?us re/or$8 ,does ?is surface cd accord ) ! rock /ructures on :i* x has be5 develop$8 ,h[ may x h be5 made8 ,at :at height did ! l& /& !n1 comp>$ ) its pres5t height8 ,:at elevations /ood above ! surface cd8 ,:y8 ,:at "n may y use to designate !m8 ,h[ does ! l5g? ( "t ne$$ to develop ! surface cd comp>e ) t ne$$ to develop ! valley l[l&s8 ,! ,plat=m ,& ,plateau4 ,:y d !y /& at a common level ab8 ,( :at surface may !y be remnants8 ,is x accordant ) ! rock /ructure8 ,h[ 0 x produc$8 ,:at unconsum$ masses ov]look$ x8 ,did ! rocks ( ! ,appala*ian valley /& above ?is surface :5 x 0 produc$8 ,did !y !n /& bel[ x8 ,comp>e ! "t ne$$ to develop ?is surface ) t ne$$ to develop cd4 ,:i* surface is ! old]8 ,h[ _m cycles ( erosion are repres5t$ "h8 ,give ! erosion hi/ory ( ! region by cycles1 beg9n+ ) ! olde/1 ! "w done 9 ea* & ! "w left undone1 :at br\ght ea* cycle to a close1 & h[ long relatively x cont9u$4 ,,*apt] ,,iv ,,riv] ,,deposits ,! *>act]i/ic features ( riv] deposits & ! =ms :i* !y assume may be treat$ "u ?ree heads3 7#a7 valley deposits1 7#b7 bas9 deposits1 & 7#c7 deltas4 ,valley ,deposits ,flood pla9s4 ,! deposits :i* /reams build along _! c\rses at times ( flood are kn[n z flood pla9s4 ,a swift curr5t !n sweeps along ! *annel1 :ile a %all[ %eet ( wat] moves sl[ly ov] ! flood pla91 spread+ ^u x a ?9 lay] ( s$im5t4 ,x has be5 e/imat$ t ea* inundation ( ! ,nile leaves a lay] ( f]tiliz+ silt ?ree hundr$?s ( an in* ?ick ov] ! flood pla9 ( ,egypt4 ,flood pla9s may consi/ ( a ?9 spread ( alluvium ov] ! flat rock floor ( a valley :i* is be+ wid5$ by ! lat]al erosion ( a grad$ /ream 7,fig4 #fj74 ,flood-pla9 deposits ( great ?ickness may be built by aggrad+ riv]s ev5 9 valleys ^: rock floors h nev] be5 ?us wid5$ 7,fig4 #cfh74 ,illu/ration3 ,fig4 #ga4 ,cross ,section ( a ,flood ,pla9 ,a cross section ( a flood pla9 7,fig4 #ga7 %[s t x is highe/ next ! riv]1 slop+ gradually !nce to ! valley sides4 ,^! wide natural embankm5ts are due to ! fact t ! riv] deposit is heavi] ne> ! bank1 :]e ! velocity ( ! silt-lad5 *annel curr5t is fir/ *eck$ by contact ) ! sl[]-mov+ ov]fl[4 ,illu/ration3 ,fig4 #gb4 ,wa/e-fill$ ,valley & ,braid$ ,*annels ( ! ,upp] ,mississippi ,?us bank$ (f f ! /ream1 ! out] portions ( a flood pla9 are (t5 ill-dra9$ & swampy1 & "h vegetal deposits1 su* z peat1 may be int]b$d$ ) riv] silts4 ,a map ( a wide flood pla91 su* z t ( ! ,mississippi or ! ,miss\ri 7,fig4 #gg71 %[s t ! c\rses ( ! tribut>ies on ent]+ x are deflect$ d[n/ream4 ,:y8 ,! aggrad+ /reams by :i* flood pla9s are con/ruct$ gradually build _! imm$iate banks & b$s to high] & high] levels1 & !re=e f9d x easy at times ( great floods to break _! natural embankm5ts & take new c\rses ov] ! pla94 ,9 ?is way !y aggrade ea* portion ( x 9 turn by means ( _! %ift+ *annels4 ,braid$ *annels4 ,a riv] actively engag$ 9 aggrad+ its valley ) co>se wa/e builds a flood pla9 ( comp>atively /eep gradi5t & (t5 fl[s d[n x 9 a fairly direct c\rse & ?r\gh a network ( braid$ *annels4 ,f "t to "t a *annel becomes *ok$ ) wa/e1 & ! wat] no long] f9d+ room 9 x breaks out & cuts & builds itself a new way :i* reunites d[n valley ) ! o!r *annels4 ,?us !re becomes e/abli%$ a network ( ev]-*ang+ *annels inclos+ l[ isl&s ( s& & gravel4 ,illu/ration3 ,fig4 #gc4 ,t]rac$ ,valley ( ,riv] 9 ,c5tral ,asia ,illu/ration3 ,fig4 #gd4 ,t]races c>v$ 9 ,alluvial ,deposits ,:i* is old]1 ! rock floor ( ! valley or ! riv] deposits :i* fill x8 ,:at are ! relative ages ( t]races a1 b1 c1 & e8 ,x w be not$ t ! remnants ( ! high] flood pla9s h n be5 swept away by ! me&]+ riv]1 z x swung f side to side ( ! valley at l[] levels1 because !y h be5 def5d$ by l$ges ( h>d rock 9 ! project+ spurs ( ! initial valley4 ,! /ream has enc\nt]$ su* def5d+ l$ges at ! po9t m>k$ d ,illu/ration3 ,fig4 #ge4 ,riv] ,t]races ( ,rock cov]$ ) ,alluvium c1 rec5t flood pla9 ( ! riv]4 ,to :at processes is x due8 ,acc\nt = ! alluvium at a & b & on ! opposite side ( ! valley at ! same levels4 ,:i* is ! old]8 ,acc\nt = ! flat rock floors on :i* ^! deposits ( alluvium re/4 ,give ! entire hi/ory :i* may be read 9 ! section ,t]races4 ,:ile aggrad+ /reams ?us t5d to %ift _! *annels1 degrad+ /reams1 on ! contr>y1 become m & m deeply intr5*$ 9 _! valleys4 ,x (t5 occurs t a /ream1 aft] hav+ built a flood pla91 ceases to aggrade its b$ because ( a less5$ load or = o!r reasons1 su* z an uplift ( ! region1 & beg9s in/ead to degrade x4 ,x leaves ! orig9al flood pla9 out ( rea* ( ev5 ! highe/ floods4 ,:5 aga9 x rea*es grade at a l[] level x produces a new flood pla9 by lat]al erosion 9 ! old] deposits1 remnants ( :i* /& z t]races on "o or bo? sides ( ! valley4 ,9 ?is way a valley may be l9$ ) a succession ( t]races at diff]5t levels1 ea* level repres5t+ an ab&on$ flood pla94 ,illu/ration3 ,fig4 #gf4 ,developm5t ( a ,me&] ,! dott$ l9e 9 a1 b1 & c %[s ! /age prec$+ t indicate by ! unbrok5 l9e ,me&]s4 ,valleys aggrad$ ) f9e wa/e =m well-nigh level pla9s ov] :i* /reams w9d f side to side ( a direct c\rse 9 symmetric b5ds kn[n z me&]s1 f ! "n ( a w9d+ riv] ( ,asia ,m9or4 ,! giant ,mississippi has develop$ me&]s ) a radius ( "o & "o half miles1 b a little creek may display on its mead[ z p]fect curves only a rod or s 9 radius4 ,on ! flood pla9 ( ei!r riv] or creek we may f9d examples ( ! successive /ages 9 ! developm5t ( ! me&]1 f its beg9n+ 9 ! slight initial b5d suffici5t to deflect ! curr5t aga9/ ! out] side4 ,erod+ "h & deposit+ on ! inn] side ( ! b5d1 x gradually rea*es fir/ ! op5 b5d 7,fig4 #gf1 a7 ^: wid? & l5g? are n f> f equal1 & lat] t ( ! horse%oe me&] 7,fig4 #gf1 b7 ^: diamet] transv]se to ! c\rse ( ! /ream is mu* great] ?an t p>allel ) x4 ,little by little ! neck ( l& project+ into ! b5d is n>r[$1 until at la/ x is cut ?r\gh & a cut-(f is e/abli%$4 ,! old *annel is n[ silt$ up at bo? ends & becomes a cresc5tic lagoon 7,fig4 #gf1 c71 or oxb[ lake1 :i* fills gradually to an arc-%ap$ %all[ depression4 ,illu/ration3 ,fig4 #gg4 ,map ( a portion ( ! ,flood ,pla9 ( ! ,miss\ri ,riv] ,ea* small squ>e repres5ts "o squ>e mile4 ,h[ wide is ! flood pla9 ( ! ,miss\ri8 ,h[ wide is ! flood pla9 ( ! ,big ,si\x8 ,:y is ! latt] riv] deflect$ d[n valley on ent]+ ! flood pla9 ( ! ma/] /ream8 ,h[ d ! me&]s ( ! two riv]s comp>e 9 size8 ,h[ does ! wid? ( ea* flood pla9 comp>e ) ! wid? ( ! belt occupi$ by ! me&]s ( ! riv]8 ,d y f9d traces ( any =m] *annels8 ,flood pla9s *>act]i/ic ( mature riv]s4 ,on rea*+ grade a /ream planes a flat floor = its cont9ually wid5+ valley4 ,ev] cutt+ on ! out] bank ( its curves1 x deposits on ! inn] bank scroll-l flood-pla9 pat*es 7,fig #fj74 ,= a :ile ! valley bluffs d n give its gr[+ me&]s room to develop to _! normal size1 b z planation goes on1 ! bluffs are driv5 back to ! full wid? ( ! me&] belt & /ill lat] to a wid? :i* gives room = broad /ret*es ( flood pla9 on ei!r side 7,fig4 #gg74 ,usually a riv] fir/ atta9s grade ne> its m\?1 & "h fir/ s9ks its b$ to ne> baselevel4 ,ext5d+ its grad$ c\rse up/ream by cutt+ away b>ri] aft] b>ri]1 x comes to h a wid5$ & mature valley ov] its l[] c\rse1 :ile its "y headwat]s are /ill busily erod+ _! b$s4 ,its ungrad$ bran*es may ?us br+ d[n to its l[] c\rse m wa/e ?an x is compet5t to c>ry on to ! sea1 & "h x aggrades its b$ & builds a flood pla9 9 ord] to ga9 a /eep] gradi5t & velocity en\gh to transport its load4 ,z maturity is pa/ & ! relief ( ! l& is less5$1 a small] & small] load ( wa/e is deliv]$ to ! riv]4 ,x n[ has en]gy to sp>e & aga9 degrades its valley1 excavat+ its =m] flood pla9s & leav+ !m 9 t]races on ei!r side1 & at la/ 9 its old age sweep+ !m away4 ,illu/ration3 ,fig4 #gh4 ,alluvial ,cones1 ,wyom+ ,alluvial cones & fans4 ,9 hilly & m\nta9\s c\ntries "o (t5 sees on a valley side a conical or fan-%ap$ deposit ( wa/e at ! m\? ( a lat]al /ream4 ,! cause is obvi\s3 ! "y bran* has n be5 able z yet to we> its b$ to accordant level ) ! already deep5$ valley ( ! ma/] /ream4 ,x !re=e builds its b$ to grade at ! po9t ( juncture by deposit+ "h its load ( wa/e1--a load too heavy to be c>ri$ along ! m g5tle pr(ile ( ! trunk valley4 ,illu/ration3 ,fig4 #gi4 ,tribut>ies & ,di/ribut>ies ( a ,fan-,build+ ,/ream ,:]e riv]s desc5d f a m\nta9\s region ^u ! pla9 !y may build alluvial fans ( exce$+ly g5tle slope4 ,?us ! riv]s ( ! we/]n side ( ! ,si]ra ,nevada ,m\nta9s h spread fans ) a radius ( z mu* z =ty miles & a slope too slight to be detect$ )\t in/rum5ts1 :]e !y leave ! rock-cut canyons 9 ! m\nta9s & desc5d ^u ! broad c5tral valley ( ,cali=nia4 ,z a riv] fl[s ov] its fan x commonly divides into a bran*work ( %ift+ *annels call$ di/ribut>ies1 s9ce !y lead (f ! wat] f ! ma9 /ream4 ,9 ?is way ea* "p ( ! fan is aggrad$ & its symmetric =m is pres]v$4 ,pi$mont pla9s4 ,m\nta9 /reams may build _! conflu5t fans into widespread pi$mont 7foot ( ! m\nta97 alluvial pla9s4 ,^! are especially *>act]i/ic ( arid l&s1 :]e ! /reams )] z !y fl[ out ^u ! ?ir/y l[l&s & are !re=e compell$ to lay d[n a l>ge portion ( _! load4 ,9 humid climates m\nta9-born /reams are usually compet5t to c>ry _! loads ( wa/e on to ! sea1 & h en]gy to sp>e to cut ! l[] m\nta9 slopes into foo?ills4 ,9 arid regions foo?ills are commonly abs5t & ! ranges rise1 z f p$e/als1 above broad1 slop+ pla9s ( /ream-laid wa/e4 ,illu/ration3 ,fig4 #hj4 ,section f ! ,rocky ,m\nta9s ,ea/w>d ,riv] deposits dott$ ,! ,high ,pla9s4 ,! riv]s :i* fl[ ea/w>d f ! ,rocky ,m\nta9s h unit$ _! fans 9 a cont9u\s %eet ( wa/e :i* /ret*es =w>d f ! base ( ! m\nta9s = hundr$s ( miles & 9 places is five hundr$ feet ?ick 7,fig4 #hj74 ,t ! deposit 0 made 9 anci5t times on l& & n 9 ! sea is prov$ by ! rema9s :i* x conta9s ( l& animals & plants ( species n[ ext9ct4 ,t x 0 laid by riv]s & n by fre%-wat] lakes is %[n by its /ructure4 ,wide /ret*es ( flat-ly+1 clays & s&s are int]rupt$ by long1 n>r[ belts ( gravel :i* m>k ! *annels ( ! anci5t /reams4 ,gravels1 & s&s are (t5 cross b$d$1 & _! well worn pebbles may be id5tifi$ ) ! rocks ( ! m\nta9s4 ,aft] build+ ?is %eet ( wa/e ! /reams ceas$ to aggrade & began ! "w ( de/ruction4 ,l>ge un]od$ remnants1 _! surfaces flat z a floor1 rema9 z ! ,high ,pla9s ( we/]n ,kansas & ,nebraska4 ,riv] deposits 9 subsid+ tr\ghs4 ,to a geologi/ ! mo/ important riv] deposits are ^? :i* ga!r 9 areas ( gradual subsid5ce2 !y are (t5 ( va/ ext5t & imm5se ?ickness1 & su* deposits ( pa/ geological ages h n infrequ5tly be5 pres]v$1 ) all _! records ( ! times 9 :i* !y 7 built1 by be+ c>ri$ bel[ ! level ( ! sea1 to be br\ght to light by a lat] uplift4 ,on ! o!r h&1 riv] deposits :i* rema9 above baselevels ( erosion are swept away comp>atively soon4 ,! ,great ,valley ,( ,cali=nia is a monoton\sly level pla9 ( great f]tility1 f\r hundr$ miles 9 l5g? & fifty miles 9 av]age wid?1 built ( wa/e swept d[n by /reams f ! m\nta9 ranges :i* inclose x1--! ,si]ra ,nevada on ! ea/ & ! ,coa/ ,range on ! we/4 ,on ! wa/e slopes at ! foot ( ! bord]+ hills co>se gravels & ev5 b[ld]s are left1 :ile ov] ! int]ior ! sl[-fl[+ /reams at times ( flood spread wide %eets ( silt4 ,organic deposits are n[ =m+ by ! decay ( vegetation 9 swampy tule 7re$7 l&s & 9 %all[ lakes :i* occupy depressions left by ! aggrad+ /reams4 ,deep bor+s %[ t ?is great tr\gh is fill$ to a dep? ( at lea/ two ?\s& feet bel[ sea level ) rec5t unconsolidat$ s&s & silts conta9+ logs ( wood & fre%-wat] %ells4 ,^! are l& deposits1 & ! abs5ce ( any m>9e deposits among !m proves t ! region has n be5 invad$ by ! sea s9ce ! accumulation began4 ,x has !re=e be5 sl[ly subsid+ & its /reams1 al?\gh cont9ually c>ri$ bel[ grade1 h yet be5 able to aggrade ! surface z rapidly z ! region sank1 & h ma9ta9$ x1 z at pres5t1 slightly above sea level4 ,! ,indo-,gangetic ,pla91 spread by ! ,brahmaputra1 ! ,ganges1 & ! ,indus riv] sy/ems1 /ret*es = sixte5 hundr$ miles along ! s\!rn base ( ! ,himalaya ,m\nta9s & occupies an area ( ?ree hundr$ ?\s& squ>e miles 7,fig4 #cdb74 ,x consi/s ( ! flood pla9s ( ! ma/] /reams & ! conflu5t fans ( ! tribut>ies :i* issue f ! m\nta9s on ! nor?4 ,l>ge areas are subject to ov]fl[ ea* season ( flood1 & /ill l>g] tracts m>k ab&on$ flood pla9s bel[ :i* ! riv]s h n[ cut _! b$s4 ,! pla9 is built ( f>-/ret*+ b$s ( clay1 p5etrat$ by /reaks ( s&1 & also ( gravel ne> ! m\nta9s4 ,b$s ( impure peat occur 9 x1 & x conta9s fre%-wat] %ells & ! bones ( l& animals ( species n[ liv+ 9 nor!rn ,india4 ,at ,luckn[ an artesian well 0 sunk to "o ?\s& feet bel[ sea level )\t rea*+ ! bottom ( ^! riv]-laid s&s & silts1 prov+ a sl[ subsid5ce ) :i* ! aggrad+ riv]s h kept pace4 ,w>p$ valleys4 ,x is n necess>y t an area %\ld s9k bel[ sea level 9 ord] to be fill$ ) /ream-swept wa/e4 ,high valleys among gr[+ m\nta9 ranges may suff] w>p+1 or may be blockad$ by ris+ m\nta9 folds a?w>t !m4 ,:]e ! de=mation is rapid en\gh1 ! riv] may be pond$ & ! valley fill$ ) lake-laid s$im5ts4 ,ev5 :5 ! riv] is able to ma9ta9 its "r ( way x may yet h its declivity s less5$ t x is compell$ to aggrade its c\rse cont9ually1 fill+ ! valley ) riv] deposits :i* may gr[ to an enorm\s ?ickness4 ,beh9d ! out] ranges ( ! ,himalaya ,m\nta9s lie sev]al wa/e-fill$ valleys1 ! l>ge/ ( :i* are ,ka%mir & ,nepal1 ! =m] be+ an alluvial pla9 ab\t z l>ge z ! /ate ( ,delaw>e4 ,! riv]s :i* dra9 ^! pla9s h already cut d[n _! outlet gorges suffici5tly to beg9 ! task ( ! removal ( ! broad accumulations :i* !y h br\ght 9 f ! surr\nd+ m\nta9s4 ,_! pres5t flood pla9s lie z mu* z "s hundr$s ( feet bel[ wide alluvial t]races :i* m>k _! =m] levels4 ,inde$1 ! horizontal b$s ( ! ,hundes ,valley h be5 tr5*$ to ! dep? ( ne>ly ?ree ?\s& feet by ! ,sutlej ,riv]4 ,^! deposits are rec5t or subrec5t1 = !re h be5 f\nd at v>i\s levels ! rema9s ( l& plants & l& & fre%-wat] %ells1 & 9 "s ! bones ( su* animals z ! hy5a & ! goat1 ( species or ( g5]a n[ liv+4 ,su* s(t deposits _c be expect$ to endure ?r\gh any consid]able l5g? ( future "t ! rapid erosion to :i* _! great height above ! level ( ! sea w subject !m4 ,illu/ration3 ,fig4 #ha4 ,cross ,section ( ,aggrad$ ,valley1 %[+ ,/ructure ( ,riv] ,deposits ,*>act]i/ics ( riv] deposits4 ,! examples j cit$ tea* cle>ly ! *>act]i/ic features ( ext5sive riv] deposits4 ,^! deposits consi/ ( broad1 flat-ly+ %eets ( clay & f9e s& left by ! ov]fl[ at "t ( flood1 & trav]s$ "h & !re by long1 n>r[ /rips ( co>se1 cross-b$d$ s&s & gravels ?r[n d[n by ! swift] curr5ts ( ! %ift+ *annels4 ,occasional b$s ( muck m>k ! sites ( %all[ lakelets or fre%-wat] swamps4 ,! v>i\s /rata also conta9 "s rema9s ( ! c\ntless myriads ( animals & plants :i* live ^u ! surface ( ! pla9 z x is 9 process ( build+4 ,riv] %ells su* z ! mussel1 l& %ells su* z ^? ( snails1 ! bones ( fi%es & ( su* l& animals z suff] dr[n+ at times ( flood or are mir$ 9 swampy places1 logs ( wood1 & ! /ems & leaves ( plants are examples ( ! v>iety ( ! rema9s ( l& & fre%-wat] organisms :i* are entomb$ 9 riv] deposits & seal$ away z a record ( ! life ( ! "t1 & z pro( t ! deposits 7 laid by /reams & n b5ea? ! sea4 ,bas9 ,deposits ,deposits 9 dry bas9s4 ,on des]t areas )\t outlet to ! sea1 z on ! ,great ,bas9 ( ! ,unit$ ,/ates & ! des]ts ( c5tral ,asia1 /ream-swept wa/e accumulates indef9itely4 ,! riv]s ( ! surr\nd+ m\nta9s1 f$ by ! ra9s & melt+ sn[s ( ^! comp>atively moi/ elevations1 dry & soak away z !y come d[n ^u ! arid pla9s4 ,!y are compell$ to lay aside _! entire load ( wa/e erod$ f ! m\nta9 valleys1 9 fans :i* gr[ to enorm\s size1 rea*+ 9 "s in/ances ?\s&s ( feet 9 ?ickness4 ,! monoton\s levels ( ,turke/an include va/ alluvial tracts n[ 9 process ( build+ by ! floods ( ! frequ5tly %ift+ *annels ( ! ,oxus & o!r riv]s ( ! region4 ,= ab\t sev5 hundr$ miles f its m\? 9 ,aral ,lake ! ,oxus receives no tribut>ies1 s9ce ev5 ! l>g] bran*es ( its sy/em are lo/ 9 a network ( di/ribut>ies & *ok$ ) des]t s&s be=e !y rea* _! ma/] /ream4 ,^! aggrad+ riv]s1 :i* h *annels b no valleys1 spread _! muddy floods--:i* 9 ! case ( ! ,oxus sometimes equal ! av]age volume ( ! ,mississippi--f> & wide ov] ! pla91 wa%+ ! bases ( ! des]t dunes4 ,playas4 ,9 arid int]ior bas9s ! c5tral depressions may be occupi$ by playas1--pla9s ( f9e mud wa%$ =w>d f ! m>g9s4 ,9 ! wet season ! playa is cov]$ ) a ?9 %eet ( muddy wat]1 a playa lake1 suppli$ usually by "s /ream at flood4 ,9 ! dry season ! lake evaporates1 ! riv] :i* f$ x retreats1 & !re is left to view a h>d1 smoo?1 level floor ( sun-bak$ & sun-crack$ yell[ clay utt]ly devoid ( vegetation4 ,9 ! ,black ,rock des]t ( ,nevada a playa lake spreads ov] an area fifty miles long & tw5ty miles wide4 ,9 summ] x disappe>s2 ! ,qu9n ,riv]1 :i* fe$s x1 %r9ks back "o hundr$ miles t[>d its s\rce1 leav+ an absolutely b>r5 floor ( clay1 level z ! sea4 ,lake deposits4 ,reg>d+ lakes z p>ts ( riv] sy/ems1 we may n[ notice ! *>act]i/ic features ( ! deposits 9 lake bas9s4 ,s\nd+s 9 lakes ( consid]able size & dep? %[ t _! bottoms are be+ cov]$ ) t9e clays4 ,s& & gravel are f\nd along2 _! m>g9s1 be+ br\ght 9 by /reams & worn by waves f ! %ore1 b !re are no tidal or o!r /rong curr5ts to sweep co>se wa/e out f %ore to any consid]able di/ance4 ,:]e f9e clays are n[ f\nd on ! l& 9 ev51 horizontal lay]s conta9+ ! rema9s ( fre%-wat] animals & plants1 uncut by *annels till$ ) cross-b$d$ gravels & s&s & bord]$ by bea* deposits ( co>se wa/e1 we may safely inf] ! exi/5ce ( anci5t lakes4 ,m>l4 ,m>l is a s(t1 :iti% deposit ( c>bonate ( lime1 m+l$ (t5 ) m or less ( clay1 accumulat$ 9 small lakes ^: fe$+ spr+s are *>g$ ) c>bonate ( lime & into :i* little wa/e is wa%$ f ! l&4 ,su* lakelets are n infrequ5t on ! surface ( ! y\ng] drift %eets ( ,mi*igan & nor!rn ,indiana1 :]e _! b$s ( m>l--sometimes z mu* z =ty feet ?ick--are utiliz$ 9 ! manufacture ( ,portl& cem5t4 ,! deposit results f ! decay ( c]ta9 aquatic plants :i* secrete lime c>bonate f ! wat]1 f ! decomposition ( ! calc>e\s %ells ( t9y mollusks :i* live 9 c\ntless numb]s on ! lake floor1 & 9 "s cases app>5tly f *emical precipitation4 ,peat4 ,we h se5 h[ lakelets are ext+ui%$ by ! decay+ rema9s ( ! vegetation :i* !y support4 ,a section ( su* a fossil lake %[s t bel[ ! gr[+ mosses & o!r plants ( ! surface ( ! bog lies a spongy mass compos$ ( dead vegetable tissue1 :i* passes d[nw>d gradually into peat1--a d5se1 d>k br[n c>bonace\s deposit 9 :i*1 to ! unaid$ eye1 little or no trace ( vegetable /ructure rema9s4 ,:5 dri$1 peat =ms a fuel ( "s value & is us$ ei!r cut into slabs & dri$ or press$ into bricks by ma*9]y4 ,illu/ration3 ,fig4 #hb4 ,digg+ ,peat1 ,scotl& ,:5 vegetation decays 9 op5 air ! c>bon ( its tissues1 tak5 f ! atmosph]e by ! leaves1 is oxidiz$ & return$ to x 9 its orig9al =m ( c>bon dioxide4 ,b decompos+ 9 ! pres5ce ( wat]1 z 9 a bog1 :]e ! oxyg5 ( ! air is exclud$1 ! c>bonace\s matt] ( plants accumulates 9 deposits ( peat4 ,peat bogs are num]\s 9 regions lately ab&on$ by glaci] ice1 :]e riv] sy/ems are s immature t ! initial depressions left 9 ! %eet ( drift spread ov] ! c\ntry h n yet be5 dra9$4 ,"o t5? ( ! surface ( ,irel& is said to be cov]$ ) peat1 & small bogs ab\nd 9 ! drift-cov]$ area ( ,new ,engl& & ! /ates ly+ z f> we/ z ! ,miss\ri ,riv]4 ,9 ,massa*usetts alone x has be5 reckon$ t !re are fifte5 billion cubic feet ( peat1 ! l>ge/ bog occupy+ sev]al ?\s& acres4 ,mu* l>g] swamps occur on ! "y coa/al pla9 ( ! ,atlantic f ,new ,j]sey to ,florida4 ,! ,dismal ,swamp1 = example1 9 ,virg9ia & ,nor? ,c>ol9a is =ty miles across4 ,x is cov]$ ) a d5se gr[? ( wat]-lov+ trees su* z ! cypress & black gum4 ,! c5t] ( ! swamp is occupi$ by ,lake ,drummond1 a %all[ lake sev5 miles 9 diamet]1 ) banks ( pure-peat1 & /ill n>r[+ f ! encroa*m5t ( vegetation along its bord]s4 ,salt lakes4 ,9 arid climates a lake r>ely receives suffici5t infl[ to enable x to rise to ! bas9 rim & f9d an outlet4 ,be=e ?is height is rea*$ its surface becomes l>ge en\gh to dis*>ge by evaporation into ! dry air ! am\nt ( wat] t is suppli$ by /reams4 ,z su* a lake has no outlet1 ! m9]als 9 solution br\ght into x by its /reams _c escape f ! bas94 ,! lake wat] becomes m & m heavily *>g$ ) su* sub/ances z common salt & ! sulphates & c>bonates ( lime1 ( soda1 & ( pota%1 & ^! are ?r[n d[n f solution "o aft] ano!r z ! po9t ( saturation = ea* m9]al is rea*$4 ,c>bonate ( lime1 ! lea/ soluble & (t5 ! mo/ abundant m9]al br\ght 91 is ! fir/ to be precipitat$4 ,z conc5tration goes on1 gypsum1 :i* is insoluble 9 a /rong br9e1 is deposit$1 & aft]w>ds common salt4 ,z ! saltness ( ! lake v>ies ) ! seasons & ) climatic *anges1 gypsum & salt are laid 9 alt]nate b$s & are int]leav$ ) s$im5t>y clays spread f ! wa/e br\ght 9 by /reams at times ( flood4 ,few =ms ( life c live 9 bodies ( salt wat] s conc5trat$ t *emical deposits take place1 & h5ce ! b$s ( salt1 gypsum1 & silt ( su* lakes are q b>r5 ( ! rema9s ( life4 ,simil> deposits are precipitat$ by ! conc5tration ( sea wat] 9 lagoons & arms ( ! sea cut (f f ! ocean4 ,illu/ration3 ,fig4 #hc4 ,map ( ,lake ,bonneville & ,lahontan ,f ,davis' ,physical ,geography ,lakes ,bonneville & ,lahontan4 ,^! names are giv5 to ext9ct lakes :i* once occupi$ l>ge areas 9 ! ,great ,bas91 ! =m] 9 ,utah1 ! latt] 9 nor?we/]n ,nevada4 ,_! records rema9 9 old horizontal bea* l9es :i* !y drew along _! m\nta9\s %ores at ! diff]5t levels at :i* !y /ood1 & 9 ! deposits ( _! b$s4 ,at its highe/ /age ,lake ,bonneville1 !n "o ?\s& feet deep1 ov]fl[$ to ! nor? & 0 a fre%-wat] lake4 ,z x %rank bel[ ! outlet x became m & m salty1 & ! ,great ,salt ,lake1 its )]$ residue1 is n[ deposit+ salt along its %ores4 ,9 its /rong br9e lime c>bonate is insoluble1 & t br\ght 9 by /reams is ?r[n d[n at once 9 ! =m ( trav]t9e4 ,illu/ration3 ,fig4 #hd4 ,section ( ,deposits 9 ,b$s ( ,lakes ,bonneville & ,lahontan ,lake ,lahontan nev] _h an outlet4 ,! fir/ *emical deposits to be made along its %ores 7 deposits ( trav]t9e1 9 places eighty feet ?ick4 ,its floor is spread ) f9e clays1 :i* mu/ h be5 laid 9 deep1 /ill wat]1 & :i* are *>g$ ) ! salts absorb$ by !m z ! br9y wat] ( ! lake dri$ away4 ,^! s$im5t>y clays are 9 two divisions1 ! upp] & l[]1 ea* be+ ab\t "o hundr$ feet ?ick 7a & c1 ,fig4 #hd74 ,!y are sep>at$ by heavy deposits ( well-r\nd$1 cross-b$d$ gravels & s&s 7b1 ,fig4 #hd71 simil> to ^? spread at ! pres5t "t by ! int]mitt5t /reams ( arid regions4 ,a simil> record is %[n 9 ! old floors ( ,lake ,bonneville4 ,:at conclusions d y draw f ^! facts z to ! hi/ory ( ^! anci5t lakes8 ,deltas ,9 ! riv] deposits :i* are left above sea level p>ticles ( wa/e are all[$ to l+] only = a "t4 ,f alluvial fans & flood pla9s !y are con/antly be+ tak5 up & swept f>!r on d[n/ream4 ,al?\gh ^! l& =ms may long p]si/1 ! p>ticles :i* compose !m are ev] *ang+4 ,we may !re=e ?9k ( ! alluvial deposits ( a valley z a /ream ( wa/e f$ by ! wa/e mantle z x creeps & wa%es d[n ! valley sides1 & sl[ly mov+ onw>ds to ! sea4 ,9 bas9s wa/e f9ds a long] re/1 b soon] or lat] lakes & dry bas9s are dra9$ or fill$1 & _! deposits1 if above sea level1 resume _! j\rney to _! f9al goal4 ,x is only :5 c>ri$ bel[ ! level ( ! sea t !y are indef9itely pres]v$4 ,on rea*+ ?is t]m9us1 riv]s deliv] _! load to ! ocean4 ,9 "s cases ! ocean is able to take x up by means ( /rong tidal & o!r curr5ts1 & to dispose ( x 9 ways :i* we %all /udy lat]4 ,b (t5 ! load is s l>ge1 or ! tides are s weak1 t mu* ( ! wa/e :i* ! riv] br+s 9 settles at its m\?1 !re build+ up a deposit call$ ! delta1 f ! ,greek lett] 7,d7 ( t "n1 ^: %ape x sometimes resembles4 ,deltas & alluvial fans h _m common *>act]i/ics4 ,bo? owe _! orig9 to a sudd5 *eck 9 ! velocity ( ! riv]1 compell+ a deposit ( ! load2 bo? are triangul> 9 outl9e1 ! apex po9t+ up/ream2 & bo? are trav]s$ by di/ribut>ies :i* build up all p>ts 9 turn4 ,9 a delta we may di/+ui% deposits ( two di/9ct k9ds1--! subm>9e & ! subarial4 ,9 "p a delta is built ( wa/e br\ght d[n by ! riv] & r$i/ribut$ & spread by waves & tides ov] ! sea bottom adjac5t to ! riv]'s m\?4 ,! orig9 ( ^! deposits is record$ 9 ! rema9s ( m>9e animals & plants :i* !y conta94 ,illu/ration3 ,fig4 #he4 ,delta ( ! ,mississippi ,riv] ,z ! subm>9e delta gr[s ne> to ! level ( ! sea ! di/ribut>ies ( ! riv] cov] x ) subarial deposits altoge!r simil> to ^? ( ! flood pla91 ( :i* inde$ ! subarial delta is ! prolongation4 ,"h ext5d$ deposits ( peat may accumulate 9 swamps1 & ! rema9s ( l& & fre%-wat] animals & plants swept d[n by ! /ream are imb$d$ 9 ! silts laid at times ( flood4 ,bor+s made 9 ! deltas ( great riv]s su* z ! ,mississippi1 ! ,ganges1 & ! ,nile1 %[ t ! subarial portion (t5 rea*es a surpris+ ?ickness4 ,lay]s ( peat1 old soils1 & =e/ gr\nds ) ! /umps ( trees are discov]$ hundr$s ( feet bel[ sea level4 ,9 ! ,nile delta "s eight lay]s ( co>se gravel 7 f\nd int]b$d$ ) riv] silts1 & 9 ! ,ganges delta at ,calcutta a bor+ ne>ly five hundr$ feet 9 dep? /opp$ 9 su* a lay]4 ,! ,mississippi has built a delta ( twelve ?\s& ?ree hundr$ squ>e miles1 & is pu%+ ! natural embankm5ts ( its *ief di/ribut>ies into ! ,gulf at a maximum rate ( a mile 9 sixte5 ye>s4 ,muddy %oals surr\nd its front1 %all[ lakes1 e4g4 lakes ,pont*>tra9 & ,borgne1 are =m$ betwe5 ! gr[+ delta & ! old %ore l9e1 & elongate lakes & swamps are inclos$ betwe5 ! natural embankm5ts ( ! di/ribut>ies4 ,! delta ( ! ,indus ,riv]1 ,india1 lies s l[ along %ore t a broad tract ( c\ntry is ov]fl[$ by ! highe/ tides4 ,! subm>9e portion ( ! delta has be5 built to ne> sea level ov] s wide a belt (f%ore t 9 _m places l>ge vessels _c come ev5 )9 sight ( l& because ( ! %all[ wat]4 ,illu/ration3 ,fig4 #hf4 ,radial ,section ( a ,delta ,?is section ( a delta illu/rates ! /ructure ( ! plat=m :i* swift /reams well load$ ) co>se wa/e build 9 ! wat] bodies into :i* !y empty4 ,?ree memb]s may be di/+ui%$3 ! bottom set b$s1 a3 ! =e set b$s1 b2 & ! top set b$s1 c4 ,acc\nt = ! slope ( ea* ( ^!4 ,:y are ! bottom set b$s ( ! f9] mat]ial & :y d !y ext5d beyond ! o!rs8 ,h[ does ! pr(ile ( ?is delta diff] f t ( an alluvial cone & :y8 ,a =m] arm ( ! sea1 ! ,rann ( ,cut*1 adjo9+ ! delta on ! ea/ has be5 silt$ up & is n[ an imm5se b>r5 flat ( s&y mud two hundr$ miles 9 l5g? & "o hundr$ miles 9 greate/ bread?4 ,ea* summ] x is flood$ ) salt wat] :5 ! sea is br\ght 9 by /rong s\?we/]ly monsoon w9ds1 & ! climate dur+ ! rema9d] ( ! ye> is hot & dry4 ,by ! evaporation ( sea wat] ! soil is ?us left s salty t no vegetation c gr[ ^u x1 & 9 places b$s ( salt sev]al feet 9 ?ickness h accumulat$4 ,"u l conditions salt b$s ( great ?ickness h be5 =m$ 9 ! pa/ & are n[ f\nd buri$ among ! deposits ( anci5t deltas4 ,subsid5ce ( great deltas4 ,z a rule great deltas are sl[ly s9k+4 ,9 "s in/ances upbuild+ by riv] deposits has gone on z rapidly z ! region has subsid$4 ,! entire ?ickness ( ! ,ganges delta1 = example1 s f> z x has be5 s\nd$1 consi/s ( deposits laid 9 op5 air4 ,9 o!r cases int]b$d$ lime/ones & o!r s$im5t>y rocks conta9+ m>9e fossils prove t at times subsid5ce has ga9$ on ! upbuild+ & ! delta has be5 cov]$ ) ! sea4 ,x is by gradual depression t delta deposits atta9 enorm\s ?ickness1 &1 be+ l[]$ b5ea? ! level ( ! sea1 are safely pres]v$ f erosion until a movem5t ( ! e>?'s cru/ 9 ! opposite direction lifts !m to =m "p ( ! l&4 ,we %all read lat] 9 ! h>d rocks ( our cont95t ! records ( su* anci5t deltas1 & we %all n be surpris$ to f9d !m z ?ick z are ^? n[ build+ at ! m\?s ( great riv]s4 ,lake deltas4 ,deltas are also =m$ :]e /reams lose _! velocity on ent]+ ! /ill wat]s ( lakes4 ,! %ore l9es ( ext9ct lakes1 su* z ,lake ,agassiz & ,lakes ,bonneville & ,lahontan1 may be trac$ by ! heavy deposits at ! m\?s ( _! tribut>y /reams4 99 99 99 99 99 ,we h se5 t ! "w ( /reams is to dra9 ! l&s ( ! wat] p\r$ ^u !m by ! ra9fall1 to we> !m d[n1 & to c>ry _! wa/e away to ! sea1 !re to be rebuilt by o!r ag5ts into s$im5t>y rocks4 ,! anci5t /rata ( :i* ! cont95ts are l>gely made are compos$ *iefly ( mat]ial ?us worn f /ill m anci5t l&s--l&s ) _! hills & valleys l ^? ( to-day--& c>ri$ by _! riv]s to ! ocean4 ,9 all geological times1 z at ! pres5t1 ! "w ( /reams has be5 to de/roy ! l&s1 & 9 s do+ to furni% to ! ocean ! mat]ials f :i* ! l&s ( future ages 7 to be made4 ,be=e we consid] h[ ! wa/e ( ! l& br\ght 9 by /reams is rebuilt ^u ! ocean floor1 we mu/ proce$ to /udy ! "w ( two ag5ts1 glaci] ice & ! w9d1 :i* cop]ate ) riv]s 9 ! d5udation ( ! l&4 ,illu/ration3 ,fig4 #hg4 ,section ( ,undiff]5tiat$ ,drift ne> ,*icago ,,*apt] ,v ,,! ,,"w ,,( ,,glaci]s ,! drift4 ,! surface ( nor!a/]n ,nor? ,am]ica1 z f> s\? z ! ,ohio & ,miss\ri riv]s1 is g5]ally cov]$ by ! drift1--a =mation :i* is q unlike any :i* we h s f> /udi$4 ,a section ( x1 su* z t illu/rat$ 9 ,figure #hg1 %[s t = ! mo/ "p x is un/ratifi$1 consi/+ ( clay1 s&1 pebbles1 & ev5 l>ge b[ld]s1 all m+l$ pell-mell toge!r4 ,! ag5t :i* laid ! drift is "o :i* c c>ry a load ( mat]ial ( all sizes1 f ! l>ge/ b[ld] to ! f9e/ clay1 & deposit x )\t sort+4 ,illu/ration3 ,fig4 #hh4 ,*>act]i/ic ,pebbles f ! ,drift ,no4 #a has six facets2 ,no4 #d1 orig9ally a r\nd$ riv] pebble1 has be5 nibbl$ d[n to "o flat face2 ,nos4 #c & #e are batt]$ subangul> fragm5ts on "o side only ,! /ones ( ! drift are ( _m k9ds4 ,! region f :i* x 0 ga!r$ may well h be5 l>ge 9 ord] to supply ^! _m diff]5t v>ieties ( rocks4 ,pebbles & b[ld]s h be5 left f> f _! orig9al homes1 z may be se5 9 s\!rn ,i[a1 :]e ! drift conta9s nuggets ( copp] br\ght f ! region ab\t ,lake ,sup]ior4 ,! ag5t :i* laid ! drift is "o able to ga!r its load ov] a l>ge area & c>ry x a long way4 ,illu/ration3 ,fig4 #hi4 ,smoo!d & ,scor$ ,rock ,surface expos$ to ,view by ! ,removal ( ,ov]ly+ ,drift1 ,i[a ,! pebbles ( ! drift are unlike ^? r\nd$ by runn+ wat] or by waves4 ,!y are m>k$ ) scrat*es4 ,"s are angul>1 _m h _h _! edges blunt$1 :ile o!rs h be5 gr\nd flat & smoo? on "o or m sides1 l gems :i* h be5 facet$ by be+ held firmly aga9/ ! lapid>y's :eel 7,fig4 #hh74 ,9 _m places ! upp] surface ( ! c\ntry rock b5ea? ! drift has be5 swept clean ( residual clays & o!r wa/e4 ,all rock rott5 has be5 plan$ away1 & ! l$ges ( s\nd rock to :i* ! surface has be5 cut d[n h be5 rubb$ smoo? & scrat*$ ) long1 /raight1 p>allel l9es 7,fig4 #hi74 ,! ag5t :i* laid ! drift c hold s& & pebbles firmly 9 its grasp & c gr9d !m aga9/ ! rock b5ea?1 ?us plan+ x d[n & scor+ x1 :ile facet+ ! pebbles also4 ,nei!r wat] nor w9d c d ^! ?+s4 ,inde$1 no?+ l ! drift is be+ =m$ by any process n[ at "w any:]e 9 ! ea/]n ,unit$ ,/ates4 ,to f9d ! ag5t :i* has laid ?is ext5sive =mation we mu/ g to a region ( diff]5t climatic conditions4 ,illu/ration3 ,fig4 #ij4 ,map ( ,gre5l& ,glaci] ice cov]s all b ! areas %ad$ ,! inl& ice ( ,gre5l&4 ,gre5l& is ab\t fifte5 hundr$ miles long & ne>ly sev5 hundr$ miles 9 greate/ wid?4 ,) ! exception ( a n>r[ fr+e ( m\nta9\s coa/ l&1 x is completely buri$ b5ea? a %eet ( ice1 9 %ape l a va/ :ite %ield1 ^: convex surface rises to a height ( n9e ?\s& feet above ! sea4 ,! few explor]s :o h cross$ ! ice cap f\nd x a trackless des]t de/itute ( all life save su* l[ly =ms z ! microscopic plant :i* produces ! s-call$ r$ sn[4 ,on ! smoo? pla9 ( ! int]ior no rock wa/e relieves ! sn['s dazzl+ :it5ess2 no /reams ( runn+ wat] are se52 ! sil5ce is brok5 only by h[l+ /orm w9ds & ! ru/le ( ! surface sn[ :i* !y drive be=e !m4 ,s\nd+ ) long poles1 explor]s f9d t bel[ ! p[d]y sn[ ( ! late/ sn[fall lie successive lay]s ( e>li] sn[s1 :i* gr[ m & m compact d[nw>d1 & at la/ h alt]$ to imp5etrable ice4 ,! ice cap =m$ by ! accumulat$ sn[s ( unc\nt$ c5turies may well be m ?an a mile 9 dep?4 ,ice ?us =m$ by ! compact+ ( sn[ is di/+ui%$ :5 9 motion z glaci] ice4 ,illu/ration3 ,fig4 #ia4 ,hypo!tical ,cross ,section ( ,gre5l& ,! inl& ice ( ,gre5l& moves4 ,x fl[s ) imp]ceptible sl[ness "u its own weight1 l1 a mass ( "s visc\s or pla/ic sub/ance1 su* z pit* or molasses c&y1 9 all directions outw>d t[>d ! sea4 ,ne> ! edge x has s ?9n$ t m\nta9 peaks are laid b>e1 ^! isl&s 9 ! sea ( ice be+ kn[n z nunataks4 ,d[n ! valleys ( ! coa/al belt x dra9s 9 sep>ate /reams ( ice1 or glaci]s4 ,! l>ge/ ( ^! rea* ! sea at ! head ( inlets1 & are !re=e call$ tide glaci]s4 ,_! fronts /& s deep 9 sea wat] t !re is visible seldom m ?an ?ree hundr$ feet ( ! wall ( ice1 :i* 9 _m glaci]s mu/ be two ?\s& & m feet high4 ,f ! sea walls ( tide glaci]s great fragm5ts break (f & float away z iceb]gs4 ,?us sn[s :i* fell 9 ! int]ior ( ?is nor!rn l&1 p]haps _m ?\s&s ( ye>s ago1 are c>ri$ 9 ! =m ( iceb]gs to melt at la/ 9 ! ,nor? ,atlantic4 ,gre5l&1 !n1 is be+ model$ ov] ! va/ ext5t ( its int]ior n by /reams ( runn+ wat]1 z are regions 9 w>m & humid climates1 nor by curr5ts ( air1 z are des]ts to a l>ge ext5t1 b by a %eet ( fl[+ ice4 ,:at ! ice %eet is do+ 9 ! int]ior we may inf] f a /udy ( ! sep>ate glaci]s into :i* x breaks at its edge4 ,! small] ,gre5l& glaci]s4 ,_m ( ! small] glaci]s ( ,gre5l& d n rea* ! sea1 b deploy on pla9s ( s& & gravel4 ,! edges ( ^! ice tongues are (t5 z abrupt z if slic$ away ) a knife 7,fig4 #ib71 & _! /ructure is ?us readily se54 ,!y are /ratifi$1 _! lay]s repres5t+ 9 "p ! successive sn[falls ( ! int]ior ( ! c\ntry4 ,! upp] lay]s are commonly :ite & free f /ones2 b ! l[] lay]s1 to ! height ( a hundr$ feet or m1 are d>k ) debris :i* is be+ sl[ly c>ri$ on4 ,s ?ickly /udd$ ) /ones is ! base ( ! ice t x is sometimes difficult to di/+ui% x f ! rock wa/e :i* has be5 sl[ly dragg$ b5ea? ! glaci] or left ab\t its edges4 ,! wa/e b5ea? & ab\t ! glaci] is unsort$4 ,! /ones are ( _m k9ds1 & numb]s ( !m h be5 gr\nd to flat faces4 ,:]e ! front ( ! ice has retreat$ ! rock surface is se5 to be plan$ & scor$ 9 places by ! /ones froz5 fa/ 9 ! sole ( ! glaci]4 ,illu/ration3 ,fig4 #ib4 ,a ,gre5l& ,glaci] ,we h n[ f\nd 9 glaci] ice an ag5t able to produce ! drift ( ,nor? ,am]ica4 ,! ice %eet ( ,gre5l& is n[ do+ :at we h se5 0 done 9 ! rec5t pa/ 9 our own l&4 ,x is c>ry+ = long di/ances rocks ( _m k9ds ga!r$1 we may inf]1 ov] a l>ge ext5t ( c\ntry4 ,x is lay+ d[n its load )\t assortm5t 9 un/ratifi$ deposits4 ,x gr9ds d[n & scores ! rock ov] :i* x moves1 & 9 ! process _m ( ! pebbles ( its load are !mselves also gr\nd smoo? & scrat*$4 ,s9ce ?is "w c be done by no o!r ag5t1 we mu/ conclude t ! nor!a/]n "p ( our own cont95t 0 cov]$ 9 ! rec5t pa/ by glaci] ice1 z ,gre5l& is to-day4 ,valley ,glaci]s ,! "w ( glaci] ice c be mo/ conv5i5tly /udi$ 9 ! sep>ate ice /reams :i* creep d[n m\nta9 valleys 9 _m regions su* z ,alaska1 ! we/]n m\nta9s ( ! ,unit$ ,/ates & ,canada1 ! ,himalayas1 & ! ,alps4 ,z ! glaci]s ( ! ,alps h be5 /udi$ long] & m ?or\ghly ?an any o!rs1 we %all describe !m 9 "s detail z examples ( valley glaci]s 9 all p>ts ( ! _w4 ,conditions ( glaci] =mation4 ,! condition ( ! great accumulation ( sn[ to :i* glaci]s are due--t m or less ( ea* w9t]'s sn[ %\ld be left ov] unmelt$ & unevaporat$ to ! next--is fully met 9 ! ,alps4 ,!re is abundant moi/ure br\ght by ! w9ds f neighbor+ seas4 ,! curr5ts ( moi/ air driv5 up ! m\nta9 slopes are cool$ by _! own expansion z !y rise1 & ! moi/ure :i* !y conta9 is cond5s$ at a temp]ature at or bel[ #cb ,f41 & !re=e is precipitat$ 9 ! =m ( sn[4 ,! summ]s are cool & _! heat does n suffice to completely melt ! heavy sn[ ( ! prec$+ w9t]4 ,on ! ,alps ! sn[ l9e--! l[] limit ( p]man5t sn[--is drawn at ab\t eight ?\s& five hundr$ feet above sea level4 ,above ! sn[ l9e on ! slopes & cre/s1 :]e ^! are n too /eep1 ! sn[ lies ! ye> r\nd & ga!rs 9 valley heads to a dep? ( hundr$s ( feet4 ,illu/ration3 ,fig4 #ic4 ,glaci]s head+ 9 ,sn[-fill$ ,amphi!at]s1 ! ,alps ,illu/ration3 ,fig4 #id4 ,b]gs*rund ( a ,glaci] 9 ,colorado ,?is is b a small fraction ( ! ?ickness to :i* sn[ w\ld be pil$ on ! ,alps 7 x n con/antly be+ dra9$ away4 ,bel[ ! sn[ fields :i* mantle ! heights ! m\nta9 valleys are occupi$ by glaci]s :i* ext5d z mu* z a v]tical mile bel[ ! sn[ l9e4 ,! pres5ce 9 ! mid/ ( =e/s & mead[s & cultivat$ fields ( ^! tongues ( ice1 ev] melt+ & yet f ye> to ye> los+ none ( _! bulk1 proves t _! loss is made good 9 ! only possible way4 ,!y are f$ by sn[ fields above1 ^: surplus ( sn[ !y dra9 away 9 ! =m ( ice4 ,! pres5ce ( glaci]s bel[ ! sn[ l9e is a cle> pro( t1 rigid & motionless z !y appe>1 glaci]s really are 9 con/ant motion d[n valley4 ,! nv field4 ,! head ( an ,alp9e valley occupi$ by a glaci] is commonly a broad amphi!at] deeply fill$ ) sn[ 7,fig4 #ic74 ,great peaks t[] above x1 & sn[y slopes rise on ei!r side on ! flanks ( m\nta9 spurs4 ,f ^! heights fi]ce w9ds drift ! sn[s into ! amphi!at]1 & avalan*es p\r 9 _! torr5ts ( sn[ & wa/e4 ,! sn[ ( ! amphi!at] is l t ( drifts 9 late w9t] aft] _m successive ?aws & freez+s4 ,x is made ( h>d gra9s & pellets & is call$ nv4 ,b5ea? ! surface ( ! nv field & at its outlet ! granul> nv has be5 compact$ to a mass ( por\s cry/all9e ice4 ,sn[ has be5 *ang$ to nv1 & nv to glacial ice1 bo? by pressure1 :i* drives ! air f ! int]spaces ( ! sn[flakes1 & also by successive melt+s & freez+s1 mu* z a sn[ball is pack$ 9 ! w>m h& & becomes froz5 to a ball ( ice4 ,illu/ration3 ,fig4 #ie4 ,sea ,wall ( ! ,muir ,glaci]1 ,alaska ,! b]gs*rund4 ,! nv is 9 sl[ motion4 ,x breaks itself loose f ! ?9n] sn[s ab\t x1 too %all[ to %>e its motion1 & f ! rock rim :i* surr\nds x1 =m+ a deep fissure call$ ! b]gs*rund1 sometimes a score & m feet wide 7,fig4 #id74 ,size ( glaci]s4 ,! ice /reams ( ! ,alps v>y 9 size accord+ to ! am\nt ( precipitation & ! area ( ! nv fields :i* !y dra94 ,! l>ge/ ( ,alp9e glaci]s1 ! ,alets*1 is ne>ly t5 miles long & has an av]age wid? ( ab\t a mile4 ,! ?ickness ( "s ( ! glaci]s ( ! ,alps is z mu* z a ?\s& feet4 ,giant glaci]s m ?an twice ! l5g? ( ! longe/ 9 ! ,alps occur on ! s\? slope ( ! ,himalaya ,m\nta9s1 :i* receive frequ5t precipitations ( sn[ f moi/ w9ds f ! ,indian ,ocean4 ,! be/ kn[n ( ! _m imm5se glaci]s ( ,alaska1 ! ,muir1 has an area ( ab\t eight hundr$ squ>e miles 7,fig4 #ie74 ,illu/ration3 ,fig4 #if4 ,diagram %[+ ,movem5t ( ,r[ ( ,/akes a1 set 9 a direct l9e across ! surface ( a glaci]2 b1 c1 & d1 successive lat] positions ( ! /akes ,illu/ration3 ,fig4 #ig4 ,diagram %[+ ,movem5t ( ,v]tical ,r[ ( ,/akes a1 set on side ( glaci] ,glaci] motion4 ,! motion ( ! glaci]s ( ! ,alps seldom exce$s "o or two feet a day4 ,l>ge glaci]s1 because ( ! enorm\s pressure ( _! weight & because ( less m>g9al resi/ance1 move fa/] ?an small ones4 ,! ,muir advances at ! rate ( sev5 feet a day1 & "s ( ! l>g] tide glaci]s ( ,gre5l& are report$ to move at ! exceptional rate ( fifty feet & m 9 ! same "t4 ,glaci]s move fa/] by day ?an by night1 & 9 summ] ?an 9 w9t]4 ,o!r laws ( glaci] motion may be discov]$ by a /udy ( ,figures #if & #ig4 ,x is important to rememb] t glaci]s d n slide bodily ov] _! b$s1 b urg$ by gravity move sl[ly d[n valley 9 some:at ! same way z w\ld a /ream ( ?ick mud4 ,al?\gh small pieces ( ice are brittle1 ! l>ge mass ( granul> ice :i* composes a glaci] acts z a visc\s sub/ance4 ,illu/ration3 ,fig4 #ih4 ,crevasses ( a ,glaci]1 ,canada ,crevasses4 ,slight *anges ( slope 9 ! glaci] b$1 & ! diff]5t rates ( motion 9 diff]5t p>ts1 produce t5sions "u :i* ! ice cracks & op5s 9 great fissures call$ crevasses4 ,at an abrupt desc5t 9 ! b$ ! ice is %att]$ into great fragm5ts1 :i* unite aga9 bel[ ! icefall4 ,crevasses are op5$ on l9es at "r angles to ! direction ( ! t5sion4 ,transv]se crevasses are due to a convexity 9 ! b$ :i* /ret*es ! ice l5g?wise 7,fig4 #ii74 ,m>g9al crevasses are direct$ up/ream & inw>ds2 radial crevasses are f\nd :]e ! ice /ream deploys f "s n>r[ valley & spreads ^u "s m op5 space4 ,:at is ! direction ( ! t5sion :i* causes ea* & to :at is x due8 7,figs4 #ajj & #aja74 ,illu/ration3 ,fig4 #ii4 ,longitud9al ,section ( a ,portion ( a ,glaci]1 %[+ ,trav]se ,crevasses ,illu/ration3 ,fig4 #ajj4 ,map view ( ,m>g9al ,crevasses ,illu/ration3 ,fig4 #aja4 ,! ,rhone ,glaci]1 %[+ ,radial ,crevasses1 ! ,alps ,illu/ration3 ,fig4 #ajb4 ,map ,view ( ! ,junction ( ,two ,bran*es ( a ,glaci] ,! mora9es are repres5t$ by brok5 l9es ,lat]al & m$ial mora9es4 ,! surface ( a glaci] is /rip$ l5g?wise by long d>k b&s ( rock debris4 ,^? 9 ! c5t] are call$ ! m$ial mora9es4 ,! "o on ei!r m>g9 is a lat]al mora9e1 & is cle>ly =m$ ( wa/e :i* has fall5 on ! edge ( ! ice f ! valley slopes4 ,a m$ial mora9e _c be =m$ 9 ?is way1 s9ce no rock fragm5ts c fall s f> out f ! sides4 ,b foll[+ x up ! glacial /ream1 "o f9ds t a m$ial mora9e takes its beg9n+ at ! junction ( ! glaci] & "s tribut>y & is =m$ by ! union ( _! two adjac5t lat]al mora9es 7,fig4 #ajb74 ,ea* bran* ?us adds a m$ial mora9e1 & by c\nt+ ! numb] ( m$ial mora9es ( a trunk /ream "o may le>n ( h[ _m bran*es x is compos$4 ,illu/ration3 ,fig4 #ajc4 ,cross ,section ( a ,glaci] %[+ ,lat]al ,mora9es l1 l1 & ,m$ial ,mora9es m1 m ,surface mora9es appe> 9 ! l[] c\rse ( ! glaci] z ridges1 :i* may rea* ! exceptional height ( "o hundr$ feet4 ,! bulk ( su* a ridge is ice4 ,x has be5 protect$ f ! sun by ! v5e] ( mora9e /uff2 :ile ! glaci] surface on ei!r side has melt$ d[n at lea/ ! di/ance ( ! height ( ! ridge4 ,9 summ] ! l[]+ ( ! glacial surface by melt+ goes on rapidly4 ,9 ,swiss glaci]s x has be5 e/imat$ t ! av]age l[]+ ( ! surface by melt+ & evaporation am\nts to t5 feet a ye>4 ,z a mora9e ridge gr[s high] & m /eep by ! l[]+ ( ! surface ( ! surr\nd+ ice1 ! /ones ( its cov] t5d to slip d[n its sides4 ,?us mora9es broad51 until ne> ! t]m9us ( a glaci] !y may coalesce 9 a wide field ( /ony wa/e4 ,illu/ration3 ,fig4 #ajd4 ,glaci] ) ,m$ial ,mora9es1 ! ,alps ,is ! ice mov+ f or t[>ds ! obs]v]8 ,englacial drift4 ,?is "n is appli$ to :atev] debris is c>ri$ )9 ! glaci]4 ,x consi/s ( rock wa/e fall5 on ! nv & !re buri$ by accumulations ( sn[1 & ( t engulf$ 9 ! glaci] :]e crevasses h op5$ b5ea? a surface mora9e4 ,z ! surface ( ! glaci] is l[]$ by melt+1 m or less englacial drift is br\ght aga9 to op5 air1 & ne> ! t]m9us x may help to bury ! ice f view b5ea? a %eet ( debris4 ,! gr\nd mora9e4 ,! drift dragg$ along at ! glaci]'s base & lodg$ b5ea? x is kn[n z ! gr\nd mora9e4 ,"p ( ! mat]ial ( x has fall5 d[n deep crevasses & "p has be5 torn & worn f ! glaci]'s b$ & banks4 ,:ile ! /ones ( ! surface mora9es rema9 z angul> z :5 !y lodg$ on ! ice1 _m ( ^? ( ! gr\nd mora9e h be5 blunt$ on ! edges & facet$ & scrat*$ by be+ gr\nd aga9/ "o ano!r & ! rocky b$4 ,9 glaci]s su* z ^? ( ,gre5l&1 ^: basal lay]s are well load$ ) drift & ^: surface lay]s are ne>ly clean1 diff]5t lay]s h diff]5t rates ( motion1 accord+ to ! am\nt ( drift ) :i* !y are clogg$4 ,"o lay] glides ov] ano!r1 & ! /ones inset 9 ea* are gr\nd & smoo!d & scrat*$4 ,usually ! sides ( glaciat$ pebbles are m worn ?an ! ends1 & ! scrat*es ^u !m run ) ! long] axis ( ! /one4 ,:y8 ,! t]m9al mora9e4 ,z a glaci] is 9 con/ant motion1 x br+s to its end all ( its load except su* p>ts ( ! gr\nd mora9e z may f9d p]man5t lodgm5t b5ea? ! ice4 ,:]e ! glaci] front rema9s = "s "t at "o place1 !re is =m$ an accumulation ( drift kn[n z ! t]m9al mora9e4 ,9 valley glaci]s x is %ap$ by ! ice front to a cresc5t ^: convex side is d[n/ream4 ,"s ( ! pebbles ( ! t]m9al mora9e are angul>1 & "s are facet$ & scor$1 ! latt] hav+ come by ! h>d road ( ! gr\nd mora9e4 ,! mat]ial ( ! dump is = ! mo/ "p unsort$1 ?\gh ! wat] ( ! melt+ ice may f9d opportunity to leave pat*es ( /ratifi$ s&s & gravels 9 ! mid/ ( ! un/ratifi$ mass ( drift1 & ! f9] mat]ial is 9 places wa%$ away4 ,illu/ration3 ,fig4 #aje4 ,t]m9al ,mora9e ( a ,glaci] 9 ,montana ,! ice has melt$ back f ! mora9ic ridge on ! left & is build+ ano!r on ! "r4 ,! holl[ betwe5 ! ridges is occupi$ by a lakelet4 ,glaci] dra9age4 ,! t]m9al mora9e is commonly brea*$ by a consid]able /ream1 :i* issues f b5ea? ! ice by a tunnel ^: portal has be5 enl>g$ to a beautiful ar*way by melt+ 9 ! sun & ! w>m air 7,fig4 #ajg74 ,! /ream is gray ) silt & load$ ) s& & gravel wa%$ f ! gr\nd mora9e4 ,glaci] milk ! ,swiss call ?is muddy wat]1 ! gray color ( ^: silt proves x rock fl\r fre%ly gr\nd by ! ice f ! unoxidiz$ s\nd rock ( its b$1 ! mud ( /reams be+ yell[i% :5 x is wa%$ f ! oxidiz$ mantle ( wa/e4 ,s9ce glacial /reams are well load$ ) wa/e due to vigor\s ice erosion1 ! valley 9 front ( ! glaci] is commonly aggrad$ to a broad1 flat floor4 ,^! outwa% deposits are kn[n z valley drift4 ,illu/ration3 ,fig4 #ajf4 ,heavy ,mora9e ab\t ! ,t]m9us ( a ,glaci] 9 ! ,rocky ,m\nta9s ( ,canada ,acc\nt = ! fact t ! mora9ic ridge rises consid]ably above ! surface ( ! ice ,! s& br\ght out by /reams f b5ea? a glaci] diff]s f riv] s& 9 t x consi/s ( fre%ly brok5 angul> gra9s4 ,:y8 ,! /ream d]ives its wat] *iefly f ! surface melt+ ( ! glaci]4 ,z ! ice is t\*$ by ! rays ( ! morn+ sun 9 summ]1 wat] ga!rs 9 pools1 & rills trickle & unite 9 brooklets :i* melt & cut %all[ *annels 9 ! blue ice4 ,! c\rse ( ^! /reams is %ort4 ,soon !y plunge into deep wells cut by _! :irl+ wat]s :]e "s crevasse has begun to op5 across _! pa?4 ,^! wells lead into *amb]s & tunnels by :i* soon] or lat] _! wat]s f9d way to ! rock floor ( ! valley & !re unite 9 a subglacial /ream4 ,illu/ration3 ,fig4 #ajg4 ,subglacial ,/ream ,issu+ f ,tunnel 9 ! ,ice1 ,norway ,! l[] limit ( glaci]s4 ,! glaci]s ( a region d n by any means end at a uni=m height above sea level4 ,ea* t]m9ates :]e its supply is balanc$ by melt+4 ,^? !re=e :i* are f$ by ! l>ge/ & deepe/ nvs & ^? also :i* are be/ protect$ f ! sun by a nor?w>d exposure or by ! dep? ( _! inclos+ valleys fl[ to l[] levels ?an ^? ^: supply is less & ^: exposure to ! sun is great]4 ,a s]ies ( cold1 moi/ ye>s1 ) an abundant sn[fall1 causes glaci]s to ?ick5 & advance2 a s]ies ( w>m1 dry ye>s causes !m to )] & melt back4 ,! v>iation 9 glaci]s is n[ c>efully obs]v$ 9 _m p>ts ( ! _w4 ,! ,muir glaci] has retreat$ two miles 9 tw5ty ye>s4 ,! glaci]s ( ! ,swiss ,alps are n[ = ! mo/ "p melt+ back1 al?\gh a well-kn[n glaci] ( ! ea/]n ,alps1 ! ,v]nagt1 advanc$ five hundr$ feet 9 ! ye> #aijj1 & 0 !n pl[+ up its t]m9al mora9e4 ,h[ soon w\ld y expect a glaci] to advance aft] its nv fields h be5 swoll5 ) unusually heavy sn[s1 z comp>$ ) ! "t ne$$ = ! flood ( a l>ge riv] to rea* its m\? aft] heavy ra9s ^u its headwat]s8 ,illu/ration3 ,fig4 #ajh4 ,a ,glaci] ,table ,on ! surface ( glaci]s 9 summ] "t "o may (t5 see l>ge /ones support$ by pill>s ( ice sev]al feet 9 height 7,fig4 #ajh74 ,^! glaci] tables commonly slope m or less /rongly to ! s\?1 & ?us may be us$ to indicate r\ghly ! po9ts ( ! compass4 ,c y expla9 _! =mation & ! direction ( _! slope8 ,on ! o!r h&1 a small & ?9 /one1 or a pat* ( du/1 ly+ on ! ice1 t5ds to s9k a few in*es into x4 ,:y8 ,9 :at respects is a valley glaci] l a m\nta9 /ream :i* fl[s out ^u des]t pla9s8 ,two conflu5t glaci]s d n m+le _! curr5ts z d two conflu5t riv]s4 ,:at *>act]i/ics ( surface mora9es prove ?is fact8 ,:at effect w\ld y expect ! laws ( glaci] motion to h on ! slant ( ! sides ( transv]se crevasses8 ,illu/ration3 ,fig4 #aji4 ,map ( ,malasp9a ,glaci]1 ,alaska ,a trunk glaci] has f\r m$ial mora9es4 ,( h[ _m tribut>ies is x compos$8 ,illu/rate by diagram4 ,/ate all ! evid5ces :i* y h f\nd t glaci]s move4 ,if a glaci] melts back ) occasional pauses up a valley1 :at records are left ( its retreat8 ,illu/ration3 ,fig4 #aaj4 ,outwa% ,pla91 ! ,delta ( ! ,yahtse ,riv]1 ,alaska ,pi$mont ,glaci]s ,! ,malasp9a glaci]4 ,pi$mont 7foot ( ! m\nta97 glaci]s are1 z ! "n implies1 ice fields =m$ at ! foot ( m\nta9s by ! conflu5ce ( valley glaci]s4 ,! ,malasp9a glaci] ( ,alaska1 ! typical glaci] ( ?is k9d1 is sev5ty miles wide & /ret*es = ?irty miles f ! foot ( ! ,m\nt ,sa9t ,elias range to ! %ore ( ! ,pacific ,ocean4 ,! valley glaci]s :i* unite & spread to =m ?is lake ( ice lie above ! sn[ l9e & _! mora9es are conceal$ b5ea? nv4 ,! c5tral area ( ! ,malasp9a is also free f debris2 b on ! out] edge l>ge quantities ( englacial drift are expos$ by surface melt+ & =m a belt ( mora9ic wa/e a few feet ?ick & sev]al miles wide1 cov]$ 9 "p ) a luxuriant =e/1 b5ea? :i* ! ice is 9 places "o ?\s& feet 9 dep?4 ,! glaci] "h is practically /agnant1 & lakes a few hundr$ y>ds across1 :i* c\ld n exi/ 7 ! ice 9 motion & brok5 ) crevasses1 ga!r on _! b$s sort$ wa/e f ! mora9e4 ,! /reams :i* dra9 ! glaci] h cut _! c\rses 9 englacial & subglacial tunnels2 none fl[ = any di/ance on ! surface4 ,! l>ge/1 ! ,yahtse ,riv]1 issues f a high ar*way 9 ! ice1--a muddy torr5t "o hundr$ feet wide & tw5ty feet deep1 load$ ) s& & /ones :i* x deposits 9 a broad outwa% pla9 7,fig4 #aaj74 ,:]e ! ice has retreat$ f ! sea !re is left a hummocky drift %eet ) holl[s fill$ ) lakelets4 ,^! deposits help to expla9 simil> hummocky regions ( drift & simil> pla9s ( co>se1 wat]-laid mat]ial (t5 f\nd 9 ! drift-cov]$ area ( ! nor!a/]n ,unit$ ,/ates4 ,! ,geological ,"w ,( ,glaci] ,ice ,! sluggi% glaci] mu/ d its "w 9 a diff]5t way f ! agile riv]4 ,! m\nta9 /ream is swift & small1 & its *annel occupies b a small portion ( ! valley4 ,! glaci] is sl[ & big2 its rate ( motion may be less ?an a million? ( t ( runn+ wat] ov] ! same declivity1 & its bulk is proportionately l>ge & fills ! valley to great dep?4 ,moreov]1 glaci] ice is a solid body pla/ic "u sl[ly appli$ /resses1 :ile ! wat] ( riv]s is a nimble fluid4 ,transportation4 ,valley glaci]s diff] f riv]s z c>ri]s 9 t !y float ! major "p ( _! load ^u _! surface1 transport+ ! heavie/ b[ld] z easily z a gra9 ( s&2 :ile /reams pu% & roll mu* ( _! load along _! b$s1 & _! p[] ( transport+ wa/e dep5ds solely ^u _! velocity4 ,! am\nt ( ! surface load ( glaci]s is limit$ only by ! am\nt ( wa/e receiv$ f ! m\nta9 slopes above !m4 ,! mov+ floor ( ice /ret*$ high across a valley sweeps along z lat]al mora9es mu* ( ! wa/e :i* a m\nta9 /ream w\ld let accumulate 9 talus & alluvial cones4 ,:ile a valley glaci] c>ries mu* ( its load on top1 an ice %eet1 su* z t ( ,gre5l&1 is free f surface debris1 except :]e mora9es trail away f "s nunatak4 ,if at its edge x breaks into sep>ate glaci]s :i* dra9 d[n m\nta9 valleys1 ^! tongues ( ice w c>ry ! selvages ( wa/e common to valley glaci]s4 ,bo? ice %eets & valley glaci]s drag on l>ge quantities ( rock wa/e 9 _! gr\nd mora9es4 ,/ones transport$ by glaci]s are sometimes call$ erratics4 ,su* are ! b[ld]s ( ! drift ( our nor!rn /ates4 ,erratics may be set d[n 9 an insecure position on ! melt+ ( ! ice4 ,deposit4 ,little ne$ be add$ "h to :at has already be5 said ( gr\nd & t]m9al mora9es4 ,all /rictly glacial deposits are un/ratifi$4 ,! load laid d[n at ! end ( a glaci] 9 ! t]m9al mora9e is loose 9 texture1 :ile ! drift lodg$ b5ea? ! glaci] z gr\nd mora9e is (t5 an extremely d5se1 /ony clay1 hav+ be5 compact$ "u ! pressure ( ! ov]rid+ ice4 ,erosion4 ,a glaci] erodes its b$ & banks 9 two ways1--by abrasion & by pluck+4 ,! rock b$ ov] :i* a glaci] has mov$ is se5 9 places to h be5 abrad$1 or gr\nd away1 to smoo? surfaces :i* are m>k$ by long1 /raight1 p>allel scor+s align$ ) ! l9e ( movem5t ( ! ice & v>y+ 9 size f hair l9es & co>se scrat*es to exceptional furr[s sev]al feet deep4 ,cle>ly ?is "w has be5 accompli%$ by means ( ! %>p s&1 ! pebbles1 & ! l>g] /ones ) :i* ! base ( ! glaci] is inset1 & :i* x holds 9 a firm grasp z runn+ wat] _c4 ,h>d & f9e-gra9$ rocks1 su* z granite & qu>tzite1 are (t5 n only gr\nd d[n to a smoo? surface b are also highly poli%$ by means ( f9e rock fl\r worn f ! glaci] b$4 ,9 o!r places ! b$ ( ! glaci] is r\gh & torn4 ,! rocks h be5 disrupt$ & _! fragm5ts h be5 c>ri$ away1--a process kn[n z pluck+4 ,mov+ "u imm5se pressure ! ice %att]s ! rock1 breaks (f projections1 presses into crevices & w$ges ! rocks ap>t1 dislodges ! blocks into :i* ! rock is divid$ by jo9ts & b$d+ planes1 & freez+ fa/ to ! fragm5ts drags !m on4 ,9 ?is "w ! freez+ & ?aw+ ( subglacial wat]s 9 any cracks & crevices ( ! rock no d\bt play an important "p4 ,pluck+ occurs especially :]e ! b$ rock is weak because ( close jo9t+4 ,! product ( pluck+ is b[ld]s1 :ile ! product ( abrasion is f9e rock fl\r & s&4 ,is ! gr\nd mora9e ( ,figure #hg due *iefly to abrasion or to pluck+8 ,illu/ration3 ,fig4 #aaa4 ,ro*es ,m\tonns1 ,bronx ,p>k1 ,new ,york ,ro*es m\tonnes & r\nd$ hills4 ,! prom95ces left betwe5 ! holl[s due to pluck+ are commonly gr\nd d[n & r\nd$ on ! /oss side1--! side f :i* ! ice advances1--& sometimes on ! opposite1 ! lee side1 z well4 ,9 ?is way ! b$ rock (t5 comes to h a bill[y surface kn[n z ro*es m\tonnes 7%eep rocks74 ,hills ov]ridd5 by an ice %eet (t5 h simil>ly r\nd$ cont\rs on ! /oss side1 :ile on ! lee side !y may be craggy1 ei!r because ( pluck+ or because "h !y h be5 less worn f _! initial pr(ile 7,fig4 #aab74 ,! direction ( glaci] movem5t4 ,! direction ( ! fl[ ( vani%$ glaci]s & ice %eets is record$ bo? 9 ! diff]5ces j m5tion$ 9 ! pr(iles ( ov]ridd5 hills & also 9 ! m9ute details ( ! glaci] trail4 ,fl9t nodules or o!r small prom95ces 9 ! b$ rock are f\nd m worn on ! /oss ?an on ! lee side1 :]e inde$ !y may h a l[ cone ( rock protect$ by !m f abrasion4 ,cavities1 on ! o!r h&1 h _! edges worn on ! lee side & left %>p ^u ! /oss4 ,surfaces worn & torn 9 ! ways :i* we h m5tion$ are said to be glaciat$4 ,b x mu/ n be suppos$ t a glaci] ev]y:]e glaciates its b$4 ,al?\gh 9 places x acts z a rasp or z a pick1 9 o!rs1 & especially :]e its pressure is lea/1 z ne> ! t]m9us1 x moves ov] its b$ 9 ! mann] ( a sl$4 ,in/ances are kn[n :]e glaci]s h advanc$ ov] deposits ( s& & gravel )\t di/urb+ !m to any notable degree4 ,l a riv]1 a glaci] does n ev]y:]e erode4 ,9 places x leaves its b$ undi/urb$ & 9 places aggrades x by deposits ( ! gr\nd mora9e4 ,illu/ration3 ,fig4 #aab4 ,a ,glaciat$ ,hill1 ,norway4 ,%>p ,wea!r$ ,m\nta9 ,peaks 9 ! ,di/ance ,cirques4 ,valley glaci]s commonly head z we h se51 9 broad amphi!at]s deeply fill$ ) sn[ & ice4 ,on m\nta9s n[ de/itute ( glaci]s1 b ^: glaciation %[s t !y h support$ glaci]s 9 ! pa/1 !re are f\nd simil> cresc5tic holl[s ) high1 precipit\s walls & glaciat$ floors4 ,_! floors are (t5 bas9$ & hold lakelets ^: deep & quiet wat]s reflect ! %elt]+ ramp>ts ( rugg$ rock :i* t[] f> above !m4 ,su* m\nta9 holl[s are t]m$ cirques4 ,z a p[]ful spr+ we>s back a recess 9 ! valley side :]e x dis*>ges1 s ! f\nta9 head ( a glaci] gradually we>s back a cirque4 ,9 its sl[ movem5t ! nv field broadly sc\rs its b$ to a flat or bas9$ floor4 ,mean:ile ! sides ( ! valley head are /eep5$ & driv5 back to precipit\s walls4 ,= 9 w9t] ! crevasse ( ! b]gs*rund :i* surr\nds ! nv field is fill$ ) sn[ & ! nv is froz5 fa/ to ! rocky sides ( ! valley4 ,9 e>ly summ] ! nv te>s itself free1 dislodg+ & remov+ any loos5$ blocks1 & ! op5 fissure ( ! b]gs*rund all[s fro/ & o!r ag5cies ( wea!r+ to attack ! unprotect$ rock4 ,z cirques are ?us =m$ & enl>g$ ! peaks b5ea? :i* !y lie are %>p5$1 & ! m\nta9 cre/s are scallop$ & cut back f ei!r side to knife-edg$ ridges 7,figs4 #aac & #ic74 ,illu/ration3 ,fig4 #aac4 ,cirques1 ,si]ra ,nevada ,m\nta9s ,9 ! we/]n m\nta9s ( ! ,unit$ ,/ates _m cirques1 n[ empty ( nv & glaci] ice1 & kn[n locally z bas9s1 te/ify to ! fact t 9 rec5t times ! sn[ l9e /ood b5ea? ! levels ( _! floors1 & ?us f> bel[ its pres5t altitude4 ,illu/ration3 ,fig4 #aad4 ,a ,glaci] ,tr\gh1 ,montana ,glaci] tr\ghs4 ,! *annel worn to accommodate ! big & clumsy glaci] diff]s m>k$ly f ! riv] valley cut z ) a saw by ! n>r[ & flexible /ream & wid5$ by ! wea!r & ! wa% ( ra9s4 ,! valley glaci] may easily be f "o ?\s& to ?ree ?\s& feet deep & f "o to ?ree miles wide4 ,su* a pond]\s bulk ( sl[ly mov+ ice does n readily adapt itself to %>p turns & a n>r[ b$4 ,by sc\r+ & pluck+ all resi/+ edges x develops a fitt+ *annel ) a wide1 flat floor1 & /eep1 smoo? sides1 above :i* are se5 ! wea!r$ slopes ( /ream-worn m\nta9 valleys4 ,s9ce ! trunk glaci] requires a deep] *annel ?an d its bran*es1 ! b$ ( a bran* glaci] ent]s ! ma9 tr\gh at "s di/ance above ! floor ( ! latt]1 al?\gh ! surface ( ! two ice /reams may be accordant4 ,glaci] tr\ghs c be /udi$ be/ :]e l>ge glaci]s h rec5tly melt$ completely away1 z is ! case 9 _m valleys ( ! m\nta9s ( ! we/]n ,unit$ ,/ates & ( c5tral & nor!rn ,europe 7,fig4 #aad74 ,! typical glaci] tr\gh1 z %[n 9 su* examples1 is ,u-%ap$1 ) a broad1 flat floor1 & high1 /eep walls4 ,its walls are little brok5 by project+ spurs & lat]al rav9es4 ,x is z if a ,v-valley cut by a riv] _h aft]w>ds be5 g\g$ deep] ) a gigantic *isel1 wid5+ ! floor to ! wid? ( ! *isel blade1 cutt+ back ! spurs1 & smoo?+ & /eep5+ ! sides4 ,a riv] valley c\ld only be z wide-floor$ z ?is aft] x _h long be5 worn d[n to grade4 ,illu/ration3 ,fig4 #aae ,lynn ,canal1 ,alaska1 a ,fjord ,b ! floor ( a glaci] tr\gh may n be grad$2 x is (t5 int]rupt$ by irregul> /eps p]haps hundr$s & ev5 a ?\s& feet 9 height1 ov] :i* ! /ream t n[ dra9s ! valley tumbles 9 wat]falls4 ,rea*es betwe5 ! /eps are (t5 bas9$4 ,lakelets may occupy holl[s excavat$ 9 solid rock1 & o!r lakes may be held beh9d t]m9al mora9es left z dams across ! valley at pauses 9 ! retreat ( ! glaci]4 ,fjords are glaci] tr\ghs n[ occupi$ 9 "p or :olly by ! sea1 ei!r because !y 7 excavat$ by a tide glaci] to _! pres5t dep? bel[ sea level1 or because ( a subm]g5ce ( ! l&4 ,_! *>act]i/ic =m is t ( a long1 deep1 n>r[ bay ) /eep rock walls & bas9$ floor 7,fig4 #aae74 ,fjords are f\nd only 9 regions :i* h suff]$ glaciation1 su* z ,norway & ,alaska4 ,illu/ration3 ,fig4 #aaf4 ,a1 ,v-,riv] ,valley1 ) ,valley ( ,tribut>y jo9+ x a ,accordant ,level2 ,b1 ! ,same *ang$ aft] ,long ,glaciation to a ,tr\gh ) ,hang+ ,valley ,hang+ valleys4 ,^! are lat]al valleys :i* op5 on _! ma9 valley "s di/ance above its floor4 ,!y are conspicu\s features ( glaci] tr\ghs f :i* ! ice has vani%$2 = ! trunk glaci] 9 wid5+ & deep5+ its *annel cut its b$ bel[ ! bottoms ( ! lat]al valleys 7,fig4 #aaf74 ,s9ce ! m\?s ( hang+ valleys are susp5d$ on ! walls ( ! glaci] tr\gh1 _! /reams are compell$ to plunge d[n its /eep1 high sides 9 wat]falls4 ,"s ( ! l(tie/ & mo/ beautiful wat]falls ( ! _w leap f hang+ valleys1--among !m ! celebrat$ ,/aubba* ( ! ,laut]brunn5 valley ( ,switz]l&1 & ^? ( ! fjords ( ,norway & ,alaska 7,fig4 #aag74 ,illu/ration3 ,fig4 #aag4 ,hang+ ,valley on ! ,wall ( a ,fjord1 ,norway ,hang+ valleys are f\nd also 9 riv] gorges :]e ! small] tribut>ies h n be5 able to keep pace ) a /rong ma/] /ream 9 cutt+ d[n _! b$s4 ,9 ?is case1 h[ev]1 !y are a m>k ( extreme y\?2 =1 z ! trunk /ream approa*es grade & its velocity & p[] to erode its b$ decrease1 ! side /reams soon cut back _! falls & we> _! b$s at _! m\?s to a common level ) t ( ! ma9 riv]4 ,! ,gr& ,canyon ( ! ,colorado mu/ be reckon$ a "y valley4 ,at its base x n>r[s to sc>cely m ?an ! wid? ( ! riv]1 & yet its tribut>ies1 except ! v smalle/1 ent] x at a common level4 ,:y c\ld n a wide-floor$ valley1 su* z a glaci] tr\gh1 ) hang+ valleys op5+ ^u x1 be produc$ 9 ! normal developm5t ( a riv] valley8 ,! tr\ghs ( "y & ( mature glaci]s4 ,! features ( a glaci] tr\gh dep5d mu* on ! l5g? ( "t ! preexi/+ valley 0 occupi$ ) ice4 ,dur+ ! infancy ( a glaci]1 we may believe1 ! spurs ( ! valley :i* x fills are b little blunt$ & its b$ is b little brok5 by /eps4 ,9 y\? ! glaci] develops icefalls1 z a riv] 9 y\? develops wat]falls1 & its b$ becomes t]rac$ ) great /airs4 ,! mature glaci]1 l ! mature riv]1 has effac$ its falls & smoo!d its b$ to grade4 ,x has also worn back ! project+ spurs ( its valley1 mak+ itself a wide *annel ) smoo? sides4 ,! b$ ( a mature glaci] may =m a long bas91 s9ce x abrades mo/ 9 its upp] & middle c\rse1 :]e its weight & motion are ! greate/4 ,ne> ! t]m9us1 :]e weight & motion are ! lea/1 x erodes lea/1 & may in/ead deposit a %eet ( gr\nd mora9e1 mu* z a riv] builds a flood pla9 9 ! same "p ( its c\rse z x approa*es maturity4 ,! b$ ( a mature glaci] ?us t5ds to take ! =m ( a long1 relatively n>r[ bas91 across ^: l[] end may be /ret*$ ! dam ( ! t]m9al mora9e4 ,on ! disappe>ance ( ! ice ! bas9 is rill$ ) a long1 n>r[ lake1 su* z ,lake ,*elan 9 ,wa%+ton & _m ( ! lakes 9 ! ,highl&s ( ,scotl&4 ,pi$mont glaci]s app>5tly erode b little4 ,b5ea? _! lake-l expanse ( sluggi% or /agnant ice a broad %eet ( gr\nd mora9e is probably be+ deposit$4 ,cirques & glaciat$ valleys rapidly lose _! *>act]i/ic =ms aft] ! ice has )drawn4 ,! wea!r de/roys all smoo!d1 poli%$1 & scor$ surfaces :i* are n protect$ b5ea? glacial deposits4 ,! ov]-/eep5$ sides ( ! tr\gh are grad$ by l&slips1 by talus slopes1 & by alluvial cones4 ,mora9ic heaps ( drift are dissect$ & c>ri$ away4 ,hang+ valleys & ! irregul> b$ ( ! tr\gh are bo? worn d[n to grade by ! /reams :i* n[ occupy !m4 ,! l5g? ( "t s9ce ! retreat ( ! ice f a m\nta9 valley may ?us be e/imat$ by ! degree to :i* ! de/ruction ( ! *>act]i/ic features ( ! glaci] tr\gh has be5 c>ri$4 ,9 ,figure #ajd :at *>act]i/ics ( a glaci] tr\gh d y notice8 ,:at inf]5ce d y draw z to ! =m] ?ickness ( ! glaci]8 ,"n all ! evid5ces y w\ld expect to f9d to prove ! fact t 9 ! rec5t geological pa/ ! valleys ( ! ,alps conta9$ f> l>g] glaci]s ?an at pres5t1 & t on ! nor? ( ! ,alps ! ice /reams unit$ 9 a pi$mont glaci] :i* ext5d$ across ! pla9s ( ,switz]l& to ! sides ( ! ,jura ,m\nta9s4 ,! relative importance ( glaci]s & ( riv]s4 ,p[]ful z glaci]s are1 & m>k$ z are ! l& =ms :i* !y produce1 x is easy to exagg]ate _! geological importance z comp>$ ) riv]s4 ,"u pres5t climatic conditions !y are conf9$ to l(ty m\nta9s or pol> l&s4 ,pol> ice %eets are p]man5t only s long z ! l&s rema9 on :i* !y re/4 ,m\nta9 glaci]s c /ay only ! brief "t dur+ :i* ! ranges cont9ue "y & high4 ,z l(ty m\nta9s1 su* z ! ,selkirks & ! ,alps1 are l[]$ by fro/ & glaci] ice1 ! sn[fall w decrease1 ! l9e ( p]man5t sn[ w rise1 & z ! m\nta9 holl[s 9 :i* sn[ may ga!r are worn b5ea? ! sn[ l9e1 ! glaci]s mu/ disappe>4 ,"u pres5t climatic conditions ! "w ( glaci]s is !re=e bo? local & ( %ort duration4 ,illu/ration3 ,fig4 #aah4 ,longitud9al ,section ( a ,tide ,glaci] occupy+ a ,fjord & dis*>g+ ,iceb]gs ,dott$ ,l9e1 sea level ,ev5 ! glacial epo*1 dur+ :i* va/ ice %eets deposit$ drift ov] nor!a/]n ,nor? ,am]ica1 mu/ h be5 brief z well z rec5t1 = _m l(ty m\nta9s1 su* z ! ,rockies & ! ,alps1 /ill be> ! m>ks ( great glaci]s :i* !n fill$ _! valleys4 ,_h ! glacial epo* be5 long1 z ! e>? c\nts "t1 ^! m\nta9s w\ld h be5 worn l[ by ice2 _h ! epo* be5 remote1 ! m>ks ( glaciation w\ld already h be5 l>gely de/roy$ by o!r ag5cies4 ,on ! o!r h&1 riv]s are well-nigh univ]sally at "w ov] ! l& surfaces ( ! globe1 & ev] s9ce ! dry l& appe>$ !y h be5 con/antly engag$ 9 level+ ! cont95ts & 9 deliv]+ to ! seas ! wa/e :i* !re is built into ! /ratifi$ rocks4 ,iceb]gs4 ,tide glaci]s1 su* z ^? ( ,gre5l& & ,alaska1 are able to excavate _! b$s to a consid]able di/ance bel[ sea level4 ,f _! fronts ! buoyancy ( sea wat] raises & breaks away great masses ( ice :i* float out to sea z iceb]gs4 ,only ab\t "o sev5? ( a mass ( glaci] ice floats above ! surface1 & a b]g ?ree hundr$ feet high may be e/imat$ to h be5 deta*$ f a glaci] n less ?an two ?\s& feet ?ick :]e x met ! sea4 ,iceb]gs transport on _! long j\rneys :atev] drift !y may h c>ri$ :5 "p ( ! glaci]1 & scatt] x1 z !y melt1 ov] ! ocean floor4 ,9 ?is way pebbles torn by ! inl& ice f ! rocks ( ! int]ior ( ,gre5l& & glaciat$ dur+ _! c>riage 9 ! gr\nd mora9e are dropp$ at la/ among ! oozes ( ! bottom ( ! ,nor? ,atlantic4 ,,*apt] ,,vi ,,! ,,"w ,,( ,,! ,,w9d ,illu/ration3 ,fig4 #aai4 ,a s&y ,region 9 a ,des]t1 ! ,sah>a ,we are n[ to /udy ! geological "w ( ! curr5ts ( ! atmosph]e1 & to le>n h[ !y erode1 & transport & deposit wa/e z !y sweep ov] ! l&4 ,illu/rations ( ! w9d's "w are at h& 9 dry wea!r on any w9dy day4 ,cl\ds ( du/ are rais$ f ! /reet & driv5 along by ! gale4 ,"h ! roadway is swept b>e2 & !re1 9 %elt]$ places1 ! du/ settles 9 little w9dr[s4 ,! erosive p[] ( wa/e-lad5 curr5ts ( air is sugge/$ z ! %>p gra9s ( fly+ s& /+ "o's face or clatt] aga9/ ! w9d[4 ,9 ! c\ntry "o sometimes sees ! du/ :irl$ 9 cl\ds f dry1 pl[$ fields 9 spr+ & left 9 ! lee ( f5ces 9 small drifts resembl+ 9 =m ^? ( sn[ 9 w9t]4 ,! ess5tial conditions = ! w9d's conspicu\s "w are illu/rat$ 9 ^! simple examples2 !y are aridity & ! abs5ce ( vegetation4 ,9 humid climates ^! conditions are only r>ely & locally met2 = ! mo/ "p a ?ick gr[? ( vegetation protects ! moi/ soil f ! w9d ) a cov] ( leaves & /ems & a mattress ( int]lac+ roots4 ,b 9 arid regions ei!r vegetation is :olly lack+1 or scant gr[?s are f\nd huddl$ 9 deta*$ clumps1 leav+ int]spaces ( unprotect$ gr\nd 7,fig4 #aai74 ,"h1 too1 ! mantle ( wa/e1 :i* is =m$ *iefly "u ! action ( temp]ature *anges1 rema9s dry & loose = long p]iods4 ,little or no moi/ure is pres5t to cause its p>ticles to coh]e1 & !y are !re=e readily lift$ & drift$ by ! w9d4 ,transportation ,by ,! ,w9d ,9 ! des]t ! f9] wa/e is cont9ually swept to & fro by ! ev]-%ift+ w9d4 ,ev5 9 quiet wea!r ! air heat$ by contact ) ! hot s&s rises 9 :irls1 & ! du/ is lift$ 9 /ately columns1 sometimes z mu* z "o ?\s& feet 9 height1 :i* m>* sl[ly across ! pla94 ,9 /orms ! s& is driv5 along ! gr\nd 9 a cont9u\s %eet1 :ile ! air is till$ ) du/4 ,explor]s tell ( s& /orms 9 ! des]ts ( c5tral ,asia & ,africa1 9 :i* ! air gr[s murky & suffocat+4 ,ev5 at midday x may become d>k z night1 & no?+ c be he>d except ! ro> ( ! bla/ & ! :ir ( myriads ( gra9s ( s& z !y fly pa/ ! e>4 ,s& /orms are by no means uncommon 9 ! arid regions ( ! we/]n ,unit$ ,/ates4 ,9 a rec5t ye>1 six 7 report$ f ,yuma1 ,arizona4 ,tra9s on transcont95tal railways are occasionally blockad$ by drift+ s&1 & ! du/ sifts into clos$ pass5g] coa*es1 cov]+ ! seats & floors4 ,aft] su* a /orm ?irte5 c> loads ( s& 7 remov$ f ! plat=m ( a /ation on a we/]n railway4 ,du/ falls4 ,du/ laun*$ by upw>d-:irl+ w9ds on ! swift curr5ts ( ! upp] air is (t5 bl[n = hundr$s ( miles beyond ! arid region f :i* x 0 tak54 ,du/ falls f we/]n /orms are n unkn[n ev5 z f> ea/ z ! ,great ,lakes4 ,9 #ahif a black sn[ fell 9 ,*icago1 & 9 ano!r du/ /orm 9 ! same decade ! am\nt ( du/ c>ri$ 9 ! air ov] ,rock ,isl&1 ,ill41 0 e/imat$ at m ?an "o ?\s& tons to ! cubic mile4 ,illu/ration3 ,fig4 #abj4 ,a ,tract ( ,rocky ,des]t1 ,arabia ,by :at process h ^! rocks be5 brok5 up8 ,:y is f9] wa/e "h abs5t8 ,9 ,m>*1 #aija1 a cyclonic /orm c>ri$ va/ quantities ( du/ f ! ,sah>a nor?w>d across ! ,m$it]ranean to fall ov] s\!rn & c5tral ,europe4 ,on ,m>* #h? du/ /orms rag$ 9 s\!rn ,alg]ia2 two days lat] ! du/ fell 9 ,italy2 & on ! #aa? x _h rea*$ c5tral ,g]many & ,d5m>k4 ,x is e/imat$ t 9 ^! few days "o million eight hundr$ ?\s& tons ( wa/e 7 c>ri$ f nor!rn ,africa & deposit$ on ,european soil4 ,we may see f ^! examples ! importance ( ! w9d z an ag5t ( transportation1 & h[ va/ 9 ! aggregate are ! loads :i* x c>ries4 ,!re are /rik+ diff]5ces betwe5 air & wat] z c>ri]s ( wa/e4 ,riv]s fl[ 9 fix$ & n>r[ *annels to def9ite goals4 ,! *annelless /reams ( ! air sweep across broad areas1 &1 %ift+ ab\t cont9ually1 c>ry _! loads back & =?1 n[ 9 "o direction & n[ 9 ano!r4 ,w9d ,deposits ,! mantle ( wa/e ( des]ts is rapidly sort$ by ! w9d4 ,! co>s] rubbi%1 too heavy to be lift$ into ! air1 is left to /rew wide tracts ) residual gravels 7,fig4 #abj74 ,! s& d]iv$ f ! dis9tegration ( des]t rocks ga!rs 9 va/ fields4 ,ab\t "o eigh? ( ! surface ( ! ,sah>a is said to be ?us cov]$ ) drift+ s&4 ,9 des]t m\nta9s1 z ^? ( ,s9ai1 x lies l fields ( sn[ 9 ! high valleys bel[ ! %>p peaks4 ,on m level tracts x accumulates 9 seas ( s&1 sometimes1 z 9 ! des]ts ( ,arabia1 two hundr$ & m feet deep4 ,illu/ration3 ,fig4 #aba4 ,longitud9al ,dunes1 ,des]t ( ,nor?we/]n ,india ,scale1 #a 9 #c miles ,dunes4 ,! s& ?us accumulat$ by ! w9d is heap$ 9 wavelike hills call$ dunes4 ,9 ! des]t ( nor?we/]n ,india1 :]e ! preval5t w9d is ( great /r5g?1 ! s& is laid 9 longitud9al dunes1 i4e4 9 /ripes runn+ p>allel ) ! direction ( ! w9d2 b commonly dunes lie1 l ripple m>ks1 transv]se to ! w9d curr5t4 ,on ! w9dw>d side !y %[ a long1 g5tle slope1 up :i* gra9s ( s& c readily be mov$2 :ile to ! lee _! slope is frequ5tly z great z ! angle ( repose 7,fig4 #abb74 ,dunes ^: s&s are n fix$ by vegetation travel sl[ly ) ! w9d2 = _! mat]ial is ev] %ift$ =w>d z ! gra9s are driv5 up ! w9dw>d slope &1 fall+ ov] ! cre/1 are deposit$ 9 slant+ lay]s 9 ! quiet ( ! lee4 ,illu/ration3 ,fig4 #abb4 ,a ,transv]se ,dune1 ,sev5 ,mile ,bea*1 ,new ,j]sey ,acc\nt = ! diff]5ce ( slope 9 ! two sides ( ! dune4 ,is ! dune m>*+8 ,9 :at direction8 ,) :at effect8 ,d ! ridges ( ! ripple m>ks ^u ! dune ext5d along x or a?w>t x8 ,:y8 ,l riv] deposits1 w9d-bl[n s&s are /ratifi$1 s9ce !y are laid by curr5ts ( air v>y+ 9 int5sity1 & !re=e 9 transport+ p[]1 :i* c>ry n[ f9] & n[ co>s] mat]ials & lay !m d[n :]e _! velocity is *eck$ 7,fig4 #abc74 ,s9ce ! w9d v>ies 9 direction1 ! /rata dip 9 v>i\s directions4 ,!y also dip at v>i\s angles1 accord+ to ! incl9ation ( ! surface on :i* !y 7 laid4 ,illu/ration3 ,fig4 #abc4 ,/ratifi$ ,w9d-,bl[n ,s&s1 ,b]muda ,isl&s ,^! isl&s are made :olly ( lime/one1 ! product ( reef-build+ corals1 & ( lime f ! sea wat]4 ,! lime/one s& ( ! bea*es has be5 bl[n up into great dunes1 "s m ?an two hundr$ feet 9 height4 ,mu* ( ! loose dune s& has be5 *ang$ to firm rock by p]colat+ wat]s1 :i* h dissolv$ "s ( ! lime/one & deposit$ x aga9 z a cem5t betwe5 ! gra9s ,dunes occur n only 9 arid regions1 b also :]ev] loose s& lies unprotect$ by vegetation f ! w9d4 ,f ! bea*es ( sea & lake %ores ! w9d drives inl& ! surface s& left dry betwe5 tides & aft] /orms1 pil+ x 9 dunes :i* may invade =e/s & fields & bury villages b5ea? _! sl[ly advanc+ waves4 ,on flood pla9s dur+ summ] dr\ghts riv] deposits are (t5 work$ ov] by ! w9d2 ! s& is heap$ 9 hummocks & mu* ( ! f9e silt is caught & held by ! =e/s & grassy fields ( ! bord]+ hills4 ,illu/ration3 ,fig4 #abd4 ,cross ,section ( ,transv]se ,dune aft] ,rev]sal ( ,w9d ,r$raw diagram1 %[+ by dott$ l9e ! orig9al outl9e ( ! dune ,! s& ( %ore dunes diff]s little 9 composition & ! %ape ( its gra9s f t ( ! bea* f :i* x 0 d]iv$4 ,b 9 des]ts1 by ! long we> ( gra9 on gra9 z !y are bl[n hi!r & ?i!r by ! w9d1 all s(t m9]als are gr\nd to p[d] & ! s& comes to consi/ almo/ :olly ( smoo? r\nd grams ( h>d qu>tz4 ,illu/ration3 ,fig4 #abe4 ,dune ,s&s1 ,%ore ( ,lake ,mi*igan ,acc\nt = ! dead =e/1 = its lean+ tree trunks4 ,is ! lake %ore to ! "r or left8 ,:at has be5 ! hi/ory ( ! l&scape8 ,"s m>9e s&/ones1 su* z ! ,/4 ,pet] s&/one ( ! upp] ,mississippi valley1 are compos$ s entirely ( poli%$ sph]ules ( qu>tz t x has be5 believ$ by "s t _! gra9s 7 long bl[n ab\t 9 anci5t des]ts be=e !y 7 deposit$ 9 ! sea4 ,illu/ration3 ,fig4 #abf4 ,cresc5tic ,s& ,dunes1 ,valley ( ! ,columbia ,riv] ,did ! w9d :i* %ap$ !m bl[ f ! left or f ! "r8 ,du/ deposits4 ,z des]t s&s are compos$ almo/ :olly ( qu>tz1 we may ask :at has become ( ! s(t] m9]als ( :i* ! rocks ^: dis9tegration has suppli$ ! s& 7 9 "p1 & (t5 9 l>ge "p1 compos$4 ,! s(t] m9]als h be5 gr\nd to p[d]1 & little by little ! qu>tz s& also is worn by attrition to f9e du/4 ,yet du/ deposits are scant & few 9 great des]ts su* z ! ,sah>a4 ,! f9] wa/e is bl[n beyond its limits & laid 9 adjac5t oceans1 :]e x adds to ! muds & oozes ( _! floors1 & on bord]+ /eppes & =e/ l&s1 :]e x is b\nd fa/ by vegetation & sl[ly accumulates 9 deposits ( un/ratifi$ loose yell[ e>?4 ,! f9e wa/e ( ! ,sah>a has be5 id5tifi$ 9 dr$g+s f ! bottom ( ! ,atlantic ,ocean1 tak5 hundr$s ( miles f ! coa/ ( ,africa4 ,loess4 ,9 nor!rn ,*9a an area z l>ge z ,france is deeply cov]$ ) a yell[ pulv]ul5t e>? call$ loess 7,g]man1 loose71 :i* _m consid] a du/ deposit bl[n f ! great ,mongolian des]t ly+ to ! we/4 ,loess mantles ! rec5tly uplift$ m\nta9s to ! height ( eight ?\s& feet & desc5ds on ! pla9s ne>ly to sea level4 ,its texture & lack ( /ratification give x a v]tical cleavage2 h5ce x /&s 9 /eep cliffs on ! sides ( ! deep & n>r[ tr5*es :i* h be5 cut 9 x by /reams4 ,on loess hillsides 9 ,*9a are ?\s&s ( villages ^: eavelike dwell+s h be5 excavat$ 9 ?is s(t1 yet firm1 dry loam4 ,:ile du/ falls are common at ! pres5t "t 9 ?is region1 ! loess is n[ be+ rapidly d5ud$ by /reams1 & its yell[ silt gives "n to ! muddy ,hwang-ho 7,yell[ ,riv]71 & to ! ,yell[ ,sea1 ^: wat]s x discolors = scores ( miles f %ore4 ,w9d deposits bo? ( du/ & ( s& may be expect$ to conta9 ! rema9s ( l& %ells1 bits ( wood1 & bones ( l& animals1 te/ify+ to ! fact t !y 7 accumulat$ 9 op5 air & n 9 ! sea or 9 bodies ( fre% wat]4 ,w9d ,erosion ,illu/ration3 ,fig4 #abg4 ,w9d-,c>v$ ,rocks1 ,arizona ,s&-lad5 curr5ts ( air abrade & smoo? & poli% expos$ rock surfaces1 act+ 9 mu* ! same way z does ! jet ( /eam f$ ) %>p s&1 :i* is us$ 9 ! manufacture ( gr\nd glass4 ,inde$1 9 a s+le /orm at ,cape ,cod a plate glass ( a ligh?\se 0 s gr\nd by fly+ s& t its transp>5cy 0 de/roy$ & its removal made necess>y4 ,illu/ration3 ,fig4 #abh4 ,a ,w9d-,c>v$ ,pebble1 ,cape ,cod ,telegraph poles & wires :ett$ by w9d-bl[n s&s are de/roy$ )9 a few ye>s4 ,9 rocks ( unequal resi/ance ! h>d] p>ts are left 9 relief1 :ile ! s(t] are et*$ away4 ,?us 9 ! pass ( ,san ,b]n>d9o1 ,cal41 ?r\gh :i* /rong w9ds /ream f ! we/1 cry/als ( g>net are left project+ on delicate rock f+]s f ! s(t] rock 9 :i* !y 7 imb$d$4 ,w9d-c>v$ pebbles are *>act]i/ically plan$1 ! facets meet+ along a summit ridge or at a po9t l t ( a pyramid4 ,we may suppose t ^! facets 7 gr\nd by preval5t w9ds f c]ta9 directions1 or t f "t to "t ! /one 0 und]m9$ & roll$ ov] z ! s& b5ea? x 0 bl[n away on ! w9dw>d side1 ?us expos+ fre% surfaces to ! driv+ s&4 ,su* w9d-c>v$ pebbles are sometimes f\nd 9 anci5t rocks & may be accept$ z evid5ce t ! s&s ( :i* ! rocks are compos$ 7 bl[n ab\t by ! w9d4 ,deflation4 ,9 ! d5udation ( an arid region1 w9d erosion is comp>atively ineffective z comp>$ ) deflation 7,lat91 de1 f2 fl>e1 to bl[71--a t]m by :i* is meant ! con/ant removal ( wa/e by ! w9d1 leav+ ! rocks b>e to ! cont9u\s attack ( ! wea!r4 ,9 moi/ climates d5udation is cont9ually imp$$ by ! mantle ( wa/e & its cov] ( vegetation1 & ! l& surface c be l[]$ no fa/] ?an ! wa/e is remov$ by runn+ wat]4 ,deep residual soils come to protect all regions ( mod]ate slope1 conceal+ f view ! rock /ructure1 & ! v>i\s =ms ( ! l& are due m to ! ag5cies ( erosion & transportation ?an to diff]5ces 9 ! resi/ance ( ! und]ly+ rocks4 ,illu/ration3 ,fig4 #abi4 ,mesa ,v]de1 ,colorado ,9 ! di/ance on ! left are high volcanic m\nta9s4 ,on ! extreme "r are se5 outli]s ( /rata :i* once cov]$ ! region ( ! mesa ,b 9 arid regions ! mantle is rapidly remov$1 ev5 f well-nigh level pla9s & plateaus1 by ! sweep ( ! w9d & ! wa% ( occasional ra9s4 ,! geological /ructure ( ^! regions ( nak$ rock c be read z f> z ! eye c see1 & x is to ?is /ructure t ! =ms ( ! l& are !re l>gely due4 ,9 a l& mass ( horizontal /rata1 = example1 any s(t] surface rocks we> d[n to "s und]ly+1 resi/ant /ratum1 & ?is = a :ile =ms ! surface ( a level plateau 7,fig4 #abi74 ,! edges ( ! capp+ lay]1 toge!r ) ^? ( any s(t] lay]s b5ea? x1 we> back 9 /eep cliffs1 dissect$ by ! valleys ( wet-wea!r /reams & (t5 swept b>e to ! base by ! w9d4 ,z !y are little protect$ by talus1 :i* commonly is remov$ ab\t z fa/ z =m$1 ^! esc>pm5ts & ! walls ( ! valleys retreat indef9itely1 expos+ "s h>d /ratum b5ea? :i* =ms ! floor ( a wid5+ t]race4 ,! high plateaus ( nor!rn ,arizona & s\!rn ,utah 7,fig4 #acj71 nor? ( ! ,gr& ,canyon ( ! ,colorado ,riv]1 are compos$ ( /ratifi$ rocks m ?an t5 ?\s& feet ?ick & ( v g5tle incl9ation nor?w>d4 ,f ! broad plat =m 9 :i* ! canyon has be5 cut rises a s]ies ( gigantic /airs1 :i* are (t5 m ?an "o ?\s& feet high & a score or m ( miles 9 bread?4 ,! retreat+ esc>pm5ts1 ! cliffs ( ! mesas & buttes :i* !y h left beh9d z outli]s1 & ! walls ( ! rav9es are c>v$ into noble ar*itectural =ms--into ca!drals1 pyramids1 amphi!at]s1 t[]s1 ar*es1 & colonnades--by ! processes ( wea!r+ aid$ by deflation4 ,x is ?us by ! help ( ! action ( ! w9d t great plateaus 9 arid regions are dissect$ & at la/ are smoo!d away to wat]less pla9s1 ei!r compos$ ( nak$ rock1 or /rew$ ) residual gravels1 or cov]$ ) drift+ residual s&4 ,illu/ration3 ,fig4 #acj4 ,nor?-,s\? ,section1 ,eighty-,five ,miles ,long1 across ! ,plateau ,nor? ( ! ,gr& ,canyon ( ! ,colorado ,riv]1 ,arizona1 %[+ ,retreat+ ,esc>pm5ts ,o1 outli]s2 ,v1 canyon ( ! ,colorado2 ,a-,h1 rock sy/ems f ! ,ar*ean to ! ,t]ti>y2 ,p1 plat=m ( ! plateau f :i* ! once ov]ly+ rocks h be5 /ripp$2 dott$ l9es indicate probable =m] ext5sion ( ! /rata4 ,h[ ?ick is ! mass ( /rata :i* has be5 remov$ f ov] ! plat=m8 ,has ?is "w be5 accompli%$ :ile ! ,colorado ,riv] has be5 cutt+ its pres5t canyon8 ,! specific gravity ( air is #a_/hbc t ( wat]4 ,h[ does ?is fact affect ! weight ( ! mat]ial :i* ea* c c>ry at ! same velocity8 ,if ! ra9fall %\ld less5 9 y\r own /ate to f five to t5 in*es a ye>1 :at *anges w\ld take place 9 ! vegetation ( ! c\ntry8 9 ! soil8 9 ! /reams8 9 ! erosion ( valleys8 9 ! ag5cies *iefly at "w 9 d5ud+ ! l&8 ,9 :at way c a w9d-c>v$ pebble be di/+ui%$ f a riv]-worn pebble8 f a glaciat$ pebble8 ,,*apt] ,,vii ,,! ,,sea ,,& ,,its ,,%ores ,illu/ration3 ,fig4 #aca4 ,sea ,cliff & ,rock ,b5* ,cut 9 ,*alk1 ,dov]1 ,engl& ,we h already se5 t ! ocean is ! goal at :i* ! wa/e ( ! l& arrives4 ,! mantle ( rock wa/e1 creep+ d[n slopes1 is wa%$ to ! sea by /reams1 toge!r ) ! mat]ial :i* ! /reams h worn f _! b$s & t dissolv$ by und]gr\nd wat]s4 ,9 arid regions ! w9ds sweep wa/e ei!r into bord]+ oceans or into m humid regions :]e riv]s take x up & c>ry x on to ! sea4 ,glaci]s deliv] ! load ( _! mora9es ei!r directly to ! sea or leave x = /reams to transport to ! same goal4 ,all deposits made on ! l&1 su* z ! flood pla9s ( riv]s1 ! silts ( lake b$s1 dune s&s1 & %eets ( glacial drift1 m>k b pauses 9 ! process :i* is to br+ all ! mat]ials ( ! l& n[ above sea level to re/ ^u ! ocean b$4 ,b ! sea is also at "w along all its %ores z an ag5t ( de/ruction1 & we mu/ fir/ take up its "w 9 erosion be=e we consid] h[ x transports & deposits ! wa/e ( ! l&4 ,sea ,erosion ,! sea cliff & ! rock b5*4 ,on _m coa/s ! l& fronts ! ocean 9 a l9e ( cliffs 7,fig4 #aca74 ,to ! edge ( ! cliffs !re lead d[n valleys & ridges1 c>v$ by runn+ wat]1 :i*1 if ext5d$1 w\ld meet ! wat] surface "s way out f %ore4 ,evid5tly !y are n[ abruptly cut %ort at ! pres5t %ore l9e because ! l& has be5 cut back4 ,illu/ration3 ,fig4 #acb4 ,diagram ( ,sea ,cliff sc1 & ,rock ,b5* rb ,! brok5 l9e indicates ! =m] ext5t ( ! l&4 ,along ! foot ( ! cliff lies a g5tly %elv+ b5* ( rock1 m or less ?ickly v5e]$ ) s& & %+le4 ,at l[ tide its inn] m>g9 is laid b>e1 b at high tide x is cov]$ :olly1 & ! sea wa%es ! base ( ! cliffs4 ,a not*1 ( :i* ! sea cliff & ! rock b5* are ! two sides1 has be5 cut along ! %ore 7,fig4 #acb74 ,waves4 ,! position ( ! rock b5*1 ) its inn] m>g9 slightly above l[ tide1 %[s t x has be5 cut by "s ag5t :i* acts l a horizontal saw set at ab\t sea level4 ,?is ag5t is cle>ly ! surface agitation ( ! wat]2 x is ! w9d-rais$ wave4 ,z a wave comes up ! %elv+ b5* ! cre/ topples =w>d & ! wave breaks1 /rik+ a bl[ ^: =ce is measur$ by ! mom5tum ( all its tons ( fall+ wat] 7,fig4 #acc74 ,on ! coa/ ( ,scotl& ! =ce ( ! bl[s /ruck by ! waves ( ! heavie/ /orms has sometimes exce$$ ?ree tons to ! squ>e foot4 ,b ev5 a calm sea con/antly *afes ! %ore4 ,x heaves 9 g5tle undulations kn[n z ! gr\nd swell1 ! result ( /orms p]haps a ?\s& miles di/ant1 & breaks on ! %ore 9 surf4 ,illu/ration3 ,fig4 #acc4 ,break+ ,wave1 ,lake ,sup]ior ,! bl[s ( ! waves are n /ruck ) cle> wat] only1 else !y w\ld h little effect on cliffs ( solid rock4 ,/orm waves arm !mselves ) ! s& & gravel1 ! cobbles1 & ev5 ! l>ge b[ld]s :i* lie at ! base ( ! cliff1 & beat aga9/ x ) ^! hamm]s ( /one4 ,:]e a precipice desc5ds %e] into deep wat]1 waves swa% up & d[n ! face ( ! rocks b _c break & /rike effective bl[s4 ,!y !re=e erode b little until ! talus fall5 f ! cliff is gradually built up b5ea? ! sea to ! level at :i* ! waves drag bottom ^u x & break4 ,comp>e ! ways 9 :i* diff]5t ag5ts abrade4 ,! w9d lightly bru%es s& & du/ ov] expos$ surfaces ( rock4 ,runn+ wat] sweeps fragm5ts ( v>i\s sizes along its *annels1 hold+ !m ) a loose h&4 ,glacial ice gr9ds ! /ones ( its gr\nd mora9e aga9/ ! und]ly+ rock ) ! pressure ( its enorm\s weight4 ,! wave hurls fragm5ts ( rock aga9/ ! sea cliff1 bruis+ & batt]+ x by ! bl[4 ,x also rasps ! b5* z x drags s& & gravel to & fro ^u x4 ,wea!r+ ( sea cliffs4 ,! sea cliff furni%es ! weapons = its own de/ruction4 ,!y are brok5 f x n only by ! wave b also by ! wea!r4 ,inde$ ! sea cliff wea!rs m rapidly1 z a rule1 ?an d rock l$ges inl&4 ,x is abundantly wet ) spray4 ,along its base ! gr\nd wat] ( ! neighbor+ l& f9ds its natural outlet 9 spr+s :i* "u m9e x4 ,moreov]1 x is unprotect$ by any %ield ( talus4 ,fragm5ts ( rock z !y fall f its face are batt]$ to pieces by ! waves & swept out to sea4 ,! cliff is ?us left expos$ to ! attack ( ! wea!r1 & its retreat w\ld be comp>atively rapid = ?is reason alone4 ,illu/ration3 ,fig4 #acd4 ,sea ,caves1 ,la ,jolla1 ,cali=nia ,copyright1 #ahii1 by ! ,detroit ,photography ,company ,sea cliffs seldom ov]hang1 b commonly1 z 9 ,figure #acd1 slope seaw>d1 %[+ t ! upp] portion has retreat$ at a m rapid rate ?an has ! base4 ,:i* d y inf] is on ! :ole ! m de/ructive ag5t1 wea!r+ or ! wave8 ,draw a section ( a sea cliff cut 9 well jo9t$ rocks ^: jo9ts dip t[>d ! l&4 ,draw a diagram ( a sea cliff :]e ! jo9ts dip t[>d ! sea4 ,sea caves4 ,! wave does n m]ely batt] ! face ( ! cliff4 ,l a skillful qu>ryman x ins]ts w$ges 9 all natural fissures1 su* z jo9ts1 & uses explosive =ces4 ,z a wave flaps aga9/ a crevice x compresses ! air )9 ) ! sudd5 /roke2 z x falls back ! air z sudd5ly exp&s4 ,on ligh?\ses heavily b>r$ doors h be5 bur/ outw>d by ! explosive =ce ( ! air )91 z x 0 releas$ f pressure :5 a p>tial vacuum 0 =m$ by ! reflu5ce ( ! wave4 ,:]e a crevice is fill$ ) wat] ! entire =ce ( ! bl[ ( ! wave is transmitt$ by hydraulic pressure to ! sides ( ! fissure4 ,?us /orm waves little by little pry & suck ! rock loose1 & 9 ?is way1 & by ! bl[s :i* !y /rike ) ! /ones ( ! bea*1 !y qu>ry out ab\t a jo9t1 or :]ev] ! rock may be weak1 a recess kn[n z a sea cave1 provid$ t ! rock above is coh]5t en\gh to =m a ro(4 ,o!rwise an op5 *asm results4 ,illu/ration3 ,fig4 #ace4 ,a ,sea ,ar*1 ,cali=nia ,copyright1 #ahii1 by ! ,detroit ,photography ,company ,bl[holes & sea ar*es4 ,z a sea cave is drill$ back into ! rock1 x may enc\nt] a jo9t or crevice op5$ to ! surface by p]colat+ wat]4 ,! %ock ( ! waves soon enl>ges ?is to a bl[hole1 :i* "o may f9d on ! breezy upl&1 p]haps a hundr$ y>ds & m back f ! cliff's edge4 ,9 quiet wea!r ! bl[hole is a deep well2 9 /orm x plays a f\nta9 z ! waves drive ?r\gh ! long tunnel bel[ & sp\t _! spray high 9 air 9 successive jets4 ,z ! ro( ( ! cave ?us breaks d[n 9 ! re>1 !re may rema9 9 front = a :ile a sea ar*1 simil> to ! natural bridges ( l& cav]ns 7,fig4 #ace74 ,illu/ration3 ,fig4 #acf4 ,*asms worn by ,waves1 ,coa/ ( ,scotl& ,/acks & wave-cut isl&s4 ,z ! sea drives its tunnels & op5 drifts into ! cliff1 x breaks ?r\gh beh9d ! int]v5+ portions & leaves !m isolat$ z /acks1 mu* z monum5ts are deta*$ f inl& esc>pm5ts by ! wea!r2 & z ! sea cliff retreats1 ^! remnant masses may be left beh9d z rocky islets4 ,?us ! rock b5* is (t5 set ) /acks1 islets 9 all /ages ( de/ruction1 & sunk5 reefs1--all wrecks ( ! l& te/ify+ to its retreat be=e ! incessant attack ( ! waves4 ,illu/ration3 ,fig4 #acg4 ,a ,/ack1 ,scotl& ,illu/ration3 ,fig4 #ach4 ,wave-,cut ,isl&s1 ,scotl& ,h[ f> did ! l& once ext5d8 ,coves4 ,:]e zones ( s(t or closely jo9t$ rock outcrop along a %ore1 or :]e m9or wat] c\rses conic d[n to ! sea & aid 9 erosion1 ! %ore is worn back 9 curv$ rentrants call$ coves2 :ile ! m resi/ant rocks on ei!r h& are left project+ z headl&s 7,fig4 #aci74 ,aft] coves are cut back a %ort di/ance by ! waves1 ! headl&s come to protect !m1 z ) breakwat]s1 & prev5t _! indef9ite retreat4 ,! %ore takes a curve ( equilibrium1 along :i* ! h>d rock ( ! expos$ headl& & ! weak rock ( ! protect$ cove we> back at an equal rate4 ,illu/ration3 ,fig4 #aci4 ,coves =m$ 9 ,s(t] ,/rata ,s1 ,s2 :ile ! ,h>d] ,/rata ,h1 ,h1 are left z ,headl&s ,rate ( recession4 ,! rate at :i* a %ore rec$es dep5ds on sev]al factors4 ,9 s(t or incoh]5t rocks expos$ to viol5t /orms ! retreat is s rapid z to be easily measur$4 ,! coa/ ( ,york%ire1 ,engl&1 ^: cliffs are cut 9 glacial drift1 loses sev5 feet a ye> on ! av]age1 & s9ce ! ,norman conque/ a /rip a mile wide1 ) f>m/eads & villages & hi/oric seaports1 has be5 dev\r$ by ! sea4 ,! s&y s\? %ore ( ,m>?a's ,v9ey>d we>s back ?ree feet a ye>4 ,b h>d rocks retreat s sl[ly t _! recession has seldom be5 measur$ by ! records ( hi/ory4 ,illu/ration3 ,fig4 #adj4 ,a ,pebble ,bea*1 ,cape ,ann1 ,massa*usetts ,%ore ,drift ,b[ld] & pebble bea*es4 ,ab\t z fa/ z =m$ ! wa/e ( ! sea cliff is swept bo? along ! %ore & out to sea4 ,! road ( wa/e along %ore is ! bea*4 ,we may also def9e ! bea* z ! expos$ edge ( ! %eet ( s$im5t =m$ by ! c>riage ( l& wa/e out to sea4 ,at ! foot ( sea cliffs1 :]e ! waves are p\nd+ h>de/1 "o commonly f9ds ! rock b5* /rewn on its inn] m>g9 ) l>ge /ones1 dislodg$ by ! waves & by ! wea!r & some:at worn on _! corn]s & edges4 ,f ?is b[ld] bea* ! small] fragm5ts ( wa/e f ! cliff & ! fragm5ts into :i* ! b[ld]s are at la/ brok5 drift on to m %elt]$ places & !re accumulate 9 a pebble bea*1 made ( pebbles well r\nd$ by ! we> :i* !y h suff]$4 ,su* bea*es =m a mill ^: raw mat]ial is con/antly suppli$ by ! cliff4 ,! break]s ( /orms set x 9 motion to a dep? ( sev]al feet1 gr9d+ ! pebbles toge!r ) a clatt] to be he>d above ! ro> ( ! surf4 ,9 su* a rock cru%] ! life ( a pebble is %ort4 ,:]e %ips h /r&$ on our ,atlantic coa/ ) c>goes ( h>d-burn$ brick or ( coal1 a ye> ( "t & a drift ( five miles along ! %ore h prov$ en\gh to we> brick & coal to p[d]4 ,at no great di/ance f _! s\rce1 !re=e1 pebble bea*es give place to bea*es ( s&1 :i* occupy ! m %elt]$ rea*es ( ! %ore4 ,s& bea*es4 ,! angul> s& gra9s ( v>i\s m9]als into :i* pebbles are brok5 by ! waves are gr\nd toge!r "u ! beat+ surf & r\nd$1 & ^? ( ! s(t] m9]als are cru%$ to p[d]4 ,! process1 h[ev]1 is a sl[ "o1 & if we /udy ^! s& gra9s "u a l5s we may be surpris$ to see t1 ?\gh _! corn]s & edges h be5 blunt$1 !y are yet f> f ! sph]ical =m ( ! pebbles f :i* !y 7 d]iv$4 ,! gra9s are small1 & 9 wat] !y h lo/ ab\t half _! weight 9 air2 ! bl[s :i* !y /rike "o ano!r are !re=e weak4 ,besides1 ea* gra9 ( s& ( ! wet bea* is protect$ by a cu%ion ( wat] f ! bl[s ( its neighbors4 ,! %ape & size ( ^! gra9s & ! relative proportion ( gra9s ( ! s(t] m9]als :i* /ill rema9 give a r\gh measure ( ! di/ance 9 space & "t :i* !y h travel$ f _! s\rce4 ,! s& ( _m bea*es1 d]iv$ f ! rocks ( adjac5t cliffs or br\ght 9 by torr5tial /reams f neighbor+ highl&s1 is d>k ) gra9s ( a numb] ( m9]als s(t] ?an qu>tz4 ,! :ite s& ( o!r bea*es1 z ^? ( ! ea/ coa/ ( ,florida1 is almo/ :olly compos$ ( qu>tz gra9s2 = 9 its long travel d[n ! ,atlantic coa/ ! weak] m9]als h be5 worn to p[d] & ! h>de/ alone survive4 ,h[ does ! abs5ce ( cleavage 9 qu>tz affect ! durability ( qu>tz s&8 ,h[ %ore drift migrates4 ,x is "u ! action ( waves & curr5ts t %ore drift migrates sl[ly along a coa/4 ,:]e waves /rike a coa/ obliquely !y drive ! wa/e be=e !m little by little along ! %ore4 ,?us on a nor?-s\? coa/1 :]e ! pr$om9ant /orms are f ! nor!a/1 !re w be a migration ( %ore drift s\?w>ds4 ,all %ores are swept also by curr5ts produc$ by w9ds & tides4 ,^! are usually f> too g5tle to transport ( !mselves ! co>se mat]ials ( :i* bea*es are made4 ,b :ile ! wave /irs ! gra9s ( s& & gravel1 & = a mom5t lifts !m f ! bottom1 ! curr5t c>ries !m a /ep =w>d on _! way4 ,! curr5t _c lift & ! wave _c c>ry1 b toge!r ! two transport ! wa/e along ! %ore4 ,! road ( %ore drift is !re=e ! zone ( ! break+ waves4 ,illu/ration3 ,fig4 #ada4 ,a ,bay ,b>1 ,lake ,ont>io ,! bay-head bea*4 ,z ! wa/e d]iv$ f ! we> ( waves & t br\ght 9 by /reams is trail$ along a coa/ x assumes1 "u v>y+ conditions1 a numb] ( di/9ct =ms4 ,:5 swept into ! head ( a %elt]$ bay x con/itutes ! bay-head bea*4 ,by ! highe/ /orm waves ! bea* is (t5 built high] ?an ! gr\nd imm$iately beh9d x1 & =ms a dam inclos+ a %all[ pond or m>%4 ,! bay b>4 ,z ! /ream ( %ore drift rea*es ! m\? ( a bay ( "s size x (t5 occurs t1 in/ead ( turn+ 91 x sets directly across t[>d ! opposite headl&4 ,! wa/e is c>ri$ out f %ore into ! deep] wat]s ( ! bay m\?2 :]e x is no long] support$ by ! break+ waves1 & s9ks to ! bottom4 ,! dump is gradually built to ! surface z a /ubby spur1 po9t+ across ! bay1 & z x rea*es ! zone ( wave action curr5t & wave c n[ comb9e to c>ry %ore drift along x1 deposit+ _! load cont9ually at ! po9t ( ! spur4 ,an embankm5t is ?us con/ruct$ 9 mu* ! same mann] z a railway fill1 :i*1 :ile x is build+1 s]ves z a roadway along :i* ! dirt f an adjac5t cut is c>t$ to be dump$ at ! end4 ,:5 ! embankm5t is complet$ x bridges ! bay ) a highway along :i* %ore drift n[ moves )\t int]ruption1 & becomes a bay b>4 ,illu/ration3 ,fig4 #adb4 ,a ,hook1 ,lake ,mi*igan ,incomplete bay b>s4 ,"u c]ta9 conditions ! sea _c c>ry out its int5tion to bridge a bay4 ,riv]s dis*>g+ 9 bays dem& op5 way to ! ocean4 ,/rong tidal curr5ts also are able to keep op5 *annels sc\r$ by _! ebb & fl[4 ,9 su* cases ! mo/ t l& wa/e c d is to build spits & %oals1 n>r[+ & %oal+ ! *annel z mu* z possible4 ,incomplete bay b>s sometimes h _! po9ts recurv$ by curr5ts sett+ at "r angles to ! /ream ( %ore drift & are !n classifi$ z hooks 7,fig4 #adb74 ,illu/ration3 ,fig4 #adc4 ,cross ,section ( ,s& ,reef sr1 & ,lagoon2 sl1 ,sea ,level ,s& reefs4 ,on l[ coa/s :]e %all[ wat] ext5ds "s di/ance out1 ! highway ( %ore drift lies along a l[1 n>r[ ridge1 t]m$ ! s& reef1 sep>at$ f ! l& by a n>r[ /ret* ( %all[ wat] call$ ! lagoon 7,fig4 #adc74 ,at int]vals ! reef is held op5 by inlets1--gaps ?r\gh :i* ! tide fl[s & ebbs1 & by :i* ! wat] ( /reams f9ds way to ! sea4 ,illu/ration3 ,fig4 #add4 ,s& ,reef & ,lagoon1 ,texas ,no f9] example ( ?is k9d ( %ore l9e is to be f\nd 9 ! _w ?an ! coa/ ( ,texas4 ,f ne> ! m\? ( ! ,rio ,gr&e a cont9u\s s& reef draws its ev5 curve = a hundr$ miles to ,corpus ,*ri/i ,pass1 & ! reefs are b seldom int]rupt$ by inlets z f> nor? z ,galve/on ,h>bor4 ,on ?is coa/ ! tides are v>iable & exceptionally weak1 be+ less ?an "o foot 9 height1 :ile ! am\nt ( wa/e swept along ! %ore is l>ge4 ,! lagoon is extremely %all[1 & mu* ( x is a mud flat too %oal = ev5 small boats4 ,on ! coa/ ( ,new ,j]sey /rong tides are able to keep op5 inlets at int]vals ( f two to tw5ty miles 9 spite ( a heavy along%ore drift4 ,s& reefs are =m$ :]e ! wat] is s %all[ ne> %ore t /orm waves _c run 9 x & !re=e break "s di/ance out f l&4 ,:]e /orm waves fir/ drag bottom !y erode & deep5 ! sea floor1 & sweep 9 s$im5t z f> z ! l9e :]e !y break4 ,"h1 :]e !y lose _! =ce1 !y drop _! load & beat up ! ridge :i* is kn[n z ! s& reef :5 x rea*es ! surface4 ,%ores ( ,elevation & ,depression ,our /udies h already br\ght to our notice two di/9ct =ms ( /r& l9es1--"o ! high1 rocky coa/ cut back to cliffs by ! attack ( ! waves1 & ! o!r ! l[1 s&y coa/ :]e ! waves break usually ^u ! s& reef4 ,to und]/& ! orig9 ( ^! two types we mu/ "k t ! meet+ place ( sea & l& is det]m9$ prim>ily by movem5ts ( ! e>?'s cru/4 ,:]e a coa/ l& em]ges !--%ore l9e moves seaw>d2 :]e x is be+ subm]g$ ! %ore l9e advances on ! l&4 ,%ores ( elevation4 ,! retreat ( ! sea1 ei!r because ( a local uplift ( ! l& or = any o!r reason1 su* z ! l[]+ ( any portion ( ocean bottom1 lays b>e ! inn] m>g9 ( ! sea floor4 ,:]e ! sea floor has long receiv$ ! wa/e ( ! l& x has be5 built up to a smoo?1 subaque\s pla91 g5tly %elv+ f ! l&4 ,s9ce ! new %ore l9e is drawn across ?is ev5 surface x is simple & regul>1 & is bord]$ on ! "o side by %all[ wat] gradually deep5+ seaw>d1 & on ! o!r by l[ l& compos$ ( mat]ial :i* has n yet ?or\ghly consolidat$ to firm rock4 ,a s& reef is soon beat5 up by ! waves1 & = "s "t conditions w favor its gr[?4 ,! loss ( s& driv5 into ! lagoon beyond1 & ( t gr\nd to p[d] by ! surf & c>ri$ out to sea1 is m ?an made up by ! /ream ( along%ore drift1 & especially by ! drag ( s$im5ts to ! reef by ! waves z !y deep5 ! sea floor on its seaw>d side4 ,mean:ile ! lagoon gradually fills ) wa/e f ! reef & f ! l&4 ,x is invad$ by v>i\s grasses & re$s :i* h le>n$ to gr[ 9 salt & bracki% wat]2 ! m>%1 laid b>e only at l[ tide1 is built above high tide by w9d drift & vegetable deposits1 & becomes a mead[1 sold]+ ! s& reef to ! ma9l&4 ,:ile ! lagoon has be5 fill+1 ! waves h be5 s deep5+ ! sea floor (f ! s& reef t at la/ !y are able to attack x vigor\sly4 ,!y n[ we> x back1 &1 driv+ ! %ore l9e across ! lagoon or mead[1 cut a l9e ( l[ cliffs on ! ma9l&4 ,su* a %ore is t ( ,gascony 9 s\?we/]n ,france1--a l[1 /raight1 s&y %ore1 bord]$ by dunes & unprotect$ by reefs f ! attack ( ! waves ( ! ,bay ( ,biscay4 ,illu/ration3 ,fig4 #ade4 ,map ( ,new ,j]sey1 ) t ,portion ( ! ,/ate "o ,hundr$ ,feet & m above ,sea ,level %ad$ ,describe ! coa/ l9e :i* ! /ate w\ld h if depress$ "o hundr$ feet4 ,comp>e x ) ! pres5t coa/l9e ,we may say1 !n1 t on %ores ( elevation ! pres5ce ( s& reefs & lagoons indicates ! /age ( y\?1 :ile ! abs5ce ( ^! features & ! vigor\s & unimp$$ attack by ! sea ^u ! ma9l& indicate ! /age ( maturity4 ,:]e mu* wa/e is br\ght 9 by riv]s ! maturity ( su* a coa/ may be long delay$4 ,! wa/e f ! l& keeps ! sea %all[ (f%ore & con/antly r5ews ! s& reef4 ,! en]gy ( ! waves is consum$ 9 h&l+ %ore drift1 & no en]gy is left = an effective attack ^u ! l&4 ,inde$1 ) an excessive am\nt ( wa/e br\ght d[n by /reams ! l& may be built out & encroa* tempor>ily ^u ! sea2 & n until long d5udation has l[]$ ! l&1 & ?us decreas$ ! am\nt ( wa/e f x1 may ! waves be able to cut ?r\gh ! s& reef & ?us ! coa/ rea* maturity4 ,%ores ( ,depression ,:]e a coa/al region is und]go+ subm]g5ce ! %ore l9e moves l&w>d4 ,! horizontal plane ( ! sea n[ int]sects an old l& surface r\gh5$ by subarial d5udation4 ,! %ore l9e is irregul> & ind5t$ 9 proportion to ! relief ( ! l& & ! am\nt ( ! subm]g5ce :i* ! l& has suff]$4 ,x foll[s up p>tially subm]g$ valleys1 =m+ bays1 & b5ds r\nd ! divides1 leav+ !m to project z promontories & p59sulas4 ,! outl9es ( %ores ( depression are z v>i$ z are ! =ms ( ! l& p>tially subm]g$4 ,we give a few typical illu/rations4 ,illu/ration3 ,fig4 #adf4 ,*esapeake ,bay ,draw a sket* ( ?is area be=e its depression ,! *>act]i/ics ( ! coa/ ( ,ma9e are due *iefly to ! fact t a m\nta9\s region ( h>d rocks1 once worn to a p5epla91 & aft] a subsequ5t elevation deeply dissect$ by nor?-s\? valleys1 has subsid$1 ! depression am\nt+ on its s\!rn m>g9 to z mu* z six hundr$ feet bel[ sea level4 ,dr[n$ valleys p5etrate ! l& 9 long1 n>r[ bays1 & rugg$ divides project 9 long1 n>r[ l& arms prolong$ seaw>d by isl&s repres5t+ ! high portions ( _! extremities4 ,( ?is exce$+ly ragg$ %ore !re are said to be two ?\s& miles f ! ,new ,brunswick b\nd>y z f> we/ z ,portl&1--a /raight-l9e di/ance ( b two hundr$ miles4 ,s9ce ! "t ( its greate/ depression ! l& is kn[n to h ris5 "s ?ree hundr$ feet2 = ! bays h be5 %ort5$1 & ! wa/e ) :i* _! floors 7 /rewn is n[ 9 "p laid b>e z clay pla9s ab\t ! bay heads & 9 n>r[ selvages ab\t ! p59sulas & isl&s4 ,! coa/ ( ,dalmatia1 on ! ,adriatic ,sea1 is *>act]iz$ by long l& arms & *a9s ( long & n>r[ isl&s1 all p>allel to ! tr5d ( ! coa/4 ,a region ( p>allel m\nta9 ranges has be5 depress$1 & ! longitud9al valleys :i* lie betwe5 !m are occupi$ by arms ( ! sea4 ,*esapeake ,bay is a bran*+ bay due to ! depression ( an anci5t coa/al pla9 :i*1 aft] hav+ em]g$ f ! sea1 0 *annel$ ) broad1 %all[ valleys4 ,! sea has invad$ ! valley ( ! trunk /ream & ^? ( its tribut>ies1 =m+ a %all[ bay ^: _m bran*es are all direct$ t[>d its axis 7,fig4 #adf74 ,hudson ,bay1 & ! ,nor?1 ! ,baltic1 & ! ,yell[ seas are examples :]e ! s9k+ ( ! l& has br\ght ! sea 9 ov] l[ pla9s ( l>ge ext5t1 ?us deeply ind5t+ ! cont95tal outl9e4 ,! rise ( a few hundr$ feet w\ld re/ore ^! subm]g$ pla9s to ! l&4 ,! cycle ( %ores ( depression4 ,9 its infantile /age ! outl9e ( a %ore ( depression dep5ds almo/ :olly on ! previ\s relief ( ! l&1 & b little on erosion by ! sea4 ,sea cliffs & n>r[ b5*es appe> :]e headl&s & outly+ isl&s h be5 nipp$ by ! waves4 ,z yet1 little %ore wa/e has be5 =m$4 ,! coa/ ( ,ma9e is an example ( ?is /age4 ,9 e>ly y\? all promontories h be5 /rongly cliff$1 & "u a vigor\s attack ( ! sea ! %ore ( op5 bays may be cut back also4 ,sea /acks & rocky islets1 caves & coves1 make ! %ore m9utely ragg$4 ,! irregul>ity ( ! coa/1 due to depression1 is = a :ile increas$ by diff]5tial wave we> on h>d] & s(t] rocks4 ,! rock b5* is /ill n>r[4 ,%ore wa/e1 ?\gh be+ produc$ 9 l>ge am\nts1 is = ! mo/ "p swept into deep] wat] & buri$ out ( sight4 ,examples ( ?is /age are ! ea/ coa/ ( ,scotl& & ! ,cali=nia coa/ ne> ,san ,francisco4 ,lat] y\? is *>act]iz$ by a l>ge accumulation ( %ore wa/e4 ,! rock b5* has be5 cut back s t x n[ furni%es a good roadway = %ore drift4 ,! /ream ( along%ore drift gr[s l>g] & l>g]1 fill+ ! heads ( ! small] bays ) bea*es1 build+ spits & hooks1 & ty+ isl&s ) s& b>s to ! ma9l&4 ,x bridges ! l>g] bays ) bay b>s1 :ile _! l5g? is be+ r$uc$ z _! inclos+ promontories are cut back by ! waves4 ,?us !re comes to be a /raight1 cont9u\s1 & easy road1 no long] int]rupt$ by headl&s & bays1 = ! transportation ( wa/e along%ore4 ,! ,baltic coa/ ( ,g]many is 9 ?is /age4 ,illu/ration3 ,fig4 #adg4 ,portion ( ! ,nor?we/ ,coa/ ( ,france ,all ?is :ile /reams h be5 busy fill+ ) delta deposits ! bays into :i* !y empty4 ,by ^! /eps a coa/ gradually advances to maturity1 ! /age :5 ! irregul>ities due to depression h be5 effac$1 :5 outly+ isl&s =m$ by subsid5ce h be5 plan$ away1 & :5 ! %ore l9e has be5 driv5 back beh9d ! =m] bay heads4 ,! sea n[ attacks ! l& mo/ effectively along a cont9u\s & fairly /raight l9e ( cliffs4 ,al?\gh ! fir/ effect ( wave we> 0 to increase ! irregul>ities ( ! %ore1 x soon] or lat] rectifies x1 mak+ x simple & smoo?4 ,! nor?we/ coa/ ( ,france is (t5 cit$ z an example ( a coa/ :i* has rea*$ ?is /age ( developm5t 7,fig4 #adg74 ,9 ! old age ( coa/s ! rock b5* is cut back s f> t ! waves c no long] ex]t _! full effect ^u ! %ore4 ,_! en]gy is dissipat$ 9 mov+ %ore drift hi!r & ?i!r & 9 abrad+ ! b5* :5 !y drag bottom ^u x4 ,little by little ! b5* is deep5$ by tidal curr5ts & ! drag ( waves2 b ?is process is s sl[ t mean:ile ! sea cliffs melt d[n "u ! wea!r1 & ! b5* becomes a broad %oal :]e waves & tides gradually "w ov] ! wa/e f ! l& to great] f95ess & sweep x out to sea4 ,illu/ration3 ,fig4 #adh4 ,! ,s\? ,%ore ( ,m>?a's ,v9ey>d ,! l& is %ad$4 ,to :at class ( coa/s does ?is belong8 ,:at /age has x rea*$1 & by :at process8 ,:at *anges w take place 9 ! future8 ,pla9s ( m>9e abrasion4 ,:ile subarial d5udation r$uces ! l& to baselevel1 ! sea is saw+ its edges to wave base1 i4e4 ! l[e/ limit ( ! wave's effective we>4 ,! wid5$ rock b5* =ms :5 uplift$ a pla9 ( m>9e abrasion1 :i* l ! p5epla9 bevels across /rata reg>dless ( _! v>i\s incl9ations & v>i\s degrees ( h>dness4 ,h[ may a pla9 ( m>9e abrasion be expect$ to diff] f a p5epla9 9 its mantle ( wa/e8 ,comp>$ ) subarial d5udation1 m>9e abrasion is a comp>atively feeble ag5t4 ,at ! rate ( five feet p] c5tury--a high] rate ?an obta9s on ! y\?ful rocky1 coa/ ( ,brita9--x w\ld require m ?an t5 million ye>s to p>e a /rip "o hundr$ miles wide f ! m>g9 ( a cont95t1 a "t suffici5t1 at ! rate at :i* ! ,mississippi valley is n[ be+ worn away1 = subarial d5udation to l[] ! l&s ( ! globe to ! level ( ! sea4 ,sl[ subm]g5ce favors ! cutt+ ( a wide rock b5*4 ,! wat] cont9ually deep5s ^u ! b5*2 /orm waves c !re=e always ride 9 to ! base ( ! cliffs & attack !m ) full =ce2 %ore wa/e _c imp$e ! onset ( ! waves1 = x is cont9ually wa%$ out 9 deep] wat] bel[ wave base4 ,basal conglom]ates4 ,z ! sea m>*es across ! l& dur+ a sl[ subm]g5ce1 ! plat=m is cov]$ ) %eets ( sea-laid s$im5ts4 ,l[e/ ( ^! is a conglom]ate1--! b[ld] & pebble bea*1 wid5$ indef9itely by ! retreat ( ! cliffs at ^: base x 0 =m$1 & pres]v$ by ! f9] deposits laid ^u x 9 ! con/antly deep5+ wat] z ! l& subsides4 ,su* basal conglom]ates are n uncommon among ! anci5t rocks ( ! l&1 & we may "k !m by _! r\nd$ pebbles & l>g] /ones1 compos$ ( ! same k9d ( rock z t ( ! abrad$ & ev5$ surface on :i* !y lie4 ,,*apt] ,,viii ,,(f%ore ,,& ,,deep-,,sea ,,deposits ,! along%ore deposits :i* we h n[ /udi$ are ! expos$ edge ( a va/ subaque\s %eet ( wa/e :i* bord]s ! cont95ts & ext5ds (t5 = z mu* z two or ?ree hundr$ miles f l&4 ,s\nd+s %[ t (f%ore deposits are laid 9 belts p>allel to ! coa/1 ! co>se/ mat]ials ly+ ne>e/ to ! l& & ! f9e/ f>!/ out4 ,! pebbles & gravel & ! clean1 co>se s& ( bea*es give place to broad /ret*es ( s&1 :i* gr[s f9] & f9] until x is succe$$ by %eets ( mud4 ,cle>ly !re is an (f%ore movem5t ( wa/e by :i* x is sort$1 ! co>s] be+ soon] dropp$ & ! f9] be+ c>ri$ f>!r out4 ,(f%ore ,deposits ,! debris torn by waves f rocky %ores is f> less 9 am\nt ?an ! wa/e ( ! l& br\ght d[n to ! sea by riv]s1 be+ only "o ?irty-?ird z great1 accord+ to a cons]vative e/imate4 ,bo? m+le along%ore 9 all ! =ms ( bea* & b> t h be5 describ$1 & bo? are toge!r sl[ly c>ri$ out to sea4 ,on ! %elv+ ocean floor wa/e is agitat$ by v>i\s movem5ts ( ! unquiet wat]1--by ! und]t[ 7an outw>d-runn+ bottom curr5t ne> ! %ore71 by ! ebb & fl[ ( tides1 by ocean curr5ts :]e !y approa* ! l&1 & by waves & gr\nd swells1 ^: effects are sometimes felt to a dep? ( six hundr$ feet4 ,by all ^! means ! wa/e is sl[ly wa%$ to & fro1 & z x is ?us gr\nd f9] & f9] & its soluble p>ts are m & m dissolv$1 x drifts f>!r & f>!r out f l&4 ,x is by no /eady & rapid movem5t t wa/e is swept f ! %ore to its f9al re/+ place4 ,day aft] day & c5tury aft] c5tury ! gra9s ( s& & p>ticles ( mud are %ift$ to & fro1 w9n[$ & spread 9 lay]s1 :i* are de/roy$ & rebuilt aga9 & aga9 be=e !y are buri$ safe f fur!r di/urbance4 ,^! processes :i* are hidd5 f ! eye are among ! mo/ important ( ^? ) :i* our sci5ce has to d2 = x is !y :i* h giv5 %ape to by f> ! l>ge/ "p ( ! /ratifi$ rocks ( :i* ! l& is made4 ,! cont95tal delta4 ,?is fitt+ t]m has be5 rec5tly sugge/$ = ! %eet ( wa/e sl[ly accumulat+ along ! bord]s ( ! cont95ts4 ,)9 a n>r[ belt1 :i* r>ely exce$s two or ?ree hundr$ miles1 except ne> ! m\?s ( muddy riv]s su* z ! ,amazon & ,congo1 ne>ly all ! wa/e ( ! cont95t1 :e!r worn f its surface by ! wea!r1 by /reams1 by glaci]s1 or by ! w9d1 or f its edge by ! *af+ ( ! waves1 comes at la/ to its f9al re/+ place4 ,! ag5cies :i* spread ! mat]ial ( ! cont95tal delta gr[ m & m feeble z !y pass into deep] & m quiet wat] away f %ore4 ,co>se mat]ials are !re=e soon dropp$ along n>r[ belts ne> l&4 ,gravels & co>se s&s lie 9 ?ick1 w$ge-%ap$ masses :i* ?9 out seaw>d rapidly & give place to %eets ( f9] s&4 ,sea muds4 ,out]mo/ ( ! s$im5ts d]iv$ f ! wa/e ( ! cont95ts is a wide belt ( mud2 = f9e clays settle s sl[ly1 ev5 9 sea wat]1--^: saltness causes !m to s9k mu* fa/] ?an !y w\ld 9 fre% wat]1--t !y are waft$ f> be=e !y rea* a bottom :]e !y may rema9 undi/urb$4 ,muds are also f\nd ne> %ore1 c>pet+ ! floors ( e/u>ies1 & among /ret*es ( s&y deposits 9 holl[s :]e ! m quiet wat] has p]mitt$ ! f9] silt to re/4 ,sea muds are commonly blui% & consolidate to blui% %ales2 ! r$ color+ matt] br\ght f l& wa/e--iron oxide--is alt]$ to o!r iron comp\nds by decompos+ organic matt] 9 ! pres5ce ( sea wat]4 ,yell[ & r$ muds occur :]e ! am\nt ( iron oxide 9 ! silt br\ght d[n to ! sea by riv]s is too great to be r$uc$1 or decompos$1 by ! organic matt] pres5t4 ,gre5 muds & gre5 s& owe _! color to c]ta9 *emical *anges :i* take place :]e wa/e f ! l& accumulates on ! sea floor ) extreme sl[ness4 ,a gre5i% m9]al call$ glauconite--a silicate ( iron & alum9a--is !n =m$4 ,su* deposits1 kn[n z gre5 s&1 are n[ 9 process ( mak+ 9 sev]al pat*es (f ! ,atlantic coa/1 & are f\nd on ! coa/al pla9 ( ,new ,j]sey among ! (f%ore deposits ( e>li] geological ages4 ,organic deposits4 ,liv+ creatures sw>m along ! %ore & on ! %all[s out f l& z n[h]e else 9 ! ocean4 ,seawe$ (t5 mantles ! rock ( ! sea cliff betwe5 ! levels ( high & l[ tide1 protect+ x to "s degree f ! bl[s ( waves4 ,on ! rock b5* ea* little pool left by ! ebb+ tide is an aqu>ium ab\nd+ 9 ! l[ly =ms ( m>9e life4 ,bel[ l[-tide level occur b$s ( mollusc\s %ells1 su* z ! oy/]1 ) c\ntless numb]s ( o!r humble organisms4 ,_! h>d] p>ts--! %ells ( mollusks1 ! :ite framework ( corals1 ! c>apaces ( crabs & o!r cru/aceans1 ! %ells ( sea ur*9s1 ! bones & tee? ( fi%es--are gradually buri$ )9 ! accumulat+ %eets ( s$im5t1 ei!r :ole or1 f> m (t51 brok5 into fragm5ts by ! waves4 ,by means ( ^! organic rema9s ea* lay] ( bea* deposits & ^? ( ! cont95tal delta may conta9 a record ( ! life ( ! "t :5 x 0 laid4 ,su* a record has be5 made ev] s9ce liv+ creatures ) h>d p>ts appe>$ ^u ! globe4 ,we %all f9d x seal$ away 9 ! /ratifi$ rocks ( ! cont95ts1--p>ts ( anci5t sea deposits n[ rais$ to =m ! dry l&4 ,?us we h 9 ! traces ( liv+ creatures f\nd 9 ! rocks1 i4e4 9 fossils1 a hi/ory ( ! progress ( life ^u ! planet4 ,illu/ration3 ,fig4 #adi4 ,coqu9a1 ,florida ,mollusc\s %ell deposits4 ,! =ms ( m>9e life ( importance 9 rock mak+ ?rive be/ 9 cle> wat]1 :]e little s$im5t is be+ laid1 & :]e at ! same "t ! dep? is n s great z to deprive !m ( ne$$ light1 heat1 & ( suffici5t oxyg5 absorb$ by sea wat] f ! air4 ,9 su* cle> & comp>atively %all[ wat] !re (t5 gr[ c\ntless myriads ( animals1 su* z mollusks & corals1 ^: %ells & skeletons ( c>bonate ( lime gradually accumulate 9 b$s ( lime/one4 ,a %ell lime/one made ( brok5 fragm5ts cem5t$ toge!r is sometimes call$ coqu9a1 a local t]m appli$ to su* b$s rec5tly uplift$ f ! sea along ! coa/ ( ,florida 7,fig4 #adi74 ,olitic lime/one 7on1 an egg2 li?os1 a /one7 is s nam$ f ! lik5ess ( ! t9y sph]ules :i* compose x to ! roe ( fi%4 ,corals & %ells h be5 p\nd$ by ! waves to calc>e\s s&1 & ea* gra9 has be5 cov]$ ) successive conc5tric coat+s ( lime c>bonate deposit$ ab\t x f solution4 ,! impalpable p[d] to :i* calc>e\s s& is gr\nd by ! waves settles at "s di/ance f %ore 9 deep] & quiet] wat] z a limy silt1 & h>d5s into a d5se1 f9e-gra9$ lime/one 9 :i* p]haps no trace ( fossil is f\nd to sugge/ ! fact t x is ( organic orig94 ,f ,florida ,keys !re ext5ds s\? to ! tr\gh ( ,florida ,/raits a lime/one bank cov]$ by f five hundr$ & =ty to eighte5 hundr$ feet ( wat]4 ,! rocky bottom consi/s ( lime/one n[ sl[ly build+ f ! accumulation ( ! rema9s ( mollusks1 small corals1 sea ur*9s1 worms ) calc>e\s tubes1 & lime-secret+ seawe$1 :i* live ^u its surface4 ,:]e sponges & o!r silica-secret+ organisms ab\nd on lime/one banks1 silica =ms "p ( ! accumulat$ deposit1 ei!r 9 its orig9al condition1 z1 = example1 ! spicules ( sponges1 or ga!r$ into concretions & lay]s ( fl9t4 ,:]e consid]able mud is be+ deposit$ along ) c>bonate ( lime !re is 9 process ( mak+ a clayey lime/one or a limy %ale2 :]e consid]able s&1 a s&y lime/one or a limy s&/one4 ,consolidation ( (f%ore deposits4 ,we _c d\bt t all ^! loose s$im5ts ( ! sea floor are be+ sl[ly consolidat$ to solid rock4 ,!y are soak$ ) wat] :i* c>ries 9 solution lime c>bonate & o!r cem5t+ sub/ances4 ,^! cem5ts are deposit$ betwe5 ! fragm5ts ( %ells & corals1 ! gra9s ( s& & ! p>ticles ( mud1 b9d+ !m toge!r into firm rock4 ,:]e s$im5ts h accumulat$ to great ?ickness ! l[] portions t5d also to consolidate "u ! weight ( ! ov]ly+ b$s4 ,except 9 ! case ( lime/ones1 rec5t sea deposits uplift$ to =m l& are seldom s well cem5t$ z are ! old] /rata1 :i* h long be5 act$ ^u by und]gr\nd wat]s deep bel[ ! surface )9 ! zone ( cem5tation1 & h be5 expos$ to view by great erosion4 ,illu/ration3 ,fig4 #aej4 ,ripple ,m>ks on ,lay]s ( ,anci5t ,s&/one1 ,wiscons9 ,ripple m>ks1 sun cracks1 etc4 ,! pulse ( waves & tidal curr5ts agitates ! loose mat]ial ( (f%ore deposits1 ?r[+ x into f9e p>allel ridges call$ ripple m>ks4 ,"o may see ?is beautiful ribb+ impr9t$ on bea* s&s uncov]$ by ! outgo+ tide1 & x is also produc$ :]e ! wat] is ( consid]able dep?4 ,:ile ! tide is out ! surface ( %ore deposits may be m>k$ by ! footpr9ts ( birds & o!r animals1 or by ! ra9drops ( a pass+ %[] 7,fig4 #aec74 ,! mud ( flats1 ?us expos$ to ! sun & dri$1 cracks 9 a *>act]i/ic way 7,figs4 #aea & #aeb74 ,su* m>k+s may be cov]$ ov] ) a ?9 lay] ( s$im5t at ! next flood tide & seal$ away z a la/+ record ( ! mann] & place 9 :i* ! /rata 7 laid4 ,9 ,figure #aej we h an illu/ration ( a v anci5t ripple-m>k$ s& consolidat$ to h>d /one1 uplift$ & set on edge by movem5ts ( ! e>?'s cru/1 & expos$ to op5 air aft] long erosion4 ,illu/ration3 ,fig4 #aea4 ,sun ,cracks ,/ratification4 ,= ! mo/ "p ! %eet ( sea-laid wa/e is hidd5 f our sight4 ,:]e its edge is expos$ along ! %ore we may see ! surface m>k+s :i* h j be5 notic$4 ,s\nd+s also1 & ! obs]vations made 9 %all[ wat]s by div]s1 tell some?+ ( its surface2 b to le>n m ( its /ructures we mu/ /udy ^? anci5t s$im5ts :i* h be5 lift$ f ! sea & dissect$ by subarial ag5cies4 ,f !m we asc]ta9 t sea deposits are /ratifi$4 ,!y lie 9 di/9ct lay]s :i* (t5 diff] f "o ano!r 9 ?ickness1 9 size ( p>ticles1 & p]haps 9 color4 ,!y are p>t$ by b$d+ planes1 ea* ( :i* repres5ts ei!r a *ange 9 mat]ial or a pause dur+ :i* deposition ceas$ & ! mat]ial ( "o lay] _h "t to settle & become some:at consolidat$ be=e ! mat]ial ( ! next 0 laid ^u x4 ,/ratification is ?us due to int]mitt5tly act+ =ces1 su* z ! agitation ( ! wat] dur+ /orms1 ! fl[ & ebb ( ! tide1 & ! %ift+ *annels ( tidal curr5ts4 ,(f ! m\?s ( riv]s1 /ratification is also caus$ by ! co>s] & m abundant mat]ial br\ght d[n at "t ( floods be+ laid on ! f9] silt :i* is dis*>g$ dur+ ord9>y /ages4 ,illu/ration3 ,fig4 #aeb4 ,! ,"u ,side ( a ,lay] deposit$ ^u a ,sun-,crack$ ,surface1 %[+ ,ca/s ( ! ,cracks ,illu/ration3 ,fig4 #aec4 ,ra9 ,pr9ts ,h[ /ratifi$ deposits are built up is well illu/rat$ 9 ! flats :i* bord] e/u>ies1 su* z ! ,bay ( ,fundy4 ,ea* advance ( ! tide spreads a film ( mud1 :i* dries & h>d5s 9 ! air dur+ l[ wat] be=e ano!r film is laid ^u x by ! next incom+ tidal flood4 ,9 ?is way ! flats h be5 cov]$ by a clay :i* splits into leaves z ?9 z %eets ( pap]4 ,x is 9 f9e mat]ial1 su* z clays & %ales & lime/ones1 t ! ?9ne/ & mo/ uni=m lay]s1 z well z ^? ( wide/ ext5t1 occur4 ,on ! o!r h&1 co>se mat]ials are commonly laid 9 ?ick b$s1 :i* soon ?9 out seaw>d & give place to deposits ( f9] /uff4 ,9 a g5]al way /rata are laid 9 well-nigh horizontal %eets1 = ! surface on :i* !y are laid is g5]ally ( v g5tle incl9ation4 ,ea* /ratum1 h[ev]1 is l5ticul>1 or l5slike1 9 =m1 hav+ an area :]e x is ?icke/1 & ?9n+ out !nce to its edges1 :]e x is ov]lapp$ by /rata simil> 9 %ape4 ,illu/ration3 ,fig4 #aed4 ,cross ,b$d+ 9 ,s&/one1 ,engl& ,cross b$d+4 ,!re is an app>5t exception to ?is rule :]e /rata ^: upp] & l[] surfaces may be ab\t horizontal are made up ( lay]s incl9$ at angles :i* may be z high z ! angle ( repose4 ,9 ?is case ea* /ratum grew by ! addition along its edge ( successive lay]s ( s$im5t1 precisely z does a s& b> 9 a riv]1 ! s& be+ pu%$ cont9u\sly ov] ! edge & com+ to re/ on a slop+ surface4 ,%oals built by /rong & %ift+ tidal curr5ts (t5 %[ successive /rata 9 :i* ! cross b$d+ is incl9$ 9 diff]5t directions4 ,?ickness ( sea deposits4 ,rememb]+ ! va/ am\nt ( mat]ial d5ud$ f ! l& & deposit$ (f%ore1 we %\ld expect t ) ! lapse ( "t sea deposits w\ld h gr[n to an enorm\s ?ickness4 ,x is a sugge/ive fact t1 z a rule1 ! pr(ile ( ! ocean b$ is t ( a s\p plate1--a bas9 surr\nd$ by a fl>+ rim4 ,on ! cont95tal %elf1 z ! rim is call$1 ! wat] is seldom m ?an six hundr$ feet 9 dep? at ! out] edge1 & %all[s gradually t[>ds %ore4 ,along ! ea/]n coa/ ( ! ,unit$ ,/ates ! cont95tal %elf is f fifty to "o hundr$ & m miles 9 wid?2 on ! ,pacific coa/ x is mu* n>r[]4 ,s f> z x is due to upbuild+1 a wide cont95tal %elf1 su* z t ( ! ,atlantic coa/1 implies a massive cont95tal delta ?\s&s ( feet 9 ?ickness4 ,! coa/al pla9 ( ! ,atlantic /ates may be reg>d$ z ! em]g$ inn] m>g9 ( ?is %elf1 & bor+s made along ! coa/ probe x to ! dep? ( z mu* z ?ree ?\s& feet )\t f9d+ ! bottom ( anci5t (f%ore deposits4 ,cont95tal %elves may also be due 9 "p to a subm]g5ce ( ! out] m>g9 ( a cont95tal plateau & to m>9e abrasion4 ,deposition ( s$im5ts & subsid5ce4 ,! /ratifi$ rocks ( ! l& %[ 9 _m places anci5t s$im5ts :i* rea* a ?ickness :i* is measur$ 9 miles1 & :i* are yet ! product ( well-nigh cont9u\s deposition4 ,su* /rata may prove by _! fossils & by _! composition & /ructure t !y 7 all laid (f%ore 9 %all[ wat]4 ,we mu/ inf] t1 dur+ ! va/ l5g? ( "t record$ by ! enorm\s pile1 ! floor ( ! sea along ! coa/ 0 sl[ly s9k+1 & t ! tr\gh 0 con/antly be+ fill$1 foot by foot1 z fa/ z x 0 depress$4 ,su* gradual1 quiet movem5ts ( ! e>?'s cru/ n only modify ! outl9e ( coa/s1 z we h se51 b are ( f> great] geological importance 9 t !y p]mit ! mak+ ( imm5se deposits ( /ratifi$ rock4 ,a sl[ subsid5ce cont9u$ dur+ long "t is record$ also 9 ! succession ( ! v>i\s k9ds ( rock t come to be deposit$ 9 ! same area4 ,z ! sea transgresses ! l&1 i4e4 encroa*es ^u x1 any giv5 "p ( ! sea bottom is br\ght f>!r & f>!r f ! %ore4 ,! basal conglom]ate =m$ by b[ld] & pebble bea*es comes to be cov]$ ) %eets ( s&1 & ^! ) lay]s ( mud z ! sea becomes deep] & ! %ore m remote2 :ile deposits ( lime/one are made :5 at la/ no wa/e is br\ght to ! place f ! n[ di/ant l&1 & ! wat] is left cle> = ! gr[? ( mollusks & o!r lime-secret+ organisms4 ,illu/ration3 ,fig4 #aee4 ,succession ( ,deposits record+ a ,transgress+ ,sea c1 conglom]ate2 ss1 s&/one2 %1 %ale2 lm1 lime/one ,rate ( deposition4 ,z deposition 9 ! sea corresponds to d5udation on ! l&1 we are able to make a g5]al e/imate ( ! rate at :i* ! =m] process is go+ on4 ,leav+ out ( acc\nt ! soluble matt] remov$1 ! ,mississippi is l[]+ its bas9 at ! rate ( "o foot 9 five ?\s& ye>s1 & we may assume ?is z ! av]age rate at :i* ! e>?'s l& surface ( fifty-sev5 million squ>e miles is n[ be+ d5ud$ by ! removal ( its me*anical wa/e4 ,b s$im5ts f ! l& are spread )9 a zone b two or ?ree hundr$ miles 9 wid? along ! m>g9 ( ! cont95ts1 a l9e "o hundr$ ?\s& miles long4 ,z ! area ( deposition--ab\t tw5ty-five million squ>e miles--is ab\t "o half ! area ( d5udation1 ! av]age rate ( deposition mu/ be twice ! av]age rate ( d5udation1 i4e4 ab\t "o foot 9 tw5ty-five hundr$ ye>s4 ,if "s deposits are made mu* m rapidly ?an ?is1 o!rs are made mu* m sl[ly4 ,if !y 7 laid no fa/] ?an ! pres5t av]age rate1 ! /rata ( anci5t sea deposits expos$ 9 a qu>ry fifty feet deep repres5t a lapse ( at lea/ "o hundr$ & tw5ty-five ?\s& ye>s1 & ^? ( a =mation five hundr$ feet ?ick requir$ = _! accumulation "o million two hundr$ & fifty ?\s& ye>s4 ,illu/ration3 ,fig4 #aef4 ,?ick ,(f%ore ,deposits ( ,co>se ,wa/e record+ ! ,pres5ce ( a ,"y ,m\nta9 ,range ne> ,%ore ,! s$im5t>y record & ! d5udation cycle4 ,we h se5 t ! successive /ages 9 a cycle ( d5udation1 su* z t by :i* a l& mass ( l(ty m\nta9s is worn to l[ pla9s1 are m>k$ ea* by its own peculi> l& =ms1 & t ! =ms ( ! e>li] /ages are m or less completely effac$ z ! cycle draws t[>d an end4 ,f> m la/+ records ( ea* /age are left 9 ! s$im5t>y deposits ( ! cont95tal delta4 ,?us1 9 ! y\? ( su* a l& mass z we h m5tion$1 torr5tial /reams fl[+ d[n ! /eep m\nta9 sides deliv] to ! adjac5t sea _! heavy loads ( co>se wa/e1 & ?ick (f%ore deposits ( s& & gravel 7,fig4 #aef7 record ! high elevation ( ! bord]+ l&4 ,z ! l& is worn to l[] levels1 ! am\nt & co>s5ess ( ! wa/e br\ght to ! sea dim9i%es1 until ! sluggi% /reams c>ry only a f9e silt :i* settles on ! ocean floor ne> to l& 9 wide %eets ( mud :i* h>d5 into %ale4 ,at la/1 9 ! old age ( ! region 7,fig4 #aeg71 its l[ pla9s contribute little to ! sea except ! soluble elem5ts ( ! rocks1 & 9 ! cle> wat]s ne> ! l& lime-secret+ organisms fl\ri% & _! rema9s accumulate 9 b$s ( lime/one4 ,:5 long-wea!r$ l&s mantl$ ) deep1 well-oxidiz$ wa/e are uplift$ by a gradual movem5t ( ! e>?'s cru/1 & ! mantle is rapidly /ripp$ (f by ! reviv$ /reams1 ! uprise is record$ 9 wide deposits ( r$ & yell[ clays & s&s ^u ! adjac5t ocean floor4 ,:]e ! wa/e br\ght 9 is m ?an ! waves c easily di/ribute1 z (f ! m\?s ( turbid riv]s :i* dra9 highl&s ne> ! sea1 deposits are little w9n[$1 & are laid 9 rapidly alt]nat+1 %aly s&/ones & s&y %ales4 ,illu/ration3 ,fig4 #aeg4 ,(f%ore ,deposits record+ ,old ,age ( ! ,adjac5t ,l& ss1 s&/one2 %1 %ale2 lm1 lime/one ,:]e ! highl&s are ( igne\s rock1 su* z granite1 & me*anical dis9tegration is go+ on m rapidly ?an *emical decay1 ^! conditions are record$ 9 ! nature ( ! deposits laid (f%ore4 ,! wa/e swept 9 by /reams conta9s mu* feldsp> & o!r m9]als s(t] & m soluble ?an qu>tz1 & :]e ! waves h little opportunity to we> & w9n[ x1 x comes to re/ 9 b$s ( s&/one 9 :i* gra9s ( feldsp> & o!r s(t m9]als are abundant4 ,su* feldspa?ic s&/ones are kn[n z arkose4 ,on ! o!r h&1 :]e ! wa/e suppli$ to ! sea comes *iefly f wide1 s&y1 coa/al pla9s1 !re are deposit$ (f%ore clean s&/ones ( well-worn gra9s ( qu>tz alone4 ,9 su* coa/al pla9s ! wa/e ( ! l& is /or$ = ages4 ,aga9 & aga9 !y are ab&on$ & invad$ by ! sea z f "t to "t ! l& sl[ly em]ges & is aga9 subm]g$4 ,_! deposits are long expos$ to ! wea!r1 & sort$ ov] by ! /reams1 & w9n[$ & work$ ov] aga9 & aga9 by ! waves4 ,9 ! c\rse ( long ages su* deposits ?us become ?or\ghly sort$1 & ! gra9s ( all m9]als s(t] ?an qu>tz are gr\nd to mud4 ,illu/ration3 ,fig4 #aeh4 ,globig]9a ,ooze "u ! ,microscope ,deep-,sea ,oozes & ,clays ,globig]9a ooze4 ,beyond ! rea* ( wa/e f ! l& ! bottom ( ! deep sea is c>pet$ = ! mo/ "p ) ei!r *alky ooze or a f9e r$ clay4 ,! surface wat]s ( ! w>m seas sw>m ) m9ute & l[ly animals belong+ to ! ord] ( ! ,=am9if]a1 :i* secrete %ells ( c>bonate ( lime4 ,at dea? ^! t9y :ite %ells fall ?r\gh ! sea wat] l sn[flakes 9 ! air1 &1 sl[ly dissolv+1 seem to melt q away be=e !y c rea* dep?s great] ?an ab\t ?ree miles4 ,ne> %ore !y rea* bottom1 b are mask$ by ! rapid deposit ( wa/e d]iv$ f ! l&4 ,at int]m$iate dep?s !y mantle ! ocean floor ) a :ite1 s(t lime deposit kn[n z ,globig]9a ooze1 f a g5us ( ! ,=am9if]a :i* contributes l>gely to its =mation4 ,r$ clay4 ,bel[ dep?s ( f fifte5 to eighte5 ?\s& feet ! ocean bottom is %eet$ ) r$ or *ocolate color$ clay4 ,x is ! insoluble residue ( sea%ells1 ( ! debris ( subm>9e volcanic eruptions1 ( volcanic du/ waft$ by ! w9ds1 & ( pieces ( pumice drift$ by ocean curr5ts f> f ! volcanoes f :i* !y 7 hurl$4 ,! r$ clay builds up ) su* inconceivable sl[ness t ! tee? ( %>ks & ! h>d e> bones ( :ales may be dr$g$ 9 l>ge numb]s f ! deep ocean b$1 :]e !y h la9 unburi$ = ?\s&s ( ye>s2 & an appreciable "p ( ! clay is also =m$ by ! du/ ( meteorites consum$ 9 ! atmosph]e1--a du/ :i* falls ev]y:]e on sea & l&1 b :i* else:]e is :olly mask$ by o!r deposits4 ,! d>k1 cold abysses ( ! ocean are f> less affect$ by *ange ?an any o!r portion ( ! surface ( ! li?osph]e4 ,^! va/1 sil5t pla9s ( ooze lie f> bel[ ! rea* ( /orms4 ,!y "k no succession ( summ] & w9t]1 or ( night & day4 ,a mantle ( deep & quiet wat] protects !m f ! ag5ts ( erosion :i* cont9ually attack1 furr[1 & de/roy ! surface ( ! l&4 ,:ile ! l& is ! area ( erosion1 ! sea is ! area ( deposition4 ,! %eets ( s$im5t :i* are sl[ly spread !re t5d to efface any inequalities1 & to =m a smoo? & featureless subaque\s pla94 ,) few exceptions1 ! /ratifi$ rocks ( ! l& are prov$ by _! fossils & composition to h be5 laid 9 ! sea2 b 9 ! same way !y are prov$ to be (f%ore1 %all[-wat] deposits1 ak9 to ^? n[ mak+ on cont95tal %elves4 ,deep-sea deposits are abs5t f ! rocks ( ! l&1 & we may !re=e inf] t ! deep sea has nev] held sway :]e ! cont95ts n[ are1--t ! cont95ts h ev] be51 z n[1 ! elevat$ portions ( ! li?osph]e1 & t ! deep seas ( ! pres5t h ev] be5 its mo/ depress$ portions4 ,! ,reef-,build+ ,corals ,9 w>m seas ! mo/ conspicu\s ( rock-mak+ organisms are ! corals kn[n z ! reef build]s4 ,float+ 9 a boat ov] a coral reef1 z1 = example1 (f ! s\? coa/ ( ,florida or among ! ,bahamas1 "o looks d[n ?r\gh cle> wat] on ?ickets ( bran*+ coral %rubs p]haps z mu* z eight feet high1 & hemisph]ical masses ?ree or f\r feet ?ick1 all abloom ) c\ntless m9ute fl[]like coral polyps1 gorge\s 9 _! colors ( yell[1 orange1 gre51 & r$4 ,9 /ructure ea* t9y polyp is little m ?an a fle%y sac ^: m\? is surr\nd$ ) petal-l t5tacles1 or feel]s4 ,f ! sea wat] ! polyps secrete calcium c>bonate & build x up into ! /ony framework :i* supports _! colonies4 ,bor+ mollusks1 worms1 & sponges p]=ate & honeycomb ?is framework ev5 :ile its surface is cov]$ ) myriads ( liv+ polyps4 ,x is ?us easily brok5 by ! waves1 & :ite fragm5ts ( coral trees /rew ! gr\nd b5ea?4 ,brilliantly color$ fi%es live 9 ^! coral groves1 & c\ntless mollusks1 sea ur*9s1 & o!r =ms ( m>9e life make "h _! home4 ,) ! debris f all ^! s\rces ! reef is con/antly built up until x rises to l[-tide level4 ,high] ?an ?is ! corals _c gr[1 s9ce !y are kill$ by a few h\rs' exposure to ! air4 ,illu/ration3 ,fig4 #aei4 ,pat* ( ,gr[+ ,corals expos$ at an ,exceptionally ,l[ ,tide1 ,great ,b>ri] ,reef1 ,au/ralia ,:5 ! reef has ris5 to wave base1 ! waves abrade x on ! w9dw>d side & pile to leew>d coral blocks torn f _! f\ndation1 fill+ ! int]/ices ) f9] fragm5ts4 ,?us !y heap up along ! reef l[1 n>r[ isl&s 7,fig4 #afj74 ,reef build+ is a comp>atively rapid progress4 ,x has be5 e/imat$ t (f ,florida a reef c\ld be built up to ! surface f a dep? ( fifty feet 9 ab\t fifte5 hundr$ ye>s4 ,illu/ration3 ,fig4 #afj4 ,wave-,built ,isl& on ,coral ,reef r1 reef2 sl1 sea level ,coral lime/ones4 ,lime/ones ( v>i\s k9ds are due to ! reef build]s4 ,! reef rock is made ( corals 9 place & brok5 fragm5ts ( all sizes1 cem5t$ toge!r ) calcium c>bonate f solution by infiltrat+ wat]s4 ,on ! isl& bea*es coral s& is =m+ oolitic lime/one1 & ! :ite coral mud ) :i* ! sea is milky = miles ab\t ! reef 9 times ( /orm settles & concretes into a compact lime/one ( f9e/ gra94 ,corals h be5 among ! mo/ important lime/one build]s ( ! sea ev] s9ce !y made _! appe>ance 9 ! e>ly geological ages4 ,! areas on :i* coral lime/one is n[ =m+ are l>ge4 ,! ,great ,b>ri] ,reef ( ,au/ralia1 :i* lies (f ! nor!a/]n coa/1 is twelve hundr$ & fifty miles long1 & has a wid? ( f t5 to n9ety miles4 ,mo/ ( ! isl&s ( ! tropics are ei!r skirt$ ) coral reefs or are !mselves ( coral =mation4 ,conditions ( coral gr[?4 ,reef-build+ corals _c live except 9 cle> salt wat] less1 z a rule1 ?an "o hundr$ & fifty feet 9 dep?1 ) a w9t] temp]ature n l[] ?an #fh ,f4 ,an important condition also is an abundant food supply1 & ?is is be/ secur$ 9 ! pa? ( ! w>m oceanic curr5ts4 ,coral reefs may be gr\p$ 9 ?ree classes1--fr++ reefs1 b>ri] reefs1 & atolls4 ,fr++ reefs4 ,^! take _! "n f ! fact t !y are atta*$ z n>r[ fr+es to ! %ore4 ,an example is ! reef :i* =ms a selvage ab\t a mile wide along ! nor!a/]n coa/ ( ,cuba4 ,! out] m>g91 indicat$ by ! l9e ( :ite surf1 :]e ! corals are 9 vigor\s gr[?1 rises f ab\t =ty feet ( wat]4 ,betwe5 ?is & ! %ore lies a /ret* ( %oal across :i* "o c wade at l[ wat]1 compos$ ( coral s& ) "h & !re a clump ( gr[+ coral4 ,b>ri] reefs4 ,reefs sep>at$ f ! %ore by a %ip *annel ( quiet wat]1 (t5 sev]al miles 9 wid? & sometimes z mu* z ?ree hundr$ feet 9 dep?1 are kn[n z b>ri] reefs4 ,! seaw>d face rises abruptly f wat] too deep = coral gr[?4 ,l[ isl&s are ca/ up by ! waves ^u ! reef1 & inlets give place = ! ebb & fl[ ( ! tides4 ,along ! we/ coa/ ( ! isl& ( ,new ,cal$onia a b>ri] reef ext5ds = f\r hundr$ miles1 & = a l5g? ( _m leagues seldom approa*es )9 eight miles ( ! %ore4 ,atolls4 ,^! are r+-%ap$ or irregul> coral isl&s1 or isl&-/udd$ reefs1 inclos+ a c5tral lagoon4 ,! n>r[ zone ( l&1 l ! rim ( a great b[l sunk5 to ! wat]'s edge1 rises h>dly m ?an tw5ty feet at mo/ above ! sea1 & is cov]$ ) a =e/ ( trees su* z ! cocoanut1 ^: se$s c be drift$ to x un9jur$ f long di/ances4 ,! :ite bea* ( coral s& leads d[n to ! gr[+ reef1 on ^: out] m>g9 ! surf is con/antly break+4 ,! sea face ( ! reef falls (f abruptly1 (t5 to dep?s ( ?\s&s ( feet1 :ile ! lagoon v>ies 9 dep? f a few feet to "o hundr$ & fifty or two hundr$1 & exceptionally measures z mu* z ?ree hundr$ & fifty feet4 ,!ories ( coral reefs4 ,fr++ reefs require no explanation1 s9ce ! dep? ( wat] ab\t !m is n great] ?an t at :i* coral c gr[2 b b>ri] reefs & atolls1 :i* may rise f dep?s too great = coral gr[? dem& a !ory ( _! orig94 ,illu/ration3 ,fig4 #afa4 ,diagram illu/rat+ ! ,subsid5ce ,!ory ( ,coral ,reefs ,d>w9's !ory holds t b>ri] reefs & atolls are =m$ f fr++ reefs by subsid5ce4 ,! rate ( s9k+ _c be great] ?an t ( ! upbuild+ ( ! reef1 s9ce o!rwise ! corals w\ld be c>ri$ bel[ _! dep? & dr[n$4 ,! process is illu/rat$ 9 ,figure #afa1 :]e v repres5ts a volcanic isl& 9 mid ocean und]go+ sl[ depression1 & ss ! sea level be=e ! s9k+ began1 :5 ! isl& 0 surr\nd$ by a fr++ reef4 ,z ! isl& sl[ly s9ks1 ! reef builds up ) equal pace4 ,x re>s its seaw>d face m /eep ?an ! isl& slope1 & ?us ! int]v5+ space betwe5 ! s9k+1 n>r[+ l& & ! out] m>g9 ( ! reef con/antly wid5s4 ,9 ?is int]v5+ space ! corals are m or less smo!r$ ) silt f ! out] reef & f ! l&1 & are also depriv$ 9 l>ge measure ( ! ne$ful supply ( food & oxyg5 by ! vigor\s gr[? ( ! corals on ! out] rim4 ,! out] rim ?us becomes a b>ri] reef & ! inn] belt ( ret>d$ gr[? is deep5$ by subsid5ce to a %ip *annel1 ss repres5t+ sea level at ?is "t4 ,! f9al /age1 :]e ! isl& has be5 c>ri$ completely b5ea? ! sea & ov]gr[n by ! contract+ reef1 ^: out] r+ n[ =ms an atoll1 is repres5t$ by ss4 ,illu/ration3 ,fig4 #afb4 ,b>ri] ,reef =m$ )\t ,subsid5ce a1 zone ( coral gr[?2 f1 =m] fr++ reef2 t1 talus2 b1 b>ri] reef ,9 v _m in/ances1 h[ev]1 atolls & b>ri] reefs may be expla9$ )\t subsid5ce4 ,?us a b>ri] reef may be =m$ by ! seaw>d gr[? ( a fr++ reef ^u ! talus ( its sea face4 ,9 ,figure #afb1 f is a fr++ reef ^: out] wall rises f ab\t "o hundr$ & fifty feet1 ! l[] limit ( ! reef-build+ species4 ,at ! foot ( ?is subm>9e cliff a talus ( fall5 blocks t accumulates1 & z x rea*es ! zone ( coral gr[? becomes ! f\ndation on :i* ! reef is /eadily ext5d$ seaw>d4 ,z ! reef wid5s1 ! polyps ( ! circumf]5ce fl\ri%1 :ile ^? ( ! inn] belt are ret>d$ 9 _! gr[? & at la/ p]i%4 ,! coral rock ( ! inn] belt is n[ dissolv$ by sea wat] & sc\r$ out by tidal curr5ts until x gives place to a gradually deep5+ %ip *annel1 :ile ! out] m>g9 is left z a b>ri] reef4 ,illu/ration3 ,fig4 #afc4 ,section ( ,atoll on a ,%oal :i* has be5 built up to ne> ! ,surface by ,organic ,deposits ^u a ,subm>9e ,volcanic ,peak v1 volcano2 f1 =am9if]al deposits2 m1 mollusc\s %ell deposits2 c1 coral reef2 sl1 sea level ,9 mu* ! same way atolls may be built on any %oal :i* lies )9 ! zone ( coral gr[?4 ,su* %oals may be produc$ :5 volcanic isl&s are level$ by waves & ocean curr5ts1 & :5 subm>9e plateaus1 ridges1 & peaks are built up by v>i\s organic ag5cies1 su* z mollusc\s & =am9if]al %ell deposits 7,fig4 #afc74 ,! reef-build+ corals1 ^: eggs are drift$ widely ov] ! tropic seas by ocean curr5ts1 colonize su* subm>9e f\ndations :]ev] ! conditions are favorable = _! gr[?4 ,z ! reef approa*es ! surface ! corals ( ! inn] area are smo!r$ by silt & />v$1 & _! ,subm>9e ,volcanic ,peak h>d p>ts are dissolv$ & sc\r$ away2 :ile ^? ( ! circumf]5ce1 ) abundant food supply1 n\ri% & build ! r+ ( ! atoll4 ,atolls may be produc$ also by ! backw>d drift ( s& f ei!r end ( a cresc5tic coral reef or isl&1 ! spits unit+ 9 ! quiet wat] ( ! lee to inclose a lagoon4 ,9 ! ,maldive ,ar*ipelago all gradations betwe5 cresc5t-%ap$ islets & complete atoll r+s h be5 obs]v$4 ,9 a numb] ( in/ances :]e coral reefs h be5 rais$ by movem5ts ( ! e>?'s cru/1 ! reef =mation is f\nd to be a ?9 v5e] built ^u a f\ndation ( o!r deposits4 ,?us ,*ri/mas ,isl&1 9 ! ,indian ,ocean1 is a volcanic pile ris+ elev5 hundr$ feet above sea level & fifte5 ?\s& five hundr$ feet above ! bottom ( ! sea4 ,! summit is a plateau surr\nd$ by a rim ( hills ( reef =mation1 :i* repres5t ! r+ ( islets ( an anci5t atoll4 ,b5ea? ! reef are ?ick b$s ( lime/one1 compos$ l>gely ( ! rema9s ( =am9if]s1 :i* cov] ! lavas & fragm5tal mat]ials ( ! old subm>9e volcano4 ,among ! anci5t s$im5ts :i* n[ =m ! /ratifi$ rocks ( ! l& !re occur _m ?9 reef deposits1 b none are kn[n ( ! imm5se ?ickness :i* mod]n reefs are suppos$ to rea* accord+ to ! !ory ( subsid5ce4 ,b>ri] & fr++ reefs are commonly int]rupt$ (f ! m\?s ( riv]s4 ,:y8 ,summ>y4 ,we h se5 t ! ocean b$ is ! goal to :i* ! wa/e ( ! rocks ( ! l& at la/ arrives4 ,_! soluble p>ts1 dissolv$ by und]gr\nd wat]s & c>ri$ to ! sea by riv]s1 are l>gely built up by liv+ creatures into va/ %eets ( lime/one4 ,! less soluble portions--! wa/e br\ght 9 by /reams & ! wa/e ( ! %ore--=m ! muds & s&s ( cont95tal deltas4 ,all ( ^! sea deposits consolidate & h>d51 & ! coh]5t rocks ( ! l& are ?us recon/ruct$ on ! ocean floor4 ,b ! de/9ation is n a f9al "o4 ,! /ratifi$ rocks ( ! l& are = ! mo/ "p anci5t deposits ( ! sea1 :i* h be5 lift$ above sea level2 & we may believe t ! s$im5ts n[ be+ laid (f%ore are ! du/ ( cont95ts to be1 & w "s "t em]ge to =m additions to ! l&4 ,we are n[ to /udy ! movem5ts ( ! e>?'s cru/ :i* re/ore ! s$im5ts ( ! sea to ! light ( day1 & to ^: b5efic5ce we owe ! habitable l&s ( ! pres5t4 ,,"p ,,ii ,,int]nal ,,geological ,,ag5cies ,,*apt] ,,ix ,,movem5ts ,,( ,,! ,,e>?',s ,,cru/ ,! geological ag5cies :i* we h s f> /udi$--wea!r+1 /reams1 und]gr\nd wat]s1 glaci]s1 w9ds1 & ! ocean--all "w ^u ! e>? f )\t1 & all are set 9 motion by an en]gy ext]nal to ! e>?1 namely1 ! radiant en]gy ( ! sun4 ,all1 too1 h a common t5d5cy to r$uce ! inequalities ( ! e>?'s surface by level+ ! l&s & /rew+ _! wa/e b5ea? ! sea4 ,b despite ! unceas+ ef=ts ( ^! ext]nal ag5cies1 !y h n de/roy$ ! cont95ts1 :i* /ill re> _! broad pla9s & great plateaus & m\nta9 ranges above ! sea4 ,ei!r1 !n1 ! e>? is v "y & ! ag5ts ( d5udation h n yet _h "t to d _! "w1 or !y h be5 oppos$ successfully by o!r =ces4 ,we ent] n[ ^u a dep>tm5t ( our sci5ce :i* treats ( =ces :i* "w ^u ! e>? f )91 & increase ! inequalities ( its surface4 ,x is !y :i* uplift & recreate ! l&s :i* ! ag5ts ( d5udation are cont9ually de/roy+2 x is !y :i* deep5 ! ocean b$ & ?us )draw its wat]s f ! %ores4 ,at times also ^! =ces h aid$ 9 ! de/ruction ( ! l&s by gradually l[]+ !m & br++ 9 ! sea4 ,"u ! action ( =ces resid5t )9 ! e>? ! cru/ sl[ly rises or s9ks2 f "t to "t x has be5 fold$ & brok52 :ile va/ quantities ( molt5 rock h be5 press$ up into x f b5ea? & outp\r$ ^u its surface4 ,we %all take up ^! ph5om5a 9 ! foll[+ *apt]s1 :i* treat ( upheavals & depressions ( ! cru/1 fold+s & fractures ( ! cru/1 e>?quakes1 volcanoes1 ! int]ior conditions ( ! e>?1 m9]al ve9s1 & metamorphism4 ,oscillations ( ! ,cru/ ,( ! v>i\s movem5ts ( ! cru/ due to int]nal ag5cies we w consid] fir/ ^? call$ oscillations1 :i* lift or depress l>ge areas s sl[ly t a long "t is ne$$ to produce p]ceptible *anges ( level1 & :i* leave ! /rata 9 ne>ly _! orig9al horizontal attitude4 ,^! movem5ts are mo/ conspicu\s along coa/s1 :]e !y c be ref]r$ to ! datum plane ( sea level2 we w !re=e take our fir/ illu/rations f ris+ & s9k+ %ores4 ,new ,j]sey4 ,along ! coa/s ( ,new ,j]sey "o may f9d awa% at high tide anci5t %ell heaps1 ! rema9s ( tribal fea/s ( aborig9es4 ,mead[s & old =e/ gr\nds1 ) ! /umps /ill /&+1 are n[ ov]fl[$ by ! sea1 & fragm5ts ( _! turf & wood are br\ght to %ore by waves4 ,assum+ t ! sea level rema9s con/ant1 x is cle> t ! ,new ,j]sey coa/ is n[ gradually s9k+4 ,! rate ( subm]g5ce has be5 e/imat$ at ab\t two feet p] c5tury4 ,on ! o!r h&1 ! wide coa/al pla9 ( ,new ,j]sey is made ( /ratifi$ s&s & clays1 :i*1 z _! m>9e fossils %[1 7 outspread b5ea? ! sea4 ,_! pres5t position above sea level proves t ! l& n[ subsid+ em]g$ 9 ! rec5t pa/4 ,! coa/ ( ,new ,j]sey is an example ( ! sl[ & tranquil oscillations ( ! e>?'s un/able cru/ n[ 9 progress along _m %ores4 ,"s are em]g+ f ! sea1 "s are s9k+ b5ea? x2 & no "p ( ! l& seems to h be5 exempt f ^! *anges 9 ! pa/4 ,evid5ces ( *anges ( level4 ,tak+ ! surface ( ! sea z a level ( ref]5ce1 we may accept z pro(s ( relative upheaval :atev] is n[ f\nd 9 place above sea level & c\ld h be5 =m$ only at or b5ea? x1 & z pro(s ( relative subsid5ce :atev] is n[ f\nd b5ea? ! sea & c\ld only h be5 =m$ above x4 ,?us old /r& l9es ) sea cliffs1 wave-cut rock b5*es1 & bea*es ( wave-worn pebbles or s&1 are /rik+ pro(s ( rec5t em]g5ce to ! am\nt ( _! pres5t height above tide4 ,no less conclusive is ! pres5ce ( sea-laid rocks :i* we may f9d 9 ! neighbor+ qu>ry or outcrop1 al?\gh x may h be5 long ages s9ce !y 7 lift$ f ! sea to =m "p ( ! dry l&4 ,among common pro(s ( subsid5ce are roads & build+s & o!r works ( man1 & vegetal gr[?s & deposits1 su* z =e/ gr\nds & peat b$s1 n[ subm]g$ b5ea? ! sea4 ,9 ! deltas ( _m l>ge riv]s1 su* z ! ,po1 ! ,nile1 ! ,ganges1 & ! ,mississippi1 buri$ soils prove subsid5ces ( hundr$s ( feet2 & 9 sev]al cases1 z 9 ! ,mississippi delta1 ! depression seems to be n[ 9 progress4 ,o!r pro(s ( ! same movem5t are dr[n$ l& =ms :i* are model$ only 9 op5 air4 ,s9ce riv]s _c cut _! valleys f>!r bel[ ! baselevel ( ! sea ?an ! dep?s ( _! *annels1 dr[n$ valleys are among ! pla9e/ pro(s ( depression4 ,to ?is class belong ,n>ragansett1 ,delaw>e1 ,*esapeake1 ,mobile1 & ,san ,francisco bays1 & _m o!r simil> dr[n$ valleys along ! coa/s ( ! ,unit$ ,/ates4 ,less conspicu\s are ! subm>9e *annels :i*1 z s\nd+s %[1 ext5d f ! m\?s ( a numb] ( riv]s "s di/ance out to sea4 ,su* is ! subm]g$ *annel :i* rea*es f ,new ,york ,bay s\!a/ to ! edge ( ! cont95tal %elf1 & :i* is suppos$ to h be5 cut by ! ,hudson ,riv] :5 ?is "p ( ! %elf 0 a coa/al pla94 ,w>p+4 ,9 a region und]go+ *anges ( level ! rate ( movem5t commonly v>ies 9 diff]5t p>ts4 ,portions ( an area may be ris+ or s9k+1 :ile adjac5t portions are /ation>y or mov+ 9 ! opposite direction4 ,9 ?is way a l& surface becomes w>p$4 ,?us1 :ile ,nova ,scotia & ,new ,brunswick are n[ ris+ f ! level ( ! sea1 ,pr9ce ,edw>d ,isl& & ,cape ,breton ,isl& are s9k+1 & ! sea n[ fl[s ov] ! site ( ! fam\s old t[n ( ,l\isburg de/roy$ 9 #ageh4 ,s9ce ! close ( ! glacial epo* ! coa/s ( ,newf\ndl& & ,labrador h ris5 hundr$s ( feet1 b ! rate ( em]g5ce has n be5 uni=m4 ,! old /r& l9e1 :i* /&s at five hundr$ & sev5ty-five feet above tide at ,/4 ,john's1 ,newf\ndl&1 decl9es to two hundr$ & fifty feet ne> ! nor!rn po9t ( ,labrador 7,fig4 #afd74 ,illu/ration3 ,fig4 #afd4 ,w>p$ ,/r& ,l9e f ,/4 ,john's1 ,newf\ndl&1 to ,na*vak1 ,labrador ,! ,great ,lakes is n[ und]go+ p]ceptible w>p+4 ,riv]s ent] ! lakes f ! s\? & we/ ) sluggi% curr5ts & deep *annels resembl+ ! e/u>ies ( dr[n$ riv]s2 :ile ^? t ent] f opposite directions are swift & %all[4 ,at ! we/]n end ( ,lake ,erie are f\nd subm]g$ caves conta9+ /alactites1 & old mead[s & =e/ gr\nds are n[ "u wat]4 ,x is ?us se5 t ! wat] ( ! lakes is ris+ along _! s\?we/]n %ores1 :ile f _! nor!a/]n %ores x is be+ )drawn4 ,! region ( ! ,great ,lakes is !re=e w>p+2 x is ris+ 9 ! nor!a/ z comp>$ ) ! s\?we/4 ,f old b5* m>ks & records ( lake levels x has be5 e/imat$ t ! rate ( w>p+ am\nts to five in*es a c5tury = e "o hundr$ miles4 ,x is calculat$ t ! wat] ( ,lake ,mi*igan is ris+ at ,*icago at ! rate ( n9e or t5 in*es p] c5tury4 ,! divide at ?is po9t betwe5 ! tribut>ies ( ! ,mississippi & ,lake ,mi*igan is b eight feet above ! mean /age ( ! lake4 ,if ! cant+ ( ! region cont9ues at its pres5t rate1 9 a ?\s& ye>s ! wat]s ( ! lake w "h ov]fl[ ! divide4 ,9 ?ree ?\s& five hundr$ ye>s all ! lakes except ,ont>io w dis*>ge by ?is outlet1 via ! ,ill9ois & ,mississippi riv]s1 into ! ,gulf ( ,mexico4 ,! pres5t outlet by ! ,niag>a ,riv] w be left dry1 & ! divide betwe5 ! ,/4 ,lawr5ce & ! ,mississippi sy/ems w h %ift$ f ,*icago to ! vic9ity ( ,buffalo4 ,physiographic effects ( oscillations4 ,we h already m5tion$ sev]al ( ! mo/ important effects ( movem5ts ( elevation & depression1 su* z _! effects on riv]s1 ! mantle ( wa/e 7pp4 #he1 #hf71 & ! =ms ( coa/s 7p4 #aff74 ,movem5ts ( elevation--includ+ uplifts by fold+ & fracture ( ! cru/ to be notic$ lat]--are ! necess>y conditions = erosion by :atev] ag5t4 ,!y det]m9e ! v>i\s ag5cies :i* are to be *iefly conc]n$ m ! we> ( any l&1--:e!r /reams or glaci]s1 wea!r+ or ! w9d1--& ! degree ( _! effici5cy4 ,! l&s mu/ be uplift$ be=e !y c be erod$1 & s9ce !y mu/ be erod$ be=e _! wa/e c be deposit$1 movem5ts ( elevation are a pr]equisite condition = s$im5tation also4 ,subsid5ce is a necess>y condition = deposits ( great ?ickness1 su* z ^? ( ! ,great ,valley ( ,cali=nia & ! ,indo-,gangetic pla9 7p4 #aja71 ! ,mississippi delta 7p4 #aji71 & ! /ill m important =mations ( ! cont95tal delta 9 gradually s9k+ tr\ghs 7p4 #ahc74 ,x is n too mu* to say t ! "* & ?ickness ( ea* =mation ( ! /ratifi$ rocks dep5d prim>ily on ^! cru/al movem5ts4 ,along ! ,baltic coa/ ( ,sw$51 b5* m>ks %[ t ! sea is )draw+ f ! l& at a rate :i* at ! nor? am\nts to betwe5 ?ree & f\r feet p] c5tury2 ,t[>ds ! s\? ! rate decreases4 ,s\? ( ,/ockholm1 until rec5t ye>s1 ! sea has ga9$ ^u ! l&1 & "h 9 sev]al seabo>d t[ns /reets by ! %ore are /ill subm]g$4 ,! rate ( oscillation increases also f ! coa/ inl&4 ,on ! o!r h&1 along ! ,g]man coa/ ( ! ,baltic ! only hi/oric fluctuations ( sea level are ^? :i* may be acc\nt$ = by v>iations due to *anges 9 ra9fall4 ,9 #agcj ,celsius expla9$ ! *anges ( level ( ! ,sw$i% coa/ z due to a l[]+ ( ! ,baltic in/ead ( to an elevation ( ! l&4 ,are ! facts j /at$ consi/5t ) 8 !ory8 ,illu/ration3 ,fig4 #afe4 ,old ,/r& ,l9es1 ,tad\sac1 ,quebec ,at ! little t[n ( ,tad\sac--:]e ! ,sagu5ay ,riv] empties into ! ,/4 ,lawr5ce--!re are t]races ( old sea bea*es1 "s almo/ z fre% z rec5t railway fills1 ! highe/ /&+ two hundr$ & ?irty feet above ! riv] 7,fig4 #afe74 ,"h ! ,sagu5ay is eight hundr$ & =ty feet 9 dep?1 & ! tide ebbs & fl[s f> up its /ream4 ,0 its *annel cut to ?is dep? by ! riv] :5 ! l& 0 at its pres5t height8 ,:at oscillations are "h record$1 & to :at am\nt8 ,illu/ration3 ,fig4 #aff4 ,diagram %[+ ,ru9s ( ,temple1 ,nor? ( ,naples ,c1 anci5t sea cliff2 m1 m>ble pill>s1 dott$ :]e bor$ by mollusks2 sl1 sea level ,a few miles nor? ( ,naples1 ,italy1 ! ru9s ( an anci5t ,roman temple lie by ! edge ( ! sea1 on a n>r[ pla9 :i* is ov]look$ 9 ! re> by an old sea cliff 7,fig4 #aff74 ,?ree m>ble pill>s are /ill /&+4 ,= elev5 feet above _! bases ^! columns are un9jur$1 = to ?is height !y 7 protect$ by an accumulation ( volcanic a%es2 b f elev5 to n9ete5 feet !y are closely pitt$ ) ! holes ( bor+ m>9e mollusks4 ,f ^! facts trace ! hi/ory ( ! oscillations ( ! region4 ,illu/ration3 ,fig4 #afg4 ,section 9 a ,region ( ,fold$ ,rocks ,fold+s ( ! ,cru/ ,! oscillations :i* we h j describ$ leave ! /rata n f> f _! orig9al horizontal attitude4 ,figure #afg repres5ts a region 9 :i* movem5ts ( a v diff]5t nature h tak5 place4 ,"h1 on ei!r side ( ! valley v1 we f9d outcrops ( lay]s tilt$ at high angles4 ,sections along ! ridge r %[ t x is compos$ ( lay]s :i* slant inw>d f ei!r side4 ,9 places ! outcropp+ /rata /& ne>ly on edge1 & on ! "r ( ! valley !y are q ov]turn$2 a %ale % has come to ov]lie a lime/one lm al?\gh ! %ale is ! old] rock1 ^: orig9al position 0 b5ea? ! lime/one4 ,illu/ration3 ,fig4 #afh4 ,dip & ,/rike ,x is n reasonable to suppose t ^! rocks 7 deposit$ 9 ! attitude 9 :i* we f9d !m n[2 we mu/ believe t1 l o!r /ratifi$ rocks1 !y 7 outspread 9 ne>ly level %eets ^u ! ocean floor4 ,s9ce t "t !y mu/ h be5 de=m$4 ,lay]s ( solid rock sev]al miles 9 ?ickness h be5 crumpl$ & fold$ l s(t wax 9 ! h&1 & a va/ d5udation has worn away ! upp] portions ( ! folds1 9 "p repres5t$ 9 our section by dott$ l9es4 ,dip & /rike4 ,9 di/ricts :]e ! /rata h be5 di/urb$ x is desirable to record _! attitude4 ,?is is mo/ easily done by tak+ ! angle at :i* ! /rata are incl9$ & ! compass direction 9 :i* !y slant4 ,x is also conv5i5t to record ! direction 9 :i* ! outcrop ( ! /rata tr5ds across ! c\ntry4 ,illu/ration3 ,fig4 #afi4 ,an ,anticl9e1 ,m>yl& ,! incl9ation ( a b$ ( rocks to ! horizon is its dip 7,fig4 #afh74 ,! am\nt ( ! dip is ! angle made ) a horizontal plane4 ,! dip ( a horizontal lay] is z]o1 & t ( a v]tical lay] is #ij4 ,! direction ( ! dip is tak5 ) ! compass4 ,?us a geologi/'s notebook 9 describ+ ! attitude ( outcropp+ /rata conta9s _m su* entries z ^!3 dip #cb nor?1 or dip #h s\? #bj we/1--mean+ 9 ! latt] case t ! am\nt ( ! dip is #h & ! direction ( ! dip be>s #bj we/ ( s\?4 ,! l9e ( int]section ( a lay] ) ! horizontal plane is ! /rike4 ,! /rike always runs at "r angles to ! dip4 ,dip & /rike may be illu/rat$ by a book set aslant on a %elf4 ,! dip is ! acute angle made ) ! %elf by ! side ( ! book1 :ile ! /rike is repres5t$ by a l9e runn+ along ! book's upp] edge4 ,if ! dip is nor? or s\?1 ! /rike runs ea/ & we/4 ,illu/ration3 ,fig4 #agj4 ,fold$ ,/rata1 ,coa/ ( ,engl& ,a syncl9e 9 ! c5t]1 ) an anticl9e on ei!r side ,fold$ /ructures4 ,an upfold1 9 :i* ! /rata dip away f a l9e drawn along ! cre/ & call$ ! axis ( ! fold1 is kn[n z an anticl9e 7,fig4 #afi74 ,a d[nfold1 :]e ! /rata dip f ei!r side t[>d ! axis ( ! tr\gh1 is call$ a syncl9e 7,fig4 #agj74 ,!re is sometimes se5 a d[nw>d b5d 9 horizontal or g5tly incl9$ /rata1 by :i* !y desc5d to a l[] level4 ,su* a s+le flexure is a monocl9e 7,fig4 #aga74 ,illu/ration3 ,fig4 #aga4 ,a ,monocl9e ,degrees ( fold+4 ,folds v>y 9 degree f broad1 l[ swells1 :i* c h>dly be detect$1 to ! mo/ highly contort$ & complicat$ /ructures4 ,9 symmetric folds 7,figs4 #afi & #ahj7 ! dips ( ! rocks on ea* side ! axis ( ! fold are equal4 ,9 unsymmetrical folds "o limb is /eep] ?an ! o!r1 z 9 ! anticl9e 9 ,figure #afg4 ,9 ov]turn$ folds 7,figs4 #afg & #agb7 "o limb is incl9$ beyond ! p]p5dicul>4 ,fan folds h be5 s p9*$ t ! orig9al anticl9es are left broad] at ! top ?an at ! bottom 7,fig4 #agc74 ,illu/ration3 ,fig4 #agb4 ,ov]turn$ ,fold1 ,v]mont ,9 folds :]e ! compression has be5 great ! lay]s are (t5 f\nd ?ick5$ at ! cre/ & ?9n$ along ! limbs 7#agd74 ,:]e /rong rocks su* z heavy lime/ones are fold$ toge!r ) weak rocks su* z %ales1 ! /rong rocks are (t5 b5t into great simple folds1 :ile ! weak rocks are m9utely crumpl$4 ,illu/ration3 ,fig4 #agc4 ,fan ,folds1 ! ,alps ,sy/ems ( folds4 ,z a rule1 folds occur 9 sy/ems4 ,ov] ! ,appala*ian m\nta9 belt1 = example1 ext5d+ f nor!a/]n ,p5nsylvania to nor!rn ,alabama & ,georgia1 ! e>?'s cru/ has be5 ?r[n into a s]ies ( p>allel folds ^: axes run f nor!a/ to s\?we/ 7,fig4 #age74 ,9 ,p5nsylvania "o may c\nt a score or m ( ^! e>? waves1--"s b f t5 to tw5ty miles 9 l5g?1 & "s ext5d+ z mu* z two hundr$ miles be=e !y die away4 ,on ! ea/]n "p ( ?is belt ! folds are /eep] & m num]\s ?an on ! we/]n side4 ,illu/ration3 ,fig4 #agd4 ,folds ) ,lay]s ?ick5$ at ! ,cre/ & ?9n$ along ! ,limbs ,cause & conditions ( fold+4 ,! sections :i* we h /udi$ sugge/ t rocks are fold$ by lat]al pressure4 ,:ile a s+le1 simple fold might be produc$ by a heave1 a s]ies ( folds1 includ+ ov]turns1 fan folds1 & folds ?ick5$ on _! cre/s at ! exp5se ( _! limbs1 c\ld only be made 9 "o way1--by pressure f ! side4 ,exp]im5t has reproduc$ all =ms ( folds by subject+ to lat]al ?ru/ lay]s ( pla/ic mat]ial su* z wax4 ,va/ z ! =ce mu/ h be5 :i* c\ld fold ! solid rocks ( ! cru/ z "o may crumple ! leaves ( a magaz9e 9 ! f+]s1 x is only "u c]ta9 conditions t x c\ld h produc$ ! results :i* we see4 ,rocks are brittle1 & x is only :5 "u a heavy load & by great pressure sl[ly appli$1 t !y c ?us be fold$ & b5t in/ead ( be+ cru%$ to pieces4 ,"u ^! conditions1 exp]im5ts prove t n only metals su* z /eel1 b also brittle rocks su* z m>ble1 c be de=m$ & mold$ & made to fl[ l pla/ic clay4 ,illu/ration3 ,fig4 #age4 ,relief ,map ( ! ,nor!rn ,appala*ian ,region ,f ,b+ham's ,geographic ,influ5ces 9 ,am]ican ,hi/ory ,zone ( fl[1 zone ( fl[ & fracture1 & zone ( fracture4 ,we may believe t at dep?s :i* mu/ be reckon$ 9 t5s ( ?\s&s ( feet ! load ( ov]ly+ rocks is s great t rocks ( all k9ds yield by fold+ to lat]al pressure1 & fl[ in/ead ( break+4 ,inde$1 at su* pr(\nd dep?s & "u su* inconceivable weight no cavity c =m1 & any fractures w\ld be heal$ at once by ! weld+ ( gra9 to gra94 ,at less dep?s !re exi/s a zone :]e s(t rocks fold & fl[ "u /ress1 & h>d rocks are fractur$2 :ile at & ne> ! surface h>d & s(t rocks alike yield by fracture to /rong pressure4 ,/ructures develop$ 9 ,compress$ ,rocks ,de=m$ rocks %[ ! effects ( ! /resses to :i* !y h yield$1 n only 9 ! imm5se folds into :i* !y h be5 ?r[n b 9 _! smalle/ p>ts z well4 ,a h& specim5 ( slate1 or ev5 a p>ticle "u ! microscope1 may %[ plications simil> 9 =m & orig9 to ! fold+s :i* h produc$ ranges ( m\nta9s4 ,a t9y flake ( mica 9 ! rocks ( ! ,alps may be puck]$ by ! same resi/less =ces :i* h fold$ miles ( solid rock to =m t l(ty range4 ,slaty cleavage4 ,rocks :i* h yield$ to pressure (t5 split easily 9 a c]ta9 direction across ! b$d+ planes4 ,?is cleavage is kn[n z slaty cleavage1 s9ce x is mo/ p]fectly develop$ 9 f9e-gra9$1 homog5e\s rocks1 su* z slates1 :i* cleave to ! ?91 smoo?-surfac$ plates ) :i* we are famili> 9 ! slates us$ 9 ro(+ & = ciph]+ & blackbo>ds4 ,9 co>se-gra9$ rocks1 pressure develops m di/ant p>t+s :i* sep>ate ! rocks into blocks4 ,slaty cleavage _c be due to lam9ation1 s9ce x commonly crosses b$d+ planes at an angle1 :ile ^! planes h be5 (t5 well-nigh or q oblit]at$4 ,exam9+ slate ) a microscope1 we f9d t its cleavage is due to ! gra9 ( ! rock4 ,its p>ticles are flatt5$ & lie ) _! broad faces 9 p>allel planes1 along :i* ! rock naturally splits m easily ?an 9 any o!r direction4 ,! irregul> gra9s ( ! mud :i* has be5 alt]$ to slate h be5 squeez$ flat by a pressure ex]t$ at "r angles to ! plane ( cleavage4 ,cleavage is f\nd only 9 fold$ rocks1 &1 z we may see 9 ,figure #agf1 ! /rike ( ! cleavage runs p>allel to ! /rike ( ! /rata & ! axis ( ! folds4 ,! dip ( ! cleavage is g5]ally /eep1 h5ce ! pressure 0 ne>ly horizontal4 ,! pressure :i* has act$ at "r angles to ! cleavage1 & to :i* x is due1 is ! same lat]al pressure :i* has ?r[n ! /rata into folds4 ,illu/ration3 ,fig4 #agf4 ,slaty ,cleavage ,we f9d additional pro( t slates h und]gone compression at "r angles to _! cleavage 9 ! fact t any inclusions 9 !m1 su* z nodules & fossils1 h be5 squeez$ out ( %ape & h _! long diamet]s ly+ 9 ! planes ( cleavage4 ,t pressure is compet5t to cause cleavage is %[n by exp]im5t4 ,homog5e\s mat]ial ( f9e gra91 su* z beeswax1 :5 subject$ to heavy pressure cleaves at "r angles to ! direction ( ! compress+ =ce4 ,rate ( fold+4 ,all ! facts kn[n ) reg>d to rock de=mation agree t x is a secul> process1 tak+ place s sl[ly t1 l ! deep5+ ( valleys by erosion1 x escapes ! notice ( ! inhabitants ( ! region4 ,x is only "u /resses sl[ly appli$ t rocks b5d )\t break+4 ,! folds ( "s ( ! highe/ m\nta9s h ris5 s gradually t /rong1 well-intr5*$ riv]s :i* _h ! "r ( way across ! region 7 able to hold to _! c\rses1 & z a circul> saw cuts its way ?r\gh ! log :i* is /eadily driv5 aga9/ x1 s ^! riv]s saw$ _! gorges ?r\gh ! fold z fa/ z x rose b5ea? !m4 ,/reams :i* ?us ma9ta9 ! c\rse :i* !y _h antec$5t to a de=mation ( ! region are kn[n z antec$5t /reams4 ,examples ( su* are ! ,sutlej & o!r riv]s ( ,india1 ^: valleys tr5* ! out] ranges ( ! ,himalayas & ^: e>li] riv] deposits h be5 upturn$ by ! ris+ ridges4 ,on ! o!r h&1 m\nta9 cre/s are usually divides1 p>t+ ! head wat]s ( diff]5t dra9age sy/ems4 ,9 ^! cases ! orig9al /reams ( ! region h be5 brok5 or de/roy$ by ! uplift ( ! m\nta9 mass across _! pa?s4 ,on ! :ole1 :i* h work$ m rapidly1 processes ( de=mation or ( d5udation8 ,illu/ration3 ,fig4 #agg4 ,an ,unro($ ,anticl9e ,l& ,=ms due to ,fold+ ,z fold+ goes on s sl[ly1 x is nev] left to =m surface features unmodifi$ by ! action ( o!r ag5cies4 ,an anticl9al fold is attack$ by erosion z soon z x beg9s to rise above ! orig9al level1 & ! high] x is uplift$1 & ! /rong] are its slopes1 ! fa/] is x worn away4 ,ev5 :ile ris+1 a "y upfold is (t5 ?us unro($1 & in/ead ( appe>+ z a long1 ,smoo?1 boat-%ap$ ridge1 x commonly has _h op5$ along ! rocks ( ! axis1 :5 ^! are weak1 a valley :i* is ov]look$ by ! infac+ esc>pm5ts ( ! h>d lay]s ( ! sides ( ! fold 7,fig4 #agg74 ,"u long-cont9u$ erosion1 anticl9es may be degrad$ to valleys1 :ile ! syncl9es ( ! same sy/em may be left 9 relief z ridges 7,fig4 #afg74 ,fold$ m\nta9s4 ,! va/ness ( ! =ces :i* wr9kle ! cru/ is be/ realiz$ 9 ! pres5ce ( "s l(ty m\nta9 range4 ,all m\nta9s1 inde$1 are n ! result ( fold+4 ,"s1 z we %all see1 are due to upw>ps or to fractures ( ! cru/2 "s are piles ( volcanic mat]ial2 "s are swell+s caus$ by ! intrusion ( molt5 matt] b5ea? ! surface2 "s are ! relicts left aft] ! long d5udation ( high plateaus4 ,illu/ration3 ,fig4 #agh4 ,m\nta9 ,peaks c>v$ 9 ,fold$ ,/rata1 ,rocky ,m\nta9s1 ,montana ,b mo/ ( ! m\nta9 ranges ( ! e>?1 & "s ( ! greate/1 su* z ! ,alps & ! ,himalayas1 7 orig9ally m\nta9s ( fold+4 ,! e>?'s cru/ has wr9kl$ into a fold2 or into a s]ies ( folds1 =m+ a s]ies ( p>allel ridges & int]v5+ valleys2 or a numb] ( folds h be5 ma%$ toge!r into a va/ upswell+ ( ! cru/1 9 :i* ! lay]s h be5 s crumpl$ & twi/$1 ov]turn$ & cru%$1 t x is exce$+ly difficult to make out ! orig9al /ructure4 ,! close & intricate folds se5 9 great m\nta9 ranges 7 =m$1 z we h se51 deep bel[ ! surface1 )9 ! zone ( fold+4 ,h5ce !y may nev] h f\nd expression 9 any individual surface features4 ,z ! result ( ^! de=mations deep "u gr\nd ! surface 0 broadly lift$ to m\nta9 height1 & ! crumpl$ & twi/$ m\nta9 /ructures are n[ to be se5 only because erosion has swept away ! heavy cov] ( surface rocks "u ^: load !y 7 develop$4 ,illu/ration3 ,fig4 #agi4 ,section ( a ,portion ( ! ,alps ,:5 ! /ructure ( m\nta9s has be5 deciph]$ x is possible to e/imate r\ghly ! am\nt ( horizontal compression :i* ! region has suff]$4 ,if ! /rata ( ! folds ( ! ,alps 7 smoo!d out1 !y w\ld occupy a belt sev5ty-f\r miles wid] ?an t to :i* !y h be5 compress$1 or twice _! pres5t wid?4 ,a section across ! ,appala*ian folds 9 ,p5nsylvania %[s a compression to ab\t two ?irds ! orig9al wid?2 ! belt has be5 %ort5$ ?irty-five miles 9 e hundr$4 ,consid]+ ! ?ickness ( _! /rata1 ! compression :i* m\nta9s h und]gone acc\nts fully = _! height1 ) en\gh to sp>e = all t has be5 lo/ by d5udation4 ,! ,appala*ian folds involve /rata ?irty ?\s& feet 9 ?ickness4 ,assum+ t ! fold$ /rata re/$ on an unyield+ f\ndation1 & t :at 0 lo/ 9 wid? 0 ga9$ 9 height1 :at elevation w\ld ! range h rea*$ _h n d5udation worn x z x rose8 ,! life hi/ory ( m\nta9s4 ,:ile ! di/urbance & uplift ( m\nta9 masses are due to de=mation1 _! sculpture into ridges & peaks1 valleys & deep rav9es1 & all ! =ms :i* meet ! eye 9 m\nta9 sc5]y1 except+ 9 ! v y\nge/ ranges1 is due solely to erosion4 ,we may !re=e classify m\nta9s accord+ to ! degree to :i* !y h be5 dissect$4 ,! ,juras are an example ( ! /age ( e>ly y\?1 9 :i* ! anticl9es /ill p]si/ z ridges & ! syncl9es co9cide ) ! valleys2 ?is !y owe z mu* to ! slight height ( _! uplift z to ! rec5cy ( its date 7,fig4 #ahj74 ,illu/ration3 ,fig4 #ahj4 ,section ( a ,portion ( ! ,jura ,m\nta9s ,! ,alps 7 upheav$ at v>i\s times 7,fig4 #cii71 ! la/ uplift be+ lat] ?an ! uplift ( ! ,juras1 b to s mu* great] height t erosion has already advanc$ !m well on t[>ds maturity4 ,! m\nta9 mass has be5 cut to ! core1 reveal+ /range contortions ( /rata :i* c\ld nev] h f\nd expression at ! surface4 ,%>p peaks1 knife-edg$ cre/s1 deep valleys ) ungrad$ slopes subject to frequ5t l&slides1 are all features ( ,alp9e sc5]y typical ( a m\nta9 range at ?is /age 9 its life hi/ory4 ,!y repres5t ! survival ( ! h>de/ rocks & ! /ronge/ /ructures1 & ! de/ruction ( ! weak] 9 _! long /ruggle = exi/5ce aga9/ ! ag5ts ( erosion4 ,al?\gh miles ( rock h be5 remov$ f su* ranges z ! ,alps1 we ne$ n suppose t !y ev] /ood mu*1 if any1 high] ?an at pres5t4 ,all ?is va/ d5udation may easily h be5 accompli%$ :ile _! sl[ upheaval 0 go+ on2 9 sev]al m\nta9 ranges we h evid5ce t elevation has n yet ceas$4 ,illu/ration3 ,fig4 #aha4 ,"y ,m\nta9s1 ,rocky ,m\nta9s ( ,canada ,"u long d5udation m\nta9s are subdu$ to ! =ms *>act]i/ic ( old age4 ,! l(ty peaks & jagg$ cre/s ( _! e>li] life are smoo!d d[n to l[ domes & r\nd$ cre/s4 ,! s\!rn ,appala*ians & portions ( ! ,h>tz ,m\nta9s 9 ,g]many 7,fig4 #ahb7 are examples ( m\nta9s :i* h rea*$ ?is /age4 ,illu/ration3 ,fig4 #ahb4 ,subdu$ ,m\nta9s1 ! ,h>tz ,m\nta9s1 ,g]many ,!re are num]\s regions ( upl& & pla9s 9 :i* ! rocks are f\nd to h ! same /ructure t we h se5 9 fold$ m\nta9s2 !y are tilt$1 crumpl$1 & ov]turn$1 & h cle>ly suff]$ int5se compression4 ,we may inf] t _! folds 7 once lift$ to ! height ( m\nta9s & h s9ce be5 wa/$ to l[-ly+ l&s4 ,su* a section z t ( ,figure #fg illu/rates h[ anci5t m\nta9s may be level$ to _! roots1 & repres5ts ! f9al /age to :i* ev5 ! ,alps & ! ,himalayas mu/ sometime arrive4 ,m\nta9s1 p]haps ( ,alp9e height1 once /ood ab\t ,lake ,sup]ior2 a l(ty range once ext5d$ f ,new ,engl& & ,new ,j]sey s\?we/w>d to ,georgia along ! ,pi$mont belt4 ,9 our /udy ( hi/oric geology we %all see m cle>ly h[ %ort is ! life ( m\nta9s z ! e>? c\nts "t1 & h[ great ranges h be5 lift$1 worn away1 & aga9 upheav$ into a new cycle ( erosion4 ,! s$im5t>y hi/ory ( fold$ m\nta9s4 ,we may m5tion "h "s ( ! conditions :i* h commonly be5 antec$5t to great fold+s ( ! cru/4 #a4 ,m\nta9 ranges are made ( belts ( enorm\sly & exceptionally ?ick s$im5ts4 ,! /rata ( ! ,appala*ians are ?irty ?\s& feet ?ick1 :ile ! same =mations ?9 out to five ?\s& feet 9 ! ,mississippi valley4 ,! folds ( ! ,wasat* ,m\nta9s involve /rata ?irty ?\s& feet ?ick1 :i* ?9 to two ?\s& feet 9 ! region ( ! ,pla9s4 #b4 ,! s$im5t>y /rata ( :i* m\nta9s are made are = ! mo/ "p ! %all[-wat] deposits ( cont95tal deltas4 ,m\nta9 ranges h be5 upfold$ along ! m>g9s ( cont95ts4 #c4 ,%all[-wat] deposits ( ! imm5se ?ickness f\nd 9 m\nta9 ranges c be laid only 9 a gradually s9k+ area4 ,a pr(\nd subsid5ce1 (t5 to be reckon$ 9 t5s ( ?\s&s ( feet1 prec$es ! upfold+ ( a m\nta9 range4 ,?us ! hi/ory ( m\nta9s ( fold+ is z foll[s3 ,= long ages ! sea bottom (f ! coa/ ( a cont95t sl[ly subsides1 & ! great tr\gh1 z fa/ z x =ms1 is fill$ ) s$im5ts1 :i* at la/ come to be _m ?\s&s ( feet ?ick4 ,! d[nw>d movem5t f9ally ceases4 ,a sl[ b resi/less pressure sets 91 & gradually1 & ) a long s]ies ( _m int]mitt5t movem5ts1 ! va/ mass ( accumulat$ s$im5ts is crumpl$ & uplift$ into a m\nta9 range4 ,fractures & ,dislocations ( ! ,cru/ ,consid]+ ! imm5se /resses to :i* ! rocks ( ! cru/ are subject$1 x is n surpris+ to f9d t !y (t5 yield by fracture1 l brittle bodies1 in/ead ( by fold+ & fl[+1 l pla/ic solids4 ,:e!r rocks b5d or break dep5ds on ! "* & condition ( ! rocks1 ! load ( ov]ly+ rocks :i* !y be>1 & ! am\nt ( ! =ce & ! sl[ness ) :i* x is appli$4 ,jo9ts4 ,at ! surface1 :]e _! load is lea/1 we f9d rocks univ]sally brok5 into blocks ( great] or less size by p>t+s kn[n z jo9ts4 ,"u ?is "n are includ$ _m division planes caus$ by cool+ & dry+2 b x is n[ g5]ally believ$ t ! l>g] & m regul> jo9ts1 especially ^? :i* run p>allel to ! dip & /rike ( ! /rata1 are fractures due to up-&-d[n movem5ts & fold+s & twi/+s ( ! rocks4 ,illu/ration3 ,fig4 #ahc4 ,jo9ts utiliz$ by a ,riv] 9 wid5+ its ,valley1 ,i[a ,jo9ts are us$ to great advantage 9 qu>ry+1 & we h se5 h[ !y are utiliz$ by ! wea!r 9 break+ up rock masses1 by riv]s 9 wid5+ _! valleys1 by ! sea 9 driv+ back its cliffs1 by glaci]s 9 pluck+ _! b$s1 & h[ !y are enl>g$ 9 soluble rocks to =m natural passageways = und]gr\nd wat]s4 ,! ends ( ! p>t$ /rata mat* along bo? sides ( jo9t planes2 94 jo9ts !re has be5 little or no displacem5t ( ! brok5 rocks4 ,illu/ration3 ,fig4 #ahd4 ,a ,normal ,fault ,faults4 ,9 ,figure #ahd ! rocks h be5 bo? brok5 & dislocat$ along ! plane ff4 ,"o side mu/ h be5 mov$ up or d[n pa/ ! o!r4 ,su* a dislocation is call$ a fault4 ,! am\nt ( ! displacem5t1 z measur$ by ! v]tical di/ance betwe5 ! ends ( a p>t$ lay]1 is ! ?r[ 7cd74 ,! angle 7ffv7 :i* ! fault plane makes ) ! v]tical is ! hade4 ,9 ,figure #ahd ! "r side has gone d[n relatively to ! left2 ! "r is ! side ( ! d[n?r[1 :ile ! left is ! side ( ! up?r[4 ,:]e ! fault plane is n v]tical ! surfaces on ! two sides may be di/+ui%$ z ! hang+ wall 7t on ! "r ( ,figure #ahd7 & ! foot wall 7t on ! left ( ! same figure74 ,faults diff] 9 ?r[ f a fraction ( an in* to _m ?\s&s ( feet4 ,slick5sides4 ,if we exam9e ! walls ( a fault1 we may f9d fur!r evid5ce ( movem5t 9 ! fact t ! surfaces are poli%$ & groov$ by ! enorm\s friction :i* !y h suff]$ z !y h gr\nd "o ^u ! o!r4 ,^! appe>ances1 call$ slick5sides1 h sometimes be5 mi/ak5 = ! results ( glacial action4 ,normal faults4 ,faults are ( two k9ds1--normal faults & ?ru/ faults4 ,normal faults1 ( :i* ,figure #ahd is an example1 hade to ! d[n?r[2 ! hang+ wall has gone d[n4 ,! total l5g? ( ! /rata has be5 increas$ by ! displacem5t4 ,x seems t ! /rata h be5 /ret*$ & brok51 & t ! blocks h readju/$ !mselves "u ! action ( gravity z !y settl$4 ,?ru/ faults4 ,?ru/ faults hade to ! up?r[2 ! hang+ wall has gone up4 ,cle>ly su* faults1 :]e ! /rata occupy less space ?an be=e1 are due to lat]al ?ru/4 ,folds & ?ru/ faults are closely associat$4 ,"u lat]al pressure /rata may fold to a c]ta9 po9t & !n te> ap>t & fault along ! surface ( lea/ resi/ance4 ,"u imm5se pressure /rata also break by %e> )\t fold+4 ,?us1 9 ,figure #ahe1 ! rigid e>? block "u lat]al ?ru/ has f\nd x easi] to break along ! fault plane ?an to fold4 ,:]e su* faults are ne>ly horizontal !y are di/+ui%$ z ?ru/ planes4 ,illu/ration3 ,fig4 #ahe4 ,a ,?ru/ ,fault ,9 all ?ru/ faults "o mass has be5 pu%$ ov] ano!r1 s z to br+ ! und]ly+ & old] /rata ^u y\ng] b$s2 & :5 ! fault planes are ne>ly horizontal1 & especially :5 ! rocks h be5 brok5 into _m slices :i* h slidd5 f> "o ^u ano!r1 ! true succession ( /rata is extremely h>d to deciph]4 ,9 ! ,selkirk ,m\nta9s ( ,canada ! basem5t rocks ( ! region h be5 driv5 ea/ = sev5 miles on a ?ru/ plane1 ov] rocks :i* orig9ally lay ?\s&s ( feet above !m4 ,along ! we/]n ,appala*ians1 f ,virg9ia to ,georgia1 ! m\nta9 folds are brok5 by m ?an fifte5 p>allel ?ru/ planes1 runn+ f nor!a/ to s\?we/1 along :i* ! old] /rata h be5 pu%$ we/w>d ov] ! y\ng]4 ,! longe/ cont9u\s fault has be5 trac$ ?ree hundr$ & sev5ty-five miles1 & ! greate/ horizontal displacem5t has be5 e/imat$ at n less ?an elev5 miles4 ,cru% breccia4 ,rocks (t5 d n fault ) a clean & simple fracture1 b along a zone1 sometimes sev]al y>ds 9 wid?1 9 :i* !y are brok5 to fragm5ts4 ,x may occur also t /rata :i* z a :ole yield to lat]al ?ru/ by fold+ include b$s ( brittle rocks1 su* z ?9-lay]$ lime/ones1 :i* are cru%$ to pieces by ! /ra94 ,9 ei!r case ! fragm5ts :5 recem5t$ by p]colat+ wat]s =m a rock kn[n z a cru% breccia 7pron\nc$ bret*a77,fig4 #ahf74 ,illu/ration3 ,fig4 #ahf4 ,breccia ,breccia is a t]m appli$ to any rock =m$ ( cem5t$ angul> fragm5ts4 ,?is rock may be made by ! consolidation ( volcanic c9d]s1 ( angul> wa/e at ! foot ( cliffs1 or ( fragm5ts ( coral torn by ! waves f coral reefs1 z well z ( /rata cru%$ by cru/al movem5ts4 ,surface ,features due to ,dislocations ,fault sc>ps4 ,a fault ( rec5t date may be m>k$ at surface by a sc>p1 because ! face ( ! up?r[n block has n yet be5 worn to ! level ( ! d[n?r[ side4 ,aft] ! up?r[n block has be5 worn d[n to ?is level1 diff]5tial erosion produces fault sc>ps :]ev] weak rocks & resi/ant rocks are br\ght 9 contact along ! fault plane2 & ! h>d] rocks1 :e!r on ! up?r[ or ! d[n?r[ side1 em]ge 9 a l9e ( cliffs4 ,:]e a fault is s old t no abrupt sc>ps appe>1 its g5]al c\rse is sometimes m>k$ by ! l9e ( division betwe5 highl& & l[l& or hill & pla94 ,great faults h sometimes br\ght anci5t cry/all9e rocks 9 contact ) weak] & y\ng] s$im5t>y rocks1 & long aft] erosion has de/roy$ all fault sc>ps ! h>d] cry/all9es rise 9 an upl& ( rugg$ or m\nta9\s c\ntry :i* meets ! l[l& along ! l9e ( fault+4 ,illu/ration3 ,fig4 #ahg4 ,a ,conceal$ ,fault ,?is fault may be inf]r$ f ! *anges 9 /rata 9 pass+ along ! /rike1 z f b to a & f c to b ,! va/ majority ( faults give rise to no surface features4 ,! fault$ region may be old en\gh to h be5 baselevel$1 or ! rocks on bo? sides ( ! l9e ( dislocation may be alike 9 _! resi/ance to erosion & !re=e h be5 worn d[n to a common slope4 ,! fault may be entirely conceal$ by ! mantle ( wa/e1 & 9 su* cases x c be inf]r$ f abrupt *anges 9 ! "* or ! /rike & dip ( ! /rata :]e !y may outcrop ne> x 7,fig4 #ahg74 ,illu/ration3 ,fig4 #ahh4 ,ea/-,we/ ,section across ! ,brok5 ,plateau nor? ( ! ,gr& ,canyon ( ! ,colorado ,riv]1 ,arizona ,! plateau tr5*$ by ! ,gr& ,canyon ( ! ,colorado ,riv] exhibits a s]ies ( magnific5t fault sc>ps ^: g5]al c\rse is f nor? to s\?1 m>k+ ! edges ( ! great cru/ blocks into :i* ! c\ntry has be5 brok54 ,! highe/ "p ( ! plateau is a cru/ block n9ety miles long & ?irty-five miles 9 maximum wid?1 :i* has be5 hoi/$ to n9e ?\s& ?ree hundr$ feet above1 sea level4 ,on ! ea/ x desc5ds f\r ?\s& feet by a monocl9al fold1 :i* passes into a fault t[>ds ! nor?4 ,on ! we/ x breaks d[n by a succession ( t]races fac$ by fault sc>ps4 ,! ?r[ ( ^! faults v>ies f sev5 hundr$ feet to m ?an a mile4 ,! esc>pm5ts1 h[ev]1 are due 9 a l>ge degree to ! erosion ( weak] rock on ! d[n?r[ side4 ,illu/ration3 ,fig4 #ahi4 ,! ,fault sep>at+ ! ,highl&s & ! ,l[l&s1 ,scotl& ,! ,highl&s ( ,scotl& 7,fig4 #ahi7 meet ! ,l[l&s on ! s\? ) a bold front ( rugg$ hills along a l9e ( dislocation :i* runs across ! c\ntry f sea to sea4 ,on ! "o side are hills ( anci5t cry/all9e rocks ^: crumpl$ /ructures prove t !y are b ! roots ( once l(ty m\nta9s2 on ! o!r lies a l[l& ( s&/one & o!r /ratifi$ rocks =m$ f ! wa/e ( ^? long-vani%$ m\nta9 ranges4 ,remnants ( s&/one occur 9 places on ! nor? ( ! great fault1 & are "h se5 to re/ on ! worn & fairly ev5 surface ( ! cry/all9es4 ,we may inf] t ^! anci5t m\nta9s 7 r$uc$ along _! m>g9s to l[ pla9s1 :i* 7 sl[ly l[]$ b5ea? ! sea to receive a cov] ( s$im5t>y rocks4 ,/ill lat] came an uplift & dislocation4 ,on ! "o side erosion has s9ce /ripp$ (f ! s&/ones = ! mo/ "p1 b ! h>d cry/all9e rocks yet /& 9 bold relief4 ,on ! o!r side ! weak s$im5t>y rocks h be5 worn d[n to l[l&s4 ,rift valleys4 ,9 a brok5 region und]go+ uplift or ! unequal settl+ :i* may foll[1 a slice inclos$ betwe5 two fissures may s9k bel[ ! level ( ! cru/ blocks on ei!r side1 ?us =m+ a l9e> depression kn[n z a rift valley1 or valley ( fracture4 ,illu/ration3 ,fig4 #aij4 ,section f ! ,m\nta9s ( ,pale/9e to ! ,m\nta9s ( ,moab across ! ,dead ,sea a1 anci5t s*i/s2 b1 ,c>bonif]\s /rata2 c1 d1 & e1 ,cretace\s /rata ,"o ( ! mo/ /rik+ examples ( ?is r>e type ( valley is ! long tr\gh :i* runs /raight f ! ,lebanon ,m\nta9s ( ,syria on ! nor? to ! ,r$ ,sea on ! s\?1 & ^: c5tral portion is occupi$ by ! ,jordan valley & ! ,dead ,sea4 ,! plateau :i* x ga%es has be5 lift$ m ?an ?ree ?\s& feet above sea level1 & ! bottom ( ! tr\gh rea*es a dep? ( two ?\s& six hundr$ feet bel[ t level 9 p>ts ( ! ,dead ,sea4 ,s\? ( ! ,dead ,sea ! floor ( ! tr\gh rises some:at above sea level1 & 9 ! ,gulf ( ,akabah aga9 s9ks bel[ x4 ,?is unev5 floor c\ld be acc\nt$ = ei!r by ! pr(\nd w>p+ ( a valley ( erosion or by ! unequal depression ( ! floor ( a rift valley4 ,b t ! tr\gh is a true valley ( fracture is prov$ by ! fact t on ei!r side x is b\nd$ by fault sc>ps & monocl9al folds4 ,! key/one ( ! ar* has subsid$4 ,_m geologi/s believe t ! ,jordan-,akabah tr\gh1 ! long n>r[ bas9 ( ! ,r$ ,sea1 & ! *a9 ( d[n-fault$ valleys :i* 9 ,africa ext5ds f ! /rait ( ,bab-el-,m&eb z f> s\? z ,lake ,nyassa--valleys :i* conta9 m ?an ?irty lakes--belong to a s+le sy/em ( dislocation4 ,%\ld y expect ! lat]al valleys ( a rift valley at ! "t ( its =mation to ent] x z hang+ valleys or at a common level8 ,block m\nta9s4 ,dislocations take place on s gr& a scale t by ! upheaval ( blocks ( ! e>?'s cru/ or ! d[nfault+ ( ! blocks ab\t "o :i* is relatively /ation>y1 m\nta9s kn[n z block m\nta9s are produc$4 ,a tilt$ cru/ block may pres5t a /eep slope on ! side upheav$ & a m g5tle desc5t on ! side depress$4 ,illu/ration3 ,fig4 #aia4 ,block ,m\nta9s1 ,s\!rn ,oregon ,! ,bas9 ranges4 ,! plateaus ( ! ,unit$ ,/ates b\nd$ by ! ,rocky ,m\nta9s on ! ea/1 & on ! we/ by ! ranges :i* front ! ,pacific1 h be5 pr(\ndly fractur$ & fault$4 ,! sy/em ( great fissures by :i* !y are brok5 ext5ds nor? & s\?1 & ! long1 n>r[1 tilt$ cru/ blocks int]cept$ betwe5 ! fissures give rise to ! num]\s nor?-s\? ranges ( ! region4 ,"s ( ! tilt$ blocks1 z ^? ( s\!rn ,oregon1 are z yet b mod]ately c>v$ by erosion1 & %all[ lakes lie on ! wa/e t has be5 wa%$ into ! depressions betwe5 !m 7,fig4 #aia74 ,we may !re=e conclude t _! displacem5t is some:at rec5t4 ,o!rs1 z ^? ( ,nevada1 are s old t !y h be5 deeply dissect$2 _! orig9al =m has be5 de/roy$ by erosion1 & ! int]montane depressions are occupi$ by wide pla9s ( wa/e4 ,dislocations & riv] valleys4 ,be=e geologi/s _h prov$ t riv]s c by _! own unaid$ ef=ts cut deep canyons1 x 0 common to consid] any n>r[ gorge z a gap+ fissure ( ! cru/4 ,?is crude view has long s9ce be5 set aside4 ,a map ( ! plateaus ( nor!rn ,arizona %[s h[ indep5d5t ( ! imm5se faults ( ! region is ! c\rse ( ! ,colorado ,riv]4 ,9 ! ,alps ! tunnels on ! ,sa9t ,got?>d railway pass six times b5ea? ! gorge ( ! ,reuss1 b at no po9t d ! rocks %[ ! slighte/ trace ( a fault4 ,illu/ration3 ,fig4 #aib4 ,fault cross+ ,valley 9 ,japan ,rate ( dislocation4 ,s f> z human exp]i5ce goes1 ! e>? movem5ts :i* we h j /udi$1 "s ( :i* h produc$ deep-sunk valleys & l(ty m\nta9 ranges1 & faults ^: ?r[ is to be measur$ 9 ?\s&s ( feet1 are sl[ & gradual4 ,!y are n accompli%$ by a s+le p>oxysmal ef=t1 b by sl[ creep & a s]ies ( slight slips cont9u$ = va/ l5g?s ( "t4 ,9 ! ,asp5 m9+ di/rict 9 ,colorado fault+ is n[ go+ on at a comp>atively rapid rate4 ,al?\gh no sudd5 slips take place1 ! creep ( ! rock along c]ta9 planes ( fault+ gradually b5ds out ( %ape ! squ>e-set timb]s 9 horizontal drifts & has clos$ "s v]tical %afts by %ift+ ! upp] portion across ! l[]4 ,along "o ( ! faults ( ?is region x is e/imat$ t !re has be5 a movem5t ( at lea/ f\r hundr$ feet s9ce ! ,glacial epo*4 ,m conspicu\s are ! in/ances ( active fault+ by means ( sudd5 slips4 ,9 #ahia !re occurr$ along an old fault plane 9 ,japan a slip :i* produc$ an e>? r5t trac$ = fifty miles 7,fig4 #aib74 ,! c\ntry on "o side 0 depress$ 9 places tw5ty feet bel[ t on ! o!r1 & also %ift$ z mu* z ?irte5 feet horizontally 9 ! direction ( ! fault l9e4 ,9 #ahgb a slip occurr$ = =ty miles on ! great l9e ( dislocation :i* runs along ! ea/]n base ( ! ,si]ra ,nevada ,m\nta9s4 ,9 ! ,ow5s valley1 ,cali=nia1 ! ?r[ am\nt$ to tw5ty-five feet 9 places1 ) a horizontal movem5t along ! fault l9e ( z mu* z eighte5 feet4 ,bo? ?is slip & t 9 ,japan j m5tion$ caus$ sev]e e>?quakes4 ,= ! sake ( cle>ness we h describ$ oscillations1 fold+s1 & fractures ( ! cru/ z sep>ate processes1 ea* giv+ rise to its own peculi> surface features1 b 9 nature e>? movem5ts are by no means s simple1--!y are (t5 implicat$ ) "o ano!r3 folds pass into faults2 9 a de=m$ region c]ta9 rocks h b5t1 :ile o!rs "u ! same /ra91 b "u diff]5t conditions ( pla/icity & load1 h brok52 fold$ m\nta9s h be5 worn to _! roots1 & ! p5epla9s to :i* !y h be5 d5ud$ h be5 upw>p$ to m\nta9 height & aft]w>ds dissect$1--z 9 ! case ( ! ,allegh5y ridges1 ! s\!rn ,c>pa?ians1 & o!r ranges1--or1 z 9 ! case ( ! ,si]ra ,nevada ,m\nta9s1 h be5 brok5 & uplift$ z m\nta9s ( fracture4 ,draw ! foll[+ diagrams1 be+ c>eful to %[ ! direction 9 :i* ! fault$ blocks h mov$1 by ! position ( ! two p>ts ( "s well-def9$ lay] ( lime/one1 s&/one1 or %ale1 :i* occurs on ea* side ( ! fault plane1 z 9 ,figure #ahd4 #a4 ,a normal fault ) a hade ( #ae1 ! orig9al fault sc>p rema9+4 #b4 ,a normal fault ) a hade ( #ej1 ! orig9al fault sc>p worn away1 %[+ cliffs caus$ by h>d] /rata on ! d[n?r[ side4 #c4 ,a ?ru/ fault ) a hade ( #cj1 %[+ cliffs due to h>d] /rata outcropp+ on ! d[n?r[4 #d4 ,a ?ru/ fault ) a hade ( #hj1 ) surface baselevel$4 #e4 ,9 a region ( normal faults a coal m9e is be+ work$ along ! seam ( coal ,,ab 7,fig4 #aic74 ,at ,b x is f\nd brok5 by a fault f :i* hades t[>d ,a4 ,to f9d ! seam aga91 %\ld y advise tunnel+ up or d[n f ,b8 ,illu/ration3 ,fig4 #aic #f4 ,9 a v]tical %aft ( a coal m9e ! same b$ ( coal is pi]c$ twice at diff]5t levels because ( a fault4 ,draw a diagram to %[ :e!r ! fault is normal or a ?ru/4 ,illu/ration3 ,fig4 #aid4 ,ridges to be expla9$ by ,fault+ #g4 ,copy ! diagram 9 ,figure #aid1 %[+ h[ ! two ridges may be acc\nt$ = by a s+le resi/ant /ratum dislocat$ by a fault4 ,is ! fault a /rike fault1 i4e4 "o runn+ p>allel ) ! /rike ( ! /rata1 or a dip fault1 "o runn+ p>allel ) ! direction ( ! dip8 ,illu/ration3 ,fig4 #aie4 ,e>? ,block ( ,tilt$ ,/rata1 ) ,includ$ ,seam ( ,coal cc #h4 ,draw a diagram ( ! block 9 ,figure #aie z x w\ld appe> if dislocat$ along ! plane efg by a normal fault ^: ?r[ equals "o f\r? ! height ( ! block4 ,is ! fault a /rike or a dip fault8 ,draw a second diagram %[+ ! same block aft] d5udation has worn x d[n bel[ ! c5t] ( ! up?r[n side4 ,note t ! outcrop ( ! coal seam is n[ deceptively repeat$4 ,?is ex]cise may be done 9 blocks ( wood in/ead ( draw+s4 ,illu/ration3 ,fig4 #aif4 ,a & ,b4 ,repeat$ ,outcrops ( ,same ,/rata #i4 ,draw diagrams %[+ by dott$ l9es ! conditions bo? ( ,a & ,b1 ,figure #aif1 aft] de=mation _h giv5 ! /rata _! pres5t attitude4 ,illu/ration3 ,fig4 #aig4 ,a ,block ,m\nta9 #aj4 ,:at is ! attitude ( ! /rata ( ?is e>? block1 ,figure #aig8 ,:at has tak5 place along ! plane baf8 ,:5 did ! dislocation occur comp>$ ) ! fold+ ( ! /rata8 ,) ! erosion ( ! valleys on ! "r-h& side ( ! m\nta98 ,) ! deposition ( ! s$im5ts efg8 ,d y f9d any remnants ( ! orig9al surface baf produc$ by ! dislocation8 ,f ! left-h& side ( ! m\nta9 inf] :at 0 ! relief ( ! region be=e ! dislocation4 ,give ! complete hi/ory record$ 9 ! diagram f ! deposition ( ! /rata to ! pres5t4 ,illu/ration3 ,fig4 #aih4 ,a ,fault$ ,lava ,fl[ aa #aa4 ,:i* is ! old] fault1 9 ,figure #aih1 f or f8 ,:5 did ! lava fl[ occur8 ,h[ long a "t elaps$ betwe5 ! =mation ( ! two faults z measur$ 9 ! "w done 9 ! int]val8 ,h[ long a "t s9ce ! =mation ( ! lat] fault8 ,illu/ration3 ,fig4 #aii4 ,measurem5t ( ! ,?ickness ( ,incl9$ ,/rata #ab4 ,measure by ! scale ! ?ickness bc ( ! coal-be>+ /rata outcropp+ f a to b 9 ,figure #aii4 ,on any conv5i5t scale draw a simil> section ( /rata ) a dip ( #cj outcropp+ along a horizontal l9e normal to ! /rike "o ?\s& feet 9 l5g?1 & measure ! ?ickness ( ! /rata by ! scale employ$4 ,! ?ickness may also be calculat$ by trigonometry4 ,illu/ration3 ,fig4 #bjj4 ,uncon=mity betwe5 ,p>allel ,/rata ,illu/ration3 ,fig4 #bja4 ,uncon=mity betwe5 ,non-p>allel ,/rata ,uncon=mity ,/rata deposit$ "o ^u1 ano!r 9 an unbrok5 succession are said to be con=mable4 ,b ! cont9u\s deposition ( /rata is (t5 int]rupt$ by movem5ts ( ! e>?'s cru/1 ,old sea floors are lift$ to =m l& & are aga9 depress$ b5ea? ! sea to receive a cov] ( s$im5ts only aft] an int]val dur+ :i* !y 7 c>v$ by subarial erosion4 ,an erosion surface :i* ?us p>ts old] f y\ng] /rata is kn[n z an uncon=mity1 & ! /rata above x are said to be uncon=mable ) ! rocks bel[1 or to re/ uncon=mably ^u !m4 ,an uncon=mity ?us records movem5ts ( ! cru/ & a consequ5t break 9 ! deposition ( ! /rata4 ,x d5otes a p]iod ( l& erosion ( great] or less l5g?1 :i* may sometimes be r\ghly measur$ by ! /age 9 ! erosion cycle :i* ! l& surface _h atta9$ be=e its burial4 ,uncon=mable /rata may be p>allel1 z 9 ,figure #bjj1 :]e ! record includes ! deposition ( /rata a1 _! em]g5ce1 ! erosion ( ! l& surface ss1 a subm]g5ce & ! deposit ( ! /rata b1 & la/ly1 em]g5ce & ! erosion ( ! pres5t surface ss4 ,illu/ration3 ,fig4 #bjb4 ,c>bonif]\s ,lime/one re/+ uncon=mably on ,e>ly ,silurian ,slates1 ,york%ire1 ,engl& ,(t5 ! e>? movem5ts to :i* ! uplift or depression 0 due involv$ tilt+ or fold+ ( ! e>li] /rata1 s t ! /rata are n[ nonp>allel z well z uncon=mable4 ,9 ,figure #bja1 = example1 ! record includes deposition1 uplift1 & tilt+ ( a2 erosion1 depression1 ! deposit ( b2 & f9ally ! uplift :i* has br\ght ! rocks to op5 air & p]mitt$ ! dissection by :i* ! uncon=mity is reveal$4 ,f ?is section we inf] t dur+ e>ly ,silurian times ! area 0 sea1 & ?ick sea muds 7 laid ^u x4 ,^! 7 lat] alt]$ to h>d slates by pressure & upfold$ into m\nta9s4 ,dur+ ! lat] ,silurian & ! ,devonian ! area 0 l& & suff]$ va/ d5udation4 ,9 ! ,c>bonif]\s p]iod x 0 l[]$ b5ea? ! sea & receiv$ a cov] ( lime/one4 ,illu/ration3 ,fig4 #bjc4 ,diagram ,illu/rat+ h[ ! ,age ( ,m\nta9s is det]m9$ ,! age ( m\nta9s4 ,x is l>gely by means ( uncon=mities t we read ! hi/ory ( m\nta9 mak+ & o!r de=mations & movem5ts ( ! cru/4 ,9 ,figure #bjc1 = example1 ! de=mation :i* upfold$ ! range ( m\nta9s took place aft] ! deposit ( ! s]ies ( /rata a ( :i* ! m\nta9s are compos$1 & be=e ! deposit ( ! /ratifi$ rocks1 :i* re/ uncon=mably on a & h n %>$ _! uplift4 ,illu/ration3 ,fig4 #bjd4 ,section ( ,m\nta9 ,range %[+ repeat$ ,uplifts a1 /rata ^: fold+ =m$ a m\nta9 range2 on1 baselevel$ surface produc$ by long d5udation ( ! m\nta9s2 b1 tilt$ /rata re/+ uncon=mably on a2 c1 horizontal /rata p>t$ f b by ! uncon=mity uu4 ,! fir/ uplift ( ! range prec$$ ! p]iod ( "t :5 b 0 deposit$4 ,! & uplift1 to :i* ! pres5t m\nta9s owe _! height1 0 lat] ?an ?is p]iod b e>li] ?an ! p]iod :5 /rata c 7 laid ,mo/ great m\nta9 ranges1 l ! ,si]ra ,nevada & ! ,alps1 m>k l9es ( weakness along :i* ! e>?'s cru/ has yield$ aga9 & aga9 dur+ ! long ages ( geological "t4 ,! /rata deposit$ at v>i\s times ab\t _! flanks h be5 infold$ by lat] crumpl+s ) ! orig9al m\nta9 mass1 & h be5 repeat$ly cru%$1 inv]t$1 fault$1 intrud$ ) igne\s rocks1 & d5ud$4 ,! /ructure ( great m\nta9 ranges ?us becomes exce$+ly complex & difficult to read4 ,a comp>atively simple case ( repeat$ uplift is %[n 9 ,figure #bjd4 ,9 ! section ( a portion ( ! ,alps %[n 9 ,figure #agi a f> m complicat$ hi/ory may be deciph]$4 ,illu/ration3 ,fig4 #bje4 ,uncon=mity %[+ ,buri$ ,valleys lm1 lime/one2 %1 %ale2 r1 r1 & r1 riv] silts fill+ erod$ valleys 9 ! lime/one4 ,! upp] surface ( ! lime/one is evid5tly a l& surface develop$ by erosion4 ,! valleys :i* tr5* x are n>r[ & /eep-sid$2 h5ce ! l& surface _h n rea*$ maturity4 ,! s&s & muds1 n[ h>d5$ to firm rock1 :i* fill ^! valleys1 r1 r1 & r1 conta9 no relics ( ! sea1 b ,in/ead ! rema9s ( l& animals & plants4 ,!y are riv] deposits1 & we may inf] t ow+ to a subsid5ce ! "y riv]s ceas$ to degrade _! *annels & sl[ly fill$ _! gorges ) s&s & silts4 ,! ov]ly+ %ale records a fur!r depression :i* br\ght ! lanes bel[ ! level ( ! sea4 ,a section simil> to ?is is to be se5 9 ! coal m9es ( ,b]nissant1 ,belgium1 :]e a gorge twice z deep z t ( ,niag>a 0 discov]$ )9 ^: anci5t riv] deposits 7 f\nd entomb$ ! skeletons ( m ?an a score ( ! huge reptiles *>act]i/ic ( ! age :5 ! gorge 0 cut & fill$ ,illu/ration3 ,fig4 #bjf4 ,uncon=mity %[+ ,buri$ ,m\nta9s1 ,scotl& gn1 anci5t cry/all9e rocks2 ss1 m>9e s&/ones4 ,! surface bb ( ! anci5t cry/all9e rocks is m\nta9\s1 ) peaks ris+ to a height ( z mu* z ?ree ?\s& feet4 ,x is "o ( ! mo/ anci5t l& surfaces on ! planet & is cov]$ uncon=mably ) pre-,cambrian s&/ones ?\s&s ( feet 9 ?ickness1 9 :i* ! ,torridonian ,m\nta9s ( ,scotl& h be5 c>v$4 ,:at has be5 ! hi/ory ( ! region s9ce ! m\nta9\s surface bb 0 produc$ by erosion8 ,uncon=mities 9 ! ,colorado ,canyon1 ,arizona4 ,h[ geological hi/ory may be read 9 uncon=mities is fur!r illu/rat$ 9 ,figures #bjg & #bjh4 ,! d>k cry/all9e rocks a at ! bottom ( ! canyon are among ! mo/ anci5t kn[n1 & are ov]la9 uncon=mably by a mass ( tilt$ co>se m>9e s&/ones b1 ^: total ?ickness is n se5 9 ! diagram & measures twelve ?\s& feet p]p5dicul>ly to ! dip4 ,bo? a & b rise to a common level nn & ^u !m re/ ! horizontal sea-laid /rata c1 9 :i* ! upp] portion ( ! canyon has be5 cut4 ,illu/ration3 ,fig4 #bjg4 ,diagram ( ,wall ( ! ,colorado ,canyon1 ,arizona1 %[+ ,uncon=mities ,note t ! cry/all9e rocks a h be5 crumpl$ & cru%$4 ,comp>+ _! /ructure ) t ( fold$ m\nta9s1 :at d y inf] z to _! relief aft] _! de=mation8 ,to :i* surface 7 !y fir/ worn d[n1 mm or nm8 ,describe & acc\nt = ! surface mm4 ,h[ does x diff] f ! surface ( ! cry/all9e rocks se5 9 ! ,torridonian ,m\nta9s 7,fig4 #bjf71 & :y8 ,?is surface mm is "o ( ! olde/ l& surfaces ( :i* any ve/ige rema9s4 ,x is a bit ( fossil geography buri$ f view s9ce ! e>lie/ geological ages & rec5tly br\ght to light by ! erosion ( ! canyon4 ,illu/ration3 ,fig4 #bjh4 ,view ( ! ,nor? ,wall ( ! ,gr& ,canyon ( ! ,colorado ,riv]1 ,arizona1 %[+ ! ,uncon=mities illu/rat$ 9 ,figure #bjg ,h[ did ! surface mm come to receive its cov] ( s&/ones b8 ,f ! ?ickness & co>s5ess ( ^! s$im5ts draw inf]5ces z to ! l& mass f :i* !y 7 d]iv$4 ,0 x ris+ or subsid+8 high or l[8 ,7 its /reams sl[ or swift8 ,0 ! am\nt ( erosion small or great8 ,note ! /rong dip ( ^! s&/ones b4 ,0 ! surface mm tilt$ z n[ :5 ! s&/ones 7 deposit$ ^u x8 ,:5 0 x tilt$8 ,draw a diagram %[+ ! attitude ( ! rocks aft] ?is tilt+ occurr$1 & _! height relative to sea level4 ,! surface nn is rem>kably ev51 al?\gh div]sifi$ by "s l[ hills :i* rise into ! b$d$ rocks ( c1 & x may be trac$ = long di/ances up & d[n ! canyon4 ,7 ! lay]s ( b & ! surface mm always ?us cut %ort by nn z n[8 ,:at has made ! surface nn s ev58 ,h[ does x come to cross ! h>d cry/all9e rocks a & ! weak] s&/ones b at ! same imp>tial level8 ,h[ did ! s$im5ts ( c come to be laid ^u x8 ,give n[ ! entire hi/ory record$ 9 ! section1 & 9 addition t involv$ 9 ! production ( ! plat=m ,p1 %[n 9 ,figure #acj1 & t ( ! cutt+ ( ! canyon4 ,h[ does ! "t involv$ 9 ! cutt+ ( ! canyon comp>e ) t requir$ = ! production ( ! surfaces mm1 nn1 & ,p8 ,,*apt] ,x ,,e>?quakes ,any sudd5 movem5t ( ! rocks ( ! cru/1 z :5 !y te> ap>t :5 a fissure is =m$ or ext5d$1 or slip f "t to "t along a gr[+ fault1 produces a j> call$ an e>?quake1 :i* spreads 9 all directions f ! place ( di/urbance4 ,! ,*>le/on e>?quake4 ,on ! ev5+ ( ,augu/ #ca1 #ahhf1 ! city ( ,*>le/on1 ,s4,c41 0 %ak5 by "o ( ! greate/ e>?quakes :i* has occurr$ 9 ! ,unit$ ,/ates4 ,a slight tremor :i* rattl$ ! w9d[s 0 foll[$ a few seconds lat] by a ro>1 z ( subt]ranean ?und]1 z ! ma9 %ock pass$ b5ea? ! city4 ,h\ses sway$ to & fro1 & _! heav+ floors ov]turn$ furniture & ?rew p]sons (f _! feet z1 dizzy & nauseat$1 !y ru%$ to ! doors = safety4 ,9 sixty seconds a numb] ( h\ses 7 completely wreck$1 f\rte5 ?\s& *imneys 7 toppl$ ov]1 & 9 all ! city sc>cely a build+ 0 left )\t s]i\s injury4 ,9 ! vic9ity ( ,*>le/on railways 7 twi/$ & tra9s d]ail$4 ,fissures op5$ 9 ! loose sup]ficial deposits1 & 9 places sp\t$ wat] m+l$ ) s& f %all[ und]ly+ aquif]s4 ,! po9t ( orig91 or focus1 ( ! e>?quake 0 inf]r$ f subsequ5t inve/igations to be a r5t 9 ! rocks ab\t twelve miles b5ea? ! surface4 ,f ! c5t] ( greate/ di/urbance1 :i* lay above ! focus1 a few miles nor?we/ ( ! city1 ! surface %ock travel$ outw>d 9 e direction1 ) decreas+ effects1 at ! rate ( ne>ly two hundr$ miles p] m9ute4 ,x 0 felt f ,bo/on to ,cuba1 & f ea/]n ,i[a to ! ,b]mudas1 ov] a circul> area ^: diamet] 0 a ?\s& miles4 ,an e>?quake is transmitt$ f ! focus ?r\gh ! ela/ic rocks ( ! cru/1 z a wave1 or s]ies ( waves1 ( compression & r>efaction1 mu* z a s\nd wave is transmitt$ ?r\gh ! ela/ic m$ium ( ! air4 ,ea* e>? p>ticle vibrates ) exce$+ swiftness1 b ov] a v %ort pa?4 ,! sw+ ( a p>ticle 9 firm rock seldom exce$s "o t5? ( an in* 9 ord9>y e>?quakes1 & :5 x rea*es "o half an in* & an in*1 ! movem5t becomes dang]\s & de/ructive4 ,illu/ration3 ,fig4 #baj4 ,block ( ! ,e>?'s ,cru/ %ak5 by an ,e>?quake x1 focus2 a1 b1 c1 d1 successive sph]oidal waves 9 ! cru/2 a1 b1 c1 d1 successive surface waves produc$ by ! outcropp+ ( a1 b1 c1 & d ,! velocity ( e>?quake waves1 l t ( all ela/ic waves1 v>ies ) ! temp]ature & ela/icity ( ! m$ium4 ,9 ! deep1 hot1 ela/ic rocks !y spe$ fa/] ?an 9 ! cold & brok5 rocks ne> ! surface4 ,! deep] ! po9t ( orig9 & ! m viol5t ! initial %ock1 ! fa/] & f>!r d ! vibrations run4 ,great e>?quakes1 caus$ by "s sudd5 displacem5t or "s viol5t r5d+ ( ! rocks1 %ake ! entire planet4 ,_! waves run ?r\gh ! body ( ! e>? at ! rate ( ab\t ?ree hundr$ & fifty miles a m9ute1 & m sl[ly r\nd its circumf]5ce1 regi/]+ _! arrival at opposite sides ( ! globe on ! exce$+ly delicate in/rum5ts ( mod]n e>?quake obs]vatories4 ,geological effects4 ,ev5 great e>?quakes seldom produce geological effects ( mu* importance4 ,l&slides may be %ak5 d[n f ! sides ( m\nta9s & hills1 & cracks may be op5$ 9 ! surface deposits ( pla9s2 b ! transi5t %iv]1 :i* may ov]turn cities & de/roy ?\s&s ( human lives1 runs ?r\gh ! cru/ & leaves x mu* ! same z be=e4 ,e>?quakes att5d+ great displacem5ts4 ,great e>?quakes frequ5tly att5d ! displacem5t ( l>ge masses ( ! rocks ( ! cru/4 ,9 #ahbb ! coa/ ( ,*ile 0 sudd5ly rais$ ?ree or f\r feet1 & ! rise 0 five or six feet a mile inl&4 ,9 #ahce ! same region 0 aga9 upheav$ f two to t5 feet4 ,9 ea* in/ance a de/ructive e>?quake 0 felt = "o ?\s& miles along ! coa/4 ,! great ,cali=nia e>?quake ( #aijf4 ,a sudd5 dislocation occurr$ 9 #aijf along an anci5t fault plane :i* ext5ds = #cjj miles ?r\gh we/]n ,cali=nia4 ,! v]tical displacem5t did n exce$ f\r feet1 :ile ! horizontal %ift+ rea*$ a maximum ( tw5ty feet4 ,f5ces1 r[s ( trees1 & roads :i* cross$ ! fault 7 brok5 & (fset4 ,! latitude & longitude ( all po9ts ov] ?\s&s ( squ>e miles 7 *ang$4 ,on ea* side ( ! fault ! e>? blocks mov$ 9 opposite directions1 ! block on ! ea/ mov+ s\?w>d & t on ! we/ mov+ nor?w>d & to twice ! di/ance4 ,ea/ & we/ ( ! fault ! movem5ts less5$ ) increas+ di/ance f x4 ,?is sudd5 slip set up an e>?quake la/+ sixty-five seconds1 foll[$ by m9or %ocks recurr+ = _m days4 ,9 places ! j> %ook d[n ! wa/e on /eep hillsides1 snapp$ (f or uproot$ trees1 & rock$ h\ses f _! f\ndations or ?rew d[n _! walls or *imneys4 ,! wat] ma9s ( ,san ,francisco 7 brok51 & ! city 0 ?us left def5seless aga9/ a conflagration :i* de/roy$ #ejj1jjj1jjj wor? ( prop]ty4 ,! de/ructive effects v>i$ ) ! nature ( ! gr\nd4 ,build+s on firm rock suff]$ lea/1 :ile ^? on deep alluvium 7 sev]ely %ak5 by ! undulations1 l wat] waves1 into :i* ! loose mat]ial 0 ?r[n4 ,well-brac$ /eel /ructures1 ev5 ( ! l>ge/ size1 7 e>?quake pro(1 & build+s ( o!r mat]ials1 :5 hone/ly built & intellig5tly design$ to )/& e>?quake %ocks1 usually suff]$ little injury4 ,! l5g? ( ! int]vals betwe5 sev]e e>?quakes 9 we/]n ,cali=nia %[s t a great dislocation s relieves ! /resses ( ! adjac5t e>? blocks t scores ( ye>s may elapse be=e ! /resses aga9 accumulate & cause ano!r dislocation4 ,p]haps ! mo/ viol5t e>?quake :i* ev] visit$ ! ,unit$ ,/ates att5d$ ! depression1 9 #ahab1 ( a region sev5ty-five miles long & ?irty miles wide1 ne> ,new ,madrid1 ,mo4 ,mu* ( ! area 0 conv]t$ into swamps & "s into %all[ lakes1 :ile a region tw5ty miles 9 diamet] 0 bulg$ up a?w>t ! *annel ( ! ,mississippi4 ,slight quakes are /ill felt 9 ?is region f "t to "t1 %[+ t ! /ra9s to :i* ! dislocation 0 due h n yet be5 fully reliev$4 ,e>?quakes orig9at+ b5ea? ! sea4 ,_m e>?quakes orig9ate b5ea? ! sea1 & 9 a numb] ( examples !y seem to h be5 accompani$1 z s\nd+s indicate1 by local subsid5ces ( ! ocean bottom4 ,!re h be5 in/ances :]e ! displacem5t has be5 suffici5t to set ! entire ,pacific ,ocean pulsat+ = _m h\rs4 ,9 mid ocean ! wave ?us produc$ has a height ( only a few feet1 :ile x may be two hundr$ miles 9 wid?4 ,on %ores ne> ! po9t ( orig9 de/ructive waves two or ?ree score feet 9 height roll 91 & on coa/s ?\s&s ( miles di/ant ! expir+ undulations may be /ill able to record !mselves on tidal gauges4 ,di/ribution ( e>?quakes4 ,e half h\r "s consid]able area ( ! e>?'s surface is s5sibly %ak5 by an e>?quake1 b e>?quakes are by no means uni=mly di/ribut$ ov] ! globe4 ,z we might inf] f :at we "k z to _! causes1 e>?quakes are mo/ frequ5t 9 regions n[ und]go+ de=mation4 ,su* are "y ris+ m\nta9 ranges1 fault l9es :]e readju/m5ts recur f "t to "t1 & ! slopes ( suboceanic depressions ^: /eepness sugge/s t subsid5ce may !re be 9 progress4 ,e>?quakes1 (t5 ( extreme sev]ity1 frequ5tly visit ! l(ty & "y ranges ( ! ,&es1 :ile !y are little kn[n 9 ! subdu$ old m\nta9s ( ,brazil4 ,! ,highl&s ( ,scotl& are cross$ by a deep & s+ul>ly /raight depression call$ ! ,great ,gl51 :i* has be5 excavat$ along a v anci5t l9e ( dislocation4 ,! e>?quakes :i* occur f "t to "t 9 ?is region1 su* z ! ,inv]ness e>?quake 9 #ahia1 are ref]r$ to slight slips along ?is fault plane4 ,9 ,japan1 e>?quakes are v frequ5t4 ,m ?an a ?\s& are record$ e ye>1 & tw5ty-n9e _w-%ak+ e>?quakes occurr$ 9 ! ?ree ye>s end+ ) #aija4 ,!y orig9ate1 = ! mo/ "p1 well d[n on ! ea/]n flank ( ! e>? fold ^: summit is ! m\nta9\s cre/ ( ! isl&s1 & :i* plunges /eeply b5ea? ! sea to ! abyss ( ! ,tusc>ora ,deep4 ,m9or causes ( e>?quakes4 ,s9ce any concussion )9 ! cru/ sets up an e>? j>1 !re are sev]al m9or causes ( e>?quakes1 su* z volcanic explosions & ev5 ! collapse ( ! ro(s ( caves4 ,! e>?quakes :i* att5d ! eruption ( volcanoes are local1 ev5 9 ! case ( ! mo/ viol5t volcanic p>oxysms kn[n4 ,:5 ! top ( a volcano has be5 bl[n to fragm5ts1 ! accompany+ e>? %ock has sometimes n be5 felt m ?an tw5ty-five miles away4 ,dep? ( focus4 ,! focus ( ! ,*>le/on e>?quake1 e/imat$ at ab\t twelve miles bel[ ! surface1 0 exceptionally deep4 ,volcanic e>?quakes are p>ticul>ly %all[1 & probably no e>?quakes kn[n h />t$ at a great] dep? ?an fifte5 or tw5ty miles4 ,?is di/ance is s slight comp>$ ) ! e>?'s radius t we may say t e>?quakes are b sk9-deep4 ,%\ld y expect ! velocity ( an e>?quake to be great] 9 a p5epla9 or 9 a riv] delta8 ,aft] an e>?quake1 piles on :i* build+s re/$ 7 f\nd driv5 into ! gr\nd1 & *imneys cru%$ at base4 ,f :at direction did ! %ock come8 ,*imneys /&+ on ! s\? walls ( h\ses toppl$ ov] on ! ro(4 ,%\ld y inf] t ! %ock 9 ?is case came f ! nor? or s\?8 ,h[ %\ld y expect a %ock f ! ea/ to affect pictures hang+ on ! ea/ & ! we/ walls ( a room8 h[ ! pictures hang+ on ! nor? & ! s\? walls8 ,9 p>ts ( ! c\ntry1 z 9 s\?we/]n ,wiscons91 sl5d] erosion pill>s1 or monum5ts1 are common4 ,:at inf]5ce c\ld y draw z to ! occurr5ce 9 su* regions ( sev]e e>?quakes 9 ! rec5t pa/8 ,,*apt] ,,xi ,,volcanoes ,connect$ ) movem5ts ( ! e>?'s cru/ :i* take place s sl[ly t !y c be inf]r$ only f _! effects is "o ( ! mo/ rapid & impressive ( all geological processes1--! extrusion ( molt5 rock f b5ea? ! surface ( ! e>?1 giv+ rise to all ! v>i\s ph5om5a ( volcanoes4 ,9 a volcano1 molt5 rock f a region deep bel[1 :i* we may call its res]voir1 asc5ds ?r\gh a pipe or fissure to ! surface4 ,! mat]ials erupt$ may be spread ov] va/ areas1 or1 z is commonly ! case1 may accumulate ab\t ! op5+1 =m+ a conical pile kn[n z ! volcanic cone4 ,x is to ?is cone t popul> usage ref]s ! ^w volcano2 b ! cone is simply a conspicu\s "p ( ! volcanic me*anism ^: /ill m important p>ts1 ! res]voir & ! pipe1 are hidd5 f view4 ,volcanic eruptions are ( two types1--effusive eruptions1 9 :i* molt5 rock wells up f bel[ & fl[s =? 9 /reams ( lava 7a compreh5sive t]m appli$ to all k9ds ( rock emitt$ f volcanoes 9 a molt5 /ate71 & explosive eruptions1 9 :i* ! rock is bl[n out 9 fragm5ts great & small by ! expansive =ce ( /eam4 ,eruptions ( ! ,effusive ,type ,! ,hawaiian volcanoes4 ,! ,hawaiian ,isl&s are all volcanic 9 orig91 & h a l9e> arrangem5t *>act]i/ic ( _m volcanic gr\ps 9 all p>ts ( ! _w4 ,!y are /rung along a nor?we/-s\!a/ l9e1 _! volcanoes /&+ 9 two p>allel r[s z if re>$ along two adjac5t l9es ( fracture or fold+4 ,9 ! nor?we/]n isl&s ! volcanoes h long be5 ext9ct & are worn l[ by erosion4 ,9 ! s\!a/]n isl&4 ,hawaii1 ?ree volcanoes are /ill active & 9 process ( build+4 ,( ^! ,mauna ,loa1 ! mon>* ( volcanoes1 ) a gir? ( two hundr$ miles & a height ( ne>ly f\rte5 ?\s& feet above sea level1 is a lava dome ! slope ( ^: sides does n av]age m ?an five degrees4 ,on ! summit is an elliptical bas9 t5 miles 9 circumf]5ce & sev]al hundr$ feet deep4 ,conc5tric cracks surr\nd ! rim1 & f "t to "t ! bas9 is enl>g$ z great slices are deta*$ f ! v]tical walls & engulf$4 ,su* a volcanic bas91 =m$ by ! ins9k+ ( ! top ( ! cone1 is call$ a cald]a4 ,illu/ration3 ,fig4 #baa4 ,mauna ,loa ,illu/ration3 ,fig4 #bab4 ,cald]a ( ,mauna ,loa ,on ! flanks ( ,mauna ,loa1 f\r ?\s& feet above sea level1 lies ! cald]a ( ,kilauea1 an indep5d5t volcano ^: dome has be5 jo9$ to ! l>g] m\nta9 by ! gradual gr[? ( ! two4 ,9 ea* cald]a ! floor1 :i* to ! eye is a pla9 ( black lava1 is ! congeal$ surface ( a column ( molt5 rock4 ,at times ( an eruption lakes ( boil+ lava appe> :i* may be comp>$ to air holes 9 a froz5 riv]4 ,great waves surge up1 lift+ tons ( ! fi]y liquid a score ( feet 9 air1 to fall back ) a mighty plunge & ro>1 & occasionally ! lava rises sev]al hundr$ feet 9 f\nta9s ( dazzl+ brightness4 ,! lava lakes may flood ! floor ( ! bas91 b 9 hi/oric times h nev] be5 kn[n to fill x & ov]fl[ ! rim4 ,in/ead1 ! heavy column ( lava breaks way ?r\gh ! sides ( ! m\nta9 & dis*>ges 9 /reams :i* fl[ d[n ! m\nta9 slopes = a di/ance sometimes ( z mu* z ?irty-five miles4 ,) ! draw+ (f ( ! lava ! column 9 ! duct ( ! volcano l[]s1 & ! floor ( ! cald]a :olly or 9 "p subsides4 ,a black & /eam+ abyss m>ks ! place ( ! lava lakes 7,fig4 #bac74 ,aft] a "t ! lava rises 9 ! duct1 ! floor is float$ high]1 & ! boil+ lakes reappe>4 ,illu/ration3 ,fig4 #bac4 ,portion ( ,cald]a ( ,kilauea aft] ,collapse foll[+ an ,eruption ,! eruptions ( ! ,hawaiian volcanoes are ?us ( ! effusive type4 ,! column ( lava rises1 breaks ?r\gh ! side ( ! m\nta91 & dis*>ges 9 lava /reams4 ,!re are no explosions1 & usually no e>?quakes1 or v slight ones1 accompany ! eruptions4 ,! lava 9 ! cald]as boils because ( escap+ /eam1 b ! vapor emitt$ is comp>atively little1 & seldom hangs above ! summits 9 heavy cl\ds4 ,we see "h 9 its simple/ =m ! mo/ impressive & important fact 9 all volcanic action1 molt5 rock has be5 driv5 upw>d to ! surface f "s deep-ly+ s\rce4 ,lava fl[s4 ,z lava issues f ! side ( a volcano or ov]fl[s f ! summit1 x fl[s away 9 a gl[+ /ream resembl+ molt5 iron drawn :ite-hot f an iron furnace4 ,! surface ( ! /ream soon cools & black5s1 & ! h>d cru/ ( nonconduct+ rock may gr[ ?ick & firm en\gh to =m a tunnel1 )9 :i* ! fluid lava may fl[ f> be=e x loses its heat to any m>k$ degree4 ,su* tunnels may at la/ be left z caves by ! dra9+ away ( ! lava1 & are sometimes sev]al miles 9 l5g?4 ,illu/ration3 ,fig4 #bad4 ,pahoehoe ,lava1 ,hawaii ,pahoehoe & aa4 ,:5 ! cru/ ( highly fluid lava rema9s unbrok5 aft] its fir/ freez+1 x pres5ts a smoo?1 hummocky1 & ropy surface kn[n by ! ,hawaiian t]m pahoehoe 7,fig4 #bad74 ,on ! o!r h&1 ! cru/ ( a viscid fl[ may be brok5 & spl9t]$ z x is dragg$ along by ! sl[ly mov+ mass b5ea?4 ,! /ream !n appe>s z a field ( /ones clank+ & gr9d+ on1 ) "h & !re f "s *9k a dull r$ gl[ or a wisp ( /eam4 ,x sets to a surface call$ aa1 ( brok51 %>p-edg$ blocks1 :i* is (t5 bo? difficult & dang]\s to trav]se 7,fig4 #bae74 ,illu/ration3 ,fig4 #bae4 ,lava ,fl[ ( ! ,aa ,type1 ,c9d] ,cones 9 ! ,di/ance1 ,arizona ,fissure eruptions4 ,"s ( ! l>ge/ & mo/ important outfl[s ( lava h n be5 connect$ ) volcanic cones1 b h be5 dis*>g$ f fissures1 flood+ ! c\ntry f> & wide ) molt5 rock4 ,%eet aft] %eet ( molt5 rock has be5 successively outp\r$1 & !re h be5 built up1 lay] ^u lay]1 plateaus ( lava ?\s&s ( feet 9 ?ickness & _m ?\s&s ( squ>e miles 9 area4 ,icel&4 ,?is isl& plateau has be5 r5t f "t to "t by fissures f :i* floods ( lava h outp\r$4 ,9 "s in/ances ! lava dis*>ges along ! :ole l5g? ( ! fissure1 b m (t5 only at c]ta9 po9ts ^u x4 ,! ,laki fissure1 tw5ty miles long1 0 9 eruption 9 #aghc = sev5 mon?s4 ,! inundation ( fluid rock :i* p\r$ f x is ! l>ge/ ( hi/oric record1 rea*+ a di/ance ( =ty-sev5 miles & cov]+ two hundr$ & tw5ty squ>e miles to an av]age dep? ( a hundr$ feet4 ,at ! pres5t "t ! fissure is trac$ by a l9e ( sev]al hundr$ insignificant m\nds ( fragm5tal mat]ials :i* m>k :]e ! lava issu$ 7,fig4 #baf74 ,! di/ance to :i* ! fissure eruptions ( ,icel& fl[ on slopes extremely g5tle is notewor?y4 ,"o su* /ream is n9ety miles 9 l5g?1 & ano!r sev5ty miles long has a slope ( little m ?an "o half a degree4 ,:]e lava is emitt$ at "o po9t & fl[s to a less di/ance !re is gradually built up a dome ( ! %ape ( an inv]t$ sauc] ) an imm5se base b comp>atively l[4 ,_m lava domes h be5 discov]$ 9 ,icel&1 al?\gh f _! exce$+ly g5tle slopes1 (t5 b two or ?ree degrees1 !y long escap$ ! notice ( explor]s4 ,! entire plateau ( ,icel&1 a region z l>ge z ,ohio1 is compos$ ( volcanic products1--= ! mo/ "p ( successive %eets ( lava ^: total ?ickness falls little %ort ( two miles4 ,! lava %eets expos$ to view 7 outp\r$ 9 op5 air & n b5ea? ! sea2 = peat bogs & old =e/ gr\nds are int]b$d$ ) !m1 & ! fossil plants ( ^! vegetable deposits prove t ! plateau has long be5 build+ & is v anci5t4 ,on ! /eep sea cliffs ( ! isl&1 :]e its /ructure is exhibit$1 ! %eets ( lava are se5 to be cut ) _m dikes1--fissures :i* h be5 fill$ by molt5 rock1--& !re is little d\bt t x 0 ?r\gh ^! fissures t ! lava outwell$ 9 successive fl[s :i* spread f> & wide ov] ! c\ntry & gradually re>$ ! enorm\s pile ( ! plateau4 ,eruptions ( ! ,explosive ,type ,9 ! majority ( volcanoes ! lava :i* rises 9 ! pipe is at lea/ 9 "p bl[n into fragm5ts ) viol5t explosions & %ot into ! air toge!r ) va/ quantities ( wat] vapor & v>i\s gases4 ,! f9] p>ticles into--:i* ! lava is explod$ are call$ volcanic du/ or volcanic a%es1 & are (t5 c>ri$ long di/ances by ! w9d be=e !y settle to ! e>?4 ,! co>s] fragm5ts fall ab\t ! v5t & !re accumulate 9 a /eep1 conical1 volcanic m\nta94 ,z successive explosions keep op5 ! ?roat ( ! pipe1 !re rema9s on ! summit a cup-%ap$ depression call$ ! crat]4 ,/romboli4 ,to /udy ! nature ( ^! explosions we may visit ,/romboli1 a l[ volcano built *iefly ( fragm5tal mat]ials1 :i* rises f ! sea (f ! nor? coa/ ( ,sicily & is 9 con/ant ?\gh mod]ate action4 ,ov] ! summit hangs a cl\d ( vapor :i* /rik+ly resembles ! column ( smoke puff$ f ! smoke/ack ( a locomotive1 9 t x consi/s ( globul> masses1 ea* ! product ( a di/9ct explosion4 ,at night ! cl\d ( vapor is light$ ) a r$ gl[ at int]vals ( a few m9utes1 l ! gl[ on ! trail ( smoke beh9d ! locomotive :5 f "t to "t ! fire box is op5$4 ,because ( ?is int]mitt5t light fla%+ ?\s&s ( feet above ! sea1 ,/romboli has be5 giv5 ! "n ( ! ,ligh?\se ( ! ,m$it]ranean4 ,look+ d[n into ! crat] ( ! volcano1 "o sees a viscid lava sl[ly see?+4 ,! agitation gradually increases4 ,a great bubble =ms4 ,x bur/s ) an explosion :i* causes ! walls ( ! crat] to quiv] ) a m9iature e>?quake1 & an outru% ( /eam c>ries ! fragm5ts ( ! bubble al(t = a ?\s& feet to fall into ! crat] or on ! m\nta9 side ab\t x4 ,) ! explosion ! cool$ & d>k5$ cru/ ( ! lava is remov$1 & ! light ( ! inc&esc5t liquid b5ea? is reflect$ f ! cl\d ( vapor :i* ov]hangs ! cone4 ,at ,/romboli we le>n ! lesson t ! explosive =ce 9 volcanoes is t ( /eam4 ,! lava 9 ! pipe is p]meat$ ) x mu* z is a ?ick boil+ porridge4 ,! /eam 9 boil+ porridge is unable to escape freely & ga!rs into bubbles :i* 9 break+ spurt out drops ( ! pa/y sub/ance2 9 ! same way ! explosion ( great bubbles ( /eam 9 ! viscid lava %oots clots & fragm5ts ( x into ! air4 ,krakatoa4 ,! mo/ viol5t eruption ( hi/ory1 t ( ,krakatoa1 a small volcanic isl& 9 ! /rait betwe5 ,sumatra & ,java1 occurr$ 9 ! la/ week ( ,augu/1 #ahhc4 ,cont9u\s explosions %ot a column ( /eam & a%es4 sev5te5 miles 9 air4 ,a black cl\d1 b5ea? :i* 0 midnight d>kness & f :i* fell a ra9 ( a%es & /ones1 ov]spread ! surr\nd+ region to a di/ance ( "o hundr$ & fifty miles4 ,laun*$ on ! curr5ts ( ! upp] air1 ! du/ 0 swiftly c>ri$ we/w>d to long di/ances4 ,?ree days aft] ! eruption x fell on ! deck ( a %ip sixte5 hundr$ miles away1 & 9 ?irte5 days ! f9e/ impalpable p[d] f ! volcano _h float$ r\nd ! globe4 ,= _m mon?s ! du/ hung ov] ,europe & ,am]ica z a fa9t l(ty haze illum9at$ at sunrise & sunset ) brilliant crimson4 ,9 c\ntries ne>] ! eruption1 z 9 ,india & ,africa1 ! haze = "s "t 0 s ?ick t x color$ sun & moon ) blue1 gre51 & copp]-r$ t9ts & encircl$ !m ) coronas4 ,at a di/ance ( ev5 a ?\s& miles ! detonations ( ! eruption s\nd$ l ! boom+ ( heavy guns a few miles away4 ,9 "o direction !y 7 audible = a di/ance z great z t f ,san ,francisco to ,clevel&4 ,! entire atmosph]e 0 ?r[n into undulations "u :i* all b>omet]s rose & fell z ! air waves ?rice encircl$ ! e>?4 ,! %ock ( ! explosions rais$ sea waves :i* swept r\nd ! adjac5t %ores at a height ( m ?an fifty feet1 & :i* 7 p]ceptible halfway ar\nd ! globe4 ,at ! close ( ! eruption x 0 f\nd t half ! m\nta9 _h be5 bl[n away1 & t :]e ! c5tral "p ( ! isl& _h be5 ! sea 0 a ?\s& feet deep4 ,m>t9ique & ,/4 ,v9c5t4 ,9 #aijb two dormant volcanoes ( ! ,we/ ,indies1 ,mt4 ,pelee 9 ,m>t9ique & ,s\frire 9 ,/4 ,v9c5t1 broke into eruption simultane\sly4 ,no lava 0 emitt$1 b !re 7 bl[n into ! air great quantities ( a%es1 :i* mantl$ ! adjac5t p>ts ( ! isl&s ) a pall z ( gray sn[4 ,9 e>ly /ages ( ! eruption lakes :i* occupi$ old crat]s 7 dis*>g$ & swept d[n ! a%-cov]$ m\nta9 valleys 9 torr5ts ( boil+ mud4 ,on sev]al occasions !re 0 %ot f ! crat] ( ea* volcano a ?ick & heavy cl\d ( inc&esc5t a%es & /eam1 :i* ru%$ d[n ! m\nta9 side l an avalan*e1 r$ ) gl[+ /ones & sc9tillat+ ) lightn+ fla%es4 ,=e/s & build+s 9 its pa? 7 level$ z by a tornado1 wood 0 *>r$ & set on fire by ! inc&esc5t fragm5ts1 all vegetation 0 de/roy$1 & to brea! ! /eam & hot1 suffocat+ du/ ( ! cl\d 0 dea? to e liv+ creature4 ,on ! morn+ ( ! #h? ( ,may1 #aijb1 ! fir/ ( ^! peculi> avalan*es f ,mt4 ,pelee fell on ! city ( ,/4 ,pi]re & in/antly de/roy$ ! lives ( its ?irty ?\s& inhabitants4 ,illu/ration3 ,fig4 #bai4 ,an ,eruption ( ,vesuvius1 #ahgb ,! eruptions ( _m volcanoes p>take ( bo? ! effusive & ! explosive types3 ! molt5 rock 9 ! pipe is 9 "p bl[n into ! air ) explosions ( /eam1 & 9 "p is dis*>g$ 9 /reams ( lava ov] ! lip ( ! crat] & f fissures 9 ! sides ( ! cone4 ,su* are ! eruptions ( ,vesuvius1 "o ( :i* is illu/rat$ 9 ,figure #bai4 ,subm>9e eruptions4 ,! _m volcanic isl&s ( ! ocean & ! coral isl&s re/+ on subm]g$ volcanic peaks prove t eruptions h (t5 tak5 place ^u ! ocean floor & h !re built up enorm\s piles ( volcanic fragm5ts & lava4 ,! ,hawaiian volcanoes rise f a dep? ( eighte5 ?\s& feet ( wat] & lift _! heads to ab\t ?irty ?\s& feet above ! ocean b$4 ,*ri/mas ,isl& 7see p4 #aid71 built :olly b5ea? ! ocean1 is a coral-capp$ volcanic peak1 ^: total height1 z measur$ f ! bottom ( ! sea1 is m ?an fifte5 ?\s& feet4 ,deep-sea s\nd+s h reveal$ ! pres5ce ( num]\s peaks :i* fail to rea* sea level & :i* no d\bt are subm>9e volcanoes4 ,a numb] ( volcanoes on ! l& 7 subm>9e 9 _! e>ly /ages1 z1 = example1 ! va/ pile ( ,etna1 ! celebrat$ ,sicilian volcano1 :i* re/s on /ratifi$ volcanic fragm5ts conta9+ m>9e %ells n[ uplift$ f ! sea4 ,subm>9e outfl[s ( lava & deposits ( volcanic fragm5ts become cov]$ ) s$im5ts dur+ ! long int]vals betwe5 eruptions4 ,su* volcanic deposits are said to be contemporane\s1 because !y are =m$ dur+ ! same p]iod z ! /rata among :i* !y are imb$d$4 ,contemporane\s lava %eets may be expect$ to bake ! surface ( ! /ratum on :i* !y re/1 :ile ! s$im5ts deposit$ ^u !m are unalt]$ by _! heat4 ,!y are among ! mo/ p]man5t records ( volcanic action1 f> outla/+ ! greate/ volcanic m\nta9s built 9 op5 air4 ,f uprais$ subm>9e volcanoes1 su* z ,*ri/mas ,isl&1 x is le>n$ t lava fl[s :i* are p\r$ out ^u ! bottom ( ! sea d n diff] mat]ially ei!r 9 composition or texture f ^? ( ! l&4 ,volcanic ,products ,va/ am\nts ( /eam are1 z we h se51 emitt$ f volcanoes1 & comp>atively small quantities ( o!r vapors1 su* z v>i\s acid & sulphur\s gases4 ,! rocks erupt$ f volcanoes diff] widely 9 *emical composition & 9 texture4 ,illu/ration3 ,fig4 #bbj4 ,cellul> ,lava ,acidic & basic lavas4 ,two classes ( volcanic rocks may be di/+ui%$1--^? conta9+ a l>ge proportion ( silica 7silicic acid1 ,si,o#b7 & !re=e call$ acidic1 & ^? conta9+ less silica & a l>g] proportion ( ! bases 7lime1 magnesia1 soda1 etc47 & !re=e call$ basic4 ,! acidic lavas1 ( :i* rhyolite & ?ra*yte are examples1 are comp>atively light 9 color & weight1 & are difficult to melt4 ,! basic lavas1 ( :i* basalt is a type1 are d>k & heavy & melt at a l[] temp]ature4 ,scoria & pumice4 ,! texture ( volcanic rocks dep5ds 9 "p on ! degree to :i* !y 7 di/5d$ by ! /eam :i* p]meat$ !m :5 9 a molt5 /ate4 ,!y h>d5 into compact rock :]e ! /eam _c exp&4 ,:]e ! /eam is releas$ f pressure1 z on ! surface ( a lava /ream1 x =ms bubbles 7/eam blebs7 ( v>i\s sizes1 :i* give ! h>d5$ rock a cellul> /ructure 7,fig4 #bbj71 ,9 ?is way are =m$ ! r\gh slags & cl9k]s call$ scoria1 :i* are f\nd on ! surface ( fl[s & :i* are also ?r[n out z clots ( lava 9 explosive eruptions4 ,on ! surface ( ! see?+ lava 9 ! ?roat ( ! volcano !re ga!rs a rock foam1 :i*1 :5 hurl$ into ! air1 is cool$ & falls z pumice1--a spongy gray rock s light t x floats on wat]4 ,illu/ration3 ,fig4 #bba4 ,amygdules 9 ,lava ,amygdules4 ,! /eam blebs ( lava fl[s are (t5 drawn out f a sph]ical to an elliptical =m resembl+ t ( an almond1 & aft] ! rock has cool$ ^! cavities are gradually fill$ ) m9]als deposit$ f solution by und]gr\nd wat]4 ,f _! %ape su* ca/s are call$ amygdules 7,greek1 amygdalon1 an almond74 ,amygdules are commonly compos$ ( silica4 ,lavas conta9 bo? silica & ! alkalies1 pota% & soda1 & aft] dissolv+ ! alkalies1 p]colat+ wat] is able to take silica also into solution4 ,mo/ agates are b&$ amygdules 9 :i* ! silica has be5 laid 9 v>icolor$1 conc5tric lay]s 7,fig4 #bbb74 ,illu/ration3 ,fig4 #bbb4 ,poli%$ ,section ( an ,agate ,illu/ration3 ,fig4 #bbc4 ,microsection %[+ ! ,beg9n+s ( ,cry/al ,gr[? 9 ,glassy ,lava ,glassy & /ony lavas4 ,volcanic rocks diff] 9 texture accord+ also to ! rate at :i* !y h solidifi$4 ,:5 rapidly cool$1 z on ! surface ( a lava fl[1 molt5 rock *ills to a glass1 because ! m9]als ( :i* x is compos$ h n _h "t to sep>ate !mselves f ! fus$ mixture & =m cry/als4 ,"u sl[ cool+1 z 9 ! int]ior ( ! fl[1 x becomes a /ony mass compos$ ( cry/als set 9 a glassy pa/e4 ,9 ?9 slices ( volcanic glass "o may see "u ! microscope ! beg9n+s ( cry/al gr[? 9 filam5ts & ne$les & fea!ry =ms1 :i* are ! rudim5ts ( ! cry/als ( v>i\s m9]als4 ,sph]ulites1 :i* also m>k ! fir/ *anges ( glassy lavas t[>d a /ony condition1 are little balls )9 ! rock1 v>y+ f microscopic size to sev]al in*es 9 diamet]1 & made up ( radiat+ fib]s4 ,p]litic /ructure1 common among glassy lavas1 consi/s ( microscopic curv+ & int]lac+ cracks1 due to contraction4 ,illu/ration3 ,fig4 #bbd4 ,p]litic ,/ructure & ,sph]ulites1 a1 a ,illu/ration3 ,fig4 #bbe4 ,fl[ ,l9es 9 ,lava ,fl[ l9es are exhibit$ by volcanic rocks bo? to ! nak$ eye & "u ! microscope4 ,/eam blebs1 toge!r ) cry/als & _! embryonic =ms1 are left arrang$ 9 l9es & /reaks by ! curr5ts ( ! fl[+ lava z x /iff5$ into rock4 ,illu/ration3 ,fig4 #bbf4 ,porphyritic ,/ructure ,porphyritic /ructure4 ,rocks ^: gr\nd mass has scatt]$ ?r\gh x l>ge conspicu\s cry/als 7,fig4 #bbf7 are said to be porphyritic1 & x is especially among volcanic rocks t ?is /ructure occurs4 ,! gr\nd mass ( porphyries ei!r may be glassy or may consi/ 9 "p ( a felt ( m9ute cry/als2 9 ei!r case x repres5ts ! consolidation ( ! rock aft] its outp\r+ ^u ! surface4 ,on ! o!r h&1 ! l>ge cry/als ( porphyry h sl[ly =m$ deep bel[ ! gr\nd at an e>li] date4 ,column> /ructure4 ,j z wet />* contracts on dry+ to prismatic =ms1 s lava (t5 contracts on cool+ to a mass ( close-set1 prismatic1 & commonly six-sid$ columns1 :i* /& at "r angles to ! cool+ surface4 ,! upp] portion ( a fl[1 on rapid cool+ f ! surface expos$ to ! air1 may contract to a confus$ mass ( small & irregul> prisms2 :ile ! rema9d] =ms l>ge & beautifully regul> columns1 :i* h gr[n upw>d by sl[ cool+ f b5ea? 7,fig4 #bbg74 ,fragm5tal ,mat]ials ,rocks weigh+ _m tons are (t5 ?r[n f a volcano at ! beg9n+ ( an outbur/ by ! break+ up ( ! solidifi$ floor ( ! crat]2 & dur+ ! progress ( an eruption l>ge blocks may be torn f ! ?roat ( ! volcano by ! outru% ( /eam4 ,b ! mo/ important fragm5tal mat]ials are ^? d]iv$ f ! lava itself4 ,z lava rises 9 ! pipe1 ! /eam :i* p]meates x is releas$ f pressure & explodes1 hurl+ ! lava into ! air 9 fragm5ts ( all sizes1--l>ge pieces ( scoria1 lapilli 7fragm5ts ! size ( a pea or walnut71 volcanic s& & volcanic a%es4 ,! latt] resemble 9 appe>ance ! a%es ( wood or coal1 b !y are n 9 any s5se1 l !m1 a residue aft] combu/ion4 ,illu/ration3 ,fig4 #bbg4 ,column> ,/ructure 9 ,basaltic ,lava1 ,scotl& ,volcanic a%es are produc$ 9 sev]al ways3 lava ris+ 9 ! volcanic duct is explod$ into f9e du/ by ! /eam :i* p]meates x2 glassy lava1 hurl$ into ! air & cool$ sudd5ly1 is br\ght into a /ate ( high /ra9 & t5sion1 &1 l ,pr9ce ,rup]t's drops1 flies to pieces at ! lea/ provocation4 ,! cla% ( ris+ & fall+ projectiles also produces "s du/1 a fair sample ( :i* may be made by grat+ toge!r two pieces ( pumice4 ,b$s ( volcanic a% occur widely among rec5t deposits 9 ! we/]n ,unit$ ,/ates4 ,9 ,nebraska a% b$s are f\nd 9 tw5ty c\nties1 & are (t5 z :ite z p[d]$ pumice4 ,! b$s gr[ ?ick] & co>s] t[>d ! s\?we/]n "p ( ! /ate1 :]e _! ?ickness sometimes rea*es fifty feet4 ,9 :at direction w\ld y look = ! n[ ext9ct volcano ^: explosive eruptions are ?us record$8 ,tuff4 ,?is is a conv5i5t t]m designat+ any rock compos$ ( volcanic fragm5ts4 ,co>se tuffs ( angul> fragm5ts are call$ volcanic breccia1 & :5 ! fragm5ts h be5 r\nd$ & sort$ by wat] ! rock is t]m$ a volcanic conglom]ate4 ,ev5 :5 deposit$ 9 ! op5 air1 z on ! slopes ( a volcano1 tuffs may be rudely b$d$ & _! fragm5ts m or less r\nd$1 & unless m>9e %ells or ! rema9s ( l& plants & animals are f\nd z fossils 9 !m1 !re is (t5 consid]able difficulty 9 tell+ :e!r !y 7 laid 9 wat] or 9 air4 ,9 ei!r case !y soon become consolidat$4 ,*emical deposits f p]colat+ wat]s fill ! int]/ices1 & ! b$ ( loose fragm5ts is cem5t$ to h>d rock4 ,! mat]ials ( :i* tuffs are compos$ are easily recogniz$ z volcanic 9 _! orig94 ,! fragm5ts are m or less cellul>1 accord+ to ! degree to :i* !y 7 di/5d$ ) /eam :5 9 a molt5 /ate1 & ev5 9 ! f9e/ du/ "o may see ! glass or ! cry/als ( lava f :i* x 0 d]iv$4 ,tuffs (t5 conta9 volcanic bombs1--balls ( lava :i* took %ape :ile :irl+ 9 ! air1 & solidifi$ be=e fall+ to ! gr\nd4 ,illu/ration3 ,fig4 #bbh4 ,volcanic ,bombs1 ,c9d] ,cone1 ,cali=nia ,illu/ration3 ,fig4 #bbi4 ,a ,volcanic ,cone1 ,arizona ,anci5t volcanic rocks4 ,x is 9 ^! mat]ials & /ructures :i* we h describ$ t volcanoes leave "s ( _! mo/ endur+ records4 ,ev5 ! volcanic rocks ( ! e>lie/ geological ages1 uplift$ aft] long burial b5ea? ! sea & expos$ to view by deep erosion1 are recogniz$ & _! hi/ory read despite ! _m *anges :i* !y may h und]gone4 ,a %eet ( anci5t lava may be di/+ui%$ by its composition f ! s$im5ts among :i* x is imb$d$4 ,! direction ( its fl[ l9es may be not$4 ,! cellul> & slaggy surface :]e ! pa/y lava 0 di/5d$ by escap+ /eam is recogniz$ by ! amygdules :i* n[ fill ! anci5t /eam blebs4 ,9 a pile ( successive %eets ( lava ea* fl[ may be di/+ui%$ & its ?ickness measur$2 = ! surface ( ea* %eet is glassy & scoriace\s1 :ile b5ea? its upp] portions ! lava ( ea* fl[ is m d5se & /ony4 ,! l5g? ( "t :i* elaps$ be=e a %eet 0 buri$ b5ea? ! mat]ials ( succe$+ eruptions may be told by ! am\nt ( wea!r+ :i* x _h und]gone1 ! dep? ( anci5t soil--n[ bak$ to solid rock--^u x1 & ! erosion :i* x _h suff]$ 9 ! int]val4 ,if ! fl[ occurr$ f "s subm>9e volcano1 we may recognize ! fact by ! sea-laid s$im5ts :i* cov] x1 fill+ ! cracks & crevices ( its upp] surface & conta9+ pieces ( lava wa%$ f x 9 _! basal lay]s4 ,long-buri$ glassy lavas devitrify1 or pass to a /ony condition1 "u ! unceas+ action ( und]gr\nd wat]s2 b _! fl[ l9es & p]litic & sph]ulitic /ructures rema9 to tell ( _! orig9al /ate4 ,anci5t tuffs are kn[n by ! fragm5tal "* ( _! volcanic mat]ial1 ev5 ?\gh !y h be5 alt]$ to firm rock4 ,"s rema9s ( l& animals & plants may be f\nd imb$d$ to tell t ! b$s 7 laid 9 op5 air2 :ile ! rema9s ( m>9e organisms w\ld prove z surely t ! tuffs 7 deposit$ 9 ! sea4 ,9 ^! ways anci5t volcanoes h be5 recogniz$ ne> ,bo/on1 9 s\!a/]n ,p5nsylvania1 ab\t ,lake ,sup]ior1 & 9 o!r regions ( ! ,unit$ ,/ates4 ,! ,life ,hi/ory ( a ,volcano ,! invasion ( a region by volcanic =ces is att5d$ by movem5ts ( ! cru/ h]ald$ by e>?quakes4 ,a fissure or a pipe is op5$ & ! build+ ( ! cone or ! spread+ ( wide lava %eets is begun4 ,volcanic cones4 ,! %ape ( a volcanic cone dep5ds *iefly on ! mat]ials erupt$4 ,cones made ( fragm5ts may h sides z /eep z ! angle ( repose1 :i* 9 ! case ( co>se scoria is sometimes z high z ?irty or =ty degrees4 ,ab\t ! base ( ! m\nta9 ! f9] mat]ials erupt$ are spread 9 m g5tle slopes1 & are also wa%$ =w>d by ra9s & /reams4 ,! normal pr(ile is ?us a symmetric cone ) a fl>+ base4 ,illu/ration3 ,fig4 #bcj4 ,s>c\i1 a ,tra*yte ,dome1 ,france ,cones built ( lava v>y 9 =m accord+ to ! liquidity ( ! lava4 ,domes ( g5tle slope1 z ^? ( ,hawaii1 = example1 are =m$ ( basalt1 :i* fl[s to long di/ances be=e x congeals4 ,:5 sup]heat$ & emitt$ f _m v5ts1 ?is easily melt$ lava builds great plateaus1 su* z t ( ,icel&4 ,on ! o!r h&1 lavas less fusible1 or p\r$ out at a l[] temp]ature1 /iff5 :5 !y h fl[$ b a %ort di/ance1 & accumulate 9 a /eep cone4 ,tra*yte has be5 extrud$ 9 a /ate s viscid t x has =m$ /eep-sid$ domes l t ( ,s>c\i 7,fig4 #bcj74 ,mo/ volcanoes are built1 l ,vesuvius1 bo? ( lava fl[s & ( tuffs1 & sections %[ t ! /ructure ( ! cone consi/s ( outw>d-dipp+1 alt]nat+ lay]s ( lava1 scoria1 & a%es4 ,illu/ration3 ,fig4 #bca4 ,section ( ,vesuvius ,v1 ,vesuvius2 ,s1 ,somma1 a m\nta9\s ramp>t half encircl+ ,vesuvius1 & l x built ( outw>d-dipp+ %eets ( tuff & lava2 a1 cry/all9e rocks2 b1 m>9e /rata2 c1 tuffs conta9+ sea%ells4 ,:i* is ! old] m\nta91 ,vesuvius or ,somma8 ,( :at is ,somma a remnant8 ,draw a diagram %[+ its orig9al outl9e4 ,sugge/ :at processes may h br\ght x to its pres5t =m4 ,:at record d y f9d ( ! e>lie/ volcanic activity8 ,:at d y inf] z to ! beg9n+s ( ! volcano8 ,f "t to "t ! cone is r5t by ! viol5ce ( explosions & by ! weight ( ! column ( lava 9 ! pipe4 ,! fissures are fill$ ) lava & "s dis*>ge on ! sides ( ! m\nta91 build+ p>asitic cones1 :ile all =m dikes1 :i* /r5g!n ! pile ) ribs ( h>d rock & make x m difficult to r5d4 ,great cata/rophes are record$ 9 ! %ape ( "s volcanoes :i* consi/ ( a circul> rim p]haps miles 9 diamet]1 inclos+ a va/ crat] or a cald]a )9 :i* small cones may rise4 ,we may inf] t at "s "t ! top ( ! m\nta9 has be5 bl[n (f1 or has collaps$ & be5 engulf$ because "s res]voir b5ea? _h be5 empti$ by long-cont9u$ eruptions 7,fig4 #bcj74 ,! cone-build+ /age may be said to cont9ue until eruptions ( lava & fragm5tal mat]ials cease altoge!r4 ,soon] or lat] ! volcanic =ces %ift or die away1 & no fur!r eruptions add to ! pile or replace its losses by erosion dur+ p]iods ( repose4 ,gases h[ev] are /ill emitt$1 &1 z sulphur vapors are conspicu\s among !m1 su* v5ts are call$ solfat>as4 ,m\nt ,hood1 9 ,oregon1 is an example ( a volcano sunk to ?is /age4 ,f a /eam+ rift on its side !re rise sulphur\s fumes :i*1 half a mile d[n ! w9d1 w t>ni% a silv] co94 ,illu/ration3 ,fig4 #bcb4 ,crat] ,lake1 ,oregon ,h[ wide & deep is ! bas9 :i* holds ! lake8 ,! m\nta9 walls :i* enclose x are made ( outw>d-dipp+ %eets ( lava4 ,draw a diagram re/or+ ! volcano ( :i* !y are ! remnant4 ,no volcanic fragm5ts ( ! same nature z ! mat]ials ( :i* ! volcano is built are f\nd ab\t ! region4 ,:at !ory ( ! de/ruction ( ! cone does ?is fact favor8 ,w1 ,wiz>d ,isl&1 is a c9d] cone4 ,:5 0 x built8 ,geys]s & hot spr+s4 ,! hot spr+s ( volcanic regions are among ! la/ ve/iges ( volcanic heat4 ,p]iodically eruptive boil+ spr+s are t]m$ geys]s4 ,9 ea* ( ! geys] regions ( ! e>?--! ,yell[/one ,national ,p>k1 ,icel&1 & ,new ,zeal&--! gr\nd wat] ( ! locality is suppos$ to be heat$ by anci5t lavas t1 because ( ! poor conductivity ( ! rock1 /ill rema9 hot b5ea? ! surface4 ,illu/ration3 ,fig4 #bcc4 ,old ,fai?ful ,geys] 9 ,eruption1 ,yell[/one ,national ,p>k ,old ,fai?ful1 "o ( ! _m geys]s ( ! ,yell[/one ,national ,p>k1 plays a f\nta9 ( boil+ wat] a hundr$ feet 9 air2 :ile cl\ds ( vapor f ! escap+ /eam asc5d to sev]al times t height4 ,! eruptions take place at int]vals ( f sev5ty to n9ety m9utes4 ,9 repose ! geys] is a quiet pool1 occupy+ a crat]like depression 9 a conical m\nd "s twelve feet high4 ,! conduit ( ! spr+ is too irregul> to be s\nd$4 ,! m\nd is compos$ ( por\s silica deposit$ by ! wat]s ( ! geys]4 ,geys]s erupt at int]vals in/ead ( cont9u\sly boil+1 because _! long1 n>r[1 & (t5 tortu\s conduits d n p]mit a free circulation ( ! wat]4 ,aft] an eruption ! tube is refill$ & ! wat] aga9 gradually becomes heat$4 ,deep 9 ! tube :]e x is 9 contact ) hot lavas ! wat] soon] or lat] rea*es ! boil+ po9t1 & bur/+ into /eam %oots ! wat] above x high 9 air4 ,illu/ration3 ,fig4 #bcd4 ,t]race & ,cones ( ,silice\s ,s9t] deposit$ by ,geys]s1 ,yell[/one ,national ,p>k ,c>bonat$ spr+s4 ,aft] all ! o!r signs ( life h gone1 ! anci5t volcano may emit c>bon dioxide z its dy+ brea?4 ,! spr+s ( ! region may long be *>g$ ) c>bon dioxide1 or c>bonat$1 & :]e !y rise ?r\gh lime/one may be expect$ to deposit l>ge quantities ( trav]t9e4 ,we %\ld rememb]1 h[ev]1 t _m c>bonat$ spr+s1 & _m hot spr+s1 are :olly indep5d5t ( volcanoes4 ,illu/ration3 ,fig4 #bce4 ,m\nt ,%a/a1 ,cali=nia ,illu/ration3 ,fig4 #bcf4 ,m\nt ,hood1 ,oregon ,! de/ruction ( ! cone4 ,z soon z ! volcanic cone ceases to gr[ by eruptions ! ag5ts ( erosion beg9 to we> x d[n1 & ! l5g? ( "t t has elaps$ s9ce ! p]iod ( active gr[? may be r\ghly measur$ by ! degree to :i* ! cone has be5 dissect$4 ,we inf] t ,m\nt ,%a/a1 ^: conical %ape is /ill pres]v$ despite ! gullies "o ?\s& feet deep :i* tr5* its sides 7,fig4 #bce71 is y\ng] ?an ,m\nt ,hood1 :i* erosive ag5cies h c>v$ to a pyramidal =m 7,fig4 #bcf74 ,! pile ( mat]ials accumulat$ ab\t a volcanic v5t1 no matt] h[ va/ 9 bulk1 is at la/ swept entirely away4 ,! cone ( ! volcano1 active or ext9ct1 is n old z ! e>? c\nts "t2 volcanoes are %ort-liv$ geological ph5om5a4 ,illu/ration3 ,fig4 #bcg4 ,cr&all ,volcano ,cr&all volcano4 ,?is "n is giv5 to a dissect$ anci5t volcano 9 ! ,yell[/one ,national ,p>k1 :i* once1 x is e/imat$1 re>$ its head ?\s&s ( feet above ! surr\nd+ c\ntry & greatly exce$$ 9 bulk ei!r ,m\nt ,%a/a or ,m\nt ,etna4 ,n a l9e ( ! orig9al m\nta9 rema9s2 all has be5 swept away by erosion except "s f\r ?\s& feet ( ! base ( ! pile4 ,?is basal wreck n[ appe>s z a rugg$ region ab\t ?irty miles 9 diamet]1 tr5*$ by deep valleys & cut into %>p peaks & precipit\s ridges4 ,9 ! c5t] ( ! area is f\nd ! nucleus 7,n1 ,fig4 #bcg71--;a mass ( co>sely cry/all9e rock t congeal$ deep 9 ! old volcanic pipe4 ,f x !re radiate 9 all directions1 l ! spokes ( a :eel1 long dikes ^: rock gr[s rapidly f9] ( gra9 z x leaves ! vic9ity ( ! once heat$ core4 ,! rema9d] ( ! base ( ! anci5t m\nta9 is made ( rudely b$d$ tuffs & volcanic breccia1 ) occasional fl[s ( lava1 "s ( ! fragm5ts ( ! breccia measur+ z mu* z tw5ty feet 9 diamet]4 ,on ! sides ( canyons ! breccia is c>v$ by ra9 erosion to fanta/ic p9nacles4 ,at diff]5t levels 9 ! mid/ ( ^! b$s ( tuff & lava are _m old =e/ gr\nds4 ,! /umps & trunks ( ! trees1 n[ turn$ to /one1 /ill 9 _m cases /& upright :]e once !y grew on ! slopes ( ! m\nta9 z x 0 build+ 7,fig4 #bch74 ,! great size & age ( "s ( ^! trees indicate1 ! lapse ( "t betwe5 ! eruption ^: lavas or tuffs wea!r$ to ! soil on :i* !y grew & ! subsequ5t eruption :i* buri$ !m b5ea? %[]s ( /ones & a%es4 ,ne> ! edge ( ! area lies ,dea? ,gul*1 9 :i* c>bon dioxide is giv5 (f 9 su* quantities t 9 quiet wea!r x accumulates 9 a heavy lay] along ! gr\nd & suffocates ! animals :i* may ent] x4 ,illu/ration3 ,fig4 #bch4 ,fossil ,tree ,trunks1 ,yell[/one ,national ,p>k ,,*apt] ,,xii ,,und]gr\nd ,,/ructures ,,( ,,igne\s ,,orig9 ,x is because long-cont9u$ erosion lays b>e ! inn]mo/ anatomy ( an ext9ct volcano1 & ev5 sweeps away ! entire pile ) mu* ( ! und]ly+ /rata1 ?us leav+ ! v roots ( ! volcano op5 to view1 t we are able to /udy und]gr\nd volcanic /ructures4 ,) ^! we include1 = conv5i5ce1 intrusions ( molt5 rock :i* h be5 driv5 upw>d into ! cru/1 b :i* may n h succe$$ 9 break+ way to ! surface & e/abli%+ a volcano4 ,all ^! /ructures are built ( rock =c$ :5 9 a fluid or pa/y /ate into "s cavity :i* x has f\nd or made1 & we may classify !m !re=e1 accord+ to ! %ape ( ! molds 9 :i* ! molt5 rock has congeal$1 z 7#a7 dikes1 7#b7 volcanic necks1 7#c7 intrusive %eets1 & 7#d7 intrusive masses4 ,dikes4 ,! %eet ( once molt5 rock ) :i* a fissure has be5 fill$ is kn[n z a dike4 ,dikes are =m$ :5 volcanic cones are r5t by explosions or by ! weight ( ! lava column 9 ! duct1 & on ! dissection ( ! pile !y appe> z radiat+ v]tical ribs cutt+ across ! lay]s ( lava & tuff ( :i* ! cone is built4 ,9 regions und]go+ de=mation rocks ly+ deep bel[ ! gr\nd are (t5 brok5 & ! fissures are fill$ ) molt5 rock f b5ea?1 :i* f9ds no outlet to ! surface4 ,su* dikes are common 9 areas ( ! mo/ anci5t rocks1 :i* h be5 br\ght to light by long erosion4 ,9 exceptional cases dikes may rea* ! l5g? ( fifty or "o hundr$ miles4 ,!y v>y 9 wid? f a fraction ( a foot to ev5 z mu* z ?ree hundr$ feet4 ,illu/ration3 ,fig4 #bci4 ,dikes1 ,spani% ,peaks1 ,colorado ,dikes are commonly m f9e ( gra9 on ! sides ?an 9 ! c5t]1 & may h a glassy & crackl$ surface :]e !y meet ! inclos+ rock4 ,c y acc\nt = ?is on any pr9ciple :i* y h le>n$8 ,illu/ration3 ,fig4 #bdj4 ,a ,dissect$ ,volcanic ,cone ,n1 volcanic neck2 l1 l1 lava-topp$ table m\nta9s2 t1 t1 b$s ( tuff2 d1 d1 dikes2 dott$ l9es indicate ! initial pr(ile ,volcanic necks4 ,! pipe ( a volcano rises f f> bel[ ! base ( ! cone1--f ! deep res]voir f :i* its eruptions are suppli$4 ,:5 ! volcano has become ext9ct ?is great tube rema9s fill$ ) h>d5$ lava4 ,x =ms a cyl9drical core ( solid rock1 except = "s di/ance bel[ ! anci5t crat]1 :]e x may conta9 a mass ( fragm5ts :i* _h fall5 back into ! *imney aft] be+ hurl$ into ! air4 ,illu/ration3 ,fig4 #bda4 ,m\nt ,johnson1 a ,volcanic ,neck ne> ,montreal ,z ! m\nta9 is worn d[n1 ?is c5tral column kn[n z ! volcanic neck is left /&+ z a conical hill 7,fig4 #bdj74 ,ev5 :5 e o!r trace ( ! volcano has be5 swept away1 erosion w n h pass$ bel[ ?is great /alk on :i* ! volcano 0 borne z a fi]y fl[] ^: site x rema9s to m>k4 ,9 volcanic regions ( deep d5udation volcanic necks rise solit>y & abrupt f ! surr\nd+ c\ntry z dome-%ap$ hills4 ,!y are m>k$ features 9 ! l&scape 9 p>ts ( ,scotl& & 9 ! ,/4 ,lawr5ce valley ab\t ,montreal 7,fig4 #bda74 ,illu/ration3 ,fig4 #bdb4 ,! ,palisades ( ! ,hudson1 ,new ,j]sey ,intrusive %eets4 ,%eets ( igne\s rocks are sometimes f\nd int]leav$ ) s$im5t>y /rata1 especially 9 regions :]e ! rocks h be5 de=m$ & h suff]$ f volcanic action4 ,9 "s in/ances su* a %eet is se5 to be contemporane\s 7p4 #bdh74 ,9 o!r in/ances ! %eet mu/ be intrusive4 ,! ov]ly+ /ratum1 z well z t b5ea?1 has be5 affect$ by ! heat ( ! once molt5 rock4 ,we inf] t ! igne\s rock :5 9 a molt5 /ate 0 =c$ betwe5 ! /rata1 mu* z a c>d may be pu%$ betwe5 ! leaves ( a clos$ book4 ,! liquid w$g$ its way betwe5 ! lay]s1 lift+ ^? above to make room = itself4 ,! s\rce ( ! intrusive %eet may (t5 be trac$ to "s dike 7kn[n !re=e z ! fe$+ dike71 or to "s mass ( igne\s rock4 ,intrusive %eets may ext5d a score & m ( miles1 &1 l ! longe/ surface fl[s1 ! mo/ ext5sive %eets consi/ ( ! m fusible & fluid lavas1--^? ( ! basic class ( :i* basalt is an example4 ,intrusive %eets are usually h>d] ?an ! /rata 9 :i* !y lie & are !re=e (t5 left 9 relief aft] long d5udation ( ! region 7,fig4 #cae74 ,illu/ration3 ,fig4 #bdc4 ,diagram ( ! ,palisades ( ! ,hudson i1 intrusive %eet2 s1 s&/one2 d1 fe$+ dike2 ,,hr1 ,hudson ,riv] ,on ! we/ bank ( ! ,hudson !re ext5ds f ,new ,york ,bay nor? = ?irty miles a bold cliff sev]al hundr$ feet high1--! ,palisades ( ! ,hudson4 ,x is ! outcropp+ edge ( a %eet ( anci5t igne\s rock1 :i* re/s on /ratifi$ s&/ones & is ov]la9 by /rata ( ! same s]ies4 ,s&/ones & lava %eet toge!r dip g5tly to ! we/ & ! latt] disappe>s f view two miles back f ! riv]4 ,x is an int]e/+ "q :e!r ! ,palisades %eet is contemporane\s or intrusive4 ,0 x outp\r$ on ! s&/ones b5ea? x :5 !y =m$ ! floor ( ! sea1 & cov]$ =?) by ! s$im5ts ( ! /rata above1 or 0 x intrud$ among ^! b$s at a lat] date8 ,illu/ration3 ,fig4 #bdd4 ,section ( ,electric ,peak4 ,e4 & ,gray ,peak1 ,g1 ,yell[/one ,national ,p>k ,intrusive %eets & masses ( igne\s rock are drawn 9 black ,! latt] is ! case3 = ! ov]ly+ /ratum is int5sely bak$ along ! zone ( contact4 ,at ! we/ edge ( ! %eet is f\nd ! dike 9 :i* ! lava rose to =ce its way f> & wide betwe5 ! /rata4 ,electric ,peak1 "o ( ! prom95t m\nta9s ( ! ,yell[/one ,national ,p>k1 is c>v$ out ( a mass ( /rata into :i* _m %eets ( molt5 rock h be5 intrud$4 ,! we/]n summit consi/s ( su* a %eet sev]al hundr$ feet ?ick4 ,/udy+ ! section ( ,figure #bdd1 :at inf]5ce d y draw z to ! s\rce ( ^! intrusive %eets8 ,illu/ration3 ,fig4 #bde4 ,/one ,m\nta91 ,georgia1 a ,granite ,boss ,intrusive ,masses ,bosses4 ,?is "n is g5]ally appli$ to huge irregul> masses ( co>sely cry/all9e igne\s rock ly+ 9 ! mid/ ( o!r =mations4 ,bosses v>y greatly 9 size & may rea* scores ( miles 9 ext5t4 ,seldom are !re any evid5ces f\nd t bosses ev] _h connection ) ! surface4 ,on ! o!r h&1 x is (t5 prov$ t !y h be5 driv51 or h melt$ _! way1 upw>d into ! =mations 9 :i* !y lie2 = !y give (f dikes & intrusive %eets1 & h pr(\ndly alt]$ ! rocks ab\t !m by _! heat4 ,illu/ration3 ,fig4 #bdf4 ,map ( ,granite ,bosses ne> ,baltimore 7areas horizontally ,l9$7 ,! texture ( ! rock ( bosses proves t consolidation proce$$ sl[ly & at great dep?s1 & x is only because ( va/ d5udation t !y are n[ expos$ to view4 ,bosses are commonly h>d] ?an ! rocks ab\t !m1 & /& up1 !re=e1 z r\nd$ hills & m\nta9\s ridges long aft] ! surr\nd+ c\ntry has worn to a l[ pla9 7,fig4 #bde74 ,figure #bdf exhibits a few small bosses ( granite ne> ,baltimore z examples ( num]\s areas ( igne\s rock )9 ! ,pi$mont ,belt :i* repres5t bodies ( molt5 rock :i* solidifi$ deep bel[ ! surface4 ,! ,spani% ,peaks ( s\!a/]n ,colorado 7 =m$ by ! up?ru/ ( imm5se masses ( igne\s rock1 bulg+ & break+ ! ov]ly+ /rata4 ,on "o side ( ! m\nta9s ! ?r[ ( ! fault is ne>ly a mile1 & fragm5ts ( deep-ly+ b$s 7 dragg$ upw>d by ! ris+ masses4 ,! adjac5t rocks 7 alt]$ by heat to a di/ance ( sev]al ?\s& feet4 ,no evid5ce appe>s t ! molt5 rock ev] rea*$ ! surface1 & if volcanic eruptions ev] took place ei!r 9 lava fl[s or fragm5tal mat]ials1 all traces ( !m h be5 effac$4 ,! rock ( ! intrusive masses is co>sely cry/all9e1 & no d\bt solidifi$ sl[ly "u ! pressure ( va/ ?icknesses ( ov]ly+ rock1 n[ mo/ly remov$ by erosion4 ,a magnific5t sy/em ( dikes radiates f ! ,peaks to a di/ance ( fifte5 miles1 "s n[ be+ left by long erosion z walls a hundr$ feet 9 height 7,fig4 #bci74 ,intrusive %eets f$ by ! dikes p5etrate ! surr\nd+ /rata1 & _! edges are cut by canyons z mu* z tw5ty-five miles f ! m\nta94 ,9 ^! /rata are valuable b$s ( lignite1 an imp]fect coal1 :i* ! heat ( dikes & %eets has *ang$ to coke4 ,illu/ration3 ,fig4 #bdg4 ,section ( a ,laccoli? ,laccoli?s4 ,! laccoli? 7,greek laccos1 ci/]n2 li?os1 /one7 is a v>iety ( intrusive masses 9 :i* molt5 rock has spread betwe5 ! /rata1 &1 lift+ ! /rata above x to a dome-%ap$ =m1 has collect$ b5ea? !m 9 a l5s-%ap$ body ) a flat base4 ,! ,h5ry ,m\nta9s1 a small gr\p ( deta*$ peaks 9 s\!rn ,utah1 rise f a plateau ( horizontal rocks4 ,"s ( ! peaks are c>v$ :olly 9 sep>ate domelike uplifts ( ! /rata ( ! plateau4 ,9 o!rs1 z ,m\nt ,hill]s1 ! l>ge/ ( ! gr\p1 !re is expos$ on ! summit a core ( igne\s rock f :i* ! s$im5t>y rocks ( ! flanks dip /eeply outw>d 9 all directions4 ,9 /ill o!rs erosion has /ripp$ (f ! cov]+ /rata & has laid b>e ! core to its base2 & its %ape is "h se5 to be t ( a plano-convex l5s or a bak]'s bun1 its flat base re/+ on ! undi/urb$ b$d$ rocks b5ea?4 ,! /ructure ( ,m\nt ,hill]s is %[n 9 ,figure #bdh4 ,! nucleus ( igne\s rock is f\r miles 9 diamet] & m ?an a mile 9 dep?4 ,illu/ration3 ,fig4 #bdh4 ,section ( ,m\nt ,hill]s ,regional intrusions4 ,^! va/ bodies ( igne\s rock1 :i* may rea* hundr$s ( miles 9 diamet]1 diff] little f bosses except 9 _! imm5se bulk4 ,l bosses1 regional intrusions give (f dikes & %eets & greatly *ange ! rocks ab\t !m by _! heat4 ,!y are n[ expos$ to view only because ( ! pr(\nd d5udation :i* has remov$ ! upheav$ dome ( rocks b5ea? :i* !y sl[ly cool$4 ,su* intrusions are accompani$--:e!r z cause or z effect is /ill h>dly kn[n--by de=mations1 & _! masses ( igne\s rock are ?us f\nd z ! core ( _m great m\nta9 ranges4 ,! granitic masses ( :i* ! ,bitt] ,root ,m\nta9s & ! ,si]ra ,nevadas h be5 l>gely c>v$ are ea* m ?an ?ree hundr$ miles 9 l5g?4 ,imm5se regional intrusions1 ! cores ( once l(ty m\nta9 ranges1 are f\nd ^u ! ,laur5tian p5epla94 ,physiographic effects ( intrusive masses4 ,we h already se5 examples ( ! topographic effects ( intrusive masses 9 ,m\nt ,hill]s1 ! ,spani% ,peaks1 & 9 ! great m\nta9 ranges m5tion$ 9 ! p>agraph on regional intrusions1 al?\gh 9 ! latt] in/ances ^! effects are entangl$ ) ! effects ( o!r processes4 ,masses ( igne\s rock _c be intrud$ )9 ! cru/ )\t an accompany+ de=mation on a scale correspond+ to ! bulk ( ! intrud$ mass4 ,! ov]ly+ /rata are ar*$ into hills or m\nta9s1 or1 if ! molt5 mat]ial is ( great ext5t1 ! /rata may conceivably be float$ upw>d to ! height ( a plateau4 ,we may suppose t ! transf]5ce ( molt5 matt] f "o region to ano!r may be among ! causes ( sl[ subsid5ces & elevations4 ,intrusions give rise to fissures1 dikes1 & intrusive %eets1 & ^! dislocations _c fail to produce e>?quakes4 ,:]e intrusive masses op5 communication ) ! surface1 volcanoes are e/abli%$ or fissure eruptions occur su* z ^? ( ,icel&4 ,! ,intrusive ,rocks ,! igne\s rocks are divid$ into two g5]al classes1--! volcanic or eruptive rocks1 :i* h be5 outp\r$ 9 op5 air or on ! floor ( ! sea1 & ! intrusive rocks1 :i* h be5 intrud$ )9 ! rocks ( ! cru/ & h solidifi$ bel[ ! surface4 ,! two classes are alike 9 *emical composition & may be divid$ into acidic & basic gr\ps4 ,9 texture ! intrusive rocks diff] f ! volcanic rocks because ( ! diff]5t conditions "u :i* !y h solidifi$4 ,!y cool$ f> m sl[ly b5ea? ! cov] ( ! rocks into :i* !y 7 press$ ?an is p]mitt$ to lava fl[s 9 op5 air4 ,_! con/itu5t m9]als _h ample opportunity to sort !mselves & cry/allize f ! fluid mixture1 & none ( t mixture 0 left to congeal z a glassy pa/e4 ,!y consolidat$ also "u pressure4 ,!y are nev] scoriace\s1 = ! /eam ) :i* !y 7 *>g$ 0 n all[$ to exp& & di/5d !m ) /eam blebs4 ,9 ! rocks ( ! l>g] intrusive masses "o may see ) a p[]ful microscope exce$+ly m9ute cavities1 to be c\nt$ by _m millions to ! cubic in*1 9 :i* ! gase\s wat] :i* ! mass conta9$ 0 held imprison$ "u ! imm5se pressure ( ! ov]ly+ rocks4 ,naturally ^! *>act]i/ics are be/ develop$ 9 ! intrusives :i* cool$ mo/ sl[ly1 i4e4 9 ! deepe/-seat$ & l>ge/ masses2 :ile 9 ^? :i* cool$ m rapidly1 z 9 dikes & %eets1 we f9d gradations approa*+ ! texture ( surface fl[s4 ,v>ieties ( ! intrusive rocks4 ,we w n[ describe a few ( ! v>ieties ( rocks ( deep-seat$ intrusions4 ,all are ev5 gra9$1 consi/+ ( a mass ( cry/all9e gra9s =m$ dur+ "o cont9u\s /age ( solidification1 & no porphyritic cry/als appe> z 9 lavas4 ,granite1 z we h le>n$ already1 is compos$ ( ?ree m9]als1--qu>tz1 feldsp>1 & mica4 ,accord+ to ! color ( ! feldsp> ! rock may be r$1 or p9k1 or gray4 ,hornbl5de--a black or d>k gre5 m9]al1 an iron-magnesian silicate1 ab\t z h>d z feldsp>--is sometimes f\nd z a f\r? con/itu5t1 & ! rock is !n kn[n z hornbl5dic granite4 ,granite is an acidic rock correspond+ to rhyolite 9 *emical composition4 ,we may believe t ! same molt5 mass :i* supplies ?is acidic lava 9 surface fl[s solidifies z granite deep bel[ gr\nd 9 ! volcanic res]voir4 ,sy5ite1 compos$ ( feldsp> & mica1 has consolidat$ f a less silice\s mixture ?an has granite4 ,diorite1 /ill less silice\s1 is compos$ ( hornbl5de & feldsp>1--! latt] m9]al be+ ( diff]5t v>iety f ! feldsp> ( granite & sy5ite4 ,gabbro1 a typical basic rock1 corresponds to basalt 9 *emical composition4 ,x is a d>k1 heavy1 co>sely cry/all9e aggregate ( feldsp> & augite 7a d>k m9]al alli$ to hornbl5de74 ,x (t5 conta9s magnetite 7! magnetic black oxide ( iron7 & oliv9e 7a gre5i% magnesian silicate74 ,9 ! nor!rn /ates all ^! types1 & _m o!rs also ( ! va/ numb] ( v>ieties ( intrusive rocks1 c be f\nd among ! rocks ( ! drift br\ght f ! areas ( igne\s rock 9 ,canada & ! /ates ( our nor!rn bord]4 ,illu/ration3 ,fig4 #bdi4 ,gr\nd ,plan ( ,dikes 9 ,granite4 7,scale #hj feet to ! in*7 ,:at is ! relative age ( ! dikes aa1 bb1 & cc8 ,illu/ration3 ,fig4 #bej4 ,a & ,b4 ,m\nta9s ( co>sely ,cry/all9e ,igne\s i1 surr\nd$ by ,s$im5t>y ,/rata s & s ,copy ea* diagram & complete x1 s z to %[ :e!r ! mass ( igne\s rock is a volcanic neck1 a boss1 or a laccoli? ,summ>y4 ,! records ( geology prove t s9ce ! e>lie/ ( _! annals trem5d\s =ces h be5 active 9 ! e>?4 ,9 all ! pa/1 "u pressures inconceivably great1 molt5 rock has be5 driv5 upw>d into ! rocks ( ! cru/4 ,x has squeez$ into fissures =m+ dikes2 x has burr[$ among ! /rata z intrusive %eets2 x has melt$ ! rocks away or lift$ ! ov]ly+ /rata1 fill+ ! *amb]s :i* x has made ) intrusive masses4 ,dur+ all geological ages molt5 rock has f\nd way to ! surface1 & volcanoes h d>k5$ ! sky ) cl\ds ( a%es & p\r$ /reams ( gl[+ lava d[n _! sides4 ,! old] /rata1--! /rata :i* h be5 mo/ deeply buri$1--& especially ^? :i* h suff]$ mo/ f fold+ & f fracture1 %[ ! l>ge/ am\nt ( igne\s intrusions4 ,! molt5 rock :i* has be5 driv5 f ! e>?'s int]ior to )9 ! cru/ or to ! surface dur+ geologic "t mu/ be reckon$ 9 millions ( cubic miles4 ,illu/ration3 ,fig4 #bea4 #a1 lime/one2 #b1 tuff2 #c1 #e1 #g1 %ale ) m>9e %ells2 #d1 #f1 lava1 dott$ portions scoriace\s4 ,give ! hi/ory record$ 9 ?is section ,illu/ration3 ,fig4 #beb4 a1 s$im5t>y /rata ) intrusive %eets2 b1 s$im5t>y /rata2 c1 lava fl[2 d1 dike4 ,give ! succession ( ev5ts record$ 9 ?is section ,illu/ration3 ,fig4 #bec4 ,:i* ( ! lava %eets ( ?is section are contemporane\s anti :i* intrusive1--,a1 ^: upp] surface is ov]la9 ) a conglom]ate ( roll$ lava pebbles2 ,b1 ! cracks & seams ( ^: upp] surface are fill$ ) ! mat]ial ( ! ov]ly+ s&/one2 ,c1 :i* breaks across ! /rata 9 :i* x is imb$d$2 ,d1 :i* includes fragm5ts ( bo? ! und]ly+ & ov]ly+ /rata & p5etrates _! crevices & seams8 ,illu/ration3 ,fig4 #bed4 ,mato ,tepee1 ,wyom+ ,?is magnific5t t[] ( igne\s rock ?ree hundr$ feet 9 height has be5 call$ by "s a volcanic neck4 ,is ! direction ( ! columns t :i* w\ld obta9 9 ! cyl9drical pipe ( a volcano8 ,! t[] is probably ! remnant ( a small laccoli?1 an outly+ memb] ( a gr\p ( laccoli?s situat$ n f> di/ant ,! ,int]ior ,condition ( ! ,e>? & ,causes ( ,vulcanism & ,de=mation ,! problems ( volcanoes & ( de=mation are s closely connect$ ) t ( ! e>?'s int]ior t we may consid] !m toge!r4 ,few ( ^! problems are solv$1 & we may only /ate "s kn[n facts & ! probable conclusions :i* may be drawn z inf]5ces f !m4 ,! int]ior ( ! e>? is hot4 ,volcanoes prove t 9 _m p>ts ( ! e>? !re exi/ )9 rea* ( ! surface regions ( su* int5se heat t ! rock is 9 a molt5 condition4 ,deep wells & m9es %[ ev]y:]e an increase 9 temp]ature bel[ ! surface %ell affect$ by ! heat ( summ] & ! cold ( w9t]1--a %ell 9 temp]ate latitudes sixty or sev5ty feet ?ick4 ,?us 9 a bor+ m ?an a mile deep at ,s*ladeba*1 ,g]many1 ! e>? gr[s w>m] at ! rate ( #a ,f4 = e sixty-sev5 feet z we desc5d4 ,tak+ ! av]age rate ( increase at "o degree = e sixty feet ( desc5t1 & assum+ t ?is rate1 obs]v$ at ! mod]ate di/ances op5 to obs]vation1 cont9ues to at lea/ ?irty-five miles1 ! temp]ature at t dep? mu/ be m ?an ?ree ?\s& degrees1--a temp]ature at :i* all ord9>y rocks w\ld melt at ! e>?'s surface4 ,! rate ( increase 9 temp]ature probably less5s z we g d[nw>d1 & x may n be appreciable bel[ a few hundr$ miles4 ,b !re is no reason to d\bt t ! int]ior ( ! e>? is int5sely hot4 ,bel[ a dep? ( "o or two score miles we may imag9e ! rocks ev]y:]e gl[+ ) heat4 ,al?\gh ! heat ( ! int]ior is great en\gh to melt all rocks at atmosph]ic pressure1 x does n foll[ t ! int]ior is fluid4 ,pressure raises ! fus+ po9t ( rocks1 & ! weight ( ! cru/ may keep ! int]ior 9 :at may be call$ a solid /ate1 al?\gh s hot z to be a liquid or a gas 7 ! pressure to be remov$4 ,! int]ior ( ! e>? is d5se & heavy4 ,! e>? behaves z a globe m rigid ?an glass "u ! /ra9s to :i* x is subject$ by ! attractions ( ! sun & moon & o!r heav5ly bodies4 ,! j> ( _w-%ak+ e>?quakes passes ?r\gh ! e>?'s int]ior ) ne>ly twice ! velocity ) :i* x w\ld trav]se solid /eel1 & s9ce ! spe$ ( ela/ic waves dep5ds on ! d5sity & ela/icity ( ! m$ium1 x foll[s t ! globe is z a :ole m d5se & rigid ?an /eel4 ,! int]ior ( ! e>? is extremely d5se & rigid4 ,! common rocks ( ! cru/ are ab\t two & a half times heavi] ?an wat]1 :ile ! e>? z a :ole weighs five & six-t5?s times z mu* z a globe ( wat] ( ! same size4 ,! int]ior is !re=e mu* m heavy ?an ! cru/4 ,?is may be caus$ 9 "p by compression ( ! int]ior "u ! enorm\s weight ( ! cru/1 & 9 "p also by an assortm5t ( mat]ial1 ! heavi] sub/ances1 su* z ! heavy metals1 hav+ gravitat$ t[>ds ! c5t]4 ,betwe5 ! cru/1 :i* is solid because x is cool1 & ! int]ior1 :i* is hot en\gh to melt 7 x n = ! pressure :i* keeps x d5se & rigid1 !re may be an int]m$iate zone 9 :i* heat & pressure are s ev5ly balanc$ t "h rock liquefies :5ev] & :]ev] ! pressure ^u x may be reliev$ by movem5ts ( ! cru/4 ,x is p]haps f su* a subcru/al lay] t ! lava ( volcanoes is suppli$4 ,! causes ( volcanic action4 ,x is n[ g5]ally believ$ t ! heat ( volcanoes is t ( ! e>?'s int]ior4 ,o!r causes1 su* z friction & cru%+ 9 ! mak+ ( m\nta9s & ! *emical reactions betwe5 oxidiz+ ag5ts ( ! cru/ & ! unoxidiz$ int]ior1 h be5 sugge/$1 b to mo/ geologi/s !y seem inadequate4 ,!re is mu* diff]5ce ( op9ion z to ! =ce :i* causes molt5 rock to rise to ! surface 9 ! ducts ( volcanoes4 ,/eam is s evid5tly conc]n$ 9 explosive eruptions t _m believe t lava is driv5 upw>d by ! expansive =ce ( ! /eam ) :i* x is *>g$1 mu* z a viscid liquid rises & boils ov] 9 a te/ tube or kettle4 ,b 9 quiet eruptions1 & /ill m 9 ! irruption ( intrusive %eets & masses1 !re is little if any evid5ce t /eam is ! driv+ =ce4 ,x is !re=e believ$ by _m geologi/s t x is pressure due to cru/al movem5ts & int]nal /resses :i* squeezes molt5 rock f bel[ into fissures & ducts 9 ! cru/4 ,x is held by "s t :]e consid]able wat] is suppli$ to ! ris+ column ( lava1 z f ! gr\nd wat] ( ! surr\nd+ region1 & :]e ! lava is viscid s t /eam does n readily escape1 ! eruption is ( ! explosive type2 :5 ^! conditions d n obta91 ! lava outwells quietly1 z 9 ! ,hawaiian volcanoes4 ,x is held by o!rs n only t volcanoes are due to ! outfl[ ( ! e>?'s deep-seat$ heat1 b also t ! /eam & o!r emitt$ gases are = ! mo/ "p native to ! e>?'s int]ior & nev] h _h place 9 ! circulation ( atmosph]ic & gr\nd wat]s4 ,volcanic action & de=mation4 ,volcanoes d n occur on wide pla9s or among anci5t m\nta9s4 ,on ! o!r h&1 :]e movem5ts ( ! e>?'s cru/ are 9 progress 9 ! uplift ( high plateaus1 & /ill m 9 m\nta9 mak+1 molt5 rock may rea* ! surface1 or may be driv5 upw>d t[>d x =m+ great intrusive masses4 ,?us ext5sive lava fl[s accompani$ ! upheaval ( ! block m\nta9s ( we/]n ,nor? ,am]ica & ! uplift ( ! ,colorado plateau4 ,a l9e ( rec5t volcanoes may be trac$ along ! sy/em ( rift valleys :i* ext5ds f ! ,jordan & ,dead ,sea ?r\gh ea/]n ,africa to ,lake ,nyassa4 ,! volcanoes ( ! ,&es %[ h[ conspicu\s volcanic action may be 9 "y ris+ ranges4 ,fold$ m\nta9s (t5 %[ a core ( igne\s rock1 :i* by long erosion has come to =m ! axis & ! highe/ peaks ( ! range1 z if ! molt5 rock _h be5 squeez$ up "u ! ris+ upfolds4 ,z we deciph] ! records ( ! rocks 9 hi/orical geology we %all see m fully h[1 9 all ! pa/1 volcanic action has *>act]iz$ ! p]iods ( great cru/al movem5ts1 & h[ x has be5 abs5t :5 & :]e ! e>?'s cru/ has rema9$ comp>atively at re/4 ,! causes ( de=mation4 ,z ! e>?'s int]ior1 or nucleus1 is highly heat$ x mu/ be con/antly ?\gh sl[ly los+ its heat by conduction ?r\gh ! cru/ & into space2 & s9ce ! nucleus is cool+ x mu/ also be contract+4 ,! nucleus has contract$ also because ( ! extrusion ( molt5 matt]1 ! loss ( con/itu5t gases giv5 (f 9 volcanic eruptions1 & 7/ill m important7 ! compression & consolidation ( its mat]ial "u gravity4 ,z ! nucleus contracts1 x t5ds to draw away f ! cool$ & solid cru/1 & ! latt] settles1 adapt+ itself to ! %r9k+ nucleus mu* z ! sk9 ( a )]+ apple wr9kles d[n ^u ! %runk5 fruit4 ,! unsupport$ weight ( ! sph]ical cru/ develops enorm\s tang5tial pressures1 simil> to ! /resses ( an ar* or dome1 & :5 ^! lat]al ?ru/s accumulate beyond ! p[] ( resi/ance ! solid rock is w>p$ & fold$ & brok54 ,s9ce ! planet atta9$ its pres5t mass x has ?us be5 less5+ 9 volume4 ,not)/&+ local & relative upheavals ! e>?'s surface on ! :ole has drawn ne>] & ne>] to ! c5t]4 ,! portions ( ! li?osph]e :i* h be5 c>ri$ d[n ! f>!/ h receiv$ ! wat]s ( ! oceans1 :ile ^? portions :i* h be5 c>ri$ d[n ! lea/ h em]g$ z cont95ts4 ,al?\gh x s]ves our conv5i5ce to ref] ! movem5ts ( ! cru/ to ! sea level z datum plane1 x is und]/ood t ?is level is by no means fix$4 ,*anges 9 ! ocean bas9s increase or r$uce _! capacity & ?us l[] or raise ! level ( ! sea4 ,b s9ce ^! bas9s are connect$1 ! effect ( any *ange ^u ! wat] level is s di/ribut$ t x is f> less noticeable ?an a correspond+ *ange w\ld be ^u ! l&4 ,,*apt] ,,xiii ,,metamorphism ,,& ,,m9]al ,,ve9s ,"u ! action ( int]nal ag5cies rocks ( all k9ds may be r5d]$ h>d]1 m firmly cem5t$1 & m cry/all9e4 ,^! processes are kn[n z metamorphism1 & ! rocks affect$1 :e!r orig9ally s$im5t>y or igne\s1 are call$ metamorphic rocks4 ,we may contra/ ) metamorphism ! action ( ext]nal ag5cies 9 wea!r+1 :i* r5d] rocks less coh]5t by dissolv+ _! soluble p>ts & break+ d[n _! cry/all9e gra9s4 ,contact metamorphism4 ,rocks b5ea? a lava fl[ or 9 contact ) igne\s intrusions are f\nd to be metamorphos$ to v>i\s degrees by ! heat ( ! cool+ mass4 ,! adjac5t /rata may be *ang$ only 9 color1 h>dness1 & texture4 ,?us1 next to a dike1 bitum9\s coal may be bak$ to coke or an?racite1 & *alk & lime/one to cry/all9e m>ble4 ,s&/one may be conv]t$ into qu>tzite1 & %ale into argillite1 a compact1 massive clay rock4 ,new m9]als may also be develop$4 ,9 s$im5t>y rocks !re may be produc$ cry/als ( mica & ( g>net 7a m9]al z h>d z qu>tz1 commonly occurr+ 9 r$1 twelve-sid$ cry/als74 ,:]e ! *anges are mo/ pr(\nd1 rocks may be :olly made ov] 9 /ructure & m9]al composition4 ,9 contact metamorphism1 ?9 %eets ( molt5 rock produce less effect ?an ?ick] ones4 ,! /ronge/ heat effects are naturally caus$ by bosses & regional intrusions1 & ! zone ( *ange ab\t !m may be sev]al miles 9 wid?4 ,9 ^! *anges heat$ wat]s & vapors f ! masses ( igne\s rocks und\bt$ly play a v important "p4 ,:i* w be m /rongly alt]$1 ! rocks ab\t a clos$ dike 9 :i* lava began to cool z soon z x fill$ ! fissure1 or ! rocks ab\t a dike :i* op5$ on ! surface & ?r\gh :i* ! molt5 rock fl[$ = "s "t8 ,tak+ into consid]ation ! "p play$ by heat$ wat]s1 :i* w produce ! mo/ f>-rea*+ metamorphism1 dikes :i* cut across ! b$d+ planes or intrusive %eets :i* are ?ru/ betwe5 ! /rata8 ,regional metamorphism4 ,metamorphic rocks occur widespread 9 _m regions1 (t5 hundr$s ( squ>e miles 9 area1 :]e su* ext5sive *anges _c be acc\nt$ = by igne\s intrusions4 ,su* are ! dissect$ cores ( l(ty m\nta9s1 z ! ,alps1 & ! worn-d[n bases ( anci5t ranges1 z 9 ,new ,engl&1 l>ge areas 9 ! ,pi$mont ,belt1 & ! ,laur5tian p5epla94 ,9 ^! regions ! rocks h yield$ to imm5se pressure4 ,!y h be5 fold$1 crumpl$1 & ma%$1 & ev5 _! m9ute gra9s1 z "o may see ) a microscope1 h (t5 be5 puck]$1 brok51 & cru%$ to p[d]4 ,x is to ^! me*anical movem5ts & /ra9s :i* ! rocks h suff]$ 9 e "p t we may attribute _! metamorphism1 & ! degree to :i* !y h be5 *ang$ is 9 direct proportion to ! degree to :i* !y h be5 de=m$ & ma%$4 ,o!r factors1 h[ev]1 h play$ important p>ts4 ,rock cru%+ develops heat1 & all[s a fre] circulation ( heat$ wat]s & vapors4 ,?us *emical reactions are greatly quick5$2 m9]als are dissolv$ & r$eposit$ 9 new positions1 or _! *emical con/itu5ts may recomb9e 9 new m9]als1 entirely *ang+ ! nature ( ! rock1 z :51 = example1 feldsp> recry/allizes z qu>tz & mica4 ,e>ly /ages ( metamorphism are se5 9 slate4 ,pressure has h>d5$ ! m>9e muds1 ! arkose 7p4 #ahf71 or ! volcanic a% f :i* slates are d]iv$1 & has caus$ !m to cleave by ! re>rangem5t ( _! p>ticles4 ,"u some:at great] pressure1 slate becomes phyllite1 a clay slate ^: cleavage surfaces are lu/r\s ) flat-ly+ mica flakes4 ,! same pressure :i* has caus$ ! rock to cleave has set free "s ( its m9]al con/itu5ts along ! cleavage planes to cry/allize !re z mica4 ,illu/ration3 ,fig4 #bee4 ,a ,foliat$ ,rock ,foliation4 ,"u /ill /rong] pressure ! :ole /ructure ( ! rock is alt]$4 ,! m9]als ( :i* x is compos$1 & ! new m9]als :i* develop by heat & pressure1 arrange !mselves along planes ( cleavage or ( %e> 9 rudely p>allel leaves1 or folia4 ,( ?is /ructure1 call$ foliation1 we may di/+ui% two types1--a co>s] feldspa?ic type1 & a f9e type 9 :i* o!r m9]als ?an feldsp> pr$om9ate4 ,gneiss is ! g5]al "n "u :i* are compris$ co>sely foliat$ rocks b&$ ) irregul> lay]s ( feldsp> & o!r m9]als4 ,! gneisses appe> to be due 9 _m cases to ! cru%+ & %e>+ ( deep-seat$ igne\s rocks1 su* z granite & gabbro4 ,! cry/all9e s*i/s1 repres5t+ ! f9] types ( foliation1 consi/ ( ?91 p>allel1 cry/all9e leaves1 :i* are (t5 rem>kably crumpl$4 ,^! folia c be di/+ui%$ f ! lam9ae ( s$im5t>y rocks by _! l5ticul> =m & lack ( cont9uity1 & especially by ! fact t !y consi/ ( platy1 cry/all9e gra9s1 & n ( p>ticles r\nd$ by we>4 ,mica s*i/1 ! mo/ common ( s*i/s1 & 9 fact ( all metamorphic rocks1 is compos$ ( mica & qu>tz 9 alt]nat+ wavy folia4 ,all gradations betwe5 x & phyllite may be trac$1 & 9 _m cases we may prove x due to ! metamorphism ( slates & %ales4 ,x is widespread 9 ,new ,engl& & along ! ea/]n side ( ! ,appala*ians4 ,talc s*i/ consi/s ( qu>tz & talc1 a light-color$ magnesian m9]al ( greasy feel1 & s s(t t x c be scrat*$ ) ! ?umb nail4 ,hornbl5de s*i/1 result+ 9 _m cases f ! foliation ( basic igne\s rocks1 is made ( folia ( hornbl5de alt]nat+ ) b&s ( qu>tz & feldsp>4 ,hornbl5de s*i/ is common ov] l>ge areas 9 ! ,lake ,sup]ior region4 ,qu>tz s*i/ is produc$ f qu>tzite by ! developm5t ( f9e folia ( mica along planes ( %e>4 ,all gradations may be f\nd betwe5 x & unfoliat$ qu>tzite on ! "o h& & mica s*i/ on ! o!r4 ,"u ! resi/less pressure ( cru/al movem5ts almo/ any rocks1 s&/ones1 %ales1 lavas ( all k9ds1 granites1 diorites1 & gabbros may be metamorphos$ into s*i/s by cru%+ & %e>+4 ,lime/ones1 h[ev]1 are metamorphos$ by pressure into m>ble1 ! gra9s ( c>bonate ( lime recry/alliz+ freely to int]lock+ cry/als ( calcite4 ,^! few examples mu/ suffice ( ! great class ( metamorphic rocks4 ,z we h se51 !y owe _! orig9 to ! alt]ation ( bo? ( ! o!r classes ( rocks--! s$im5t>y & ! igne\s--by heat & pressure1 assi/$ usually by ! pres5ce ( wat]4 ,! fact ( *ange is se5 9 _! h>dness arid cem5tation1 _! m or less complete recry/allization1 & _! foliation2 b ! *ange is (t5 s complete t no trace ( _! orig9al /ructure & m9]al composition rema9s to tell :e!r ! rocks f :i* !y 7 d]iv$ 7 s$im5t>y or igne\s1 or to :at v>iety ( ei!r ( ^! classes !y belong$4 ,illu/ration3 ,fig4 #bef4 ,contort$ ,gneiss1 ! ,ottawa ,riv]1 ,canada ,illu/ration3 ,fig4 #beg4 ,qu>tz ,ve9s 9 ,slate ,9 _m cases1 h[ev]1 ! e>ly hi/ory ( a metamorphic rock c be deciph]$4 ,fossils n :olly oblit]at$ may prove x orig9ally wat]-laid4 ,s*i/s may conta9 roll$-out pebbles1 %[+ _! d]ivation f a conglom]ate4 ,dikes ( igne\s rocks may be foll[$ into a region :]e !y h be5 foliat$ by pressure4 ,! mo/ ?or\ghly metamorphos$ rocks may sometimes be trac$ out into unalt]$ s$im5t>y or igne\s rocks1 or among !m may be f\nd pat*es ( little *ange :]e _! hi/ory maybe read4 ,metamorphism is mo/ common among rocks ( ! e>li] geological ages1 & mo/ r>e among rocks ( rec5t =mation4 ,no d\bt x is n[ 9 progress :]e deep-buri$ s$im5ts are invad$ by heat ei!r f intrusive igne\s masses or f ! e>?'s int]ior1 or are suff]+ sl[ de=mation "u ! ?ru/ ( m\nta9-mak+ =ces4 ,sugge/ h[ rocks n[ 9 process ( metamorphism may sometimes be expos$ to view4 ,:y d metamorphic rocks appe> on ! surface to-day8 ,m9]al ,ve9s ,9 regions ( fold$ & brok5 rocks fissures are frequ5tly f\nd to be fill$ ) %eets ( cry/all9e m9]als deposit$ f solution by und]gr\nd wat]1 & fissures ?us fill$ are kn[n z m9]al ve9s4 ,mu* ( ! importance ( m9]al ve9s is due to ! fact t !y are (t5 metallif]\s1 c>ry+ valuable native metals & metallic ores dissem9at$ 9 f9e p>ticles1 9 /r+s1 & sometimes 9 l>ge masses 9 ! mid/ ( ! valueless nonmetallic m9]als :i* make up :at is kn[n z ! ve9 /one4 ,! mo/ common ve9 /ones are qu>tz & calcite4 fluorite 7calcium fluoride71 a m9]al h>d] ?an calcite & cry/alliz+ 9 cubes ( v>i\s colors1 & b>ite 7b>ium sulphate71 a heavy :ite m9]al1 are abundant 9 _m ve9s4 ,illu/ration3 ,fig4 #beh4 ,plac] ,deposits 9 ,cali=nia g1 gold-be>+ gravels 9 pres5t riv] b$s2 g1 anci5t gold-be>+ riv] gravels2 a1 a1 lava fl[s capp+ table m\nta9s2 s1 slate4 ,draw a diagram %[+ by dott$ l9es conditions be=e ! lava fl[s occurr$4 ,:at *anges h s9ce tak5 place8 ,! gold-be>+ qu>tz ve9s ( ,cali=nia trav]se ! metamorphic slates ( ! ,si]ra ,nevada ,m\nta9s4 ,bel[ ! zone ( solution 7p4 #de7 ^! ve9s consi/ ( a ve9 /one ( qu>tz m+l$ ) pyrite 7p4 #ac71 ! latt] conta9+ ?reads & gra9s ( native gold4 ,b to ! dep? ( ab\t fifty feet f ! surface ! pyrite ( ! ve9 has be5 dissolv$1 leav+ a ru/y1 cellul> qu>tz ) gra9s ( ! insoluble gold scatt]$ ?r\gh x4 ,! plac] deposits ( ,cali=nia & o!r regions are gold-be>+ deposits ( gravel & s& 9 riv] b$s4 ,! heavy gold is apt to be f\nd mo/ly ne> or ^u ! solid rock1 & its gra9s1 l ^? ( ! s&1 are always r\nd$4 ,h[ ! gold came 9 ! plac]s we may leave ! pupil to sugge/4 ,copp] is f\nd 9 a numb] ( ores1 & also 9 ! native metal4 ,bel[ ! zone ( surface *anges ! ore ( a copp] ve9 is (t5 a d\ble sulphide ( iron & copp] call$ *alcopyrite1 a m9]al s(t] ?an pyrite--x c easily be scrat*$ ) a knife--& deep] yell[ 9 color4 ,= sev]al score ( feet bel[ ! gr\nd ! ve9 may consi/ ( ru/y qu>tz f :i* ! metallic ores h be5 dissolv$2 b at ! base ( ! zone ( solution we may f9d exce$+ly ri* deposits ( copp] ores1--copp] sulphides1 r$ & black copp] oxides1 & gre5 & blue copp] c>bonates1 :i* h cle>ly be5 br\ght d[n 9 solution f ! lea*$ upp] portion ( ! ve94 ,orig9 ( m9]al ve9s4 ,bo? ve9 /ones & ores h be5 deposit$ sl[ly f solution 9 wat]1 mu* z cry/als ( salt are deposit$ on ! sides ( a j> ( saturat$ br9e4 ,9 our /udy ( und]gr\nd wat] we le>n$ t x is ev]y:]e circulat+ ?r\gh ! p]meable rocks ( ! cru/1 desc5d+ to pr(\nd dep?s "u ! action ( gravity & aga9 driv5 to ! surface by hydro/atic pressure4 ,n[ fissures1 :]ev] !y occur1 =m ! trunk *annels ( ! und]gr\nd circulation4 ,wat] desc5ds f ! surface along ^! rifts2 x moves lat]ally f ei!r side to ! fissure plane1 j z gr\nd wat] seeps ?r\gh ! surr\nd+ rocks f e direction to a well2 & x asc5ds ?r\gh ^! natural wat] ways z 9 an artesian well1 :5ev] !y int]sect an aquif] 9 :i* wat] is "u hydro/atic pressure4 ,! wat]s :i* deposit ve9 /ones & ores are commonly hot1 & 9 _m cases !y h d]iv$ _! heat f intrusions ( igne\s rock /ill uncool$ )9 ! cru/4 ,! solv5t p[] ( ! wat] is ?us greatly increas$1 & x takes up into solution v>i\s sub/ances f ! igne\s & s$im5t>y rocks :i* x trav]ses4 ,= v>i\s reasons ^! sub/ances /ances are deposit$ 9 ! ve9 z ores & ve9 /ones4 ,on ris+ ?r\gh ! fissure ! wat] cools & loses pressure1 & its capacity to hold m9]als 9 solution is !re=e less5$4 ,besides1 z diff]5t curr5ts meet 9 ! fissure1 "s asc5d+1 "s desc5d+1 & "s com+ 9 f ! sides1 ! *emical reaction ( ^! v>i\s weak solutions ^u "o ano!r & ^u ! walls ( ! ve9 precipitates ! m9]als ( ve9 /uffs & ores4 ,z an illu/ration ( ! me?od ( ve9 deposits we may cite ! case ( a wood5 box pipe us$ 9 ! ,com/ock m9es1 ,nevada1 to c>ry ! hot wat] ( ! m9e f "o level to ano!r1 :i* 9 t5 ye>s 0 l9$ ) calcium c>bonate m ?an half an in* ?ick4 ,! ,/eamboat ,spr+s1 ,nevada1 furni% examples ( m9]al ve9s 9 process ( =mation4 ,! /eam+ wat] rises ?r\gh fissures 9 volcanic rocks & is n[ deposit+ 9 ! rifts a ve9 /one ( qu>tz1 ) metallic ores ( iron1 m]cury1 lead1 & o!r metals4 ,reconc5tration4 ,ne> ! base ( ! zone ( solution ve9s are (t5 /or$ ) exceptionally l>ge & valuable ore deposits4 ,?is local enri*m5t ( ! ve9 is due to ! reconc5tration ( its metallif]\s ores4 ,z ! surface ( ! l& is sl[ly l[]$ by wea!r+ & runn+ wat]1 ! zone ( solution is l[]$ at an equal rate & encroa*es con/antly on ! zone ( cem5tation4 ,! m9]als ( ve9s are !re=e con/antly be+ dissolv$ along _! upp] portions & c>ri$ d[n ! fissures by gr\nd wat] to l[] levels1 :]e !y are r$eposit$4 ,_m ( ! ri*e/ ore deposits are ?us due to successive conc5trations3 ! ores 7 lea*$ orig9ally f ! rocks to a l>ge ext5t by lat]ally seep+ wat]s2 !y 7 conc5trat$ 9 ! ore deposits ( ! ve9 *iefly by asc5d+ curr5ts2 !y h be5 reconc5trat$ by desc5d+ wat]s 9 ! way j m5tion$4 ,! orig9al s\rce ( ! metals4 ,x is to ! igne\s rocks t we may look = ! orig9al s\rce ( ! metals ( ve9s4 ,lavas conta9 m9ute p]c5tages ( v>i\s metallic comp\nds1 & no d\bt ?is 0 ! case also ) ! igne\s rocks :i* =m$ ! orig9al e>? cru/4 ,by ! erosion ( ! igne\s rocks ! metals h be5 di/ribut$ among s$im5t>y /rata1 & ev5 ! sea has tak5 into solution an appreciable am\nt ( gold & o!r metals1 b 9 ?is widely diffus$ condition !y are :olly useless to man4 ,! conc5tration :i* has made !m available is due to ! int]action ( _m ag5cies4 ,e>? movem5ts fractur+ deeply ! rocks ( ! cru/1 ! intrusion ( heat$ masses1 ! circulation ( und]gr\nd wat]s1 h all cop]at$ 9 ! conc5tration ( ! metals ( m9]al ve9s4 ,:ile fissure ve9s are ! mo/ important ( m9]al ve9s1 ! latt] t]m is appli$ also to any wat] way :i* has be5 fill$ by simil> deposits f solution4 ,?us 9 soluble rocks1 su* z lime/ones1 jo9ts enl>g$ by p]colat+ wat] are sometimes fill$ ) metallif]\s deposits1 z1 = example1 ! lead & z9c deposits ( ! upp] ,mississippi valley4 ,ev5 a por\s aquif] may be made ! seat ( m9]al deposits1 z 9 ! case ( "s copp]-be>+ & silv]-be>+ s&/ones ( ,new ,mexico4 99 99 99 99 99 ,illu/ration3 ,fig4 #bfj4 ,geological ,map ( ! ,unit$ /ates & ,"p ( ,canada 99 99 99 99 99 ,,"p ,,iii ,,hi/orical ,,geology ,,*apt] ,,xiv ,,! ,,geological ,,record ,:at a =mation records4 ,we h already le>n$ t ea* individual body ( /ratifi$ rock1 or =mation1 con/itutes a record ( ! "t :5 x 0 laid4 ,! /ructure & ! "* ( ! s$im5ts ( ea* =mation tell :e!r ! area 0 l& or sea at ! "t :5 !y 7 spread2 & if ! =m]1 :e!r ! l& 0 riv] pla91 or lake b$1 or 0 cov]$ ) w9d-bl[n s&s1 or by ! deposits ( an ice %eet4 ,if ! s$im5ts are m>9e1 we may "k also :e!r !y 7 laid 9 %oal wat] ne> ! %ore or 9 deep] wat] out at sea1 & :e!r dur+ a p]iod ( em]g5ce1 or dur+ a p]iod ( subsid5ce :5 ! sea transgress$ ! l&4 ,by ! same means ea* =mation records ! /age 9 ! cycle ( erosion ( ! l& mass f :i* its s$im5ts 7 d]iv$ 7p4 #ahe74 ,an uncon=mity betwe5 two m>9e =mations records ! fact t betwe5 ! p]iods :5 !y 7 deposit$ 9 ! sea ! area em]g$ z l& & suff]$ erosion 7p4 #bbg74 ,! attitude & /ructure ( ! /rata tell also ( ! fold+s & fractures1 ! de=mation & ! metamorphism1 :i* !y h suff]$2 & ! igne\s rocks associat$ ) !m z lava fl[s & igne\s intrusions add o!r details to ! /ory4 ,ea* =mation is ?us a sep>ate local *apt] 9 ! geological hi/ory ( ! e>?1 & its /rata are its leaves4 ,x conta9s an au!ntic record ( ! physical conditions--! geography--( ! "t & place :5 & :]e its s$im5ts 7 laid4 ,pa/ cycles ( erosion4 ,^! *apt]s 9 ! hi/ory ( ! planet are v num]\s1 al?\gh mu* ( ! record has be5 de/roy$ 9 v>i\s ways4 ,a succession ( diff]5t =mations is usually se5 9 any consid]able section ( ! cru/1 su* z a deep canyon or :]e ! edges ( upturn$ /rata are expos$ to view on ! flanks ( m\nta9 ranges2 & 9 any ext5sive area1 su* z a /ate ( ! ,union or a prov9ce ( ,canada1 ! numb] ( =mations outcropp+ on ! surface is l>ge4 ,x is ?us le>n$ t our pres5t cont95t is made up = ! mo/ "p ( old cont95tal deltas4 ,"s1 rec5tly em]g$ z ! /rata ( "y coa/al pla9s1 are ! records ( rec5t cycles ( erosion2 :ile o!rs 7 deposit$ 9 ! e>ly hi/ory ( ! e>?1 & 9 _m in/ances h be5 crumpl$ into m\nta9s1 :i* aft]w>ds 7 level$ to _! bases & l[]$ b5ea? ! sea to receive a cov] ( lat] s$im5ts be=e !y 7 aga9 uplift$ to =m l&4 ,! cycle ( erosion n[ 9 progress & record$ 9 ! lay]s ( /ratifi$ rock be+ spread b5ea? ! sea 9 cont95tal deltas has !re=e be5 prec$$ by _m simil> cycles4 ,aga9 & aga9 movem5ts ( ! cru/ h br\ght to an end "o cycle--sometimes :5 only well "u way1 & sometimes :5 draw+ t[>d its close--& h begun ano!r4 ,aga9 & aga9 !y h add$ to ! l& areas :i* be=e 7 sea1 ) all _! deposition records ( e>li] cycles1 or h l[]$ areas ( l& b5ea? ! sea to receive new s$im5ts4 ,! age ( ! e>?4 ,! ?ickness ( ! /ratifi$ rocks n[ expos$ ^u ! erod$ surface ( ! cont95ts is v great4 ,9 ! ,appala*ian region ! /rata are sev5 or eight miles ?ick1 & /ill great] ?icknesses h be5 measur$ 9 sev]al o!r m\nta9 ranges4 ,! aggregate ?ickness ( all ! =mations ( ! /ratifi$ rocks ( ! e>?'s cru/1 giv+ to ea* =mation its maximum ?ickness :]ev] f\nd1 am\nts to n less ?an =ty miles4 ,kn[+ h[ sl[ly s$im5ts accumulate ^u ! sea floor 7p4 #ahd71 we mu/ believe t ! successive cycles :i* ! e>? has se5 /ret* back into a pa/ almo/ inconceivably remote1 & measure t5s ( millions & p]haps ev5 hundr$s ( millions ( ye>s4 ,h[ ! =mations are correlat$ & ! geological record made up4 ,arrang$ 9 ! ord] ( _! succession1 ! =mations ( ! e>?'s cru/ w\ld con/itute a connect$ record 9 :i* ! geological hi/ory ( ! planet may be read1 & !re=e kn[n z ! geological record4 ,b to arrange ! =mations 9 _! natural ord] is n an easy task4 ,a complete set ( ! volumes ( ! record is to be f\nd 9 no s+le region4 ,_! leaves & *apt]s are scatt]$ ov] ! l& surface ( ! globe4 ,9 "o area c]ta9 *apt]s may be f\nd1 ?\gh p]haps ) _m miss+ leaves1 & ) int]v5+ *apt]s want+1 & ^! abs5t p>ts p]haps c be suppli$ only aft] long se>* ?r\gh _m o!r regions4 ,adjac5t /rata 9 any region are arrang$ accord+ to ! law ( sup]position1 i4e4 any /ratum is y\ng] ?an t on :i* x 0 deposit$1 j z 9 a pile ( pap]1 any %eet 0 laid lat] ?an t on :i* x re/s4 ,:]e rocks h be5 di/urb$1 _! orig9al attitude mu/ be det]m9$ be=e ! law c be appli$4 ,nor c ! law ( sup]position be us$ 9 id5tify+ & comp>+ ! /rata ( diff]5t regions :]e ! =mations _c be trac$ cont9u\sly f "o region to ! o!r4 ,! =mations ( diff]5t regions are arrang$ 9 _! true ord] by ! law ( includ$ organisms2 i4e4 =mations1 h[ev] widely sep>at$1 :i* conta9 a simil> assemblage ( fossils are equival5t & belong to ! same division ( geological "t4 ,! correlation ( =mations by means ( fossils may be expla9$ by ! =mations n[ be+ deposit$ ab\t ! nor? ,atlantic4 ,li?ologically !y are extremely v>i\s4 ,on ! cont95tal %elf ( ,nor? ,am]ica lime/ones ( diff]5t k9ds are =m+ (f ,florida1 & s&/ones & %ales f ,georgia nor?w>d4 ,sep>at$ f !m by ! deep ,atlantic oozes are o!r s$im5t>y deposits n[ accumulat+ along ! we/ coa/ ( ,europe4 ,if n[ all ^! (f%ore =mations 7 rais$ to op5 air1 h[ c\ld !y be correlat$8 ,surely n by li?ological lik5ess1 = 9 ?is respect !y w\ld be q div]se4 ,all w\ld be simil>1 h[ev]1 9 ! fossils :i* !y conta94 ,"s fossil species w\ld be id5tical 9 all ^! =mations & o!rs w\ld be closely alli$4 ,mak+ all due all[ance = diff]5ces 9 species due to local diff]5ces 9 climate & o!r physical causes1 x w\ld /ill be pla9 t plants & animals s simil> liv$ at ! same p]iod ( "t1 & t ! =mations 9 :i* _! rema9s 7 imb$d$ 7 contemporane\s 9 a broad way4 ,! pres5ce ( ! bones ( :ales & o!r m>9e mammals w\ld prove t ! /rata 7 laid aft] ! appe>ance ( mammals ^u e>?1 & imb$d$ relics ( man w\ld give a /ill clos] approximation to _! age4 ,9 ! same way we correlate ! e>li] geological =mations4 ,= example1 9 #aijb !re 7 collect$ ! fir/ fossils ev] f\nd on ! ant>ctic cont95t4 ,among ! doz5 specim5s obta9$ 7 "s fossil ammonites 7a family ( *amb]$ %ells7 ( g5]a :i* are f\nd on o!r cont95ts 9 c]ta9 =mations classifi$ z ! ,cretace\s sy/em1 & :i* occur nei!r above ^! =mations nor bel[ !m4 ,on ! basis ( ^! few fossils we may be confid5t t ! /rata 9 :i* !y 7 f\nd 9 ! ant>ctic region 7 laid 9 ! same p]iod ( geologic "t z 7 ! ,cretace\s rocks ( ! ,unit$ ,/ates & ,canada4 ,! record z a "t scale4 ,by means ( ! law ( includ$ organisms & ! law ( sup]position ! =mations ( diff]5t c\ntries & cont95ts are correlat$ & arrang$ 9 _! natural ord]4 ,:5 ! geological record is ?us obta9$ x may be us$ z a univ]sal "t scale = geological hi/ory4 ,geological "t is sep>at$ into divisions correspond+ to ! times dur+ :i* ! successive =mations 7 laid4 ,! l>ge/ assemblages ( =mations are kn[n z gr\ps1 :ile ! correspond+ divisions ( "t are kn[n z eras4 ,gr\ps are subdivid$ into sy/ems1 & sy/ems into s]ies4 ,s]ies are divid$ into /ages & sub/ages1--subdivisions :i* d n conc]n u 9 ?is brief treatise4 ,! correspond+ divisions ( "t are giv5 9 ! foll[+ table4 ,/rata ,"t ,gr\p ,era ,sy/em ,p]iod ,s]ies ,epo* ,! geologi/ is n[ prep>$ to read ! physical hi/ory--! geographical developm5t--( any c\ntry or ( any cont95t by means ( its =mations1 :5 he has giv5 ea* =mation its true place 9 ! geological record z a "t scale4 ,! foll[+ *>t exhibits ! ma9 divisions ( ! record1 ! "n giv5 to ea* be+ giv5 also to ! correspond+ "t division4 ,?us we speak ( ! ,cambrian sy/em1 mean+ a c]ta9 succession ( =mations :i* are classifi$ toge!r because ( broad resemblances 9 _! includ$ organisms2 & ( ! ,cambrian p]iod1 mean+ ! "t dur+ :i* ^! rocks 7 deposit$4 ,gr\p & ,era ,sy/em & ,p]iod ,s]ies & ,epo* ,rec5t ,quat]n>y 4 4 4 4 ,plei/oc5e ,c5ozoic 4 4 4 4 ,plioc5e ,t]ti>y 4 4 4 4 ,mioc5e ,eoc5e ,cretace\s ,mesozoic 4 4 4 4 ,jurassic ,triassic ,p]mian ,c>bonif]\s 4 4 ,p5nsylvanian ,mississippian ,paleozoic 4 4 4 4 ,devonian ,silurian ,ordovician ,cambrian ,algonkian ,ar*ean ,fossils & :at !y tea* ,! geological =mations conta9 a record /ill m important ?an t ( ! geographical developm5t ( ! cont95ts2 ! fossils imb$d$ 9 ! rocks ( ea* =mation tell ( ! k9ds ( animals & plants :i* inhabit$ ! e>? at t "t1 & f ^! fossils we are !re=e able to con/ruct ! hi/ory ( life ^u ! e>?4 ,fossils4 ,^! rema9s ( organisms are f\nd 9 ! /rata 9 all degrees ( p]fection1 f trails & tracks & fragm5t>y impressions1 to p]fectly pres]v$ %ells1 wood1 bones1 & complete skeletons4 ,z a rule1 x is only ! h>d p>ts ( animals & plants :i* h left any traces 9 ! rocks4 ,sometimes ! orig9al h>d sub/ance is pres]v$1 b m (t5 x has be5 replac$ by "s less soluble mat]ial4 ,petrifaction1 z ?is process ( sl[ replacem5t is call$1 is (t5 c>ri$ on 9 ! mo/ exquisite detail4 ,:5 wood1 = example1 is und]go+ petrifaction1 ! woody tissue may be replac$1 p>ticle by p>ticle1 by silica 9 solution ?r\gh ! action ( und]gr\nd wat]s1 ev5 ! microscopic /ructures ( ! wood be+ p]fectly reproduc$4 ,9 %ells orig9ally made ( aragonite1 a cry/all9e =m ( c>bonate ( lime1 t m9]al is usually replac$ by calcite1 a m /able =m ( ! same sub/ance4 ,! mo/ common petrify+ mat]ials are calcite1 silica1 & pyrite4 ,(t5 ! organic sub/ance has nei!r be5 pres]v$ nor replac$1 b ! =m has be5 reta9$ by means ( molds & ca/s4 ,p]man5t impressions1 or molds1 may be made 9 s$im5ts n only by ! h>d p>ts ( organisms1 b also by su* s(t & p]i%able p>ts z ! leaves ( plants1 &1 9 ! r>e/ in/ances1 by ! sk9 ( animals & ! fea!rs ( birds4 ,9 f9e-gra9$ lime/ones ev5 ! impr9ts ( jellyfi% h be5 reta9$4 ,! diff]5t k9ds ( molds & ca/s may be illu/rat$ by means ( a clam %ell & "s moi/ clay1 ! latt] repres5t+ ! s$im5ts 9 :i* ! rema9s ( animals & plants are entomb$4 ,imb$d+ ! %ell 9 ! clay & all[+ ! clay to h>d51 we h a mold ( ! ext]ior ( ! %ell1 z is se5 on cutt+ ! clay matrix 9 two & remov+ ! %ell f x4 ,fill+ ?is mold ) clay ( diff]5t color1 we obta9 a ca/ ( ! ext]ior1 :i* repres5ts accurately ! orig9al =m & surface m>k+s ( ! %ell4 ,9 nature1 %ells & o!r relics ( animals or plants are (t5 remov$ by be+ dissolv$ by p]colat+ wat]s1 & ! molds are ei!r fill$ ) s$im5ts or ) m9]als deposit$ f solution4 ,:]e ! fossil is holl[1 a ca/ ( ! int]ior is made 9 ! same way4 ,int]ior ca/s ( %ells reproduce any m>k+s on ! inside ( ! valves1 & ca/s ( ! int]ior ( ! skulls ( anci5t v]tebrates %[ ! =m & size ( _! bra9s4 ,imp]fection ( ! life record4 ,at ! pres5t "t only ! smalle/ fraction ( ! life on e>? ev] gets entomb$ 9 rocks n[ =m+4 ,9 ! =e/ great fall5 tree trunks1 z well z dead leaves1 decay1 & only add a little to ! lay] ( d>k vegetable mold f :i* !y grew4 ,! bones ( l& animals are1 = ! mo/ "p1 left unburi$ on ! surface & are soon de/roy$ by *emical ag5cies4 ,ev5 :]e1 z 9 ! swamps ( riv]1 flood pla9s & 9 o!r bogs1 !re are pres]v$ ! rema9s ( plants1 & sometimes insects1 toge!r ) ! bones ( "s animal dr[n$ or mir$1 9 mo/ cases ^! swamp & bog deposits are soon] or lat] de/roy$ by ! %ift+ *annels ( ! /ream or by ! g5]al erosion ( ! l&4 ,9 ! sea ! conditions = pres]vation are m favorable ?an on l&2 yet ev5 "h ! proportion ( animals & plants ^: h>d p>ts are fossiliz$ is v small comp>$ ) ^? :i* ei!r totally decay be=e !y are buri$ 9 sl[ly accumulat+ s$im5ts or are gr\nd to p[d] by waves & curr5ts4 ,we may inf] t dur+ ea* p]iod ( ! pa/1 z at ! pres5t1 only a v insignificant fraction ( ! innum]able organisms ( sea & l& escap$ de/ruction & left 9 cont95tal & oceanic deposits p]man5t records ( _! exi/5ce4 ,scanty z ^! orig9al life records mu/ h be51 !y h be5 l>gely de/roy$ by metamorphism ( ! rocks 9 :i* !y 7 imb$d$1 by solution 9 und]gr\nd wat]s1 & by ! va/ d5udation "u :i* ! s$im5ts ( e>li] p]iods h be5 erod$ to furni% mat]ials = ! s$im5t>y records ( lat] times4 ,moreov]1 v mu* ( :at has escap$ de/ruction /ill rema9s undiscov]$4 ,! imm5se bulk ( ! /ratifi$ rocks is buri$ & inaccessible1 & ! records ( ! pa/ :i* x conta9s c nev] be kn[n4 ,comp>atively few outcrops h be5 ?or\ghly se>*$ = fossils4 ,al?\gh new species are con/antly be+ discov]$1 ea* discov]y may be consid]$ z ! outcome ( a s]ies ( happy accid5ts1--t ! rema9s ( individuals ( ?is p>ticul> species happ5$ to be imb$d$ & fossiliz$1 t !y happ5$ to escape de/ruction dur+ long ages1 & t !y happ5$ to be expos$ & f\nd4 ,"s inf]5ces f ! records ( ! hi/ory ( life ^u ! planet4 ,meag] z are ^! records1 !y set =? pla9ly "s important tru?s :i* we w n[ briefly m5tion4 #a4 ,ea* s]ies ( ! /ratifi$ rocks1 except ! v deepe/1 conta9s ve/iges ( life4 ,h5ce ! e>? 0 t5ant$ by liv+ creatures = an uncalculat$ l5g? ( "t be=e human hi/ory began4 #b4 ,life on ! e>? has be5 ev]-*ang+4 ,! y\nge/ /rata hold ! rema9s ( exi/+ species ( animals & plants & ^? ( species & v>ieties closely alli$ to !m4 ,/rata some:at old] conta9 few] exi/+ species1 & 9 /rata ( a /ill e>li]1 b by no means an anci5t epo*1 no exi/+ species are to be f\nd2 ! species ( t epo* & ( previ\s epo*s h vani%$ f ! liv+ _w4 ,dur+ all geological "t s9ce life began on e>? old species h con/antly become ext9ct & ) !m ! g5]a & families to :i* !y belong1 & o!r species1 g5]a1 & families h replac$ !m4 ,! fossils ( ea* =mation diff] on ! :ole f ^? ( e o!r4 ,! assemblage ( animals & plants 7! fauna-flora7 ( ea* epo* diff]s f t ( e o!r epo*4 ,9 _m cases ! ext9ction ( a type has be5 gradual2 9 o!r in/ances app>5tly abrupt4 ,!re is no evid5ce t any organism once become ext9ct has ev] reappe>$4 ,! duration ( a species 9 "t1 or its v]tical range ?r\gh ! /rata1 v>ies greatly4 ,"s species are limit$ to a /ratum a few feet 9 ?ickness2 "s may range ?r\gh an entire =mation & be f\nd b little modifi$ 9 /ill high] b$s4 ,a =mation may ?us (t5 be divid$ into zones1 ea* *>act]iz$ by its own peculi> species4 ,z a rule1 ! simpl] organisms h a long] duration z species1 ?\gh n z individuals1 ?an ! m complex4 #c4 ,! l>g] zological & botanical gr\p+s survive long] ?an ! small]4 ,species are s %ort-liv$ t a s+le geological epo* may be m>k$ by sev]al m or less complete ext9ctions ( ! species ( its fauna-flora & _! replacem5t by o!r species4 ,a g5us cont9ues ) new species aft] all ! species ) :i* x began h become ext9ct4 ,families survive g5]a1 & ord]s families4 ,classes are s long-liv$ t mo/ ( ^? :i* are kn[n f ! e>lie/ =mations are repres5t$ by liv+ =ms1 & no subk+dom has ev] become ext9ct4 ,?us1 to take an example f ! /ony corals1--! zoan?>ia1--! p>ticul> *>act]s--:i* con/itut$ a c]ta9 species--,facosites niag>5sis--( ! ord] are conf9$ to ! ,niag>a s]ies4 ,its g5]ic *>act]s appe>$ 9 o!r species e>li] 9 ! ,silurian & cont9u$ ?r\gh ! ,devonian4 ,its family *>act]s1 repres5t$ 9 diff]5t g5]a & species1 range f ! ,ordovician to ! close ( ! ,paleozoic2 :ile ! *>act]s :i* x %>es ) all its ord]1 ! ,zoan?>ia1 began 9 ! ,cambrian & are f\nd 9 liv+ species4 #d4 ,! *ange 9 organisms has be5 gradual4 ,! fossils ( ea* life zone & ( ea* =mation ( a con=mable s]ies closely resemble1 ) "s expla9able exceptions1 ^? ( ! b$s imm$iately above & bel[4 ,! animals & plants :i* t5ant$ ! e>? dur+ any geological epo* are s closely relat$ to ^? ( ! prec$+ & ! succe$+ epo*s t we may consid] !m to be ! desc5dants ( ! "o & ! ance/ors ( ! o!r1 ?us acc\nt+ = ! resemblance by h]$ity4 ,x is !re=e believ$ t ! species ( animals & plants n[ liv+ on ! e>? are ! desc5dants ( ! species ^: rema9s we f9d entomb$ 9 ! rocks1 & t ! *a9 ( life has be5 unbrok5 s9ce its beg9n+4 #e4 ,! *ange 9 species has be5 a gradual diff]5tiation4 ,trac+ ! l9es ( desc5t ( v>i\s animals & plants ( ! pres5t backw>d ?r\gh ! divisions ( geologic "t1 we f9d t ^! l9es ( desc5t conv]ge & unite 9 simpl] & /ill simpl] types4 ,! developm5t ( life may be repres5t$ by a tree ^: trunk is f\nd 9 ! e>lie/ ages & ^: bran*es spread & subdivide to ! gr[+ twigs ( pres5t species4 #f4 ,! *ange 9 organisms ?r\gh\t geologic "t has be5 a progressive *ange4 ,9 ! e>lie/ ages ! only animals & plants on ! e>? 7 l[ly =ms1 simple & g5]aliz$ 9 /ructure2 :ile succe$+ ages h be5 *>act]iz$ by ! introduction ( types m & m specializ$ & complex1 & !re=e ( high] rank 9 ! scale ( be+4 ,?us ! ,algonkian conta9s ! rema9s ( only ! humble/ =ms ( ! inv]tebrates4 ,9 ! ,cambrian1 ,ordovician1 & ,silurian ! inv]tebrates 7 repres5t$ 9 all _! subk+doms by a v>i$ fauna4 ,9 ! ,devonian1 fi%es--! l[e/ ( ! v]tebrates--became abundant4 ,amphibians made _! entry on ! /age 9 ! ,c>bonif]\s1 & reptiles came to rule ! _w 9 ! ,mesozoic4 ,mammals culm9at$ 9 ! ,t]ti>y 9 /range =ms :i* became m & m l ^? ( ! pres5t z ! long ages ( t era roll$ on2 & late/ ( all appe>$ ! noble/ product ( ! creative process1 man4 ,j z gr[? is *>act]i/ic ( ! individual life1 s gradual1 progressive *ange1 or evolution1 has *>act]iz$ ! hi/ory ( life ^u ! planet4 ,! evolution ( ! organic k+dom f its primitive g]m9al =ms to ! complex & highly organiz$ fauna-flora ( to-day may be comp>$ to ! gr[? ( "s noble oak z x rises f ! acorn1 spread+ l(ti] & m widely ext5d$ bran*es z x gr[s4 #g4 ,:ile high] & /ill high] types h cont9ually be5 evolv$1 until man1 ! highe/ ( all1 appe>$1 ! l[] & e>li] types h g5]ally p]si/$4 ,"s :i* rea*$ _! culm9ation e>ly 9 ! hi/ory ( ! e>? h s9ce *ang$ only 9 slight adju/m5ts to a *ang+ environm5t4 ,?us ! bra*iopods1 a type ( %ellfi%1 h made no progress s9ce ! ,paleozoic1 & "s ( _! e>lie/ kn[n g5]a are repres5t$ by liv+ =ms h>dly to be di/+ui%$ f _! anci5t ance/ors4 ,! l[e/ & e>lie/ bran*es ( ! tree ( life h ris5 to no high] levels s9ce !y rea*$ _! climax ( developm5t long ago4 #h4 ,a /range p>allel has be5 f\nd to exi/ betwe5 ! evolution ( organisms & ! developm5t ( ! individual4 ,9 ! embryonic /ages ( its gr[? ! individual passes swiftly ?r\gh ! successive /ages ?r\gh :i* its ance/ors evolv$ dur+ ! millions ( ye>s ( geologic "t4 ,! developm5t ( ! individual recapitulates ! evolution ( ! race4 99 99 99 99 99 ,! frog is a typical amphibian4 ,z a tadpole x passes ?r\gh a /age id5tical 9 sev]al well-kn[n features ) ! maturity ( fi%es2 z1 = example1 its aquatic life1 ! tail by :i* x swims1 & ! gills ?r\gh :i* x brea!s4 ,x is a fair inf]5ce t ! tadpole /age 9 ! life hi/ory ( ! frog repres5ts a /age 9 ! evolution ( its k9d1--t ! ,amphibia are d]iv$ f fi%like ance/ral =ms4 ,?is inf]5ce is amply confirm$ 9 ! geological record2 fi%es appe>$ be=e ,amphibia & 7 connect$ ) !m by transitional =ms4 ,! great l5g? ( geologic "t inf]r$ f ! sl[ *ange ( species4 ,life =ms1 l l& =ms1 are ?us subject to *ange "u ! influ5ce ( _! *ang+ environm5t & ( =ces act+ f )94 ,h[ sl[ly !y *ange may be se5 9 ! app>5t /ability ( exi/+ species4 ,9 ! lifetime ( ! obs]v] & ev5 9 ! record$ hi/ory ( man1 species seem z /able z ! m\nta9 & ! riv]4 ,b life =ms & l& =ms are alike v>iable1 bo? 9 nature & /ill m "u ! %ap+ h& ( man4 ,z man has modifi$ ! face ( ! e>? ) 8 great eng9e]+ works1 s he has produc$ widely diff]5t v>ieties ( _m k9ds ( dome/icat$ plants & animals1 su* z ! v>ieties ( ! dog & ! horse1 ! apple & ! rose1 :i* may be reg>d$ 9 "s respects z new species 9 ! mak+4 ,we h assum$ t l& =ms h *ang$ 9 ! pa/ "u ! influ5ce ( =ces n[ 9 op]ation4 ,assum+ also t life =ms h always *ang$ z !y are *ang+ at pres5t1 we come to realize some?+ ( ! imm5sity ( geologic "t requir$ = ! evolution ( life f its e>lie/ l[ly =ms up to man4 ,x is because ! onw>d m>* ( life has tak5 ! same g5]al c\rse ! _w ov] t we are able to use x z a univ]sal "t scale & divide geologic "t into ages & m9or subdivisions accord+ to ! rul+ or *>act]i/ic organisms !n liv+ on ! e>?4 ,?us1 s9ce v]tebrates appe>$1 we h 9 succession ! ,age ( ,fi%es1 ! ,age ( ,amphibians1 ! ,age ( ,reptiles1 & ! ,age ( ,mammals4 ,! *>t giv5 on page #bie is ?us bas$ on ! law ( sup]position & ! law ( ! evolution ( organisms4 ,! fir/ law gives ! succession ( ! =mations 9 local areas4 ,! fossils :i* !y conta9 demon/rate ! law ( ! progressive appe>ance ( organisms1 & by means ( ?is law ! =mations ( diff]5t c\ntries are correlat$ & set ea* 9 its place 9 a univ]sal "t scale & gr\p$ toge!r accord+ to ! aff9ities ( _! imb$d$ organic rema9s4 ,geologic "t divisions comp>$ ) ^? ( human hi/ory4 ,we may comp>e ! division ( geologic "t into eras1 p]iods1 & o!r divisions accord+ to ! dom9ant life ( ! "t1 to ! ill-def9$ ages into :i* human hi/ory is divid$ accord+ to ! dom9ance ( "s nation1 rul]1 or o!r *>act]i/ic feature4 ,?us we speak ( ! ,d>k ,ages1 ! ,age ( ,elizabe?1 & ! ,age ( ,electricity4 ,^! crude divisions w\ld be ( mu* value if1 z 9 ! case ( geologic "t1 we _h no exact reckon+ ( human hi/ory by ye>s4 ,& z ! c\rse ( human hi/ory has fl[$ 9 an unbrok5 /ream along quiet rea*es ( sl[ *ange & ?r\gh p]iods ( rapid *ange & revolution1 s ) ! c\rse ( geologic hi/ory4 ,p]iods ( quiesc5ce1 9 :i* revolution>y =ces are p]haps ga!r+ head1 alt]nate ) p]iods ( comp>atively rapid *ange 9 physical geography & 9 organisms1 :5 new & high] =ms appe> :i* s]ve to draw ! b\nd>y l9e ( new epo*s4 ,nev]!less1 geological hi/ory is a cont9u\s progress2 its p]iods & epo*s %ade into "o ano!r by imp]ceptible gradations1 & all our subdivisions mu/ ne$s be vague & m or less arbitr>y4 ,h[ fossils tell ( ! geography ( ! pa/4 ,fossils are us$ n only z a record ( ! developm5t ( life ^u ! e>?1 b also 9 te/imony to ! physical geography ( pa/ epo*s4 ,!y indicate :e!r 9 any region ! climate 0 tropical1 temp]ate1 or arctic4 ,s9ce species spread sl[ly f "s c5t] ( disp]sion :]e !y orig9ate until "s b>ri] limits _! migration f>!r1 ! occurr5ce ( ! same species 9 rocks ( ! same sy/em 9 diff]5t c\ntries implies ! abs5ce ( su* b>ri]s at ! p]iod4 ,?us 9 ! collection ( ant>ctic fossils ref]r$ to on page #bid !re 7 %all[-wat] m>9e %ells id5tical 9 species ) ,mesozoic %ells f\nd 9 ,india & 9 ! s\!rn extremity ( ,s\? ,am]ica4 ,s9ce su* organisms are n di/ribut$ by ! curr5ts ( ! deep sea & _c migrate along its bottom1 we inf] a %all[-wat] connection 9 ,mesozoic times betwe5 ,india1 ,s\? ,am]ica1 & ! ant>ctic region4 ,su* a %all[-wat] connection w\ld be (f]$ along ! m>g9al %elf ( a cont95t unit+ ^! n[ widely sep>at$ c\ntries4 ,,*apt] ,,xv ,,! ,,pre-,,cambrian ,,sy/ems ,! e>?'s beg9n+s4 ,! geological record does n tell u ( ! beg9n+s ( ! e>?4 ,! hi/ory ( ! planet1 z we h e reason to believe1 /ret*es f> back beyond ! p]iod ( ! olde/ /ratifi$ rocks1 & is involv$ 9 ! hi/ory ( ! sol> sy/em & ( ! nebula1--! cl\d ( gl[+ gases or ( cosmic du/1--f :i* ! sun & planets are believ$ to h be5 d]iv$4 ,! nebul> hypo!sis4 ,x 0 long held t ! e>? began z a vapor\s1 %9+ sph]e1 =m$ by ! ga!r+ toge!r ( ! mat]ial ( a gase\s r+ :i* _h be5 deta*$ f a cool+ & %r9k+ nebula4 ,su* a vapor\s sph]e w\ld cond5se to a liquid fi]y globe1 ^: surface w\ld become cold & solid1 :ile ! int]ior w\ld long rema9 int5sely hot because ( ! sl[ conductivity ( ! cru/4 ,"u ^! conditions ! primeval atmosph]e ( ! e>? mu/ h conta9$ 9 vapor ! wat] n[ belong+ to ! e>?'s cru/ & surface4 ,x also held all ! oxyg5 s9ce lock$ up 9 rocks by _! oxidation1 & all ! c>bon dioxide :i* has s9ce be5 laid away 9 lime/ones1 besides t correspond+ to ! c>bon ( c>bonace\s deposits1 su* z peat1 coal1 & petroleum4 ,on ?is hypo!sis ! orig9al atmosph]e 0 d5se1 d>k1 & noxi\s1 & enorm\sly heavi] ?an ! atmosph]e at pres5t4 ,! accretion hypo!sis4 ,on ! o!r h&1 x has be5 rec5tly sugge/$ t ! e>? may h gr[n to its pres5t size by ! gradual accretion ( meteoritic masses4 ,su* cold1 /ony bodies might h come toge!r at s sl[ a rate t ! heat caus$ by _! impact w\ld n raise s5sibly ! temp]ature ( ! gr[+ planet4 ,?us ! surface ( ! e>? may nev] h be5 hot & lum9\s2 b z ! loose aggregation ( /ony masses grew l>g] & 0 m & m compress$ by its own gravitation1 ! heat ?us g5]at$ rais$ ! int]ior to high temp]atures1 :ile f "t to "t molt5 rock 0 intrud$ among ! loose1 cold meteoritic masses ( ! cru/ & outp\r$ ^u ! surface4 ,su* a spiral nebula might be =m$ by ! close approa* ( "o /> to ano!r1--( a pass+ /> to our own sun1 = example1 be=e ! bir? ( ! sol> sy/em4 ,z ! pull ( ! moon raises ! tides on opposite sides ( ! e>?1 s1 x is suppos$1 ! pull ( ! pass+ /> releas$ ! explosive =ces ( ! sun1 & two /reams ( matt] 7 flung out f x4 ,! knots 9 ! arms =m$ ! nuclei ( ! planets4 ,! gase\s matt] scatt]$ outside ! knots cool$ into small /ony masses1 revolv+ ab\t a c5tral mass & h5ce call$ planetesimals 7little planets74 ,l ! meteorites :i* /ill fall ^u ! e>?1 ! planetesimals 7 gradually ga!r$ 9 by ! nucle> knots1 :i* ?us grew to ! pres5t planets4 ,x is suppos$ t ! meteorites ( :i* ! e>? 0 built br\ght to x1 z meteorites d n[1 v>i\s gases %ut up )9 _! pores4 ,z ! heat ( ! int]ior increas$1 ^! gases transpir$ to ! surface & =m$ ! primitive atmosph]e & hydrosph]e4 ,! atmosph]e has !re=e gr[n sl[ly f ! smalle/ beg9n+s4 ,gases emitt$ f ! int]ior 9 volcanic eruptions & 9 o!r ways h ev] add$ to x1 & are add+ to x n[4 ,on ! o!r h&1 ! atmosph]e has con/antly suff]$ loss1 z x has be5 robb$ ( oxyg5 by ! oxidation ( rocks 9 wea!r+1 & ( c>bon dioxide 9 ! mak+ ( lime/ones & c>bonace\s deposits4 ,:ile all hypo!ses ( ! e>?'s beg9n+s are z yet unprov$ speculations1 !y s]ve to br+ to m9d "o ( ! *ief lessons :i* geology has to tea*1--t ! duration ( ! e>? 9 "t1 l ! ext5sion ( ! univ]se 9 space1 is va/ly beyond ! p[] ( ! human m9d to realize4 ,beh9d ! hi/ory record$ 9 ! rocks1 :i* /ret*es back = _m million ye>s1 lies ! long unrecord$ hi/ory ( ! beg9n+s ( ! planet2 & /ill f>!r 9 ! abysses ( ! pa/ are dimly se5 ! cycles ( ! evolution ( ! sol> sy/em & ( ! nebula :i* gave x bir?4 ,we pass n[ f ! dim realm ( speculation to ! e>lie/ era ( ! record$ hi/ory ( ! e>?1 :]e "s c]ta9 facts may be obs]v$ & "s sure inf]5ces f !m may be drawn4 ,! ,ar*ean ,! olde/ kn[n s$im5t>y /rata1 :]ev] !y are expos$ by uplift & erosion1 are f\nd to be involv$ ) a mass ( cry/all9e rocks :i* possesses ! same *>act]i/ics 9 all p>ts ( ! _w4 ,x consi/s ( foliat$ rocks1 gneisses1 & s*i/s ( v>i\s k9ds1 :i* h be5 cut ) dikes & o!r intrusions ( molt5 rock1 & h be5 brok51 crumpl$1 & cru%$1 & left 9 int]lock+ masses s confus$ t _! true arrangem5t c usually be made out only ) ! greate/ difficulty if at all4 ,! condition ( ?is body ( cry/all9e rocks is due to ! fact t !y h suff]$ n only f ! fault+s1 fold+s1 & igne\s intrusions ( _! "t1 b necess>ily1 also1 f ^? ( all lat] geological ages4 ,at pres5t ?ree lead+ !ories are held z to ! orig9 ( ^! basal cry/all9e rocks4 #a4 ,!y are consid]$ by p]haps ! majority ( ! geologi/s :o h /udi$ !m mo/ c>efully to be igne\s rocks intrud$ 9 a molt5 /ate among ! s$im5t>y rocks involv$ ) !m4 ,9 _m localities ?is relation is prov$ by ! ph5om5a ( contact 7p4 #bfh72 b = ! mo/ "p ! de=mations :i* ! rocks h s9ce suff]$ aga9 & aga9 h be5 suffici5t to de/roy su* evid5ce if x ev] exi/$4 #b4 ,an old] view reg>ds !m z pr(\ndly alt]$ s$im5t>y /rata1 ! mo/ anci5t ( ! e>?4 #c4 ,accord+ to a ?ird !ory !y repres5t portions ( ! e>?'s orig9al cru/2 n1 inde$1 its orig9al surface1 b deep] portions uncov]$ by erosion & aft]w>ds mantl$ ) s$im5t>y deposits4 ,all ^! !ories agree t ! pres5t foliat$ condition ( ^! rocks is due to ! int5se metamorphism :i* !y h suff]$4 ,x is to ?is body ( cry/all9e rocks & ! /ratifi$ rocks involv$ ) x1 :i* =m a v small proportion ( its mass1 t ! t]m ,ar*ean 7,greek1 ar*e1 beg9n+7 is appli$ by _m geologi/s4 ,! ,algonkian ,9 "s regions !re re/s uncon=mably on ! ,ar*ean an imm5se body ( /ratifi$ rocks1 ?\s&s & 9 places ev5 scores ( ?\s&s ( feet ?ick1 kn[n z ! ,algonkian4 ,great uncon=mities divide x into well-def9$ sy/ems1 b z only ! scantie/ traces ( fossils appe> "h & !re among its /rata1 x is z yet impossible to correlate ! =mations ( diff]5t regions & to give !m names ( m ?an local application4 ,we w describe ! ,algonkian rocks ( two typical areas4 ,! ,gr& ,canyon ( ! ,colorado4 ,we h already /udi$ a v anci5t p5epla9 ^: edge is expos$ to view deep on ! walls ( ! ,colorado ,canyon 7nu1 ,fig4 #bjg74 ,! =mation ( flat-ly+ s&/one :i* cov]s ?is buri$ l& surface is prov$ by its fossils to belong to ! ,cambrian1--! e>lie/ p]iod ( ! ,paleozoic era4 ,! tilt$ rocks 7b1 ,fig4 #bjg74 on ^: upturn$ edges ! ,cambrian s&/one re/s are f> old]1 = ! physical break :i* sep>ates !m f x records a "t int]val dur+ :i* !y 7 upheav$ to m\nta9\s ridges & worn d[n to a l[ pla94 ,!y are !re=e classifi$ z ,algonkian4 ,!y comprise two imm5se s]ies4 ,! upp] is m ?an five ?\s& feet ?ick & consi/s ( %ales & s&/ones ) "s lime/ones4 ,sep>at$ f x by an uncon=mity :i* does n appe> 9 ,figure #bjg1 ! l[] division1 sev5 ?\s& feet ?ick1 consi/s *iefly ( massive r$di% s&/ones ) sev5 or m %eets ( lava int]b$d$4 ,! l[e/ memb] is a basal conglom]ate compos$ ( pebbles d]iv$ f ! erosion ( ! d>k crumpl$ s*i/s b5ea?1--s*i/s :i* are suppos$ to be ,ar*ean4 ,z %[n 9 ,figure #bjg1 a /rong uncon=mity 7nm1 ,fig4 #bjg7 p>ts ! s*i/s & ! ,algonkian4 ,! floor on :i* ! ,algonkian re/s is rem>kably ev51 & "h aga9 is prov$ an int]val ( incalculable l5g?1 dur+ :i* an anci5t l& mass ( ,ar*ean rocks 0 baselevel$ be=e x receiv$ ! cov] ( ! s$im5ts ( ! lat] age4 ,! ,lake ,sup]ior region4 ,9 ea/]n ,canada an area ( pre-,cambrian rocks1 ,ar*ean & ,algonkian1 e/imat$ at two million squ>e miles1 /ret*es f ! ,great ,lakes & ! ,/4 ,lawr5ce ,riv] nor?w>d to ! conf9es ( ! cont95t1 inclos+ ,hudson ,bay 9 ! arms ( a gigantic ,u4 ,?is imm5se area1 :i* we h already /udi$ z ! ,laur5tian p5epla9 7p4 #hi71 ext5ds s\?w>d across ! ,canadian bord] into nor!rn ,m9nesota1 ,wiscons91 & ,mi*igan4 ,! rocks ( ?is area are kn[n to be pre-,cambrian2 = ! ,cambrian /rata1 :]ev] f\nd1 lie uncon=mably ^u !m4 ,illu/ration3 ,fig4 #bfb4 ,ideal ,section 9 ! ,lake ,sup]ior ,region ,! g5]al relations ( ! =mations ( t portion ( ! area :i* lies ab\t ,lake ,sup]ior are %[n 9 ,figure #bfb4 ,great uncon=mities1 ,,uu sep>ate ! ,algonkian bo? f ! ,ar*ean & f ! ,cambrian1 & divide x into ?ree di/9ct sy/ems1--! ,l[] ,huronian1 ! ,upp] ,huronian1 & ! ,kewe5awan4 ,! ,l[] & ! ,upp] ,huronian consi/ 9 ! ma9 ( old sea muds & s&s & limy oozes n[ *ang$ to gneisses1 s*i/s1 m>bles1 qu>tzites1 slates1 & o!r metamorphic rocks4 ,! ,kewe5awan is compos$ ( imm5se piles ( lava1 su* z ^? ( ,icel&1 ov]la9 by b$d$ s&/ones4 ,:at rema9s ( ^! rock sy/ems aft] ! d5udation ( all lat] geologic ages is enorm\s4 ,! ,l[] ,huronian is m ?an a mile ?ick1 ! ,upp] ,huronian m ?an two miles ?ick1 :ile ! ,kewe5awan exce$s n9e miles 9 ?ickness4 ,! va/ l5g? ( ,algonkian "t is %[n by ! ?ickness ( its m>9e deposits & by ! cycles ( erosion :i* x includes4 ,9 ,figure #bfb ! /ud5t may read an outl9e ( ! hi/ory ( ! ,lake ,sup]ior region1 ! de=mations :i* x suff]$1 _! relative sev]ity1 ! times :5 !y occurr$1 & ! erosion cycles m>k$ by ! successive uncon=mities4 ,o!r pre-,cambrian areas 9 ,nor? ,am]ica4 ,pre-,cambrian rocks are expos$ 9 v>i\s p>ts ( ! cont95t1 usually by ! erosion ( m\nta9 ranges 9 :i* _! /rata 7 infold$4 ,l>ge areas occur 9 ! m>itime prov9ces ( ,canada4 ,! core ( ! ,gre5 ,m\nta9s ( ,v]mont is pre-,cambrian1 & rocks ( ^! sy/ems occur 9 scatt]$ pat*es 9 we/]n ,massa*usetts4 ,"h belong also ! olde/ rocks ( ! ,highl&s ( ! ,hudson & ( ,new ,j]sey4 ,! ,adirondack region1 an outli] ( ! ,laur5tian region1 exposes pre-,cambrian rocks1 :i* h be5 metamorphos$ & tilt$ by ! intrusion ( a great boss ( igne\s rock out ( :i* ! c5tral peaks are c>v$4 ,! core ( ! ,blue ,ridge & probably mu* ( ! ,pi$mont ,belt are ( ?is age4 ,9 ! ,black ,hills ! irruption ( an imm5se mass ( granite has caus$ or accompani$ ! upheaval ( pre-,cambrian /rata & metamorphos$ !m by heat & pressure into gneisses1 s*i/s1 qu>tzites1 & slates4 ,9 mo/ ( ^! m\nta9\s regions ! l[e/ /rata are pr(\ndly *ang$ by metamorphism1 & !y c be assign$ to ! pre-,cambrian only :]e !y are cle>ly ov]la9 uncon=mably by =mations prov$ to be ,cambrian by _! fossils4 ,9 ! ,belt ,m\nta9s ( ,montana1 h[ev]1 ! ,cambrian is und]la9 by ,algonkian s$im5ts twelve ?\s& feet ?ick1 & b little alt]$4 ,m9]al weal? ( ! pre-,cambrian rocks4 ,! pre-,cambrian rocks are ( v great economic importance1 because ( _! ext5sive metamorphism & ! enorm\s masses ( igne\s rock :i* !y involve4 ,9 _m p>ts ( ! c\ntry !y are ! s\rce ( supply ( granite1 gneiss1 m>ble1 slate1 & o!r su* build+ mat]ials4 ,/ill m valuable are ! /ores ( iron & copp] & o!r metals :i* !y conta94 ,at ! pres5t "t ! pre-,cambrian region ab\t ,lake ,sup]ior leads ! _w 9 ! production ( iron ore1 its output = #aijc be+ m ?an five sev5?s ( ! entire output ( ! :ole ,unit$ ,/ates1 & exce$+ t ( any =eign c\ntry4 ,! ore bodies consi/ *iefly ( ! r$ oxide ( iron 7hematite7 & occur 9 tr\ghs ( ! /rata1 und]la9 by "s imp]vi\s rock4 ,a !ory held by _m ref]s ! ultimate s\rce ( ! iron to ! igne\s rocks ( ! ,ar*ean4 ,:5 ^! rocks 7 upheav$ & subject$ to wea!r+1 _! iron comp\nds 7 decompos$4 ,_! iron 0 lea*$ out & c>ri$ away to be laid 9 ! ,algonkian wat] bodies 9 b$s ( iron c>bonate & o!r iron comp\nds4 ,dur+ ! lat] ages1 aft] ! ,algonkian /rata _h be5 uplift$ to =m "p ( ! cont95t1 a second conc5tration has tak5 place4 ,desc5d+ und]gr\nd wat]s *>g$ ) oxyg5 h decompos$ ! iron c>bonate & deposit$ ! iron1 9 ! =m ( iron oxide1 9 tr\ghs ( ! /rata :]e _! d[nw>d progress 0 arre/$ by imp]vi\s floors4 ,! pre-,cambrian rocks ( ! ea/]n ,unit$ ,/ates also are ri* 9 iron4 ,9 c]ta9 di/ricts1 z 9 ! ,highl&s ( ,new ,j]sey1 ! black oxide ( iron 7magnetite7 is s abundant 9 b$s & dissem9at$ gra9s t ! ord9>y surveyor's compass is useless4 ,! pre-,cambrian copp] m9es ( ! ,lake ,sup]ior region are among ! ri*e/ on ! globe4 ,9 ! igne\s rocks copp]1 next to iron1 is ! mo/ common ( all ! useful metals1 & x 0 especially abundant 9 ! ,kewe5awan lavas4 ,aft] ! ,kewe5awan 0 uplift$ to =m l&1 p]colat+ wat]s lea*$ out mu* ( ! copp] diffus$ 9 ! lava %eets & deposit$ x )9 /eam blebs z amygdules ( native copp]1 9 cracks & fissures1 & especially z a cem5t1 or matrix1 9 ! int]b$d$ gravels :i* =m$ ! *ief aquif]s ( ! region4 ,! fam\s ,calumet & ,hecla m9e foll[s d[n ! dip ( ! /rata to ! dep? ( ne>ly a mile & works su* an anci5t conglom]ate ^: matrix is pure copp]4 ,illu/ration3 ,fig4 #bfc4 ,successive ,/ages 9 ! ,developm5t ( ! ,ovum to ! ,ga/rula ,/age ,! appe>ance ( life4 ,sometime dur+ ! dim ages prec$+ ! ,cambrian1 :e!r 9 ! ,ar*ean or 9 ! ,algonkian we "k n1 occurr$ "o ( ! mo/ important ev5ts 9 ! hi/ory ( ! e>?4 ,life appe>$ = ! fir/ "t ^u ! planet4 ,geology has no evid5ce :atev] to (f] z to :5ce or h[ life came4 ,all analogies lead u to believe t its appe>ance mu/ h be5 sudd54 ,its e>lie/ =ms are unkn[n1 b analogy sugge/s t z e liv+ creature has develop$ f a s+le cell1 s ! e>lie/ organisms ^u ! globe--! g]ms f :i* all lat] life is suppos$ to h be5 evolv$--7 t9y1 unicellul> masses ( protoplasm1 resembl+ ! amoeba ( to-day 9 ! simplicity ( _! /ructure4 ,su* l[ly =ms 7 de/itute ( any h>d p>ts & c\ld leave no evid5ce ( _! exi/5ce 9 ! record ( ! rocks4 ,& ( _! suppos$ desc5dants we f9d s few traces 9 ! pre-,cambrian /rata t ! fir/ /eps 9 organic evolution mu/ be suppli$ f su* analogies 9 embryology z ! foll[+4 ,! f]tiliz$ ovum1 ! cell ) :i* ea* animal beg9s its life1 gr[s & multiplies by cell division1 & develops into a holl[ globe ( cells call$ ! bla/osph]e4 ,?is /age is succe$$ by ! /age ( ! ga/rula1--an ovoid or cup-%ap$ body ) a d\ble wall ( cells inclos+ a body cavity1 & ) an op5+1 ! primitive m\?4 ,ea* ( ^! e>ly embryological /ages is repres5t$ by liv+ animals1--! undivid$ cell by ! protozoa1 ! bla/osph]e by "s r>e =ms1 & ! ga/rula 9 ! ess5tial /ructure ( ! coel5t]ates1--! subk+dom to :i* ! fre%-wat] hydra & ! corals belong4 ,all =ms ( animal life1 f ! coel5t]ates to ! mammals1 foll[ ! same pa? 9 _! embryological developm5t z f> z ! ga/rula /age1 b "h _! pa?s widely div]ge1 ^? ( ea* subk+dom go+ _! own sep>ate ways4 ,we may inf]1 !re=e1 t dur+ ! pre-,cambrian p]iods organic evolution foll[$ ! l9es ?us dimly trac$4 ,! e>lie/ "o-cell$ protozoa 7 probably succe$$ by _m-cell$ animals ( ! type ( ! bla/osph]e1 & ^! by ga/rula-l organisms4 ,f ! ga/rula type ! high] subdivisions ( animal life probably div]g$1 z sep>ate bran*es f a common trunk4 ,mu* or all ( ?is va/ diff]5tiation 0 accompli%$ be=e ! op5+ ( ! next era2 = all ! subk+doms are repres5t$ 9 ! ,cambrian except ! v]tebrates4 ,evid5ces ( pre-,cambrian life4 ,an indirect evid5ce ( life dur+ ! pre-,cambrian p]iods is f\nd 9 ! abundant & v>i$ fauna ( ! next p]iod2 =1 if ! !ory ( evolution is correct1 ! diff]5tiation ( ! ,cambrian fauna 0 a long process :i* might well h requir$ = its accompli%m5t a l>ge "p ( pre-,cambrian "t4 ,o!r indirect evid5ces are ! pre-,cambrian lime/ones1 iron ores1 & graphite deposits1 s9ce su* m9]als & rocks h be5 =m$ 9 lat] times by ! help ( organisms4 ,if ! c>bonate ( lime ( ! ,algonkian lime/ones & m>bles 0 extract$ f sea wat] by organisms1 z is done at pres5t by corals1 mollusks1 & o!r humble animals & plants1 ! life ( ^? anci5t seas mu/ h be5 abundant4 ,graphite1 a s(t black m9]al compos$ ( c>bon & us$ 9 ! manufacture ( lead p5cils & z a lubricant1 occurs widely 9 ! metamorphic pre-,cambrian rocks4 ,x is kn[n to be produc$ 9 "s cases by ! metamorphism ( coal1 :i* itself is =m$ ( decompos$ vegetal tissues4 ,seams ( graphite may !re=e repres5t accumulations ( vegetal matt] su* z seawe$4 ,b lime/one1 iron ores1 & graphite c be produc$ by *emical processes1 & _! pres5ce 9 ! pre-,cambrian makes x only probable1 & n c]ta91 t life exi/$ at t "t4 ,pre-,cambrian fossils4 ,v r>ely has any cle> trace ( an organism be5 f\nd 9 ! mo/ anci5t *apt]s ( ! geological record1 s _m ( _! leaves h be5 de/roy$ & s f> h _! pages be5 defac$4 ,omitt+ /ructures ^: organic nature has be5 que/ion$1 !re are left to m5tion a t9y sea%ell ( "o ( ! mo/ l[ly types1--a ,disc9a f ! pre-,cambrian rocks ( ! ,colorado ,canyon1--& f ! pre-,cambrian rocks ( ,montana trails ( annelid worms & ca/s ( _! burr[s 9 anci5t bea*es1 & fragm5ts ( ! te/s ( cru/aceans4 ,^! div]se =ms indicate t be=e ! ,algonkian _h clos$1 life 0 abundant & _h widely diff]5tiat$4 ,we may expect t o!r =ms w be discov]$ z ! rocks are closely se>*$4 ,pre-,cambrian geography4 ,our k is f> too meag] to w>rant an attempt to draw ! v>y+ outl9es ( sea & l& dur+ ! ,ar*ean & ,algonkian eras4 ,pre-,cambrian "t probably 0 long] ?an all lat] geological "t d[n to ! pres5t1 z we may inf] f ! va/ ?icknesses ( its rocks & ! uncon=mities :i* "p !m4 ,we "k t dur+ its long p]iods l& masses aga9 & aga9 rose f ! sea1 7 worn l[1 & 7 subm]g$ & cov]$ ) ! wa/e ( o!r l&s4 ,b ! =mations ( sep>at$ regions _c be correlat$ because ( ! abs5ce ( fossils1 & no?+ m c be made out ?an ! deta*$ *apt]s ( local hi/ories1 su* z ! outl9e giv5 ( ! di/rict ab\t ,lake ,sup]ior4 ,! pre-,cambrian rocks %[ no evid5ce ( any =ces !n at "w ^u ! e>? except ! =ces :i* are at "w ^u x n[4 ,! mo/ anci5t s$im5ts kn[n are s l ! s$im5ts n[ be+ laid t we may inf] t !y 7 =m$ "u conditions ess5tially simil> to ^? ( ! pres5t "t4 ,!re is no pro( t ! s&s ( ! pre-,cambrian s&/ones 7 swept by any m p[]ful waves & curr5ts ?an are (f%ore s&s to-day1 or t ! muds ( ! pre-,cambrian %ales settl$ to ! sea floor 9 less quiet wat] ?an su* muds settle 9 at pres5t4 ,! pre-,cambrian l&s 71 no d\bt1 worn by w9d & wea!r1 beat5 by ra91 & furr[$ by /reams z n[1 &1 z n[1 !y front$ ! ocean ) bea*es on :i* waves da%$ & along :i* tidal curr5ts ran4 ,p]haps ! *ief diff]5ce betwe5 ! pre-,cambrian & ! pres5t 0 ! abs5ce ( life ^u ! l&4 ,s f> z we h any k1 no =e/s cov]$ ! m\nta9 sides1 no v]dure c>pet$ ! pla9s1 & no animals liv$ on ! gr\nd or 9 ! air4 ,x is p]mitt$ to ?9k ( ! mo/ anci5t l&s z des]ts ( b>r5 rock & rock wa/e swept by ra9s & tr5*$ by p[]ful /reams4 ,we may !re=e suppose t ! processes ( _! de/ruction w5t on m rapidly ?an at pres5t4 ,,*apt] ,,xvi ,,! ,,cambrian ,! ,paleozoic era4 ,! second volume ( ! geological record1 call$ ! ,paleozoic 7,greek1 palaios1 anci5t2 zoe1 life71 has come d[n to u f> less mutilat$ & defac$ ?an has ! fir/ volume1 :i* conta9s ! traces ( ! mo/ anci5t life ( ! globe4 ,fossils are f> m abundant 9 ! ,paleozoic ?an 9 ! e>li] /rata1 :ile ! s$im5ts 9 :i* !y 7 entomb$ h suff]$ f> less f metamorphism & o!r causes1 & h be5 less widely buri$ f view1 ?an ! /rata ( ! pre-,cambrian gr\ps4 ,by means ( _! fossils we c correlate ! =mations ( widely sep>at$ regions f ! beg9n+ ( ! ,paleozoic on1 & c !re=e trace "s outl9e ( ! hi/ory ( ! cont95ts4 ,paleozoic "t1 al?\gh %ort] ?an ! pre-,cambrian z measur$ by ! ?ickness ( ! /rata1 mu/ /ill be reckon$ 9 millions ( ye>s4 ,dur+ ?is va/ rea* ( "t ! *anges 9 organisms 7 v great4 ,x is accord+ to ! successive /ages 9 ! advance ( life t ! ,paleozoic =mations are arrang$ 9 five sy/ems1--! ,cambrian1 ! ,ordovician1 ! ,silurian1 ! ,devonian1 & ! ,c>bonif]\s4 ,on ! same basis ! fir/ ?ree sy/ems are gr\p$ toge!r z ! old] ,paleozoic1 because !y alike are *>act]iz$ by ! dom9ance ( ! inv]tebrates2 :ile ! la/ two sy/ems are unit$ 9 ! lat] ,paleozoic1 & are *>act]iz$1 ! "o by ! dom9ance ( fi%es1 & ! o!r by ! appe>ance ( amphibians & reptiles4 ,ea* ( ^! sy/ems is _w-wide 9 its di/ribution1 & may be recogniz$ on any cont95t by its own peculi> fauna4 ,! names fir/ giv5 !m 9 ,great ,brita9 h !re=e come into g5]al use1 :ile _! subdivisions1 :i* (t5 _c be correlat$ 9 diff]5t c\ntries & diff]5t regions1 are usually giv5 local names4 ,! fir/ ?ree sy/ems 7 nam$ f ! fact t _! /rata are well display$ 9 ,wales4 ,! ,cambrian c>ries ! ,roman "n ( ,wales1 & ! ,ordovician & ,silurian ! names ( tribes ( anci5t ,britons :i* inhabit$ ! same c\ntry4 ,! ,devonian is nam$ f ! ,engli% c\nty ,devon1 :]e its rocks 7 e>ly /udi$4 ,! ,c>bonif]\s 0 s call$ f ! l>ge am\nt ( coal :i* x 0 f\nd to conta9 9 ,great ,brita9 & cont95tal ,europe4 ,! ,cambrian ,di/ribution ( /rata4 ,! ,cambrian rocks outcrop 9 n>r[ belts ab\t ! pre-,cambrian areas ( ea/]n ,canada & ! ,lake ,sup]ior region1 ! ,adirondacks & ! ,gre5 ,m\nta9s4 ,/rips ( ,cambrian =mations occupy tr\ghs 9 ! pre-,cambrian rocks ( ,new ,engl& & ! m>itime prov9ces ( ,canada2 a long belt bord]s on ! we/ ! cry/all9e rocks ( ! ,blue ,ridge2 & on ! opposite side ( ! cont95t ! ,cambrian reappe>s 9 ! m\nta9s ( ! ,great ,bas9 & ! ,canadian ,rockies4 ,9 ! ,mississippi valley x is expos$ 9 small di/ricts :]e uplift has p]mitt$ ! /ripp+ (f ( y\ng] rocks4 ,al?\gh ! areas ( outcrop are small1 we may inf] t ,cambrian rocks 7 widely deposit$ ov] ! cont95t ( ,nor? ,am]ica4 ,physical geography4 ,! ,cambrian sy/em ( ,nor? ,am]ica comprises ?ree di/9ct s]ies1 ! ,l[] ,cambrian1 ! ,middle ,cambrian1 & ! ,upp] ,cambrian1 ea* ( :i* is *>act]iz$ by its own peculi> fauna4 ,9 sket*+ ! outl9es ( ! cont95t z x 0 at ! beg9n+ ( ! ,paleozoic1 x mu/ be rememb]$ t :]ev] ! ,l[] ,cambrian =mations n[ are f\nd 0 c]ta9ly !n sea bottom1 & :]ev] ! ,l[] ,cambrian are want+1 & ! next =mations re/ directly on pre-,cambrian rocks1 0 probably !n l&4 ,illu/ration3 ,fig4 #bfd4 ,hypo!tical ,map ( ,ea/]n ,nor? ,am]ica at ! ,beg9n+ ( ,cambrian ,"t ,un%ad$ areas1 probable l& ,e>ly ,cambrian geography4 ,9 ?is way we "k t at ! op5+ ( ! ,cambrian two long1 n>r[ m$it]ranean seas /ret*$ f nor? to s\? across ! cont95t4 ,! ea/]n sea ext5d$ f ! ,gulf ( ,/4 ,lawr5ce d[n ! ,*ampla9-,hudson valley & !nce along ! we/]n base ( ! ,blue ,ridge s\? at lea/ to ,alabama4 ,! we/]n sea /ret*$ f ! ,canadian ,rockies ov] ! ,great ,bas9 & at lea/ z f> s\? z ! ,gr& ,canyon ( ! ,colorado 9 ,arizona4 ,betwe5 ^! m$it]raneans lay a great c5tral l& :i* includ$ ! pre-,cambrian ,u-%ap$ area ( ! ,laur5tian p5epla91 & probably ext5d$ s\?w>d to ! latitude ( ,new ,orleans4 ,to ! ea/ lay a l& :i* we may designate z ,appala*ia1 ^: we/]n %ore l9e 0 drawn along ! site ( ! pres5t ,blue ,ridge1 b ^: o!r limits are q unkn[n4 ,! l& ( ,appala*ia mu/ h be5 l>ge1 = x furni%$ a great am\nt ( wa/e dur+ ! entire ,paleozoic era1 & its ea/]n coa/ may possibly h la9 ev5 beyond ! edge ( ! pres5t cont95tal %elf4 ,on ! we/]n side ( ! cont95t a n>r[ l& occupi$ ! site ( ! ,si]ra ,nevada ,m\nta9s4 ,?us1 ev5 at ! beg9n+ ( ! ,paleozoic1 ! cont95tal plateau ( ,nor? ,am]ica _h already be5 left by cru/al movem5ts 9 relief above ! abysses ( ! great oceans on ei!r side4 ,! m$it]raneans :i* lay ^u x 7 %all[1 z _! s$im5ts prove4 ,!y 7 epicont95tal seas2 t is1 !y re/$ ^u 7,greek1 epi7 ! subm]g$ portion ( ! cont95tal plateau4 ,we h no pro( t ! deep ocean ev] occupi$ any "p ( :]e ,nor? ,am]ica n[ is4 ,! ,middle & ,upp] ,cambrian /rata are f\nd toge!r ) ! ,l[] ,cambrian ov] ! area ( bo? ! ea/]n & ! we/]n m$it]raneans1 s t "h ! sea cont9u$ dur+ ! entire p]iod4 ,! s$im5ts ?r\gh\t are ^? ( %oal wat]4 ,co>se cross-b$d$ s&/ones record ! action ( /rong %ift+ curr5ts :i* spread co>se wa/e ne> %ore & w9n[$ x ( f9] /uff4 ,frequ5t ripple m>ks on ! b$d+ planes ( ! /rata prove t ! loose s&s ( ! sea floor 7 ne> en\gh to ! surface to be agitat$ by waves & tidal curr5ts4 ,sun cracks %[ t (t5 ! outgo+ tide expos$ l>ge muddy flats to ! dry+ action ( ! sun4 ,! fossils1 also1 ( ! /rata are ( k9ds relat$ to ^? :i* n[ live 9 %all[ wat]s ne> ! %ore4 ,! s$im5ts :i* ga!r$ 9 ! m$it]ranean seas 7 v ?ick1 rea*+ 9 places ! enorm\s dep? ( t5 ?\s& feet4 ,h5ce ! bottoms ( ^! seas 7 s9k+ tr\ghs1 ev] fill+ ) wa/e f ! adjac5t l& z fa/ z !y subsid$4 ,late ,cambrian geography4 ,! =mations ( ! ,middle & ,upp] ,cambrian are f\nd re/+ uncon=mably on ! pre-,cambrian rocks f ,new ,york we/w>d into ,m9nesota & at v>i\s po9ts 9 ! int]ior1 z 9 ,miss\ri & 9 ,texas4 ,h5ce aft] e>li] ,cambrian "t ! c5tral l& subsid$1 ) mu* ! same effect z if ! ,mississippi valley 7 n[ to l[] gradually1 & ! ,gulf ( ,mexico to spread nor?w>d until x ent]$ ,lake ,sup]ior4 ,! ,cambrian seas transgress$ ! c5tral l& & /rew$ f> & wide beh9d _! advanc+ bea*es ! s$im5ts ( ! lat] ,cambrian ^u an erod$ surface ( pre-,cambrian rocks4 ,! succession ( ! ,cambrian =mations 9 ,nor? ,am]ica records _m m9or oscillations & v>y+ conditions ( physical geography2 yet on ! :ole x tells ( wid5+ seas & l[]+ l&s4 ,basal conglom]ates & co>se s&/ones :i* mu/ h be5 laid ne> %ore are succe$$ by %aly s&/ones1 s&y %ales1 & %ales4 ,t[>d ! top ( ! s]ies heavy b$s ( lime/one1 ext5d+ f ! ,blue ,ridge to ,miss\ri1 speak ( cle> wat]1 & ei!r ( m di/ant %ores or ( neighbor+ l&s :i* 7 worn or sunk s l[ t = ! mo/ "p _! wa/e 0 c>ri$ to ! sea 9 solution4 ,9 brief1 ! ,cambrian 0 a p]iod ( subm]g5ce4 ,x began ) ! l>g] "p ( ,nor? ,am]ica em]g$ z great l& masses4 ,x clos$ ) mo/ ( ! int]ior ( ! cont95tal plateau cov]$ ) a %all[ sea4 ,! ,life ( ! ,cambrian ,p]iod ,x is n[ = ! fir/ "t t we f9d pres]v$ 9 ! (f%ore deposits ( ! ,cambrian seas en\gh rema9s ( animal life to be prop]ly call$ a fauna4 ,d\btless ^! rema9s are only ! mo/ fragm5t>y repres5tation ( ! life ( ! "t1 = ! ,cambrian rocks are v old & h be5 widely metamorphos$4 ,yet ! five hundr$ & m species already discov]$ embrace all ! lead+ types ( inv]tebrate life1 & are s v>i$ t we mu/ believe t _! l9es ( desc5t /ret* f> back into ! pre-,cambrian pa/4 ,plants4 ,no rema9s ( plants h be5 f\nd 9 ,cambrian /rata1 except "s d\btful m>k+s1 z ( seawe$4 ,sponges4 ,! sponges1 ! l[e/ ( ! multicellul> animals1 7 repres5t$ by sev]al ord]s4 ,_! fossils are recogniz$ by ! silice\s spicules1 :i*1 z 9 mod]n sponges1 ei!r 7 scatt]$ ?r\gh a mass ( horny fib]s or 7 connect$ 9 a fl9ty framework4 ,illu/ration3 ,fig4 #bfe4 ,sponge ,spicules z se5 9 ,fl9t "u ! ,microscope ,coel5t]ates4 ,?is subk+dom includes two classes ( int]e/ to ! geologi/1--! ,hydrozoa1 su* z ! fre%-wat] hydra & ! jellyfi%1 & ! corals4 ,bo? classes exi/$ 9 ! ,cambrian4 ,illu/ration3 ,fig4 #bff4 ,graptolites ,! ,hydrozoa 7 repres5t$ n only by jellyfi% b also by ! graptolite1 :i* takes its "n f a fanci$ resemblance ( "s ( its =ms to a quill p54 ,x 0 a composite animal ) a horny framework1 ! individuals ( ! colony liv+ 9 cells /rung on "o or bo? sides along a holl[ /em1 & communicat+ by means ( a common fle% 9 ?is c5tral tube4 ,"s graptolites 7 /raight1 & "s curv$ or spiral2 "s 7 s+le /emm$1 & o!rs consi/$ ( sev]al radial /ems unit$4 ,graptolites occur b r>ely 9 ! ,upp] ,cambrian4 ,9 ! ,ordovician & ,silurian !y are v pl5tiful1 & at ! close ( ! ,silurian !y pass out ( exi/5ce1 nev] to return4 ,corals are v r>ely f\nd 9 ! ,cambrian1 & ! description ( _! primitive types is po/pon$ to lat] *apt]s treat+ ( p]iods :5 !y became m num]\s4 ,e*9od]ms4 ,?is subk+dom comprises at pres5t su* famili> =ms z ! cr9oid1 ! />fi%1 & ! sea ur*94 ,! /ructure ( e*9od]ms is radiate4 ,_! integum5t is h>d5$ ) plates or p>ticles ( c>bonate ( lime4 ,illu/ration3 ,fig4 #bfg4 ,cy/oids1 "o %[+ ,two ,rudim5t>y ,arms ,( ! free e*9od]ms1 su* z ! />fi% & ! sea ur*91 ! =m] has be5 f\nd 9 ! ,cambrian rocks ( ,europe1 b nei!r h s f> be5 discov]$ 9 ! /rata ( ?is p]iod 9 ,nor? ,am]ica4 ,! /emm$ & l[] division ( ! e*9od]ms 0 repres5t$ by a primitive type1 ! cy/oid1 s call$ f its saclike =m1 ,a small globul> or ovate calyx ( calc>e\s plates1 ) an ap]ture at ! top = ! m\?1 inclos$ ! body ( ! animal1 & 0 atta*$ to ! sea bottom by a %ort flexible /alk consi/+ ( disks ( c>bonate ( lime held toge!r by a c5tral ligam5t4 ,ar?ropods4 ,^! segm5t$ animals ) jo9t$ feet1 z _! "n sugge/s1 may be divid$ 9 a g5]al way into wat] brea!rs & air brea!rs4 ,! fir/-nam$ & l[] division comprises ! class ( ! ,cru/acea1--ar?ropods protect$ by a h>d ext]ior skeleton1 or cru/1--( :i* crabs1 crayfi%1 & lob/]s are famili> examples4 ,! high] division1 t ( ! air brea!rs1 includes ! foll[+ classes3 spid]s1 scorpions1 c5tip$es1 & insects4 ,! trilobite4 ,! aquatic ar?ropods1 ! ,cru/acea1 culm9at$ be=e ! air brea!rs2 & :ile none ( ! latt] are f\nd 9 ! ,cambrian1 ! =m] 7 ! dom9ant life ( ! "t 9 numb]s1 9 size1 & 9 ! v>iety ( _! =ms4 ,! lead+ cru/acean type is ! trilobite1 :i* takes its "n f ! ?ree lobes into :i* its %ell is divid$ longitud9ally4 ,!re are also ?ree cross divisions1--! head %ield1 ! tail %ield1 & betwe5 ! two ! ?orax1 consi/+ ( a numb] ( di/9ct & unconsolidat$ segm5ts4 ,! head %ield c>ries a pair ( l>ge1 cresc5tic1 comp\nd eyes1 l ^? ( ! insect4 ,! eye v>ies greatly 9 ! numb] ( its l5ses1 rang+ f f\rte5 9 "s species to fifte5 ?\s& 9 o!rs4 ,figure #bfh1 ,c1 is a re/oration ( ! trilobite1 & %[s ! app5dages1 :i* are f\nd pres]v$ only 9 ! r>e/ cases4 ,illu/ration3 ,fig4 #bfh4 ,trilobites ,a1 a ,cambrian species2 ,b1 a ,devonian species %[+ eyes2 ,c1 re/oration ( an ,ordovician species ,dur+ ! long ages ( ! ,cambrian ! trilobite v>i$ greatly4 ,aga9 & aga9 new species & g5]a appe>$1 :ile ! old] types became ext9ct4 ,= ?is reason & because ( _! abundance1 trilobites are us$ 9 ! classification ( ! ,cambrian sy/em4 ,! ,l[] ,cambrian is *>act]iz$ by ! pres5ce ( a trilobitic fauna 9 :i* ! g5us ,ol5ellus is pr$om9ant4 ,?is1 ! ,ol5ellus ,zone1 is "o ( ! mo/ important plat=ms 9 ! entire geological s]ies2 =1 ! _w ov]1 x m>ks ! beg9n+ ( ,paleozoic "t1 :ile all und]ly+ /rata are classifi$ z pre-,cambrian4 ,! ,middle ,cambrian is m>k$ by ! g5us ,p>adoxides1 & ! ,upp] ,cambrian by ! g5us ,ol5us4 ,"s ( ! ,cambrian trilobites 7 giants1 measur+ z mu* z two feet long1 :ile o!rs 7 ! smalle/ ( _! k9d1 a fraction ( an in* 9 l5g?4 ,ano!r type ( cru/acean :i* liv$ 9 ! ,cambrian & ^: ord] is /ill liv+ is illu/rat$ 9 ,figure #bfi4 ,illu/ration3 ,fig4 #bfi4 ,a ,phyllopod ,worms4 ,trails & burr[s ( worms h be5 left on ! sea bea*es & mud flats ( all geological times f ! ,algonkian to ! pres5t4 ,bra*iopods4 ,^! s(t-bodi$ animals1 ) bivalve %ells & two int]ior armlike processes :i* s]v$ = brea?+1 appe>$ 9 ! ,algonkian1 & _h n[ become v abundant4 ,! two valves ( ! bra*iopod %ell are unequal 9 size1 & 9 ea* valve a l9e drawn f ! beak to ! base divides ! valve into two equal p>ts 7,fig4 #bgj74 ,x may ?us be told f ! pelecypod mollusk1 su* z ! clam1 ^: two valves are n f> f equal 9 size1 ea* be+ divid$ into unequal p>ts by a l9e dropp$ f ! beak 7,fig4#bgb74 ,illu/ration3 ,fig4 #bgj4 ,a ,cambrian ,articulate ,bra*iopod1 ,or?is ,illu/ration3 ,fig4 #bga4 ,cambrian ,in>ticulate ,bra*iopods ,a1 ,l+ulella2 ,b1 ,disc9a ,bra*iopods include two ord]s4 ,9 ! mo/ primitive ord]--t ( ! in>ticulate bra*iopods--! two valves are held toge!r only by muscles ( ! animal1 & ! %ell is horny or is compos$ ( phosphate ( lime4 ,! ,disc9a1 :i* began 9 ! ,algonkian1 is ( ?is type1 z is also ! ,l+ulella ( ! ,cambrian 7,fig4 #bga74 ,bo? ( ^! g5]a h liv$ on dur+ ! millions ( ye>s ( geological "t s9ce _! introduction1 h&+ d[n f g5]ation to g5]ation ) h>dly any *ange to _! desc5dants n[ liv+ (f our %ores ! *>act]s impress$ ^u !m at ! beg9n+4 ,! m highly organiz$ articulate bra*iopods h valves ( c>bonate ( lime m securely jo9$ by a h+e ) tee? & sockets 7,fig4 #bgj74 ,9 ! ,cambrian ! in>ticulates pr$om9ate1 ?\gh ! articulates gr[ common t[>d ! end ( ! p]iod4 ,mollusks4 ,! ?ree *ief classes ( mollusks--! pelecypods 7repres5t$ by ! oy/] & clam ( to-day71 ! ga/ropods 7repres5t$ n[ by snails1 con*es1 & p]iw9kles71 & ! cephalopods 7su* z ! nautilus1 cuttlefi%1 & squids7--7 all repres5t$ 9 ! ,cambrian1 al?\gh v sp>+ly4 ,illu/ration3 ,fig4 #bgb4 ,a ,cambrian ,pelecypod ,illu/ration3 ,fig4 #bgc4 ,ga/ropods ,pt]opods1 a subord] ( ! ga/ropods1 appe>$ 9 ?is age4 ,_! pap]y %ells ( c>bonate ( lime are f\nd 9 great numb]s f ?is "t on4 ,illu/ration3 ,fig4 #bgd4 ,cambrian ,pt]opods ,cephalopods1 ! mo/ highly organiz$ ( ! mollusks1 />t$ into exi/5ce1 s f> z ! record %[s1 t[>d1 ! end ( ! ,cambrian1 ) ! long ext9ct ,or?oc]as 7/raigh?orn7 & ! alli$ g5]a ( its family4 ,! ,or?oc]as _h a long1 /raight1 & tap]+ %ell1 divid$ by cross p>titions into *amb]s4 ,! animal liv$ 9 ! body *amb] at ! l>g] end1 & wall$ (f ! o!r *amb]s f x 9 succession dur+ ! gr[? ( ! %ell4 ,a c5tral tube1 ! siphuncle 7s1 ,fig4 #bge1 ,b71 pass$ ?r\gh f ! body *amb] to ! clos$ tip ( ! cone4 ,illu/ration3 ,fig4 #bge4 ,or?oc]as ,a1 fossil2 ,b1 re/oration ,! sea%ells1 bo? bra*iopods & mollusks1 are 9 "s respects ! mo/ important to ! geologi/ ( all fossils4 ,!y h be5 s num]\s1 s widely di/ribut$1 & s well pres]v$ because ( _! durable %ells & _! /ation 9 gr[+ s$im5ts1 t bett] ?an any o!r gr\p ( organisms !y c be us$ to correlate ! /rata ( diff]5t regions & to m>k by _! sl[ *anges ! advance ( geological "t4 ,climate4 ,! life ( ,cambrian times 9 diff]5t c\ntries conta9s no sugge/ion ( any m>k$ climatic zones1 & z 9 lat] p]iods a w>m climate probably rea*$ to ! pol> regions4 ,,*apt] ,,xvii ,,! ,,ordovician#b ,,& ,,silurian #b ,(t5 kn[n z ! ,l[] ,silurian4 ,! ,ordovician ,9 ,nor? ,am]ica ! ,ordovician rocks lie con=mably on ! ,cambrian4 ,! two p]iods1 !re=e1 7 n p>t$ by any de=mation1 ei!r ( m\nta9 mak+ or ( cont95tal uplift4 ,! g5]al subm]g5ce :i* m>k$ ! ,cambrian cont9u$ into ! succe$+ p]iod ) little int]ruption4 ,subdivisions & di/ribution ( /rata4 ,! ,ordovician s]ies1 z !y h be5 made out 9 ,new ,york1 are giv5 = ref]5ce 9 ! foll[+ table1 ) ! rocks ( :i* !y are *iefly compos$3 #e ,hudson 44444 %ales #d ,utica 44444 %ales #c ,tr5ton 44444 lime/ones #b ,*azy 44444 lime/ones #a ,calcif]\s 44444 s&y lime/ones ,^! m>9e =mations ( ! ,ordovician outcrop ab\t ! ,cambrian & pre-,cambrian areas1 &1 z bor+s %[1 ext5d f> & wide ov] ! int]ior ( ! cont95t b5ea? m rec5t /rata4 ,! ,ordovician sea /ret*$ f ,appala*ia across ! ,mississippi valley4 ,x seems to h ext5d$ to ,cali=nia1 al?\gh brok5 probably by sev]al m\nta9\s isl&s 9 ! we/4 ,physical geography4 ,! physical hi/ory ( ! p]iod is record$ 9 ! succession ( its =mations4 ,! s&/ones ( ! ,upp] ,cambrian1 z we h le>n$1 tell ( a transgress+ sea :i* gradually came to occupy ! ,mississippi valley & ! int]ior ( ,nor? ,am]ica4 ,! lime/ones ( ! e>ly & middle ,ordovician %[ t n[ ! %ore _h become remote & ! l&s _h become m l[4 ,! wat]s n[ _h cle>$4 ,colonies ( bra*iopods & o!r lime-secret+ animals occupi$ ! sea bottom1 & _! debris mantl$ x ) %eets ( limy ooze4 ,! s&y lime/ones ( ! ,calcif]\s record ! transition /age f ! ,cambrian :5 "s s& 0 /ill br\ght 9 f %ore4 ,! highly fossilif]\s lime/ones ( ! ,tr5ton tell ( cle> wat] & abundant life4 ,we ne$ n reg>d ?is epicont95tal sea z deep4 ,no abysmal deposits h be5 f\nd1 & ! lime/ones ( ! p]iod are ^? :i* w\ld be laid 9 cle>1 w>m wat] ( mod]ate dep? l t ( mod]n coral seas4 ,illu/ration3 ,fig4 #bgf4 ,hypo!tical ,map ( ! ,ea/]n ,unit$ ,/ates 9 ,ordovician ,"t ,%ad$ areas1 probable sea2 brok5 l9es1 approximate %ore l9es ,! %ales ( ! ,utica & ,hudson %[ t ! wat]s ( ! sea n[ became cl\d$ ) mud wa%$ 9 f l&4 ,ei!r ! l& 0 gradually uplift$1 or p]haps !re _h arriv$ "o ( ^? p]iodic crises :i*1 z we may imag9e1 h tak5 place :5ev] ! cru/ ( ! %r9k+ e>? has sl[ly giv5 way ov] its great depressions1 & ! ocean has )drawn its wat]s into deep5+ abysses4 ,! l& 0 ?us left relatively high] & bord]$ ) new coa/al pla9s4 ,! epicont95tal sea 0 %oal$ & n>r[$1 & muds 7 wa%$ 9 f ! adjac5t l&s4 ,! ,taconic de=mation4 ,! ,ordovician 0 clos$ by a de=mation ^: ext5t & sev]ity are n yet kn[n4 ,f ! ,/4 ,lawr5ce ,riv] to ,new ,york ,bay1 along ! nor?we/]n & we/]n bord] ( ,new ,engl&1 lies a belt ( ,cambrian-,ordovician rocks m ?an a mile 9 total ?ickness1 :i* accumulat$ dur+ ! long ages ( ^? p]iods 9 a gradually subsid+ tr\gh betwe5 ! ,adirondacks & a pre-,cambrian range ly+ we/ ( ! ,connecticut ,riv]4 ,b s9ce _! deposition ^! anci5t s$im5ts h be5 crumpl$ & cru%$1 brok5 ) great faults1 & ext5sively metamorphos$4 ,! lime/ones h recry/alliz$ into m>bles1 among !m ! fam\s m>bles ( ,v]mont2 ! ,cambrian s&/ones h become qu>tzites1 & ! ,hudson %ale has be5 *ang$ to a s*i/ expos$ on ,manhattan ,isl& & nor?w>d4 ,9 "p ^! *anges occurr$ at ! close ( ! ,ordovician1 = 9 sev]al places b$s ( ,silurian age re/ uncon=mably on ! upturn$ ,ordovician /rata2 b rec5t inve/igations h made x probable t ! cru/al movem5ts recurr$ at lat] times1 & x 0 p]haps 9 ! ,devonian & at ! close ( ! ,c>bonif]\s t ! great] "p ( ! de=mation & metamorphism 0 accompli%$4 ,z a result ( ^! movem5ts1--p]haps sev]al times repeat$1--a great m\nta9 range 0 upridg$1 :i* has be5 long s9ce level$ by erosion1 b ^: roots are n[ visible 9 ! ,taconic ,m\nta9s ( we/]n ,new ,engl&4 ,! ,c9c9nati anticl9e4 ,ov] an oval area 9 ,ohio1 ,indiana1 & ,k5tucky1 ^: long] axis ext5ds f nor? to s\? ?r\gh ,c9c9nati1 ! ,ordovician /rata rise 9 a v l[1 broad swell1 call$ ! ,c9c9nati anticl9e4 ,! ,silurian & ,devonian /rata ?9 out z !y approa* ?is area & seem nev] to h deposit$ ^u x4 ,we may reg>d x1 !re=e1 z an isl& upw>p$ f ! sea at ! close ( ! ,ordovician or %ortly aft]4 ,petroleum & natural gas4 ,^! valuable illum9ants & fuels are consid]$ "h because1 al?\gh !y are f\nd 9 traces 9 old] /rata1 x is 9 ! ,ordovician t !y occur = ! fir/ "t 9 l>ge quantities4 ,!y range ?r\gh\t lat] =mations d[n to ! mo/ rec5t4 ,illu/ration3 ,fig4 #bgg4 ,diagram ,illu/rat+ ! ,conditions ( ,accumulation ( ,oil & ,gas a1 s\rce2 b1 res]voir2 c1 cov]4 ,:at w\ld be ! result ( bor+ to ! res]voir rock at d8 at d8 at d8 ,! oil horizons ( ,cali=nia & ,texas are ,t]ti>y2 ^? ( ,colorado1 ,cretace\s2 ^? ( ,we/ ,virg9ia1 ,c>bonif]\s2 ^? ( ,p5nsylvania1 ,k5tucky1 & ,canada1 ,devonian2 & ! l>ge field ( ,ohio & ,indiana belongs to ! ,ordovician & high] sy/ems4 ,petroleum & natural gas1 :]ev] f\nd1 h probably orig9at$ f ! decay ( organic matt] :5 buri$ 9 s$im5t>y deposits1 j z at pres5t 9 swampy places ! hydrog5 & c>bon ( decay+ vegetation comb9e to =m m>% gas4 ,! light & heat ( ^! hydroc>bons we may ?9k (1 !re=e1 z a gift to ! civiliz$ life ( our race f ! humble organisms1 bo? animal & vegetable1 ( ! remote pa/1 ^: rema9s 7 entomb$ 9 ! s$im5ts ( ! ,ordovician & lat] geological ages4 ,petroleum is v widely dissem9at$ ?r\gh\t ! /ratifi$ rocks4 ,c]ta9 lime/ones are visibly greasy ) x1 & o!rs give (f its *>act]i/ic fetid odor :5 /ruck ) a hamm]4 ,_m %ales are bitum9\s1 & "s are s highly *>g$ t small flakes may be light$ l tap]s1 & sev]al gallons ( oil to ! ton may be obta9$ by di/illation4 ,b oil & gas are f\nd 9 pay+ quantities only :5 c]ta9 conditions meet3 #a4 ,a s\rce bel[1 usually a bitum9\s %ale1 f ^: organic matt] !y h be5 d]iv$ by sl[ *ange4 #b4 ,a res]voir above1 9 :i* !y h ga!r$4 ,?is is ei!r a por\s s&/one or a por\s or crevic$ lime/one4 #c4 ,oil & gas are light] ?an wat]1 & are usually "u pressure ow+ to artesian wat]4 ,h5ce1 9 ord] to hold !m f escap+ to ! surface1 ! res]voir mu/ h ! %ape ( an anticl9e1 dome1 or l5s4 #d4 ,x mu/ also h an imp]vi\s cov]1 usually a %ale4 ,9 ^! res]voirs gas is "u a pressure :i* is (t5 enorm\s1 rea*+ 9 extreme cases z high z a ?\s& five hundr$ p\nds to ! squ>e in*4 ,:5 tapp$ x ru%es out ) a deaf5+ ro>1 sometimes fl++ ! heavy drill high 9 air4 ,9 acc\nt+ = ?is pressure we mu/ rememb] t ! gas has be5 compress$ )9 ! pores ( ! res]voir rock by artesian wat]1 & 9 "s cases also by its own expansive =ce4 ,x is n uncommon = artesian wat] to rise 9 wells aft] ! exhau/ion ( gas & oil4 ,life ( ! ,ordovician ,dur+ ! ages ( ! ,ordovician1 life made great advances4 ,types already pres5t bran*$ widely into new g5]a & species1 & new & high] types appe>$4 ,sponges cont9u$ f ! ,cambrian4 ,graptolites n[ rea*$ _! climax4 ,illu/ration3 ,fig4 #bgh4 ,/romatopora ,/romatopora--colonies ( m9ute hydrozoans alli$ to corals--grew 9 places on ! sea floor1 secret+ /ony masses compos$ ( ?91 close1 conc5tric lay]s1 connect$ by v]tical rods4 ,! ,/romatopora are among ! *ief lime/one build]s ( ! ,silurian & ,devonian p]iods4 ,corals develop$ along sev]al di/9ct l9es1 l mod]n corals !y secret$ a calc>e\s framework1 9 ^: out] portions ! polyps liv$4 ,9 ! ,ordovician1 corals 7 repres5t$ *iefly by ! family ( ! ,*tetes1 all species ( :i* are long s9ce ext9ct4 ,! description ( o!r types ( corals w be giv5 "u ! ,silurian1 :]e !y fir/ became abundant4 ,e*9od]ms4 ,! cy/oid rea*es its climax1 b !re appe> n[ two high] types ( e*9od]ms1--! cr9oid & ! />fi%4 ,! cr9oid1 nam$ f its resemblance to ! lily1 is l ! cy/oid 9 _m respects1 b has a long] /em & supports a cr[n ( plumose arms4 ,/irr+ ! wat] ) ^! arms1 x creates curr5ts by :i* p>ticles ( food are waft$ to its m\?4 ,cr9oids are r>e at ! pres5t "t1 b !y grew 9 ! greate/ pr(usion 9 ! w>m ,ordovician seas & = long ages !reaft]4 ,9 _m places ! sea floor 0 beautiful ) ^! graceful1 fl[]like =ms1 z ) fields ( long-/emm$ lilies4 ,( ! high]1 free-mov+ classes ( ! e*9od]ms1 />fi% are m num]\s ?an 9 ! ,cambrian1 & sea ur*9s make _! appe>ance 9 r>e ar*aic =ms4 ,illu/ration3 ,fig4 #bgi4 ,cr9oid1 a ,jurassic ,species ,illu/ration3 ,fig4 #bhj4 ,an ,ordovician ,/>fi% ,illu/ration3 ,fig4 #bha4 ,an ,ordovician ,sea ,ur*9 ,illu/ration3 ,fig4 #bhb4 ,eurypt]us ,cru/aceans4 ,trilobites n[ rea* _! greate/ developm5t & m ?an elev5 hundr$ species h be5 describ$ f ! rocks ( ?is p]iod4 ,x is int]e/+ to note t 9 _m species ! segm5ts ( ! ?orax h n[ come to be s %ap$ t !y move freely on "o ano!r4 ,unlike _! ,cambrian ance/ors1 _m ( ! ,ordovician trilobites c\ld roll !mselves into balls at ! approa* ( dang]4 ,x is 9 ?is attitude1 tak5 at ! approa* ( dea?1 t trilobites are (t5 f\nd 9 ! ,ordovician & lat] rocks4 ,! gigantic cru/aceans call$ ! eurypt]ids 7 also pres5t 9 ?is p]iod 7,fig4 #bhb74 ,! ar?ropods _h n[ seiz$ ^u ! l&4 ,c5tip$es & insects ( a l[ type1 ! e>lie/ kn[n l& animals1 h be5 discov]$ 9 /rata ( ?is sy/em4 ,illu/ration3 ,fig4 #bhc4 ,a ,bryozoan ,bryozoans4 ,no fossils are m common 9 ! lime/ones ( ! "t ?an ! small bran*+ /ems & lacelike mats ( ! bryozoans1--! skeletons ( colonies ( a m9ute animal alli$ 9 /ructure to ! bra*iopod4 ,illu/ration3 ,fig4 #bhd4 ,ordovician ,bra*iopods ,bra*iopods4 ,^! multipli$ greatly1 & 9 places _! %ells =m$ ?ick b$s ( coqu9a4 ,!y /ill greatly surpass$ ! mollusks 9 numb]s4 ,cephalopods4 ,among ! mollusks we mu/ note ! evolution ( ! cephalopods4 ,! primitive /raight ,or?oc]as has n[ become abundant4 ,b 9 addition to ?is ance/ral type !re appe>s a succession ( =ms m & m curv$ & closely coil$1 z illu/rat$ 9 ,figure #bhe4 ,! nautilus1 :i* began its c\rse 9 ?is p]iod1 crawls on ! bottom ( our pres5t seas4 ,illu/ration3 ,fig4 #bhe4 ,a1 ,cyrtoc]as2 ,b1 ,tro*oc]as2 ,c1 ,lituites ,illu/ration3 ,fig4 #bhf4 ,nautilus ,v]tebrates4 ,! mo/ important record ( ! ,ordovician is t ( ! appe>ance ( a new & high] type1 ) possibilities ( developm5t ly+ hidd5 9 its /ructure t ! mollusk & ! insect c\ld nev] hope to rea*4 ,scales & plates ( m9ute fi%es f\nd 9 ! ,ordovician rocks ne> ,canon ,city1 ,colorado1 %[ t ! humble/ ( ! v]tebrates _h already made its appe>ance4 ,b x is probable t v]tebrates _h be5 on ! e>? = ages be=e ?is 9 l[ly types1 :i*1 be+ de/itute ( h>d p>ts1 w\ld leave no record4 ,! ,silurian ,! n>r[+ ( ! seas & ! em]g5ce ( ! l&s :i* *>act]iz$ ! clos+ epo* ( ! ,ordovician 9 ea/]n ,nor? ,am]ica cont9ue into ! succe$+ p]iod ( ! ,silurian4 ,new species appe> & _m old species n[ become ext9ct4 ,! ,appala*ian region4 ,:]e ! ,silurian sy/em is mo/ fully develop$1 f ,new ,york s\?w>d along ! ,appala*ian ,m\nta9s1 x comprises f\r s]ies3 #d ,sal9a 44444 %ales1 impure lime/ones1 gypsum1 salt #c ,niag>a 44444 *iefly lime/ones #b ,cl9ton 44444 s&/ones1 %ales1 ) "s lime/ones #a ,m$9a 44444 conglom]ates1 s&/ones ,! rocks ( ^! s]ies are %all[-wat] deposits & rea* ! total ?ickness ( "s five ?\s& feet4 ,evid5tly !y 7 laid ov] an area :i* 0 on ! :ole gradually subsid+1 al?\gh ) v>i\s g5tle oscillations :i* are record$ 9 ! diff]5t =mations4 ,! co>se s&s ( ! heavy ,m$9a =mations record a p]iod ( uplift ( ! oldl& ( ,appala*ia1 :5 erosion w5t on rapidly & co>se wa/e 9 abundance 0 br\ght d[n f ! hills by swift /reams & spread by ! waves 9 wide1 s&y flats4 ,z ! l&s 7 worn l[] ! wa/e became f9]1 & dur+ an epo* ( transition--! ,cl9ton--!re 7 deposit$ v>i\s =mations ( s&/ones1 %ales1 & lime/ones4 ,! ,niag>a lime/ones te/ify to a long epo* ( repose1 :5 l[-ly+ l&s s5t little wa/e d[n to ! sea4 ,! gypsum & salt deposits ( ! ,sal9a %[ t t[>d ! close ( ! ,silurian p]iod a slight oscillation br\ght ! sea floor ne>] to ! surface1 & at ! nor? cut (f ext5sive tracts f ! int]ior sea4 ,9 ^! wide lagoons1 :i* n[ & !n rega9$ access to ! op5 sea & obta9$ new supplies ( salt wat]1 b$s ( salt & gypsum 7 deposit$ z ! br9y wat]s became conc5trat$ by evaporation "u a des]t climate4 ,along ) ^! b$s !re 7 also laid %ales & impure lime/ones4 ,9 ,new ,york ! salt pans ( ! ,sal9a ext5d$ ov] an area "o hundr$ & fifty miles long f ea/ to we/ & sixty miles wide1 & simil> salt m>%es occurr$ z f> we/ z ,clevel&1 ,ohio1 & ,god]i* on ,lake ,huron4 ,at ,i?aca1 ,new ,york1 ! s]ies is fifte5 hundr$ feet ?ick1 & is buri$ b5ea? an equal ?ickness ( lat] /rata4 ,x includes two hundr$ & fifty feet ( solid salt1 9 sev]al di/9ct b$s1 ea* seal$ )9 ! %ales ( ! s]ies4 ,w\ld y expect to f9d anci5t b$s ( rock salt inclos$ 9 b$s ( p]vi\s s&/one8 ,! salt b$s ( ! ,sal9a are ( great value4 ,!y are rea*$ by well bor+s1 & _! br9es are evaporat$ by sol> heat & by boil+4 ,! rock salt is also m9$ f deep %afts4 ,simil> deposits ( salt1 =m$ "u l conditions1 occur 9 ! rocks ( lat] sy/ems d[n to ! pres5t4 ,! salt b$s ( ,texas are ,p]mian1 ^? ( ,kansas are ,p]mian1 & ^? ( ,l\isiana are ,t]ti>y4 ,! ,mississippi valley4 ,! heavy ne>-%ore =mations ( ! ,silurian 9 ! ,appala*ian region ?9 out t[>d ! we/4 ,! ,m$9a & ! ,cl9ton s&/ones are n f\nd we/ ( ,ohio1 :]e ! fir/ passes into a %ale & ! second into a lime/one4 ,! ,niag>a lime/one1 h[ev]1 spreads f ! ,hudson ,riv] to beyond ! ,mississippi1 a di/ance ( m ?an a ?\s& miles4 ,dur+ ! ,silurian p]iod ! ,mississippi valley region 0 cov]$ ) a quiet1 %all[1 lime/one-mak+ sea1 :i* receiv$ little wa/e f ! l[ l&s :i* bord]$ x4 ,! probable di/ribution ( l& & sea 9 ea/]n ,nor? ,am]ica & we/]n ,europe is %[n 9 ,figure #bhg4 ,! fauna ( ! int]ior region & ( ea/]n ,canada are closely alli$ ) t ( we/]n ,europe1 & sev]al species are id5tical4 ,we c h>dly acc\nt = ?is except by a %all[-wat] connection betwe5 ! two anci5t epicont95tal seas4 ,x 0 p]haps along ! coa/al %elves ( a nor!rn l& connect+ ,am]ica & ,europe by way ( ,gre5l& & ,icel& t ! migration took place1 s t ! same species came to live 9 ,i[a & 9 ,sw$54 ,illu/ration3 ,fig4 #bhg4 ,hypo!tical ,map ( ,p>ts ( ,nor? ,am]ica & ,europe 9 ,silurian ,"t4 ,%ad$ areas1 probably seas2 brok5 l9es1 approximate %ore l9es ,! we/]n ,unit$ ,/ates4 ,s little is f\nd ( ! rocks ( ! sy/em we/ ( ! ,miss\ri ,riv] t x is q probable t ! we/]n "p ( ! ,unit$ ,/ates _h = ! mo/ "p em]g$ f ! sea at ! close ( ! ,ordovician & rema9$ l& dur+ ! ,silurian4 ,at ! same "t ! we/]n l& 0 p]haps connect$ ) ! ea/]n l& ( ,appala*ia across ,arkansas & ,mississippi2 = t[>d ! s\? ! ,silurian s$im5ts indicate an approa* to %ore4 ,life ( ! ,silurian ,9 ?is brief sket* x is q impossible to relate ! _m *anges ( species & g5]a dur+ ! ,silurian4 ,corals4 ,"s ( ! m common types are famili>ly kn[n z cup corals1 honeycomb corals1 & *a9 corals4 ,9 ! cup corals ! mo/ important feature is ! developm5t ( radiat+ v]tical p>titions1 or septa1 9 ! cell ( ! polyp4 ,"s ( ! cup corals grew 9 hemisph]ical colonies 7,fig4 #bhh71 :ile _m 7 sep>ate individuals 7,fig4 #bhi71 build+ a s+le conical1 or horn-%ap$ cell1 :i* sometimes rea*$ ! extreme size ( a foot 9 l5g? & two or ?ree in*es 9 diamet]4 ,illu/ration3 ,fig4 #bhh4 ,a ,comp\nd ,cup ,coral ,illu/ration3 ,fig4 #bhi4 ,a ,simple ,cup ,coral ,illu/ration3 ,fig4 #bij4 ,honeycomb ,corals ,illu/ration3 ,fig4 #bia4 ,a ,*a9 ,coral ,illu/ration3 ,fig4 #bib4 ,a ,syr+opora ,coral ,honeycomb corals consi/ ( masses ( small1 close-set prismatic cells1 ea* cross$ by horizontal p>titions1 or tabul1 :ile ! septa are rudim5t>y1 be+ repres5t$ by fa9tly project+ ridges or r[s ( sp9es4 ,*a9 corals are also m>k$ by tabul4 ,_! cells =m elliptical tubes1 t\*+ ea* o!r at ! edges1 & appe>+ 9 cross section l ! l9ks ( a *a94 ,!y became ext9ct at ! end ( ! ,silurian4 ,! corals ( ! ,syr+opora family are simil> 9 /ructure to *a9 corals1 b ! tubul> columns are connect$ only 9 places4 ,illu/ration3 ,fig4 #bic4 ,a ,bla/oid3 ,a1 side view1 %[+ portion ( ! /em2 ,b1 summit ( calyx 7species ,c>bonif]\s7 ,illu/ration3 ,fig4 #bid4 ,a ,silurian ,scorpion ,to ! e*9od]ms !re is n[ add$ ! bla/oid 7bud-%ap$74 ,! bla/oid is /emm$ & armless1 & its globul> head or calyx1 ) its five petal-l divisions1 resembles a fl[] bud4 ,! bla/oids became m abundant 9 ! ,devonian1 culm9at$ 9 ! ,c>bonif]\s1 & disappe>$ at ! end ( ! ,paleozoic4 ,! great eurypt]ids--"s ( :i* 7 five or six feet 9 l5g?--& ! cephalopods 7 /ill ma/]s ( ! seas4 ,fi%es 7 z yet few & small2 trilobites & graptolites _h n[ pass$ _! prime & _h dim9i%$ greatly 9 numb]s4 ,scorpions are f\nd 9 ?is p]iod bo? 9 ,europe & 9 ,am]ica4 ,! lime/one-mak+ seas ( ! ,silurian sw>m$ ) corals1 cr9oids1 & bra*iopods4 ,) ! end ( ! ,silurian p]iod ! ,age ( ,inv]tebrates comes to a close1 giv+ place to ! ,devonian1 ! ,age ( ,fi%es4 ,illu/ration3 ,fig4 #bie4 ,block ( ,lime/one %[+ ,int]ior ,ca/s ( ,p5tam]us oblongus1 a ,common ,silurian ,bra*iopod ,,*apt] ,,xviii ,,! ,,devonian ,9 ,am]ica ! ,silurian is n sep>at$ f ! ,devonian by any m\nta9-mak+ de=mation or cont95tal uplift4 ,! "o p]iod pass$ quietly into ! o!r4 ,_! con=mable sy/ems are s closely relat$1 & ! *ange 9 _! faunas is s gradual1 t geologi/s are n agre$ z to ! precise horizon :i* divides !m4 ,subdivisions & physical geography4 ,! ,devonian is repres5t$ 9 ,new ,york & s\?w>d by ! foll[+ five s]ies4 ,we add ! rocks ( :i* !y are *iefly compos$4 #e ,*emung 44444 s&/ones & s&y %ales #d ,hamilton 44444 %ales & s&/ones #c ,cornif]\s 44444 lime/ones #b ,oriskany 44444 s&/ones #a ,held]b]g 44444 lime/ones ,! ,held]b]g is a transition epo* ref]r$ by "s geologi/s to ! ,silurian4 ,! ?9 s&/ones ( ! ,oriskany m>k an epo* :5 waves work$ ov] ! deposits ( =m] coa/al pla9s4 ,! lime/ones ( ! ,cornif]\s te/ify to a w>m & cle> wide sea :i* ext5d$ f ! ,hudson to beyond ! ,mississippi4 ,corals ?rove luxuriantly1 & _! rema9s1 ) ^? ( mollusks & o!r lime-secret+ animals1 built up great b$s ( lime/one4 ,! bord]+ cont95ts1 z dur+ ! lat] ,silurian1 mu/ n[ h be5 monoton\s l[l&s :i* s5t d[n little ( ev5 ! f9e/ wa/e to ! sea4 ,9 ! ,hamilton ! cle> seas ( ! previ\s epo* became cl\d$ ) mud4 ,! imm5se deposits ( co>se s&/ones & s&y %ales ( ! ,*emung1 :i* are f\nd (f :at 0 at ! "t ! we/ coa/ ( ,appala*ia1 prove an uplift ( t anci5t cont95t4 ,! ,*emung s]ies ext5ds f ! ,catskill ,m\nta9s to nor!a/]n ,ohio & s\? to nor!a/]n ,t5nessee1 cov]+ an area ( n less ?an a hundr$ ?\s& squ>e miles4 ,9 ea/]n ,new ,york x atta9s ?ree ?\s& feet 9 ?ickness2 9 ,p5nsylvania x rea*es ! enorm\s ?ickness ( two miles2 b x rapidly ?9s to ! we/4 ,ev]y:]e ! ,*emung is made ( ?9 b$s ( rapidly alt]nat+ co>se & f9e s&s & clays1 ) an occasional pebble lay]1 & h5ce is a %all[-wat] deposit4 ,! f9e mat]ial has n be5 ?or\ghly w9n[$ f ! co>se by ! long action ( /rong waves & tides4 ,! s&s & clays h und]gone little m sort+ ?an is done by riv]s4 ,we mu/ reg>d ! ,*emung s&/ones z deposits made at ! m\?s ( swift1 turbid riv]s 9 su* great am\nt t !y c\ld be little sort$ & di/ribut$ by waves4 ,ov] consid]able areas ! ,*emung s&/ones be> little or no trace ( ! action ( ! sea4 ,! ,catskill ,m\nta9s1 = example1 h z _! summit lay]s "s ?ree ?\s& feet ( co>se r$ s&/ones ( ?is s]ies1 ^: /ructure is t ( riv] deposits1 & ^: few fossils are *iefly ( fre%-wat] types4 ,! ,*emung is !re=e compos$ ( delta deposits1 m or less work$ ov] by ! sea4 ,! bulk ( ! ,*emung equals t ( ! ,si]ra ,nevada ,m\nta9s4 ,to furni% ?is imm5se volume ( s$im5t a great m\nta9 range1 or highl&1 mu/ h be5 upheav$ :]e ! ,appala*ian l[l& long _h be54 ,to :at height ! ,devonian m\nta9s ( ,appala*ia atta9$ _c be told f ! volume ( ! s$im5ts wa/$ f !m1 = !y may h ris5 b little fa/] ?an !y 7 worn d[n by d5udation4 ,we may inf] f ! "* ( ! wa/e :i* !y furni%$ to ! ,*emung %ores t !y did n rea* an ,alp9e height4 ,! gra9s ( ! ,*emung s&/ones are n ^? :i* w\ld result f me*anical dis9tegration1 z by fro/ on high m\nta9 peaks1 b are r ^? :i* w\ld be left f ! long *emical decay ( silice\s cry/all9e rocks2 = ! m soluble m9]als are l>gely want+4 ,! r$ color ( mu* ( ! deposits po9ts to ! same conclusion4 ,r$ residual clays accumulat$ on ! m\nta9 sides & upl& summits1 & 7 wa%$ z o*]\s silt to m+le ) ! delta s&s4 ,! iron-be>+ igne\s rocks ( ! oldl& also contribut$ by _! decay iron 9 solution to ! riv]s1 to be deposit$ 9 films ( iron oxide ab\t ! qu>tz gra9s ( ! ,*emung s&/ones1 giv+ !m _! r$di% t9ts4 ,life ( ! ,devonian ,plants4 ,! l&s 7 probably clad ) v]dure dur+ ,silurian times1 if n /ill e>li]2 = "s r>e rema9s ( f]ns & o!r l[ly types ( vegetation h be5 f\nd 9 ! /rata ( t sy/em4 ,b x is 9 ! ,devonian t we discov] = ! fir/ "t ! rema9s ( ext5sive & luxuriant =e/s4 ,?is ri* flora rea*$ its climax 9 ! ,c>bonif]\s1 & x w be m conv5i5t to describe its v>i$ types 9 ! next *apt]4 ,rhizoc>ps4 ,9 ! %ales ( ! ,devonian are f\nd microscopic spores ( rhizoc>ps 9 su* c\ntless numb]s t _! weight mu/ be reckon$ 9 hundr$s ( millions ( tons4 ,x w\ld seem t ^! aquatic plants culm9at$ 9 ?is p]iod1 & 9 widely di/ant portions ( ! e>? swampy flats & %all[ lagoons 7 fill$ ) vegetation ( ?is humble type1 ei!r gr[+ f ! bottom or float+ free ^u ! surface4 ,x is to ! res9\s spores ( ! rhizoc>ps t ! petroleum & natural gas f ,devonian rocks are l>gely due4 ,! decomposition ( ! spores has made ! %ales highly bitum9\s1 & ! oil & gas h accumulat$ 9 ! res]voirs ( ov]ly+ por\s s&/ones4 ,inv]tebrates4 ,we mu/ pass ov] ! ev]-*ang+ gr\ps ( ! inv]tebrates ) ! briefe/ notice4 ,*a9 corals became ext9ct at ! close ( ! ,silurian1 b o!r corals 7 extremely common 9 ! ,devonian seas4 ,at _m places corals =m$ ?9 reefs1 z at ,l\isville1 ,k5tucky1 :]e ! h>dness ( ! reef rock is "o ( ! causes ( ! ,falls ( ! ,ohio4 ,sponges1 e*9od]ms1 bra*iopods1 & mollusks 7 abundant4 ,! cephalopods take a new dep>ture4 ,s f> 9 all _! v>i\s =ms1 :e!r /raight1 z ! ,or?oc]as1 or curv$1 or close-coil$ z 9 ! nautilus1 ! septum1 or p>tition divid+ ! *amb]s1 met ! inn] %ell along a simple l9e1 l t ( ! rim ( a sauc]4 ,!re n[ beg9s a gr[? ( ! septum by :i* its edges become %>ply corrugat$1 & ! suture1 or l9e ( juncture ( ! septum & ! %ell1 is ?us angl$4 ,! gr\p 9 :i* ?is gr[? ( ! septum takes place is call$ ! ,goniatite 7,greek gonia1 angle74 ,illu/ration3 ,fig4 #bif4 ,a ,goniatite ,v]tebrates4 ,x is ) ! greate/ int]e/ t we turn n[ to /udy ! backbon$ animals ( ! ,devonian2 = !y are believ$ to be ! ance/ors ( ! ho/s ( v]tebrates :i* h s9ce dom9at$ ! e>?4 ,_! rudim5t>y /ructures =e%ad[$ :at _! desc5dants 7 to be1 & give "s clue to ! e>lie/ v]tebrates f :i* !y sprang4 ,l ^? ^: rema9s are f\nd 9 ! l[] ,paleozoic sy/ems1 all ( ^! ,devonian v]tebrates 7 aquatic & g "u ! g5]al designation ( fi%es4 ,! l[e/ 9 grade & ne>e/1 p]haps1 to ! ance/ral type ( v]tebrates1 0 ! problematic creature1 an in* or s long1 ( ,figure #big4 ,note ! circul> m\? n suppli$ ) jaws1 ! lack ( pair$ f9s1 & ! symmetric tail f91 ) ! column ( c>tilag9\s1 r+like v]tebr runn+ ?r\gh x to ! end4 ,! animal is probably to be plac$ ) ! jawless lampreys & hags1--a gr\p too l[ to be includ$ among true fi%es4 ,illu/ration3 ,fig4 #big4 ,palospondylus ,o/racod]ms4 ,?is ar*aic gr\p1 long s9ce ext9ct1 is also too l[ly to rank among ! true fi%es1 = its memb]s h nei!r jaws nor pair$ f9s4 ,^! small1 fi%like =ms 7 cas$ 9 front ) bony plates develop$ 9 ! sk9 & cov]$ 9 ! re> ) scales4 ,! v]tebr 7 n ossifi$1 = no trace ( !m has be5 f\nd4 ,illu/ration3 ,fig4 #bih4 ,an ,o/racod]m ,devonian fi%es4 ,! true fi%es ( ! ,devonian c be/ be und]/ood by ref]5ce to _! desc5dants n[ liv+4 ,mod]n fi%es are divid$ into sev]al gr\ps3 %>ks & _! allies2 dipnoans2 ganoids1 su* z ! /urgeon & g>2 & teleo/s1--mo/ common fi%es1 su* z ! p]* & cod4 ,illu/ration3 ,fig4 #bii4 ,a ,paleozoic ,%>k ,%>ks4 ,( all gr\ps ( liv+ fi%es ! %>ks are ! olde/ & /ill reta9 mo/ fully ! embryonic *>act]s ( _! ,paleozoic ance/ors4 ,su* *>act]s are ! c>tilag9\s skeleton1 & ! sep>ate gill slits ) :i* ! ?roat wall is pi]c$ & :i* are arrang$ 9 l9e l ! gill op5+s ( ! lamprey4 ,! %>ks ( ! ,silurian & ,devonian are kn[n to u *iefly by _! tee? & f9 sp9es1 = !y 7 unprotect$ by scales or plates1 & 7 devoid ( a bony skeleton4 ,figure #bii is a re/oration ( an ar*aic %>k f a some:at high] horizon4 ,note ! sev5 gill slits & ! lappetlike pair$ f9s4 ,^! f9s seem to be remnants ( ! cont9u\s fold ( sk9 :i*1 z embryology tea*es1 pass$ f =e to aft d[n ea* side ( ! primitive v]tebrate4 ,devonian %>ks 7 comp>atively small4 ,!y _h n evolv$ into ! f]oci\s mon/]s :i* 7 lat] to be ma/]s ( ! seas4 ,illu/ration3 ,fig4 #cjj4 ,a ,devonian ,dipnoan ,dipnoans1 or lung fi%es4 ,^! are repres5t$ to-day by a few peculi> fi%es & are di/+ui%$ by "s high /ructures :i* ally !m ) amphibians4 ,an air sac ) cellul> spaces is connect$ ) ! gullet & s]ves z a rudim5t>y lung4 ,x corresponds ) ! swim bladd] ( mo/ mod]n fi%es1 & appe>s to h _h a common orig9 ) x4 ,we may conceive t ! primordial fi%es n only _h gills us$ 9 brea?+ air dissolv$ 9 wat]1 b also develop$ a saclike p\* (f ! gullet4 ,?is sac evolv$ along two di/9ct l9es4 ,on ! l9e ( ! ance/ry ( mo/ mod]n fi%es its duct 0 clos$ & x became ! swim bladd] us$ 9 flotation & balanc+4 ,on ano!r l9e ( desc5t x 0 left op51 air 0 swall[$ into x1 & x develop$ into ! rudim5t>y lung ( ! dipnoans & into ! m p]fect lungs ( ! amphibians & o!r air-brea?+ v]tebrates4 ,"o ( ! anci5t dipnoans is illu/rat$ 9 ,figure #cjj4 ,"s ( ! memb]s ( ?is ord] 71 l ! o/racod]ms1 cas$ 9 armor1 b _! high] rank is %[n by _! p[]ful jaws & by o!r /ructures4 ,"s ( ^! armor$ fi%es rea*$ tw5ty-five feet 9 l5g? & six feet across ! head4 ,!y 7 ! tyrants ( ! ,devonian seas4 ,illu/ration3 ,fig4 #cja4 ,a ,devonian ,fr+e-,f9n$ ,ganoid ,ganoids4 ,^! take _! "n f _! enamel$ plates or scales ( bone4 ,! few g5]a n[ surviv+ are ! desc5dants ( ! tribes :i* sw>m$ 9 ! ,devonian seas4 ,a re/oration ( "o ( a lead+ ord]1 ! fr+e-f9n$ ganoids1 is giv5 9 ,figure #cja4 ,! side f9s1 :i* correspond to ! limbs ( ! high] v]tebrates1 are q unlike ^? ( mo/ mod]n fi%es4 ,_! rays1 in/ead ( radiat+ f a common base1 fr+e a c5tral lobe :i* conta9s a c>tilag9\s axis4 ,! tee? ( ! ,devonian ganoids %[ a complicat$ fold$ /ructure4 ,g5]al *>act]i/ics ( ,devonian fi%es4 ,! noto*ord is p]si/5t4 ,! noto*ord is a cont9u\s rod ( c>tilage1 or gri/le1 :i* 9 ! embryological gr[? ( v]tebrate animals supports ! sp9al n]ve cord be=e ! =mation ( ! v]tebr4 ,9 mo/ mod]n fi%es & 9 all high] v]tebrates ! noto*ord is gradually remov$ z ! bodies ( ! v]tebr are =m$ ab\t x2 b 9 ! ,devonian fi%es x p]si/s ?r\gh maturity & ! v]tebr rema9 incomplete4 ,! skeleton is c>tilag9\s4 ,?is also is an embryological *>act]i/ic4 ,9 ! ,devonian fi%es ! v]tebr1 z well z ! o!r p>ts ( ! skeleton1 h n ossifi$1 or *ang$ to bone1 b rema9 9 _! primitive c>tilag9\s condition4 ,illu/ration3 ,fig4 #cjb4 ,v]tebr ( ,/urgeon 9 side view ,a2 & v]tical transv]se section ,b1 %[+ ,noto*ord *1 & ,neural ,canal m ,! tail f9 is v]tebrat$4 ,! backbone runs ?r\gh ! f9 & is fr+$ above & bel[ ) its v]tical rays4 ,9 "s fi%es ) v]tebrat$ tail f9s ! f9 is symmetric 7,fig4 #cjj71 & ?is seems to be ! primitive type4 ,9 o!rs ! tail f9 is unsymmetric3 ! backbone runs into ! upp] lobe1 leav+ ! two lobes ( unequal size4 ,9 mo/ mod]n fi%es 7! teleo/s7 ! tail f9 is n v]tebrat$3 ! sp9al column ends 9 a broad plate1 to :i* ! div]g+ f9 rays are atta*$4 ,b along ) ^! embryonic *>act]s1 :i* 7 common to all ,devonian fi%es1 !re 7 o!r /ructures 9 c]ta9 gr\ps :i* =e%ad[$ ! high] /ructures ( ! l& v]tebrates :i* 7 yet to come3 air sacs :i* 7 to develop into lungs1 & c>tilag9\s axes 9 ! side f9s :i* 7 a prophecy ( limbs4 ,! v]tebrates _h already advanc$ f> en\gh to prove ! sup]iority ( _! type ( /ructure to all o!rs4 ,_! int]nal skeleton af=d$ ! be/ atta*m5t = muscles & enabl$ !m to become ! l>ge/ & mo/ p[]ful creatures ( ! "t4 ,! c5tral n]v\s sy/em1 ) ! pr$om9ance giv5 to ! ganglia at ! =e end ( ! n]ve cord1--! bra91--already end[$ !m ) great] en]gy ?an ! inv]tebrates2 &1 /ill m important1 ^! /ructures conta9$ ! possibility ( developm5t into ! m highly organiz$ l& v]tebrates :i* 7 to rule ! e>?4 ,teleo/s4 ,! great gr\p ( fi%es call$ ! teleo/s1 or ^? ) complete bony skeletons1 to :i* mo/ mod]n fi%es belong1 may be m5tion$ "h1 al?\gh 9 ! ,devonian !y _h n yet appe>$4 ,! teleo/s are a highly specializ$ type1 adapt$ mo/ p]fectly to _! aquatic environm5t4 ,heavy armor has be5 disc>d$1 & reliance is plac$ in/ead on swiftness4 ,! skeleton is completely ossifi$ & ! noto*ord remov$4 ,! v]tebr h be5 economically )drawn f ! tail1 & ! c>tilag9\s axis ( ! side f9s has be5 f\nd unnecess>y4 ,! air sac has become a swim bladd]4 ,9 ?is complete specialization !y h long s9ce lo/ ! possibility ( evolv+ into high] types4 ,x is int]e/+ to note t ! mod]n teleo/s 9 _! embryological gr[? pass ?r\gh ! /ages :i* *>act]iz$ ! maturity ( _! ,devonian ance/ors2 _! skeleton is c>tilag9\s & _! tail f9 v]tebrat$4 ,,*apt] ,,xix ,,! ,,c>bonif]\s ,! ,c>bonif]\s sy/em is s nam$ f ! l>ge am\nt ( coal :i* x conta9s4 ,o!r sy/ems1 f ! ,devonian on1 are coal be>+ also1 b none s ri*ly & to s wide an ext5t4 ,nev] be=e or s9ce h ! peculi> conditions be5 s favorable = ! =mation ( ext5sive coal deposits4 ,) few exceptions ! ,c>bonif]\s /rata re/ on ^? ( ! ,devonian )\t any m>k$ uncon=mity2 ! "o p]iod pass$ quietly into ! o!r1 ) no great physical di/urbances4 ,! ,c>bonif]\s includes ?ree di/9ct s]ies4 ,! l[] is call$ ! ,mississippian1 f ! outcrop ( its =mations along ! ,mississippi ,riv] 9 c5tral & s\!rn ,ill9ois & ! adjac5t portions ( ,i[a & ,miss\ri4 ,! middle s]ies is call$ ! ,p5nsylvanian 7or ,coal ,measures71 f its wide occurr5ce ov] ,p5nsylvania4 ,! upp] s]ies is nam$ ! ,p]mian1 f ! prov9ce ( ,p]m 9 ,russia4 ,! ,mississippian s]ies4 ,9 ! int]ior ! ,mississippian is compos$ *iefly ( lime/ones1 ) "s %ales1 :i* tell ( a cle>1 w>m1 epicont95tal sea sw>m+ ) cr9oids1 corals1 & %ells1 & occasionally cl\d$ ) silt f ! l&4 ,9 ! ea/]n region1 ,new ,york _h be5 add$ by uplift to ! ,appala*ian l& :i* n[ 0 unit$ to ! nor!rn area4 ,f ea/]n ,p5nsylvania s\?w>d !re 7 laid 9 a subsid+ tr\gh1 fir/1 ?ick s&/ones 7! ,pocono s&/one71 & lat] /ill heavi] %ales1--! two toge!r rea*+ ! ?ickness ( f\r ?\s& feet & m4 ,we inf] a r5ew$ uplift ( ,appala*ia simil> to t ( ! lat] epo*s ( ! ,devonian1 b z mu* less 9 am\nt z ! volume ( s$im5ts is small]4 ,! ,p5nsylvanian ,s]ies ,! ,mississippian 0 br\ght to an end by a quiet oscillation :i* lift$ l>ge areas slightly above ! sea1 & ! ,p5nsylvanian began ) a movem5t 9 ! opposite direction4 ,! sea encroa*$ on ! new l&1 & spread f> & wide a great basal conglom]ate & co>se s&/ones4 ,on ?is anci5t bea* deposit a gr\p ( /rata re/s :i* we mu/ n[ int]pret4 ,!y consi/ ( alt]nat+ %ales & s&/ones1 ) "h & !re a b$ ( lime/one & an occasional seam ( coal4 ,a /ratum ( fire clay commonly und]lies a coal seam1 & !re occur also b$s ( iron ore4 ,we give a typical section ( a v small portion ( ! s]ies at a locality 9 ,p5nsylvania4 ,al?\gh "s ( ! m9or *anges are omitt$1 ! section %[s ! rapid alt]nation ( ! /rata3 #i ,s&/one & %ale 44444 #be #h ,lime/one 44444 #ah #g ,s&/one 44444 #aj #f ,coal 44444 #a-f #e ,%ale 44444 #j-b #d ,s&/one 44444 #dj #c ,lime/one 44444 #aj #b ,coal 44444 #e-ab #a ,fire clay 44444 #c ,?is section %[s m coal ?an is usual2 on ! :ole1 coal seams d n take up m ?an "o foot 9 fifty ( ! ,coal ,measures4 ,!y v>y also 9 ?ickness m ?an is se5 9 ! section1 "s exceptional seams rea*+ ! ?ickness ( fifty feet4 ,h[ coal 0 made4 #a4 ,coal is ( vegetable orig94 ,exam9$ "u ! microscope ev5 an?racite1 or h>d coal1 is se5 to conta9 c>boniz$ vegetal tissues4 ,!re are also all gradations connect+ ! h>de/ an?racite--?r\gh semibitum9\s coal1 bitum9\s or s(t coal1 lignite 7an imp]fect coal 9 :i* sometimes woody fib]s may be se5 little *ang$7--) peat & decay+ vegetable tissues4 ,coal is compress$ & m9]aliz$ vegetal matt]4 ,its v>ieties dep5d on ! p]fection to :i* ! peculi> *ange call$ bitum9ization has be5 c>ri$1 & also1 z %[n 9 ! table bel[1 on ! degree to :i* ! volatile sub/ances & wat] h escap$1 & on ! p] c5t ( c>bon rema9+4 ,peat ,bitum9\s ,dismal ,lignite ,coal ,an?racite ,swamp ,texas ,p5n4 ,p5n4 ,moi/ure #gh4hi #ad4fg #a4cj #b4gd ,volatile matt] #ac4hd #cg4cb #bj4hg #d4be ,fix$ c>bon #f4di #da4jg #fg4bj #ha4ea ,a% #j4gh #f4fi #h4hj #aj4hg #b4 ,! vegetable rema9s associat$ ) coal are ^? ( l& plants4 #c4 ,coal accumulat$ 9 ! pres5ce ( wat]2 = x is only :5 ?us protect$ f ! air t vegetal matt] is pres]v$4 #d4 ,! vegetation ( coal accumulat$ = ! mo/ "p :]e x grew2 x 0 n g5]ally drift$ & deposit$ by waves & curr5ts4 ,commonly ! fire clay b5ea? ! seam is p5etrat$ ) roots1 & ! %ale above is pack$ ) leaves ( f]ns & o!r plants z beautifully press$ z 9 a h]b>ium4 ,!re (t5 is associat$ ) ! seam a fossil =e/1 ) ! /umps1 :i* are /ill /&+ :]e !y grew1 _! spread+ roots1 & ! soil b5ea?1 all *ang$ to /one4 ,9 ! ,nova ,scotia field1 out ( sev5ty-six di/9ct coal seams1 tw5ty are und]la9 by old =e/ gr\nds4 ,! pres5ce ( fire clay b5ea? a seam po9ts 9 ! same direction4 ,su* und]clays )/& int5se heat & are us$ 9 mak+ fire brick1 because _! alkalies h be5 remov$ by ! long-cont9u$ gr[? ( vegetation4 ,fuel coal is also too pure to h be5 accumulat$ by driftage4 ,9 t case we %\ld expect to f9d x mix$ ) mud1 :ile 9 fact x (t5 conta9s no m a% ?an ! vegetal matt] w\ld furni% f :i* x has be5 compress$4 ,illu/ration3 ,fig4 #cjc4 ,fossil ,tree ,/umps ( a ,c>bonif]\s ,=e/1 ,scotl& ,^! conditions are fairly met 9 ! great swamps ( riv] pla9s & deltas & ( coa/al pla9s1 su* z ! great ,dismal ,swamp1 :]e ?\s&s ( g5]ations ( =e/s ) _! und]gr[?s contribute _! /ems & leaves to =m ?ick b$s ( peat4 ,a coal seam is a fossil peat b$4 ,geographical conditions dur+ ! ,p5nsylvanian4 ,! ,c>bonif]\s peat swamps 7 ( va/ ext5t4 ,a map ( ! ,coal ,measures 7,fig4 #bfj7 %[s t ! coal m>%es /ret*$1 ) v>i\s int]ruptions ( high] gr\nd & /raits ( op5 wat]1 f ea/]n ,p5nsylvania into ,alabama1 ,texas1 & ,kansas4 ,"s individual coal b$s may /ill be trac$ ov] a ?\s& squ>e miles1 despite ! erosion :i* !y h suff]$4 ,x taxes ! imag9ation to conceive t ! v>i$ region includ$ )9 ^! limits 0 = hundr$s ( ?\s&s ( ye>s a m>%y pla9 cov]$ ) tropical jungles su* z t pictur$ 9 ,figure #cjd4 ,on ! basis t peat loses f\r fif?s ( its bulk 9 *ang+ to coal1 we may reckon ! ?ickness ( ^! anci5t peat b$s4 ,coal seams six & t5 feet ?ick1 :i* are n uncommon1 repres5t peat b$s ?irty & fifty feet 9 ?ickness1 :ile mammo? coal seams fifty feet ?ick h be5 compress$ f peat b$s two hundr$ & fifty feet deep4 ,at ! same "t1 ! ?\s&s ( feet ( m>9e & fre%-wat] s$im5ts1 ) _! repeat$ alt]nations ( lime/ones1 s&/ones1 & %ales1 9 :i* ! seams ( coal occur1 prove a sl[ subsid5ce1 ) _m *anges 9 its rate1 ) halts :5 ! l& 0 at a /ill/&1 & ) occasional movem5ts upw>d4 ,:5 subsid5ce 0 mo/ rapid & long cont9u$ ! sea encroa*$ f> & wide ^u ! l[l&s & cov]$ ! coal swamps ) s&s & muds & limy oozes4 ,:5 subsid5ce slack5$ or ceas$ ! l& ga9$ on ! sea4 ,bays 7 b>r$1 & lagoons z !y gradually fill$ ) mud became m>%es4 ,riv] deltas pu%$ =w>d1 bury+ ) _! silts ! sunk5 peat b$s ( e>li] c5turies1 & at ! surface em]g$ 9 broad1 swampy flats1--l ^? ( ! deltas ( ! ,mississippi & ! ,ganges1--:i* soon 7 cov]$ ) luxuriant =e/s4 ,at times a g5tle uplift br\ght to sea level great coa/al pla9s1 :i* = ages rema9$ mantl$ ) ! jungle1 _! undevelop$ dra9age clogg$ ) its debris1 & 7 !n aga9 subm]g$4 ,illu/ration3 ,fig4 #cjd4 ,ideal ,l&scape ( ! ,p5nsylvanian ,epo* ,physical geography ( ! sev]al regions4 ,! ,acadian region lay on ! ea/]n side ( ! nor!rn l&1 :]e n[ are ,new ,brunswick & ,nova ,scotia1 & 0 an imm5se riv] delta4 ,"h riv] deposits ri* 9 coal accumulat$ to a dep? ( sixte5 ?\s& feet4 ,! area ( ?is coal field is e/imat$ at ab\t ?irty-six ?\s& squ>e miles4 ,! ,appala*ian region skirts ! ,appala*ian oldl& on ! we/ f ! s\!rn b\nd>y ( ,new ,york to nor!rn ,alabama1 ext5d+ we/ into ea/]n ,ohio4 ,! ,c9c9nati anticl9e 0 n[ a p59sula1 & ! broad gulf :i* _h la9 betwe5 x & ,appala*ia 0 trans=m$ at ! beg9n+ ( ! ,p5nsylvanian into wide m>%y pla9s1 n[ s9k+ b5ea? ! sea & n[ em]g+ f x4 ,?is area subsid$ dur+ ! ,c>bonif]\s p]iod to a dep? ( ne>ly t5 ?\s& feet4 ,! ,c5tral region lay we/ ( ! p59sula ( ! ,c9c9nati anticl9e1 & ext5d$ f ,indiana we/ into ea/]n ,nebraska1 & f c5tral ,i[a & ,ill9ois s\?w>d ab\t ! anci5t isl& 9 ,miss\ri & ,arkansas into ,oklahoma & ,texas4 ,on ! nor? ! subsid5ce 9 ?is area 0 comp>atively slight1 = ! ,c>bonif]\s /rata sc>cely exce$ two ?\s& feet 9 ?ickness4 ,b 9 ,arkansas & ,indian ,t]ritory ! d[nw>d movem5t am\nt$ to f\r & five miles1 z is prov$ by %oal wat] deposits ( t imm5se ?ickness4 ,! coal fields ( ,indiana1 & ,ill9ois are n[ sep>at$ by erosion f ^? ly+ we/ ( ! ,mississippi ,riv]4 ,at ! s\? ! ,appala*ian l& seems /ill to h /ret*$ away to ! we/ across ,l\isiana & ,mississippi into ,texas1 & ?is we/w>d ext5sion =m$ ! s\!rn b\nd>y ( ! coal m>%es ( ! cont95t4 ,! ?ree regions j m5tion$ include ! *ief ,c>bonif]\s coal fields ( ,nor? ,am]ica4 ,includ+ a field 9 c5tral ,mi*igan evid5tly =m$ 9 an inclos$ bas9 7,fig4 #bfj71 & "o 9 ,rhode ,isl&1 ! total area ( ,am]ican coal fields has be5 reckon$ at n less ?an two hundr$ ?\s& squ>e miles4 ,we c h>dly e/imate ! value ( ^! great /ores ( fossil fuel to an indu/rial civilization4 ,! =e/s ( ! coal swamps accumulat$ 9 _! woody tissues ! en]gy :i* !y receiv$ f ! sun 9 light & heat1 & x is ?is sol> en]gy long /or$ 9 coal seams :i* n[ =ms ! _w's *ief s\rce ( p[] 9 manufactur+4 ,! we/]n area4 ,on ! ,great ,pla9s beyond ! ,miss\ri ,riv] ! ,c>bonif]\s /rata pass "u ^? ( m rec5t sy/ems4 ,:]e !y reappe>1 z ab\t dissect$ m\nta9 axes or on /ripp$ plateaus1 !y consi/ :olly ( m>9e deposits & are devoid ( coal4 ,! ri* coal fields ( ! ,we/ are ( lat] date4 ,on ! :ole ! ,c>bonif]\s seems to h be5 a "t ( subsid5ce 9 ! ,we/4 ,?r\gh\t ! p]iod a sea cov]$ ! ,great ,bas9 & ! plateaus ( ! ,colorado ,riv]4 ,at ! "t ( ! greate/ depression ! sites ( ! c5tral *a9s ( ! ,rockies 7 probably isl&s1 b e>ly 9 ! p]iod !y may h be5 connect$ ) ! broad l&s to ! s\? & ea/4 ,?\s&s ( feet ( ,c>bonif]\s s$im5ts 7 deposit$ :]e ! ,si]ra ,nevada ,m\nta9s n[ /&4 ,! ,p]mian4 ,z ! ,c>bonif]\s p]iod drew t[>d its close ! sea gradually )drew f ! ea/]n "p ( ! cont95t4 ,:]e ! sea l+]$ 9 ! deepe/ tr\ghs1 & :]e inclos$ bas9s 7 cut (f f x1 ! /rata ( ! ,p]mian 7 deposit$4 ,su* are f\nd 9 ,new ,brunswick1 9 ,p5nsylvania & ,we/ ,virg9ia1 9 ,texas1 & 9 ,kansas4 ,9 s\?we/]n ,kansas ext5sive ,p]mian b$s ( rock salt & gypsum %[ t "h lay great salt lakes 9 :i* ^! m9]als 7 precipitat$ z _! br9es grew d5se & dri$ away4 ,9 ! s\!rn hemisph]e ! ,p]mian deposits are s extraord9>y t !y des]ve a brief notice1 al?\gh we h s f> omitt$ m5tion ( ! great ev5ts :i* *>act]iz$ ! evolution ( o!r cont95ts ?an our own4 ,! ,p]mian fauna-flora ( ,au/ralia1 ,india1 ,s\? ,africa1 & ! s\!rn "p ( ,s\? ,am]ica are s simil> t ! inf]5ce is a reasonable "o t ^! widely sep>at$ regions 7 !n connect$ toge!r1 probably z ext5sions ( a great ant>ctic cont95t4 ,int]b$d$ ) ! ,p]mian /rata ( ! fir/ ?ree c\ntries nam$ are ext5sive & ?ick deposits ( a peculi> nature :i* are cle>ly anci5t gr\nd mora9es4 ,clays & s&1 n[ h>d5$ to firm rock1 are inset ) unsort$ /ones ( all sizes1 :i* (t5 are facet$ & scrat*$4 ,moreov]1 ^! b[ld] clays re/ on rock pavem5ts :i* are poli%$ & scor$ ) glacial m>k+s4 ,h5ce t[>d ! close ( ! ,paleozoic ! s\!rn l&s ( ! ea/]n hemisph]e 7 invad$ by great glaci]s or p]haps by ice %eets l t :i* n[ %r\ds ,gre5l&4 ,^! ,p]mian gr\nd mora9es are n ! fir/ traces ( ! "w ( glaci]s met ) 9 ! geological record4 ,simil> deposits prove glaciation 9 ,norway succe$+ ! pre-,cambrian /age ( elevation1 & ,cambrian glacial drift has rec5tly be5 f\nd 9 ,*9a4 ,! ,appala*ian de=mation4 ,we h se5 t dur+ ,paleozoic times a long1 n>r[ tr\gh ( ! sea lay (f ! we/]n coa/ ( ! anci5t l& ( ,appala*ia1 :]e n[ are ! ,appala*ian ,m\nta9s4 ,dur+ ! long ages ( ?is era ! tr\gh gradually subsid$1 al?\gh ) _m /ill/&s & ) occasional slight oscillations upw>d4 ,mean:ile ! l& ly+ to ! ea/ 0 gradually uplift$ at v>y+ rates & ) long pauses4 ,! wa/e ( ! ris+ l& 0 con/antly transf]r$ to ! s9k+ m>g9al sea bottom1 & on ! :ole ! tr\gh 0 fill$ ) s$im5ts z rapidly z x subsid$4 ,! sea 0 ?us kept %all[1 & at times1 especially t[>d ! close ( ! era1 mu* ( ! area 0 upbuilt or rais$ to l[1 m>%y1 coa/al pla9s4 ,:5 ! ,c>bonif]\s 0 end$ ! wa/e :i* _h be5 remov$ f ! l& & laid along its m>g9 9 ! successive =mations ( ! ,paleozoic _h rea*$ a ?ickness ( betwe5 ?irty & =ty ?\s& feet4 ,bo? by s$im5tation & by subsid5ce ! tr\gh _h n[ become a belt ( weakness 9 ! cru/ ( ! e>?4 ,"h ! cru/ 0 n[ made ( lay]s to ! dep? ( six or sev5 miles4 ,9 comp>ison ) ! massive cry/all9e rocks ( ,appala*ia on ! ea/1 ! lay]$ rock ( ! tr\gh 0 weak to resi/ lat]al pressure1 z a ream ( %eets ( pap] is weak :5 comp>$ ) a solid bo>d ( ! same ?ickness4 ,x 0 weak] also ?an ! region to ! we/1 s9ce !re ! s$im5ts 7 mu* ?9n]4 ,besides1 by ! long-cont9u$ depression ! /rata ( ! tr\gh _h be5 b5t f ! flat-ly+ attitude 9 :i* !y 7 laid to "o 9 :i* !y 7 less able to resi/ a horizontal ?ru/4 ,!re n[ occurr$ "o ( ! critical /ages 9 ! hi/ory ( ! planet1 :5 ! cru/ crumples "u its own weight & %r9ks d[n ^u a nucleus :i* is dim9i%+ 9 volume & no long] able to support x4 ,"u sl[ b resi/less pressure ! /rata ( ! ,appala*ian tr\gh 7 ?ru/ aga9/ ! rigid l&1 & sl[ly1 /eadily b5t into long folds ^: axes ran nor!a/-s\?we/ p>allel to ! anci5t coa/ l9e4 ,x 0 on ! ea/]n side next ! buttress ( ! l& t ! de=mation 0 ! greate/1 & ! folds mo/ /eep & close4 ,9 c5tral ,p5nsylvania & ,we/ ,virg9ia ! folds 7 = ! mo/ "p op54 ,s\? ( ^! /ates ! folds 7 m closely appress$1 ! /rata 7 mu* brok51 & ! great ?ru/ faults 7 =m$ :i* h be5 describ$ already4 ,9 ea/]n ,p5nsylvania seams ( bitum9\s coal 7 alt]$ to an?racite1 :ile outside ! region ( /rong de=mation1 z 9 we/]n ,p5nsylvania1 !y rema9$ un*ang$4 ,an important factor 9 ! de=mation 0 ! massive lime/ones ( ! ,cambrian-,ordovician4 ,because ( ^! ?ick1 resi/ant b$s ! rocks 7 b5t into wide folds & %e>$ 9 places ) great ?ru/ faults4 ,_h ! /rata be5 weak %ales1 an equal pressure w\ld h cru%$ & ma%$ !m4 ,al?\gh ! great e>? folds 7 sl[ly rais$1 & no d\bt erod$ 9 _! ris+1 !y =m$ 9 all probability a range ( l(ty m\nta9s1 ) a wid? ( f fifty to a hundr$ & tw5ty-five miles1 :i* /ret*$ f ,new ,york to c5tral ,alabama4 ,f _! bases l[l&s ext5d$ we/w>d to beyond ! ,miss\ri ,riv]4 ,at ! same "t ranges 7 upridg$ out ( ?ick ,paleozoic s$im5ts bo? 9 ! ,bay ( ,fundy region & 9 ! ,indian ,t]ritory4 ,! ea/]n portion ( ! ,nor? ,am]ican cont95t 0 n[ well-nigh complete4 ,! date ( ! ,appala*ian de=mation is told 9 ! usual way4 ,! ,c>bonif]\s /rata1 ne>ly two miles ?ick1 are all infold$ 9 ! ,appala*ian ridges1 :ile ! next deposits f\nd 9 ?is region--^? ( ! lat] portion ( ! fir/ p]iod 7! ,trias7 ( ! succe$+ era--re/ uncon=mably on ! worn edges ( ! ,appala*ian fold$ /rata4 ,! de=mation !re=e took place ab\t ! close ( ! ,paleozoic4 ,x seems to h begun 9 ! ,p]mian1 91 ea/]n ,p5nsylvania1--= "h ! ,p]mian /rata are want+1--& to h cont9u$ into ! ,trias1 ^: e>li] =mations are abs5t ov] all ! area4 ,) ?is wide uplift ! subsid5ce ( ! sea floor :i* _h s long be5 g5]al 9 ea/]n ,nor? ,am]ica came to an end4 ,deposition n[ gave place to erosion4 ,! s$im5t>y record ( ! ,paleozoic 0 clos$1 & aft] an unkn[n lapse ( "t1 "h unrecord$1 ! annals ( ! succe$+ era 7 writt5 "u *ang$ conditions4 ,9 we/]n ,nor? ,am]ica ! clos+ /ages ( ! ,paleozoic 7 m>k$ by important oscillations4 ,! ,great ,bas91 :i* _h long be5 a m$it]ranean sea1 0 conv]t$ into l& ov] we/]n ,utah & ea/]n ,nevada1 :ile ! waves ( ! ,pacific roll$ across ,cali=nia & we/]n ,nevada4 ,! abs5ce ( tuffs & lavas among ! ,c>bonif]\s /rata ( ,nor? ,am]ica %[s t "h volcanic action 0 s+ul>ly want+ dur+ ! entire p]iod4 ,ev5 ! ,appala*ian de=mation 0 n accompani$ by any volcanic outbur/s4 ,illu/ration3 ,fig4 #cje4 ,c>bonif]\s ,f]ns ,illu/ration3 ,fig4 #cjf4 ,calamites ,life ( ! ,c>bonif]\s ,plants4 ,! gloomy =e/s & d5se und]gr[?s ( ! ,c>bonif]\s jungles w\ld appe> unfamili> to u c\ld we see !m z !y grew1 & ev5 a botani/ w\ld f9d _m ( _! =ms p]plex+ & h>d to classify4 ,none ( our mod]n trees w\ld meet ! eye4 ,plants ) conspicu\s fl[]s ( fragrance & beauty 7 yet to come4 ,ev5 mosses & grasses 7 /ill abs5t4 ,tree f]ns lift$ _! cr[ns ( fea!ry fronds high 9 air on trunks ( woody tissue2 & l[ly h]bace\s f]ns1 "s belong+ to exi/+ families1 c>pet$ ! gr\nd4 ,_m ( ! f]nlike =ms1 h[ev]1 h di/9ct aff9ities ) ! cycads1 ( :i* !y may be ! ance/ors1 & "s be> se$s & mu/ be class$ z gymnosp]ms4 ,d5se ?ickets1 l cane or bamboo brakes1 7 compos$ ( ?ick clumps ( ,calamites1 ^: sl5d]1 jo9t$ /ems %ot up to a height ( =ty feet1 & at ! jo9ts bore sl5d] bran*es set ) :orls ( leaves4 ,^! 7 close allies ( ! ,equiseta or horsetails1 ( ! pres5t2 b !y bore *>act]i/ics ( high] classes 9 ! woody /ructures ( _! /ems4 ,!re 7 also va/ monoton\s =e/s1 compos$ *iefly ( trees belong+ to ! lycopods1 & ^: ne>e/ relatives to-day are ! little club mosses ( our ea/]n woods4 ,two families ( lycopods des]ve special m5tion1--! ,lepidod5drons & ! ,sigill>ia4 ,illu/ration3 ,fig4 #cjg4 ,lepidod5dron ,illu/ration3 ,fig4 #cjh4 ,sigill>ia ,! ,lepidod5dron1 or scale tree1 0 a gigantic club moss fifty & sev5ty-five feet high1 spread+ t[>d ! top into /\t bran*es1 at ^: ends 7 borne cone-%ap$ spore cases4 ,! y\ng] p>ts ( ! tree 7 clo!d ) /iff ne$le-%ap$ leaves1 b else:]e ! trunk & bran*es 7 m>k$ ) scalelike sc>s1 left by ! fall5 leaves1 & arrang$ 9 spiral r[s4 ,! ,sigill>ia1 or seal tree1 0 simil> to ! ,lepidod5dron1 b its flut$ trunk divid$ into ev5 few] bran*es1 & 0 dott$ ) v]tical r[s ( leaf sc>s1 l ! impressions ( a seal4 ,bo? ,lepidod5dron & ,sigill>ia 7 an*or$ by means ( great cablelike und]gr\nd /ems1 :i* ran to long di/ances ?r\gh ! m>%y gr\nd4 ,! trunks ( bo? trees _h a ?ick woody r9d1 inclos+ loose cellul> tissue & a pi?4 ,_! holl[ /umps1 fill$ ) s& & mud1 are common 9 ! ,coal ,measures1 & 9 !m "o sometimes f9ds leaves & /ems1 l& %ells1 & ! bones ( little reptiles ( ! "t :i* made _! home !re4 ,x is important to note t "s ( ^! gigantic lycopods1 :i* are class$ ) ! cryptogams1 or fl[]less plants1 _h pi? & m$ull>y rays divid+ _! cyl9d]s into woody w$ges4 ,^! *>act]s connect !m ) ! phan]ogams1 or fl[]+ plants4 ,l s _m ( ! organisms ( ! remote pa/1 !y 7 connect+ types f :i* gr\ps n[ widely sep>at$ h div]g$4 ,gymnosp]ms1 ak9 to ! cycads1 7 also pres5t 9 ! ,c>bonif]\s =e/s4 ,su* 7 ! diff]5t species ( ,cordaites1 trees pyramidal 9 %ape1 ) /rap-%ap$ leaves & nutlike fruit4 ,o!r gymnosp]ms 7 relat$ to ! yews1 & x 0 by ^! t _m ( ! fossil nuts f\nd 9 ! ,coal ,measures 7 borne4 ,x is ?\ght by "s t ! gymnosp]ms _h _! /ation on ! dri] pla9s & high] l&s4 ,! ,c>bonif]\s jungles ext5d$ ov] p>ts ( ,europe & ( ,asia1 z well z ea/]n ,nor? ,am]ica1 & rea*$ f ! equator to )9 n9e degrees ( ! nor? pole4 ,ev5 9 ^! widely sep>at$ regions ! g5]a & species ( coal plants are close ak9 & (t5 id5tical4 ,inv]tebrates4 ,among ! e*9od]ms1 cr9oids are n[ exce$+ly abundant1 sea ur*9s are m pl5tiful1 & sea cucumb]s are f\nd n[ = ! fir/ "t4 ,trilobites are rapidly decl9+1 & pass away =ev] ) ! close ( ! p]iod4 ,eurypt]ids are common2 /++ scorpions are abundant2 & "h occur ! fir/-kn[n spid]s4 ,we h se5 t ! ar?ropods 7 ! fir/ ( all animals to conqu] ! realm ( ! air1 ! e>lie/ insects appe>+ 9 ! ,ordovician4 ,insects _h n[ become exce$+ly abundant1 & ! ,c>bonif]\s =e/s sw>m$ ) ! ance/ral types ( dragon flies1--"s ) a spread ( w+ ( m ?an two feet1--,may flies1 crickets1 & locu/s4 ,cockroa*es infe/$ ! swamps1 & "o hundr$ & ?irty-?ree species ( ?is anci5t ord] h be5 discov]$ 9 ! ,c>bonif]\s ( ,nor? ,am]ica4 ,! high] fl[]-lov+ insects are /ill abs5t2 ! reign ( ! fl[]+ plants has n yet begun4 ,! ,paleozoic insects 7 g5]aliz$ types connect+ ! pres5t ord]s4 ,_! =e w+s 7 /ill membran\s & delicately ve9$1 & us$ 9 fly+2 !y _h n yet become ?ick1 & useful only z w+ cov]s1 z 9 _m ( _! desc5dants4 ,illu/ration3 ,fig4 #cji4 ,c>bonif]\s ,bra*iopods ,a1 ,productus2 ,b1 ,spirif]1 ! "r-h& figure %[+ ! int]ior ) ! calc>e\s spires = ! support ( ! arms ,fi%es /ill held to ! ,devonian types1 ) ! exception t ! /range o/racod]ms n[ _h p]i%$4 ,amphibians4 ,! v]tebrates _h n[ foll[$ ! ar?ropods & ! mollusks ^u ! l&1 & develop$ a high] type adapt$ to ! new environm5t4 ,amphibians--! class to :i* frogs & salam&]s belong--n[ appe>1 ) lungs = brea?+ air & ) limbs = locomotion on ! l&4 ,mo/ ( ! ,c>bonif]\s amphibians 7 %ap$ l ! salam&]1 ) weak limbs adapt$ m = crawl+ ?an = c>ry+ ! body well above ! gr\nd4 "s legless1 deg5]ate =ms 7 snakelike 9 %ape4 ,illu/ration3 ,fig4 #caj4 ,a ,c>bonif]\s ,dragon ,fly ,"o t5? natural size ,! e>lie/ amphibians diff] f ^? ( to-day 9 a numb] ( respects4 ,!y 7 connect+ types l9k+ toge!r fi%es1 f :i* !y 7 desc5d$1 ) reptiles1 ( :i* !y 7 ! ance/ors4 ,!y reta9$ ! evid5ce ( _! close relation%ip ) ! ,devonian fi%es 9 _! cold blood1 _! gills & aquatic habit dur+ _! l>val /age1 _! tee? ) d5t9e infold$ l ^? ( ! ,devonian ganoids b /ill m intricately1 & _! biconcave v]tebr :i* nev] completely ossifi$4 ,^!1 ! highe/ v]tebrates ( ! "t1 _h n yet advanc$ beyond ! embryonic /age ( ! m or less c>tilag9\s skeleton & ! p]si/5t noto*ord4 ,illu/ration3 ,fig4 #caa4 ,a ,c>bonif]\s ,amphibian ,illu/ration3 ,fig4 #cab4 ,transv]se ,section ( ,segm5t ( ,too? ( ,c>bonif]\s ,amphibian ,on ! o!r h&1 ! skull ( ! ,c>bonif]\s amphibians 0 made ( close-set bony plates1 l ! skull ( ! reptile1 r ?an l t ( ! frog1 ) its op5 spaces 7,figs4 #cac & #cad74 ,unlike mod]n amphibians1 ) _! slimy sk91 ! ,c>bonif]\s amphibians wore an armor ( bony scales ov] ! v5tral surface & sometimes ov] ! back z well4 ,illu/ration3 ,fig4 #cac4 ,skull ( a ,p]mian ,amphibian f ,texas ,illu/ration3 ,fig4 #cad4 ,skull ( a ,frog ,x is int]e/+ to notice f ! footpr9ts & skeletons ( ^! e>lie/-kn[n v]tebrates ( ! l& :at 0 ! primitive numb] ( digits4 ,! ,c>bonif]\s amphibians _h five-to$ feet1 ! primitive type ( foot1 f :i* _! desc5dants ( high] ord]s1 ) a small] numb] ( digits1 h div]g$4 ,! ,c>bonif]\s 0 ! age ( lycopods & amphibians1 z ! ,devonian _h be5 ! age ( rhizoc>ps & fi%es4 ,life ( ! ,p]mian4 ,! close ( ! ,paleozoic 01 z we h se51 a "t ( m>k$ physical *anges4 ,! upridg+ ( ! ,appala*ians _h begun & a wide cont95tal uplift--prov$ by ! abs5ce ( ,p]mian deposits ov] l>ge areas :]e s$im5tation _h gone on be=e--op5$ new l&s = settlem5t to hordes ( air-brea?+ animals4 ,*anges ( climate compell$ ext5sive migrations1 & ! fauna ( diff]5t regions 7 ?us br\ght into conflict4 ,! ,p]mian 0 a "t ( pron\nc$ *anges 9 plant & animal life1 & a transitional p]iod betwe5 two great eras4 ,! somb] =e/s ( ! e>li] ,c>bonif]\s1 ) _! gigantic club mosses1 7 n[ replac$ by =e/s ( cycads1 tree f]ns1 & conif]s4 ,ev5 9 ! l[] ,p]mian ! ,lepidod5dron & ,sigill>ia 7 v r>e1 & be=e ! end ( ! epo* !y & ! ,calamites also _h become ext9ct4 ,gradually ! antique types ( ! ,paleozoic fauna di$ out1 & 9 ! ,p]mian rocks are f\nd ! la/ survivors ( ! cy/oid1 ! trilobite1 & ! eurypt]id1 & ( _m long-liv$ families ( bra*iopods1 mollusks1 & o!r inv]tebrates4 ,! v5]able ,or?oc]as & ! ,goniatite l+] on ?r\gh ! epo* & into ! fir/ p]iod ( ! succe$+ era4 ,=]unn]s ( ! great ammonite family ( cephalopod mollusks n[ appe>4 ,! antique =ms ( ! e>li] ,c>bonif]\s amphibians cont9ue1 b ) _m new g5]a & a m>k$ increase 9 size4 ,a long =w>d /ep _h n[ be5 tak5 9 ! evolution ( ! v]tebrates4 ,a new & high] type1 ! reptiles1 _h appe>$1 & 9 su* numb]s & v>iety are !y f\nd 9 ! ,p]mian /rata t _! adv5t may well h occurr$ 9 a /ill e>li] epo*4 ,x w be mo/ conv5i5t to describe ! ,p]mian reptiles along ) _! desc5dants ( ! ,mesozoic4 ,,*apt] ,,xx ,,! ,,mesozoic ,) ! close ( ! ,p]mian ! _w ( animal & vegetable life _h s *ang$ t ! l9e is drawn "h :i* m>ks ! end ( ! old ord] & ! beg9n+ ( ! new & sep>ates ! ,paleozoic f ! succe$+ era1--! ,mesozoic1 ! ,middle ,age ( geological hi/ory4 ,al?\gh ! ,mesozoic era is %ort] ?an ! ,paleozoic1 z measur$ by ! ?ickness ( _! /rata1 yet its duration mu/ be reckon$ 9 millions ( ye>s4 ,its pr$om9ant life features are ! culm9ation & ! beg9n+ ( ! decl9e ( reptiles1 amphibians1 cephalopod mollusks1 & cycads1 & ! adv5t ( m>supial mammals1 birds1 teleo/ fi%es1 & angiosp]m\s plants4 ,! lead+ ev5ts ( ! long ages ( ! era we c sket* only 9 ! mo/ summ>y way4 ,! ,mesozoic comprises ?ree sy/ems1--! ,triassic1 nam$ f its ?reefold division 9 ,g]many2 ! ,jurassic1 :i* is well display$ 9 ! ,jura ,m\nta9s2 & ! ,cretace\s1 :i* conta9s ! ext5sive *alk 7,lat91 creta7 deposits ( ,europe4 ,9 ea/]n ,nor? ,am]ica ! ,mesozoic rocks are mu* less important ?an ! ,paleozoic1 = mu* ( ?is portion ( ! cont95t 0 l& dur+ ! ,mesozoic era1 & ! area ( ! ,mesozoic rocks is small4 ,9 we/]n ,nor? ,am]ica1 on ! o!r h&1 ! /rata ( ! ,mesozoic--& ( ! ,c5ozoic also--are widely spread4 ,! ,paleozoic rocks are buri$ q g5]ally f view except :]e ! m\nta9 mak+s & cont95tal uplifts ( ! ,mesozoic & ,c5ozoic h all[$ pr(\nd erosion to br+ !m to light1 z 9 deep canyons & ab\t m\nta9 axes4 ,! record ( _m ( ! mo/ important ev5ts 9 ! developm5t ( ! cont95t dur+ ! ,mesozoic & ,c5ozoic eras is f\nd 9 ! rocks ( our we/]n /ates4 ,! ,triassic & ,jurassic ,ea/]n ,nor? ,am]ica4 ,! s$im5t>y record int]rupt$ by ! ,appala*ian de=mation 0 n r5ew$ 9 ea/]n ,nor? ,am]ica until late 9 ! ,triassic4 ,h5ce dur+ ?is long int]val ! l& /ood high1 ! coa/ 0 f>!r out ?an n[1 & ov] our ,atlantic /ates geological "t 0 record$ *iefly 9 erosion =ms ( hill & pla9 :i* h long s9ce vani%$4 ,! area ( ! lat] ,triassic rocks ( ?is region1 :i* take up aga9 ! geological record1 is se5 9 ! map ( ,figure #bfj4 ,!y lie on ! upturn$ & erod$ edges ( ! old] rocks & occupy long tr\ghs runn+ = ! mo/ "p p>allel to ! ,atlantic coa/4 ,evid5tly subsid5ce 0 9 progress :]e ^! rocks 7 deposit$4 ,! ea/]n bord] ( ,appala*ia 0 n[ depress$4 ,! oldl& 0 w>p+1 & long belts ( c\ntry ly+ p>allel to ! %ore subsid$1 =m+ tr\ghs 9 :i* ?\s&s ( feet ( s$im5t n[ ga!r$4 ,^! ,triassic rocks1 :i* are *iefly s&/ones1 hold no m>9e fossils1 & h5ce 7 n laid 9 op5 arms ( ! sea4 ,b _! lay]s are (t5 ripple-m>k$1 & conta9 _m tracks ( reptiles1 impr9ts ( ra9drops1 & "s fossil wood1 :ile an occasional b$ ( %ale is fill$ ) ! rema9s ( fi%es4 ,we may conceive1 !n1 ( ! ,connecticut valley & ! l>g] tr\gh to ! s\?we/ z bas9s gradually s9k+ at a rate p]haps no fa/] ?an t ( ! ,new ,j]sey coa/ to-day1 & z gradually aggrad$ by /reams f ! neighbor+ upl&s4 ,_! broad1 s&y flats 7 ov]fl[$ by w&]+ /reams1 & :5 subsid5ce ga9$ on deposition %all[ lakes ov]spread ! alluvial pla9s4 ,p]haps n[ & !n ! bas9s became long1 bracki% e/u>ies1 ^: l[ %ores 7 swept by ! incom+ tide & 7 9 turn left b>e at its retreat to receive ! ra9 pr9ts ( pass+ %[]s & ! tracks ( ! troops ( reptiles :i* inhabit$ ^! valleys4 ,! ,triassic rocks are ma9ly r$ s&/ones1--(t5 feldspa?ic1 or arkose1 ) "s conglom]ates & %ales4 ,consid]+ ! l>ge am\nt ( feldspa?ic mat]ial 9 ^! rocks1 d y inf] t !y 7 d]iv$ f ! adjac5t cry/all9e & metamorphic rocks ( ! oldl& ( ,appala*ia1 or f ! s$im5t>y ,paleozoic rocks :i* _h be5 fold$ into m\nta9s dur+ ! ,appala*ian de=mation8 ,if f ! =m]1 0 ! dra9age ( ! nor!rn ,appala*ian m\nta9 region !n1 z n[1 ea/w>d & s\!a/w>d t[>d ! ,atlantic8 ,! ,triassic s&/ones are volum9\s1 measur+ at lea/ a mile 9 ?ickness1 & are l>gely ( co>se wa/e4 ,:at d y inf] z to ! height ( ! l&s f :i* ! wa/e 0 %$1 or ! direction ( ! oscillation :i* !y 7 !n und]go+8 ,9 ! s\!rn bas9s1 z ab\t ,ri*mond1 ,virg9ia1 are valuable b$s ( coal2 :at 0 ! physical geography ( ^! areas :5 ! coal 0 be+ =m$8 ,illu/ration3 ,fig4 #cae4 ,section ( ,triassic ,s&/ones ( ! ,connecticut ,valley ss1 s&/ones2 ll1 lava %eets2 cc1 cry/all9e igne\s & metamorphic rocks ,int]b$d$ ) ! ,triassic s&/ones are contemporane\s lava b$s :i* 7 f$ f dikes4 ,volcanic action1 :i* _h be5 rem>kably abs5t 9 ea/]n ,nor? ,am]ica dur+ ,paleozoic times1 0 well-m>k$ 9 connection ) ! w>p+ n[ 9 progress4 ,?ick intrusive %eets h also be5 driv5 9 among ! /rata1 z1 = example1 ! %eet ( ! ,palisades ( ! ,hudson1 describ$ on page #bfi4 ,! pres5t condition ( ! ,triassic s&/ones ( ! ,connecticut valley is se5 9 ,figure #cae4 ,7 ! b$s laid 9 _! pres5t attitude8 ,:at 0 ! nature ( ! de=mation :i* !y h suff]$8 ,:5 did ! intrusion ( lava %eets take place relative to ! de=mation8 ,:at effect h ^! %eets on ! pres5t topography1 & :y8 ,assum+ t ! ,triassic de=mation w5t on m rapidly ?an d5udation1 :at 0 its effect on ! topography ( ! "t8 ,are !re any ( its results rema9+ 9 ! topography ( to-day8 ,d ! ,triassic areas n[ /& high] or l[] ?an ! surr\nd+ c\ntry1 & :y8 ,h[ d ! ,triassic s&/ones & %ales comp>e 9 h>dness ) ! igne\s & metamorphic rocks ab\t !m8 ,! ,jurassic /rata are want+ ov] ! ,triassic areas & ov] all ( ea/]n ,nor? ,am]ica4 ,0 ?is region l& or sea1 an area ( erosion or s$im5tation1 dur+ ! ,jurassic p]iod8 ,9 ,new ,j]sey1 ,p5nsylvania1 & f>!r s\?we/ ! l[e/ /rata ( ! next p]iod1 ! ,cretace\s1 re/ on ! erod$ edges ( ! e>li] rocks4 ,! surface on :i* !y lie is worn s ev5 t we mu/ believe t at ! op5+ ( ! ,cretace\s ! oldl& ( ,appala*ia1 includ+ ! ,triassic areas1 _h be5 baselevel$ at lea/ ne> ! coa/4 ,:51 !re=e1 did ! de=mation ( ! ,triassic rocks occur8 ,we/]n ,nor? ,am]ica4 ,triassic /rata infold$ 9 ! ,si]ra ,nevada ,m\nta9s c>ry m>9e fossils & rea* a ?ickness ( ne>ly five ?\s& feet4 ,cali=nia 0 !n "u wat]1 & ! site ( ! ,si]ra 0 a subsid+ tr\gh sl[ly fill+ ) wa/e f ! ,great ,bas9 l& to ! ea/4 ,ov] a long belt :i* rea*es f ,wyom+ across ,colorado into ,new ,mexico no ,triassic s$im5ts are f\nd1 nor is !re any evid5ce t !y 7 ev] pres5t2 h5ce ?is area 0 high l& suff]+ erosion dur+ ! ,triassic4 ,on ea* side ( x1 9 ea/]n ,colorado & ab\t ! ,black ,hills1 9 we/]n ,texas1 9 ,utah1 ov] ! site ( ! ,wasat* ,m\nta9s1 & s\?w>d into ,arizona ov] ! plateaus tr5*$ by ! ,colorado ,riv]1 are l>ge areas ( ,triassic rocks1 s&/ones *iefly1 ) "s rock salt & gypsum4 ,fossils are v r>e & none ( !m m>9e4 ,"h1 !n1 lay broad %all[ lakes (t5 salt1 & w>p$ bas9s1 9 :i* ! wa/e ( ! adjac5t upl&s ga!r$4 ,to ?is sy/em belong ! s&/ones ( ! ,g>d5 ( ! ,gods 9 ,colorado1 :i* lat] e>? movem5ts h upturn$ ) ! uplift$ m\nta9 flanks4 ,! ,jurassic 0 m>k$ ) v>i$ oscillations & wide *anges 9 ! outl9e ( sea & l&4 ,jurassic %ales ( imm5se ?ickness--n[ metamorphos$ into slates--are f\nd infold$ into ! ,si]ra ,nevada ,m\nta9s4 ,h5ce dur+ ,jurassic times ! ,si]ra tr\gh cont9u$ to subside1 & enorm\s deposits ( mud 7 wa%$ into x f ! l& ly+ to ! ea/4 ,contemporane\s lava fl[s int]b$d$ ) ! /rata %[ t volcanic action accompani$ ! d[nw>p1 & t molt5 rock 0 driv5 upw>d ?r\gh fissures 9 ! cru/ & outspread ov] ! sea floor 9 %eets ( lava4 ,! ,si]ra de=mation4 ,ev] s9ce ! middle ( ! ,silurian1 ! ,si]ra tr\gh _h be5 s9k+1 ?\gh no d\bt ) halts & int]ruptions1 until x conta9$ ne>ly tw5ty-five ?\s& feet ( s$im5t4 ,at ! close ( ! ,jurassic x yield$ to lat]al pressure & ! va/ pile ( /rata 0 crumpl$ & upheav$ into t[]+ m\nta9s4 ,! ,mesozoic muds 7 h>d5$ & squeez$ into slates4 ,! rocks 7 wr5*$ & brok51 & und]gr\nd wat]s began ! "w ( fill+ _! fissures ) gold-be>+ qu>tz1 :i* 0 yet to wait millions ( ye>s be=e ! arrival ( man to m9e x4 ,imm5se bodies ( molt5 rock 7 intrud$ into ! cru/ z x suff]$ de=mation1 & ^! appe> 9 ! l>ge areas ( granite :i* ! lat] d5udation ( ! range has br\ght to light4 ,! same movem5ts probably uplift$ ! rocks ( ! ,coa/ ,range 9 a *a9 ( isl&s4 ,! :ole we/]n "p ( ! cont95t 0 rais$ & its seas & lakes 7 = ! mo/ "p dra9$ away4 ,! ,briti% ,isles4 ,! ,triassic /rata ( ! ,briti% ,isles are cont95tal1 & include breccia b$s ( cem5t$ talus1 deposits ( salt & gypsum1 & s&/ones ^: r\nd$ & poli%$ gra9s are ^? ( ! w9d-bl[n s&s ( des]ts4 ,9 ,triassic times ! ,briti% ,isles 7 "p ( a des]t ext5d+ ov] mu* ( nor?we/]n ,europe4 ,! ,cretace\s ,! ?ird great sy/em ( ! ,mesozoic includes _m =mations1 m>9e & cont95tal1 :i* record a long & complicat$ hi/ory m>k$ by great oscillations ( ! cru/ & wide *anges 9 ! outl9es ( sea & l&4 ,e>ly ,cretace\s4 ,9 ea/]n ,nor? ,am]ica ! l[e/ ,cretace\s s]ies comprises fre%-wat] =mations :i* are trac$ f ,nantucket across ,m>?a's ,v9ey>d & ,long ,isl&1 & ?r\gh ,new ,j]sey s\?w>d into ,georgia4 ,!y re/ uncon=mably on ! ,triassic s&/ones & ! old] rocks ( ! region4 ,! ,atlantic %ore l9e 0 /ill f>!r out ?an n[ 9 ! nor!rn /ates4 ,aga91 z dur+ ! ,triassic1 a w>p+ ( ! cru/ =m$ a long tr\gh p>allel to ! coa/ & to ! ,appala*ian ridges1 b cut (f f ! sea2 & "h ! cont95tal deposits ( ! e>ly ,cretace\s 7 laid4 ,along ! ,gulf ( ,mexico ! same s]ies 0 deposit$ "u l conditions ov] ! area kn[n z ! ,mississippi embaym5t1 rea*+ f ,georgia nor?we/w>d into ,t5nessee & !nce across into ,arkansas & s\?w>d into ,texas4 ,9 ! ,s\?we/ ! subsid5ce cont9u$ until ! transgress+ sea cov]$ mo/ ( ,mexico & ,texas & ext5d$ a gulf nor?w>d into ,kansas4 ,9 its w>m & quiet wat]s lime/ones accumulat$ to a dep? ( f "o ?\s& to five ?\s& feet 9 ,texas1 & ( m ?an t5 ?\s& feet 9 ,mexico4 ,mean:ile ! l[l&s1 :]e ! ,great ,pla9s are n[1 receiv$ cont95tal deposits2 coal swamps /ret*$ f we/]n ,montana into ,briti% ,columbia4 ,! ,middle ,cretace\s4 ,?is 0 a l& epo*4 ,! e>ly ,cretace\s sea retir$ f ,texas & ,mexico1 = its s$im5ts are ov]la9 uncon=mably by =mations ( ! ,upp] ,cretace\s4 ,s long 0 ! "t gap betwe5 ! two s]ies t no species f\nd 9 ! "o occurs 9 ! o!r4 ,! ,upp] ,cretace\s4 ,!re n[ began "o ( ! mo/ rem>kable ev5ts 9 all geological hi/ory1--! great ,cretace\s subsid5ce4 ,its e>li] w>p+s 7 record$ 9 cont95tal deposits1--wide %eets ( s&/one1 %ale1 & "s coal1--:i* 7 spread f ,texas to ,briti% ,columbia4 ,^! cont95tal deposits are ov]la9 by a succession ( m>9e =mations ^: va/ area is %[n on ! map1 ,figure #bfj4 ,we may inf] t z ! depression ( ! cont95t cont9u$ ! sea came 9 f> & wide ov] ! coa/ l&s & ! pla9s worn l[ dur+ ! previ\s epo*s4 ,upp] ,cretace\s =mations %[ t s\? ( ,new ,engl& ! wat]s ( ! ,atlantic some:at ov]lapp$ ! cry/all9e rocks ( ! ,pi$mont ,belt & spread _! wa/e ov] ! subm]g$ coa/al pla94 ,! ,gulf ( ,mexico aga9 cov]$ ! ,mississippi embaym5t1 rea*+ z f> nor? z s\!rn ,ill9ois1 & ext5d$ ov] ,texas4 ,a m$it]ranean sea n[ /ret*$ f ! ,gulf to ! arctic regions & f c5tral ,i[a to ! ea/]n %ore ( ! ,great ,bas9 l& at ab\t ! longitude ( ,salt ,lake ,city1 ! ,colorado ,m\nta9s ris+ f x 9 a *a9 ( isl&s4 ,along ) m9or oscillations !re 7 laid 9 ! int]ior sea v>i\s =mations ( s&/ones1 %ales1 & lime/ones1 & f ,kansas to ,s\? ,dakota b$s ( :ite *alk %[ t ! cle>1 w>m wat]s sw>m$ at times ) =am9if]al life ^: dis9tegrat+ microscopic %ells accumulat$ 9 ?is r>e deposit4 ,illu/ration3 ,fig4 #caf4 ,hypo!tical ,map ( ,upp] ,cretace\s ,epicont95tal ,seas ,%ad$ areas1 probable seas2 brok5 l9es1 approximate %ore l9es ,illu/ration3 ,fig4 #cag4 ,=am9if]a f ,cretace\s ,*alk1 ,i[a ,at ?is epo* a wide sea1 int]rupt$ by v>i\s isl&s1 /ret*$ across ,eurasia f ,wales & we/]n ,spa9 to ,*9a1 & spread s\?w>d ov] mu* ( ! ,sah>a4 ,to ! we/ its wat]s 7 cle> & on its floor ! crumbl$ rema9s ( =am9if]s ga!r$ 9 heavy accumulations ( calc>e\s ooze1--! :ite *alk ( ,france & ,engl&4 ,sea ur*9s 7 also abundant1 & sponges contribut$ _! spicules to =m nodules ( fl9t4 ,! ,l>amie4 ,! clos+ /age ( ! ,cretace\s 0 m>k$ 9 ,nor? ,am]ica by a sl[ uplift ( ! l&4 ,z ! int]ior sea gradually )drew1 ! w>p+ bas9s ( its floor 7 fill$ ) wa/e f ! ris+ l&s ab\t !m1 & ov] ?is wide area !re 7 spread cont95tal deposits 9 fre%-wat] lakes l ! ,great ,lakes ( ! pres5t1 9 bracki% e/u>ies1 & 9 riv] pla9s1 :ile occasional oscillations n[ & aga9 let 9 ! sea4 ,!re 7 va/ m>%es 9 :i* !re accumulat$ ! l>g] "p ( ! valuable coal seams ( ! ,we/4 ,! ,l>amie is ! coal-be>+ s]ies ( ! ,we/1 z ! ,p5nsylvanian is ( ! ea/]n "p ( our c\ntry4 ,! ,rocky ,m\nta9 de=mation4 ,at ! close ( ! ,cretace\s we ent] ^u an epo* ( m\nta9-mak+ f> m ext5sive ?an any :i* ! cont95t _h witness$4 ,! long belt ly+ we/ ( ! anci5t axes ( ! ,colorado ,isl&s & ea/ ( ! ,great ,bas9 l& _h be5 an area ( deposition = _m ages1 & 9 its subsid+ tr\ghs ,paleozoic & ,mesozoic s$im5ts _h ga!r$ to ! dep? ( _m ?\s& feet4 ,& n[ f ,mexico well-nigh to ! ,arctic ,ocean ?is belt yield$ to lat]al pressure4 ,! ,cretace\s lime/ones ( ,mexico 7 fold$ into l(ty m\nta9s4 ,a massive range 0 upfold$ :]e ! ,wasat* ,m\nta9s n[ are1 & v>i\s ranges ( ! ,rockies 9 ,colorado & o!r /ates 7 upridg$4 ,h[ev] sl[ly ^! de=mations 7 effect$ !y 7 no d\bt accompani$ by _w-%ak+ e>?quakes1 & x is kn[n t volcanic eruptions took place on a magnific5t scale4 ,outfl[s ( lava occurr$ along ! ,wasat*1 ! laccoli?s ( ! ,h5ry ,m\nta9s 7p4 #bga7 7 =m$1 :ile ! great masses ( igne\s rock :i* con/itute ! cores ( ! ,spani% ,peaks 7p4 #bga7 & o!r we/]n m\nta9s 7 ?ru/ up amid ! /rata4 ,! high plateaus f :i* _m ( ^! ranges rise _h n yet be5 uplift$1 & ! bases ( ! m\nta9s probably /ood ne> ! level ( ! sea4 ,nor? ,am]ica 0 n[ well-nigh complet$4 ,! m$it]ranean seas :i* s (t5 _h occupi$ ! he>t ( ! l& 7 done away )1 & ! cont95t /ret*$ unbrok5 f ! foot ( ! ,si]ras on ! we/ to ! ,fall ,l9e ( ! ,atlantic coa/al pla9 on ! ea/4 ,! ,mesozoic p5epla94 ,! imm5se ?ickness ( ! ,mesozoic =mations conveys to our m9ds "s idea ( ! va/ l5g? ( "t involv$ 9 ! sl[ progress ( its successive ages4 ,! same lesson is taught z pla9ly by ! am\nt ( d5udation :i* ! l&s suff]$ dur+ ! era4 ,! beg9n+ ( ! ,mesozoic saw a sy/em ( l(ty m\nta9 ranges /ret*+ f ,new ,york into c5tral ,alabama4 ,! end ( ?is long era f\nd "h a wide p5epla9 cross$ by sluggi% w&]+ riv]s & ov]look$ by deta*$ hills z yet unr$uc$ to ! g5]al level4 ,! ,mesozoic era 0 long en\gh = ! ,appala*ian ,m\nta9s1 upridg$ at its beg9n+1 to h be5 wea!r$ & worn away & c>ri$ gra9 by gra9 to ! sea4 ,! same pla9 ext5d$ ov] s\!rn ,new ,engl&4 ,! ,taconic range1 uplift$ p>tially at lea/ at ! close ( ! ,ordovician1 & ! block m\nta9s ( ! ,triassic1 toge!r ) ! pre-,cambrian m\nta9s ( anci5t ,appala*ia1 _h n[ all be5 worn to a common level ) ! ,allegh5y ranges4 ,! ,mesozoic p5epla9 has be5 upw>p$ by lat] cru/al movem5ts & has suff]$ pr(\nd erosion1 b ! remnants ( x :i* rema9 on ! upl& ( s\!rn ,new ,engl& & ! ev5 summits ( ! ,allegh5y ridges suffice to prove t x once exi/$4 ,! age ( ! ,mesozoic p5epla9 is det]m9$ f ! fact t ! l[] ,t]ti>y s$im5ts 7 deposit$ on its ev5 surface :5 at ! close ( ! era ! p5epla9 0 depress$ along its edges b5ea? ! sea4 ,life ( ! ,mesozoic ,plant life ( ! ,triassic & ,jurassic4 ,! ,c>bonif]\s =e/s ( lepidod5drons & sigill>ids _h n[ vani%$ f ! e>?4 ,! upl&s 7 clo!d ) conif]s1 l ! ,arauc>ian p9es ( ,s\? ,am]ica & ,au/ralia4 ,d5se =e/s ( tree f]ns ?rove 9 moi/ regions1 & canebrakes ( horsetails ( mod]n type1 b ) /ems rea*+ f\r in*es 9 ?ickness1 bord]$ ! lagoons & m>%es4 ,cycads 7 exce$+ly abundant4 ,^! gymnosp]ms1 relat$ to ! p9es & spruces 9 /ructure & fruit+1 b palmlike 9 _! foliage1 & uncoil+ _! long leaves aft] ! mann] ( f]ns1 culm9at$ 9 ! ,jurassic4 ,f ! view po9t ( ! botani/ ! ,mesozoic is ! ,age ( ,cycads1 & aft] ?is era !y gradually decl9e to ! small numb] ( species n[ exi/+ 9 tropical latitudes4 ,illu/ration3 ,fig4 #cah4 ,a ,liv+ ,cycad ( ,au/ralia ,illu/ration3 ,fig4 #cai4 ,/em ( a ,mesozoic ,cycad ,plant life ( ! ,cretace\s4 ,9 ! ,l[] ,cretace\s ! woodl&s cont9u$ ( mu* ! same type z dur+ ! ,jurassic4 ,! =]unn]s n[ appe>$ ( ! mod]n dicotyls 7plants ) two se$ leaves71 & 9 ! ,middle ,cretace\s ! monocotyl$on\s gr\p ( palms came 94 ,palms are s l cycads t we may reg>d !m z ! desc5dants ( "s cycad type4 ,9 ! ,upp] ,cretace\s1 cycads become r>e4 ,! highe/ types ( fl[]+ plants ga9 a complete asc5d5cy1 & =e/s ( mod]n aspect cov] ! cont95t f ! ,gulf ( ,mexico to ! ,arctic ,ocean4 ,among ! k9ds ( =e/ trees ^: rema9s are f\nd 9 ! cont95tal deposits ( ! ,cretace\s are ! magnolia1 ! myrtle1 ! laurel1 ! fig1 ! tulip tree1 ! *e/nut1 ! oak1 bee*1 elm1 popl>1 will[1 bir*1 & maple4 ,=e/s ( ,eucalyptus grew along ! coa/ ( ,new ,engl&1 & palms on ! ,pacific %ores ( ,briti% ,columbia4 ,sequoias ( _m v>ieties rang$ f> into nor!rn ,canada4 ,9 nor!rn ,gre5l& !re 7 luxuriant =e/s ( magnolias1 figs1 & cycads2 & a simil> flora has be5 dis9t]r$ f ! ,cretace\s rocks ( ,alaska & ,spitzb]g54 ,evid5tly ! l&s )9 ! ,arctic ,circle enjoy$ a w>m & g5ial climate1 z !y _h done dur+ ! ,paleozoic4 ,gre5l& _h ! temp]ature ( ,cuba & s\!rn ,florida1 & ! "t 0 yet f> di/ant :5 x 0 to be wrapp$ 9 glaci] ice4 ,illu/ration3 ,fig4 #cbj4 ,a ,jurassic ,long-,tail$ ,cru/acean ,inv]tebrates4 ,dur+ ! long succession ( ! ages ( ! ,mesozoic1 ) _! va/ geographical *anges1 !re 7 _m & great *anges 9 organisms4 ,species 7 replac$ aga9 & aga9 by o!rs bett] fitt$ to ! *ang+ environm5t4 ,dur+ ! ,l[] ,cretace\s alone !re 7 no less ?an six successive *anges 9 ! faunas :i* inhabit$ ! lime/one-mak+ sea :i* !n cov]$ ,texas4 ,we %all disreg>d ^! *anges = ! mo/ "p 9 describ+ ! life ( ! era1 & %all conf9e our view to "s ( ! mo/ important advances made 9 ! lead+ types4 ,/romatopora h disappe>$4 ,protozoans & sponges are exce$+ly abundant1 & all contribute to ! mak+ ( ,mesozoic /rata4 ,corals h assum$ a m mod]n type4 ,sea ur*9s h become pl5tiful2 cr9oids ab\nd until ! ,cretace\s1 :]e !y beg9 _! decl9e to _! pres5t humble /ation4 ,illu/ration3 ,fig4 #cba4 ,a ,fossil ,crab ,illu/ration3 ,fig4 #cbb4 ,cretace\s ,mollusks ,a1 ,o/rea 7oy/]72 ,b1 ,exogyra2 ,c4 ,grypha ,trilobites & eurypt]ids are gone4 ,t5-foot$ cru/aceans ab\nd ( ! primitive long-tail$ type 7repres5t$ by ! lob/] & ! crayfi%71 & 9 ! ,jurassic !re appe>s ! mod]n %ort-tail$ type repres5t$ by ! crabs4 ,! latt] type is high] 9 organization & n[ f> m common4 ,9 its embryological developm5t x passes ?r\gh ! long-tail$ /age2 connect+ l9ks 9 ! ,mesozoic also indicate t ! y\ng] type is ! (f%oot ( ! old]4 ,insects evolve along div]se l9es1 giv+ rise to beetles1 ants1 bees1 & flies4 ,bra*iopods h dw9dl$ greatly 9 ! numb] ( _! species1 :ile mollusks h correspond+ly increas$4 ,! great oy/] family dates f "h4 ,cephalopods are n[ to h _! day4 ,! ar*aic ,or?oc]as l+]s on into ! ,triassic & becomes ext9ct1 b a rem>kable developm5t is n[ at h& = ! m highly organiz$ desc5dants ( ?is anci5t l9e4 ,we h notic$ t 9 ! ,devonian ! sutures ( "s ( ! *amb]$ %ells become angl$1 evolv+ ! ,goniatite type4 ,! sutures n[ become lob$ & corrugat$ 9 ,c]atites4 ,! process 0 c>ri$ /ill f>!r1 & ! sutures 7 elaborately frill$ 9 ! great ord] ( ! ,ammonites4 ,x 0 9 ! ,jurassic t ! ,ammonites rea*$ _! height4 ,no fossils are m abundant or *>act]i/ic ( _! age4 ,great banks ( _! %ells =m$ b$s ( lime/one 9 w>m seas ! _w ov]4 ,illu/ration3 ,fig4 #cbc4 ,c]atites ,illu/ration3 ,fig4 #cbd4 ,an ,ammonite ,a portion ( ! %ell is remov$ to %[ frill+ ( suture ,illu/ration3 ,fig4 #cbe4 ,slab ( ,rock cov]$ ) ,ammonites1--a ,bit ( a ,mesozoic ,sea ,bottom ,illu/ration3 ,fig4 #cbf4 ,repres5tative ,species ( ,diff]5t ,families ( ,ammonites ,! ammonite /em bran*$ into a mo/ luxuriant v>iety ( =ms4 ,! typical =m 0 closely coil$ l a nautilus4 ,9 o!rs ! coil 0 m or less op51 or ev5 erect$ into a spiral4 ,"s 7 hook-%ap$1 & !re 7 memb]s ( ! ord] 9 :i* ! %ell 0 /raight1 & yet reta9$ all ! int]nal /ructures ( its k9d4 ,at ! end ( ! ,mesozoic ! entire tribe ( ammonites became ext9ct4 ,! ,belemnite 7,greek1 belemnon1 a d>t7 is a di/9ctly high] type ( cephalopod :i* appe>$ 9 ! ,triassic1 became num]\s & v>i$ 9 ! ,jurassic & ,cretace\s1 & di$ out e>ly 9 ! ,t]ti>y4 ,l ! squids & cuttlefi%1 ( :i* x 0 ! prototype1 x _h an int]nal calc>e\s %ell4 ,?is consi/$ ( a *amb]$ & siphuncl$ cone1 ^: po9t 0 %ea!d 9 a long solid gu>d some:at l a d>t4 ,! animal c>ri$ an ink sac1 & no d\bt us$ x z t ( ! mod]n cuttlefi% is us$1--to d>k5 ! wat] & make easy an escape f foes4 ,belemnites h sometimes be5 sket*$ ) fossil sepia1 or india ink1 f _! own ink sacs4 ,9 ! belemnites & _! desc5dants1 ! squids & cuttlefi%1 ! cephalopods made ! radical *ange f ext]nal to ! int]nal %ell4 ,!y ab&on$ ! def5sive sy/em ( w>f>e & boldly took up ! (f5sive4 ,no d\bt1 l _! desc5dants1 ! belemnites 7 exce$+ly active & voraci\s creatures4 ,illu/ration3 ,fig4 #cbg4 ,int]nal ,%ell ( ,belemnite ,fi%es & amphibians4 ,9 ! ,triassic & ,jurassic1 little progress 0 made among ! fi%es1 & ! ganoid 0 /ill ! lead+ type4 ,9 ! ,cretace\s ! teleo/s1 or bony fi%es1 made _! appe>ance1 :ile ganoids decl9$ t[>d _! pres5t subord9ate place4 ,! amphibians culm9at$ 9 ! ,triassic1 "s be+ =midable creatures z l>ge z alligators4 ,!y 7 /ill ( ! primitive ,paleozoic types4 ,_! pygmy desc5dants ( m mod]n types are n f\nd until lat]1 salam&]s appe>+ fir/ 9 ! ,cretace\s1 & frogs at ! beg9n+ ( ! ,c5ozoic4 ,no rema9s ( amphibians h be5 discov]$ 9 ! ,jurassic4 ,d y inf] f ?is t !re 7 none 9 exi/5ce at t "t8 ,reptiles ( ! ,mesozoic ,! great ord] ( ,reptiles made its adv5t 9 ! ,p]mian1 culm9at$ 9 ! ,triassic & ,jurassic1 & began to decl9e 9 ! ,cretace\s4 ,! advance f ! amphibian to ! reptile 0 a long =w>d /ep 9 ! evolution ( ! v]tebrates4 ,9 ! reptile ! v]tebrate skeleton n[ became completely ossifi$4 ,gills 7 ab&on$ & brea?+ 0 by lungs alone4 ,! developm5t ( ! individual f ! egg to maturity 0 un9t]rupt$ by any metamorphosis1 su* z t ( ! frog :5 x passes f ! tadpole /age4 ,yet 9 advanc+ f ! amphibian to ! reptile ! evolution ( ! v]tebrate 0 f> f f9i%$4 ,! cold-blood$1 clumsy & sluggi%1 small-bra9$ & un9tellig5t reptile is z f> inf]ior to ! high] mammals1 ^: day 0 /ill to come1 z x is sup]ior to ! amphibian & ! fi%4 ,! reptiles ( ! ,p]mian1 ! e>lie/ kn[n1 7 mu* l liz>ds 9 =m ( body4 ,con/itut+ a transition type betwe5 ! amphibians on ! "o h&1 & bo? ! high] reptiles & ! mammals on ! o!r1 !y reta9$ ! ar*aic biconcave v]tebra ( ! fi% & 9 "s cases ! p]si/5t noto*ord1 :ile "s ( !m1 ! !romorphs1 possess$ *>act]s ally+ !m ) mammals4 ,9 ^! ! skull 0 rem>kably simil> to t ( ! c>nivores1 or fle%-eat+ mammals1 & ! tee?1 unlike ! tee? ( any lat] reptiles1 7 divisible into incisors1 can9es1 & mol>s1 z are ! tee? ( mammals 7,fig4 #cbh74 ,illu/ration3 ,fig4 #cbh4 ,skull ( a ,p]mian ,!romorph ,at ! op5+ ( ! ,mesozoic era reptiles 7 ! mo/ highly organiz$ & p[]ful ( any animals on ! e>?4 ,new ranges ( cont95tal ext5t 7 op5$ to !m1 food 0 abundant1 ! climate 0 cong5ial1 & !y n[ bran*$ into v _m div]se types :i* occupi$ & rul$ all fields1--! l&1 ! air1 & ! sea4 ,! ,mesozoic 0 ! ,age ( ,reptiles4 ,! ance/ry ( surviv+ reptilian types4 ,we w consid] fir/ ! evolution ( ! few reptilian types :i* h surviv$ to ! pres5t4 ,crocodiles1 ! highe/ ( exi/+ reptiles1 are a v anci5t ord]1 dat+ back to ! l[] ,jurassic1 & traceable to e>li] ance/ral1 g5]aliz$ =ms1 f :i* sprang sev]al o!r ord]s also4 ,turtles & tortoises are n f\nd until ! e>ly ,jurassic1 :5 !y already possess$ ! peculi> *>act]i/ics :i* set !m (f s %>ply f o!r reptiles4 ,!y seem to h liv$ at fir/ 9 %all[ wat] & 9 swamps1 & x is n until aft] ! end ( ! ,mesozoic t "s ( ! ord] became adapt$ to life on ! l&4 ,! l>ge/ ( all kn[n turtles1 ,ar*elon1 ^: home 0 ! great int]ior ,cretace\s sea1 0 fully a doz5 feet 9 l5g? & mu/ h weigh$ at lea/ two tons4 ,! skull alone is a y>d long4 ,liz>ds & snakes d n appe> until aft] ! close ( ! ,mesozoic1 al?\gh _! ance/ral l9es may be foll[$ back into ! ,cretace\s4 ,we w n[ describe "s ( ! highly specializ$ ord]s peculi> to ! ,mesozoic4 ,l& reptiles4 ,! d9osaurs 7t]rible reptiles7 are an extremely v>i$ ord] :i* 7 ma/]s ( ! l& f ! late ,trias until ! close ( ! ,mesozoic era4 ,"s 7 f> l>g] ?an elephants1 "s 7 z small z cats2 "s walk$ on all f\rs1 "s 7 bip$al2 "s f$ on ! luxuriant tropical foliage1 & o!rs on ! fle% ( weak] reptiles4 ,!y may be class$ 9 ?ree divisions1--! fle%-eat+ d9osaurs1 ! reptile-foot$ d9osaurs1 & ! beak$ d9osaurs1--! latt] two divisions be+ h]bivor\s4 ,! fle%-eat+ d9osaurs are ! olde/ kn[n division ( ! ord]1 & _! *>act]i/ics are %[n 9 ,figure #cbi4 ,z a class1 reptiles are egg lay]s 7ovip>\s72 b "s ( ! fle%-eat+ d9osaurs are kn[n to h be5 vivip>\s1 i4e4 to h br\ght =? _! "y alive4 ,?is gr\p 0 ! longe/-liv$ ( any ( ! ?ree1 beg9n+ 9 ! ,trias & cont9u+ to ! close ( ! ,mesozoic era4 ,illu/ration3 ,fig4 #cbi4 ,c]atosaurus ,contra/ ! small =e limbs1 us$ only = grasp+1 ) ! p[]ful h9d limbs on :i* ! animal /alk$ ab\t4 ,"s ( ! species ( ?is gr\p seem to h be5 able to progress by leap+ 9 kang>oo fa%ion4 ,notice ! %>p claws1 ! pond]\s tail1 & ! skull set at "r angles ) ! sp9al column4 ,! limb bones are holl[4 ,! c]atosaurs rea*$ a l5g? ( "s fifte5 feet1 & 7 n uncommon 9 ,colorado & ! we/]n l&s 9 ,jurassic times4 ,illu/ration3 ,fig4 #ccj4 ,diplodocus ,! reptile-foot$ d9osaurs 7,sauropoda7 include "s ( ! bigge/ brutes :i* ev] trod ! gr\nd4 ,"o ( ! l>ge/1 ^: rema9s are f\nd entomb$ 9 ! ,jurassic rocks ( ,wyom+ & ,colorado1 is %[n 9 ,figure #ccj4 ,note ! five digits on ! h9d feet1 ! quadrup$al gait1 ! enorm\s /ret* ( neck & tail1 ! small head align$ ) ! v]tebral column4 ,diplodocus 0 fully sixty-five feet long & mu/ h weigh$ ab\t tw5ty tons4 ,! ?igh bones ( ! ,sauropoda are ! l>ge/ bones :i* ev] grew4 ,t ( a g5us alli$ to ! ,diplodocus measures six feet & eight in*es1 & ! total l5g? ( ! animal mu/ h be5 n f> f eighty feet1 ! l>ge/ l& animal kn[n4 ,! ,sauropoda became ext9ct :5 _! haunts along ! riv]s & lakes ( ! we/]n pla9s ( ,jurassic times 7 invad$ by ! ,cretace\s int]ior sea4 ,! beak$ d9osaurs 7,pr$5tata7 7 di/+ui%$ by a beak %ea!d ) horn c>ri$ 9 front ( ! too?-set jaw1 & us$1 we may imag9e1 9 /ripp+ ! leaves & twigs ( trees & %rubs4 ,we may notice only two ( ! mo/ int]e/+ types4 ,illu/ration3 ,fig4 #cca4 ,/egosaurus ,/egosaurus 7plat$ reptile7 takes its "n f ! d\ble r[ ( bony plates arrang$ along its back4 ,! p[]ful tail 0 arm$ ) long sp9es1 & ! ?ick sk9 0 def5d$ ) irregul> bits ( bone implant$ 9 x4 ,! bra9 ( ! /egosaur 0 small] ?an t ( any l& v]tebrate1 :ile 9 ! sacrum ! n]ve canal 0 enl>g$ to t5 times ! capacity ( ! bra9 cavity ( ! skull4 ,despite _! feeble wits1 ?is well-armor$ family liv$ on ?r\gh millions ( ye>s :i* int]v5$ betwe5 _! appe>ance1 at ! op5+ ( ! ,jurassic1 & ! close ( ! ,cretace\s1 :5 !y became ext9ct4 ,a less /upid brute ?an ! /egosaur 0 ,tric]atops1 ! d9osaur ( ! ?ree horns1--"o horn c>ri$ on ! nose1 & a massive pair set ov] ! eyes 7,fig4 #ccb74 ,note ! enorm\s w$ge-%ap$ skull1 ) its %>p beak1 & ! hood beh9d resembl+ a fireman's helmet4 ,tric]atops 0 fully tw5ty-five feet long1 & ( twice ! bulk ( an elephant4 ,! family appe>$ 9 ! ,upp] ,cretace\s & became ext9ct at its close4 ,_! bones are f\nd buri$ 9 ! fre%-wat] deposits ( ! "t f ,colorado to ,montana & ea/w>d to ! ,dakotas4 ,illu/ration3 ,fig4 #ccb4 ,re/oration ( ,tric]atops ,by c\rtesy ( ! ,am]ican ,museum ( ,natural ,hi/ory ,m>9e reptiles4 ,9 ! ocean1 reptiles occupi$ ! place n[ held by ! aquatic mammals1 su* z :ales & dolph9s1 & _! =m & /ructure 7 simil>ly modifi$ to suit _! environm5t4 ,9 ! ,i*?yosaurus 7fi% reptile71 = example1 ! body 0 fi%like 9 =m1 ) %ort neck & l>ge1 po9t$ head 7,fig4 #ccc74 ,illu/ration3 ,fig4 #ccc4 ,i*?yosaurus ,a p[]ful tail1 ^: flukes 7 set v]tical1 & ! l[] "o ( :i* 0 v]tebrat$1 s]v$ z propell]1 :ile a l>ge dorsal f9 0 develop$ z a cutwat]4 ,! primitive biconcave v]tebr ( ! fi% & ( ! e>ly l& v]tebrates 7 reta9$1 & ! limbs deg5]at$ into %ort paddles4 ,! sk9 ( ! i*?yosaur 0 smoo? l t ( a :ale1 & its food 0 l>gely fi% & cephalopods1 z ! fossil cont5ts ( its /oma* prove4 ,^! sea mon/]s disport$ along ! ,pacific %ore ov] nor!rn ,cali=nia 9 ,triassic times1 & ! bones ( imm5se memb]s ( ! family occur 9 ! ,jurassic /rata ( ,wyom+4 ,l :ales & seals1 ! i*?yosaurs 7 desc5d$ f l& v]tebrates :i* _h become adapt$ to a m>9e habitat4 ,illu/ration3 ,fig4 #ccd4 ,plesiosaurus ,plesiosaurs 7 ano!r ord] :i* rang$ ?r\gh\t ! ,mesozoic4 ,desc5d$ f small amphibi\s animals1 !y lat] includ$ great m>9e reptiles1 *>act]iz$ 9 ! typical g5us by long neck1 snakelike head1 & imm5se paddles4 ,!y swam 9 ! ,cretace\s int]ior sea ( we/]n ,nor? ,am]ica4 ,illu/ration3 ,fig4 #cce4 ,re/oration ( a ,mosasaur ,mosasaurs belong to ! same ord] z d snakes & liz>ds1 & are an (f%oot ( ! same ance/ral l9e ( l& reptiles4 ,^! snakelike creatures--:i* measur$ z mu* z =ty-five feet 9 l5g?--ab\nd$ 9 ! ,cretace\s seas4 ,!y _h l>ge conical tee?1 & _! limbs _h become /\t paddles4 ,! l[] jaw ( ! mosasaur 0 jo9t$2 ! quadrate bone1 :i* 9 all reptiles connects ! bone ( ! l[] jaw ) ! skull1 0 movable1 & z 9 snakes ! l[] jaw c\ld be us$ 9 ?ru/+ prey d[n ! ?roat4 ,! family became ext9ct at ! end ( ! ,mesozoic1 & left no desc5dants4 ,"o may imitate ! movem5t ( ! l[] jaw ( ! mosasaur by ext5d+ ! arms1 clasp+ ! h&s1 & b5d+ ! elb[s4 ,fly+ reptiles4 ,! atmosph]e1 :i* _h hi!rto be5 t5ant$ only by insects1 0 fir/ conqu]$ by ! v]tebrates 9 ! ,mesozoic4 ,pt]osaurs1 w+$ reptiles1 ^: :ole organism 0 adapt$ = flight ?r\gh ! air1 appe>$ 9 ! ,jurassic & pass$ (f ! /age ( exi/5ce be=e ! end ( ! ,cretace\s4 ,! bones 7 holl[1 z are ^? ( birds4 ,! /]num1 or brea/bone1 0 giv5 a keel = ! atta*m5t ( ! w+ muscles4 ,! fif? f+]1 prodigi\sly l5g!n$1 0 turn$ backw>d to support a membrane :i* 0 atta*$ to ! body & ext5d$ to ! base ( ! tail4 ,! o!r f+]s 7 free1 & arm$ ) %>p & delicate claws1 z %[n 9 ,figures #ccf & #ccg4 ,illu/ration3 ,fig4 #ccf4 ,re/oration ( a ,pt]osaur ,illu/ration3 ,fig4 #ccg4 ,skeletons ( ,pt]osaur ,orni?o/oma1 ,a1 & ( ! ,condor1 ,b ,aft] ,lucas ,^! dragons ( ! air v>i$ greatly 9 size2 "s 7 z small z sp>r[s1 :ile o!rs surpass$ 9 /ret* ( w+ ! l>ge/ birds ( ! pres5t day4 ,!y may be divid$ into two gr\ps4 ,! e>lie/ gr\p comprises g5]a ) jaws set ) tee?1 & ) long tails sometimes provid$ ) a rudd]like expansion at ! end4 ,9 _! successors ( ! lat] gr\p ! tail _h become %ort1 & 9 "s ( ! g5]a ! tee? _h disappe>$4 ,among ! late/ ( ! fly+ reptiles 0 ,orni?o/oma 7bird beak71 ! l>ge/ creature :i* ev] flew1 & ^: rema9s are imb$d$ 9 ! (f%ore deposits ( ! ,cretace\s sea :i* held sway ov] our we/]n pla9s4 ,orni?o/oma's spread ( w+s 0 tw5ty feet4 ,its bones 7 a m>vel ( lightness1 ! entire skeleton1 ev5 9 its petrifi$ condition1 n weigh+ m ?an five or six p\nds4 ,! %>p beak1 a y>d long1 0 too?less & bird-l1 z its "n sugge/s4 ,illu/ration3 ,fig4 #cch4 ,ar*opt]yx ,birds4 ,! e>lie/ kn[n birds are f\nd 9 ! ,jurassic1 & dur+ ! rema9d] ( ! ,mesozoic !y cont5d$ ) ! fly+ reptiles = ! empire ( ! air4 ,! fir/ fea!r$ creatures 7 v diff]5t f ! birds ( to-day4 ,_! *>act]i/ics prove !m an (f%oot ( ! d9osaur l9e ( reptiles4 ,ar*opt]yx 7anci5t bird7 7,fig4 #cch7 exhibits a /range m+l+ ( bird & reptile4 ,l birds1 x 0 fl$g$ ) p]fect fea!rs1 at lea/ on w+s & tail1 b x reta9$ ! tee? ( ! reptile1 & its long tail 0 v]tebrat$1 a pair ( fea!rs spr++ f ea* jo9t4 ,?r\gh\t ! ,jurassic & ,cretace\s ! rema9s ( birds are f> less common ?an ^? ( fly+ reptiles1 & /rata repres5t+ hundr$s ( ?\s&s ( ye>s int]v5e betwe5 ,ar*opt]yx & ! next birds ( :i* we "k1 ^: skeletons occur 9 ! ,cretace\s b$s ( we/]n ,kansas4 ,mammals4 ,s f> z ! entries ^u ! geological record %[1 mammals made _! adv5t 9 a v humble way dur+ ! ,trias4 ,^! e>lie/ ( v]tebrates :i* suckle _! "y 7 no bigg] ?an "y kitt5s1 & _! /rong aff9ities ) ! !romorphs sugge/ t _! ance/ors are to be f\nd among "s g5]aliz$ types ( t ord] ( reptiles4 ,illu/ration3 ,fig4 #cci4 ,jawbone ( a ,jurassic ,mammal ,dur+ ! long ages ( ! ,mesozoic1 mammals cont9u$ small & few1 & 7 completely dom9at$ by ! reptiles4 ,_! rema9s are exce$+ly r>e1 & consi/ ( m9ute scatt]$ tee?1--) an occasional deta*$ jaw1--:i* prove !m to h be5 fle% or insect eat]s4 ,9 ! same way _! aff9ities are se5 to be ) ! l[e/ ( mammals1--! monotremes & m>supials4 ,! monotremes1--su* z ! duckbill mole & ! sp9y ant-eat] ( ,au/ralia1 reproduce by means ( eggs resembl+ ^? ( reptiles2 ! m>supials1 su* z ! opossum & ! kang>oo1 br+ =? _! "y alive1 b 9 a v immature condition1 & c>ry !m = "s "t aft] bir? 9 ! m>supium1 a p\* on ! v5tral side ( ! body4 ,,*apt] ,,xxi ,,! ,,t]ti>y ,! ,c5ozoic era4 ,! la/ /ages ( ! ,cretace\s are m>k$ by a decad5ce ( ! reptiles4 ,by ! end ( t p]iod ! reptilian =ms *>act]i/ic ( ! "t _h become ext9ct "o aft] ano!r1 leav+ to repres5t ! class only ! types ( reptiles :i* cont9ue to mod]n times4 ,! day ( ! ammonite & ! belemnite also n[ drew to a close1 & only a few ( ^! cephalopods 7 left to survive ! p]iod4 ,x is !re=e at ! close ( ! ,cretace\s t ! l9e is drawn :i* m>ks ! end ( ! ,middle ,age ( geology & ! beg9n+ ( ! ,c5ozoic era1 ! era ( mod]n life1--! ,age ( ,mammals4 ,9 place ( ! giant reptiles1 mammals n[ become ma/]s ( ! l&1 appe>+ fir/ 9 g5]aliz$ types :i*1 dur+ ! long ages ( ! era1 gradually evolve to high] =ms1 m specializ$ & ev] m closely resembl+ ! mammals ( ! pres5t4 ,9 ! atmosph]e ! fly+ dragons ( ! ,mesozoic give place to birds & bats4 ,9 ! sea1 :ales1 %>ks1 & teleo/ fi%es ( mod]n types rule 9 ! /ead ( huge swimm+ reptiles4 ,! l[] v]tebrates1 ! inv]tebrates ( l& & sea1 & ! plants ( field & =e/ take on a mod]n aspect1 & diff] little m f ^? ( to-day ?an ! plants & animals ( diff]5t c\ntries n[ diff] f "o ano!r4 ,f ! beg9n+ ( ! ,c5ozoic era until n[ !re is a /eadily increas+ numb] ( species ( animals & plants :i* h cont9u$ to exi/ to ! pres5t "t4 ,! ,c5ozoic era comprises two divisions1--! ,t]ti>y p]iod & ! ,quat]n>y p]iod4 ,9 ! e>ly days ( geology ! =mations ( ! entire geological record1 s f> z x 0 !n kn[n1 7 divid$ into ?ree gr\ps1--! ,prim>y1 ! ,second>y 7n[ kn[n z ! ,mesozoic71 & ! ,t]ti>y1 ,:5 ! ?ird gr\p 0 subdivid$ into two sy/ems1 ! t]m ,t]ti>y 0 reta9$ = ! fir/ sy/em ( ! two1 :ile ! t]m ,quat]n>y 0 us$ to designate ! second4 ,divisions ( ! ,t]ti>y4 ,! =mations ( ! ,t]ti>y are gr\p$ 9 ?ree divisions1--! ,plioc5e 7m rec5t71 ! ,mioc5e 7less rec5t71 & ! ,eoc5e 7! dawn ( ! rec5t74 ,ea* ( ^! epo*s is long & complex4 ,_! v>i\s subdivisions are di/+ui%$ ea* by its own peculi> organisms1 & ! *anges ( physical geography record$ 9 _! /rata4 ,9 ! rapid view :i* we are compell$ to take we c note only a few ( ! mo/ conspicu\s ev5ts ( ! p]iod4 ,physical geography ( ! ,t]ti>y 9 ea/]n ,nor? ,am]ica4 ,! ,t]ti>y rocks ( ea/]n ,nor? ,am]ica are m>9e deposits & occupy ! coa/al l[l&s ( ! ,atlantic & ,gulf /ates 7,fig4 #bfj74 ,9 ,new ,engl&1 ,t]ti>y b$s occur on ! isl& ( ,m>?a's ,v9ey>d1 b n on ! ma9l&2 h5ce ! %ore l9e "h /ood some:at f>!r out ?an n[4 ,f ,new ,j]sey s\?w>d ! e>lie/ ,t]ti>y s&s & clays1 /ill unconsolidat$1 leave only a n>r[ /rip ( ! edge ( ! ,cretace\s betwe5 !m & ! ,triassic & cry/all9e rocks ( ! ,pi$mont oldl&2 h5ce ! ,atlantic %ore "h /ood f>!r 9 ?an n[1 & at ! beg9n+ ( ! p]iod ! pres5t coa/al pla9 0 cont95tal delta4 ,a broad belt ( ,t]ti>y sea-laid lime/ones1 s&/ones1 & %ales surr\nds ! ,gulf ( ,mexico & ext5ds nor?w>d up ! ,mississippi embaym5t to ! m\? ( ! ,ohio ,riv]2 h5ce ! ,gulf 0 !n l>g] ?an at pres5t1 & its wat]s rea*$ 9 a broad bay f> up ! ,mississippi valley4 ,along ! ,atlantic coa/ ! ,mesozoic p5epla9 may be trac$ %orew>d to :]e x disappe>s f view b5ea? an uncon=mable cov] ( e>ly ,t]ti>y m>9e /rata4 ,! beg9n+ ( ! ,t]ti>y 0 !re=e m>k$ by a subsid5ce4 ,! wide erosion surface :i* at ! close ( ! ,mesozoic lay ne> sea level :]e ! ,appala*ian ,m\nta9s & _! neighbor+ plateaus & upl&s n[ /& 0 l[]$ g5tly along its seaw>d edge b5ea? ! ,t]ti>y ,atlantic to receive a cov] ( its s$im5ts4 ,z ! p]iod progress$ slight oscillations occurr$ f "t to "t4 ,/rips ( coa/al pla9 7 add$ to ! l&1 & z e>ly z ! close ( ! ,mioc5e ! %ore l9es ( ! ,atlantic & ,gulf /ates _h rea*$ well-nigh _! pres5t place4 ,l\isiana & ,florida 7 ! la/ areas to em]ge :olly f ! sea1--,florida be+ =m$ by a broad transv]se upw>p ( ! cont95tal delta at ! op5+ ( ! ,mioc5e1 =m+ fir/ an isl&1 :i* aft]w>ds 0 jo9$ to ! ma9l&4 ,! ,pacific coa/4 ,t]ti>y deposits ) m>9e fossils occur along ! we/]n foo?ills ( ! ,si]ra ,nevadas1 & are crumpl$ among ! m\nta9 masses ( ! ,coa/ ,ranges2 x is h5ce inf]r$ t ! ,great ,valley ( ,cali=nia 0 !n a bord] sea1 sep>at$ f ! ocean by a *a9 ( m\nta9\s isl&s :i* 7 upridg$ into ! ,coa/ ,ranges at a /ill lat] "t4 ,t]ti>y m>9e /rata are spread ov] ! l[] ,columbia valley & t ( ,puget ,s\nd1 %[+ t ! ,pacific came 9 broadly !re4 ,! int]ior ( ! we/]n ,unit$ ,/ates4 ,! clos+ /ages ( ! ,mesozoic 7 m>k$1 z we h se51 by ! upheaval ( ! ,rocky ,m\nta9s & o!r we/]n ranges4 ,! bases ( ! m\nta9s are n[ skirt$ by widespread ,t]ti>y deposits1 :i* =m ! highe/ /rata ( ! l(ty plateaus f ! level ( ^: summits ! m\nta9s rise4 ,l ! rec5t alluvium ( ! ,great ,valley ( ,cali=nia 7p4 #aja71 ^! deposits imply l[-ly+ l&s :5 !y 7 laid1 & !re=e at t "t ! m\nta9s rose f ne> sea level4 ,b ! height at :i* ! ,t]ti>y /rata n[ /&--five ?\s& feet above ! sea at ,d5v]1 & twice t height 9 ! plateaus ( s\!rn ,utah--proves t ! plateaus ( :i* ! ,t]ti>y /rata =m a "p h be5 uplift$ dur+ ! ,c5ozoic4 ,dur+ _! uplift1 w>p+ =m$ ext5sive bas9s bo? ea/ & we/ ( ! ,rockies1 & 9 ^! bas9s /ream-swept & lake-laid wa/e ga!r$ to dep?s ( hundr$s & ?\s&s ( feet1 z x is accumulat+ at pres5t 9 ! ,great ,valley ( ,cali=nia & on ! riv] pla9s ( ,turke/an 7p4 #ajc74 ,! ,t]ti>y riv] deposits ( ! ,high ,pla9s h already be5 describ$ 7p4 #ajj74 ,h[ widespread are ^! anci5t riv] pla9s & b$s ( fre%-wat] lakes may be se5 9 ! map ( ,figure #bfj4 ,illu/ration3 ,fig4 #cdj4 ,view 9 ! ,bad ,l&s ( ,s\? ,dakota ,! ,bad ,l&s4 ,9 sev]al ( ! we/]n /ates l>ge areas ( ,t]ti>y fre%-wat] deposits h be5 dissect$ to a maze ( hills ^: /eep sides are cut ) innum]able rav9es4 ,! deposits ( ^! anci5t riv] pla9s & lake b$s are little cem5t$ & because ( ! dryness ( ! climate are unprotect$ by vegetation2 h5ce !y are easily c>v$ by ! wet-wea!r rills ( scanty & infrequ5t ra9s4 ,^! wat]less1 rugg$ surfaces 7 nam$ by ! e>ly ,fr5* explor]s ! ,bad ,l&s because !y 7 f\nd s difficult to trav]se4 ,! /rata ( ! ,bad ,l&s conta9 va/ numb]s ( ! rema9s ( ! animals ( ,t]ti>y times1 & ! l>ge am\nt ( b>r5 surface expos$ to view makes se>* = fossils easy & fruitful4 ,^! desolate tracts are !re=e frequ5tly visit$ by sci5tific collect+ exp$itions4 ,m\nta9 mak+ 9 ! ,t]ti>y4 ,! ,t]ti>y p]iod includ$ epo*s :5 ! e>?'s cru/ 0 s+ul>ly unquiet4 ,f "t to "t on all ! cont95ts subt]ranean =ces ga!r$ head1 & ! cru/ 0 b5t & brok5 & upridg$ 9 l(ty m\nta9s4 ,! ,si]ra ,nevada range 0 =m$1 z we h se51 by /rata crumpl+ at ! end ( ! ,jurassic4 ,b s9ce t remote "t ! upfold$ m\nta9s _h be5 worn to pla9s & hilly upl&s1 ! remnants ( ^: uplift$ erosion surfaces may n[ be trac$ along ! we/]n m\nta9 slopes4 ,beg9n+ late 9 ! ,t]ti>y1 ! region 0 aga9 affect$ by m\nta9-mak+ movem5ts4 ,a s]ies ( displacem5ts along a pr(\nd fault on ! ea/]n side tilt$ ! enorm\s e>? block ( ! ,si]ras to ! we/1 lift+ its ea/]n edge to =m ! l(ty cre/ & giv+ to ! range a /eep ea/]n front & a g5tle desc5t t[>d ! ,pacific4 ,! ,coa/ ,ranges also h _h a complex hi/ory ) _m vicissitudes4 ,! e>lie/ fold+s ( _! /rata belong to ! close ( ! ,jurassic1 b x 0 n until ! end ( ! ,mioc5e t ! l9e ( m\nta9\s isl&s & ! heavy s$im5ts :i* _h be5 deposit$ on _! subm]g$ flanks 7 cru%$ into a cont9u\s m\nta9 *a94 ,?ick ,plioc5e b$s ^u _! sides prove t !y 7 depress$ to ne> sea level dur+ ! lat] ,t]ti>y4 ,at ! close ( ! ,plioc5e ! ,coa/ ,ranges rose along ) ! upheaval ( ! ,si]ra1 & _! gradual uplift has cont9u$ to ! pres5t "t4 ,! num]\s nor?-s\? ranges ( ! ,great ,bas9 & ! ,m\nt ,sa9t ,elias range ( ,alaska 7 also uptilt$ dur+ ! ,t]ti>y4 ,dur+ ! ,t]ti>y p]iod _m ( ! l(tie/ m\nta9s ( ! e>?--! ,alps1 ! ,ap5n9es1 ! ,pyr5ees1 ! ,atlas1 ! ,caucasus1 & ! ,himalayas--receiv$ ! uplift to :i* !y owe mo/ ( _! colossal bulk & height1 z portions ( ! ,t]ti>y sea b$s n[ f\nd high ^u _! flanks atte/4 ,9 ! ,himalayas1 ,t]ti>y m>9e lime/ones occur sixte5 ?\s& five hundr$ feet above sea level4 ,volcanic activity 9 ! t]ti>y4 ,! va/ de=mations ( ! ,t]ti>y 7 accompani$ on a correspond+ scale by outp\r+s ( lava1 ! outbur/ ( volcanoes1 & ! intrusion ( molt5 masses )9 ! cru/4 ,9 ! ,si]ra ,nevadas ! ,mioc5e riv] gravels ( ! valleys ( ! we/]n slope1 ) _! plac] deposits ( gold1 7 buri$ b5ea? /reams ( lava & b$s ( tuff 7,fig4 #beh74 ,volcanoes broke =? along ! ,rocky ,m\nta9s & on ! plateaus ( ,utah1 ,new ,mexico1 & ,arizona4 ,m\nt ,%a/a & ! imm5se volcanic piles ( ! ,cascades date f ?is p]iod4 ,! m\nta9 bas9 ( ! ,yell[/one ,p>k 0 fill$ to a dep? ( sev]al ?\s& feet ) tuffs & lavas1 ! olde/ dat+ z f> back z ! beg9n+ ( ! ,t]ti>y4 ,cr&all volcano 7,fig4 #bfc7 0 re>$ 9 ! ,mioc5e & ! late/ eruptions ( ! ,p>k are f> m rec5t4 ,illu/ration3 ,fig4 #cda4 ,lava ,plateau ) ,lava ,domes 9 ! ,di/ance ,! ,columbia & ,snake ,riv] lavas4 ,/ill m important is ! plateau ( lava1 m ?an two hundr$ ?\s& squ>e miles 9 area1 ext5d+ f ! ,yell[/one ,p>k to ! ,cascade ,m\nta9s1 :i* has be5 built f ,mioc5e times to ! pres5t4 ,ov] ?is plateau1 :i* occupies l>ge portions ( ,idaho1 ,wa%+ton1 & ,oregon1 & ext5ds into nor!rn ,cali=nia & ,nevada1 ! c\ntry rock is basaltic lava4 ,= ?\s&s ( squ>e miles ! surface is a lava pla9 :i* meets ! b\nd>y m\nta9s z a lake or sea meets a rugg$ & deeply ind5t$ coa/4 ,! floods ( molt5 rock spread up ! m\nta9 valleys = a score ( miles & m1 ! int]v5+ spurs ris+ above ! lava l long p59sulas1 :ile "h & !re an isolat$ peak 0 left to t[] above ! inundation l an isl& (f a subm]g$ %ore4 ,! riv]s :i* dra9 ! plateau--! ,snake1 ! ,columbia1 & _! tribut>ies--h deeply tr5*$ x1 yet _! canyons1 :i* rea* ! dep? ( sev]al ?\s& feet1 h n be5 worn to ! base ( ! lava except ne> ! m>g9 & :]e !y cut ! summits ( m\nta9s dr[n$ b5ea? ! flood4 ,"h & !re ! plateau has be5 de=m$4 ,x has be5 upb5t into great folds1 & brok5 into imm5se blocks ( b$d$ lava1 =m+ m\nta9 ranges1 :i* run p>allel ) ! ,pacific coa/ l9e4 ,on ! edges ( ^! tilt$ blocks ! ?ickness ( ! lava is se5 to be fully five ?\s& feet4 ,! plateau has be5 built1 l t ( ,icel& 7p4 #bdb71 ( innum]able ov]lapp+ %eets ( lava4 ,on ! canyon walls !y wea!r back 9 horizontal t]races & long talus slopes4 ,"o may di/+ui% ea* successive fl[ by its d5se c5tral portion1 (t5 jo9t$ ) l>ge v]tical columns1 & ! upp] portion ) its mass ( confus$ irregul> columns & scoriace\s surface4 ,! av]age ?ickness ( ! fl[s seems to be ab\t sev5ty-five feet4 ,! plateau 0 long 9 build+4 ,betwe5 ! lay]s are f\nd 9 places old soil b$s & =e/ gr\nds & ! s$im5ts ( lakes4 ,h5ce ! int]val betwe5 ! fl[s 9 any locality 0 sometimes long en\gh = clays to ga!r 9 ! lakes :i* fill$ depressions 9 ! surface4 ,aga9 & aga9 ! surface ( ! black basalt 0 r$d5$ by oxidation & decay$ to soil1 & =e/s _h "t to gr[ ^u x be=e ! succe$+ inundation seal$ ! s$im5ts & soils away b5ea? a %eet ( /one4 ,ne> ! edges ( ! lava pla91 riv]s f ! surr\nd+ m\nta9s spread %eets ( s& & gravel on ! surface ( "o fl[ aft] ano!r4 ,^! p]vi\s s&s1 int]b$d$ ) ! lava1 become ! aquif]s ( artesian wells4 ,9 places ! lavas re/ on ext5sive lake deposits1 "o ?\s& feet deep1 & ,mioc5e 9 age z _! fossils prove4 ,x is to ! middle ,t]ti>y1 !n1 t ! e>lie/ fl[s & ! l>ge/ bulk ( ! great inundation belong4 ,s anci5t are ! late/ floods 9 ! ,columbia bas9 t !y h wea!r$ to a residual yell[ clay f ?irty to sixty feet 9 dep? & m>vel\sly ri* 9 ! m9]al sub/ances on :i* plants fe$4 ,9 ! ,snake ,riv] valley ! late/ lavas are mu* y\ng]4 ,_! surfaces are s fre% & undecay$ t "h ! effusive eruptions may well h cont9u$ to )9 ! p]iod ( human hi/ory4 ,l[ lava domes l ^? ( ,icel& m>k :]e la/ ! basalt outwell$ & spread f> & wide be=e x *ill$ 7,fig4 #cda74 ,9 places small m\nds ( scoria %[ t ! eruptions 7 accompani$ to a slight degree by explosions ( /eam4 ,s fluid 0 ?is sup]heat$ lava t rec5t fl[s h be5 trac$ = m ?an fifty miles4 ,! rocks und]ly+ ! ,columbia lavas1 :]e expos$ to view1 are se5 to be cut by num]\s great dikes ( d5se basalt1 :i* m>k ! fissures ?r\gh :i* ! molt5 rock rose to ! surface4 ,! ,t]ti>y includ$ times ( widespread & int5se volcanic action 9 o!r cont95ts z well z 9 ,nor? ,am]ica4 ,9 ,europe1 ,vesuvius 7p4 #bca7 & ,etna began _! c>e] z subm>9e volcanoes 9 connection ) e>? movem5ts :i* f9ally lift$ ,plioc5e deposits 9 ,sicily to _! pres5t height1--f\r ?\s& feet above ! sea4 ,volcanoes broke =? 9 c5tral ,france & s\!rn ,g]many1 9 ,hung>y & ! ,c>pa?ians4 ,innum]able fissures op5$ 9 ! cru/ f ! nor? ( ,irel& & ! we/]n isl&s ( ,scotl& to ! ,f>oes1 ,icel&1 & ev5 to arctic ,gre5l&2 & "h great plateaus 7 built ( fl[s ( basalt simil> to t ( ! ,columbia ,riv]4 ,9 ,india1 at ! op5+ ( ! ,t]ti>y1 !re _h be5 an outwell+ ( basalt1 flood+ to a dep? ( ?\s&s ( feet two hundr$ ?\s& squ>e miles ( ! nor?we/]n "p ( ! p59sula 7,fig4 #cdb71 & simil> inundations ( lava occurr$ :]e are n[ ! table-l&s ( ,abyss9ia4 ,f ! middle ,t]ti>y on1 ,asia ,m9or1 ,arabia1 & ,p]sia 7 ! sc5es ( volcanic action4 ,9 ,pale/9e ! rise ( ! upl&s ( ,judea at ! close ( ! ,eoc5e1 & ! d[nfault+ ( ! ,jordan valley 7p4 #bba7 7 foll[$ by volcanic outbur/s4 ,9 comp>ison ) ! middle ,t]ti>y1 ! pres5t is a "t ( volcanic inactivity & repose4 ,illu/ration3 ,fig4 #cdb4 ,map %[+ ! ,lava ,%eet 7%ad$ area7 ( ,we/]n ,india ,erosion ( ,t]ti>y m\nta9s & plateaus4 ,! m\nta9s & plateaus built at v>i\s times dur+ ! ,t]ti>y & at its comm5cem5t h be5 pr(\ndly c>v$ by erosive ag5ts4 ,! ,si]ra ,nevada ,m\nta9s h be5 dissect$ on ! we/]n slope by su* canyons z ^? ( ,k+'s ,riv] & ! ,yosemite4 ,six miles ( /rata h be5 d5ud$ f p>ts ( ! ,wasat* ,m\nta9s s9ce _! rise at ! beg9n+ ( ! era4 ,f ! ,colorado plateaus1 ^: uplift dates f ! same "t1 !re h be5 /ripp$ (f t5 ?\s& feet ( /rata ov] ?\s&s ( squ>e miles1 & ! colossal canyon ( ! ,colorado has be5 cut aft] ?is great d5udation _h be5 mo/ly accompli%$4 ,on ! ea/]n side ( ! cont95t1 z we h se51 a broad p5epla9 _h be5 develop$ by ! close ( ! ,cretace\s4 ,! remnants ( ?is old erosion surface are n[ f\nd upw>p$ to v>i\s heights 9 diff]5t portions ( its area4 ,9 s\!rn ,new ,engl& x n[ /&s fifte5 hundr$ feet above ! sea 9 we/]n ,massa*usetts1 decl9+ !nce s\?w>d & ea/w>d to sea level at ! coa/4 ,9 s\?we/]n ,virg9ia x has be5 lift$ to f\r ?\s& feet above ! sea4 ,manife/ly ?is upw>p occurr$ s9ce ! p5epla9 0 =m$2 x is lat] ?an ! ,mesozoic1 & ! va/ dissection :i* ! p5epla9 has suff]$ s9ce its uplift mu/ belong to ! successive cycles ( ,c5ozoic "t4 ,reviv$ by ! uplift1 ! /reams ( ! area tr5*$ x z deeply z its elevation p]mitt$1 & rea*+ grade1 op5$ up wide valleys & new p5epla9s 9 ! s(t] rocks4 ,! ,connecticut valley is ,t]ti>y 9 age1 & 9 ! weak ,triassic s&/ones has be5 wid5$ 9 places to fifte5 miles4 ,dat+ f ! same "t are ! valleys ( ! ,hudson1 ! ,susquehanna1 ! ,delaw>e1 ! ,potomac1 & ! ,%5&oah4 ,9 ,p5nsylvania & ! /ates ly+ to ! s\? ! ,mesozoic p5epla9 lies along ! summits ( ! m\nta9 ridges4 ,on ! surface ( ?is anci5t pla91 ,t]ti>y erosion et*$ out ! beautifully regul> patt]n ( ! ,allegh5y m\nta9 ridges & _! int]v5+ valleys4 ,! weak] /rata ( ! long1 regul> folds 7 erod$ into longitud9al valleys1 :ile ! h>d ,paleozoic s&/ones1 su* z ! ,m$9a 7p4 #cce7 & ! ,pocono 7p4 #cej71 7 left 9 relief z bold m\nta9 walls ^: ev5 cre/s rise to ! common level ( ! anci5t pla94 ,f ,virg9ia f> into ,alabama ! great ,appala*ian valley 0 op5$ to a wid? 9 places ( fifty miles & m1 along a belt ( int5sely fold$ & fault$ /rata :]e once 0 ! he>t ( ! ,appala*ian ,m\nta9s4 ,9 ,figure #gj1 ! summit ( ! ,cumb]l& plateau 7ab7 m>ks ! level ( ! ,mesozoic p5epla91 :ile ! l[] erosion levels are ,t]ti>y & ,quat]n>y 9 age4 ,illu/ration3 ,fig4 #cdc4 ,diagram ( ! ,allegh5y ,m\nta9s1 ,p5nsylvania ,f ,davis' ,elem5t>y ,physical ,geography ,life ( ! ,t]ti>y ,p]iod ,vegetation & climate4 ,! highe/ plants 9 /ructure1 ! dicotyls 7su* z our decidu\s =e/ trees7 & ! monocotyls 7repres5t$ by ! palms71 7 introduc$ dur+ ! ,cretace\s4 ,! vegetable k+dom rea*$ its culm9ation be=e ! animal k+dom1 & if ! divid+ l9e betwe5 ! ,mesozoic & ! ,c5ozoic 7 drawn accord+ to ! progress ( plant life1 ! ,cretace\s in/ead ( ! ,t]ti>y w\ld be made ! op5+ p]iod ( ! mod]n era4 ,! plants ( ! ,t]ti>y belong$1 = ! mo/ "p1 to g5]a n[ liv+2 b _! di/ribution 0 v diff]5t f t ( ! flora ( to-day4 ,9 ! e>li] ,t]ti>y1 palms fl\ri%$ ov] nor!rn ,europe1 & 9 ! nor?we/]n ,unit$ ,/ates grew ! magnolia & laurel1 along ) ! walnut1 oak1 & elm4 ,ev5 9 nor!rn ,gre5l& & 9 ,spitzb]g5 !re 7 lakes cov]$ ) wat] lilies & surr\nd$ by =e/s ( maples1 popl>s1 limes1 ! cypress ( our s\!rn /ates1 & noble sequoias simil> to ! big trees & r$woods ( ,cali=nia4 ,a w>m climate l t ( ! ,mesozoic1 !re=e1 prevail$ ov] ,nor? ,am]ica & ,europe1 ext5d+ f> t[>d ! pole4 ,9 ! lat] ,t]ti>y ! climate gradually became cool]4 ,palms disappe>$ f ,europe1 & ev]y:]e ! aspect ( =e/s & op5 l&s became m l t ( to-day4 ,grasses became abundant1 furni%+ a new food = h]bivor\s animals4 ,animal life ( ! ,t]ti>y4 ,little ne$s to be said ( ! ,t]ti>y inv]tebrates1 s ne>ly 7 !y l ! inv]tebrates ( ! pres5t4 ,ev5 9 ! ,eoc5e1 ab\t five p] c5t ( m>9e %ells 7 ( species /ill liv+1 & 9 ! ,plioc5e ! proportion _h ris5 to m ?an "o half4 ,fi%es 7 ( mod]n types4 ,teleo/s 7 n[ abundant4 ,! ocean teem$ ) %>ks1 "s ( !m be+ voraci\s mon/]s sev5ty-five feet & ev5 m 9 l5g?1 ) a gape ( jaw ( six feet1 z e/imat$ by ! size ( _! enorm\s %>p-edg$ tee?4 ,snakes are f\nd = ! fir/ "t 9 ! e>ly ,t]ti>y4 ,^! limbless reptiles1 evolv$ by deg5]ation f liz>dlike ance/ors1 appe>$ 9 nonpoison\s types sc>cely to be di/+ui%$ f ^? ( ! pres5t day4 ,mammals ( ! e>ly ,t]ti>y4 ,! fossils ( cont95tal deposits ( ! e>lie/ ,eoc5e %[ t a m>k$ advance _h n[ be5 made 9 ! evolution ( ! ,mammalia4 ,! high] mammals _h appe>$1 & h5ce=? ! l[] mammals--! monotremes & ! m>supials--are r$uc$ to a subord9ate place4 ,illu/ration3 ,fig4 #cdd4 ,ph5acodus ,^! fir/ true mammals 7 ar*aic & g5]aliz$ 9 /ructure4 ,_! feet 7 ( ! primitive type1 ) five toes ( ab\t equal l5g?4 ,!y 7 also plantigrades1--t is1 !y t\*$ ! gr\nd ) ! sole ( ! entire foot f toe to heel4 ,no foot _h yet become adapt$ to swift runn+ by a decrease 9 ! numb] ( digits & by lift+ ! heel & sole s t only ! toes t\* ! gr\nd1--a tread call$ digitigrade4 ,nor 0 !re yet any foot l t ( ! cats1 ) %>p retractile claws adapt$ to seiz+ & te>+ ! prey4 ,! =e>m & ! l[] leg ea* _h /ill two sep>ate bones 7ulna & radius1 fibula & tibia71 nei!r pair hav+ be5 replac$ ) a s+le /rong bone1 z 9 ! leg ( ! horse4 ,! tee? also 7 primitive 9 type & ( full numb]4 ,! complex heavy gr9d]s ( ! horse & elephant1 ! %>p cutt+ tee? ( ! c>nivores1 & ! cropp+ tee? ( ! grass eat]s 7 all /ill to come4 ,ph5acodus is a *>act]i/ic g5us ( ! e>ly ,eoc5e1 ^: species v>i$ 9 size f t ( a bulldog to t ( an animal a little l>g] ?an a %eep4 ,its feet 7 primitive1 & _! five toes bore nails int]m$iate 9 =m betwe5 a claw & a ho(4 ,! ar*aic type ( tee? indicates t ! animal 0 omnivor\s 9 diet4 ,a ca/ ( ! bra9 cavity %[s t1 l its associates ( ! "t1 its bra9 0 extremely small & ne>ly smoo?1 hav+ little m ?an traces ( convolutions4 ,! long ages ( ! ,eoc5e & ! foll[+ epo*s ( ! ,t]ti>y 7 times ( comp>atively rapid evolution among ! ,mammalia4 ,! e>lie/ =ms evolv$ along div]g+ l9es t[>d ! v>i\s specializ$ types ( ho($ mammals1 rod5ts1 c>nivores1 proboscidians1 ! primates1 & ! o!r mammalian ord]s z we "k !m n[4 ,we mu/ describe ! ,t]ti>y mammals v briefly1 trac+ ! l9es ( desc5t ( only a few ( ! m famili> mammals ( ! pres5t4 ,! horse4 ,! p$igree ( ! horse runs back into ! e>ly ,eoc5e ?r\gh _m g5]a & species to a five-to$1#c %ort-legg$ ance/or little bigg] ?an a cat4 ,its desc5dants gradually increas$ 9 /ature & became bett] & bett] adapt$ to swift runn+ to escape _! foes4 ,! leg became long]1 & only ! tip ( ! toes /ruck ! gr\nd4 ,! middle toe 7digit numb] ?ree71 orig9ally ! longe/ ( ! five1 /eadily enl>g$1 :ile ! rema9+ digits dw9dl$ & disappe>$4 ,! inn] digit1 correspond+ to ! great toe & ?umb1 0 ! fir/ to g4 ,next numb] five1 ! little f+]1 0 also dropp$4 ,by ! end ( ! ,eoc5e a ?ree-to$ g5us ( ! horse family _h appe>$1 z l>ge z a %eep4 ,! ho( ( digit numb] ?ree n[ support$ mo/ ( ! weight1 b ! sl5d] ho(s ( digits two & f\r 7 /ill s]viceable4 ,9 ! ,mioc5e ! /ature ( ! ance/ors ( ! horse increas$ to t ( a pony4 ,! feet 7 /ill ?ree-to$1 b ! side ho(s 7 n[ m]e dewclaws & sc>cely t\*$ ! gr\nd4 ,! evolution ( ! family 0 complet$ 9 ! ,plioc5e4 ,! middle toe 0 enl>g$ /ill m1 ! side toes 7 dropp$1 & ! palm & foot bones :i* support$ !m 7 r$uc$ to spl9ts4 #c ,or1 m accurately1 ) f\r p]fect toes & a rudim5t>y fif? correspond+ to ! ?umb4 ,illu/ration3 ,fig4 #cde4 ,developm5t ( ,=efoot 7,a71 ! ,=e>m 7,b71 ! ,mol> 7,c71 ( ! ,horse ,family ,:ile ^! *anges 7 9 progress ! radius & ulna ( ! =e limb became consolidat$ to a s+le bone2 & 9 ! h9d limb ! fibula dw9dl$ to a spl9t1 :ile ! tibia 0 correspond+ly enl>g$4 ,! mol>s1 also gradually l5g!n$1 & became m & m complex on _! gr9d+ surface2 ! neck became long]2 ! bra9 /eadily increas$ 9 size & its convolutions became m abundant4 ,! evolution ( ! horse has made = great] fleetness & intellig5ce4 ,! rh9oc]os & tapir4 ,^! animals1 :i* are gr\p$ ) ! horse among ! odd-to$ 7p]issodactyl7 mammals1 are n[ v]g+ t[>d ext9ction4 ,9 ! rh9oc]os1 evolution seems to h tak5 ! opposite c\rse f t ( ! horse4 ,z ! animal increas$ 9 size x became m clumsy1 its limbs became %ort] & m massive1 &1 p]haps because ( its great weight1 ! numb] ( digits 7 n r$uc$ bel[ ! numb] ?ree4 ,l o!r l>ge h]bivores1 ! rh9oc]os1 too sl[ to escape its enemies by flight1 le>n$ to )/& !m4 ,x develop$ z its means ( def5se a nasal horn4 ,peculi> (f%oots ( ! l9e appe>$ at v>i\s times 9 ! ,t]ti>y4 ,a rh9oc]os1 semiaquatic 9 habits1 ) curv$ tusks1 resembl+ 9 aspect ! hippopotamus1 liv$ along ! wat] c\rses ( ! pla9s ea/ ( ! ,rockies1 & its bones are n[ f\nd by ! ?\s&s 9 ! ,mioc5e ( ,kansas4 ,ano!r develop$ along a l9e p>allel to t ( ! horse1 & h]ds ( ^! light-limb$ & swift-foot$ runn+ rh9oc]oses rang$ ! ,great ,pla9s f ! ,dakotas s\?w>d4 ,! tapirs are an anci5t family :i* has *ang$ b little s9ce x sep>at$ f ! o!r p]issodactyl /ocks 9 ! e>ly ,t]ti>y4 ,at pres5t1 tapirs are f\nd only 9 ,s\? ,am]ica & s\!rn ,asia1--a rem>kable di/ribution :i* we c\ld n expla9 7 x n t ! geological record %[s t dur+ ,t]ti>y times tapirs rang$ ?r\gh\t ! nor!rn hemisph]e1 mak+ _! way to ,s\? ,am]ica late 9 t p]iod4 ,dur+ ! ,plei/oc5e !y became ext9ct ov] all ! int]v5+ l&s betwe5 ! widely sep>at$ regions :]e n[ !y live4 ,! geographic di/ribution ( animals1 z well z _! relation%ips & orig9s1 c be und]/ood only ?r\gh a /udy ( _! geological hi/ory4 ,illu/ration3 ,fig4 #cdf4 ,a ,t]ti>y ,ma/odon ,illu/ration3 ,fig4 #cdg4 ,head ( ,d9o!re ,! proboscidians4 ,?is unique ord] ( ho($ mammals1 ( :i* ! elephant is ! sole survivor1 has be5 trac$ back to ! close ( ! ,eoc5e4 ,9 ! middle & lat] ,t]ti>y x 0 repres5t$ by huge creatures s ne>ly ak9 to ! ma/odons ( ! ,plei/oc5e t !y are (t5 includ$ 9 t g5us4 ,! ,t]ti>y ,ma/odon 0 furni%$ ) a long1 flexible proboscis1 & arm$ ) two pairs ( long1 /raight ivory tusks1 ! pair ( ! l[] jaw be+ small]4 ,! ,d9o!re 0 a curi\s (f%oot ( ! l9e1 :i* develop$ 9 ! ,mioc5e 9 ,europe4 ,9 ?is imm5se proboscidian1 ^: skull 0 ?ree feet long1 ! upp] pair ( tusks _h disappe>$1 & ^? ( ! l[] jaw 7 b5t d[n ) a backw>d curve 9 walrus fa%ion4 ,illu/ration3 ,fig4 #cdh4 ,cr[n ( ,ma/odon ,too? ,9 ! true elephants1 :i* d n appe> until ne> ! close ( ! ,t]ti>y1 ! l[] jaw loses its tusks & ! gr9d+ tee? become exce$+ly complex 9 /ructure4 ,! gr9d+ tee? ( ! ma/odon _h long roots & l[ cr[ns cross$ by f\r or five peak$ enamel$ ridges4 ,9 ! tee? ( ! true elephants ! cr[n has become deep1 & ! ridges ( enamel h *ang$ to num]\s upright1 platelike folds1 _! int]spaces fill$ ) cem5t4 ,! two g5]a--,ma/odon & ,elephant--are connect$ by species ^: tee? are int]m$iate 9 patt]n4 ,! proboscidians culm9at$ 9 ! ,plioc5e1 :5 "s ( ! giant elephants rea*$ a height ( f\rte5 feet4 ,illu/ration3 ,fig4 #cdi4 ,too? ( an ,ext9ct ,elephant1 ! ,mammo? ,illu/ration3 ,fig4 #cej4 ,evolution ( ! ,artiodactyl ,foot1 ,illu/rat$ by ,exi/+ ,families ,a1 pig2 ,b1 roebuck2 ,c1 %eep2 ,d1 camel ,! artiodactyls comprise ! ho($ ,mammalia :i* h an ev5 numb] ( toes1 su* z cattle1 %eep1 & sw9e4 ,l ! p]issodactyls1 !y are desc5d$ f ! primitive five-to$ plantigrade mammals ( ! l[e/ ,eoc5e4 ,9 _! evolution1 digit numb] "o 0 fir/ dropp$1 & ! middle pair became l>g] & m massive1 :ile ! side digits1 numb]s two & five1 became %ort]1 weak]1 & less s]viceable4 ,! f\r-to$ artiodactyls culm9at$ 9 ! ,t]ti>y2 at pres5t !y are repres5t$ only by ! hippopotamus & ! hog4 ,along ! ma9 l9e ( ! evolution ( ! artiodactyls ! side toes1 digits two & five1 disappe>$1 leav+ z pro( t !y once exi/$ ! correspond+ bones ( palm & sole z spl9ts4 ,! two-to$ artiodactyls1 su* z ! camels1 de]1 cattle1 & %eep1 are n[ ! lead+ types ( ! h]bivores4 ,sw9e & pecc>ies are two bran*es ( a common /ock1 ! fir/ develop+ 9 ! ,old ,_w & ! second 9 ! ,new4 ,9 ! ,mioc5e a noticeable (f%oot ( ! l9e 0 a gigantic piglike brute1 a root eat]1 ) a skull a y>d 9 l5g?1 ^: rema9s are n[ f\nd 9 ,colorado & ,s\? ,dakota4 ,camels & llamas4 ,! l9e ( camels & llamas develop$ 9 ,nor? ,am]ica1 :]e ! successive *anges f an e>ly ,eoc5e ance/or1 no l>g] ?an a rabbit1 are trac$ /ep by /ep to ! pres5t =ms1 z cle>ly z is ! evolution ( ! horse4 ,9 ! late ,mioc5e "s ( ! ance/ral =ms migrat$ to ! ,old ,_w by way ( a l& connection :]e ,b]+ ,/rait n[ is1 & !re gave rise to ! camels & drom$>ies4 ,o!rs migrat$ into ,s\? ,am]ica1 :i* _h n[ be5 connect$ ) our own cont95t1 & ^! develop$ into ! llamas & guanacos1 :ile ^? ( ! race :i* rema9$ 9 ,nor? ,am]ica became ext9ct dur+ ! ,plei/oc5e4 ,"s peculi> bran*es ( ! camel /em appe>$ 9 ,nor? ,am]ica4 ,9 ! ,plioc5e arose a llama ) ! long neck & limbs ( a giraffe1 ^: food 0 cropp$ f ! leaves & bran*es ( trees4 ,f> m g5]aliz$ 9 /ructure 0 ! ,oreodon1 an animal relat$ to ! camels1 b ) di/9ct aff9ities also ) o!r l9es1 su* z ^? ( ! hog & de]4 ,^! curi\s creatures 7 mu* l ! pecc>y 9 appe>ance1 except = _! long tails4 ,9 ! middle ,eoc5e !y roam$ 9 va/ h]ds f ,oregon to ,kansas & ,nebraska4 ,! rum9ants4 ,?is division ( ! artiodactyls includes antelopes1 de]1 ox51 bison1 %eep1 & goats1--all ( :i* belong to a common /ock :i* took its rise 9 ,europe 9 ! upp] ,eoc5e f ance/ral =ms ak9 to ^? ( ! camels4 ,9 ! ,mioc5e ! evolution ( ! two-to$ artiodactyl foot 0 well-nigh complet$4 ,bonelike gr[?s appe>$ on ! head1 & ! two gr\ps ( ! rum9ants became specializ$1--! de] ) bony antl]s1 %$ & r5ew$ ea* ye>1 & ! rum9ants ) holl[ horns1 ^: two bony knobs ^u ! skull are cov]$ ) p]man5t1 po9t$1 horny %ea?s4 ,! rum9ants evolv$ 9 ! ,old ,_w1 & x 0 n until ! lat] ,mioc5e t ! ance/ors ( ! antelope & ( "s de] f\nd _! way to ,nor? ,am]ica4 ,m\nta9 %eep & goats1 ! bison & mo/ ( ! de]1 did n arrive until aft] ! close ( ! ,t]ti>y1 & %eep & ox5 7 introduc$ by man4 ,! ho($ mammals ( ! ,t]ti>y includ$ _m (f%oots f ! ma9 l9es :i* we h trac$4 ,among !m 7 a numb] ( g5]a ( clumsy1 pond]\s brutes1 "s almo/ elephant9e 9 _! bulk4 ,! c>nivores4 ,! ance/ral l9es ( ! families ( ! fle% eat]s--su* z ! cats 7lions1 tig]s1 etc471 ! be>s1 ! hy5as1 & ! dogs 7includ+ wolves & foxes7--conv]ge 9 ! creodonts ( ! e>ly ,eoc5e1--an ord] s g5]aliz$ t x _h aff9ities n only ) ! c>nivores b also ) ! insect eat]s1 ! m>supials1 & ! ho($ mammals z well4 ,f ^! primitive fle% eat]s1 ) small & simple bra9s1 num]\s small tee?1 & plantigrade tread1 ! diff]5t families ( ! c>nivores ( ! pres5t h sl[ly evolv$4 ,dogs & be>s4 ,! dog family div]g$ f ! creodonts late 9 ! ,eoc5e1 & divid$ into two bran*es1 "o ( :i* evolv$ ! wolves & ! o!r ! foxes4 ,an (f%oot gave rise to ! family ( ! be>s1 & s closely d ^! two families1 n[ wide ap>t1 approa* z we trace !m back 9 ,t]ti>y times t ! ,amphicyon1 a g5us doglike 9 its tee? & be>like 9 o!r /ructures1 is ref]r$ by "s to ! dog & by o!rs to ! be> family4 ,! well-kn[n plantigrade tread ( be>s is a primitive *>act]i/ic :i* has surviv$ f _! creodont ance/ry4 ,cats4 ,! family ( ! cats1 ! mo/ highly specializ$ ( all ! c>nivores1 divid$ 9 ! ,t]ti>y into two ma9 bran*es4 ,"o1 ! sab]-too? tig]s 7,fig4 #cea71 :i* takes its "n f _! long1 sab]like1 %>p-edg$ upp] can9e tee?1 evolv$ a succession ( g5]a & species1 among !m "s ( ! mo/ de/ructive bea/s ( prey :i* ev] sc\rg$ ! e>?4 ,!y 7 ma/]s ( ! entire nor!rn hemisph]e dur+ ! middle ,t]ti>y1 b 9 ,europe dur+ ! ,plioc5e !y decl9$1 f unkn[n causes1 & gave place to ! o!r bran* ( cats1--:i* includes ! lions1 tig]s1 & leop>ds4 ,9 ! ,am]icas ! sab]-too? tig]s long surviv$ ! epo*4 ,illu/ration3 ,fig4 #cea4 ,sab]-,too? ,tig] ,m>9e mammals4 ,! c>nivor\s mammals ( ! sea--:ales1 seals1 walruses1 etc4--seem to h be5 d]iv$ f "s ( ! creodonts ( ! e>ly ,t]ti>y by adaptation to aquatic life4 ,:ales evolv$ f "s l& ance/ry at a v e>ly date 9 ! ,t]ti>y2 9 ! m>9e deposits ( ! ,eoc5e are f\nd ! bones ( ! ,zeuglodon1 a :alelike creature sev5ty feet 9 l5g?4 ,primates4 ,?is ord]1 :i* includes lemurs1 monkeys1 apes1 & man1 seems to h sprung f a creodont or insectivor\s ance/ry 9 ! l[] ,eoc5e4 ,lemur-l types1 ) small1 smoo? bra9s1 7 abundant 9 ! ,unit$ ,/ates 9 ! e>ly ,t]ti>y1 b no primates h be5 f\nd "h 9 ! middle ,t]ti>y & lat] /rata4 ,9 ,europe true monkeys 7 introduc$ 9 ! ,mioc5e1 & 7 abundant until ! close ( ! ,t]ti>y1 :5 !y 7 driv5 f ! cont95t by ! increas+ cold4 ,advance ( ! mammalia dur+ ! t]ti>y4 ,dur+ ! sev]al millions ( ye>s compris$ 9 ,t]ti>y "t ! mammals evolv$ f ! l[ly1 simple types :i* t5ant$ ! e>? at ! beg9n+ ( ! p]iod1 into ! _m k9ds ( highly specializ$ mammals ( ! ,plei/oc5e & ! pres5t1 ea* ) ! v>i\s /ructures ( ! body adapt$ to its own peculi> mode ( life4 ,! swift feet ( ! horse1 ! horns ( cattle & ! antl]s ( ! de]1 ! lion's claws & tee?1 ! long incisors ( ! beav]1 ! proboscis ( ! elephant1 7 all develop$ 9 ,t]ti>y times4 ,9 especial ! bra9 ( ! ,t]ti>y mammals con/antly grew l>g] relatively to ! size ( body1 & ! high] portion ( ! bra9--! c]ebral lobes--increas$ 9 size 9 comp>ison ) ! c]ebellum4 ,"s ( ! ho($ mammals n[ h a bra9 eight or t5 times ! size ( t ( _! e>ly ,t]ti>y pr$ecessors ( equal bulk4 ,nor c we d\bt t along ) ! increas+ size ( bra9 w5t a correspond+ increase 9 ! ke5ness ( ! s5ses1 9 activity & vigor1 & 9 intellig5ce4 ,,*apt] ,,xxii ,,! ,,quat]n>y ,! la/ p]iod ( geological hi/ory1 ! ,quat]n>y1 may be said to h begun :5 all1 or ne>ly all1 liv+ species ( mollusks & mo/ ( ! exi/+ mammals _h appe>$4 ,x is divid$ into two great epo*s4 ,! fir/1 ! ,plei/oc5e or ,glacial epo*1 is m>k$ (f f ! ,t]ti>y by ! occupation ( ! nor!rn p>ts ( ,nor? ,am]ica & ,europe by va/ ice %eets2 ! second1 ! ,rec5t epo*1 began ) ! disappe>ance ( ! ice %eets f ^! cont95ts1 & m]ges into ! pres5t "t4 ,! ,plei/oc5e ,epo* ,we n[ come to an episode ( unusual int]e/1 s diff]5t 0 x f mo/ ( ! prec$+ epo*s & f ! pres5t1 & s l>gely has x influ5c$ ! conditions ( man's life4 ,! records ( ! ,glacial epo* are s pla9 & full t we are compell$ to believe :at o!rwise w\ld seem almo/ incr$ible1--t foll[+ ! mild climate ( ! ,t]ti>y came a succession ( ages :5 ice fields1 l t ( ,gre5l&1 %r\d$ ! nor!rn p>ts ( ,nor? ,am]ica & ,europe & ext5d$ f> into temp]ate latitudes4 ,! drift4 ,our /udies ( glaci]s h prep>$ u to deciph] & int]pret ! hi/ory ( ! ,glacial epo*1 z x is record$ 9 ! surface deposits kn[n z ! drift4 ,ov] mo/ ( ,canada & ! nor!rn /ates ?is famili> =mation is expos$ to view 9 ne>ly all cutt+s :i* pass bel[ ! surface soil4 ,! drift includes two di/9ct classes ( deposits1--! un/ratifi$ drift laid d[n by glaci] ice1 & ! /ratifi$ drift spread by glaci] wat]s4 ,! mat]ials ( ! drift are 9 any giv5 place 9 "p unlike ! rock on :i* x re/s4 ,!y _c be d]iv$ f ! und]ly+ rock by wea!r+1 b h be5 br\ght f else:]e4 ,?us :]e a region is und]la9 by s$im5t>y rocks1 z is ! drift-cov]$ area f ! ,hudson ,riv] to ! ,miss\ri1 ! drift conta9s n only fragm5ts ( lime/one1 s&/one1 & %ale ( local d]ivation1 b also pebbles ( _m igne\s & metamorphic rocks1 su* z granites1 gneisses1 s*i/s1 dike rocks1 qu>tzites1 & ! qu>tz ( m9]al ve9s1 ^: ne>e/ s\rce is ! ,ar*ean area ( ,canada & ! /ates ( our nor!rn bord]4 ,! drift receiv$ its "n :5 x 0 suppos$ t ! =mation _h be5 drift$ by floods & iceb]gs f outside s\rces1--a !ory long s9ce ab&on$4 ,illu/ration3 ,fig4 #ceb4 ,/ratifi$ ,drift ov]lay+ ,un/ratifi$ ,drift1 ,massa*usetts ,! di/ribution also ( ! drift po9ts cle>ly to its peculi> orig94 ,)9 ! limits ( ! glaciat$ area x cov]s ! c\ntry )\t reg>d to ! relief1 mantl+ ) its debris n only l[l&s & valleys b also highl&s & m\nta9 slopes4 ,! b\nd>y ( ! drift is equally indep5d5t ( ! relief ( ! l&1 cross+ hills & pla9s imp>tially1 unlike wat]-laid deposits1 ^: m>g9s1 unless subsequ5tly de=m$1 are horizontal4 ,! b\nd>y ( ! drift is /rik+ly lobate also1 b5d+ outw>d 9 broad1 convex curves1 :]e !re are no natural b>ri]s 9 ! topography ( ! c\ntry to set x su* a limit4 ,"u ^! conditions su* a lobate m>g9 _c belong to deposits ( riv]s1 lakes1 or ocean1 b is precisely t :i* w\ld m>k ! edge ( a cont95tal glaci] :i* deploy$ 9 broad tongues ( ice4 ,! rock surface und]ly+ ! drift4 ,ov] mu* ( its area ! drift re/s on firm1 fre% rock1 %[+ t bo? ! preglacial mantle ( residual wa/e & ! p>tially decompos$ & brok5 rock b5ea? x h be5 swept away4 ,! und]ly+ rock1 especially if massive1 h>d1 & ( a f9e gra91 has (t5 be5 gr\nd d[n to a smoo? surface & rubb$ to a poli% z p]fect z t se5 on ! rock beside an ,alp9e glaci] :]e ! ice has rec5tly melt$ back4 ,frequ5tly x has be5 worn to ! smoo?1 r\nd$ hummocks kn[n z ro*es m\tonnes1 & ev5 rocky hills h be5 ?us smoo!d to fl[+ outl9es l ro*es m\tonnes on a gigantic scale4 ,! rock pavem5t b5ea? ! drift is also m>k$ by long1 /raight1 p>allel scor+s1 v>y+ 9 size f deep grooves to f9e /riae z delicate z ! hair l9es cut by an engrav]'s ne$le4 ,:]e ! rock is s(t or closely jo9t$ x is (t5 %att]$ to a dep? ( sev]al feet b5ea? ! drift1 :ile /ony clay has be5 ?ru/ 9 among ! fragm5ts into :i* ! rock is brok54 ,9 ! pres5ce ( ^! glaciat$ surfaces we _c d\bt t ! area ( ! drift has be5 ov]ridd5 by va/ %eets ( ice :i*1 9 _! /eady fl[1 rasp$ & scor$ ! rock b$ b5ea? by means ( ! /ones ) :i* _! basal lay]s 7 inset1 & 9 places pluck$ & %att]$ x4 ,till4 ,! un/ratifi$ portion ( ! drift consi/s *iefly ( %eets ( d5se1 /ony clay call$ till1 :i* cle>ly are ! gr\nd mora9es ( anci5t cont95tal glaci]s4 ,till is an unsort$ mixture ( mat]ials ( all sizes1 f f9e clay & s&1 gravel1 pebbles1 & cobble/ones1 to l>ge b[ld]s4 ,! /ones ( ! till are ( _m k9ds1 "s hav+ be5 pluck$ f ! b$ rock ( ! locality :]e !y are f\nd1 & o!rs hav+ be5 br\ght f outside & (t5 di/ant places4 ,l& ice is ! only ag5t kn[n :i* c spread un/ratifi$ mat]ial 9 su* ext5sive %eets4 ,! f9e mat]ial ( ! till comes f two diff]5t s\rces4 ,9 "p x is d]iv$ f old residual clays1 :i* 9 ! mak+ _h be5 lea*$ ( ! lime & o!r soluble +r$i5ts ( ! rock f :i* !y wea!r$4 ,9 "p x consi/s ( s\nd rock gr\nd f9e2 a drop ( acid on fre%1 clayey till (t5 proves by brisk eff]vesc5ce t ! till conta9s mu* undecay$ lime/one fl\r4 ,! ice %eet1 !re=e1 bo? scrap$ up ! mantle ( long-wea!r$ wa/e :i* cov]$ ! c\ntry be=e its com+1 & also gr\nd heavily ^u ! s\nd rock und]nea?1 & cru%$ & wore to rock fl\r ! fragm5ts :i* x c>ri$4 ,! color ( unwea!r$ till dep5ds on t ( ! mat]ials ( :i* x is compos$4 ,:]e r$ s&/ones h contribut$ l>gely to its mak+1 z ov] ! ,triassic s&/ones ( ! ea/]n /ates & ! ,algonkian s&/ones ab\t ,lake ,sup]ior1 ! drift is r$di%4 ,:5 d]iv$ 9 "p f coaly %ales1 z ov] _m outcrops ( ! ,p5nsylvanian1 x may :5 moi/ be almo/ black4 ,fre% till is normally a dull gray or blui%1 s l>gely is x made up ( ! gr9d+s ( unoxidiz$ rocks ( ^! common colors4 ,except :]e compos$ *iefly ( s& or co>s] /uff1 unwea!r$ till is (t5 exce$+ly d5se4 ,c y sugge/ by :at means x has be5 ?us compact$8 ,did ! ice fields ( ! ,glacial epo* be> heavy surface mora9es l ! m$ial & lat]al mora9es ( valley glaci]s8 ,:]e 0 ! great] "p ( ! load ( ^! ice fields c>ri$1 judg+ f :at y "k ( ! glaci]s ( ,gre5l&8 ,b[ld]s ( ! drift4 ,! pebbles & b[ld]s ( ! drift are 9 "p /ream gravels1 b[ld]s ( wea!r+1 & o!r co>se rock wa/e pick$ up f ! surface ( ! c\ntry by ! advanc+ ice1 & 9 "p are fragm5ts pluck$ f l$ges ( s\nd rock aft] ! mantle ( wa/e _h be5 remov$4 ,_m ( ! /ones ( ! till are dress$ z only glaci] ice c d2 _! %>p edges h be5 blunt$ & _! sides facet$ & scor$4 ,we may easily f9d all /ages ( ?is process repres5t$ among ! pebbles ( ! till4 ,"s are little worn1 ev5 on _! edges2 "s are plan$ & scor$ on "o side only2 :ile "s 9 _! long j\rney h be5 gr\nd d[n to _m facets & h lo/ mu* ( _! orig9al bulk4 ,evid5tly ! ice play$ fa/ & loose ) a /one c>ri$ 9 its basal lay]s1 n[ hold+ x fa/ & rubb+ x aga9/ ! rock b5ea?1 n[ loos5+ its grasp & all[+ ! /one to turn4 ,b[ld]s ( ! drift are sometimes f\nd on high] gr\nd ?an _! p>5t l$ges4 ,?us b[ld]s h be5 left on ! sides ( ,m\nt ,katahd91 ,ma9e1 :i* 7 pluck$ f lime/one l$ges twelve miles di/ant & ?ree ?\s& feet l[] ?an _! re/+ place4 ,9 o!r cases /ones h be5 c>ri$ ov] m\nta9 ranges1 z 9 ,v]mont1 :]e pebbles ( ,burl+ton r$ s&/one 7 dragg$ ov] ! ,gre5 ,m\nta9s1 ?ree ?\s& feet 9 height1 & left 9 ! ,connecticut valley sixty miles away4 ,no o!r geological ag5t ?an glaci] ice c\ld d ?is "w4 ,! b[ld]s ( ! drift are (t5 l>ge4 ,b[ld]s t5 & tw5ty feet 9 diamet] are n uncommon1 & "s are kn[n ^: diamet] exce$s fifty feet4 ,z a rule ! av]age size ( b[ld]s decreases ) increas+ di/ance f _! s\rces4 ,:y8 ,till pla9s4 ,! surface ( ! drift1 :]e left 9 its initial /ate1 also displays cle> pro( ( its glacial orig94 ,ov] l>ge areas x is spread 9 level pla9s ( till1 p]haps b[ld]-dott$1 simil> to ! pla9s ( /ony clay left 9 ,spitzb]g5 by ! rec5t retreat ( "s ( ! glaci]s ( t isl&4 ,9 places ! un/ratifi$ drift is heap$ 9 hills ( v>i\s k9ds1 :i* we w n[ describe4 ,illu/ration3 ,fig4 #ced4 ,map ( a portion ( a ,druml9 ,area ne> ,oswego1 ,new ,york ,druml9s4 ,druml9s are smoo?1 r\nd$ hills compos$ ( till1 elliptical 9 base1 & hav+ _! long] axes p>allel to ! movem5t ( ! ice z %[n by glacial scor+s4 ,!y cr[d c]ta9 di/ricts 9 c5tral ,new ,york & 9 s\!rn ,wiscons91 :]e !y may be c\nt$ by ! ?\s&s4 ,among ! num]\s druml9s ab\t ,bo/on is hi/oric ,bunk] ,hill4 ,druml9s are made ( gr\nd mora9e4 ,!y 7 accumulat$ & giv5 %ape b5ea? ! ov]rid+ ice1 mu* z are s& b>s 9 a riv]1 or 9 "s in/ances 7 c>v$1 l ro*es m\tonnes1 by an ice %eet out ( ! till left by an e>li] ice invasion4 ,t]m9al mora9es4 ,! glaciat$ area is cross$ by belts ( ?ick5$ drift1 (t5 a mile or two1 & sometimes ev5 t5 miles & m1 9 bread?1 :i* lie transv]se to ! movem5t ( ! ice & cle>ly are ! t]m9al mora9es ( anci5t ice %eets1 m>k+ ei!r ! limit ( _! f>!/ advance or pauses 9 _! g5]al retreat4 ,illu/ration3 ,fig4 #cee4 ,t]m9al ,mora9e1 ,/at5 ,isl& ,! surface ( ^! mora9es is a jumble ( elevations & depressions1 :i* v>y f l[1 g5tle swells & %all[ sags to %>p hills1 a hundr$ feet or s 9 height1 & deep1 /eep-sid$ holl[s4 ,su* tumultu\s hills & hummocks1 set ) depressions ( all %apes1 :i* usually are )\t outlet & are (t5 occupi$ by m>%es1 ponds1 & lakes1 surely _c be ! "w ( runn+ wat]4 ,! hills are heaps ( drift1 lodg$ b5ea? ! ice edge or pil$ along its front4 ,! bas9s 7 left among ! tangle ( mora9ic knolls & ridges 7,fig4 #aje7 z ! m>g9 ( ! ice mov$ back & =?4 ,"s b[l-%ap$ bas9s 7 made by ! melt+ ( a mass ( ice left beh9d by ! retreat+ glaci] & buri$ 9 its debris4 ,illu/ration3 ,fig4 #cef4 ,esk]1 ,new ,york ,! /ratifi$ drift4 ,l mod]n glaci]s ! ice %eets ( ! ,plei/oc5e 7 ev] be+ conv]t$ into wat] ab\t _! m>g9s4 ,_! limits on ! l& 7 ! l9es :]e _! onw>d fl[ 0 j balanc$ by melt+ & evaporation4 ,on ! surface ( ! ice along ! m>g9al zone1 rivulets no d\bt fl[$ 9 summ]1 & f\nd _! way ?r\gh crevasses to ! int]ior ( ! glaci] or to ! gr\nd4 ,subglacial /reams1 l ^? ( ! ,malasp9a glaci]1 issu$ f tunnels 9 ! ice1 & wat] ran along ! melt+ ice front z x is se5 to d ab\t ! glaci] tongues ( ,gre5l&4 ,all ^! glaci] wat]s fl[$ away d[n ! *ief dra9age *annels 9 swoll5 riv]s load$ ) glacial wa/e4 ,x is n unexpect$ !re=e t !re are f\nd1 ov] all ! c\ntry :]e ! melt+ ice retreat$1 deposits made ( ! same mat]ials z ! till1 b sort$ & /ratifi$ by runn+ wat]4 ,"s ( ^! 7 deposit$ beh9d ! ice front 9 ice-wall$ *annels1 "s at ! edge ( ! glaci]s by issu+ /reams1 & o!rs 7 spread to long di/ances 9 front ( ! ice edge by glacial wat]s z !y fl[$ away4 ,esk]s are n>r[1 w9d+ ridges ( /ratifi$ s& & gravel ^: g5]al c\rse lies p>allel ) ! movem5t ( ! glaci]4 ,^! ridges1 ?\gh evid5tly laid by runn+ wat]1 d n foll[ l9es ( cont9u\s desc5t1 b may be f\nd to cross riv] valleys & asc5d _! sides4 ,h5ce ! /reams by :i* esk]s 7 laid did n fl[ unconf9$ ^u ! surface ( ! gr\nd4 ,we may inf] t esk]s 7 deposit$ 9 ! tunnels & ice-wall$ gorges ( glacial /reams be=e !y issu$ f ! ice front4 ,illu/ration3 ,fig4 #ceg4 ,kames1 ,new ,york ,kames are s& & gravel knolls1 associat$ = ! mo/ "p ) t]m9al mora9es1 & heap$ by glacial wat]s along ! m>g9 ( ! ice4 ,illu/ration3 ,fig4 #ceh4 ,diagram ,illu/rat+ ! ,=mation ( ,kame ,t]races i1 glaci] ice2 t1 t1 t]races ,kame t]races are hummocky embankm5ts ( /ratifi$ drift sometimes f\nd 9 rugg$ regions along ! sides ( valleys4 ,9 ^! valleys long tongues ( glaci] ice lay sl[ly melt+4 ,glacial wat]s took _! way betwe5 ! edges ( ! glaci]s & ! hillside1 & "h deposit$ s& & gravel 9 rude t]races4 ,outwa% pla9s are pla9s ( s& & gravel :i* frequ5tly bord] t]m9al mora9es on _! outw>d face1 & 7 spread evid5tly by outwa% f ! melt+ ice4 ,outwa% pla9s are sometimes pitt$ by b[l-%ap$ bas9s :]e ice blocks 7 left buri$ 9 ! s& by ! retreat+ glaci]4 ,valley tra9s are deposits ( /ratifi$ drift ) :i* riv] valleys h be5 aggrad$4 ,valleys lead+ outw>d f ! ice front 7 flood$ by glacial wat]s & 7 fill$ (t5 to great dep?s ) tra9s ( /ream-swept drift4 ,s9ce ! disappe>ance ( ! ice ^! glacial flood pla9s h be5 dissect$ by ! %runk5 riv]s ( rec5t times & left on ei!r side ! valley 9 high t]races4 ,valley tra9s head 9 mora9ic pla9s1 & _! mat]ial gr[s f9] d[n valley & co>s] t[>d _! s\rces4 ,_! gradi5t is commonly great] ?an t ( ! pres5t riv]s4 ,! ext5t ( ! drift4 ,! ext5t ( ! drift ( ,nor? ,am]ica & its s\!rn limits are be/ se5 9 ,figure #cei4 ,its area is reckon$ at ab\t f\r million squ>e miles4 ,! ice fields :i* once cov]$ s mu* ( our cont95t 7 all toge!r t5 times z l>ge z ! inl& ice ( ,gre5l&1 & ab\t equal to ! enorm\s ice cap :i* n[ cov]s ! ant>tic regions4 ,! ice field ( ,europe 0 mu* small]1 measur+ ab\t sev5 hundr$ & sev5ty ?\s& squ>e miles4 ,c5t]s ( disp]sion4 ,! direction ( ! movem5t ( ! ice is record$ pla9ly 9 ! scor+s ( ! rock surface1 9 ! %apes ( glaciat$ hills1 9 ! axes ( druml9s & esk]s1 & 9 tra9s ( b[ld]s1 :5 ! l$ges f :i* !y 7 pluck$ c be discov]$4 ,9 ^! ways x has be5 prov$ t 9 ,nor? ,am]ica !re 7 ?ree c5t]s :]e ice ga!r$ to ! greate/ dep?1 & f :i* x fl[$ 9 all directions outw>d4 ,!re 7 ?us ?ree va/ ice fields1--"o ! ,cordill]an1 :i* lay ^u ! ,cordill]as ( ,briti% ,am]ica2 "o ! ,keewat91 :i* fl[$ out f ! prov9ce ( ,keewat91 we/ ( ,hudson ,bay2 & "o ! ,labrador ice field1 ^: c5t] ( disp]sion 0 on ! highl&s ( ! p59sula ( ,labrador4 ,z %[n 9 ,figure #cei1 ! we/]n ice field ext5d$ b a %ort way beyond ! ea/]n foo?ills ( ! ,rocky ,m\nta9s1 :]e p]haps x met ! f>-travel$ ice f ! great c5tral field4 ,! ,keewat9 & ! ,labrador ice fields fl[$ f>!/ t[>d ! s\?1 & 9 ! ,mississippi valley ! "o rea*$ ! m\? ( ! ,miss\ri & ! o!r ne>ly to ! m\? ( ! ,ohio4 ,9 ,m9nesota & ,wiscons9 & nor?w>d !y m]g$ 9 "o va/ field4 ,illu/ration3 ,fig4 #cei4 ,hypo!tical ,map ( ! ,plei/oc5e ,ice ,%eets ( ,nor? ,am]ica ,f ,salisbury's ,glacial ,geology ( ,new ,j]sey ,! ?ickness ( ! ice 0 s great t x buri$ ! highe/ m\nta9s ( ea/]n ,nor? ,am]ica1 z is prov$ by ! transport$ b[ld]s :i* h be5 f\nd ^u _! summits4 ,if ! l& !n /ood at its pres5t height above sea level1 & if ! av]age slope ( ! ice 7 no m ?an t5 feet to ! mile1--a slope s g5tle t ! eye c\ld n detect x & less ?an half ! slope ( ! int]ior ( ! inl& ice ( ,gre5l&1--! ice plateaus ab\t ,hudson ,bay mu/ h rea*$ a ?ickness ( at lea/ t5 ?\s& feet4 ,9 ,europe ! ,sc&9avian plateau 0 ! *ief c5t] ( disp]sion4 ,at ! "t ( greate/ glaciation a cont9u\s field ( ice ext5d$ f ! ,ural ,m\nta9s to ! ,atlantic1 :]e1 (f ! coa/s ( ,norway & ! ,briti% ,isles1 x met ! sea 9 an unbrok5 ice wall4 ,on ! s\? x rea*$ to s\!rn ,engl&1 ,belgium1 & c5tral ,g]many1 & deploy$ on ! ea/]n pla9s 9 wide lobes ov] ,pol& & c5tral ,russia 7,fig4 #cfj74 ,illu/ration3 ,fig4 #cfj4 ,hypo!tical ,map ( ! ,plei/oc5e ,ice ,%eet ( ,europe ,at ! same "t ! ,alps support$ giant glaci]s _m times ! size ( ! surviv+ glaci]s ( to-day1 & a pi$mont glaci] cov]$ ! pla9s ( nor!rn ,switz]l&4 ,! ?ickness ( ! drift4 ,! drift is f> f uni=m 9 ?ickness4 ,x is comp>atively ?9 & scanty ov] ! ,laur5tian highl&s & ! rugg$ regions ( ,new ,engl&1 :ile f s\!rn ,new ,york & ,ont>io we/w>d ov] ! ,mississippi valley1 & on ! great we/]n pla9s ( ,canada1 x exce$s an av]age ( "o hundr$ feet ov] wide areas1 & 9 places has five & six times t ?ickness4 ,x 0 to ?is m>g9al belt t ! ice %eets br\ght _! loads1 :ile nor?w>ds1 ne>] ! c5t]s ( disp]sion1 erosion 0 excessive & deposition slight4 ,successive ice invasions & _! drift %eets4 ,rec5t /udies ( ! drift prove t x does n consi/ ( "o indivisible =mation1 b includes a numb] ( di/9ct drift %eets1 ea* ) its own peculi> features4 ,! ,plei/oc5e epo* consi/$1 !re=e1 ( sev]al glacial /ages1--dur+ ea* ( :i* ! ice advanc$ f> s\?w>d1--toge!r ) ! int]v5+ int]glacial /ages :51 "u a mild] climate1 ! ice melt$ back t[>d its s\rces or :olly disappe>$4 ,illu/ration3 ,fig4 #cfa4 ,diagram illu/rat+ ,crit]ia by :i* ,diff]5t ,drift ,%eets are di/+ui%$ ,! evid5ces ( su* int]glacial /ages1 & ! means by :i* ! diff]5t drift %eets are told ap>t1 are illu/rat$ 9 ,figure #cfa4 ,"h ! c\ntry f ,n to ,s is :olly cov]$ by drift1 b ! drift f ,n to m is s unlike t f m to ,s t we may believe x ! product ( a di/9ct ice invasion & deposit$ dur+ ano!r & f> lat] glacial /age4 ,! =m] drift is v "y1 = its dra9age is z yet immature1 & !re are _m lakes & m>%es ^u its surface2 ! latt] is f> old]1 = its surface has be5 ?or\ghly dissect$ by its /reams4 ,! =m] is b slightly wea!r$1 :ile ! latt] is s old t x is deeply r$d5$ by oxidation & is lea*$ ( its soluble +r$i5ts su* z lime4 ,! y\ng] drift is bord]$ by a di/9ct t]m9al mora9e1 :ile ! m>g9 ( ! old] drift is n ?us m>k$4 ,moreov]1 ! two drift %eets are some:at unlike 9 composition1 & ! diff]5t proportion ( pebbles ( ! v>i\s k9ds ( rocks :i* !y conta9 %[s t _! respective glaci]s foll[$ diff]5t tracks & ga!r$ _! loads f diff]5t regions4 ,aga91 9 places b5ea? ! y\ng] drift !re is f\nd ! buri$ l& surface ( an old] drift ) old soils1 =e/ gr\nds1 & vegetable deposits1 conta9+ ! rema9s ( animals & plants1 :i* tell ( ! climate ( ! int]glacial /age 9 :i* !y liv$4 ,by su* diff]5ces z ^! ! foll[+ drift %eets h be5 made out 9 ,am]ica1 & simil> subdivisions h be5 recogniz$ 9 ,europe4 #e ,! ,wiscons9 =mation #d ,! ,i[an =mation #c ,! ,ill9oian =mation #b ,! ,kansan =mation #a ,! pre-,kansan or ,j]seyan =mation ,9 ,new ,j]sey & ,p5nsylvania ! edge ( a deeply wea!r$ & erod$ drift %eet1 ! ,j]seyan1 ext5ds beyond ! limits ( a mu* y\ng] ov]ly+ drift4 ,x may be ! equival5t ( a deep-buri$ basal drift %eet f\nd 9 ! ,mississippi valley b5ea? ! ,kansan & p>t$ f x by peat1 old soil1 & gravel b$s4 ,! two succe$+ /ages m>k ! greate/ sn[fall ( ! ,glacial epo*4 ,9 ,kansan times ! ,keewat9 ice field sl[ly grew s\?w>d until x rea*$ fifte5 hundr$ miles f its c5t] ( disp]sion & ext5d$ f ! ,arctic ,ocean to nor!a/]n ,kansas4 ,9 ! ,ill9oian /age ! ,labrador ice field /ret*$ f ,hudson ,/raits ne>ly to ! ,ohio ,riv] 9 ,ill9ois4 ,9 ! ,i[an & ! ,wiscons91 ! clos+ /ages ( ! ,glacial epo*1 ! readvanc+ ice fields fell f> %ort ( _! =m] limits 9 ! ,mississippi valley1 b 9 ! ea/]n /ates ! ,labrador ice field dur+ ,wiscons9 times ov]rode = ! mo/ "p all e>li] deposits1 &1 cov]+ ,new ,engl&1 probably met ! ocean 9 a cont9u\s wall ( ice :i* set its b]gs afloat f ,massa*usetts to nor!rn ,labrador4 ,we select = detail$ description ! ,kansan & ! ,wiscons9 =mations z repres5tatives1 ! "o ( ! old] & ! o!r ( ! y\ng] drift %eets4 ,illu/ration3 ,fig4 #cfb4 ,photograph ( ,relief ,map ( ! ,unit$ ,/ates at ! ,"t ( ! ,wiscons9 ,ice ,invasion ,by ! c\rtesy ( ,e4 ,e4 ,h[ell1 ,wa%+ton1 ,d4,c4 ,! ,kansan =mation4 ,! ,kansan drift consi/s = ! mo/ "p ( a %eet ( clayey till c>ry+ small] b[ld]s ?an ! lat] drift4 ,few traces ( druml9s1 kames1 or t]m9al mora9es are f\nd ^u ! ,kansan drift1 & :]e ?ick en\gh to mask ! preexi/+ surface1 x seems to h be5 spread orig9ally 9 level pla9s ( till4 ,! initial ,kansan pla9 has be5 worn by runn+ wat] until !re are n[ left only isolat$ pat*es & ! n>r[ /rips & cre/s ( ! divides1 :i* /ill rise to ! anci5t level4 ,! valleys ( ! l>g] /reams h be5 op5$ wide4 ,_! well-develop$ tribut>ies h c>v$ ne>ly ! entire pla9 to valley slopes 7,figs4 #ej ,b1 & #ei74 ,! lakes & m>%es :i* once m>k$ ! infancy ( ! region h long s9ce be5 effac$4 ,! drift is also deeply wea!r$4 ,! till1 orig9ally blue 9 color1 has be5 yell[$ by oxidation to a dep? ( t5 & tw5ty feet & ev5 m1 & its surface is sometimes ru/$ to t]ra-cotta r$4 ,to a some:at less dep? x has be5 lea*$ ( its lime & o!r soluble +r$i5ts4 ,9 ! wea!r$ zone its pebbles1 especially :]e ! till is loose 9 texture1 are sometimes s rott$ t granites may be crumbl$ ) ! f+]s4 ,! ,kansan drift is !re=e old4 ,illu/ration3 ,fig4 #cfc4 ,pla9 ( ,wiscons9 ,drift1 ,i[a ,! ,wiscons9 =mation4 ,! ,wiscons9 drift %eet is b little wea!r$ & erod$1 & !re=e is extremely "y4 ,oxidation has effect$ x b slightly1 & lime & o!r soluble plant foods rema9 undissolv$ ev5 at ! grass roots4 ,its riv] sy/ems are /ill 9 _! infancy 7,fig4 #ej1 ,a74 ,swamps & peat bogs are abundant on its undra9$ surface1 & to ?is drift %eet belong ! lake l&s ( our nor!rn /ates & ( ! ,laur5tian p5epla9 ( ,canada4 ,! lake bas9s ( ! ,wiscons9 drift are ( sev]al diff]5t classes4 ,_m are %all[ sags 9 ! gr\nd mora9e4 ,/ill m num]\s are ! lakes set 9 holl[s among ! hills ( ! t]m9al mora9es2 su* z ! ?\s&s ( lakelets ( ea/]n ,massa*usetts4 ,inde$1 ! t]m9al mora9es ( ! ,wiscons9 drift may (t5 be r\ghly trac$ on maps by means ( belts ( lakes & ponds4 ,"s lakes are due to ! blockade ( anci5t valleys by mora9ic dbris1 & ?is class includes _m ( ! lakes ( ! ,adirondacks1 ! m\nta9 regions ( ,new ,engl&1 & ! ,laur5tian area4 ,/ill o!r lakes re/ 9 rock bas9s scoop$ out by glaci]s4 ,9 _m cases lakes are due to m ?an "o cause1 z :]e preglacial valleys h bo? be5 bas9$ by ! ice & blockad$ by its mora9es4 ,! ,f+] lakes ( ,new ,york1 = example1 occupy su* glacial tr\ghs4 ,massive t]m9al mora9es1 :i* m>k ! f>!/ limits to :i* ! ,wiscons9 ice advanc$1 h be5 trac$ f ,cape ,cod & ! isl&s s\? ( ,new ,engl&1 across ! ,appala*ians & ! ,mississippi valley1 ?r\gh ! ,dakotas1 & f> to ! nor? ov] ! pla9s ( ,briti% ,am]ica4 ,:]e ! ice halt$ = a "t 9 its g5]al retreat1 x left recessional mora9es1 z ?is v>iety ( ! t]m9al mora9e is call$4 ,! mora9es ( ! ,wiscons9 drift lie ^u ! c\ntry l great fe/oons1 ea* s]ies ( conc5tric loops m>k+ ! utmo/ advance ( broad lobes ( ! ice m>g9 & ! v>i\s pauses 9 _! recession4 ,beh9d ! t]m9al mora9es lie wide till pla9s1 9 places /udd$ ?ickly ) druml9s1 or ridg$ ) an occasional esk]4 ,great outwa% pla9s ( s& & gravel lie 9 front ( ! mora9e belts1 & long valley tra9s ( co>se gravels tell ( ! swift & p[]ful riv]s ( ! "t4 ,! loess ( ! ,mississippi valley4 ,a yell[ e>?1 q l ! loess ( ,*9a1 is laid broadly z a surface deposit ov] ! ,mississippi valley f ea/]n ,nebraska to ,ohio outside ! b\nd>ies ( ! ,i[an & ! ,wiscons9 drift4 ,mu* ( ! loess 0 deposit$ 9 ,i[an times4 ,x is y\ng] ?an ! e>li] drift %eets1 = x ov]lies _! wea!r$ & erod$ surfaces4 ,x ?ick5s to ! ,i[an drift bord]1 b is n f\nd ^u t drift4 ,x is old] ?an ! ,wiscons91 = 9 _m places x passes und]nea? ! ,wiscons9 t]m9al mora9es4 ,9 "p ! loess seems to h be5 wa%$ f glacial wa/e & spread 9 sluggi% glacial wat]s1 & 9 "p to h be5 di/ribut$ by ! w9d f pla9s ( aggrad+ glacial /reams4 ,illu/ration3 ,fig4 #cfd4 ,bank ( ,loess1 ,i[a ,! effects ( ! ice invasions on riv]s4 ,! repeat$ ice invasions ( ! ,plei/oc5e pr(\ndly dis>rang$ ! dra9age sy/ems ( our nor!rn /ates4 ,9 "s regions ! anci5t valleys 7 completely fill$ ) drift4 ,on ! )drawal ( ! ice ! /reams 7 compell$ to f9d _! way1 z be/ !y c\ld1 ov] a fre% l& surface1 :]e we n[ f9d !m fl[+ on ! drift 9 "y1 n>r[ *annels4 ,b hundr$s ( feet bel[ ! gr\nd ! well drill] & ! prospector = coal & oil discov] deep1 wide1 buri$ valleys cut 9 rock1--! *annels ( preglacial & int]glacial /reams4 ,9 places ! anci5t valleys 7 fill$ ) drift to a dep? ( a hundr$ feet1 & sometimes ev5 to a dep? ( f\r hundr$ & five hundr$ feet4 ,9 su* valleys1 riv]s n[ fl[ high above _! anci5t b$s ( rock on floors ( valley drift4 ,_m ( ! valleys ( our pres5t riv]s are b pat*works ( preglacial1 int]glacial1 & po/glacial c\rses 7,fig4 #cff74 ,"h ! riv] w9ds along an anci5t valley ) g5tly slop+ sides & a wide alluvial floor p]haps a mile or s 9 wid?1 & !re x ent]s a "y1 rock-wall$ gorge1 ^: rocky b$ may be cross$ by l$ges ov] :i* ! riv] plunges 9 wat]falls & rapids4 ,illu/ration3 ,fig4 #cfe4 ,preglacial ,dra9age1 ,upp] ,ohio ,valley ,aft] ,*amb]la9 & ,lev]ett ,illu/ration3 ,fig4 #cff4 ,a ,pat*work ,valley a & a1 anci5t c\rses /ill occupi$ by ! riv]2 b1 po/glacial gorge2 c1 anci5t c\rse n[ fill$ ) drift ,9 su* cases x is possible t ! riv] 0 pu%$ to "o side ( its =m] valley by a lobe ( ice1 & compell$ to cut a new *annel 9 ! adjac5t upl&s4 ,a section ( ! valley may h be5 blockad$ ) mora9ic wa/e1 & ! lake =m$ beh9d ! b>ri] may h f\nd outlet ov] ! c\ntry to "o side ( ! anci5t drift-fill$ valley4 ,9 "s in/ances x w\ld seem t dur+ ! wan+ ( ! ice %eets1 glacial /reams1 :ile conf9$ )9 walls ( /agnant ice1 cut d[n ?r\gh ! ice & incis$ _! *annels on ! und]ly+ c\ntry1 9 "s cases be+ let d[n on old riv] c\rses1 & 9 o!r cases excavat+ gorges 9 adjac5t upl&s4 ,plei/oc5e lakes4 ,tempor>y lakes 7 =m$ :]ev] ! ice front damm$ ! natural dra9age ( ! region4 ,"s1 held 9 ! m9or valleys cross$ by ice lobes1 7 small1 & no d\bt _m 7 too %ort-liv$ to leave la/+ records4 ,o!rs1 long held aga9/ ! nor?w>d slop+ c\ntry by ! retreat+ ice edge1 left 9 _! bea*es _! clayey b$s1 & _! outlet *annels p]man5t evid5ces ( _! area & dep?4 ,"s ( ^! glacial lakes are ?us kn[n to h be5 l>g] ?an any pres5t lake4 ,lake ,agassiz1 nam$ 9 honor ( ! au?or ( ! !ory ( cont95tal glaciation1 is suppos$ to h be5 held by ! unit$ front ( ! ,keewat9 & ! ,labrador ice fields z !y f9ally retreat$ d[n ! valley ( ! ,r$ ,riv] ( ! ,nor? & ! dra9age bas9 ( ,lake ,w9nipeg4 ,f fir/ to la/ ,lake ,agassiz cov]$ a hundr$ & t5 ?\s& squ>e miles 9 ,manitoba & ! adjac5t p>ts ( ,m9nesota & ,nor? ,dakota1--an area l>g] ?an all ! ,great ,lakes comb9$4 ,x dis*>g$ its wat]s across ! divide :i* held x on ! s\?1 & ?us excavat$ ! valley ( ! ,m9nesota ,riv]4 ,! lake b$--a pla9 ( till--0 spread smoo? & level z a floor ) lacu/r9e silts4 ,s9ce ,lake ,agassiz vani%$ ) ! melt+ back ( ! ice beyond ! outlet by ! ,nelson ,riv] into ,hudson ,bay1 !re has ga!r$ on its floor a deep humus1 ri* 9 ! nitrog5\s elem5ts s ne$ful = ! gr[? ( plants1 & x is to ?is soil t ! region owes its well-kn[n f]tility4 ,! ,great ,lakes4 ,! bas9s ( ! ,great ,lakes are broad preglacial riv] valleys1 w>p$ by movem5ts ( ! cru/ /ill 9 progress1 enl>g$ by ! erosive action ( lobes ( ! cont95tal ice %eets1 & blockad$ by _! drift4 ,! complicat$ glacial & po/glacial hi/ory ( ! lakes is record$ 9 old /r& l9es :i* h be5 trac$ at v>i\s heights ab\t !m1 %[+ _! areas & ! levels at :i* _! wat]s /ood at diff]5t times4 ,) ! retreat ( ! lobate ,wiscons9 ice %eet t[>d ! nor? & ea/1 ! s\!rn & we/]n ends ( ! bas9s ( ! ,great ,lakes 7 uncov]$ fir/2 & "h1 betwe5 ! rec$+ ice front & ! slopes ( l& :i* fac$ x1 lakes ga!r$ :i* increas$ con/antly 9 size4 ,! lake :i* ?us came to occupy ! we/]n end ( ! ,lake ,sup]ior bas9 dis*>g$ ov] ! divide at ,dulu? d[n ! ,/4 ,croix ,riv]1 z an old outlet *annel proves2 t :i* held ! s\!rn end ( ! bas9 ( ,lake ,mi*igan s5t its ov]fl[ across ! divide at ,*icago via ! ,ill9ois ,riv] to ! ,mississippi2 ! lake :i* cov]$ ! l[l&s ab\t ! we/]n end ( ,lake ,erie dis*>g$ its wat]s at ,=t ,wayne into ! ,waba% ,riv]4 ,! ice /ill block$ ! ,mohawk & ,/4 ,lawr5ce valleys on ! ea/1 :ile on ! we/ x _h retreat$ f> to ! nor?4 ,! lakes become conflu5t 9 wide expanses ( wat]1 ^: dep?s & m>g9s1 z %[n by _! old lake bea*es1 v>i$ at diff]5t times ) ! position ( ! conf9+ ice & ) w>p+s ( ! l&4 ,^! va/ wat] bodies1 :i* at "o or m p]iods 7 great] ?an all ! ,great ,lakes comb9$1 dis*>g$ at v>i\s times across ! divide at ,*icago1 ne> ,syracuse1 ,new ,york1 d[n ! ,mohawk valley1 & by a *annel f ,georgian ,bay into ! ,ottawa ,riv]4 ,la/ ( all ! pres5t outlet by ! ,/4 ,lawr5ce 0 e/abli%$4 ,! bea*es ( ! glacial lakes j m5tion$ are n[ f> f horizontal4 ,t ( ! lake :i* occupi$ ! ,ont>io bas9 has an elevation ( ?ree hundr$ & sixty-two feet above tide at ! we/ & ( six hundr$ & sev5ty-five feet at ! nor!a/1 prov+ "h a diff]5tial movem5t ( ! l& s9ce glacial times am\nt+ to m ?an ?ree hundr$ feet4 ,! bea*es :i* m>k ! successive heights ( ^! glacial lakes are n p>allel2 h5ce ! w>p+ began be=e ! ,glacial epo* clos$4 ,we h already se5 t ! cant+ ( ! region is /ill 9 progress4 ,! ,*ampla9 subsid5ce4 ,z ! ,glacial epo* approa*$ its end1 & ! ,labrador ice field melt$ back = ! la/ "t to ne> its s\rce1 ! l& on :i* ! ice _h la9 9 ea/]n ,nor? ,am]ica 0 s depress$ t ! sea n[ spread f> & wide up ! ,/4 ,lawr5ce valley4 ,x jo9$ ) ,lake ,ont>io1 & ext5d+ d[n ! ,*ampla9 & ,hudson valleys1 made an isl& ( ,new ,engl& & ! m>itime prov9ces ( ,canada4 ,! pro(s ( ?is subsid5ce are f\nd 9 old sea bea*es & sea-laid clays re/+ on ,wiscons9 till4 ,at ,montreal su* t]races are f\nd six hundr$ & tw5ty feet above sea level1 & along ,lake ,*ampla9--:]e ! skeleton ( a :ale 0 once f\nd among !m--at f five hundr$ to f\r hundr$ feet4 ,! heavy delta :i* ! ,mohawk ,riv] built at its m\? 9 ?is arm ( ! sea n[ /&s some?+ m ?an ?ree hundr$ feet above sea level4 ,! clays ( ! ,*ampla9 subsid5ce pass "u wat] ne> ! m\? ( ! ,hudson1 & 9 nor!rn ,new ,j]sey !y occur two hundr$ feet bel[ tide4 ,9 ^! elevations we h measures ( ! w>p+ ( ! region s9ce glacial times4 ,! we/]n ,unit$ ,/ates 9 glacial times4 ,! we/]n ,unit$ ,/ates 0 n cov]$ dur+ ! ,plei/oc5e by any g5]al ice %eet1 b all ! high ranges 7 capp$ ) p]man5t sn[ & n\ri%$ valley glaci]s1 (t5 _m times ! size ( ! exi/+ glaci]s ( ! ,alps4 ,9 almo/ e valley ( ! ,si]ras & ! ,rockies ! records ( ^! vani%$ ice /reams may be f\nd 9 cirques1 glacial tr\ghs1 ro*es m\tonnes1 & mora9ic deposits4 ,x 0 dur+ ! ,glacial epo* t ,lakes ,bonneville & ,lahontan 7 e/abli%$ 9 ! ,great ,bas91 ^: climate mu/ !n h be5 mu* m moi/ ?an n[4 ,illu/ration3 ,fig4 #cfg4 ,a ,valley 9 ! ,driftless ,area ,! driftless area4 ,9 ! upp] ,mississippi valley !re is an area ( ab\t t5 ?\s& squ>e miles 9 s\?we/]n ,wiscons9 & ! adjac5t p>ts ( ,i[a & ,m9nesota1 :i* escap$ ! ice invasions4 ,! rocks are cov]$ ) residual clays1 ! product ( long preglacial wea!r+4 ,! region is an anci5t p5epla91 uplift$ & dissect$ 9 late ,t]ti>y times1 ) mature valleys ^: g5tle gradi5ts are unbrok5 by wat]falls & rapids4 ,?us ! driftless area is 9 /rong contra/ ) ! immature drift topography ab\t x1 :]e lakes & wat]falls are common4 ,x is a bit ( preglacial l&scape1 %[+ ! condition ( ! entire region be=e ! ,glacial epo*4 ,! driftless area lay to "o side ( ! ma9 track ( bo? ! ,keewat9 & ! ,labrador ice fields1 & at ! nor? x 0 protect$ by ! upl& s\? ( ,lake ,sup]ior1 :i* weak5$ & ret>d$ ! movem5t ( ! ice4 ,s\? ( ! driftless area ! ,mississippi valley 0 invad$ at diff]5t times by ice %eets f ! we/1--! ,kansan & ! ,i[an1--& aga9 by ! ,ill9oian ice %eet f ! ea/4 ,aga9 & aga9 ! ,mississippi ,riv] 0 pu%$ to "o side or ! o!r ( its pa?4 ,! anci5t *annel :i* x held along ! ,ill9oian ice front has be5 trac$ ?r\gh s\!a/]n ,i[a = _m miles4 ,illu/ration3 ,fig4 #cfh4 ,cross ,section ( a ,valley 9 ,ea/]n ,i[a a1 c\ntry rock2 b1 ,kansan till2 c1 loess2 t1 t]race ( r$di% s&s & decay$ pebbles above rea* ( pres5t /ream2 s1 /ream2 fp1 flood pla9 ( s4 ,:at is ! age ( rock-cut valley & ( ! alluvium :i* p>tially fills x1 comp>$ ) t ( ! ,kansan till8 ) t ( ! loess8 ,give ! complete hi/ory record$ 9 ! section4 ,b5efits ( glaciation4 ,l ! driftless area1 ! preglacial surface ov] :i* ! ice advanc$ seems to h be5 well dissect$ aft] ! late ,t]ti>y uplifts1 & to h be5 c>v$ 9 _m places to /eep valley slopes & rugg$ hills4 ,! retreat+ ice %eets1 :i* left smoo? pla9s & g5tly roll+ c\ntry ov] ! wide belt :]e glacial deposition exce$$ glacial erosion1 h made travel & transportation easi] ?an !y o!rwise w\ld h be54 ,! preglacial subsoils 7 residual clays & s&s1 compos$ ( ! insoluble elem5ts ( ! c\ntry rock ( ! locality1 ) "s m+l+s ( its soluble p>ts /ill undissolv$4 ,! glacial subsoils are made ( rocks ( _m k9ds1 /ill undecay$ & l>gely gr\nd to p[d]4 ,!y ?us conta9 an inexhau/ible /ore ( ! m9]al foods ( plants1 & 9 a =m made easily ready = plant use4 ,on ! preglacial hillsides ! humus lay] mu/ h be5 comp>atively ?91 :ile ! broad glacial pla9s h ga!r$ deep black soils1 ri* 9 c>bon & nitrog5 tak5 f ! atmosph]e4 ,to ^! soils & subsoils a l>ge "p ( ! weal? & prosp]ity ( ! glaciat$ regions ( our c\ntry mu/ be attribut$4 ,! ice invasions h also add$ v l>gely to ! wat] p[] ( ! c\ntry4 ,! riv]s :i* 9 preglacial times 7 fl[+ ov] grad$ c\rses = ! mo/ "p1 7 pu%$ f _! old valleys & set to fl[ on high] levels1 :]e !y h develop$ wat]falls & rapids4 ,?is p[] w probably be fully utiliz$ long be=e ! coal b$s ( ! c\ntry are exhau/$1 & w become "o ( ! *ief s\rces ( ! national weal?4 ,! ,rec5t epo*4 ,! deposits laid s9ce glacial times graduate into ^? n[ =m+ along ! ocean %ores1 on lake b$s1 & 9 riv] valleys4 ,sl[ & comp>atively slight *anges1 su* z ! w>p+s ( ! region ( ! ,great ,lakes1 h br\ght ab\t ! geographical conditions ( ! pres5t4 ,! physical hi/ory ( ! ,rec5t epo* ne$s "h no special m5tion4 ,! ,life ( ! ,quat]n>y ,dur+ ! entire ,quat]n>y1 inv]tebrates & plants suff]$ little *ange 9 species1--s sl[ly are ^! anci5t & comp>atively simple organisms modifi$4 ,! ,mammalia1 on ! o!r h&1 h *ang$ mu* s9ce ! beg9n+ ( ,quat]n>y "t3 ! v>i\s species ( ! pres5t h be5 evolv$1 & "s l9es h become ext9ct4 ,^! highly organiz$ v]tebrates are evid5tly less /able ?an are l[] types ( animals1 & respond m rapidly to *anges 9 ! environm5t4 ,plei/oc5e mammals4 ,9 ! ,plei/oc5e ! ,mammalia rea*$ _! culm9ation bo? 9 size & 9 v>iety ( =ms1 & 7 sup]ior 9 bo? ^! respects to ! mammals ( to-day4 ,9 ,plei/oc5e times 9 ,nor? ,am]ica !re 7 sev]al species ( bison1--"o ^: widespread+ horns 7 t5 feet f tip to tip1--a gigantic moose elk1 a giant rod5t 7,ca/oroides7 five feet long1 sev]al species ( musk ox51 sev]al species ( horses1--m ak91 h[ev]1 to zebras ?an to ! mod]n horse1--a huge lion1 sev]al sab]-too? tig]s1 imm5se ed5tates ( sev]al g5]a1 & l>ge/ ( all ! ma/odon & mammo?4 ,illu/ration3 ,fig4 #cfi4 ,mega!rium ,illu/ration3 ,fig4 #cgj4 ,glyptodon ,! l>ge/ ( ! ed5tates 0 ! ,mega!rium1 a4 clumsy gr\nd slo? bigg] ?an a rh9oc]os4 ,! bones ( ! ,mega!rium are extraord9>ily massive1--! ?igh bone be+ ?rice z ?ick z t ( an elephant1--& ! animal seems to h be5 well able to get its liv+ by ov]?r[+ trees & /ripp+ (f _! leaves4 ,! ,glyptodon 0 a mail$ ed5tate1 eight feet long1 resembl+ ! little armadillo4 ,^! ed5tates surviv$ f ,t]ti>y times1 & 9 ! w>m] /ages ( ! ,plei/oc5e rang$ nor? z f> z ,ohio & ,oregon4 ,! great proboscidians ( ! ,glacial epo* 7 ab\t ! size ( mod]n elephants1 & some:at small] ?an _! ance/ral species 9 ! ,plioc5e4 ,! ,ma/odon rang$ ov] all ,nor? ,am]ica s\? ( ,hudson ,bay1 b _h become ext9ct 9 ! ,old ,_w at ! end ( ! ,t]ti>y4 ,! elephants 7 repres5t$ by ! ,mammo?1 :i* roam$ 9 imm5se h]ds f our middle /ates to ,alaska1 & f ,arctic ,asia to ! ,m$it]ranean & ,atlantic4 ,x is an (t-told /ory h[ ab\t a c5tury ago1 ne> ! ,l5a ,riv] 9 ,sib]ia1 !re 0 f\nd ! body ( a mammo? :i* _h be5 safely pres]v$ 9 ice = ?\s&s ( ye>s1 h[ ! fle% 0 eat5 by dogs & be>s1 & h[ ! eyes & ho(s & portions ( ! hide 7 tak5 ) ! skeleton to ,/4 ,pet]sburg4 ,s9ce !n sev]al o!r c>casses ( ! mammo?1 simil>ly pres]v$ 9 ice1 h be5 f\nd 9 ! same region1--"o z rec5tly z #aija4 ,we "k f ^! rema9s t ! animal 0 clo!d 9 a coat ( long1 co>se hair1 ) ?ick br[n fur b5ea?4 ,illu/ration3 ,fig4 #cga4 ,skull ( ,musk ,ox1 f ,plei/oc5e ,deposits1 ,i[a ,! di/ribution ( animals & plants4 ,! di/ribution ( species 9 ! ,glacial epo* 0 f> diff]5t f t ( ! pres5t4 ,9 ! glacial /ages arctic species rang$ s\? into :at are n[ temp]ate latitudes4 ,! walrus ?rove along ! %ores ( ,virg9ia & ! musk ox graz$ 9 ,i[a & ,k5tucky4 ,9 ,europe ! re9de] & arctic fox rea*$ ! ,pyr5ees4 ,dur+ ! ,*ampla9 depression arctic %ells liv$ along ! %ore ( ! arm ( ! sea :i* cov]$ ! ,/4 ,lawr5ce valley4 ,9 int]glacial times ( mild] climate ! arctic fauna-flora retreat$1 & _! places 7 tak5 by plants & animals f ! s\?4 ,pecc>ies1 n[ f\nd 9 ,texas1 rang$ into ,mi*igan & ,new ,york1 :ile great slo?s f ,s\? ,am]ica rea*$ ! middle /ates4 ,int]glacial b$s at ,toronto1 ,canada1 conta9 rema9s ( =e/s ( maple1 elm1 & papaw1 ) mollusks n[ liv+ 9 ! ,mississippi bas94 ,:at *anges 9 ! =e/s ( y\r region w\ld be br\ght ab\t1 & 9 :at way1 if ! climate %\ld v gradually gr[ cold]8 ,:at *anges if x %\ld gr[ w>m]8 ,on ! ,alps & ! highe/ summits ( ! ,:ite ,m\nta9s ( ,new ,engl& are f\nd colonies ( arctic species ( plants & insects4 ,h[ did !y come to be ?us sep>at$ f _! home beyond ! arctic circle by a ?\s& miles & m ( temp]ate climate impossible to cross8 ,man4 ,along ) ! rema9s ( ! *>act]i/ic animals ( ! "t :i* are n[ ext9ct !re h be5 f\nd 9 deposits ( ! ,glacial epo* 9 ! ,old ,_w relics ( ,plei/oc5e ,man1 8 bones1 & articles ( 8 manufacture4 ,9 ,europe1 :]e !y h be/ be5 /udi$1 human relics occur *iefly 9 peat bogs1 9 loess1 9 cav]ns :]e man made 8 home1 & 9 high riv] t]races sometimes eighty & a hundr$ feet above ! pres5t flood pla9s ( ! /reams4 ,9 ord] to und]/& ! developm5t ( e>ly man1 we %\ld "k t prehi/oric peoples are rank$ accord+ to ! mat]ials ( :i* _! tools 7 made & ! skill %[n 9 _! manufacture4 ,!re are ?us f\r well-m>k$ /ages ( human culture prec$+ ! writt5 annals ( hi/ory3 #d ,! ,iron /age4 #c ,! ,bronze /age4 #b ,! ,neoli?ic 7rec5t /one7 /age4 #a ,! ,paleoli?ic 7anci5t /one7 /age4 ,9 ! ,neoli?ic /age ! use ( ! metals _h n yet be5 le>n$1 b tools ( /one 7 c>efully %ap$ & poli%$4 ,to ?is /age ! ,nor? ,am]ican ,indian belong$ at ! "t ( ! discov]y ( ! cont95t4 ,9 ! ,paleoli?ic /age1 /one implem5ts 7 *ipp$ to rude %apes & left unpoli%$4 ,?is1 ! l[e/ /ate ( human culture1 has be5 outgr[n by ne>ly e savage tribe n[ on e>?4 ,a /ill e>li] /age may once h exi/$1 :5 man _h n le>n$ s mu* z to %ape 8 weapons to 8 ne$s1 b us$ *ance pebbles & rock spl9t]s 9 _! natural =ms2 ( su* a /age1 h[ev]1 we h no evid5ce4 ,illu/ration3 ,fig4 #cgb4 ,paleoli?ic ,implem5t f ,great ,brita9 ,paleoli?ic man 9 ,europe4 ,x 0 to ! ,paleoli?ic /age t ! e>lie/ m5 belong$ ^: relics are f\nd 9 ,europe4 ,!y _h le>n$ to knock (f two-edg$ flakes f fl9t pebbles1 & to "w !m into simple weapons4 ,! great discov]y _h be5 made t fire c\ld be k9dl$ & made use (1 z ! *>coal & ! /ones discolor$ by heat ( _! anci5t he>?s atte/4 ,caves & %elt]s b5ea? ov]hang+ cliffs 7 _! homes or camp+ places4 ,paleoli?ic man 0 a savage ( ! l[e/ type1 :o liv$ by hunt+ ! wild bea/s ( ! "t4 ,skeletons f\nd 9 c]ta9 caves 9 ,belgium & ,france repres5t p]haps ! e>lie/ race yet f\nd 9 ,europe4 ,^! %ort1 broad-%\ld]$ m51 muscul>1 ) b5t knees & /oop+ gait1 l[-br[$ & small ( bra91 7 ( little intellig5ce & yet truly human4 ,! rema9s ( ,plei/oc5e man are naturally f\nd ei!r 9 cav]ns1 :]e !y escap$ de/ruction by ! ice %eets1 or 9 deposits outside ! glaciat$ area4 ,9 bo? cases x is extremely difficult1 or q impossible1 to assign ! rema9s to def9ite glacial or int]glacial times4 ,_! relative age is be/ told by ! fauna ) :i* !y are associat$4 ,?us ! olde/ relics ( man are f\nd ) ! animals ( ! late ,t]ti>y or e>ly ,quat]n>y1 su* z a species ( hippopotamus & an elephant m anci5t ?an ! mammo?4 ,lat] 9 age are ! rema9s f\nd along ) ! mammo?1 cave be> & cave hy5a1 & o!r animals ( glacial "t :i* are n[ ext9ct2 :ile m rec5t /ill are ^? associat$ ) ! re9de]1 :i* 9 ! la/ ice invasion roam$ widely ) ! mammo? ov] c5tral ,europe4 ,illu/ration3 ,fig4 #cgc4 ,paleoli?ic ,sket* on ,ivory ( ! ,mammo? ,! caves ( s\!rn ,france4 ,^! conta9 ! fulle/ records ( ! race1 mu* l ! ,eskimos 9 bodily frame1 :i* liv$ 9 we/]n ,europe at ! "t ( ! mammo? & ! re9de]4 ,! floors ( ^! caves are cov]$ ) a lay] ( bone fragm5ts1 ! rema9s ( _m meals1 & "h are f\nd also v>i\s articles ( h&icraft4 ,9 ?is way we "k t ! savages :o made ^! caves _! homes fi%$ ) h>poons ( bone1 & hunt$ ) spe>s & d>ts tipp$ ) fl9t & horn4 ,! l>g] bones are split = ! extraction ( ! m>r[4 ,among su* fragm5ts no split human bones are f\nd2 ?is p1 !re=e1 7 n cannibals4 ,bone ne$les imply ! art ( sew+1 & !re=e ! use ( clo?+1 made no d\bt ( sk9s2 :ile v>i\s ornam5ts1 su* z necklaces ( %ells1 %[ h[ anci5t is ! love ( p]sonal adornm5t4 ,pott]y 0 n yet inv5t$4 ,!re is no sign ( agriculture4 ,no animals _h yet be5 dome/icat$2 n ev5 man's e>lie/ fri5d1 ! dog4 ,c]ta9 implem5ts1 p]haps us$ z ! insignia ( (fice1 sugge/ a rude tribal organization & ! beg9n+s ( ! /ate4 ,! rema9s ( fun]al fea/s 9 front ( cav]ns us$ z tombs po9t to a religion & ! belief 9 a life beyond ! grave4 ,9 ! cav]ns ( s\!rn ,france are f\nd also ! beg9n+s ( ! arts ( pa9t+ & ( sculpture4 ,) surpris+ skill ^! ,paleoli?ic m5 sket*$ on bits ( ivory ! mammo? ) 8 long hair & huge curv$ tusks1 fresco$ _! cav]n walls ) pictures ( ! bison & o!r animals1 & c>v$ re9de] on _! dagg] heads4 ,illu/ration3 ,fig4 #cgd4 ,re/oration ( ,head ( ,pi!can?ropus erectus ,e>ly man on o!r cont95ts4 ,paleoli?ic fl9ts curi\sly l ^? ( we/]n ,europe are f\nd also 9 _m regions ( ! ,old ,_w1--9 ,india1 ,egypt1 & ,asia ,m9or1--b5ea? ! e>lie/ ve/iges ( ! civilization ( ^? anci5t seats1 & sometimes associat$ ) ! fauna ( ! ,glacial epo*4 ,9 ,java !re 7 f\nd 9 #ahia1 9 /rata e>ly ,quat]n>y or late ,plioc5e 9 age1 p>ts ( a skeleton ( l[] grade1 if n ( great] antiquity1 ?an any human rema9s n[ kn[n4 ,pi!can?ropus erectus1 z ! creature has be5 nam$1 walk$ erect1 z its ?igh bone %[s1 b ! skull & tee? indicate a close aff9ity ) ! ape4 ,9 ,nor? ,am]ica !re h be5 report$ _m f9ds ( human relics 9 valley tra9s1 loess1 old riv] gravels buri$ b5ea? lava fl[s1 & o!r deposits ( suppos$ glacial age2 b 9 ! op9ion ( "s geologi/s suffici5t pro( ( ! exi/5ce ( man 9 ,am]ica 9 glacial times has n z yet be5 f\nd4 ,^! f9ds 9 ,nor? ,am]ica h be5 discr$it$ = v>i\s reasons4 ,"s 7 n made by sci5tific m5 accu/om$ to ! close/ scrut9y ( e detail4 ,"s 7 report$ aft] a numb] ( ye>s1 :5 ! circum/ances might n be accurately rememb]$2 :ile 9 a numb] ( in/ances x seems possible t ! relics might h be5 work$ into glacial deposits by natural causes f ! surface4 ,man1 we may believe1 witness$ ! great ice fields ( ,europe1 if n ( ,am]ica1 & p]haps appe>$ on e>? "u ! g5ial climate ( preglacial times4 ,no?+ has yet be5 f\nd ( ! l9e ( man's suppos$ desc5t f ! primates ( ! e>ly ,t]ti>y1 ) ! possible exception ( ! ,java rema9s j m5tion$4 ,! /ructures ( man's body %[ t he is n desc5d$ f any ( ! exi/+ g5]a ( apes4 ,& al?\gh he may n h be5 exempt f ! law ( evolution1--t me?od ( creation :i* has made all life on e>? ak91--yet 8 appe>ance 0 an ev5t :i* 9 importance ranks ) ! adv5t ( life ^u ! planet1 & m>ks a new manife/ation ( creative en]gy ^u a high] plane4 ,!re n[ appe>$ intellig5ce1 reason1 a moral nature1 & a capacity = self-direct$ progress su* z _h nev] be5 be=e on e>?4 ,! ,rec5t epo*4 ,! ,glacial epo* ends ) ! melt+ ( ! ice %eets ( ,nor? ,am]ica & ,europe1 & ! replacem5t ( ! ,plei/oc5e mammalian fauna by pres5t species4 ,h[ gradually ! "o epo* %ades into ! o!r is se5 9 ! fact t ! glaci]s :i* /ill l+] 9 ,norway & ,alaska are ! l9eal desc5dants or ! r5ew$ appe>ances ( ! ice fields ( glacial times4 ,our sci5ce _c =etell :e!r all traces ( ! ,great ,ice ,age are to disappe>1 & ! e>? is to enjoy aga9 ! g5ial climate ( ! ,t]ti>y1 or :e!r ! pres5t is an int]glacial epo* & ! nor!rn l&s are comp>atively soon aga9 to be wrapp$ 9 ice4 ,neoli?ic man4 ,! wild ,paleoli?ic m5 vani%$ f ,europe ) ! wild bea/s :i* !y hunt$1 & _! place 0 tak5 by tribes1 p]haps f ,asia1 ( a high] culture4 ,! rema9s ( ,neoli?ic man are f\nd1 mu* z are ^? ( ! ,nor? ,am]ican ,indians1 ^u or ne> ! surface1 9 burial m\nds1 9 %ell heaps 7! refuse heaps ( _! settlem5ts71 9 peat bogs1 caves1 rec5t flood-pla9 deposits1 & 9 ! b$s ( lakes ne> %ore :]e !y sometimes built _! dwell+s ^u piles4 ,! successive /ages 9 ,european culture are well display$ 9 ! peat bogs ( ,d5m>k4 ,! l[e/ lay]s conta9 ! poli%$ /one implem5ts ( ,neoli?ic man1 along ) rema9s ( ! ,scot* fir4 ,above are oak trunks ) implem5ts ( bronze1 :ile ! high] lay]s hold iron weapons & ! rema9s ( a bee* =e/4 ,neoli?ic man 9 ,europe _h le>n$ to make pott]y1 to sp9 & weave l951 to hew timb]s & build boats1 & to gr[ :eat & b>ley4 ,! dog1 horse1 ox1 %eep1 goat1 & hog _h be5 dome/icat$1 &1 z ^! species are n kn[n to h exi/$ be=e 9 ,europe1 x is a fair inf]5ce t !y 7 br\ght by man f ano!r cont95t ( ! ,old ,_w4 ,neoli?ic man knew no?+ ( ! art ( extract+ ! metals f _! ores1 nor _h he a writt5 language4 ,! ,neoli?ic /age ( culture passes by ins5sible gradations into t ( ! age ( bronze1 & ?us into ! ,rec5t epo*4 ,9 ! ,rec5t epo* ! progress ( man 9 language1 9 social organization1 9 ! arts ( life1 9 morals & religion1 has left ample records :i* are = o!r sci5ces ?an ours to read2 "h1 !re=e1 geology gives place to ar*ology & hi/ory4 ,our brief /udy ( ! outl9es ( geology has giv5 u1 x is hop$1 "s great & la/+ good4 ,to conceive a pa/ s diff]5t f ! pres5t has /imulat$ ! imag9ation1 & to foll[ ! inf]5ces by :i* ! conclusions ( our sci5ce h be5 rea*$ has ex]cis$ "o ( ! noble/ faculties ( ! m9d1--! reason4 ,we h le>n$ to look on nature 9 new ways3 e l&scape1 e pebble n[ has a mean+ & tells some?+ ( its orig9 & hi/ory1 :ile plants & animals h a clos] int]e/ s9ce we h trac$ ! long l9es ( _! desc5t4 ,! n>r[ horizons ( human life h be5 brok5 ?r\gh1 & we h caught glimpses ( t immeasurable rea* ( "t 9 :i* nebulae & suns & planets run _! c\rses4 ,moreov]1 we h le>n$ some?+ ( t ord]ly & _w-embrac+ progress by :i* ! once un9habitable globe has come to be man's well-appo9t$ home1 & life appe>+ 9 ! l[lie/ =ms has /eadily develop$ high] & /ill high] types4 ,see+ ?is process ent] human hi/ory & lift our race cont9ually to l(ti] levels1 we f9d reason to believe t ! onw>d1 upw>d movem5t ( ! geological pa/ is ! manife/ation ( ! same wise ,p[] :i* makes = righte\sness & good & t ?is unceas+ purpose w /ill lead on to nobl] ends4 ,,index ,aa1 lava1 #bda ,acadian coal field1 #ced ,accretion hypo!sis1 #cjd ,acidic rocks1 #bdi ,adelsb]g grotto1 #dg ,adirondacks1 #cji1 #caf ,africa1 #ceg ,agassiz1 ,lake1 #fg1 #aaa1 #dce ,agates1 #bea ,alabama1 #cag1 #cfj ,alaska1 #he1 #ach1 #adj1 #cgh ,alets* glaci]1 #aba ,alg1 #ea1 #eb ,algonkian era1 #cjf1 #caj ,allegh5y ,m\nta9s1 #ij1 #bbd1 #cbf1 #djc ,alluvial cones1 #ih ,alluvium1 #fb ,alps1 #aah1 #aba1 #ada1 #baj1 #baa1 #bab1 #bbc1 #bbi1 #cdi1 #dbg1 #ddc ,amazon ,riv]1 #age ,ammonites1 #bid1 #cfg1 #chj1 #chb ,amphibians1 #cfd1 #chc ,amphicyon1 #dac ,amygdules1 #bej ,&es1 #bcf1 #bgi ,angle ( repose1 #be ,ant>ctic cont95t1 #bid ,antec$5t /reams1 #bji ,antelope1 #dac ,an?racite1 #bha ,anticl9al folds1 #bjc1 #bji ,ants1 #bj ,ap5n9e ,m\nta9s1 #cii ,appala*ia1 #cag1 #cea1 #ceh ,appala*ian coal field1 #cef ,appala*ian de=mation1 #ceh ,appala*ian ,m\nta9s1 #baa1 #bad1 #bah1 #bib ,aquif]1 #dd ,aragonite1 #bif ,ar*opt]yx1 #cic ,ar*ean era1 #cje ,ar5ace\s rocks1 #i ,argillace\s rocks1 #i ,arizona1 #cb1 #gf1 #adj1 #aea1 #afd1 #bbj1 #bbi1 #bdi1 #beg1 #cga1 #cij ,arkansas1 #ccg1 #cef1 #cgc ,arkose1 #ahf1 #bhb1 #cgj ,artesian wells1 #dd ,ar?ropods1 #cbb ,artiodactyls1 #daa ,ass9ibo9e1 ,m\nt1 #cd ,atlas ,m\nta9s1 #cii ,atmosph]e1 #cjd1 #cje ,atolls1 #aia1 #aic ,augite1 #bgd ,au/91 ,tex41 #ga ,au/ralia1 #aij1 #ceg ,avalan*es1 #bf ,bad ,l&s1 #cig1 #cih ,baltic ,sea1 #agj1 #aga1 #aii ,b>ite1 #bhg ,b>ri] ,reefs1 #aia1 #aib ,basal conglom]ate1 #agc1 #ahd ,basalt1 #bdi ,baselevel1 #hj1 #hc ,basic rocks1 #bdi ,bas9 deposits1 #ajc ,bay b>s1 #afd ,bea*es1 #afb1 #afd ,be>s1 #dac ,b$d+ planes1 #e ,belemnites1 #chb ,belt ,m\nta9s1 #cji ,b]gs*rund1 #aba1 #ace1 #acg ,b]mudas1 #adh ,birds1 #cib ,bison1 #dac ,bitt] ,root ,m\nta9s1 #bgb ,black ,hills1 #cji1 #cga ,bla/oids1 #cci ,bla/osph]e1 #caa ,block m\nta9s1 #bbb1 #bbf ,bl[holes1 #aei ,blue ,ridge1 #cji1 #caf ,bomb1 volcanic1 #bef ,bonneville1 ,lake1 #ajg1 #dhh ,bosses1 #bgj ,b[ld]s1 erratic1 #dbj ( wea!r+1 #bh ,bra*iopods1 #cbh1 #chc1 #cdc1 #cfd1 #chj ,brazil1 #ah1 #bhf ,breccia1 #bah1 #bee1 #bfd ,briti% ,columbia1 #cgc1 #cgh ,bronze /age1 #ddc1 #ddh ,bryozoans1 #ccc ,bunk] ,hill1 #dbb ,calamites1 #cfa1 #cfg ,calc>e\s rocks1 #i ,calcif]\s s]ies1 #cbg ,calcite1 #bij ,cald]a1 #bci ,cali=nia1 #bd1 #ii1 #ahf1 #aeb1 #aeh1 #afi1 #agj1 #aig1 #bbd1 #bef1 #bfb1 #bhg1 #ceg1 #cfj1 #cga1 #djj ,great ,valley (1 #aja1 #aii1 #cgb1 #cif ,cambrian p]iod1 #cae glaciation 91 #ceh life (1 #cai ,camels1 #dab ,canada1 #bh1 #hf1 #fg1 #fi1 #ij1 #ahb1 #aih1 #bjj1 #bah1 #bah1 #bfg1 #cjg1 #cji1 #caf1 #ccf1 #cfd1 #cfg1 #dhb1 #dhg ,cape ,breton ,isl&1 #aih ,cape ,cod1 #afb ,c>bonat$ spr+s1 #bfa ,c>bonates1 =mation (1 #ab ,c>bonif]\s p]iod1 #cej life (1 #cja ,c>nivores1 #dah ,cascade ,m\nta9s1 #jj1 #djj ,cats1 #dah ,catskill ,m\nta9s1 #cdb ,caucasus ,m\nta9s1 #cii ,cav]ns1 #df1 #bda ,c5ozoic era1 #cid ,c5tip$es1 #chh ,cephalopods1 #cbd1 #chh1 #chi1 #cdd1 #cfg1 #chj ,c]atites1 #chj ,c]atosaurus1 #che ,*a9 coral1 #chi1 #hdc ,*alcopyrite1 #bhg ,*alk1 #i1 #cgd1 #cge ,*alybeate spr+s1 #fb ,*ampla9 subsid5ce1 #dhg ,*>le/on e>?quake1 #bhh ,*azy s]ies1 #cbg ,*elan1 ,lake1 #ada ,*emung s]ies1 #cda1 #cdb ,*esapeake ,bay1 #afi1 #agj1 #aig ,*icago1 #adf1 #aih1 #dhf ,*ile1 #bhf ,*9a1 #bh1 #afa ,*ri/mas ,isl&1 #aid1 #bdh ,c9c9nati anticl9e1 #cbi1 #cff ,cirques1 #acf ,cl9ton s]ies1 #ccf ,coal1 #cfb1 #cgj1 #cge ,coal ,measures1 #cea ,coa/ ,range1 #aja1 #cgb1 #cii ,coa/al pla91 ,atlantic1 #ahh ,coel5t]ates1 #cbj ,coke1 #bga ,colorado1 #ah1 #bi1 #hh1 #hg1 #aeh1 #bhh1 #bff1 #bga1 #ccd ,colorado plateaus1 #ceg1 #djc ,colorado ,riv]1 #hj1 #gf1 #adj1 #aed1 #bbh1 #cjg1 #cah1 #cag ,columbia lavas1 #djj ,column> /ructure1 #bfh ,concretions1 #di ,cones1 alluvial1 #ih volcanic1 #bfg ,conglom]ate1 #i1 #agh ,congo ,riv]1 #age ,conif]s1 #cgg ,connecticut1 #cgj valley1 #djh ,contemporane\s lava %eets1 #bdh1 #bfh ,cont95tal delta1 #agf1 #ahc ,cont95tal %elf1 #ahc ,cont95ts1 #ahh ,cont\rs1 #fj ,copp]1 #bhg1 #caj ,coqu9a1 #agg ,coral reefs1 #ahh ,corals1 anci5t1 #cba1 #ccb1 #cch1 #cgi ,cordaites1 #cfc ,cordill]an ice field1 #dbf ,cornif]\s s]ies1 #cda ,coves1 #afa ,crabs1 #cgi ,cr&all volcano1 #bfh1 #djj ,crat] ,lake1 #bei ,creodonts1 #dah ,cretace\s p]iod1 #cgb ,cr9oids1 #chb1 #cjc1 #cgi ,crocodiles1 #chd ,cross b$d+1 #fe1 #ahb ,cru/acea1 #cbb1 #chb1 #cfh1 #cgi ,cru/al movem5ts1 #aie ,cumb]l& plateau1 #ij ,cup corals1 #chh ,cycads1 #cgg1 #cgh ,cycle ( erosion1 #hd1 #ahe1 #bib ,cy/oids1 #cba1 #chb1 #cfg ,dalmatia1 #agj ,d>w9's !ory ( coral reefs1 #aia ,dead ,sea1 #bba1 #bgi ,dea? ,gul*1 #bfd ,deep-sea deposits1 #ahg ,de]1 #dac ,deflation1 #aeb ,de=mation1 #bgi ,delaw>e ,riv]1 #aig1 #djc ,deltas1 #ajh1 #aaa1 #aig ( ,ganges1 #aji ( ,indus1 #aaj ( ,mississippi1 #aji1 #aig ,d5udation1 #eg ,d5v]1 #cih ,des]t1 #ae1 #ee ,devitrification1 #beg ,devonian p]iod1 #caf1 #cda ,dicotyls1 #cgg1 #djd ,digitigrade1 #djf ,dikes1 #bdd1 #bfe ,d9osaurs1 #che ,d9o!re1 #daj ,diorite1 #bgd ,dip1 #bjb ,dip fault1 #bbe ,diplodocus1 #bhf ,dipnoans1 #cdf ,disc9a1 #cbd ,dismal ,swamp1 #ajf ,dogs1 #dac ,dragon flies1 #cfd ,drift1 #ah1 #aac1 #daf b[ld]s (1 #dbj englacial1 #abe ext5t (1 #dbe pebbles (1 #aad1 #dbj /ratifi$1 #dbc ?ickness (1 #dbi ,driftless area1 #dch ,dr[n$ valleys1 #aig ,druml9s1 #dba ,dulu?1 #dcf ,dunes1 #adg ,du/ falls1 #ade ,e>?1 age (1 #bib1 #bih1 #cjb int]ior (1 #bgf ,e>?quakes1 #bbd1 #bcc causes (1 #bcc1 #bcg ,*>le/on1 #bcc di/ribution (1 #bcf geological effects (1 #bcd ,india1 #bcf ,japan1 #bcg ,new ,madrid1 #bcf ,e>?worms1 #bj1 #ba ,e*9od]ms1 #cba1 #ccb1 #ccc1 #cdc1 #cfc ,ed5tates1 #dda ,egypt1 #ih ,electric ,peak1 #bfi ,elephants1 #daj ,elevation1 effects (1 #he movem5ts (1 #aig ,eoc5e epo*1 #cie ,epicont95tal seas1 #cah ,erratics1 #acc1 #dbj ,esk]s1 #dbd ,etna1 #bdh1 #djb ,europe1 ,plei/oc5e ice %eet (1 #dbg ,eurypt]ids1 #ccc1 #cci1 #cfc1 #cfg ,evolution1 #cjj1 #ddg ,facet$ pebbles1 #aac1 #aad1 #dbj ,falls ( ! ,ohio1 #cdc ,fan folds1 #bje ,fault sc>ps1 #bai ,faults1 #bag ,faunas1 #bii ,feldsp>1 #i1 #aj1 #db ,f]ns1 #cfa ,f+] lakes1 #dcb ,fire clay1 #cec ,fi%es1 #ccd1 #cci1 #cde1 #cfd1 #dje ,fissure eruptions1 #bdb ,fissure spr+s1 #dd ,fjords1 #aci1 #adb ,fl9t1 #ah1 #cge ,flood pla9s1 #he1 #ic ,floods1 #ed ,floras1 #bii ,florida1 #df1 #afc1 #agg1 #agh1 #ahh1 #cif ,fl[ l9es1 #beb ,fluorite1 #bhg ,fold$ m\nta9s1 #baj ,folds1 #bja1 #bjh ,foliation1 #bhc ,=am9if]a1 #ahg1 #cgd3 ,=e/s1 ,c>bonif]\s1 #ced1 #cfa ,cretace\s1 #cgg1 #cgh ,devonian1 #cdc ,t]ti>y1 #djd ,=t ,wayne1 #dcf ,fossils1 #agg1 #bif ,fractures1 #bae ,fragm5tal rocks1 #h ,france1 #afg1 #aga cave m5 (1 #dde ,fr++ reefs1 #aij ,frogs1 #chc ,fro/1 #ae ,fundy1 ,bay (1 #ahb ,gabbro1 #bgd ,ganges1 #eh1 #aji1 #aig ,ganoids1 #cdg ,g>net1 #bha ,gases1 volcanic1 #bdd ,ga/ropods1 #cbd ,ga/rula1 #caa ,g5eva1 ,lake1 #ga ,geodes1 #di ,geological "t1 divisions (1 #bie ,geology1 def9ition (1 #a1 #c dep>tm5ts (1 #d ,georgia1 #ah1 #cgc ,geys]s1 #eb1 #bfj ,glacial epo*1 #adb1 #daf ,glaci]s1 #aac abrasion by1 #acc ,alp9e1 #aah comp>$ ) riv]s1 #acg1 #adb crevasses (1 #abc deposition by1 #ach ,gre5l&1 #aaf l[] limit (1 #abi melt+ (1 #abf mode ( =mation1 #aah mora9es1 #abd motion (1 #abj1 #abb1 #acd pi$mont1 #aca1 #ada pluck+ by1 #acc tables1 #acj transportation by1 #acb tr\ghs1 #acg wells1 #abi "y & mature1 #abi ,glauconite1 #agf ,globig]9a ooze1 #ahg ,glyptodon1 #dda ,gneiss1 #bhc ,goats1 #dac ,gold1 #bhg1 #cgb ,goniatite1 #cdd1 #cfg ,grad$ slopes1 #be ,granite1 #i1 #bgd ,graphite1 #cab ,graptolites1 #cbj1 #cci ,gravitation1 #bb ,great ,bas91 #ceg1 #cfj1 #cgd1 #cgf ,great ,lakes1 #aih1 #dcf ,great ,pla9s1 #hb ,great ,salt ,lake1 #ajg ,gre5l&1 #aae1 #abf1 #cgh ,gre5 ,m\nta9s1 #cji1 #caf1 #dbj ,gre5 s&1 #agf ,gr\nd wat]1 #ci ,gr\nd wat] surface1 #dj ,grypha1 #cgi ,gymnosp]ms1 #cfc1 #cgg ,gypsum1 #ab1 #cce1 #ceg1 #cga ,hade1 #bag ,hamilton s]ies1 #cda ,hang+ valley1 #achi ,hang+ wall1 #bag ,h>tz ,m\nta9s1 #bad ,hawaiian volcanoes1 #bch1 #bdh1 #beh1 #bgi ,heat & cold1 #ac ,held]b]g s]ies1 #cda ,hematite1 #caj ,h5ry ,m\nta9s1 #bga1 #cgf ,high ,pla9s1 #ajj1 #cih ,hill]s ,m\nta91 #bga ,himalaya ,m\nta9s1 #abb1 #bji1 #baj1 #cii ,hi/orical geology1 #d1 #bia ,honeycomb corals1 #cci ,hood1 ,m\nt1 #bfj1 #bfb ,hooks1 #afe ,hornbl5de1 #bgd ,hornbl5de s*i/1 #bhd ,hudson ,bay1 #ij1 #agj ,hudson ,riv]1 #aig1 #dag ,hudson s]ies1 #cbg1 #cbi ,humus acids1 #aj ,humus lay]1 #ai ,huronian sy/ems1 #cjh ,hwang-ho ,riv]1 #aea ,hydrosph]e1 #bb ,hydrozoa1 #cbj ,iceb]gs1 #aaf1 #adh ,icel&1 #bdb1 #beh ,i*?yosaurus1 #chi ,idaho1 #cd1 #djj ,igne\s rocks1 #i1 #bdi1 #bej1 #bea1 #bgc ,ill9oian =mation1 #dbi ,ill9ois1 #ed1 #adf1 #cef1 #cgd ,india1 #bh1 #ajb1 #adg1 #bce1 #ceg1 #djb ,indian ,t]ritory1 #cef ,indiana1 #dh1 #ajd ,indo-,gangetic pla91 #aja ,indus ,riv]1 #aja1 #aaj ,insects1 #ccc1 #cfd1 #chj ,int]ior ( e>?1 #bgf ,int]nal geological ag5cies1 #aie ,intrusive masses1 #bgj ,intrusive rocks1 #bgc ,intrusive %eets1 #bfh ,inv]ness e>?quake1 #bcf ,i[a1 #bi1 #fi1 #gc1 #hj1 #hf1 #ccf1 #cef1 #cgd1 #dca1 #dcc1 #dci1 #ddb ,i[an =mation1 #dbi ,iron ores1 #ac1 #ec1 #bgi1 #caj ,isl&s1 coral1 #ahh wave cut1 #aei1 #afa ,japan1 #bbc1 #bbd1 #bcg ,jo9ts1 #e1 #ca1 #baf ,jordan valley1 #bgi ,jura ,m\nta9s1 #ada1 #bab ,jurassic p]iod1 #cfi ,kame t]races1 #dbd ,kames1 #dbd ,kansan =mation1 #dbi ,kansas1 #da1 #ej1 #ajj1 #ccf1 #ceg1 #cgc1 #cgd1 #dbi ,kaol91 #ab ,k>/1 #dg ,katahd91 ,m\nt1 #dbj ,keewat9 ice field1 #dbe ,k5tucky1 #de1 #df1 #cdc1 #ddb ,kewe5awan sy/em1 #cjh1 #caj ,kilauea1 #bci ,k+s ,riv] ,canyon1 #djc ,krakatoa1 #bde ,labrador1 #aih ,labrador ice field1 #dbf ,laccoli?1 #bga ,lagoon1 #afe1 #afg ,lahontan1 ,lake1 #ajg1 #dch ,lake ,*elan1 #ada ,lake dwell+s1 #ddh ,lake ,g5eva1 #ga ,lake ,sup]ior region1 #bhd1 #cjh1 #caj ,lakes1 #gj1 #bbb1 #dcb bas9s1 #ig1 #aaj1 #abg1 #aci1 #ada1 #afd1 #afe1 #afg1 #aia1 #bba1 #bbb1 #bce1 #bei1 #dbc1 #dcb1 #dce deposits1 #ajd glacial1 #abg1 #aci1 #ada1 #dbc1 #dcb1 #dce ,plei/oc5e1 #dce salt1 #ajf ,lam91 #e ,l&slides1 #bf1 #bcd ,lapilli1 #bee ,l>amie s]ies1 #cge ,laur5tian p5epla91 #hd1 #cjh1 #dcb ,lava1 #bch1 #bda ,lava domes1 #bdc1 #djj ,lepidod5dron1 #cfb1 #cfg ,li*5s1 #af ,lignite1 #bga ,lime/one1 #g1 #agg1 #agh1 #aij ,limonite1 #ac ,l+ulella1 #cbd ,li?osph]e1 #ba ,liz>ds1 #chd ,llamas1 #dab ,loess1 #aej1 #dcc ,long ,isl&1 #cgc ,l\isiana1 #ccf1 #cif ,l[] ,silurian p]iod1 #cbg ,luray ,cav]n1 #dh ,lycopods1 #cfb ,magnetite1 #bgi1 #caj ,ma9e1 #afi1 #dbj ,malasp9a glaci]1 #aha ,maldive ,ar*ipelago1 #aih ,mammals1 #cic1 #djf1 #ddj ,mammo?1 #ddb ,mammo? ,cave1 #df ,mammo? ,hot ,spr+s1 #eb ,man1 #dad1 #ddc ,mantle ( wa/e1 #ag ,m>ble1 #bhd1 #cbi ,m>5go ,cav]n1 #dh ,m>l1 #ajd ,m>supials1 #cic1 #djf ,m>?a's ,v9ey>d1 #afa1 #cgc1 #cie ,m>yl&1 #ef1 #bgj ,massa*usetts1 #ajf1 #afb1 #beg1 #cji1 #djh1 #dag1 #dbi ,ma/odon1 #daj1 #dda1 #ddb ,matt]horn1 #cd ,maturity ( l& =ms1 #hj ,mauna ,loa1 #bci ,me&]s1 #if ,m$9a s]ies1 #cce1 #djc ,mega!rium1 #dda ,m5dota1 ,lake1 #ga ,mesa1 #ca1 #cb1 #aec ,mesozoic era1 #cfi ,mesozoic p5epla91 #cgf1 #djc ,metamorphism1 #bha ,mexico1 #cgc1 #cge ,mica1 #i ,mica s*i/1 #bhd ,mi*igan1 #ajd1 #cef1 #ddc ,mi*igan1 ,lake1 #adi1 #aih ,m9]al ve9s1 #di1 #bhf ,m9nesota1 #ig1 #dbf ,mioc5e s]ies1 #cie ,mississippi1 #ccg ,mississippi embaym5t1 #cgc1 #cgd1 #cie ,mississippi ,riv]1 #ef1 #eg1 #hb1 #id1 #if1 #aji ,mississippian s]ies1 #cej ,miss\ri1 #ah1 #bcf ,miss\ri ,riv]1 #ee1 #ig ,mobile ,bay1 #aig ,mohawk valley1 #dcf1 #dcg ,mollusc\s %ell deposits1 #agg ,mollusks1 #cbd ,monadnock1#hc ,monkeys1 #dad ,monocl9al fold1 #bjd ,monocotyls1 #cgg1 #djd ,monotremes1 #cic1 #djf ,montana1 #ga1 #cji1 #cac1 #cgc ,montreal1 #bfh1 #dcg ,monum5ts1 #cc ,mora9es1 #abd ,mosasaurs1 #cij ,m\nta9 %eep1 #dac ,m\nta9s1 age (1 #bbi life hi/ory 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