,transcrib]'s ,note ,italic text is d5ot$ by und]scores & bold text by equal signs4 ,:ole & p>tial numb]s are display$ z #b-a_/b4 ,illu/ration3 ,photo1 ,ridge ,/udio2 ,c\rtesy ,ogd5 ,*amb] ( ,comm]ce ,a great l$ge 9 ,ogd5 ,canyon ne> ,ogd51 ,utah4 ,! rock1 /ill reta9+ its /ratification1 0 deposit$ lay] ^u lay] horizontally mo/ly z s& ^u ! floor ( a sea :i* cov]$ ! region fully #be1jjj1jjj ye>s ago4 ,t ! sea 0 ( v e>ly ,paleozoic 7i4e41 ,cambrian7 age has be5 prov$ by fossils 9 associat$ /rata4 ,long aft] _! deep burial & consolidation )9 ! e>?1 ! /rata 7 subject$ to trem5d\s m\nta9-mak+ pressure1 notably alt]$ to a rock call$ ,qu>tzite1 rais$ high above sea level1 & tilt$ almo/ v]tically4 ,!n ?r\gh long ages 7millions ( ye>s7 ov]ly+ rocks ( great ?ickness h be5 cut away 7erod$7 by wea!r+ & /ream action1 lay+ b>e ! l$ge z we see x to-day4 ,popul> ,sci5ce ,libr>y ,,editor-,,9-,,*ief ,,g>rett ,p4 ,,s]viss ,,au?ors ,,william ,j4 ,,mill] ,,hippolyte ,,gru5] ,a4 ,,russell ,,bond ,d4 ,w4 ,,h]+ ,,loomis ,,havemey] ,,erne/ ,g4 ,,m>t9 ,,ar?ur ,,selwyn-,,br[n ,,rob]t ,,*5ault ,,givl] ,,erne/ ,,+]soll ,,wilfr$ ,,mason ,,b>ton ,,william ,b4 ,,scott ,,erne/ ,j4 ,,/reubel ,,norman ,,taylor ,,david ,,todd ,,*>les ,,fitzhugh ,,talman ,,rob9 ,,bea* ,,arrang$ ,,9 ,,sixte5 ,,volumes ,,) ,a ,,hi/ory ,,( ,,sci5ce1 ,,gloss>ies ,,& ,a ,,g5]al ,,index ,,illu/rat$ ,illu/ration ,,volume ,,?ree ,p4 ,f4 ,,colli] ,,son ,,company ,,new ,,york ,copyright #aibb ,by ,p4 ,f4 ,colli] ,son ,company ,,manufactur$ ,,9 ,u4 ,s4 ,a4 ,,geology ,! ,sci5ce ( ! ,e>?'s ,cru/ ,,by ,,william ,j4 ,,mill] ,pr(essor ( ,geology1 ,smi? ,college ,illu/ration ,p4 ,f4 ,,colli] ,,son ,,company ,,new ,,york ,,preface ,9 ! prep>ation ( ?is book ! au?or has attempt$ to pres5t1 9 popul> =m1 ! sali5t po9ts ( a g5]al survey ( ! :ole great sci5ce ( geology1 ! sci5ce :i* deals ) ! hi/ory ( ! e>? & its inhabitants z reveal$ 9 ! rocks4 ,! use ( te*nical & unusual t]ms has be5 r$uc$ to a m9imum compatible ) a reasonable und]/&+ ( ! subject by ! layman4 ,ea* ( ! relatively few sci5tific t]ms is expla9$ :]e fir/ us$ 9 ! text1 & a gloss>y ( common geological t]ms has be5 app5d$4 ,! matt] ( illu/rations has receiv$ v c>eful att5tion1 & only pictures1 maps1 & diagrams are us$ :i* actually illu/rate important features ( ! text4 ,a special po9t has be5 made to introduce only cuts ( simple con/ruction comp>atively free f te*nicalities4 ,ne>ly e illu/ration is accompani$ by a really explanatory title4 ,a numb] ( ! pictures are f ! au?or's collection ( photographs1 & _m ( ! l9e-cuts h ei!r be5 made or consid]ably modifi$ by ! au?or4 ,among ! num]\s s\rces ( illu/rations1 special m5tion %\ld be made ( ! ,unit$ ,/ates ,geological ,survey1 ! ,new ,york ,/ate ,museum1 ! ,am]ican ,museum ( ,natural ,hi/ory1 ! ,univ]sity ( ,*icago ,press1 & v>i\s individuals1 full cr$it be+ giv5 :]ev] due4 ,william ,j4 ,mill]4 ,nor?ampton1 ,mass4 ,,cont5ts ,,*apt] ,,page ,i4 ,introduction #i ,,ii4 ,wea!r+ & ,erosion #bb ,,iii4 ,/ream ,"w #cj ,,iv4 ,! ,sea & ,its ,"w #ea ,v4 ,glaci]s & ,_! ,"w #ei ,,vi4 ,! ,action ( ,w9d #ga ,,vii4 ,in/ability ( ! ,e>?'s ,cru/ #gf ,,viii4 ,volcanoes & ,igne\s ,rocks #ii ,,ix4 ,wat]s ,)9 ! ,e>? #aac ,x4 ,h[ ,m\nta9s ,come & ,g #acj ,,xi4 ,a ,/udy ( ,lakes #adb ,,xii4 ,h[ ! ,e>? ,may ,h ,orig9at$ #aeh ,,xiii4 ,v ,anci5t ,e>? ,hi/ory #afd ,,xiv4 ,anci5t ,e>? ,hi/ory #agi ,,xv4 ,m$ieval ,e>? ,hi/ory #bjh ,,xvi4 ,mod]n ,e>? ,hi/ory #bba ,,xvii4 ,evolution ( ,plants #bdi ,,xviii4 ,geological ,hi/ory ( ,animals 7,exclud+ ,v]tebrates7 #bei ,,xix4 ,geological ,hi/ory ( ,v]tebrate ,animals 7,includ+ ,man7 #bha ,,xx4 ,m9]alogy #cjg ,,xxi4 ,economic ,geology #cdb ,gloss>y ( ,common ,geological ,t]ms #cgg ,,li/ ,,( ,,illu/rations ,l$ge ( ,rock ) ,ne>ly ,v]tical ,/rata ,frontispiece ,,plate ,,fac+ ,,page #a ,granite ,wea!r+ to ,soil ,leav+ ,residual ,cores ( ,jo9t ,blocks 7,upp] picture7 #cb ,look+-,glass ,rock1 ,utah4 ,/ratifi$ ,s&/one ,sculptur$ by ,w9d ,erosion 7,l[] picture7 #cb #b ,gr& ,canyon ( ! ,yell[/one ,riv]4 ,a ,*annel ,worn by ,erosion #cc #c ,gorge ( ! ,niag>a ,riv] ,bel[ ! ,falls4 ,a ,sample ( ,rec5t ,erosion #fd #d ,w9d+ ,/ream 9 ! ,/4 ,lawr5ce ,valley ) ,flood ,pla9 7,upp] picture7 #fe ,davidson ,glaci]1 ,alaska1 ,%[+ ,action on ! ,valley's ,walls & ,floor 7,l[] picture7 #fe #e ,swift ,curr5t ,valley 9 ,glaci] ,national ,p>k1 ,=m$ by ,/ream & ,glaci] ,action #if #f ,yosemite ,valley f ,we/]n ,entrance4 ,! ,result ( ,glacial ,action #ig #g ,an ,upb5d ,fold or ,anticl9e 9 ,m>yl& #abh #h ,l$ge ( ,igne\s ,rock ,%[+ ,jo9ts 7,upp] picture7 #abi ,fault ,fracture 9 ,lime/one ,=mations 7,l[] pictures7 #abi #i ,molt5 ,lava ,fl[+ ,ov] a ,cliff 9 ,hawaii 7,upp] picture7 #afj ,dikes ( ,granite ,cutt+ ,old ,rock 7,l[] picture7 #afj #aj ,lass5 ,peak1 ,cali=nia1 9 ,eruption 7,left picture7 #afa ,devil's ,t[]1 ,wyom+1 ,once a ,mass ( ,molt5 ,rock ,=c$ ,?r\gh ,/rata 7,"r picture7 #afa #aa ,mammo? ,hot ,spr+s ,t]race 9 ,yell[/one ,national ,p>k 7,upp] picture7 #bbd ,crat] ,lake1 ,oregon1 ,=m$ by ! ,subsid5ce ( a ,volcano 7,l[] picture7 #bbd #ab ,ar*eozoic ,rock1 ,olde/ ,kn[n ,rock ,=mation on ,e>? 7,upp] picture7 #bbe ,twi/$ ,mass ( ,/ratifi$ ,lime/one1 ,surr\nd$ by ,granite 7,l[] picture7 #bbe #ac ,paleozoic ,rock1 ,cov]$ ) ,olde/ ,kn[n ,animal ,rema9s #bef #ad ,/one-,lily ,/ems 9 ,ordovician ,/rata 7,upp] left picture7 #beg ,v>i\s ,bra*iopods 9 ,ordovician ,/rata 7,upp] "r picture7 #beg ,/ratifi$ ,lime/one ( ,middle ,ordovician ,era ,conta9+ ,fossils 7,l[] picture7 #beg #ae ,a ,l&scape ( ! ,coal ,age 7,upp] picture7 #bhh ,fossil ,f]n on a ,piece ( ,%ale 7,l[] picture7 #bhh #af ,re/oration ( ,huge ,animals ( ! ,mesozoic ,era #bhi #ag ,skeleton ( ,two-,legg$ ,c>nivor\s ,d9osaur 7,l>ge picture7 #cbj ,e>lie/ ,kn[n ,bird ,=m 7,ins]t7 #cbj #ah ,skeleton ( ,l>ge ,fly+ ,reptile 7,upp] picture7 #cba ,skeleton ( a ,swimm+ ,reptile ( ! ,mesozoic ,era 7,l[] picture7 #cba #ai ,appala*ians ,along ,new ,riv]1 ,p5epla9 ,uprais$ ,aga9 #ceb #bj ,glacial ,b[ld] ,left by ,ice ,%eet 7,upp] picture7 #cec ,esk]1 ,deposit$ by a ,/ream 9 ! ,great ,glaci] 7,l[] picture7 #cec ,,*apt] ,i ,,introduction ,e>? features are n fix$4 ,! p]son ( ord9>y intellig5ce1 surr\nd$ z he is by a great v>iety ( physical features1 is1 unless he has devot$ "s /udy to ! subject1 v likely to reg>d ^? features z practically un*angeable1 & to ?9k t !y are n[ ess5tially z !y 7 9 ! beg9n+ ( ! e>?'s hi/ory4 ,"s ( ! mo/ fundam5tal ideas taught 9 ?is book are t ! physical features ( ! e>?1 z we behold !m to-day1 repres5t b a s+le phase ( a v long-cont9u$ hi/ory2 t significant *anges are n[ go+ on all ar\nd u2 & t we are able to int]pret pres5t-day e>? features only by an und]/&+ ( e>? *anges 9 ! pa/4 ,geology1 mean+ lit]ally e>? sci5ce1 deals ) ! hi/ory ( ! e>? & its inhabitants z reveal$ 9 ! rocks4 ,! sci5ce is v broad 9 its scope4 ,x treats ( ! processes by :i* ! e>? has be51 & is n[ be+1 *ang$2 ! /ructure ( ! e>?2 ! /ages ?r\gh :i* x has pass$2 & ! evolution ( ! organisms :i* h liv$ ^u x4 ,geography deals ) ! di/ribution ( ! e>?'s physical features1 9 _! relation to "o ano!r1 to ! life ( sea & l&1 & human life & culture4 ,x is ! pres5t & outw>d expression ( geological effects4 ,z a result ( ! "w ( _m able /ud5ts ( geology dur+ ! pa/ c5tury & a qu>t]1 x is n[ well e/abli%$ t our planet has a def9itely record$ hi/ory ( _m millions ( ye>s1 & t dur+ ! lapse ( ^? eons1 revolution>y *anges 9 e>? features h occurr$1 & also t !re has be5 a va/ succession ( liv+ ?+s :i*1 f v e>ly times1 h gradually pass$ f simple into m & m complex =ms4 ,! physical *anges & ! organisms ( pa/ ages h left abundant evid5ce ( _! "*1 & ! /udy ( ! rock =mations has %[n t )9 !m we h a fairly complete record ( ! e>?'s hi/ory4 ,al?\gh v mu* yet rema9s to be le>n$ ab\t ?is old e>?1 x is a rem>kable fact t man1 ?r\gh ! ex]cise ( 8 highe/ faculty1 has come to "k s mu* conc]n+ x4 ,! foll[+ words1 by ! late ,pr(essor ,b>rell1 admirably summ>ize ! significance ( geological hi/ory4 ,! great lesson taught by ! /udy ( ! out] cru/ is t ! e>? "m1 l h] *ildr51 has atta9$ h] pres5t =m ?r\gh ceaseless *ange1 :i* m>ks ! pulse ( life & :i* %all cease only :5 h] int]nal =ces slumb] & ! cl\dy air & surf-b\nd ocean no m are mov+ g>m5ts4 ,! fl[+ l&scapes ( geologic "t may be lik5$ to a k9etoscopic panorama4 ,! sc5es trans=m f age to age1 z f act to act2 seas & pla9s & m\nta9s ( diff]5t types foll[ & replace ea* o!r ?r\gh "t1 z ! travel] sees !m succe$ ea* o!r 9 space4 ,at times ! drama ha/5s1 & unusual rapidity ( geologic action has1 9 fact1 m>k$ ^? epo*s s9ce man has be5 a spectator ^u ! e>?4 ,sci5ce demon/rates t m\nta9s are transitory =ms1 b ! eye ( man ?r\gh all 8 lifetime sees no *ange1 & 8 reason is appall$ at ! conception ( a duration s va/ t ! mill5iums ( writt5 hi/ory h n accompli%$ ! %ift+ ( ev5 "o ( ! fleet+ views :i* bl5d into ! mov+ picture4,a ,a ,c5tral ,connecticut 9 ! ,geologic ,pa/1 pp4 #a-b4 ,or 9 ! words ( ,t5nyson3 ,!re rolls ! deep :]e grew ! tree4 ,o1 e>?1 :at *anges ha/ ?\ se56 ,!re :]e ! long /reet ro>s1 ha? be5 ,! /illness ( ! c5tral sea4 ,! hills are %ad[s1 & !y fl[ ,f =m to =m1 & no?+ /&s2 ,!y melt l mi/1 ! solid l&s1 ,l cl\ds !y %ape !mselves & g4 ,! foll[+ /atem5t ( "s ( ! m def9ite important conclusions reg>d+ e>? *anges may s]ve to make /ill cle>] ! g5]al scope ( ! sci5ce ( geology4 ,! evid5ces ^u :i* ^! conclusions are bas$ are discuss$ 9 v>i\s p>ts ( ?is book4 ,= untold millions ( ye>s ! rocks at & ne> ! e>?'s surface h be5 crumbl+2 /reams h be5 incessantly saw+ into ! l&s2 ! sea has be5 eat+ into cont95tal masses2 ! w9ds h be5 sculptur+ des]t l&s2 &1 m int]mitt5tly & locally1 glaci]s h pl[$ ?r\gh m\nta9 valleys1 & ev5 great %eets ( ice h spread ov] consid]able portions ( cont95ts4 ,?r\gh\t geologic "t1 ! cru/ ( ! e>? has %[n m>k$ in/ability4 ,sl[ upw>d & d[nw>d movem5ts ( ! l&s relative to sea level h be5 v common1 9 _m cases am\nt+ to ev5 ?\s&s ( feet4 ,v>i\s p>ts ( ! e>? h be5 notably affect$ by sudd5 movem5ts 7result+ 9 e>?quakes7 along fractures 9 ! out] cru/4 ,dur+ millions ( ye>s molt5 mat]ials h1 at v>i\s times1 be5 =c$ into ! e>?'s cru/1 & 9 _m cases to its surface4 ,m\nta9 ranges h be5 br\ght =? & cut d[n4 ,! site ( ! ,appala*ian ,m\nta9s 01 millions ( ye>s ago1 ! bottom ( a %all[ sea4 ,lakes h come & gone4 ,! ,great ,lakes h come into exi/5ce v rec5tly 7geologically71 t is to say1 s9ce ! great ,ice ,age4 ,a /udy ( /ratifi$ rocks ( m>9e orig9 %[s t all1 or ne>ly all1 ( ! e>?'s surface has at "s "t1 or times1 be5 cov]$ by sea wat]4 ,ov] c]ta9 di/ricts ! sea has transgress$ & retrogress$ repeat$ly4 ,organisms h inhabit$ ! e>? = _m millions ( ye>s4 ,9 e>li] kn[n geologic "t1 ! plants & animals 7 comp>atively simple & l[ 9 ! scale ( organization1 & ?r\gh ! succe$+ ages high] & m complex types 7 gradually evolv$ until ! highly organiz$ =ms ( ! pres5t "t1 includ+ ! human race1 7 produc$4 ,! rocks ( ! e>? con/itute ! special field ( /udy = ! geologi/ because !y conta9 ! records ( ev5ts ?r\gh :i* ! e>? & its inhabitants h pass$ dur+ ! millions ( ye>s ( "t until _! pres5t conditions h be5 rea*$4 ,all ! rocks ( ! e>?'s cru/ may be divid$ into ?ree great classes3 igne\s1 s$im5t>y1 & metamorphic4 ,igne\s rocks comprise all ^? :i* h ev] be5 9 a molt5 condition1 & ( ^! we h ! volcanic rocks 7= example1 lavas71 :i* h cool$ at or ne> ! surface2 plutonic rocks 7= example1 granites71 :i* h cool$ 9 great masses at consid]able dep?s bel[ ! surface2 & ! dike rocks :i*1 :5 molt51 h be5 =c$ into fissures 9 ! e>?'s cru/ & !re cool$4 ,s$im5t>y rocks comprise all ^? :i* h be5 deposit$ "u wat]1 except "s w9d-bl[n deposits1 & !y are ne>ly always arrang$ 9 lay]s 7/ratifi$74 ,su* rocks are call$ /rata4 ,!y may be ( me*anical orig9 su* z clay or mud :i* h>d5s to %ale2 s&1 :i* consolidates into s&/one2 & gravel1 :i* :5 cem5t$ becomes conglom]ate4 ,!y may be ( organic orig9 su* z lime/one1 mo/ ( :i* is =m$ by ! accumulation ( calc>e\s %ells2 fl9t & *]t1 :i* are accumulations ( silice\s %ells2 or coal1 :i* is =m$ by ! accumulation ( p>tly decay$ organic matt]4 ,or1 f9ally1 !y may be =m$ by *emical precipitation1 z b$s ( salt1 gypsum1 bog iron ore1 etc4 ,metamorphic rocks include bo? s$im5t>y & igne\s rocks :i* h be5 notably *ang$ f _! orig9al condition4 ,traces or rema9s ( plants & animals pres]v$ 9 ! rocks are kn[n z fossils4 ,! t]m orig9ally meant any?+ dug out ( ! e>?1 :e!r organic or inorganic1 b = _m ye>s x has be5 /rictly appli$ to organic rema9s4 ,_m ?\s&s ( species ( fossils are kn[n f rocks ( all ages except ! olde/1 & m are con/antly be+ br\ght to light1 b ^! repres5t only a small "p ( ! life ( pa/ ages because relatively few organic rema9s 7 deposit$ "u conditions favorable = pres]vation 9 fossil =m4 ,! fossils 9 ! rocks are1 h[ev]1 a fair av]age ( ! gr\ps ( organisms to :i* !y belong4 ,x is really rem>kable t su* a va/ numb] ( fossils are imb$d$ 9 ! rocks1 & f a /udy ( ^! _m fundam5tal conclusions reg>d+ ! hi/ory ( life on our planet may be drawn4 ,z e>ly z ! fif? c5tury ,b4 ,c41 ,x5ophanes is said to h obs]v$ fossil %ells & plants 9 ! rocks ( ,p>os1 & to h attribut$ _! pres5ce to incursions ( ! sea ov] ! l&4 ,h]odotus1 ab\t a c5tury lat]1 came to a simil> conclusion reg>d+ fossil %ells 9 ! m\nta9s ( ,egypt4 ,none ( ! anci5ts1 h[ev]1 seem$ to h ! slighte/ conception ( ! significance ( fossils z "t m>k]s 9 ! hi/ory ( ! e>?4 7,see discussion bel[47 ,9 ! ,middle ,ages1 di/+ui%$ writ]s held curi\s views reg>d+ fossils4 ,?us ,avic5na 7#ihj-ajcg7 believ$ t fossils repres5t$ unsuccessful attempts on ! "p ( nature to *ange inorganic mat]ials into organisms )9 ! e>? by a peculi> creative =ce 7vis pla/ica74 ,ab\t two c5turies lat]1 ,alb]tus ,magnus held a some:at simil> view4 ,leon>do da ,v9ci 7#adeb-aeai71 ! fam\s arti/1 ar*itect1 & eng9e]1 :ile engag$ 9 canal build+ 9 nor!rn ,italy1 saw fossils imb$d$ 9 ! rocks1 & conclud$ t ^! 7 ! rema9s ( organisms :i* actually liv$ 9 sea wat] :i* spread ov] ! region4 ,dur+ ! sev5te5? & eighte5? c5turies1 _m correctly held t fossils 7 really ( organic orig91 b x 0 commonly taught t all fossils repres5t$ rema9s ( organisms ( an e>li] creation :i* 7 buri$ 9 ! rocks dur+ ! great ,deluge 7,noah's ,flood74 ,william ,smi? 7#agfi-ahci71 ( ,engl&1 01 h[ev]1 ! fir/ to recognize ! fundam5tal significance ( fossils = det]m9+ ! relative ages ( s$im5t>y rocks4 ,?is discov]y laid ! f\ndation = ! det]m9ation ( e>? *ronology :i* is ( great importance 9 ! /udy ( ! hi/ory ( ! e>?4 7,see discussions bel[47 ,organic rema9s1 dat+ z f> back z t5s ( millions ( ye>s1 h be5 pres]v$ 9 ! rocks ( ! e>? 9 v>i\s ways4 ,a v common k9d ( fossilization is ! pres]vation ( only ! h>d p>ts ( organisms4 ,?us ! s(t p>ts h disappe>$ by decomposition1 :ile ! h>d p>ts1 su* z bones1 %ells1 etc41 rema94 ,9 _m cases practically complete skeletons ( l>ge & small animals :i* liv$ millions ( ye>s ago h be5 f\nd intact 9 ! rocks4 ,fossils :i* %[ none ( ! orig9al mat]ial1 b only ! %ape or =m1 are also v abundant4 ,:5 s$im5t h>d5s ar\nd an imb$d$ organism1 & ! organism !n decomposes or dissolves away1 a cavity or fossil mold only is left4 ,ca/s ( organisms or p>ts ( !m are =m$ by fill+ %ells or molds ) s$im5t or ) m9]al matt] c>ri$ 9 solution by und]gr\nd wat]4 ,only r>ely h ca/s ( :olly s(t animals be5 f\nd 9 anci5t rocks4 ,9 o!r cases bo? orig9al =m & /ructure are pres]v$1 b none ( ! orig9al mat]ial4 ,?is is kn[n z petrifaction :i* takes place :5 a plant or h>d "p ( an animal has be5 replac$1 p>ticle by p>ticle1 by m9]al matt] f solution 9 und]gr\nd wat]4 ,n uncommonly organic matt]1 su* z wood1 or inorganic matt]1 su* z c>bonate ( lime %ells1 has be5 s p]fectly replac$ t ! orig9al /ructures are pres]v$ almo/ z 9 life4 ,! popul> idea t petrifi$ wood is wood :i* has be5 *ang$ into /one is1 ( c\rse1 incorrect4 ,x is d\btful if fle% has ev] be5 truly petrifi$4 ,9 _m cases ma9ly ! c>bon only ( organisms has be5 pres]v$4 ,?is is also true ( plants :]e1 "u conditions ( sl[ *emical *ange or decomposition1 ! hydrog5 & oxyg5 mo/ly disappe>1 leav+ mu* ( ! c>bon ) orig9al /ructures (t5 rem>kably pres]v$4 ,f9e examples are fossil plants 9 ! great coal-be>+ /rata4 ,mu* m r>ely entire organisms h be5 pres]v$ ei!r by freez+ or by natural embalmm5t4 ,mo/ rem>kable are ! species ( mammo?s & rh9oc]oses1 ext9ct = ?\s&s ( ye>s1 bodies ( :i*1 ) fle%1 hide1 & hair /ill intact1 h be5 held 9 cold /orage 9 ! froz5 soils ( ,sib]ia1 or o!r cases4 ,insects h be5 p]fectly pres]v$ 9 amb]1 z1 = example1 9 ! ,baltic region4 ,?is amb] is a h>d5$ res9 9 :i* ! insects 7 caught :ile x 0 /ill s(t & exud+ f ! trees4 ,f9ally1 we %\ld m5tion ! pres]vation ( tracks & trails ( l& & wat] animals4 ,?\s&s ( tracks ( long-ext9ct great reptiles occur 9 ! s&/ones & %ales ( ! ,connecticut ,valley ( ,massa*usetts4 ,! footpr9ts 7 made 9 s(t s&y mud :i* h>d5$ & !n became cov]$ ) m s$im5t4 ,few fossils occur 9 o!r ?an ! s$im5t>y rocks4 ,mo/ num]\s1 by f>1 are fossils 9 rocks ( m>9e orig91 because on relatively %all[ sea bottoms1 :]e s$im5ts ( ! geologic ages h l>gely accumulat$1 ! conditions = fossilization h be5 mo/ favorable4 ,among ! _m conditions :i* h produc$ great div]sity 9 numb]s & di/ribution ( m>9e organisms dur+ geologic "t are temp]ature1 dep? ( wat]1 cle>ness ( wat]1 nature ( sea bottom1 degree ( sal9ity1 & food supply4 ,riv] & lake deposits also n uncommonly conta9 rema9s ( organisms :i* inhabit$ ! wat]s1 b also o!rs :i* 7 c>ri$ 94 ,surr\nd+ trees drop _! leaves1 fl[]s1 & fruit ^u ! mud flats1 insects fall into ! quiet wat]s1 :ile quadrup$s are mir$ 9 mud or quicks& & soon buri$ out ( sight4 ,flood$ /reams br+ 9 quantities ( vegetable debris1 toge!r ) c>casses ( l& animals dr[n$ by ! sudd5 rise ( ! flood 7,w4 ,b4 ,scott74 ,9 ! /udy ( ! _m *anges :i* h tak5 place 9 ! hi/ory ( ! e>?1 a fundam5tal consid]ation is ! det]m9ation ( ! relative ages ( ! rocks1 especially ! /rata4 ,h[ c ! geologi/ assign a rock =mation ( any "p ( ! e>? to a p>ticul> age 9 ! hi/ory ( ! e>?8 ,h[ c x be prov$ t c]ta9 rock =mations 9 v>i\s p>ts ( ! e>? orig9at$ practically at ! same "t8 ,!re are two important crit]ia4 ,fir/1 9 any region :]e ! /rata h n be5 di/urb$ f _! normal ord]1 ! old] /rata und]lie ! y\ng] because ! und]ly+ s$im5ts mu/ h be5 deposit$ fir/4 ,n[1 ! total ?ickness ( ! /ratifi$ s]ies ( ! e>? has be5 e/imat$ to be no less ?an #bjj1jjj feet & only a small "p ( ?is is actually pres5t 9 any giv5 locality or region4 ,x is1 !re=e1 evid5t t ! ord] ( sup]position ( /rata is 9 itself n suffici5t = ! det]m9ation ( ! relative ages ( all ! /rata 9 ev5 a consid]able portion ( a s+le cont95t1 n to m5tion its utt] inadequacy 9 build+ up ! geological column ( ! :ole e>?4 ,:51 h[ev]1 ! second crit]ion1 namely1 ! fossil cont5t ( ! /rata1 is us$ 9 direct connection ) ! ord] ( sup]position1 we h ! real basis = det]m9+ ! relative ages ( /rata = all p>ts ( ! e>?4 ,! discov]y ( ?is me?od 0 v l>gely due to ! pa9/ak+ field "w 9 ,engl& by ,william ,smi? ab\t ! beg9n+ ( ! n9ete5? c5tury4 ,x is a well-e/abli%$ fact t organisms h inhabit$ ! e>? = _m millions ( ye>s & t1 ?r\gh ! geologic ages1 !y h cont9u\sly *ang$1 ) gradual developm5t ( high] & high] types4 ,t5s ( ?\s&s ( species h come & gone4 ,accept+ ?is fact1 x is !n cle> t /rata :i* 7 =m$ at notably diff]5t times mu/ conta9 notably diff]5t fossils1 :ile /rata :i* accumulat$ at practically ! same "t conta9 simil> fossils1 all[+1 ( c\rse1 = reasonable diff]5ces 9 geographical di/ribution ( organisms z at ! pres5t "t4 ,ea* epo* ( e>? hi/ory or s]ies ( /rata has its *>act]i/ic assemblage ( organisms4 ,9 %ort1 a geological *ronology is con/ruct$ by c>efully det]m9+1 fir/ ( all1 ! ord] ( sup]position ( ! /ratifi$ rocks1 & next by le>n+ ! fossils *>act]i/ic ( ea* gr\p ( /rata4444 ,! ord] ( succession among ! fossils is det]m9$ f ! ord] ( sup]position ( ! /rata 9 :i* !y occur4 ,:5 t succession has be5 ?us e/abli%$1 x may be employ$ z a g5]al /&>d 7,w4 ,b4 ,scott74 ,x %\ld1 h[ev]1 be borne 9 m9d t precise contemporaneity ( /rata 9 widely sep>at$ di/ricts c r>ely1 if ev]1 be det]m9$ because ( ! v great l5g? ( geologic "t & ! g5]al sl[ness ( ! evolution ( organisms4 ,rocks c>ry+ rem>kably simil> fossils may really be sev]al ?\s& ye>s diff]5t 9 age2 b ?is is1 inde$1 a v small limit ( error :5 "o consid]s ! va/ antiquity ( ! e>?4 ,mu* v accurate & satisfactory "w has be5 done1 especially 9 ,europe & ,nor? ,am]ica1 9 correlat+ /rata & assign+ !m to _! places 9 ! geological "t table 7see bel[71 b a va/ am\nt ( "w yet rema9s to be done be=e ! task is complete4 ,c]ta9 types or species ( organisms are mu* m useful ?an o!rs 9 ! det]m9ation ( e>? *ronology4 ,be/ ( all = _w-wide correlations are species :i* 7 widely di/ribut$ & :i* p]si/$ = relatively %ort times4 ,?us any species :i* liv$ 9 ! surface wat]s ( ! ocean & 0 easily di/ribut$ ov] wide areas1 :ile1 at ! same "t1 x exi/$ z su* only a %ort "t1 is ! be/ type ( *ronologic indicator4 ,! kn[n hi/ory ( ! e>? has be5 m or less def9itely divid$ into great eras & less] p]iods & epo*s1 con/itut+ :at may be call$ ! geologic "t scale4 ,9 ! accompany+ table ! era & p]iod names1 except ^? repres5t+ e>li] "t1 are mo/ly _w-wide 9 _! usage4 ,epo* names1 be+ m or less locally appli$1 are omitt$ f ! table4 ,v cons]vative e/imates ( ! l5g? ( "t repres5t$ by ! eras & ! mo/ *>act]i/ic g5]al features ( ! life ( ! ma9 divisions are also giv54 ,,pr9cipal ,,divisions ,,( ,,geologic ,,"t 7,modifi$ aft] ,u4 ,s4 ,geological ,survey47 ,millions ,era4 ,p]iod4 ,*>act]i/ic life4 ( ye>s e/imat$ ---------------------------------------- ------------------------------ ,age ( man4 ,animals & plants ,quat]n>y4 ( mod]n types4 ---------------------------------------- ---------- ,c5ozoic ,age ( mammals4 ,rise ( highe/ #c to #e4 ,t]ti>y4 animals except man4 ,rise & developm5t ( highe/ ord]s ( plants4 ---------------------------------------- ------------------------------ ,age ( reptiles4 ,rise & ,cretace\s4 culm9ation ( huge l& reptiles 7d9osaurs71 ( %ellfi% ) complexly p>tition$ coil$ --------------%ells 7ammonites71 & ( great fly+ reptiles4 ,fir/ appe>ance ,mesozoic ,jurassic4 79 ,jurassic7 ( birds & mammals2 #e to #aj4 ( cycads1 an ord] ( palm-l --------------plants 79 ,triassic72 & ( angiosp]m\s plants1 among ,triassic4 :i* are palms & h>dwood trees 79 ,cretace\s74 ---------------------------------------- ------------------------------ ,age ( amphibians4 ,dom9ance ( ,p]mian4 club mosses 7lycopods7 & plants --------------( horsetail & f]n types4 ,primitive fl[]+ plants & ,p5nsylvanian4e>lie/ cone-be>+ trees4 ,beg9n+s ( back-bon$ l& --------------animals 7l& v]tebrates74 ,insects4 ,mississippian4,animals ) nautiluslike coil$ %ells 7ammonites7 & %>ks abundant4 ---------------------------------------- ---------- ,age ( fi%es4 ,%ellfi% ,devonian4 7mollusks7 also abundant4 ,rise ( amphibians & l& plants4 ---------------------------------------- ---------- ,a ,%ell-=m+ sea animals dom9ant1 g especially ^? relat$ to e ! nautilus 7cephalopods74 ,rise ,paleozoic & culm9ation ( ! m>9e #ag to #be4 ,silurian4 o animals sometimes kn[n z sea f lilies 7cr9oids7 & ( giant scorpionlike cru/aceans ,i 7eurypt]ids74 ,rise ( fi%es & n ( reef-build+ corals4 -----------n---------------------------- --------- v ,%ell-=m+ sea animals1 e especially cephalopods & ,ordovician4r mollusk-l bra*iopods1 abundant4 t ,culm9ation ( ! buglike m>9e e cru/aceans kn[n z trilobites4 -----------b---------------------------- --------- r ,trilobites & bra*iopods mo/ ,cambrian4 a *>act]i/ic animals4 ,seawe$s t 7alg7 abundant4 ,no trace ( e l& animals f\nd4 ----------------------s----------------- ----------------------------- ,fir/ life t has left di/9ct ,prot]ozoic,algonkian4 record4 ,cru/aceans1 bra*iopods1 & seawe$s4 ---------------------------------------- --------------------- ,organic matt] 9 =m ( graphite #be to #ej ,ar*eozoic ,ar*ean4 7black lead71 b no det]m9able fossils f\nd4 ---------------------------------------- ------------------------------ ,! l5g? ( "t repres5t$ by human hi/ory is v %ort comp>$ to ! va/ "t ( kn[n geological hi/ory4 ,! "o is measur$ by ?\s&s ( ye>s1 :ile ! o!r mu/ be measur$ by t5s ( millions ( ye>s4 ,j z we may r\ghly divide human hi/ory into c]ta9 ages accord+ to "s notable p]son1 nation1 pr9ciple1 or =ce z1 = example1 ! ,age ( ,p]icles1 ! ,roman ,p]iod1 ! ,age ( ! ,fr5* ,revolution1 or ! ,age ( ,electricity1 s geologic hi/ory may be subdivid$ accord+ to great pr$om9ant physical or organic ph5om5a1 su* z ! ,appala*ian ,m\nta9 ,revolution 7t[>d ! end ( ! ,paleozoic era71 ! ,age ( ,fi%es 7,devonian p]iod71 or ! ,age ( ,reptiles 7,mesozoic era74 ,9 ! /udy ( e>? hi/ory1 z 9 ! /udy ( human hi/ory1 x is important to di/+ui% betwe5 ev5ts & records ( ev5ts4 ,hi/orical ev5ts are cont9u\s1 b !y are by no means all record$4 ,records ( ev5ts are (t5 int]rupt$ & seem+ly %>ply sep>at$ f ea* o!r4 ,,*apt] ,,ii ,,wea!r+ ,,& ,,erosion ,all rocks at & ne> ! surface ( ! e>? crumble or decay4 ,! t]m wea!r+ includes all ! processes :]eby rocks are brok5 up1 decompos$1 or dissolv$4 ,a mass ( v h>d & seem+ly inde/ructible granite1 tak5 f a qu>ry1 w1 9 a v %ort "t1 geologically consid]$1 crumble 7,plate #a74 ,dur+ ! %ort span ( ! ord9>y human life wea!r+ effects are g5]ally ( v little consequ5ce1 b dur+ ! long ages ( geologic "t ! v>i\s processes ( wea!r+ h be5 sl[ly & ceaselessly at "w ^u ! out] cru/ ( ! e>?1 & su* trem5d\s quantities ( rock mat]ial h be5 brok5 up t ! l&s ( ! e>? h ev]y:]e be5 pr(\ndly affect$4 ,mo/ ( u h notic$ build+s & monum5ts 9 :i* ! /ones %[ m>k$ effects ( wea!r+4 ,a good case 9 po9t is ,we/m9/] ,abbey1 ,london1 9 :i* _m ( ! /ones are badly wea!r+1 "s ( ! m ornam5tal p>ts hav+ crumbl$ beyond recognition s9ce ! build+ 0 erect$ 9 ! ?irte5? c5tury4 ,9 _m c\ntries1 tomb/ones & monum5ts only "o or two c5turies old are s badly wea!r$ t ! inscriptions are sc>cely if at all legible4 ,:at are "s ( ! processes ( nature :]eby rocks are wea!r$8 ,9 cold c\ntries1 & (t5 9 m\nta9s ( g5]ally mild climate regions1 ! alt]nate freez+ & ?aw+ ( wat] is a pot5t ag5cy 9 break+ up rocks :]e ! soils are ?9 or abs5t4 ,on freez+1 wat] exp&s ab\t "o-t5? ( its volume & ex]ts ! enorm\s pressure ( ov] #b1jjj p\nds p] squ>e in*4 ,ne>ly all relatively h>d rock =mations are sep>at$ into m or less di/9ct blocks by natural cracks call$ jo9ts 7,plate #h74 ,v commonly ! rocks also conta9 m9ute crevices1 fissures1 & pores4 ,repeat$ freez+ & ?aw+ ( wat] :i* f9ds its way into su* op5+s f9ally causes ev5 ! mo/ resi/ant rocks to break up into small] & small] fragm5ts4 ,a v /rik+ example ( diff]5ce 9 climatic effect ^u a giv5 rock mass is ! obelisk 9 ,c5tral ,p>k1 ,new ,york4 ,= _m c5turies ?is fam\s monum5t /ood practically )\t *ange 9 ! dry1 fro/less climate ( ,egypt1 b v soon aft] its removal to ! moi/1 fro/y climate ( ,new ,york1 x began to crumble s rapidly t x 0 necess>y to cov] x ) a coat+ ( glaze to protect x f ! atmosph]e4 ,temp]ature *ange1 especially 9 dry regions1 is also an important ag5cy = me*anical break+ up ( rocks4 ,on high m\nta9s & on des]ts1 a daily range ( temp]ature ( f #gj degrees to #hj degrees is frequ5t4 ,due to heat absorption1 rocks 9 des]t regions1 dur+ ! day1 n uncommonly rea* temp]atures ( fully #abj degrees1 :ile dur+ ! night1 due to heat radiation1 _! temp]ature falls greatly4 ,dur+ ! heat+ ( ! out] portion ( ! rock1 ! v>i\s m9]als ea* exp& diff]5tly1 ?us sett+ up a s]ies ( /resses & /ra9s t5d+ to cause ! m9]als to pull ap>t4 ,! out] portions ( ! rocks :i* are subject$ to un/able & relatively rapid temp]ature *anges1 (t5 crack or peel (f 9 slabs or flakes1 ?is process be+ call$ exfoliation4 ,/one ,m\nta9 9 ,georgia1 & "s ( ! m\nta9s ( ! s\!rn ,si]ra ,nevada range 9 ,cali=nia1 are excell5t examples ( m\nta9s :i* are be+ r\nd$ (f by exfoliation4 ,! pr9ciple is ! same z t :i* causes ! spall+ ( /ones 9 build+s dur+ fires4 ,masses ( dbris consi/+ ( m or less angul> rock fragm5ts ( all sizes commonly occur at ! bases ( cliffs & m\nta9s4 ,!y repres5t mat]ials :i* h wea!r$ (f ! l$ges ma9ly by fro/ action & temp]ature *anges4 ,:]e electrical /orms are frequ5t1 lightn+ (t5 %att]s portions ( rock l$ges4 ,_m su* cases h come "u ! writ]'s obs]vation 9 ! ,adirondack ,m\nta9s ( ,new ,york4 ,! total effect ( lightn+ z a wea!r+ ag5cy is1 h[ev]1 relatively small4 ,ano!r m9or wea!r+ effect is ! me*anical action ( plants4 ,! pr9ciple is well illu/rat$ by ! break+ or tilt+ ( sidewalks by ! w$g+ action ( ! gr[+ roots ( trees4 ,9 _m places ! roots ( plants gr[+ 9 cracks 9 rocks1 ex]t p[]ful pressure caus+ ! rocks or blocks ( rocks to w$ge ap>t4 ,let u n[ briefly consid] "s ( ! *emical processes ( wea!r+4 ,! solv5t effect ( p]fectly pure wat] ^u rocks is v slight & sl[4 ,b su* wat] is n f\nd 9 nature because c]ta9 atmosph]ic gases1 especially oxyg5 & c>bonic acid gas1 are always pres5t 9 x1 & !y notably increase ! solv5t p[] ( ! wat]4 ,su* wat] has ! p[] to sl[ly b completely dissolve ! common rock call$ lime/one :i* consi/s ( c>bonate ( lime4 ,?is mat]ial is !n c>ri$ away by ! /reams4 ,rocks1 l c]ta9 s&/ones :i* conta9 c>bonate ( lime cem5t+ mat]ial1 are caus$ to crumble due to removal ( ! cem5t 9 solution4 ,c>bonic acid gas 9 wat] also has ! p[] to *emically alt] v>i\s m9]als 9 _m common rocks & ?us ! rocks fall ap>t & ! c>bonates :i* result f ! action usually are c>ri$ away 9 solution4 ,"o ( ! mo/ important *anges ( ?is k9d takes place :5 ! v common m9]al feldsp> is attack$ by wat] conta9+ c>bonic acid gas & ! m9]al alt]s to a soluble c>bonate1 kaol9 7or clay7 & silica4 ,! oxyg51 bo? ( ! air & t :i* is conta9$ 9 wat]1 is a v important *emical ag5t ( decomposition ( _m rocks4 ,wat] at ! surface & ! upp] "p ( ! cru/ ( ! e>? z well z moi/ure 9 ! air are also important *emical ag5ts :i* br+ ab\t rock decay4 ,we are all famili> ) ! ru/+ ( iron :i* is due to ! *emical union ( ! iron ) oxyg51 ?us =m+ an iron oxide :i* 9 turn commonly unites ) wat] f air or e>?4 ,n[1 _m rocks conta9 iron1 n z su*1 b held 9 comb9ation ) o!r sub/ances 9 ! =m ( v>i\s m9]als1 & ?is iron ( ! rocks1 :]e subject$ to ! oxyg5 & moi/ure ( air or wat]1 sl[ly unites ) ! oxyg5 & wat] to =m a hydrat$ iron oxide :i* is ess5tially iron-ru/4 ,! m9]als conta9+ consid]able iron are1 !re=e1 decompos$ & ! rocks crumble4 ,!re are v>i\s iron oxides1 usually m or less hydrat$1 rang+ 9 color f r$ ?r\gh br[n to yell[1 & ^! con/itute probably ! mo/ common & /rik+ colors ( ! rocks ( ! e>?4 ,! gorge\sly color$ ,gr& ,canyon ( ! ,yell[/one ,riv] is a v f9e example ( l>ge scale color+ due to developm5t ( mu* hydrat$ oxide ( iron dur+ ! wea!r+ ( lava rock1 ! process hav+ be5 aid$ by ! action ( heat$ und]gr\nd wat]s4 ,mo/ ( ! soils ( ! e>? are ! direct result ( wea!r+4 ,important exceptions are soils :i* h be5 transport$ by ! action ( wat]1 ice1 or w9d4 ,al?\gh ! process ( wea!r+ is v sl[ & relatively sup]ficial1 x is1 nev]!less1 true t 9 _m places1 ! products ( wea!r+ =m fa/] ?an !y c be c>ri$ away4 ,su* wea!r$ mat]ials accumulate 9 _! place ( orig9 to =m soils4 ,! upp] few hundr$ feet ( ! e>?'s cru/ is ev]y:]e m or less fractur$ & por\s & ! rocks are !re affect$ 9 v>y+ degrees by mo/ ( ! ord9>y ag5ts ( wea!r+4 ,9 su* cases1 outside ! areas :i* 7 rec5tly cov]$ by ice dur+ ! great ,ice ,age1 x is common to f9d ! loose soil grad+ d[nw>d into rott5 rock1 & ?is 9 turn into ! fre% practically unalt]$ b$rock4 ,soils ( ?is k9d are g5]ally n m ?an t5 or tw5ty feet deep1 ?\gh "u exceptional conditions1 z 9 p>ts ( ,brazil1 !y atta9 dep?s ( sev]al hundr$ feet4 ,9 ord] to make /ill cle>] "s ( ! above pr9ciples ( wea!r+ & also to give ! read] "s und]/&+ ( ! mo/ common types ( residual soils1 we %all consid] :at happ5s to a few r def9ite types ( ord9>y rocks :5 !y are subject$ to wea!r+4 ,a v simple case is t ( a s&/one1 ! m9]al gra9s 7mo/ly qu>tz7 ( :i* are held toge!r by c>bonate ( lime4 ,! lime simply dissolves & is c>ri$ away1 :ile _m ( ! m9]al gra9s may rema9 to =m a soil ( ne>ly pure s&4 ,:]e oxide ( iron =ms ! cem5t+ mat]ial1 ! rock yields less readily to wea!r+1 & ! s&y soil w be yell[i% br[n or r$ accord+ to ! climate4 ,ano!r simple case is t ( lime/one :i* :5 p]fectly pure yields no soil because x is all soluble4 ,pure lime/one is1 h[ev]1 r>e1 & ! v>i\s m9]al impurities 9 x1 be+ to a consid]able degree insoluble1 t5d to rema9 to =m a residual soil :i* may v>y f s&y to clayey1 & usually br[n or r$ due to ! sett+ free ( oxides ( iron4 ,accord+ to "o e/imate a ?ickness ( ab\t #ajj feet ( a c]ta9 fairly impure lime/one =mation 9 ,virg9ia mu/ wea!r to yield a lay] ( soil "o foot ?ick4 ,soils ( ?is k9d1 :i* are usually ri*1 are common 9 _m lime/one valleys ( ! ,appala*ian ,m\nta9s4 ,9 ! case ( %ale rock1 :i* is h>d5$ mud1 ! cem5t+ mat]ials are remov$1 "s *emical *anges 9 ! m9]als may take place1 & ! rock crumbles to a claylike soil4 ,:at happ5s to a v h>d1 resi/ant igne\s rock l granite :5 attack$ by ! wea!r8 ,su* a rock always consi/s ma9ly ( ! two v common m9]als feldsp> & qu>tz1 usually ) small] am\nts ( o!r m9]als su* z mica1 hornbl5de1 augite1 or magnetite4 ,! feldsp>1 :i* :5 fre% is h>d] ?an /eel1 sl[ly yields :5 attack$ by wat] conta9+ c>bonic acid gas & crumbles or decays to a mixture ( kaol9 7clay71 c>bonate ( pota%1 & silica 7qu>tz74 ,clay is an important con/itu5t ( mo/ good soils1 :ile ! c>bonate ( pota% is ess5tial z a food = mo/ plants4 ,due to yield+ ( ! gra9s or cry/als ( feldsp>1 ! granite falls ap>t 7see ,plate #a74 ,! gra9s ( qu>tz rema9 *emically un*ang$1 ?\gh !y may be m or less brok5 by *anges ( temp]ature1 & ! o!r m9]als1 :i* are mo/ly iron-be>+1 yield m or less to wea!r+1 result+ 9 a v>iety ( products1 among :i* are oxides ( iron4 ,a typical granite1 !re=e1 gives rise to a good heavy soil :i* is yell[1 br[n or r$ accord+ to climate4 ,su* granite soils are common 9 _m p>ts ( ! ,pi$mont ,plateau f ,m>yl& to ,georgia4 ,mo/ ( ! d>k-color$ igne\s rocks1 l ord9>y basaltic lava1 conta9 mu* feldsp>1 v>i\s iron-be>+ m9]als1 & little or no qu>tz4 ,su* rocks yield to ! wea!r l granite b1 because ( lack ( qu>tz1 ! soils are m clayey4 ,ri* soils ( ?is k9d occur 9 ! great lava fields ( ! nor?we/]n ,unit$ ,/ates & 9 ! ,hawaiian ,isl&s4 ,! importance ( ! break+ d[n ( feldsp> "u ! influ5ce ( ! wea!r1 z above describ$1 n only f ! /&po9t ( soil developm5t1 b also z reg>ds ! we>+ d[n ( ! l&s ( ! e>?1 is difficult to ov]emphasize because t m9]al is by f> ! mo/ abundant con/itu5t ( ! e>?'s cru/4 ,! t]m erosion is "o ( ! mo/ important 9 geologic sci5ce4 ,x comprises all ! processes :]eby ! l&s ( ! e>? are worn d[n4 ,x involves ! break+ up ( e>? mat]ial1 & its transportation ?r\gh ! ag5cy ( wat]1 ice1 or w9d4 ,wea!r+1 includ+ ! v>i\s subprocesses z above describ$1 is a v important process ( erosion4 ,by ?is process mu* rock mat]ial is got into condition = transportation4 ,ano!r process ( erosion1 call$ corrasion1 consi/s 9 ! rubb+ or bump+ ( rocks fragm5ts ( all sizes c>ri$ by wat]1 ice1 or w9d aga9/ ! g5]al c\ntry rock1 ?us caus+ ! latt] to be gradually worn away4 ,a f9e illu/ration ( exce$+ly rapid corrasion ( v h>d rock 0 t ( ! ,sill tunnel 9 ,au/ria1 :i* 0 pav$ ) granite blocks sev]al feet ?ick4 ,wat] c>ry+ l>ge quantities ( rock fragm5ts ov] ! pavem5t at high velocity caus$ ! granite blocks to be worn ?r\gh 9 only "o ye>4 ,ord9>ily 9 nature1 h[ev]1 ! rate ( we> is mu* sl[] ?an ?is4 ,pressure ex]t$ ^u ! c\ntry rock by any ag5cy ( transportation may cause relatively loose jo9t blocks1 into :i* mo/ rock =mations are sep>at$1 to be pu%$ away4 ,?is process1 call$ pluck+1 is especially effective 9 ! case ( fl[+ ice4 ,,*apt] ,,iii ,,/ream ,,"w ,mo/ /reams are incessantly at "w cutt+ or erod+ _! way into ! e>?'s cru/ & c>ry+ (f ! products ( wea!r+4 ,by ?is means ! g5]al level ( l&s is gradually be+ r$uc$ to ne>] & ne>] sea level4 ,base level ( erosion is rea*$ :5 any /ream has erod$ to its greate/ possible dep?1 & a :ole region is said to be base-level$ :51 by ! action ( /reams1 x has be5 r$uc$ to a practically flat condition4 ,a region ( ?is k9d is kn[n z a p5epla94 ,to "o :o has n s]i\sly consid]$ ! matt]1 ! p[] ( ev5 mod]ately swift wat] to transport rock dbris seems incr$ible4 ,a well-e/abli%$ law ( transportation by runn+ wat] is t ! transport+ p[] ( a curr5t v>ies z ! six? p[] ( its velocity4 ,= example1 a curr5t :i* is j able to move a rock fragm5t ( a giv5 size w1 :5 its velocity is m]ely d\bl$1 be able to move along a piece ( simil> rock sixty-f\r times z l>ge6 ,t ?is mu/ be ! case may be readily prov$ z foll[s3 ,a curr5t ( giv5 velocity is j able to move a block ( rock1 say1 ( "o cubic in* 9 ! =m ( a cube4 ,a cubic block sixty-f\r times z l>ge has a face ( sixte5 squ>e in*es4 ,by d\bl+ ! velocity ( ! curr5t1 !re=e1 twice z mu* wat] mu/ /rike ea* ( ! sixte5 squ>e in*es ( ! face ( ! l>g] block ) twice ! =ce1 ?us ex]t+ sixty-f\r times ! p[] aga9/ ! face ( ! l>g] block1 or en\gh to move x along4 ,?is surpris+ law acc\nts = ! fact t 9 c]ta9 floods1 l ! "o :i* ru%$ ov] ,john/[n1 ,p5nsylvania1 9 #ahhi1 locomotives1 massive iron bridges1 & great b[ld]s 7 swept along ) great velocity4 ,x is obvi\s1 !n1 t ord9>ily swift riv]s 9 "t ( flood accompli% f> m "w ( erosion 7especially transportation7 ?an dur+ _m days or ev5 "s mon?s ( l[ wat]4 ,few p h ! slighte/ idea z to ! enorm\s am\nt ( e>? mat]ial :i* ! riv]s are c>ry+ into ! sea ea* ye>4 ,! burd5 c>ri$ by ! ,mississippi ,riv] has be5 c>efully /udi$ = _m ye>s4 ,ea* ye> ?is riv] dis*>ges ab\t #djj1jjj1jjj tons ( mat]ial 9 susp5sion2 #abj1jjj1jjj tons 9 solution2 & #dj1jjj1jjj tons roll$ along ! bottom4 ,?is all repres5ts e>? mat]ial erod$ f ! dra9age bas9 ( ! riv]4 ,x is suffici5t to cov] a squ>e mile #cbe feet deep1 or if plac$ 9 ord9>y freight c>s x w\ld require a tra9 rea*+ ar\nd ! e>? sev]al times to conta9 x4 ,s9ce ! dra9age bas9 ( ! ,mississippi cov]s ab\t #a1bej1jjj squ>e miles1 x is1 !re=e1 evid5t t ?is dra9age area is be+ worn d[n at ! av]age rate ( ab\t "o foot 9 #c1hdj ye>s1 & ?is is p]haps1 a fair av]age = ! riv]s ( ! e>?4 ,! ,ganges ,riv]1 be+ unusually favorably situat$ = rapid erosion1 we>s d[n its dra9age bas9 ab\t "o foot 9 #a1gej ye>s4 ,x has be5 e/imat$ t ne>ly #hjj1jjj1jjj tons ( mat]ial are annually c>ri$ into ! sea by ! riv]s ( ! ,unit$ ,/ates4 ,accord+ to ?is ! c\ntry1 z a :ole1 is be+ cut d[n at ! rate ( ab\t "o foot 9 #i1jjj ye>s4 ,9 arriv+ at ?is figure x %\ld1 ( c\rse1 be borne 9 m9d t ! av]age level ( hundr$s ( ?\s&s ( squ>e miles ( ! we/]n ,unit$ ,/ates1 p>ticul>ly ! s-call$ ,great ,bas91 is practically n be+ r$uc$ at all because none ( ! /reams !re rea* ! sea4 ,deposition ( s$im5t is an important natural consequ5ce ( erosion4 ,! de/9ation ( mo/ /reams is ! sea1 & :]e tides are relatively slight ! s$im5ts dis*>g$ mo/ly accumulate relatively ne> ! m\?s ( ! riv]s 9 ! =m ( flat1 fan-%ap$ delta deposits4 ,"s riv]s1 l ! ,ganges1 :i* c>ry su* unusual quantities ( s$im5t1 are able to con/ruct deltas 9 spite ( consid]able tides4 ,deltas also =m 9 lakes4 ,9 mo/ cases1 h[ev]1 riv]s ent] ! sea :]e !re are consid]able tides & _! loads are m widely spread ov] ! m>g9al sea bottom4 ,b 9 _m cases "s ( ! s$im5t does n rea* ! m\? ( ! /ream4 ,x is1 in/ead1 deposit$ along its c\rse ei!r :]e ! velocity is suffici5tly *eck$1 z is ! case ov] _m flood-pla9 areas ( riv]s1 or :]e a heavily load$1 relatively swift /ream has its g5]al velocity notably dim9i%$4 ,an excell5t example ( ! latt] type ( /ream is ! ,platte ,riv]1 :i* is swift & load$ ) s$im5t 9 its desc5t f ! ,rocky ,m\nta9s1 b1 on rea*+ ! relatively m ne>ly level ,nebraska c\ntry1 x has its curr5t suffici5tly *eck$ to =ce x to deposit s$im5t & build up its *annel along _m miles ( its c\rse1 & ?is 9 spite ( ! fact t x /ill ma9ta9s a consid]able curr5t4 ,9 a m\nta9\s arid region a m or less int]mitt5t /ream at times ( flood becomes heavily load$ ) rock dbris & ru%es d[n ! m\nta9 side4 ,on rea*+ ! valley floor ! velocity is greatly *eck$ & mo/ ( ! load is deposit$ at ! base ( ! m\nta91 successive accumulations ( su* mat]ials1 call$ alluvial cones or fans1 hav+ n uncommonly built up to dep?s ( hundr$s1 or ev5 sev]al ?\s& feet4 ,illu/ration3 ,plate #a4--7;a7 ,granite ,wea!r+ to ,soil ne> ,nor?ampton1 ,mass4 ,"u ! action ( wea!r+ all ( ! once h>d1 fre%1 mass ( granite has crumbl$ to soil except ! fairly fre% r\nd$ masses :i* are residual cores ( jo9t blocks4 7,photo by ! au?or47 ,illu/ration3 ,plate #a4--7;b7 ,look+-,glass ,rock1 ,utah4 ,! rock is /ratifi$ s&/one sculptur$ ma9ly by w9d erosion1 t is1 by ! w9d driv+ p>ticles ( s& aga9/ x4 7,photo by ,cross1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #b4--;,gr& ,canyon ( ! ,yell[/one ,riv] 9 ,yell[/one ,national ,p>k4 ,! great wat]fall #cjh feet high is %[n4 ,! l>ge swift riv] has "h sunk its *annel 7by erosion7 to a maximum dep? ( #a1bjj feet dur+ v rec5t geological "t1 & ! process is /ill go+ on4 ,! wond]ful color+ is due to iron oxides set free dur+ wea!r+ ( ! lava rock4 7,photo by ,hill]s1 ,u4 ,s4 ,geological ,survey47 ,any newly =m$ l& surface1 l a rec5tly dra9$ lake b$ or "p ( ! m>g9al sea bottom :i* has be5 rais$ into l&1 has a dra9age sy/em develop$ ^u x4 ,9 ! e>ly or y\?ful /age ( su* a new l& area ly+ well above sea level1 "u ord9>y climatic conditions a few /reams only =m & ^! t5d to foll[ ! natural or initial slope ( ! l&4 ,^! /reams c>ve out n>r[1 /eep-sid$ valleys1 & all ( !m are actively engag$ 9 cutt+ d[n _! *annels1 or1 9 o!r words1 none ( !m h rea*$ base level1 & flood pla9s & me&]+ curves are !re=e lack+4 ,dur+ ?is y\?ful /age !re are no %>p dra9age divides2 gorges & wat]falls are n uncommonly pres5t2 & ! relief ( ! l& 9 g5]al is n rugg$4 ,a good example ( y\?ful topography is ! region ar\nd ,f>go1 ,nor? ,dakota1 :i* is "p ( ! b$ ( a great rec5tly dra9$ lake4 ,! ,gr& ,canyon ( ! ,yell[/one ,riv] is an excell5t illu/ration ( a y\?ful valley cut 9 a high plateau ( geologically rec5t orig94 7,plate #b47 ,z "t goes on1 a region 9 y\? gradually gives way to a region 9 maturity1 dur+ :i* /age ! maximum numb] 7usually a network7 ( /reams 9 broad] ,v-%ap$ valleys h develop$2 divisions ( dra9age are %>p2 ! maximum rugg$ness ( relief has develop$2 ! l>g] /reams only h cut d[n s ne> base level t w9d+ 7me&]+7 c\rses & flood pla9s are well develop$ along !m2 & wat]falls & gorges are r>ely pres5t4 ,an almo/ p]fect example ( a region 9 maturity is t ar\nd ,*>le/on1 ,we/ ,virg9ia4 ,! old-age /age develops next 9 ! hi/ory ( ! region1 dur+ :i* only a mod]ate numb] ( /reams rema91 mo/ ( ^! be+ at or close to base level s t sweep+ curves or me&]s 7,plate #d7 & cut-(f me&]s or ox b[s & wide flood pla9s are *>act]i/ic & common4 ,! relief is greatly subdu$ & ! t]m roll+ c\ntry might be appli$ to ! mod]ately hilly region4 ,divisions ( dra9age are1 ( c\rse1 n at all %>p & ! valleys are wide & %all[4 ,oxb[ lakes are common1 b gorges & wat]falls are abs5t4 ,a region typical ( old-age topography is t ar\nd ,caldwell1 ,kansas4 ,f9ally1 aft] ! rema9+ l[ hills h be5 cut d[n1 ! region is 9 ! condition ( a broad monoton\s pla91 practically devoid ( relief1 ov] :i* ! sluggi% /reams pursue v w9d+1 m or less %ift+ or indef9ite c\rses4 ,= ! atta9m5t ( ?is f9al /age 7call$ a p5epla97 9 ! normal cycle ( erosion a proportionately v long "t is necess>y1 because ! rate ( erosion becomes sl[] & sl[] z ! region is be+ cut d[n4 ,!n1 too1 "s *ange ( level betwe5 ! l& & ! sea is v likely to take place be=e ! p5epla9 /age is rea*$4 ,x is d\btful if any ext5sive region 0 ev] br\ght to ! condition ( a p]fect p5epla94 ,"s masses ( m resi/ant or m favorably situat$ rocks are almo/ sure to ma9ta9 at lea/ mod]ate heights above ! g5]al pla9 level4 ,geologically rec5tly uprais$1 fairly well develop$ p5epla9s are s\!rn ,new ,engl& & ! great region ( ea/]n ,canada4 ,! rem>kably ev5 sky l9es ( ^! regions m>k ! p5epla9 level be=e ! uplift took place1 & occasionally masses1 call$ monadnocks f ,m\nt ,monadnock 9 s\!rn ,new ,hamp%ire1 rise above ! g5]al level4 ,! valleys 9 su* an uplift$ p5epla9 region h be5 c>v$ out by /reams s9ce ! uplift began4 ,we h positive evid5ce t m or less well-develop$ p5epla9s ( consid]able ext5t exi/$ 9 v>i\s p>ts ( ! e>? at v>i\s times dur+ ! _m millions ( ye>s ( kn[n e>? hi/ory4 ,! normal cycle ( erosion :i*1 z outl9$ above1 t5ds t[>d ! p5epla9 condition may be int]rupt$ at any /age by o!r processes4 ,an excell5t case 9 po9t is ! upp] ,mississippi ,valley1 :i* _h rea*$ ! old-age /age1 ev5 approximat+ a p5epla91 j be=e ! great ,ice ,age4 ,!n1 dur+ ! )drawal ( ! va/ %eet ( ice f ! region t[>d ! close ( ! ,ice ,age1 ext5sive deposits 7mora9es1 etc47 ( glacial dbris 7 left irregul>ly /rewn ov] ! c\ntry1 giv+ rise to _m l[ hills1 lake bas9s1 & alt]$ dra9age l9es1 9 "s cases ) resultant gorge developm5t4 ,"s di/9ct features ( a y\?ful topography are1 !re=e1 pla/]$ ov] :at 0 o!rwise a region well along 9 old age4 ,! g5]al di/rict ar\nd ! ,dells ( ,wiscons9 ,riv] well illu/rates ?is pr9ciple4 ,*anges 9 level betwe5 l& & sea :i* take place dur+ ! erosion ( a region may also di/urb ! normal cycle ( erosion4 ,= example1 a region 9 old age may be consid]ably uprais$ s t ! /reams h _! velocities notably increas$4 ,su* a region is said to be rejuv5at$ & ! /reams1 :i* are reviv$ 9 activity1 beg9 to cut y\?ful valleys 9 ! bottom ( ! old ones &1 aft] a "t1 ! g5]al surface ( ! region is subject$ to vigor\s erosion & a new cycle ( erosion w be c>ri$ out unless int]f]$ ) 9 "s way1 z by relative *ange ( level betwe5 ! l& & ! sea4 ,9 ?is connection ! hi/ory ( ! topography 9 ! g5]al vic9ity ( ,h>risburg1 ,p5nsylvania1 may be ( int]e/ by way ( illu/ration ( ! pr9ciple j describ$4 ,! long1 n>r[1 p>allel ,appala*ian ,m\nta9 ridges !re rise to ab\t ! same level1 caus+ a rem>kably ev5 sky l9e z view$ f "o ( ! summits4 ,?is ev5 sky l9e m>ks approximately ! surface ( :at 0 a p5epla9 late 9 ! ,mesozoic era4 ,e>ly 9 ! succe$+ ,c5ozoic era1 ! broad p5epla9 0 notably uprais$ to ne>ly ! pres5t altitudes ( ! ridge tops4 ,! reviv$ ,susquehanna ,riv] left ! old c\rse :i* x _h on ! p5epla9 surface1 & began to c>ve out its pres5t valley1 :ile tribut>ies 7subsequ5t /reams7 to x develop$ along belts ( weak] rock & ?us !y =m$ ! pres5t p>allel valleys sep>at$ by belts ( m resi/ant rocks :i* /& out z ridges4 ,9 ?is way1 ! mature /age ( topography 0 rea*$4 ,v rec5tly1 geologically1 ! region has be5 rejuv5at$ en\gh to cause ! l>g] /reams to appreciably s9k _! *annels bel[ ! g5]al valley floors4 ,! read] w f9d a g5]al discussion ( movem5ts ( ! e>?'s cru/ 9 a succe$+ *apt]4 ,illu/ration3 ,fig4 #a4--,! subm]g$ ,hudson ,riv] *annel is cle>ly %[n by ! cont\r l9es on ! sea floor4 ,figures indicate dep? ( wat] 9 fa?oms4 ,geologically rec5t s9k+ ( ! l& has caus$ ! dr[n+ ( ! riv] valley4 7,coa/ & ,geodetic ,survey74 ,if1 = example1 a region along ! seabo>d has rea*$ ! mature /age ( erosion1 & ! l& notably subsides relative to sea level1 ! tidewat] w ent] ! l[] valleys to =m e/u>ies & ! valleys are said to be dr[n$4 ,! l>ge /reams1 or at lea/ _! l[] c\rses1 are ?us oblit]at$ & also ! g5]al erosion ( ! region is di/9ctly dim9i%$4 ,! rec5tly sunk5 coa/ ( ,ma9e well illu/rates ! idea ( dr[n$ valleys4 ,! dr[n$ valley ( ! l[] ,hudson ,riv] is ano!r f9e example4 ,illu/ration3 ,fig4 #b4--,sket* maps %[+ h[ ! ,%5&oah ,riv] captur$ ! upp] wat]s ( ,beav]dam ,creek 9 ,virg9ia4 ,! ab&on$ valley ( ! creek across ,blue ,ridge is n[ call$ a w9d gap4 7,aft] ,b4 ,willis47 ,:at is t]m$ /ream piracy is ( special int]e/ 9 connection ) /ream "w4 ,by ?is is meant ! /eal+ ( "o /ream or "p ( a /ream by ano!r4 ,we %all "h expla9 only "o ( ! v>i\s ways by :i* /ream capture may be effect$4 ,"o ( two fairly active /reams1 fl[+ r\ghly p>allel to ea* o!r1 is m favorably situat$ & has cut its *annel deep]4 ,its tribut>ies are1 !re=e1 m favorable to ext5sion ( headwat]s &1 9 "t1 "o ( its tribut>ies eats back f> en\gh to tap a bran* ( ! less favorably situat$ /ream s t ! wat]s ( ?is bran* are div]t$ into ! m favorably situat$ /ream4 ,! ,%5&oah ,riv] ( ,virg9ia has be5 su* a pirate4 ,?is riv] develop$ z a tribut>y ( ! ,potomac4 ,by headw>d ext5sion t[>d ! s\?1 ! ,%5&oah f9ally tapp$ & div]t$ ! upp] wat]s ( ! small]1 less favorably situat$ ,beav]dam ,creek4 ,! not* or s-call$ w9d gap ?r\gh :i* ! upp] wat]s ( ,beav]dam ,creek =m]ly fl[$ across ! ,blue ,ridge is /ill pla9ly visible4 ,su* ab&on$ wat] gaps1 kn[n z w9d gaps1 are common 9 ! c5tral ,appala*ian ,m\nta9 region4 ,a rem>kable type ( riv] is "o :i* has be5 able to ma9ta9 its c\rse ?r\gh a b>ri]1 ev5 a m\nta9 range1 :i* has be5 built across x4 ,?us1 ! ,columbia ,riv]1 aft] fl[+ _m miles across ! great lava plateau1 has ma9ta9$ its c\rse "r across ! gr[+ ,cascade ,range by cutt+ a deep canyon :ile ! m\nta9 uplift has be5 9 progress4 ,9 a simil> mann] ! ,ogd5 ,riv] ( ,utah has kept its we/w>d c\rse by cutt+ a deep canyon into ! ,wasat* ,range :i* has geologically rec5tly1 ?\gh sl[ly1 ris5 across its pa?4 ,9 no o!r way c we possibly expla9 ! fact t su* a riv]1 ris+ on "o side ( a high m\nta9 range1 cuts "r across x4 ,a feature ( m9or ?\gh consid]able popul> int]e/ is ! developm5t ( po?oles by /ream action4 ,:]e eddies occur1 9 r active /reams1 rock fragm5ts ( v>y+ sizes may be :irl$ ar\nd 9 su* mann] z to corrode or gr9d ! b$rock1 result+ 9 ! developm5t ( cyl9d]-%ap$ po?oles4 ,su* holes v>y 9 diamet] up to fifty feet or m 9 v exceptional cases4 ,9 ! production ( l>ge po?oles _m rock fragm5ts are worn away & new ones suppli$ to cont9ue ! "w4 ,locally1 "s /ream b$s are honeycomb$ ) po?oles4 ,illu/ration3 ,fig4 #c4--;,gr& ,canyon1 ,arizona4 7,f ,d>ton's ,/ory ( ! ,gr& ,canyon47 ,/rik+ly n>r[ & deep valleys1 call$ gorges & canyons1 are r exceptional features ( /ream action4 ,mo/ wond]ful ( all features ( ?is k9d is ! ,gr& ,canyon ( ! ,colorado ,riv] 9 ,arizona4 ,9 fact1 ?is canyon takes high rank among ! mo/ rem>kable works ( nature4 ,! canyon is ov] #bjj miles long1 f #d1jjj to #f1jjj feet deep1 & f #h to #ae miles wide4 ,contr>y to popul> op9ion1 ?is mighty canyon is n a result ( "s viol5t process1 su* z volcanic action1 or ! sudd5 s9k+ ( "p ( ! e>?'s cru/4 ,nor is x ! result ( ! sc\r+ action ( a great glaci]4 ,x is simply a result ( ! op]ation ( ! ord9>y processes ( erosion :]e ! conditions h be5 exceptionally favorable4 ,"s ( ! favorable conditions h be51 & are1 a l>ge volume ( v swift wat] 7,colorado ,riv]7 cont9ually *>g$ ) an abundance ( rock fragm5ts = ! "w ( corrasion1 & a great ?ickness ( rock :i* ! riv] mu/ cut ?r\gh be=e rea*+ base-level4 ,aridity ( climate also t5ds to pres]ve ! canyon =m4 ,! :ole "w has be5 accompli%$ 9 v late geological "t1 & ! trem5d\s volume ( rock :i* has be5 wea!r$ & erod$ to produce ! canyon has all be5 c>ri$ away by ! ,colorado ,riv] & accumulat$ 9 ! great delta deposit ne> :]e ! riv] empties into ! ,gulf ( ,cali=nia4 ,ev5 n[ ! canyon is gr[+ deep] & wid] because ! v active ,colorado ,riv] is /ill f #b1jjj to #c1jjj feet above sea level4 ,/&+ on ! s\!rn rim ne> ,gr& ,canyon /ation at an altitude ( ne>ly #g1jjj feet1 & look+ d[n into ! canyon1 "o beholds a va/ maze ( side canyons1 high1 v]tical rock walls :i* foll[ v s9u\s c\rses1 giv+ rise to a /eplike topography1 & c\ntless rock p9nacles1 t[]s1 & mesas (t5 ( m\nta9-l proportions4 ,! side canyons are ! result ( erosion by tribut>ies to ! ma9 riv] :i* h gradually develop$ & work$ headw>d z ! ma9 riv] has cut d[n4 ,! m\nta9-l sculptur$ =ms :i* rise out ( ! canyon are erosion remnants1 or1 9 o!r words1 masses ( rock :i* 7 m favorably situat$ aga9/ erosion by ei!r ! ma9 riv] or any ( its tribut>ies4 ,all ( ! rocks ( ! broad]1 ma9 portions ( ! canyon are /rata ( ,paleozoic age1 arrang$ z a va/ pile ( almo/ horizontal lay]s1 includ+ s&/one1 lime/one1 & %ale4 ,"s ( ^! lay]s1 be+ di/9ctly m resi/ant ?an o!rs1 /& out 9 ! canyon wall 9 ! =m ( conspicu\s cliffs1 9 "s cases hundr$s ( feet high4 ,! v /rik+ color b&s 7mo/ly light gray1 r$1 & gre5i% gray71 :i* may be trac$ 9 & out along ! canyon sides1 repres5t ! outcropp+ edges ( v>i\sly color$ rock lay]s4 ,f> d[n 9 ! canyon lies ! /eep-sid$1 ,v-%ap$ inn] gorge1 or canyon :i* is fully #a1jjj feet deep4 ,! rocks are !re n ord9>y /rata1 b r metamorphic & igne\s rocks1 mo/ly d>k gray1 n 9 lay]s1 & ab\t uni=mly resi/ant to erosion4 ,!re is reason to believe t ?is inn] gorge has develop$ ma9ly s9ce a di/9ct r5ew$ uplift 7rejuv5ation7 ( ! ,colorado ,plateau aft] ! riv] began its canyon cutt+4 ,! n>r[1 /eep-sid$ inn] gorge may ?us be readily acc\nt$ = & ! g5]al lack ( /eplike =ms on its sides is due to ess5tial uni=mity ( ! rock mat]ial z reg>ds resi/ance to erosion4 ,illu/ration3 ,fig4 #d4--,pr(ile & /ructure section across ! l9e ,a-,a 9 ,fig4 #c4 ,l5g? ( section #aj miles1 v]tical scale n exagg]at$4 ,! ma9 relief features1 & ! relations ( ! rocks bel[ ! surface are %[n4 ,! granite & gneiss are ( ,ar*eozoic age1 & ! ov]ly+ ne>ly horizontal /rata are ( ,paleozoic age4 7,aft] ,d>ton1 ,u4 ,s4 ,geological ,survey47 ,! wond]ful ,k+'s ,riv] ,canyon ( ! s\!rn ,si]ras 9 ,cali=nia is rem>kable = its comb9$ n>r[ness & dep?4 ,x is a /eep ,v-%ap$ canyon ^: maximum dep? is #f1ijj feet1 c>v$ out 9 mo/ly solid granite by ! action ( wea!r+ & runn+ wat]4 ,"s idea ( ! va/ antiquity ( ! e>? may be glean$ f ! fact t ?is trem5d\sly deep canyon has be5 produc$ by erosion 9 "o ( ! mo/ resi/ant ( all kn[n rocks 9 v late geologic "t6 ,conditions favorable = cutt+ ?is canyon h be5 volume & swiftness ( wat] & a lib]al supply ( gr9d+ tools4 ,among ! _m o!r great canyons ( ! we/]n ,unit$ ,/ates brief m5tion may be made ( ! ,gr& ,canyon ( ! ,yell[/one ,riv] 9 ! ,national ,p>k4 ,! plateau into :i* ! riv] has cut its /eep-sid$1 n>r[1 ,v-%ap$ canyon1 ) a maximum dep? ( #a1bjj feet1 has be5 geologically rec5tly built up by outp\r+s ( va/ %eets ( lava4 ,! l>ge volume ( v swift wat]1 aid$ by decomposition & weak5+ ( ! ord9>ily v h>d rock by ! action ( ! hot spr+s1 has be5 able to c>ve out ?is deep canyon practically )9 ! la/ p]iod ( e>? hi/ory4 ,! deep5+ process is /ill vigor\sly 9 progress4 ,! wond]ful color+ ( ! rock1 mo/ly 9 tones ( yell[ & br[n1 is due to ! hydrat$ iron oxides develop$ dur+ ! decay ( ! iron-be>+ m9]als ( ! lava1 ! *emical action hav+ be5 greatly aid$ by ! action ( ! hot wat]s4 7,see ,plate #b47 ,9 reg>d to its orig91 ! m>vel\s ,yosemite ,valley1 or canyon1 falls 9 a some:at diff]5t category1 & x is discuss$ beyond 9 connection ) ! "w ( ice4 ,suffice x to say "h t runn+ wat] has be5 a v important factor 9 its orig94 ,9 ,new ,york & ,new ,engl& !re are _m gorges :i* h develop$ by ! action ( runn+ wat] s9ce ! ,great ,ice ,age4 ,fam\s among ^! are ,ausable ,*asm & ,watk9s ,gl5 ( ,new ,york1 & ! ,flume 9 ! ,:ite ,m\nta9s ( ,new ,hamp%ire4 ,illu/ration3 ,fig4 #e4--,sket* map %[+ ! retreat ( ! cre/ ( ,niag>a ,falls f #ahdb to #aije1 bas$ ^u actual surveys4 ,! retreat ( ! inn] "p ( ! ,horse%oe ,fall 0 m ?an #cjj feet4 7,modifi$ by ! au?or aft] ,gilb]t1 ,u4 ,s4 ,geological ,survey47 ,be=e leav+ our discussion ( ! "w ( runn+ wat]1 we %\ld briefly consid] wat]falls4 ,true wat]falls orig9ate 9 a numb] ( ways4 ,mo/ common ( all is :at may be t]m$ ! ,niag>a type ( wat]fall4 ,niag>a ,falls m]it m ?an pass+ m5tion n only because ( _! sc5ic gr&eur1 b also because ( ! unusual numb] ( geologic pr9ciples :i* _! orig9 & hi/ory s cle>ly illu/rate4 ,niag>a ,falls are divid$ into two ma9 portions1 ! ,canadian1 or s-call$ ,horse%oe ,fall1 & ! ,am]ican ,fall1 sep>at$ by a l>ge isl&4 ,! cre/ ( ! ,am]ican ,fall is ab\t #a1jjj feet long & ne>ly /raight1 :ile ! cre/ ( ! ,canadian ,fall is notably curv$ inw>d up/ream1 & x is ab\t #c1jjj feet long4 ,! height ( ! ,falls is #afg feet4 ,d[n/ream f ! ,falls !re is a v /eep-sid$ gorge ab\t #bjj feet deep & sev5 miles long4 ,! expos$ rocks ( ! region are ne>ly horizontal lay]s ( lime/one und]la9 ) %ales4 ,relatively m resi/ant lime/one =ms ! cre/ ( ! falls1 & directly und]nea? are ! mu* weak] %ales4 ,h]e9 lies ! pr9ciple ( ?is type ( wat]fall because1 due to wea!r+ & ! swirl+ action ( ! wat]1 ! weak] und]ly+ rocks erode fa/]1 ?us caus+ ! ov]ly+ rock to ov]hang s t f "t to "t blocks ( x already m or less sep>at$ by cracks 7jo9ts71 fall d[n & are mo/ly c>ri$ away 9 ! swift curr5t4 ,?us ! wat]fall ma9ta9s itself :ile x /eadily retreats up/ream4 ,c>eful e/imates bas$ ^u obs]vations made betwe5 #ahbg & #aije %[ t ! ,canadian ,fall retreat$ at ! rate ( f ?ree to five feet p] ye>1 :ile ! ,am]ican ,fall retreat$ dur+ ! same "t at ! rate ( only sev]al in*es p] ye>4 ,x has be5 well e/abli%$ t ,niag>a ,falls came into exi/5ce soon aft] ! ice ( ! great ,ice ,age _h retreat$ f ! di/rict4 ,! falls />t$ by plung+ ov] a lime/one esc>pm5t1 situat$ at :at is n[ ! m\? ( ! gorge sev5 miles d[n/ream f ! pres5t falls4 ,if we consid] ! rate ( recession ( ! falls to h be5 always five feet p] ye>1 ! l5g? ( "t requir$ to cut ! gorge w\ld be some?+ ov] #g1jjj ye>s4 ,b ! problem is n s simple1 because we "k t1 at ! "t (1 or %ortly aft]1 ! beg9n+ ( ! falls1 ! upp] ,great ,lakes dra9$ f>!r nor? & n ov] ! falls2 & t ?is cont9u$ = a consid]able1 ?\gh unkn[n1 l5g? ( "t4 ,dur+ ?is int]val ! volume ( wat] 9 ,niag>a ,riv] 0 notably dim9i%$1 & h5ce ! recession ( ! falls mu/ h be5 sl[]4 ,on ! o!r h&1 judg+ by ! wid? ( ! gorge1 ! l5g? ( ! cre/ ( ! falls has g5]ally be5 consid]ably less ?an at pres5t1 :i* 9 turn means great] conc5tration ( wat] ov] ! cre/ & m rapid we>4 ,v>i\s factors consid]$1 ! be/ e/imates = ! age ( ! falls v>y f #g1jjj to #ej1jjj ye>s1 an av]age be+ ab\t #be1jjj ye>s4 ,al?\gh ?is figure is n precise1 x is1 nev]!less1 ( consid]able geologic int]e/ because x %[s t ! age ( ,niag>a ,falls 7& gorge7 is to be reckon$ 9 "s t5s ( ?\s&s ( ye>s1 r ?an hundr$s ( ?\s&s or millions ( ye>s4 ,al?\gh wat]falls ( ! ,niag>a type are ! mo/ common ( all1 x is by no means necess>y t ! p>ticul> rocks %\ld be lime/one & %ale4 ,ano!r common k9d ( wat]fall may be t]m$ ! ,yosemite type1 s nam$ f ! high falls 9 ! ,yosemite ,valley ( ,cali=nia4 ,at ! great falls ( ! ,yosemite1 ! rock is a homog5e\s granite & ! und]m9+ process does n op]ate4 ,yosemite ,creek fir/ plunges v]tically ov] a granite cliff = #a1dcj feet to =m ! ,upp] ,falls1 :i* mu/ rank among ! v highe/ ( all true wat] falls4 ,! wat] !n desc5ds ab\t #hjj feet by cascad+ ?r\gh a n>r[ gorge1 aft] :i* x makes a f9al v]tical plunge ( ov] #cjj feet4 ,a brief hi/ory ( ! falls is ab\t z foll[s4 ,a great /eep-sid$ ,v-%ap$ canyon sev]al ?\s& feet deep _h be5 c>v$ out by ! action ( ! ,m]c$ ,riv] :i* n[ fl[s ?r\gh ! valley4 ,!n1 dur+ ! ,ice ,age1 a mighty glaci] pl[$ ?r\gh ! canyon1 fill+ x to ov]fl[+4 ,! granite ( ?is di/rict hav+ be5 unusually highly fractur$ by great v]tical jo9t cracks 0 relatively easy prey = ice erosion4 ,due to its great weight1 ! erosive p[] ( ! ice 0 mo/ pot5t t[>d ! bottom1 successive jo9t blocks 7 remov$1 & ! valley 0 ?us wid5$ & ! sides /eep5$ or ev5 commonly made practically v]tical4 7,see ,plate #f47 ,aft] ! melt+ ( ! ice1 c]ta9 ( ! /reams1 l ,yosemite ,creek & ,bridal ,veil ,creek1 7 =c$ to ent] ! valley by plung+ ov] great p]p5dicul>1 granite cliffs :i* are 9 reality jo9t faces4 ,?is type ( wat]fall does n retreat1 b x con/antly dim9i%es 9 height by cutt+ into ! cre/4 ,a numb] ( o!r high falls ( ?is k9d occur 9 ! ,yosemite region1 & also 9 o!r m\nta9 valleys :i* =m]ly conta9$ glaci]s1 z 9 ! ,canadian ,rockies1 ! ,alps1 & ,norway1 ! rocks 9 ^! regions be+ ( v>i\s k9ds4 ,9 ! case ( ! ,yell[/one type ( wat]fall a diff]5t pr9ciple is involv$1 namely1 a di/9ctly h>d] or m resi/ant mass ( rock :i* ext5ds v]tically across ! *annel ( ! /ream4 ,at ! ,great ,falls ( ! ,yell[/one a mass ( relatively fre%1 h>d lava lies a?w>t ! c\rse ( ! riv]1 :ile j bel[ x ! lava has be5 mu* weak5$ by decomposition4 ,! h>d] rock !re=e acts z a b>ri]1 :ile1 9 ! c\rse ( "t1 ! weak rock on ! d[n/ream side has be5 worn away until a wat]fall #cjh feet high has develop$4 ,?is wat]fall does n retreat v appreciably1 b x is probably increas+ 9 height1 due bo? to ! sc\r+ action ( ! wat] at ! base ( ! fall & ! unusual cle>ness ( ! riv] wat] "h1 ?us caus+ little we> at ! cre/4 ,x %\ld be not$1 9 ?is connection1 t ! *annel j on ! up/ream side ( ! b>ri] _c be cut d[n fa/] ?an ! top ( ! b>ri] itself4 ,! fam\s ,victoria ,falls ( ! ,zambezi ,riv] 9 ,s\? ,africa1 repres5ts a relatively uncommon type ( wat]fall4 ,consid]+ height ( ! fall1 l5g? ( cre/1 & volume ( wat]1 ?is is p]haps ! greate/ wat]fall 9 ! _w4 ,! ,zambezi ,riv]1 a mile wide1 plunges ov] #djj feet v]tically into a *asm only a few hundr$ feet wide & at "r angles to ! ma9 c\rse ( ! /ream4 ,! g5]al c\ntry rock is h>d lava1 b locally a n>r[ belt ( ! rock has be5 highly fractur$ v]tically1 due to e>? movem5ts or fault+ 7see explanation beyond7 & !re=e weak5$ & m subject to wea!r+ ?an ! g5]al body ( ! lava rock4 ,?is belt ( weak5$ rock has be5 easy prey = erosion by ! ,zambezi ,riv] & ! *asm has !re develop$4 ,9 fact ! *asm is /ill be+ increas$ 9 dep?4 ,leav+ ! *asm t[>d "o end1 ! riv] fl[s ?r\gh a n>r[ zig-zag gorge ^: position has be5 det]m9$ by big jo9t cracks4 ,! mile-wide cre/ ( ! falls is int]rupt$ by a good _m l$ges & ev5 small isl&s4 ,! ?und]+ noise ( ?is great wat]fall is mo/ impressive1 b a good complete view is impossible because mo/ ( ! *asm is con/antly fill$ ) d5se spray4 ,/ill ano!r type ( wat]fall develops by ! removal ( jo9t blocks by ! action ( runn+ wat]4 ,falls ( ?is type are fairly common ?\gh !y seldom atta9 really great heights4 ,:]e ! rock 9 ! b$ ( a /ream is trav]s$ by well-develop$ v]tical jo9t cracks1 slabs ( rock cleav$ by ! jo9ts may fall away due to wea!r+ or !y may be pu%$ away by pressure ( ! wat]4 ,su* a fall retreats up/ream by removal ( jo9t blocks ev5 9 comp>atively homog5e\s rocks4 ,taughannock ,falls1 #bae feet high1 9 s\!rn c5tral ,new ,york1 has develop$ by ?is mann] 9 a %aly s&/one4 ,! sev]al falls 7"o #ej feet high7 9 ! fam\s gorge at ,tr5ton ,falls1 9 c5tral ,new ,york1 h develop$ 9 ?is way 9 lime/one4 ,,*apt] ,,iv ,,! ,,sea ,,& ,,its ,,"w ,x is well kn[n t ! wat]s ( ! sea cov] ne>ly ?ree-f\r?s ( ! surface ( ! e>?4 ,we ?9k ( ! ,unit$ ,/ates z be+ a l>ge piece ( l& ( ov] ?ree million squ>e miles--b ! sea is ab\t =ty-five times z l>ge1 t is1 x cov]s approximately #adj1jjj1jjj squ>e miles4 ,x is a rem>kable fact t ! av]age dep? ( ! great oceans ( ! e>? is ne>ly two & "o-half miles4 ,if ! sea 7 univ]sally pres5t ev]y:]e ) ! same dep?1 x w\ld be almo/ two miles deep4 ,yet ?is va/ body ( wat] is an extremely ?9 lay] :5 comp>$ ) ! e>?'s diamet] ( #h1jjj miles4 ,! ,pacific is ! deepe/ ( ! oceans ) an av]age dep? ( ab\t two & ?ree-f\r?s miles4 ,! deepe/ ocean wat] ev] s\nd$ is #cb1aad feet 7ov] six miles71 n f> f ! ,philipp9e ,isl&s4 ,?is is kn[n z ! ,planet ,deep1 & 0 discov]$ 9 #aiab4 ,second deepe/ is #cj1icj feet ne> ! isl& ( ,guam4 ,9 ! ,pacific ,ocean !re are five places :]e ! wat] is ov] five miles deep & elev5 places 7 x is ov] f\r miles deep4 ,! deepe/ s\nd+ ev] made 9 ! ,atlantic ,ocean 0 #bg1igb feet1 n f> f ,porto ,rico4 ,_m sub/ances are kn[n to be 9 solution 9 sea wat]1 b 9 spite ( ?is ! composition is rem>kably uni=m4 ,! mo/ abundant sub/ance by f> 9 solution is common salt4 ,9 e #ajj p\nds ( sea wat]1 !re are #c4e p\nds ( m9]al matt] ( v>i\s k9ds dissolv$4 ,ne>ly #gh p] c5t ( ! dissolv$ matt] is common salt4 ,! pr9cipal o!r con/itu5ts 9 solution are *loride & sulphate ( magnesia1 & ! sulphates ( lime & pota%4 ,all o!r dissolv$ m9]al sub/ances toge!r make up less ?an "o p] c5t ( ! total4 ,x has be5 e/imat$ t if all ! dissolv$ m9]al matt] %\ld be br\ght toge!r1 x w\ld =m a lay] #age feet ?ick ov] ! :ole sea bottom4 ,! salts ( ! sea h be5 mo/ly suppli$ by ! riv]s1 :i* 9 turn h d]iv$ !m f ! dis9tegration & *emical decay ( ! rocks4 ,if we make a g5]al comp>ison ) ! surface ( ! l&1 ! floor ( ! ocean is a va/ monoton\s pla94 ,none ( ! sea bottom comp>es ) ! rugg$ness ( m\nta9s1 & ev5 ! m level portions ( l& surface %[ _m %>p m9or irregul>ities su* z /ream tr5*es4 ,b ! sea bottom is *>act]iz$ by its smoo?ness ( surface4 ,!re are "u ! sea1 h[ev]1 m\nta9-l ridges1 plateaus1 subm>9e volcanoes & valleys kn[n z deeps4 ,b ^! r>ely %[ rugg$ness ( relief l simil> features on l&4 ,"o ( ! mo/ rem>kable relief features ( ! ocean bottom is ! s-call$ cont95tal %elf4 ,?is is a relatively n>r[ plat=m cov]$ by %all[ wat] bord]+ ne>ly all ! l&s ( ! e>?4 ,seaw>d1 ! dep? ( wat] is greate/1 & x is seldom ov] #fjj or #hjj feet4 ,! cont95tal %elves ( ! _w cov] ab\t #aj1jjj1jjj squ>e miles or ab\t "o-f\rte5? ( ! area ( ! sea4 ,view$ 9 a broad way1 !re are two great classes ( m>9e deposits2 fir/1 ^? laid d[n comp>atively ne> ! bord]s ( ! l&1 t is1 on ! cont95tal %elf & cont95tal slope1 & second1 ! abysmal deposits laid d[n on ! bottom ( ! deep ocean4 ,^? f\nd along & ne> ! cont95tal bord]s are l>gely l&-d]iv$ mat]ials1 t is to say1 !y are mo/ly s$im5ts c>ri$ f ! l& into ! sea by riv]s1 & to a less] ext5t rock mat]ial brok5 up by waves along _m %ores4 ,practically all su* l&-d]iv$ mat]ial is deposit$ )9 #ajj to #cjj miles ( ! %ores4 ,! cont95tal bord] deposits are extremely v>iable4 ,ne> %ore !y are *iefly gravel & s&s1 :ile f>!r out !y become gradually f9]1 & on ! cont95tal slope only v f9e muds are deposit$4 ,^! deposits usually conta9 m or less organic mat]ials & %ells or skeletons ( organisms4 ,9 "s cases ! %ells or skeletons ( organisms pr$om9ate or ev5 exi/ to ! exclusion ( ne>ly all o!r mat]ial1 z is true ( ! coral deposits or reefs :i* =m only 9 %all[ wat]4 ,deposits l ^? j describ$ z accumulat+ on ! bottom ( ! %all[ sea1 comp>atively ne> ! l&s1 are ( great significance to ! geologi/ because j su* m>9e deposits n[ consolidat$ into s&/one1 conglom]ate1 %ale1 & lime/one1 are s widely expos$ ov] ! v>i\s cont95ts4 ,a k ( ! conditions "u :i* %all[ sea deposits are n[ =m+1 is1 !re=e1 ( great value 9 int]pret+ ev5ts ( e>? hi/ory z !y are record$ 9 simil> rocks :i* h be5 accumulat+ ?r\gh millions ( ye>s ( "t4 ,"o specific in/ance w make ?is matt] cle>]4 ,us+ ! me?od outl9$ 9 ,*apt] ,i = ! det]m9ation ( e>? *ronology1 & our k ( pres5t conditions "u :i* %all[ sea deposits are =m$1 x has be5 well e/abli%$ t a %all[ sea spread ov] fully f\r-fif?s ( ! area ( ,nor? ,am]ica dur+ ! middle ,ordovician p]iod ( ! e>ly ,paleozoic era4 ,beyond ?is ma9 conclusion1 a c>eful /udy ( ^! rocks has reveal$ _m important facts reg>d+ ! physical geography1 life1 & climate ( t "t4 ,! importance ( ?is :ole matt] is /ill fur!r emphasiz$ by ! /atem5t t five-six?s ( ! expos$ rocks ( ! e>? are /rata--mo/ly ( %all[ sea orig94 ,! deposits on ! deep sea bottom are v l>gely ei!r organic or ! %ells & skeletons ( organisms :i* h fall5 to ! bottom f ne> ! surface z already expla9$4 ,mo/ common ( ^! are ! deep sea oozes :i* are made up ( ! rema9s & %ells ( t9y organisms call$ =am9if]s4 ,^! oozes cov] ab\t #ej million squ>e miles ( ! sea bottom d[n to dep?s ( f two to ?ree miles4 ,at dep?s great] ?an f two to ?ree miles1 a peculi> r$ clay is ! prevail+ deposit4 ,?is is mo/ ext5sive ( all1 cov]+ an area ( #ee million squ>e miles1 or ne>ly ! total area ( l&s ( ! e>?4 ,"s rema9s ( organisms are mix$ ) ?is clay1 b s9ce mo/ ( ! %ells are ( c>bonate ( lime & v ?91 !y are dissolv$ )\t rea*+ ! bottom 9 ! deep sea wat] :i* is "u great pressure & ri* 9 c>bonic acid gas4 ,! deep sea deposits1 bo? oozes & r$ clay1 d1 h[ev]1 conta9 "s l&-d]iv$ & o!r mat]ials4 ,?us (f ! we/ coa/ ( ,africa "s du/ c>ri$ by ! prevail+ w9ds f ! ,sah>a ,des]t1 is kn[n to fall 9 ! deep sea sev]al hundr$ miles f %ore4 ,volcanic du/ is c>ri$ = _m miles & deposit$ 9 ! deep sea--p>ticul>ly 9 ! ,s\? ,pacific ,ocean4 ,bits ( por\s volcanic rock call$ pumice sometimes float long di/ances out ov] ! deep sea1 be=e becom+ wat] soak$4 ,iceb]gs (t5 drift f> out f ! pol> regions ov] ! deep sea1 & on melt+ ! rock dbris :i* !y c>ry is dropp$ to ! sea bottom4 ,also1 p>ticles ( iron & du/ f meteorites 7%oot+ />s7 h be5 dr$g$ f ! deep sea4 ,"o important geological significance ( ! deep sea deposits is ! pro( :i* !y furni% t1 f at lea/ z f> back z ! beg9n+ ( ! ,paleozoic era1 fully tw5ty-five million ye>s ago1 to ! pres5t "t1 ! two great deep ocean bas9s--! ,atlantic & ! ,pacific--h ma9ta9$ ess5tially ! same positions on ! e>?4 ,?is is prov$ by ! fact t n[h]e1 on any cont95t among ! rocks ( all ages1 z old at lea/ z ! e>ly ,paleozoic1 d we f9d any really typical deep-sea deposits4 ,!re is !n no evid5ce t a deep sea ev] spread ov] any consid]able "p ( any cont95t1 & ?is 9 spite ( ! fact t m>9e deposits ( %all[ wat] orig9 furni% abundant evid5ce ( =m] sea ext5sions4 ,! %all[ seas h at v>i\s times spread ov] l>ge portions ( ! cont95ts4 ,on _m rocky coa/s ! waves are incessantly p\nd+ & we>+ away ! rocks4 ,9 su* places ! sea1 l a mighty horizontal saw1 is cutt+ into ! bord]s ( ! l&s4 ,! f9] mat]ials produc$ by ! gr9d+ up ( ! rocks are c>ri$ seaw>d by ! und]t[4 ,b1 if ! l& rema9s /ation>y ) ref]5ce to ! sea1 ?is l&w>d cutt+ by ! waves rea*es a limit4 ,s9ce ev5 big waves h v little effect 9 wat] #ajj or #bjj feet deep1 a %elf is cut by ! waves & ?is %elf1 n _m miles wide1 is cov]$ by %all[ wat]4 ,! f9] gr\nd-up rock mat]ials c>ri$ out by ! und]t[ are dump$ j beyond ! edge ( ! %elf :i* is ?us built out seaw>d z a t]race4 ,9 travel+ ov] ?is %elf & t]race1 ! waves1 due to friction1 lose _! p[]4 ,) gradually s9k+ l&1 a mu* wid] %elf may be cut1 because ! p[] ( ! waves is !n all[$ to cont9ue4 ,x might be ( int]e/ to cite a few cases ( relatively rapid coa/ de/ruction by ! waves :i* h come "u human obs]vation4 ,a rem>kable example is ! isl& ( ,heligol& on :i* is 7or 07 locat$ ! p[]ful ,g]man =t :i* gu>ds ! entrance to ! ,kiel ,canal4 ,9 ! ye> #hjj ,a4 ,d4 ?is isl& _h #abj miles ( %ore l9e2 9 #acjj x _h #de miles ( %ore2 9 #afdi only #h miles2 & 9 #aijj b #c miles ( %ore l9e rema9$4 ,9 s\!a/]n ,engl& :ole f>ms & villages h be5 wa%$ away 9 ! la/ few c5turies1 ! sea cliffs retreat+ f #g to #ae feet a ye>4 ,a *ur* locat$ a mile f ! sea %ore ne> ! m\? ( ! ,?ames riv]1 9 ! sixte5? c5tury1 n[ /&s on a cliff ov]look+ ! sea4 ,an isl& 9 ,*esapeake ,bay cov]$ ov] #djj acres 9 #ahdh1 & ! waves h s9ce r$uc$ x to ab\t fifty acres4 ,/udy %[$ t ! relatively s(t unconsolidat$ /rata ( ! ,na%aquitsa ,cliffs on ! isl& ( ,m>?a's ,v9ey>d1 7 cut back at ! rate ( #e-a_/b feet p] ye>1 betwe5 #ahdf & #ahhf4 ,if "p ( ! relatively smoo? sea bottom %\ld be rais$ into l&1 ! result+ %ore l9e w\ld ( c\rse1 be regul> & free f ind5tations or %>p embaym5ts4 ,examples ( su* coa/ :i* are v "y are at ,cape ,nome1 ,alaska2 ! nor!rn coa/ ( ,spa92 & ! we/ coa/ ( nor!rn ,s\? ,am]ica4 ,soon1 h[ev]1 su* a %ore l9e is attack$1 &1 ei!r :]e ! waves are greate/ or ! rocks are weake/1 ind5tations w result & ! :ole coa/ is gradually eat5 back until ! p[] ( ! waves is l>gely sp5t 9 travel+ across ! %all[ wat] %elf4 ,s& b>s are !n built across ! m\?s ( ! bays or ind5tations :i* lat] ! riv]s gradually fill up ) s$im5t4 ,! result is a relatively /raight or regul> old %ore l9e4 ,! coa/ ( ,texas has ab\t rea*$ ?is /age4 ,if a portion ( ! relatively rugg$ l& surface %\ld become subm]g$ "u ! sea1 a v irregul>1 deeply ind5t$ %ore l9e w\ld result1 due to ! entrance ( tidewat] into ! valleys4 ,! deeply ind5t$ coa/ ( ,ma9e is a f9e example ( a v irregul> y\?ful %ore l9e produc$ by geologically rec5t s9k+ ( a rugg$1 hilly region s t tidewat] backs = miles into ! l[] rea*es ( ! riv] valleys4 ,! promontories & isl&s are und]go+ rapid we>1 & ! developm5t ( b>s across ! inlets has sc>cely begun4 ,o!r excell5t examples are ! coa/s ( ,norway & s\!rn ,alaska4 ,su* a coa/ is !n attack$ by ! ocean waves & ! promontories are cut back until ! broad %all[ wat] %elf is =m$1 aft] :i* s& b>s are built across ! rema9+ embaym5ts & ! %ore l9e becomes relatively regul>4 ,x is1 !n1 a rem>kable fact t1 :e!r %ore l9es orig9ate by em]g5ce ( sea bottom1 or by s9k+ ( l&1 !re is a v /rong t5d5cy on ! "p ( nature to develop regul> %ore l9es4 ,x %\ld be /at$ t ! pr9ciples ( wave "w & %ore-=m developm5t j outl9$ apply almo/ equally well to lakes1 especially l>ge ones4 ,be=e leav+ ?is subject ( %ore-l9e developm5t1 m5tion %\ld be made ( ! fact t b>s & bea*es are (t5 built "p way or :olly across embaym5ts ( ! coa/ ) surpris+ rapidity4 ,to illu/rate1 ,s&y ,hook1 ,new ,j]sey1 is advanc+ nor?w>d1 :ile ,rockaway ,bea*1 ,new ,york1 is ext5d+ we/w>d1 ! t5d5cy be+ to close up ! entrance to ,new ,york h>bor & to make ! l9e ( sea%ore m ne>ly regul>4 ,records %[ t ,rockaway ,bea* actually advanc$ we/w>d m ?an ?ree miles betwe5 ! ye>s #ahce & #aijh4 ,,*apt] ,v ,,glaci]s ,,& ,,_! ,,"w ,a glaci] may be def9$ z a mass ( fl[+ ice4 ,! motion may n be t ( fl[age 9 ! usually accept$ s5se ( ! t]m4 ,a discussion ( ! v>i\s !ories ( glaci] motion w n "h be attempt$4 ,glaci]s =m only 9 regions ( p]petual sn[1 b !y commonly move d[n f> bel[ ! l9e ( p]petual sn[ ( any giv5 region4 ,9 ! pol> regions !y may =m ne> sea level1 :ile 9 ! tropics !y =m at altitudes ( two to ?ree miles1 & !re only r>ely4 ,9 s\!rn ,alaska1 ! l[] limit ( p]petual sn[ is ab\t #e1jjj feet above sea level1 & _m ( ! glaci]s come d[n to sea 7,plate #d71 :ile 9 ! ,alps1 ! l[] limit ( p]petual sn[ is at ab\t #i1jjj feet1 & ! glaci]s desc5d z mu* z #e1jjj feet bel[ x4 ,9 regions ( p]petual sn[ !re is a t5d5cy = m or less sn[ to accumulate fa/] ?an x c be remov$ by evaporation or melt+4 ,z su* sn[ accumulates x gradually und]goes a *ange1 especially 9 its l[] p>ts1 fir/ into granulat$ sn[ 7s-call$ nv7 & !n into solid ice4 ,sn[ drifts 9 ! nor!rn ,unit$ ,/ates (t5 und]go simil> trans=mation1 aft] a few mon?s fir/ to nv1 & !n to ice4 ,?is trans=mation seems to be br\ght ab\t ma9ly by weight ( ov]ly+ sn[ :i* compacts ! sn[ cry/als2 by ra9 or melt+ sn[ p]colat+ into ! sn[ to freeze & fill spaces betwe5 ! sn[ cry/als2 & by ! actual gr[? ( ! cry/als !mselves4 ,:5 ice ( suffici5t ?ickness has accumulat$ 7probably at be/ sev]al hundr$ feet71 ! spread+ action or fl[age beg9s & a glaci] has develop$4 ,r5ew$ sn[falls ov] ! ga!r+ gr\nd keep up ! supply ( ice4 ,!re are sev]al types ( glaci]s3 valley or alp9e glaci]s2 cliff or hang+ glaci]s2 pi$mont glaci]s2 ice caps2 & cont95tal ice %eets4 ,a valley or alp9e glaci] consi/s ess5tially ( a /ream ( ice sl[ly fl[+ d[n a valley & f$ f a cat*m5t bas9 ( sn[ )9 a region ( p]petual sn[4 ,9 ! ,alps1 :]e glaci]s ( ?is sort are v typically %[n1 !y v>y 9 l5g? up to eight or n9e miles4 ,p]haps ! gr&e/ display ( great valley glaci]s is 9 s\!rn ,alaska :]e !y atta9 l5g?s up to =ty or fifty miles & wid?s ( "o or two miles 7,plate #d74 ,hang+ or cliff glaci]s are 9 _m ways l valley glaci]s1 b !y are g5]ally small]2 !y develop 9 sn[-fill$ bas9s above ! sn[ l9e usually on /eep m\nta9 sides2 & !y d n rea* d[n into well-def9$ valleys4 ,mo/ ( ! glaci]s ( ! ,glaci] ,national ,p>k 9 ,montana & _m ( ^? 9 ! ,cascade ,m\nta9s are ( ?is type4 ,m\nt ,ra9i] 9 ,wa%+ton is "o ( ! mo/ rem>kable s+le l>ge m\nta9 peaks 9 ! _w1 9 reg>d to developm5t ( glaci]s ov] x4 ,great tongues ( ice1 />t+ mo/ly at #h1jjj to #aj1jjj feet above sea level1 fl[ d[n ! sides ( ! m\nta9 = di/ances ( to f\r & ev5 six miles4 ,! total area ( ice 9 ?is rem>kable sy/em ( radiat+ glaci]s on ?is "o m\nta9 is ov] =ty squ>e miles4 ,^! ,m\nt ,ra9i] glaci]s are 9 g5]al be/ classifi$ z int]m$iate 9 type betwe5 valley & hang+ glaci]s4 ,illu/ration3 ,fig4 #f4--,map ( ,m\nt ,ra9i]1 ,wa%+ton1 %[+ its wond]ful sy/em ( glaci]s :i* cov]s m ?an #dj squ>e miles4 ,dott$ portions repres5t mora9es4 7,u4 ,s4 ,geological ,survey47 ,9 "s high latitude areas1 z 9 ,icel& & ,spitzb]g51 sn[ & ice may accumulate on relatively level pla9s or plateaus & sl[ly spread or fl[ radially f _! c5t]s4 ,^! are call$ ice caps4 ,ord9>y ice caps usually d n cov] m ?an "s hundr$s ( squ>e miles4 ,cont95tal glaci]s or ice %eets are1 9 pr9ciple1 mu* l ice caps1 b !y are l>g]4 ,gre5l& is buri$ "u an ice %eet ( mod]ate size 7ab\t #ejj1jjj squ>e miles71 ! motion be+ outw>d 9 all directions t[>d ! sea4 ,tongues ( ice1 l valley glaci]s1 are commonly s5t (f f ! ma9 body ( ice across ! l& bord] ( ,gre5l& into ! sea4 ,! size ( ! great ice %eet ( ,ant>ctica is n def9itely kn[n1 b x cov]s probably at lea/ sev]al million squ>e miles4 ,two cont95tal ice %eets ( special int]e/ to ! geologi/ are ^? :i* exi/$ dur+ ! great ,ice ,age ( ! ,quat]n>y p]iod4 ,"o ( ^! !n cov]$ ne>ly #d1jjj1jjj squ>e miles ( ,nor? ,am]ica1 :ile ! o!r cov]$ ab\t #fjj1jjj squ>e miles ( nor!rn ,europe4 ,! ma9 facts reg>d+ ! ,ice ,age are giv5 9 a succe$+ *apt]4 ,! facts br\ght out 9 ! pres5t discussion ( exi/+ glaci]s w greatly aid 9 und]/&+ ! ,ice ,age4 ,h[ fa/ d glaci]s fl[8 ,bas$ ^u _m obs]vations1 we may say t an av]age rate ( fl[ = ! glaci]s ( ! _w is n m ?an a few feet p] day4 ,a v exceptional case is a l>ge glaci]1 bran*+ (f z a tongue f ! ice %eet ( ,gre5l&1 :i* is said to move sixty to sev5ty-five feet p] day4 ,"s ( ! great ,alaskan glaci]s h be5 f\nd to fl[ f f\r to =ty feet p] day4 ,mo/ glaci]s ( ! ,alps move only "o to two feet p] day4 ,a glaci] advances only :5 ! rate ( motion is great] ?an ! rate ( melt+ ( its l[] end & vice v]sa 9 ! case ( retreat4 ,?us x is true1 ?\gh seem+ly p>adoxical1 to ass]t t a glaci] has a con/ant =w>d motion ev5 :5 x is retreat+ by melt+4 ,by wat*+ ! *ang+ position ( m>k$ objects plac$ 9 ! ice1 x has be5 prov$ t1 9 a valley glaci]1 ! top moves fa/] ?an ! bottom2 ! middle moves fa/] ?an ! sides2 ! rate ( motion increases ) ?ickness ( ice1 slope ( floor ov] :i* x moves1 & temp]ature4 ,ice1 l molasses c&y1 t5ds to crack :5 subject$ to a relatively sudd5 =ce1 & :]e ! ice rides ov] a sali5t on ! b$ ( ! glaci]1 transv]se cracks or fissures (t5 develop4 ,due to m rapid motion ( ! c5tral "p ( a valley glaci]1 /resses & /ra9s are set up & crevasses are =m$1 usually po9t+ obliquely up/ream4 ,:]e ! ice t5ds to spread lat]ally 9 a broad portion ( a valley1 longitud9al cracks may develop4 ,crevasses v>y 9 size up to sev]al feet 9 wid? & hundr$s ( feet 9 dep?4 ,ow+ to ! =w>d motion ( ! ice1 old fissures t5d to close up & new ones =m1 &1 aid$ by unev5 melt+1 ! surface ( a glaci] is g5]ally v r\gh4 ,l runn+ wat]1 ice may h consid]able erosive p[] :5 x is prop]ly suppli$ ) tools4 ,! total erosive effect :i* has be51 & is n[ be+1 accompli%$ by ice comp>$ ) t ( runn+ wat] is1 h[ev]1 slight4 ,"o ( ! ma9 processes by :i* ice erosion is accompli%$ is corrasion due to ! rubb+ or gr9d+ action ( h>d rock fragm5ts froz5 into ! bottom & sides ( ! glaci]4 ,?ick ice1 %od ) h>d rock fragm5ts & fl[+ ?r\gh a deep1 n>r[ valley ( s(t rock1 is especially p[]ful z an erosive ag5t because ! abrasive tools are suppli$2 ! "w to be done is easy2 & ! deep ice causes great pressure on ! bottom & l[] sides ( ! valley4 ,rock surfaces :i* h be5 ?us subject$ to ice erosion are *>act]i/ically smoo!d & m or less scrat*$1 /riat$1 or gr\nd due to ! corrosive effects ( small & l>ge rock fragm5ts4 ,?is af=ds "o ( ! be/ means ( prov+ ! =m] pres5ce ( a glaci] ov] a region or 9 a valley4 ,a typical ,v-%ap$ /ream cut 7erod$7 valley is *ang$ into "o ) a ,u-%ap$ pr(ile or cross section by glaci] erosion 7,plate #e74 ,ano!r important process ( ice erosion is pluck+1 :i* consi/s 9 pu%+ among already m or less loos5$ jo9t blocks by ! pressure ( ! mov+ ice4 ,! pressure ?us ex]t$1 especially by a deep valley glaci]1 may be enorm\s4 ,?is process 0 an important factor 9 ! developm5t ( ! fam\s ,yosemite ,valley1 a v brief acc\nt ( ^: hi/ory x w n[ be in/ructive to give4 ,illu/ration3 ,plate #c4--,! ,gorge ( ,niag>a ,riv] ,bel[ ! ,great ,falls4 ,! /rata 7conta9+ fossils7 7 accumulat$ on ! bottom ( ! ,silurian sea :i* ov]spread ! region at lea/ #ah1jjj1jjj ye>s ago4 ,s9ce ! ,ice ,age or )9 #bj1jjj to #dj1jjj ye>s1 ! riv] has c>v$ out ! gorge4 7,c\rtesy ( ! ,ha9es ,photo ,company1 ,conneaut1 ,ohio47 ,illu/ration3 ,plate #d4--7;a7 ,a ,w9d+ ,/ream 9 ! ,/4 ,lawr5ce ,valley ( ,new ,york4 ,due to its l[ velocity ! /ream cuts its *annel d[n v little1 b x sw+s or me&]s sl[ly f "o side ( its valley to ! o!r1 develop+ a wide flood pla94 ,! /ream once fl[$ aga9/ ! valley wall %[n at ! middle left4 7,photo by ! au?or47 ,illu/ration3 ,plate #d4--7;b7 ,davidson ,glaci]1 ,alaska4 ,?is glaci] is at "w sl[ly gr9d+ d[n ! valley floor & cutt+ back its walls1 ?us *ang+ ! orig9al /ream-cut1 ,v-%ap$ pr(ile1 l t ( ,plate #e4 7,photo by ,wright1 ,u4 ,s4 ,geological ,survey47 ,! ,yosemite ,valley1 ab\t #g miles long1 less ?an "o mile wide1 & f #b1jjj to #d1jjj feet deep1 lies on ! we/]n slope ( ! ,si]ra ,nevada ,m\nta9s ( ,cali=nia4 ,great cliffs ( granite1 mo/ly f #a1jjj to ov] #c1jjj feet high1 b\nd ! valley on ei!r side4 ,! floor ( ! valley is wide & rem>kably flat 7,plate #f74 ,j prior to ! ,ice ,age1 by ! processes ( erosion already set =?1 ! ,m]c$ ,riv] _h c>v$ out a great /eep-sid$ ,v-%ap$ canyon commonly f #a1jjj to #c1jjj feet deep4 ,dur+ ! ,ice ,age1 two glaci]s jo9$ to =m an extra deep p[]ful glaci]1 :i* fl[$ ?r\gh a deep "p ( ! ,m]c$ ,canyon & modifi$ x into ! ,yosemite ,valley1 ess5tially z we see x to-day4 ,because ! ice 0 %od ) _m fragm5ts ( h>d rock 7granite71 & ! pressure at ! bottom & l[] sides ( ! glaci] 7sev]al ?\s& feet ?ick7 0 s great1 ! ,v-%ap$ /ream-cut canyon 0 *ang$ to a ,u-%ap$ canyon ) v /eep to ev5 v]tical walls4 ,a factor ( great importance :i* notably aid$ ! erosive p[] ( ! glaci] 9 ?is case 0 ! exi/5ce ( an unusual numb] ( l>ge v]tical jo9t cracks 9 ! granite 9 ?is local region4 ,! pluck+ action ( ! ice 0 ?us v greatly facilitat$ & great slabs ( rock1 sep>at$ by ! v]tical jo9ts1 especially t[>d ! l[] sides & bottom ( ! valley1 7 pu%$ away "o aft] ano!r by ! ice4 ,:5 ! ice disappe>$1 great precipit\s jo9t faces f #a1jjj to #c1jjj feet high 7 left along ! valley sides4 ,at its l[] end ! glaci] left a dam ( glacial dbris 7mora9e7 across ! valley1 ?us caus+ a lake to =m ov] ! valley floor4 ,! wide flat bottom ( ! valley 0 caus$ by fill+ up ( ! lake ) s$im5t4 ,! uniqu5ess ( ! ,yosemite ,valley is1 !n1 due to a rem>kable comb9ation ( sev]al ma9 factors2 "o1 ! pres5ce ( a l>ge swift riv] well suppli$ ) tools :i* c>v$ out a deep ,v-%ap$ canyon2 two1 a mighty glaci] :i* pl[$ its way ?r\gh ?is canyon & conv]t$ x by erosion into a ,u-%ap$ canyon2 ?ree1 ! weak5+ ( ! rock by _m jo9t cracks1 ?us greatly facilitat+ ! ice erosion2 & f\r1 a po/glacial lake cov]+ ! valley floor :i* became fill$ ) s$im5t4 ,z a result ( ! ice "w1 sev]al /reams1 tribut>y to ! ma9 /ream 7,m]c$ ,riv]7 :i* fl[s ?r\gh ! bottom ( ! valley1 7 =c$ to plunge ov] great v]tical rock walls 7jo9t faces71 ?us produc+ high & beautiful true wat]falls1 includ+ ! v high ,upp] ,yosemite ,fall :]e ,yosemite ,creek makes a /raight drop ( #a1dcj feet4 ,a tribut>y valley l t ( ,yosemite ,creek1 :i* ends abruptly well above ! ma9 valley1 is kn[n z a hang+ valley4 ,! valley ( ,bridal ,veil ,creek is ano!r good example4 7,see ,plate #f47 ,valleys :i* 7 once occupi$ by active glaci]s are g5]ally *>act]iz$ by _! ,u-%ap$ cross sections & _! hang+ 7tribut>y7 valleys1 b ! great height & /eepness ( ! valley walls 9 ,yosemite are exceptional4 ,a type ( glacial erosion :i* is ( special int]e/ is ! sculptur+ ( s-call$ cirques or amphi!at]s 9 m\nta9s )9 ! region ( p]petual sn[4 ,:]e ! ma9 mass ( sn[ & ice 9 ! cat*m5t bas9 or ga!r+ gr\nd ( a valley glaci] pulls away f ! sn[ & nv on ! upp] slopes1 ! rock wall is m or less expos$ 9 ! deep crevasse4 ,dur+ w>m days wat] fills ! jo9t cracks 9 ! rocks d[n 9 ?is crevasse 7s-call$ ,b]gs*rund71 & dur+ cold nights ! wat] freezes & =ces ! blocks ( rock ap>t4 ,?is is greate/ t[>d ! bottom ( ! crevasse & s1 by ?is excavat+ or qu>ry+ process1 v]tical or v /eep walls are develop$ ar\nd a great b[like bas9 or cirque4 ,su* cirques1 n[ free f glacial ice1 ) precipit\s walls #ejj to #b1jjj feet high & "o-f\r? ( a mile to "o-half ( a mile across1 are common 9 ! ,si]ra ,nevada & ,cascade ,ranges & 9 ! ,rocky ,m\nta9s4 ,:at becomes ( ! mat]ials erod$ by ! ice8 ,an answ] to ?is "q involves at lea/ a brief discussion ( ! deposition ( glacial dbris1 ?is con/itut+ an important feature ( ! "w ( ice4 ,! dbris transport$ by a glaci] is c>ri$ ei!r on its surface or )9 x1 or pu%$ along "u x4 ,x is g5]ally het]og5e\s mat]ial rang+ f ! f9e/ clay ?r\gh s& & gravel1 to b[ld]s ( _m tons' weight4 ,v>i\s types ( glacial deposits are abundantly illu/rat$ by dbris left /rewn ov] mu* ( ! nor!a/]n ,unit$ ,/ates & "s ref]5ce to ^! w be made4 ,mo/ valley glaci]s c>ry consid]able dbris on _! surfaces1 ?is repres5t+ mat]ial :i* falls or is c>ri$ d[n f ! valley walls ^u ! m>g9s ( ! ice1 ?us =m+ m>g9al mora9es4 ,:5 two glaci]s fl[ toge!r1 "o m>g9al mora9e f ea* w coalesce to =m a m$ial mora9e4 ,! mat]ial c>ri$ along at ! bottom ( a glaci] is call$ ! gr\nd mora9e4 ,:]e x conta9s mu* v f9e gra9$ mat]ial ) pebbles or b[ld]s scatt]$ ?r\gh its mass1 x is call$ till or b[ld] clay4 ,! pebbles or b[ld]s ( ! gr\nd mora9e are commonly facett$ & /riat$ z a result ( hav+ be5 rubb$ aga9/ ! b$rock on :i* ! glaci] mov$4 ,gr\nd mora9e mat]ial is ! mo/ ext5sively develop$ ( all glacial deposits4 ,x is s widely scatt]$ ov] ! glaciat$ nor!a/]n portion ( ! ,unit$ ,/ates t mo/ ( ! soils consi/ ( x1 hav+ be5 left /rewn ov] ! c\ntry dur+ ! melt+ ( ! va/ ice %eet4 ,:5 a glaci] rema9s practically /ation>y = "s "t1 m or less mat]ial :i* x c>ries is pil$ up at its l[] end to =m a t]m9al mora9e4 ,repeat$ pauses dur+ g5]al glaci] retreat p]mit ! accumulations ( s-call$ recessional mora9es4 ,a wond]ful display ( recessional mora9es occurs f ! ,great ,lakes s\?1 :]e !y are fe/oon$ "o )9 ano!r & rema9 almo/ exactly z !y 7 =m$ dur+ pauses 9 retreat ( great lobes ( ice dur+ ! clos+ /ages ( ! ,ice ,age4 ,a great t]m9al mora9e m>ks ! s\!rnmo/ limit ( ! ice %eet dur+ ! ,ice ,age1 a v f9e illu/ration be+ ! ridge ( l[ irregul> hills ext5d+ ! :ole l5g? ( ,long ,isl&4 ,"s ( ! mat]ial 9 t mora9ic ridge 0 transport$ by ! ice f nor!rn ,new ,engl&4 ,consid]able rock dbris is transport$ )9 ! ice1 & su* englacial mat]ial 9 "p results f rock dbris :i* falls on ! surface 9 ! cat*m5t bas9 & becomes buri$ "u new sn[falls :i* *ange to ice1 & 9 "p f mat]ial :i* falls into ! crevasses 9 ! glaci] f>!r d[n ! valley4 ,m>k$ objects ?r[n into ! cat*m5t bas9 h1 aft] _m ye>s1 em]g$ at or ne> ! end ( ! glaci]2 ?us ! rate ( motion c be v accurately told4 ,a v rem>kable case ( transportation ?r\gh ! body ( a glaci] is ! foll[+3 ,9 #ahbj1 ?ree m5 7 buri$ "u an avalan*e 9 ! cat*m5t bas9 ( ! ,bossons ,glaci] 9 ! ,alps4 ,=ty-"o ye>s lat] sev]al p>ts ( ! bodies1 includ+ ! ?ree heads toge!r ) "s pieces ( clo?+1 em]g$ at ! foot ( ! glaci] aft] travel+ mo/ ( its l5g? at ! rate ( eight in*es p] day4 ,! heads 7 s p]fectly pres]v$ aft] _! rem>kable j\rney 9 cold /orage t !y 7 cle>ly recogniz$ by =m] fri5ds6 ,:]e a valley floor slopes d[nw>d away f ! end ( a glaci]1 wat]s em]g+ f ! ice1 heavily load$ ) rock dbris1 cause m or less deposition ( ! dbris on ! valley floor (t5 = miles beyond ! ice front4 ,su* a deposit is call$ a valley tra94 ,:5 ! ice front pauses = a consid]able "t ^u a r flat surface1 ! dbris-lad5 wat]s em]g+ f ! ice develop an outwa% pla9 by deposition ( s$im5t r uni=mly ov] ! flat surface4 ,a v f9e example is ! pla9 :i* con/itutes mo/ ( ! s\!rn half ( ,long ,isl& j beyond ! s\!rn limit ( ! great t]m9al mora9e ridge4 ,a type ( glacial deposit ( p>ticul> int]e/ is ! druml9 :i* is1 9 reality1 only a special =m ( gr\nd mora9e mat]ial 7commonly till71 &1 !re=e1 ess5tially un/ratifi$4 ,typical druml9s are l[1 r\nd$ m\nds ( till ) r\ghly elliptical bases & /eep] fronts fac+ ! direction f :i* ! ice fl[$4 ,_! long axes are always p>allel to ! direction ( ice movem5t4 ,9 height !y commonly range f #ej to #bjj feet4 ,_! mode ( orig9 is n yet def9itely kn[n1 b !y =m ne> ! m>g9s ( broad lobes ( ice ei!r by erosion ( e>li] glacial deposits1 or by accumulation b5ea? ! ice "u peculi>ly favorable conditions1 z p]haps 9 ! longitud9al crevasses4 ,"o ( ! f9e/ & mo/ ext5sive exhibitions ( druml9s 9 ! _w is 9 we/]n ,new ,york betwe5 ,syracuse & ,ro*e/]4 ,?\s&s ( druml9s !re rise above ! g5]al level ( ! ,ont>io pla91 ! ,new ,york ,c5tral ,railroad pass+ ?r\gh ! v mid/ ( !m4 ,druml9s are also abundant 9 ea/]n ,wiscons94 ,ano!r type ( glacial deposit 9 ! =m ( l[ hills is ! kame :i*1 unlike ! druml91 always consi/s ( m or less /ratifi$ mat]ial4 ,kames are seldom ov] #bjj feet high1 & !y are ( v>i\s %apes4 ,9 _m cases !y =m irregul> gr\ps ( hills1 & 9 o!r cases fairly well def9$ kame ridges4 ,kames =m z deposits f dbris-lad5 /reams em]g+ f ! m>g9s ( glaci]s1 ! wat] sometimes ris+ z great f\nta9s because ( ! pressure4 ,su* deposits are n[ actually 9 process ( =mation along ! edge ( ! great ,malasp9a ,glaci] ( ,alaska4 ,kames are commonly associat$ ) t]m9al & recessional mora9es4 ,esk]s are simil> except t !y are long w9d+ l[ ridges ( /ratifi$ mat]ial deposit$ by dbris-lad5 /reams1 probably 9 longitud9al fissures 9 ! ice ne> its m>g94 7,see ,plate #bj47 ,glacial b[ld]s1 or erratics are blocks ( rock or b[ld]s left /rewn ov] ! c\ntry dur+ ! melt+ ( ! ice4 ,!y v>y 9 size f small pebbles to ^? ( _m tons ( weight1 & mo/ ( !m 7 d]iv$ f l$ges ( relatively h>d1 resi/ant rocks4 7,see ,plate #bj47 ,erratics h v commonly be5 c>ri$ a few miles f _! p>5t l$ges1 :ile m r>ely !y h travel$ ev5 hundr$s ( miles4 ,!y are extremely abundant 9 ,new ,york & ,new ,engl&1 _m occurr+ ev5 high up on ! m\nta9s4 ,9 "s cases erratics ( t5 or m tons' weight h be5 left 9 su* rem>kably balanc$ positions on b$rock t a *ild c cause "o ( !m to sw+ back & =? slightly4 ,su* a b[ld] is lit]ally a rock+ /one4 ,9 ! ,adirondack ,m\nta9s ! writ] rec5tly obs]v$ a r\nd$ erratic ( v h>d rock f\rte5 feet 9 diamet] re/+ 9 a v rem>kably balanc$ position on top ( ano!r l>ge r\nd glacial b[ld]4 ,,*apt] ,,vi ,,! ,,action ,,( ,,w9d ,only dur+ ! la/ qu>t] ( a c5tury h geologi/s come to prop]ly appreciate ! really important geological "w ( ! w9d4 ,"o reason = ?is is ! fact t p live mo/ly 9 humid regions :]e ! soils are l>gely effectually protect$ aga9/ w9d action by ! vegetation4 ,b ev5 9 su* regions1 w9d action is by no means negligible4 ,"o has b to obs]ve ! great cl\ds ( du/ rais$ by /rong w9d f fre%ly cultivat$ fields dur+ a little dry wea!r 9 ! late spr+4 ,mu* ( ?is du/ is c>ri$ consid]able di/ances1 (t5 miles1 & 9 "s cases "y crops are injur$ by removal ( soil f ar\nd ! roots1 :ile 9 o!r cases "y plants are buri$ by deposition ( ! w9d-bl[n mat]ial ov] !m4 ,9 humid regions1 ! action ( ! w9d is p]haps mo/ /rik+ly exhibit$ along & ne> %ores ( sea & lakes1 :]e loose dry s&s are pick$ up & transport$ 9 great quantities1 (t5 deposit+ !m z s& dunes1 :i* may =m gr\ps ( hills cov]+ consid]able areas4 ,v conspicu\s examples are ! s& dunes ( ,dune ,p>k 9 nor!rn ,indiana1 & ! dunes along ! coa/ ( ,new ,j]sey4 ,b ! action ( w9d is mo/ /rik+ly effective 9 des]t & semi>id regions4 ,! importance ( ! "w ( w9d is made m impressive :5 we realize t ab\t "o-fif? ( ! l& ( ! e>? is des]t4 ,9 des]ts "s ( ! ord9>y ag5ts ( wea!r+ & erosion are ei!r abs5t or notably r$uc$ 9 effectiv5ess4 ,?us1 /ream action is1 9 g5]al1 r$uc$ to a m9imum2 wea!r+ effects due to moi/ure 9 ! air are notably r$uc$1 & ei!r fro/ action1 or w$ge "w ( ice1 is relatively unimportant due to lack ( wat]4 ,*ange ( temp]ature betwe5 night & day is1 h[ev]1 unusually important z a process :]eby rocks are brok5 up due to relatively rapid expansion & contraction 9 des]ts because su* temp]ature *anges are exceptionally great1 & rocks & soils are almo/ ev]y:]e directly expos$1 be+ free f vegetation4 ,! f9] gra9$ mat]ials1 especially s& gra9s1 9 des]ts are pick$ up by ! w9d & driv51 (t5 ) great velocity1 aga9/ b>r5 rock l$ges & l>ge & small rock fragm5ts4 ,by ?is process 7corrasion7 ! rocks are worn & (t5 poli%$ by ! mat]ials bl[n aga9/ !m4 ,! pr9ciple is t ( ! artificial s&-bla/1 us$ 9 et*+ glass1 or clean+ & poli%+ build+ & decorative /ones4 ,"u favorable conditions w9d-driv5 s& accompli%es noticeable erosion 9 a surpris+ly %ort "t4 ,?us1 9 a h>d w9d /orm1 a plate glass w9d[ 9 a ligh?\se on ,cape ,cod 0 worn to opaqu5ess1 :ile 9 a few weeks or mon?s ! directly expos$ w9d[ glass may !re be worn ?r\gh4 ,! great erosive effect ( w9d-driv5 s& is relatively close to ! gr\nd because ! l>g] & heavi] fragm5ts are n lift$ to v consid]able heights4 ,= ?is reason ord9>y telegraph poles are difficult to ma9ta9 9 des]t regions because1 unless !y are specially protect$1 !y are soon cut d[n by s& swept aga9/ _! bases4 ,9 ! des]t regions ( our ,s\?we/]n ,/ates cliffs ris+ above ! g5]al level ( ! c\ntry are (t5 und]cut by w9d erosion1 sometimes ) ! developm5t ( l>ge cav]ns4 7,see ,plate #a47 ,ev5 ! high portions ( great l$ges are !re m or less fanta/ically sculptur$ by w9d erosion1 ! s(t] portions be+ m deeply cut into ?an ! h>d]4 ,! fam\s sph9x ( ,egypt has be5 notably r\gh5$ by action ( ?is k9d4 ,! enorm\s p[] ( high w9ds to transport rock mat]ial 9 des]t regions is /rik+ly illu/rat$ by ! great s& /orms ( ! ,sah>a ,des]t1 :]e s& & du/1 =m+ cl\ds ) cubic miles ( volume1 sweep = _m miles across ! c\ntry4 ,"s "o has e/imat$ t e cubic mile ( air 9 su* a /orm conta9s m ?an #ajj1jjj tons ( rock mat]ial4 ,x is said t an army ( #ej1jjj m5 "u ,cambyses 0 buri$ "u ! s&s ( a /orm 9 ! des]t ( nor!rn ,africa4 ,du/ f "s ( ^! /orms is kn[n to be driv5 hundr$s ( miles out ov] ! ,atlantic ,ocean1 !re to settle 9 ! sea4 ,9 m\nta9\s des]t regions1 l ! ,great ,bas9 ( our ,we/]n ,/ates1 ! g5]al t5d5cy is = ! rock mat]ials w9d-erod$ f ! m\nta9s to be c>ri$ into ! int]montane bas9s or valleys4 ,"s bas9s ( ?is sort are believ$ to conta9 dep?s ( #a1jjj to #b1jjj feet ( w9d-bl[n mat]ial4 ,a special k9d ( w9d-bl[n mat]ial call$ loess1 is a sort ( f9e-gra9$ yell[1 or br[n loam :i*1 ?\gh relatively unconsolidat$1 has a rem>kable prop]ty ( /&+ out z high /eep cliffs or bluffs along ! banks ( /reams4 ,_m ?\s&s ( squ>e miles ( nor!rn ,*9a are cov]$ ) loess4 ,among _m o!r regions1 ?\s&s ( squ>e miles ( p>ts ( ! ,/ates ( ,i[a1 ,nebraska1 & ,kansas are cov]$ ) loess1 :i*1 9 ?is case1 is believ$ to be f9e mat]ial ga!r$ by w9ds f ! region j aft] ! retreat ( "o ( ! ice %eets ( ! great ,ice ,age1 :5 !re 0 v little vegetation to hold d[n ! loose soils ( glacial orig94 ,mu* z sn[drifts are =m$1 s1 9 _m places1 ! w9d-driv5 s&s are built up into s& hills or s-call$ dunes4 ,dunes are v common 9 _m places1 z = example1 along our middle ,atlantic coa/2 9 ,dune ,p>k ( nor!rn ,indiana2 & 9 ! great arid & semi>id regions ( ! ,we/]n ,/ates4 ,:]e !re is a di/9ctly prevail+ direction ( w9d1 ! s& is bl[n to ! leew>d side f ! w9dw>d side1 & ! dunes are caus$ to migrate 9 ! direction ( ! w9d4 ,! burial & de/ruction ( =e/s1 & ! uncov]+ ( ! dead trees is n uncommonly caus$ by migration ( s& dunes1 all /ages ( ?is ph5om5on be+ well exhibit$ 9 ,dune ,p>k1 ,indiana4 ,! rate ( dune migration is v v>iable1 b /udy 9 a numb] ( places has %[n a rate ( f a few feet to m ?an #ajj feet p] ye>4 ,arable l&s1 build+s1 & ev5 t[ns h be5 encroa*$ ^u & buri$ "u drift+ s&4 ,an int]e/+ example is a *ur* 9 ! village ( ,kunz51 on ! ,baltic sea%ore :i*1 9 a p]iod ( sixty ye>s1 became completely buri$ "u a dune & !n completely uncov]$ by migration ( ! dune4 ,mu* de/ruction has be5 wr\ght by %ift+ s&s on ! ,bay ( ,biscay1 :]e f>ms & ev5 villages h be5 ov]:elm$4 ,! ru9s ( ! anci5t cities ( ,babylon & ,n9eveh are buri$ mo/ly "u w9d-bl[n s& & du/4 ,!re is good reason to believe t ! climate ( c5tral & we/]n ,asia is n[ notably dri] ?an x 0 a few ?\s& ye>s ago1 & ?is may help to expla9 ! burial ( _m old cities & villages !re "u w9d-bl[n deposits4 ,,*apt] ,,vii ,,in/ability ,,( ,,! ,,e>?',s ,,cru/ ,! cru/ ( ! e>? is un/able4 ,to ! mod]n /ud5t ( geology ! old notion ( a t]ra firma is outworn4 ,! idea ( an un%akable1 immovable e>? c\ld nev] h emanat$ f ! inhabitants ( an e>?quake c\ntry4 ,9 g5]al we may recognize two types ( cru/al movem5ts--sl[ & sudd54 ,to mo/ p ! sudd5 movem5ts accompani$ by e>?quakes are m significant & impressive because !y are m localiz$ & evid5t1 & (t5 accompani$ by de/ruction ( prop]ty1 or quick1 ?\gh m9or1 *anges 9 ! l&scape4 ,b movem5ts :i* take place sl[ly & quietly are (t5 ( f> great] significance 9 ! int]pretation ( ! pr(\nd physical *anges :i* h affect$ ! e>? dur+ its millions ( ye>s ( kn[n hi/ory4 ,illu/ration3 ,fig4 #g4--,/ructure section across ! ,hudson ,riv] ,valley ne> ,we/ ,po9t1 ,new ,york4 ,! %afts & tunnel1 #a1bjj feet bel[ sea level1 9 solid rock1 %[ ! position ( ! ,new ,york ,city aqu$uct f ! ,catskills4 ,! ,preglacial valley has be5 subm]g$ & fill$ ) ,po/glacial s$im5t to a dep? ( ne>ly #hjj feet4 7,r$rawn by ! au?or aft] ,b]key1 f ,new ,york ,/ate ,museum ,bullet947 ,a few well-kn[n examples w s]ve to prove t upw>d1 d[nw>d1 & diff]5tial movem5ts ( ! e>?'s cru/ h actually tak5 place n only 9 ! remote ages ( geologic "t1 b also t su* movem5ts h geologically rec5tly tak5 place1 & t simil> movem5ts are /ill go+ on4 ,x is v important t ! read] ?or\ghly appreciate ! fact t cru/al di/urbances1 (t5 pr(\nd ones1 d take place1 because ?is is "o ( ! mo/ fundam5tal t5ets ( geologic sci5ce4 ,let u consid] ! case ( ! ,hudson-,*ampla9-,/4 ,lawr5ce ,valley region4 ,t ! :ole region 0 once notably high] 7at lea/ #a1jjj feet7 ?an at pres5t is prov$ by ! dr[n$ "* ( ! ,hudson ,valley1 9 :i* tidewat] ext5ds nor?w>d = #aej miles to ne> ,troy4 ,:]e ! ,new ,york ,city ,aqu$uct passes "u ! ,hudson ,riv] ne> ,newburgh1 ! b$rock bottom ( ! old riv] *annel is n[ ab\t #hjj feet bel[ sea level z det]m9$ by drill+4 ,?is old *annel is !re fill$ up ne>ly to sea level ) glacial & po/glacial rock dbris1 :i* %[s t ! old *annel mu/ h be5 cut be=e ! oncom+ ( ! ice ( ! great ,ice ,age4 ,be=e ! ,ice ,age1 !n1 ! l[] ,hudson ,valley mu/ h be5 consid]ably m ?an #hjj feet high] ?an at pres5t1 because x !n conta9$ a riv] ) suffici5t curr5t to be an active ag5t ( erosion1 c>v+ out ! canyonlike valley 9 ! vic9ity ( ,we/ ,po9t4 ,?is conclusion is /rongly re5=c$ by ! fact t ! old valley ( ! ,hudson ,riv] has be5 def9itely trac$ z a di/9ct tr5* across ! %all[ sea bottom = ab\t #ajj miles ea/w>d f ! entrance to ,new ,york h>bor4 ,t[>d ! ea/]n end ( ?is tr5* ! dep? ( wat] is n[ consid]ably ov] #a1jjj feet1 & ?us x is obvi\s t1 prec$+ ! ,ice ,age1 ! e>?'s cru/ 9 ! vic9ity ( ,new ,york ,city mu/ h be5 mu* high] ?an at pres5t1 s t ! ,hudson ,riv] 0 able to erode its n[ completely dr[n$ *annel4 ,some:at simil> evid5ce has also e/abli%$ ! fact t ! l[] ,/4 ,lawr5ce ,valley region 0 mu* high] be=e ! ,ice ,age4 ,x is evid5t1 !re=e1 t ! g5]al ,hudson-,/4 ,lawr5ce ,valley region is n[ notably l[] ) ref]5ce to sea level ?an x 0 be=e ! ,ice ,age4 ,t ?is 0 caus$ by actual s9k+ ( ! e>?'s cru/ r ?an by a rise ( sea level is prov$ by ! fact t simil> *anges ( level betwe5 l& & sea did n take place at ! same "t ev5 along ! ,atlantic & ,gulf coa/ ( our ,s\!rn ,/ates4 ,we %all n[ proce$ to ! next /ep 9 ! geologically rec5t hi/ory ( e>?-cru/ movem5ts 9 ! ,hudson-,*ampla9-,/4 ,lawr5ce ,valley region by ass]t+ t1 s9ce ! ,ice ,age1 ! l& 0 actually notably l[] ?an at pres5t4 ,9 fact1 ! l& 0 en\gh l[] to all[ tidewat] to ext5d up ! ,/4 ,lawr5ce ,valley into ! ,ont>io bas91 & all ?r\gh ! ,*ampla9-,hudson ,valley4 ,_m bea*es1 b>s1 & delta deposits =m$ 9 ^! arms ( ! sea are /ill pla9ly pres]v$1 9 "s cases ) %ells & bones ( m>9e animals 9 !m1 n[ hundr$s ( feet above sea level4 ,^! m>9e deposits are highe/ above sea level 9 ! nor!rn portion ( ! ,*ampla9 ,valley1 :]e !y lie at an altitude ( #gjj feet or m & _! altitude /eadily dim9i%es s\?w>d to ab\t #cjj to #djj feet 9 ! g5]al vic9ity ( ,albany1 & to ne> sea level 9 ! g5]al vic9ity ( ,new ,york ,city4 ,obvi\sly1 !n1 ! l& /ood l[] dur+ "p or all ( ! int]val ( n m ?an a few t5s ( ?\s&s ( ye>s s9ce ! ,ice ,age ?an at pres5t4 ,?is leads u to ! ?ird important conclusion reg>d+ e>? movem5ts 9 ?is region1 namely1 t /ill lat] ! l& has und]gone a diff]5tial uplift1 ! rate hav+ /eadily increas$ t[>d ! nor? :]e ! total uplift is _m hundr$s ( feet4 ,we h discuss$ ?is region some:at 9 detail because ! pr9ciples ( sl[ up & d[n movem5ts ( ! e>?'s cru/ are !re s pla9ly record$4 ,among _m o!r regions :]e e>? movem5ts simil> to ^? above describ$ h tak5 place1 brief m5tion may be made ( ,norway4 ,! great fjords ( ,norway 71 j be=e ! ,ice ,age1 /ream-cut valleys :i* 7 !n m or less modifi$ by glacial erosion1 & aft] ! ,ice ,age ! riv]s 9 !m 7 dr[n$ due to l& subsid5ce4 ,! k9d ( evid5ce is l t above giv5 = ! l[] ,hudson ,riv]4 ,s9ce ! subsid5ce !re has be5 p>tial reelevation1 z prov$ by ! fact t along ! sides ( ! l>g] fjords m>9e t]races & bea*es may be trac$ ) gradually increas+ altitude = _m miles 7#aej or m7 back into ! c\ntry :]e !y are hundr$s ( feet above tidewat]4 ,sc&9avia is ( /ill fur!r special int]e/ because v appreciable e>? movem5ts h !re come "u human obs]vation4 ,m>ks c>efully plac$ along ! %ores ( ,sw$5 by ! gov]nm5t h prov$ t dur+ ! la/ #aej ye>s ! s\!rn end ( ! c\ntry has actually subsid$ sev]al feet1 :ile f ,/ockholm nor? ! l& has ris5 9 increas+ am\nt1 rea*+ a maximum ( sev5 or eight feet4 ,9 s\!rn ,sw$51 at ,malmo1 a c]ta9 /reet n[ at times becomes cov]$ by w9d-driv5 high wat]1 & dur+ excavations made "s ye>s ago an old] /reet eight feet bel[ ! pres5t "o 0 f\nd4 ,a !ory :i* appe>s to be 9 p]fect h>mony ) ! facts to acc\nt = ! subsid5ce & p>tial reelevation ( c5tral ea/]n ,nor? ,am]ica & ,sc&9avia s9ce ! beg9n+ ( ! ,ice ,age is t ! great weight ( ice dur+ ! ,ice ,age press$ ! l& d[n1 & t s9ce ! removal ( ! ice !re has be5 an appreciable t5d5cy = ! l& to spr+ back4 ,c]ta9 cru/al movem5ts :i* h occurr$ ab\t ! ,bay ( ,naples are ( v special int]e/ because actual human hi/ory dates c be plac$ ^u !m4 ,mo/ rem>kable are ! records 9 connection ) ! temple ( ,jupit] ,s]apis :i* 0 built ne> ! %ore be=e ! ,*ri/ian era4 ,! l& sank ab\t five feet & a new pavem5t _h to be con/ruct$2 !n1 by ! middle ( ! ?ird c5tury ,a4 ,d41 ! temple rose to well above sea level4 ,by ab\t ! n9? c5tury ! l& _h subsid$ fully ?irty feet1 s t m>ble columns ( ! temple 7 bor$ full ( holes z high z tw5ty-"o feet above _! bases by m>9e-%ell$ animals1 species ( :i* /ill live 9 ! bay4 ,!n a sl[ uplift ( tw5ty-?ree feet began1 br++ ! bases ( ! columns two feet above sea level by #agdi4 ,s9ce t "t a slight s9k+ has tak5 place & ?is seems to be /ill go+ on4 ,?ree ( ! m>ble columns ) ! bor+s /ill /& 9 upright position4 ,:ile ! movem5ts j describ$ 7 tak+ place1 ! isl& ( ,capri1 tw5ty miles across ! ,bay ( ,naples1 has sl[ly sunk to an am\nt e/imat$ at ?irty or =ty feet z prov$ by evid5ce f ! fam\s ,blue ,grotto4 ,ab\t ! beg9n+ ( ! ,*ri/ian era a l>ge anci5t wave-cut cave1 "p ( :i* is n[ call$ ! ,blue ,grotto1 _h its floor above sea level1 & x 0 us$ by c]ta9 ,romans z a cool place to retire to f ! heat4 ,9 ord] to obta9 bett] light an op5+ 0 cut ?r\gh its upp] portion4 ,! l& has sunk s mu* t at ! pres5t "t ev5 "p ( ! artificial op5+ 7?r\gh :i* t\ri/s pass7 is n[ "u wat]4 ,by way ( illu/rat+ rem>kable contra/s 9 direction ( cru/al movem5ts on v consid]able scales 9 a giv5 region1 we %all briefly m5tion "s facts reg>d+ "p ( ! coa/ ( s\!rn ,cali=nia & ! neighbor+ isl&s ( ,santa ,catal9a & ,san ,clem5te1 respectively tw5ty-five & fifty miles (f%ore4 ,^? movem5ts 7 n1 h[ev]1 *eck$ up by human hi/ory records4 ,! ma9l& at ,san ,p$ro has cle>ly ris5 #a1bdj feet1 z prov$ by ! pres5ce ( unusually p]fect coa/ t]races 7s-call$ rais$ bea*es71 :ile ,san ,clem5te has ris5 #a1ejj feet z prov$ by ! rais$ bea*es into :i* deep1 y\?ful ,v-%ap$ /ream-cut valleys h be5 sunk1 & a %ore l9e *>act]i/ic ( rec5t notable uplift4 ,x is a rem>kable fact t at ! same "t ! int]v5+ isl& 7,santa ,catal9a7 has notably sunk1 z prov$ by ! nature ( its %ore l9e1 & ! di/9ctly m mature "* ( its topography4 ,we are1 h[ev]1 by no means dep5d5t ^u l&s along sea %ores = evid5ces ( sl[ ris+ & s9k+ ( l&4 ,?us1 by c>eful measurem5ts x has be5 %[n t ! g5]al region ( ! ,great ,lakes is n[ diff]5tially ris+ t[>d ! nor!a/ at ! rate ( ab\t five in*es p] #ajj miles p] c5tury4 ,at ,*icago ! rise ( wat] is e/imat$ at ab\t n9e in*es p] c5tury1 :i* means increase ( fl[age ?r\gh ! ,*icago ,canal4 ,at ?is rate ! upp] lakes w\ld1 9 "s ?\s&s ( ye>s1 dra9 ?r\gh ?is canal to ! ,mississippi4 ,a well-pres]v$ %ore l9e ( ! l>ge ance/or ( ,lake ,ont>io %[s a /eady increase 9 altitude at ! rate ( sev]al feet p] mile t[>d ! nor!a/ f ne> ,niag>a to ! ,/4 ,lawr5ce ,valley1 ?us prov+ a tilt+ ( ! l& s9ce ! %ore l9e 0 =m$4 ,%ore l9es ( ! great ance/or ( ,great ,salt ,lake also %[ w>p+ ( ! e>?'s cru/1 "s p>ts ( a def9ite %ore l9e be+ sev]al hundr$ feet high] ?an o!rs4 ,v significant evid5ce po9t+ to pr(\nd cru/al movem5ts consi/ 9 ! f9d+ ( fossil rema9s ( m>9e animals 9 ! /rata high above sea level1 v commonly f "o to ?ree miles1 9 _m p>ts ( ! _w1 especially 9 ! high m\nta9s4 ,9 ,wyom+1 ne>ly horizontal /rata ( ! ,mesozoic ,age c>ry+ m>9e fossils lie two miles or m above sea level4 ,! fact t giv5 =mations1 c>ry+ m>9e fossils repres5t+ c]ta9 def9ite portions ( geologic "t1 are f\nd at v>i\s altitudes up to sev]al miles 9 _m p>ts ( ! _w1 %[s t ! l& 9 ^? places has really ris5 relative to sea level4 ,x %\ld n be presum$ f ! above discussion t ! sea level itself has nev] *ang$4 ,?us1 ! va/ areas ( ?ick ice %eets 9 bo? ,nor? ,am]ica & ,europe dur+ ! ,great ,ice ,age repres5t$ suffici5t wat] )drawn f ! sea to v appreciably l[] its level4 ,all l&-d]iv$ mat]ials1 c>ri$ into ! sea ma9ly by riv]s1 displace sea wat]1 ) consequ5t rise ( its level4 ,if all exi/+ l&s 7 worn d[n & c>ri$ into ! sea1 its level w\ld be rais$ "s hundr$s ( feet4 ,subsid5ce ( any "p ( ! ocean bottom w\ld cause a l[]+ ( sea level4 ,!re is a /rong reason to believe t "s su* %ift+s ( sea level h occurr$ dur+ ! va/ lapse ( geologic "t4 ,dur+ c]ta9 p]iods erosion ( ! l& pr$om9at$1 & dur+ o!r p]iods build+ up ( ! l& pr$om9at$1 z po9t$ out 9 ! *apt]s on geologic hi/ory4 ,x is n ?\ght t %ift+ ( sea level has ev] am\nt$ to m ?an a few hundr$ feet1 at lea/ n dur+ ! millions ( ye>s ( ! m cle>ly record$ e>? hi/ory4 ,we h ?us f> consid]$ sl[ upw>d & d[nw>d movem5ts ( ! e>?'s cru/ )\t notable /ructural *anges 9 ! rocks4 ,ano!r type ( cru/al di/urbance causes m or less pr(\nd *anges 9 ! /ructures ( ! rocks !mselves4 ,j h[ ! e>? orig9at$ is a matt] ( unc]ta9ty1 b we c be sure t = _m millions ( ye>s x has be5 a %r9k+ body4 ,! out]1 or cru/al1 portion ( ! e>?1 9 adju/+ itself to ! contract+ int]ior1 has _h _m pressures1 /resses1 & /ra9s set up )9 x4 ,z results ( su* =ces ! rocks at & ne> ! e>?'s surface h 9 v>i\s places1 & at v>i\s times1 be5 brok5 7fault$7 & subject$ to sudd5 movem5ts 7see discussion beyond71 :ile ^? well )9 ! cru/al portion1 t is to say a few miles or m d[n1 h1 9 _m cases1 be5 b5t 7fold$71 or ev5 crumpl$4 ,= ^! reasons ! surface & ne>-surface cru/al portions are call$ ! zone ( fracture1 :ile ! m deeply buri$ portions comprise ! zone ( fl[age4 ,9 ! zone ( fl[age ! rocks1 :]e subject$ to great lat]al pressure1 act l pla/ic mat]ials & !re=e b5d r ?an break1 because ( ! great weight ( ov]ly+ mat]ials4 ,laboratory exp]im5ts h confirm$ ! f9d+s ( geologi/s 9 ?is reg>d4 ,small masses ( rocks prop]ly inclos$ 9 nickel-/eel cyl9d]s h be5 subject$ to sl[ diff]5tial pressures equival5t to ^? :i* obta9 tw5ty to =ty miles )9 ! e>?4 ,"u su* conditions rocks h be5 made to *ange %ape v notably )\t fractur+4 ,bo? geological obs]vations & exp]im5ts h l$ u to conclude t n ev5 small fractures or crevices c rema9 op5 at a dep? great] ?an t5 or twelve miles ev5 9 ! h>de/ rocks4 ,f "t to "t1 dur+ ! long hi/ory ( ! e>?1 =ces ( lat]al pressure h be5 sl[ly ex]t$ along m or less localiz$ zones or belts )9 ! e>?'s cru/1 & ! rocks h be5 de=m$ *iefly by b5d+ or fold+1 especially 9 ^? regions :]e m\nta9s ( ! fold$ type h develop$4 ,movem5ts ( ?is type are consid]$ beyond 9 ! *apt] on m\nta9s4 ,rock folds v>y 9 size f microscopic to miles across1 & !y exhibit _m %apes4 ,plate #g w give ! read] a good idea ( actual rock folds ( common sizes & %apes 9 v>i\s places4 ,fold$ /ructures are mo/ cle>ly disc]nible 9 s$im5t>y rocks1 because ( _! /ratifi$ 7lay]$7 arrangem5t4 ,s9ce folds 9 h>d rocks r>ely1 if ev]1 develop except at a dep? ( "s miles )9 ! e>?1 !y %[ at ! surface only :]e great ?icknesses ( ov]ly+ mat]ials h be5 /ripp$ (f by erosion4 ,illu/ration3 ,fig4 #h4--;,an outcrop ( /ratifi$ cry/all9e lime/one 7or m>ble7 exhibit+ two small %>p folds--a syncl9e on ! left & an anticl9e on ! "r--ne> ,l5ox1 ,mass1 ,^! folds develop$ dur+ ! great m\nta9-mak+ di/urbance at ! end ( ! ,ordovician p]iod fully #bj1jjj1jjj ye>s ago4 7,aft] ,dale1 ,u4 ,s4 ,geological ,survey47 ,f ! /&po9t ( our consid]ation ( sl[ e>?-cru/ movem5ts1 x is important to be> 9 m9d t lat]al pressure 9 ! zone ( fl[age has n only notably de=m$ rocks1 b t1 z a result ( ! buckl+ =ces1 giv5 rock masses h1 9 _m cases1 be5 notably %ift$ d[nw>d or upw>d--ma9ly upw>d--f _! orig9al positions4 ,fold$ /rata c>ry+ %ells ( sea animals are commonly f\nd ?\s&s ( feet above sea level 9 _m ( ! great m\nta9 ranges ( ! _w4 ,dur+ ! process ( fold+ on a l>ge scale ! cru/ ( ! e>? is v appreciably %ort5$ at "r angles to ! direction ( appli$ pressure1 due to squeez+ or b5d+ ( ! /rata4 ,9 ! case ( ! ,appala*ian m\nta9s ( ,p5nsylvania x has be5 e/imat$ t su* %ort5+ am\nts to ab\t tw5ty-six miles or1 9 o!r words1 t ! /rata orig9ally spread out horizontally across an area ^: wid? 0 ab\t #ajj miles h be5 squeez$ or fold$ into an area ^: wid? is tw5ty-six miles less4 ,illu/ration3 ,fig4 #i4--,/ructure section %[+ ! pr(ile ( ! m\nta9s & relations ( rocks bel[ ! surface ne> ,liv+/on1 ,montana4 ,! /rata 7 cr[d$ toge!r until !y b5t into great %>ply def9$ folds at ! "t ( ! ,rocky ,m\nta9 ,revolution sev]al million ye>s ago4 ,!n ! rocks broke along ! fault fracture & ! mass on ! "r 0 %ov$ ov] ^u ! mass on ! left4 7,aft] ,u4 ,s4 ,geological ,survey47 ,we %all n[ turn to a consid]ation ( sudd5 e>? movem5ts & "s ( _! effects1 includ+ e>?quakes4 ,m5tion has already be5 made ( ! fact t1 :5 pressures & /ra9s are set up 9 ! out] portion 7zone ( fracture7 ( ! e>?'s cru/1 ! rocks yield ma9ly by break+ or fractur+ because ! rocks n be+ "u a great load ( ov]ly+ mat]ial are !re brittle4 ,! e>?'s cru/ has be5 fractur$ on small & l>ge scales 9 _m places dur+ ! long space ( geologic "t4 ,:]e "o block ( e>?'s cru/ has slipp$ or mov$ pa/ ano!r along a fracture we h :at is call$ a fault4 ,su* displacem5ts ( rock masses v>y 9 am\nt f less ?an an in* to "s miles1 & !y con/itute "o ( ! mo/ important features ( ! ar*itecture ( ! out] portion ( ! e>?4 ,!re are two types ( faults fundam5tally diff]5t z to cause4 ,9 "o type 7s-call$ normal fault7 ! rocks sudd5ly yield to a =ce ( t5sion2 a fracture develops & ! e>? block on "o side ( ! fracture or fault drops ) ref]5ce to t on ! o!r4 ,9 ! o!r type 7s-call$ ?ru/ faults7 ! rocks yield sudd5ly to a =ce ( compression or lat]al ?ru/1 & "o block ( e>? is pu%$ or ?ru/ p>tly ov] ano!r along ! surface ( fracture or fault4 7,see ,plate #h47 ,faults range 9 l5g? up to hundr$s ( miles1 ^? f "o to tw5ty miles 9 l5g? be+ v common4 ,:]e an e>? block has be5 displac$ ?\s&s ( feet along a fault surface1 x is n to be und]/ood t ! :ole displacem5t result$ f a s+le movem5t1 b r f a s]ies ( sudd5 movem5ts sep>at$ by great] or less int]vals ( "t4 ,ea* sudd5 movem5t along a fault surface produces a vibration ( ! e>? ne> by4 ,_m su* sudd5 movem5ts are kn[n to h caus$ viol5t e>?quakes4 ,displacem5ts ( tw5ty to fifty feet1 z a result ( s+le movem5ts1 are def9itely kn[n to h tak5 place 9 v>i\s regions dur+ ! la/ fifty ye>s2 & r>ely1 if ev]1 has any sudd5 displacem5t ( z mu* z sev]al hundr$ feet occurr$4 ,cliffs & /eep slopes v commonly result f fault+1 b1 because ( ! long lapse ( "t requir$ = ! repeat$ movem5ts 9 ! case ( great faults1 ! cliffs or /eep slopes beg9 to we> back & become m or less subdu$ long be=e ! la/ ( ! movem5ts take place4 ,9 regions :]e movem5ts along great faults h long s9ce ceas$1 ! orig9al /eep slopes may be completely oblit]at$ by erosion4 ,illu/ration3 ,fig4 #aj4--,v]tical sections ?r\gh /rata illu/rat+ common k9ds ( faults3 a1 normal faults :]e "o mass simply s9ks bel[ ano!r2 b1 a ?ru/ fault :]e "o mass is %ov$ ov] ano!r4 7,aft] ,u4 ,s4 ,geological ,survey47 ,h[ does ! geologi/ det]m9e ! actual am\nt ( displacem5t1 especially 9 ! case ( a l>ge fault 9 /ratifi$ rocks8 ,fir/1 ! v>i\s =mations ( ! region1 :]e unaffect$ by fault+1 are c>efully /udi$1 especially 9 reg>d to ! "* & ?ickness ( ea*1 & _! relative geologic ages or normal ord] z !y 7 deposit$ "o lay] above ! o!r4 ,!n1 9 ! simple case ( a normal-fault surface at "r angles to horizontal /rata1 x is only necess>y to f9d out :at two =mations or p>ts ( =mations come toge!r along ! fault fracture1 & ! actual am\nt ( displacem5t is readily det]m9$4 ,:]e /rata & normal fault surfaces lie at v>i\s angles1 & also 9 ?ru/ faults1 ^? angles mu/ be det]m9$ 9 addition to ! data above nam$4 ,9 _m m9+ regions1 :]e valuable deposits are affect$ by fault+1 accurate k ( ! direction & am\nt ( displacem5ts ( faults is ( great economic importance4 ,a few examples ( normal faults f well-kn[n di/ricts w n[ be briefly describ$4 ,! :ole ea/]n front ( ! c5tral & s\!rn ,si]ra ,nevada ,range ( ,cali=nia is a great1 /eep fault slope1 f a few ?\s& to t5 ?\s& or m feet high & hundr$s ( miles long1 ( su* rec5t geologic age t x has be5 only mod]ately affect$ by erosion4 ,9 fact1 x is well kn[n t ! s\!rn two-?irds ( ! range is a great tilt$ fault block1 ! total displacem5t hav+ result$ f repeat$ sudd5 movem5ts s9ce ab\t ! middle ( ! pres5t geologic era4 ,a great fault also ext5ds along ! ea/]n base ( ! great ,wasat* ,range ( ,utah & ! /eep slope ?\s&s ( feet high is a fault sc>p only slightly modifi$ by erosion4 ,r5ew$ movem5ts along ?is pr(\nd fault h v rec5tly tak5 place z prov$ by ! pres5ce ( fre% fault sc>ps 9 loose deposits :i* h accumulat$ across ! m\?s ( "s ( ! canyons1 z1 = example1 ne> ,ogd54 ,9 fact1 practically all ( ! nor?-s\? ranges ( ! ,great ,bas9 f ,utah to ,cali=nia are ess5tially a s]ies ( tilt$ fault blocks4 ,ano!r great fault1 less conspicu\s f ! topographic /&po9t1 is hundr$s ( miles long 9 ! ,coa/ ,range ,m\nta9s ( ,cali=nia4 ,at ! "t ( ! ,san ,francisco e>?quake ( #aijf !re 0 a r5ew$ sudd5 movem5t along ?is great fracture4 ,! ea/]n "o-half ( ! ,adirondack ,m\nta9s ( ,new ,york is lit]ally a mosaic ( hundr$s ( fault blocks4 ,_m ( ^! faults are f two to ?irty miles long & !y commonly %[ displacem5ts ( f a few hundr$ to #b1jjj or m feet4 ,a glance at ! geological map 79 colors7 ( ! vic9ity ( ! great copp] m9es at ,bisbee1 ,arizona1 %[s mo/ ( t region to conta9 a network ( normal faults :i* sep>ate x into a mosaic ( fault blocks4 ,9 ea* ( ! examples ( faults j giv5 a block ( e>? has sunk relative to ! o!r1 or 9 o!r words1 ea* is a normal fault4 ,we %all n[ turn to "s l>ge scale cases ( faults 9 :i* great masses ( e>? h be5 pu%$ "o ov] ano!r--s-call$ ?ru/ faults4 ,9 ! s\!rn ,appala*ian ,range1 & especially well exhibit$ 9 ! vic9ity ( ,rome1 ,georgia1 "o portion ( ! m\nta9 mass has lit]ally be5 %ov$ ov] ano!r1 at a l[ angle ov] a fault surface _m miles long1 = fully sev5 miles we/w>d4 ,bo? ! trem5d\s weight ( rock mat]ial actually translat$ & ! numb] ( sudd5 movem5ts requir$ 9 ! op]ation /agg] ! imag9ation4 ,x is safe to say t dur+ ! long "t ( ?is great op]ation viol5t e>?quakes 7 n uncommon4 ,9 ! ,rocky ,m\nta9s ( ! nor!rn ,unit$ ,/ates & s\!rn ,canada !re is ! greate/ kn[n ?ru/ fault on ! cont95t4 ,x is hundr$s ( miles long1 & ! actual displacem5t is commonly at lea/ sev]al miles4 ,9 ! ,glaci] ,national ,p>k ( ,montana x has be5 e/abli%$ t ! front range portion ( ! ,rockies has actually be5 pu%$ at lea/ sev5 miles1 & possibly z mu* z tw5ty miles1 ea/w>d ov] a fault surface1 & out ^u ! ,great ,pla9s4 ,9 "s cases rocks ( ! ,prepaleozoic ,age h !re be5 pu%$ ^u rocks ( ! late ,mesozoic ,age1 ?us locally upsett+ ! geologic column4 ,illu/ration3 ,fig4 #aa4--;,ea/-we/ pr(ile & v]tical /ructure sections fifty-two miles long 9 ! ,mohawk ,valley region ( ,new ,york1 %[+ num]\s tilt$ fault blocks :i* notably influ5ce ! topography4 ,v]tical scale exagg]at$4 ,! rocks are ,prepaleozoic & e>ly ,paleozoic 9 age4 7,modifi$ by ! au?or aft] ,d>ton1 ,new ,york ,/ate ,museum47 ,! ,wasat* ,range ( ,utah1 9 addition to ! great normal fault along its we/]n base1 conta9s a rem>kable sy/em ( ?ru/ faults4 ,9 ! region n[ occupi$ by ! ,wasat* ,m\nta9s a numb] ( p>allel 7?ru/7 faults 7 develop$ close toge!r & ! brok5 pieces ( ! e>?'s cru/ betwe5 !m 7 pu%$ up1 ! rocks on "o side ( ea* crack rid+ up ov] ^? on ! o!r side until a great m\nta9 range 0 =m$ :]e once lay a pla94 ,9 ! ,ogd5 ,canyon "o great e>? block ( ,prepaleozoic 7,algonkian7 ,age has be5 %ov$ ?\s&s ( feet ov] late ,paleozoic 7,c>bonif]\s7 rock1 :i* latt] has 9 turn be5 ?ru/ ov] e>ly ,paleozoic 7,cambrian7 rock4 ,?is ?ru/ fault+ 0 accompli%$ be=e ! developm5t ( ! geologically rec5t normal fault along ! we/]n base ( ! range4 ,illu/ration3 ,fig4 #ab4--,v]tical 7/ructure7 section ?r\gh a "p ( ! e>?'s cru/ sev]al miles long 9 ,ogd5 ,canyon1 ,utah1 %[+ ! sy/em ( great ?ru/ faults4 ,prepaleozoic 7,algonkian7 rocks h be5 pu%$ f> ov] ^u late ,paleozoic 7,c>bonif]\s7 /rata1 :i* latt] h 9 turn be5 %ov$ ov] e>ly ,paleozoic 7,cambrian7 /rata1 etc4 7,aft] ,u4 ,s4 ,geological ,survey47 ,any sudd5 movem5t ( "p ( ! cru/ ( ! e>?1 due to a natural cause1 produces a trembl+ or %ak+ call$ an e>?quake4 ,?\gh e>?quakes are g5]ally class$ among ! mo/ t]rify+ ( all natural ph5om5a1 ^? :i* h occurr$ dur+ human hi/oric times h _h sc>cely any geological or topographical effects ( real consequ5ce on ! face ( ! e>?4 ,locally1 ! effects may be notable & ! de/ruction ( life & prop]ty may be great4 ,! e>? may be locally crack$ & r5t1 small fault sc>ps may develop1 l&slides & avalan*es may result f ! %ak+ ( ! e>?1 build+s may be demoli%$1 & sea waves may be roll$ ^u ! l&4 ,on ! o!r h&1 _m e>?quakes1 call$ tremors1 are too slight to be notic$ by p1 ?\gh !y are record$ by specially con/ruct$ in/rum5ts call$ seismographs4 ,we h already /at$ t actual sudd5 displacem5ts caus+ e>?quakes h am\nt$ to tw5ty or ev5 fifty feet "r along fault fractures1 b dur+ ! vibrations or quak+s1 :i* are (t5 s de/ructively s5t out into ! neighbor+ c\ntry1 ! e>?'s surface r>ely actually moves m ?an a small fraction ( an in*4 ,because ( ! sudd5ness ( ! movem5t objects on ! surface may be mov$ in*es or ev5 feet4 ,viol5t %ocks may la/ "o or two m9utes & cause ! :ole e>? to tremble1 ?\gh at di/ant po9ts only seismographs record ! movem5t4 ,x is probably true t "s "p ( ! e>? is %ak+ all ! "t4 ,/udies dur+ ! la/ fifty ye>s h made x c]ta9 t ! ma9 cause ( e>?quakes is ! sudd5 slipp+ ( e>? blocks pa/ ea* o!r along fault fractures1 ! sudd5 slipp+ furni%+ ! impulse :i* s5ds out ! vibrations into ! surr\nd+ m or less ela/ic cru/ ( ! e>?4 ,! l[ rumbl+ to ro>+ s\nd1 :i* sometimes imm$iately prec$es an e>?quake1 is probably due to ! gr9d+ ( ! rocks toge!r bel[ ! surface4 ,e>?quakes g5]ally accompany volcanic outbur/s ( ! viol5t or explosive type1 & 9 su* cases subt]ranean explosions cause bo? ! eruptions & ! quak+s ( ! e>?4 ,x is well kn[n t ! pr9cipal volcanic di/ricts or belts ( ! e>? are also ! belts ( mo/ frequ5t e>?quakes1 b ?is does n mean t volcanic action causes mo/ ( ! e>?quakes4 ,active volcanoes & e>?quakes are s commonly associat$ 9 ! same belts because ^? belts no d\bt repres5t portions ( ! cru/ :i* are n[ mo/ actively yield+ to ! =ces directly result+ f ! %r9kage ( ! e>?4 ,)9 ! volcanic belts _m e>?quakes take place unaccompani$ by any volcanic action1 & _m o!rs take place f> f volcanoes4 ,"s e>?quakes h be5 caus$ by ! impact ( great l&slides or avalan*es1 or by ! sudd5 cav+ 9 ( und]gr\nd op5+s4 ,brief descriptions ( a few typical c>efully /udi$ e>?quakes dur+ rec5t ye>s w s]ve to make ! ma9 features ( e>?quakes /ill cle>] to ! read]4 ,! viol5t ,japanese e>?quake ( #ahia 0 caus$ by ! s9k+ ( a block ( e>? =ty miles long f two to ?irty feet bel[ t on ! o!r side ( a fault fracture4 ,!re 0 also consid]able horizontal %ift+1 & cracks develop$ 9 ! adjac5t region4 ,a di/9ct fault sc>p1 fifte5 to tw5ty feet high1 develop$1 & 9 "s cases ext5d$ "r across cultivat$ fields4 ,illu/ration3 ,fig4 #ac4--,map ( ! ,unit$ ,/ates1 %[+ ! l>ge areas ov] :i* ?ree ( ! greate/ ( our e>?quakes 7 actually felt by p4 ,^! e>?quakes 7 record$ 9 _m p>ts ( ! _w by delicate in/rum5ts3 ,new ,madrid1 #ahaa2 ,*>le/on1 #ahhf2 ,san ,francisco1 #aijf4 ,illu/ration3 ,fig4 #ad4--,sket* map %[+ ! trace ( ! great fault fracture along :i* a r5ew$ sudd5 movem5t ( z mu* z tw5ty feet took place to cause ! ,san ,francisco e>?quake ( #aijf4 7,aft] ,u4 ,s4 ,geological ,survey47 ,! ,san ,francisco e>?quake ( #aijf 0 produc$ by r5ew$ movem5t along ! great fault :i* ext5ds l5g?wise ?r\gh ! ,coa/ ,range ,m\nta9s = sev]al hundr$ miles4 ,x is lit]ally correct to say t1 = #bej miles along ?is great e>? fracture1 "o "p ( ! ,coa/ ,range in/antane\sly slipp$ f two to tw5ty-two feet pa/ ! o!r4 ,m or less ( ! movem5t ext5d$ at lea/ sev]al ?\s& feet d[n into ! e>?4 ,9 ?is case bo? sides slipp$ & ! movem5t 0 v l>gely horizontal r ?an v]tical4 ,! l& on ! ea/ side ( ! fault mov$ s\? & t on ! we/ side mov$ nor?1 ! am\nt dim9i%+ away f ! fault on ea* side s t "s miles out ! actual cru/al movem5t 0 only a few in*es4 ,:5 "o ?9ks ( ! trem5d\s volumes ( e>? mat]ial involv$ 9 ?is %ift+ ( ! e>?'s cru/1 is x any wond] t su* de/ructive e>?quake waves 7 produc$8 ,_m build+s 7 wreck$1 sev]al hundr$ p 7 kill$1 ! disa/r\s ,san ,francisco fire result$1 wat] ma9s 7 brok51 & f5ces & roads cross$ by ! fault 7 dislocat$ z mu* z fifte5 to tw5ty feet4 ,illu/ration3 ,plate #e4--,swift ,curr5t ,valley 9 ,glaci] ,national ,p>k1 ,montana4 ,?is 0 once a deep ,v-%ap$ canyon c>v$ out 7erod$7 by /ream action4 ,!n a great valley glaci] sl[ly pl[$ its way ?r\gh x dur+ ! ,ice ,age &1 by ice erosion1 ! pres5t ne>ly /raight ,u-%ap$ canyon has result$4 7,photo by ,campbell1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #f4--,view 9 ! ,yosemite ,valley f ,ne> ! ,we/]n ,entrance4 ,! great rock call$ ,el ,capitan1 on ! left rises #c1ejj feet above ! riv]1 & ,bridal ,veil ,falls on ! "r is #fbj feet high4 ,all ! rock is granite1 ! ne>ly v]tical walls ( :i* h result$ f ! action ( a great glaci] :i* pl[$ its way ?r\gh ! valley dur+ ! ,ice ,age2 ! valley walls h be5 cut back by ! removal ( l>ge v]tical jo9t blocks4 ,! flat bottom ( ! valley has result$ f ! fill+ ) s$im5t ( a po/glacial lake 9 ! valley4 7,photo by ,f4 ,n4 ,kneel&1 ,nor?ampton1 ,mass47 ,dur+ ! great e>?quake on ! coa/ ( ,alaska 9 #ahii notable *anges took place along ! %ore = "s miles1 "o portion hav+ sudd5ly ris5 z mu* z =ty-sev5 feet1 :ile ano!r portion sank bel[ sea level4 ,illu/ration3 ,fig4 #ae4--,map %[+ ! pr9cipal e>?quake regions ( ! _w4 ,9 #ahhf ! e>?quake c5t]+ ne> ,*>le/on1 ,s4 ,c41 0 prec$$ by rumbl+ & ro>+ noises & ! slight quak+ increas$ to viol5t %ak+ :i* la/$ m ?an a m9ute4 ,eight m9utes lat] a r viol5t e>?quake %ock took place1 foll[$ dur+ ! next t5 or twelve h\rs by less sev]e %ocks4 ,mo/ build+s 9 ! city 7 wreck$ or m or less badly damag$1 & "s p 7 kill$4 ,! %ocks 7 s viol5t t ! quak+ 0 actually felt by p ov] an area ( m ?an #b1jjj1jjj squ>e miles1 ! di/urbance hav+ spread at ! rate ( ab\t #aej miles p] m9ute4 ,ne> ,*>le/on op5+s & fissures 7 =m$ ?r\gh :i* s& & muddy wat] 7 eject$1 b ! cause ( ! di/urbance 0 mo/ likely slipp+ ( ! old v h>d rocks bel[ ! loose deposits ( ! ,coa/al ,pla94 ,f #ahaa to #ahac a s]ies ( viol5t e>?quakes develop$ 9 ! g5]al vic9ity ( ,new ,madrid1 ,miss\ri4 ,9 an area ( ov] #b1jjj squ>e miles1 n[ call$ ! sunk c\ntry1 _m portions sudd5ly sank giv+ rise to small fault sc>ps or cliffs1 & v>i\s lake bas9s 7 =m$4 ,developm5t ( a fissure caus$ a local *ange 9 ! c\rse ( ! ,mississippi ,riv]4 ,9 #ahig1 ,assam1 ,india1 0 %ak5 by an e>?quake ( unusual magnitude1 :i* la/$ #b-a_/b m9utes4 ,an area ( #aej1jjj squ>e miles 0 disa/r\sly %ak51 & ! %ocks 7 di/9ctly felt ov] an area ( #gej1jjj squ>e miles4 ,a numb] ( notable fault sc>ps develop$1 ! movem5t on "o hav+ be5 ?irty-five feet4 ,,*apt] ,,viii ,,volcanoes ,,& ,,igne\s ,,rocks ,n only because ( ! great p[] & t]rify+ gr&eur ( viol5t eruptions1 b also because ( _! de/ruction ( life & prop]ty1 volcanoes /& out 9 ! popul> m9d z among ! mo/ real & important ( all geological ph5om5a4 ,b great volcanic outbur/s1 l viol5t e>?quakes1 are 9 tru? only outw>d1 s5sible1 relatively m9or manife/ations ( ! trem5d\s e>?-*ang+ =ces bel[ ! surface4 ,!y are f> less important z geological ag5cies ?an ! mighty int]ior =ces :i* cause p>ts ( cont95ts to be sl[ly uprais$ & ! rocks fold$1 or ev5 ?an ! incessant action ( /reams :]eby ! l&s are cut d[n4 ,ev5 z an igne\s ag5cy1 volcanoes are notably less important ?an ! developm5t & %ift+ ( molt5 mat]ials )9 ! e>?'s cru/4 ,volcanic action is1 h[ev]1 n only conspicu\s1 b x is also ( real significance z a means ( *ang+ ! e>?1 su* action hav+ tak5 place s9ce v e>ly kn[n geologic "t4 ,aft] br++ out ! ma9 facts & pr9ciples ( volcanoes1 aid$ by descriptions ( specific eruptions1 we %all turn to a consid]ation ( igne\s activity )9 ! e>?'s cru/4 ,m\nt ,vesuvius 9 ,italy is p]haps ! mo/ fam\s active volcano 9 ! _w4 ,its eruptions h be5 m or less c>efully /udi$ = a long] "t ?an any o!r4 ,! eruption 9 ! ye> #gi ,a4 ,d4 0 really a trem5d\s explosion caus+ a l>ge "p ( ! old crat] to be bl[n away1 & s5d+ imm5se volumes ( rock fragm5ts1 mo/ly f9ely divid$ 7s-call$ a%es7 into ! air :i* completely buri$ ! small city ( ,pompeii4 ,wat] f ! great cl\ds ( cond5s+ /eam1 mix$ ) a%es1 =m$ muddy floods :i* ov]:elm$ ,h]culaneum4 ,little or no lava 0 erupt$4 ,s9ce t "t ! crat] has be5 m or less active & ! pres5t cone1 #d1jjj feet high1 has be5 built up4 ,dur+ ! la/ fifty ye>s ! greate/ eruptions took place 9 #ahgb & #aijf1 :51 /reams ( molt5 rock fl[$ d[n ! sides ( ! m\nta94 ,illu/ration3 ,fig4 #af4--,map %[+ ! di/ribution ( active & rec5tly active volcanoes ( ! _w4 ,"o ( ! greate/ volcanic explosions ev] record$ 0 t ( ! isl& ( ,krakatoa1 betwe5 ,sumatra & ,java1 9 #ahhc4 ,! great] "p ( ! isl& 0 bl[n away & !re 0 wat] #a1jjj feet deep1 :]e j be=e ! isl& /ood hundr$s ( feet high4 ,ab\t a cubic mile ( rock mat]ial 0 s5t into ! air mo/ly 9 ! =m ( f9e du/--"s ( x = sev5te5 miles--& completely hid ! sun1 caus+ total d>kness dur+ ! eruption4 ,du/ fell ov] an area ( sev]al hundr$ ?\s& squ>e miles4 ,sev]al days aft] ! explosion %ips m ?an #a1jjj miles away 7 du/ cov]$4 ,su* enorm\s quantities ( a light por\s lava call$ pumice fell & float$ ^u ! sea t navigation 0 badly ob/ruct$ _m miles f ! volcano4 ,extremely f9e du/ gradually spread ?r\gh ! :ole e>?'s atmosph]e1 caus+ ! extraord9>y r$ sunsets = sev]al mon?s4 ,! s\nd ( ! explosion 0 he>d = hundr$s ( miles4 ,great sea waves #ej to #ajj feet high 7 /irr$ up & !y swept inl& = sev]al miles ov] ! l[-ly+ coa/ l&s ( neighbor+ ,java & ,sumatra1 ov]:elm+ hundr$s ( villages & dr[n+ t5s ( ?\s&s ( p4 ,illu/ration3 ,fig4 #ag4--,! great hole left aft] ! top ( ,mt4 ,katmai 9 s\!rn ,alaska 0 bl[n (f 9 #aiab by "o ( ! mo/ trem5d\s volcanic explosions 9 ! annals ( human hi/ory4 ,! wat] 9 ! lake is hot4 7,aft] ,griggs1 ,national ,geographic ,magaz9e47 ,"o ( ! greate/ explosions on record 0 t ( ,katmai volcano1 sev]al ?\s& feet high1 on ! coa/ ( ,alaska1 9 ,june1 #aiab4 ,n only 0 ! top ( ! m\nta9 completely bl[n (f1 b also a great crat] pit1 ?ree miles wide across ! top & sev]al ?\s& feet deep1 0 develop$ 9 ! /ump ( ! =m] m\nta94 ,volcanic du/ fell to a dep? ( sev]al feet )9 tw5ty-five to fifty miles ( ! m\nta94 ,du/ accumulat$ to a dep? ( ne>ly a foot 9 ! village ( ,kodiak1 #ajj miles ea/ ( ! m\nta91 :]e total d>kness prevail$ = m ?an two days4 ,a lake ( v hot wat] n[ occupies ! bottom ( ! great new crat]4 ,! noise ( ! explosion 0 he>d = at lea/ #gej miles4 ,illu/ration3 ,fig4 #ah4--;,diagrammatic v]tical or /ructure section ?r\gh a portion ( ! e>? illu/rat+ ! common modes ( occurr5ce ( igne\s rocks4 ,p1 deep-seat$ 7plutonic7 igne\s rock2 ,s1 /rata2 ,d1 dikes2 ,m1 mass ( igne\s rock =c$ betwe5 /rata b5d+ !m upw>d2 ,f1 fe$+ *annel ( volcano2 ,v1 volcano2 ,l1 lava %eets4 7,by ! au?or47 ,"o ( ! mo/ frightful volcanic cata/rophes ( rec5t ye>s 0 ! eruption ( ,mont ,pele1 isl& ( ,m>t9ique1 ,we/ ,indies1 9 #aijb4 ,9 ?is case1 also1 no lava 0 p\r$ out1 b viol5t explosions s5t great cl\ds ( v highly heat$ gases & vapors1 m+l$ ) inc&esc5t du/1 ?\s&s ( feet into ! air4 ,"o ( ^! great cl\ds ru%$ d[n ! m\nta9 at hurricane spe$ & de/roy$ ! city ( ,/4 ,pi]re ) its #cj1jjj inhabitants4 ,aft] ! ma9 eruption a sp9e or core ( h>d rock began to rise out ( ! crat] & x sl[ly grew to a height ( #a1jjj feet 9 sev]al mon?s1 aft] :i* x began to crumble away4 ,?is sp9e probably repres5t$ ne>ly froz5 lava :i* solidifi$ z x 0 gradually =c$ out ( ! m\nta94 ,( special int]e/ to u1 ?\gh n ( great importance is ! only active volcano 9 ! ,unit$ ,/ates4 ,9 ,may1 #aiad1 ,m\nt ,lass5 7or ,lass5 ,peak71 a long inactive volcano 9 nor!rn ,cali=nia1 sudd5ly bur/ =? explosively & dur+ ! next sev]al ye>s hundr$s ( eruptions occurr$4 ,little or no lava appe>$1 b great cl\ds ( /eam & du/ (t5 %ot into ! air f "o to ?ree miles above ! top ( ! m\nta91 :i* lies ov] #aj1jjj feet above sea level4 7,plate #aj47 ,great quantities ( du/ h accumulat$ = miles ar\nd ! m\nta94 ,at ?is writ+ 7,octob]1 #aibj7 ! m\nta9 is aga9 active4 ,x %\ld n be presum$1 h[ev]1 t all1 or ne>ly all1 volcanoes are ( ! explosive type4 ,o!rs ( ! m quiet type are well exemplifi$ by ! two great ,hawaiian volcanoes1 ,mauna ,loa & ,kilauea4 ,any b relatively v m9or explosions r>ely1 if ev]1 occur1 ! product ( su* volcanoes be+ almo/ :olly lava1 :i* fl[s d[n ! m\nta9sides 9 molt5 /reams4 ,! ,hawaiian ,isl&s h1 9 fact1 be5 almo/ entirely built up by successive eruptions ( lava1 ! build+-up process hav+ begun well bel[ sea level4 ,mauna ,loa rises to ne>ly #ad1jjj feet above ! sea1 b1 due to ! fact t ! /reams ( lava h spread s f>1 ! m\nta9 has an exceptionally l[ angle ( slope :i* makes x difficult to realize t x is s high4 ,consid]+ its subm>9e portion1 ,mauna ,loa really rises ne>ly #cj1jjj feet above ! sea floor4 ,al?\gh ,kilauea lies ne>ly #d1jjj feet above sea level on ! flank ( ,mauna ,loa1 & only tw5ty miles di/ant f x1 ! two volcanoes are s+ul>ly indep5d5t 9 reg>d to _! eruptions4 ,ea* m\nta9 has a crat] irregul>ly oval 9 %ape1 ne>ly ?ree miles long1 b\nd$ by almo/ v]tical walls ( h>d lava1 9 "s cases arrang$ 9 t]races4 ,! floors ( ! great crat] pits are relatively level1 & consi/ ( black lava 9 :i* are lakes ( molt5 & ev5 boil+ lava4 ,! black lava floor is1 9 ea* case1 only a froz5 or h>d5$ cru/ ^u a great column ( molt5 lava ext5d+ d[n into ! m\nta94 ,prior to an eruption ( ,mauna ,loa ! lava column rises hundr$s ( feet 9 ! crat]1 b dur+ rec5t ye>s ! lava seldom1 if ev]1 fl[s out ov] ! crat] rim4 ,in/ead1 x breaks ?r\gh ! m\nta9sides at v>i\s altitudes1 ! great fl[ ( #aiai hav+ />t$ at an altitude ( ab\t #h1jjj feet4 ,?is /ream ( liquid rock1 fully "o-half ( a mile wide1 fl[$ = weeks d[n ! m\nta9side & into ! ocean1 ! wat]s ( :i*1 9 contact ) ! highly heat$ lava1 7 ?r[n into t]rific commotion4 ,9 #ahhe a /ream ( lava sev]al miles wide fl[$ =ty-five miles4 ,9 "o case1 lava travel$ ! fir/ fifte5 miles 9 two h\rs1 b ?is is an unusually great rate ( spe$4 ,lava /reams 9 g5]al seldom move fa/] ?an "o or two miles p] h\r1 & z ! liquid rock gradually cools & becomes m & m visc\s1 ! spe$ dim9i%es to z]o4 ,almo/ incr$ible volumes ( /eam emanate f /reams ( molt5 lava4 ,9 #ahdj an outfl[ ( lava took place f ! side ( ,kilauea ,m\nta9 & ran into ! sea4 ,s9ce t "t ! floor ( ! great crat] pit 7quot+ ,pr(essor ,w4 ,h4 ,hobbs7 has be5 ess5tially a movable plat=m ( froz5 lava ( unkn[n & d\btless v>iable ?ickness :i* has ris5 & desc5d$ 7hundr$s ( feet7 l ! floor ( an elevator c> betwe5 its guid+ ways4 ,! floor has1 h[ev]1 nev] be5 complete1 = "o or m op5 lakes are always to be se51 t ( ,halemaumau1 locat$ ne> ! s\?we/]n m>g91 hav+ be5 mu* ! mo/ p]si/5t4 ,)9 ! op5 lakes ! boil+ lava is app>5tly :ite hot at a dep? ( b a few in*es bel[ ! surface1 & 9 ! ov]turn+s ( ! mass ^! hott] portions are br\ght to ! surface & appe> z :ite /reaks m>k+ ! r$d] surface portions4 ,f "t to "t ! surface freezes ov]1 ! cracks op5 & erupt at favor$ po9ts along ! fissures1 s5d+ up jets & f\nta9s ( lava1 ! mat]ial ( :i* falls 9 pa/y fragm5ts t build up driblet cones4 ,small fluid clots are %ot out1 c>ry+ ?readlike l9es ( lava glass beh9d !m1 ! well-kn[n ',pele's hair4' ,sometimes ! op5 lakes build up congeal$ walls1 ris+ above ! g5]al level ( ! pit1 & f _! rim ! lava spills ov] 9 cascades to spread out ^u ! froz5 floor4 ,9 "s regions1 l ! ,columbian ,plateau ( ! nor?we/]n ,unit$ ,/ates & ! ,deccan ( ,india1 ea* cov]+ ab\t #bjj1jjj squ>e miles1 va/ quantities ( lava h be5 p\r$ out lay] ^u lay] to dep?s ( ev5 ?\s&s ( feet4 ,di/9ct volcanic cones or m\nta9s 9 ^? regions are ei!r abs5t or too sc>ce to look to z s\rces ( s mu* lava4 ,su* lava floods 7 probably mo/ly erupt$ f great fissures 9 ! e>?'s cru/1 ! fluidity to spread _m miles4 ,"s idea ( ! quantitative geological importance ( volcanism may be convey$ to ! read] :5 we ass]t t1 accord+ to a cons]vative e/imate1 fully "o-half ( a million cubic miles ( molt5 rocks h be5 p\r$ out ^u ! surface ( ! e>? ?r\gh volcanic action 9 relatively rec5t geological "t6 ,! ,cascade ,range ) its l(ty peaks1 includ+ ,m\nt ,%a/a & ,m\nt ,ra9i]1 ea* ris+ m ?an #ad1jjj feet above ! sea1 has be5 built up v l>gely by volcanic action dur+ ! la/ era ( geologic "t4 ,_m o!r m\nta9 peaks & v>i\s ranges h be5 simil>ly develop$ ei!r :olly or 9 "p4 ,! great *a9 ( ,aleutian ,isl&s ext5d+ hundr$s ( miles into ! sea1 is ! sc5e ( mu* volcanic activity :]e a great m\nta9 range is n[ lit]ally be+ born out ( ! sea by ! processes ( vulcanism4 ,be=e ?is ! read] has m ?an likely wond]$ ab\t ! s\rce ( ! heat1 vapors 7ma9ly wat]71 & p[] involv$ 9 volcanic action4 ,answ]s to ^! que/ions are closely ti$ up ) ! precise cause 7or causes7 ( volcanic action :i* rema9s "o ( ! mo/ unc]ta9 ( ! l>g] problems ( geologic sci5ce4 ,be=e briefly discuss+ ! causes1 a few additional facts %\ld be /at$4 ,fir/1 9 reg>d to ! heat1 a c>eful det]m9ation ( ! temp]ature ( ! molt5 lava ( ,kilauea 9 #aiaa %[$ x to be #a1bfj degrees ,c5tigrade1 or #b1cjj degrees ,f4 ,?is is1 h[ev]1 a relatively l[ temp]ature1 because _m lavas f o!r regions %[ melt+ po9ts all ! way up to at lea/ #b1jjj degrees ,c5tigrade 7#c1fjj degrees ,f474 ,wat] 9 ! =m ( /eam is quantitatively "o ( ! greate/ products ( volcanoes4 ,a fair idea ( ! trem5d\s volumes ( wat] involv$ may be ga9$ f ! /atem5t t a c>eful e/imate %[s t fully #dfj1jjj1jjj gallons ( wat] 9 ! =m ( /eam erupt$ f a s+le second>y cone ( ,m\nt ,etna dur+ a p]iod ( #ajj days4 ,among o!r gases :i* are giv5 (f 9 great] or less am\nts dur+ volcanic activity are c>bonic acid gas1 sulphuret$ hydrog51 sulphur dioxide1 & hydro*loric acid4 ,"s idea ( ! p[] back ( volcanoes may be ga9$ n only f ! trem5d\s explosions su* z ^? above describ$1 b also f ! fact t ! pressure necess>y to raise ! column ( lava f sea level to ! top ( ,mauna ,loa 7ne>ly #ad1jjj feet7 is ab\t #a1aej atmosph]es1 or ab\t #ag1jjj p\nds p] squ>e in*4 ,! actual pressure mu/ !re be mu* great] because ! lava is =c$ up f f> bel[ sea level4 ,a long-held idea t a relatively ?9 cru/ cov]s a molt5 int]ior1 & t d[nw>d pressure ( ?is cru/ due to e>? contraction causes molt5 rocks to be =c$ out1 has be5 too ?or\ghly disprov$ to n[ be at all s]i\sly ent]ta9$4 ,! fact t ne>-by volcanoes commonly erupt entirely indep5d5tly1 z 9 ! case ( ,mauna ,loa & ,kilauea1 %[s t !re c be no univ]sal liquid b5ea? a relatively ?9 cru/4 ,o!r argum5ts aga9/ liquidity ( ! e>?'s int]ior are t ! e>? acts l a body ne>ly z rigid z /eel aga9/ ! p[]ful tide-produc+ =ces1 & t e>?quake waves :i* pass ?r\gh ! e>? to a dep? ( at lea/ #b1jjj miles are ! k9d :i* require a solid m$ium = transmission4 ,let u !n briefly consid] m plausible views reg>d+ ! cause ( volcanic action4 ,fir/ ( all we may be sure t ! e>? is highly heat$ inside4 ,measurem5ts 9 _m deep bor+s %[ t ! temp]ature increases at ! rate ( ab\t #a degree ,f4 = ea* #ej to #fj feet d[nw>d1 to dep?s great] ?an a mile4 ,accord+ly1 on ! basis ( #a degree rise 9 #ej feet1 at dep?s ( #bj to #ce miles1 ! temp]ature mu/ be great en\gh 7#b1abj degrees to #c1eij degrees ,f471 to cause all ord9>y rocks to melt if !y 7 at ! surface4 ,at su* dep?s1 h[ev]1 ! d[nw>d pressure ^u ! rocks is s great t _! melt+ po9ts are notably rais$1 & !re is e reason to believe t "u ord9>y conditions ! rocks #bj to #ce miles d[n are n molt54 ,if we adh]e to ! old] 7nebul>7 hypo!sis ( e>? orig91 ! int]ior heat ( ! e>? is left ov] f ! cool+1 once molt51 e>?4 ,on ! basis ( ano!r 7planetesimal7 hypo!sis1 ! e>?'s heat is due to ! /eady1 p[]ful action ( gravity caus+ ! e>? to contract4 ,9 any case1 ! e>? is hot inside z prov$ by deep well records & igne\s ph5om5a 9 g5]al1 & x is a contract+ or %r9k+ body z prov$ by ! _m l>ge scale zones ( wr9kl+ or fold+ ( rocks4 ,if1 !n1 highly heat$ solid rocks at reasonable di/ances d[n 9 any "p ( ! e>? are subject$ to relief ( pressure by an e>? movem5t su* z upw>d crumpl+ ( ! cru/1 or by readju/m5t ( l>ge fault blocks1 su* heat$ solid rocks w\ld become molt54 ,! v e>? movem5t :i* br+s ab\t relief ( pressure & melt+ may v reasonably be reg>d$ z ! p[] :i* =ces "s ( ! newly =m$ molt5 mat]ial high] up into ! e>?'s cru/1 & ev5 out ^u ! surface4 ,?is view h>monizes ) ! well-kn[n fact1 already m5tion$1 t ! ma9 belts ( active volcanoes are also ! ma9 belts ( active e>? movem5ts1 su* z e>?quakes4 ,ano!r s\rce ( p[] beh9d volcanic action is /eam pressure4 ,we h already m5tion$ ! fact t va/ am\nts ( wat] 9 ! =m ( /eam escape f volcanoes or ev5 f /reams ( molt5 lava4 ,! viol5t volcanic explosions are q c]ta9ly all1 or ne>ly all1 direct results ( sudd5 giv+ way ( volcanoes to /eam pressure :i* accumulates dur+ great] or less p]iods ( "t1 & ) little or no possibility ( escape1 )\t ruptur+ ! m\nta94 ,/eam alone1 or comb9$ ) "s ( ! o!r gases s common z volcanic products1 may also aid 9 =c+ out molt5 rock4 ,:at is ! s\rce ( ! /eam & o!r gases or vapors8 ,accord+ to "o view !y 7 orig9ally 9 ! e>?1 :ile accord+ to ano!r view ! wat] at lea/ has be5 absorb$ by ! molt5 rocks f surface wat]s :i* work$ _! way d[nw>d4 ,at lea/ two argum5ts oppose ! second hypo!sis3 fir/1 t n a few volcanoes are really _m miles f ! sea or o!r bodies ( wat]1 :ile d[nw>d p]colation ( ra9 wat] w\ld fall f> %ort ( supply+ ! trem5d\s quantities ( wat] eject$1 & second1 any wat] tak5 up by molt5 rock mu/ be absorb$ )9 a v few miles ( ! surface because1 z we h le>n$1 f>!r d[n !re are no op5+s l>ge en\gh to p]mit ! d[nw>d passage ( wat]1 b1 z a matt] ( fact1 ! v upp] "p ( ! e>?'s cru/ is j ! place :]e molt5 rocks beg9 to give up _! wat]1 (t5 ) t]rific viol5ce4 ,we may n[ turn to a consid]ation ( ! o!r v important k9d ( igne\s activity1 namely1 ! rise & transf] ( molt5 mat]ials )9 ! e>?'s cru/1 b n to ! surface4 ,! quantity ( su* deep-seat$ 7s-call$ plutonic7 igne\s rock mat]ial :i* has be5 intrud$ into ! e>?'s cru/ )9 kn[n geologic "t1 is f> great] ?an t :i* has be5 =c$ to surface1 t is ! s-call$ volcanic mat]ial4 ,! plutonic rocks are always ?or\ghly cry/alliz$1 & !y are g5]ally co>s] gra9$ ?an ! volcanic rocks4 ,:]e molt5 mat]ials h be5 =c$ into cracks or fissures 9 ! cru/ ( ! e>? & !re congeal$1 we h a v common mode ( occurr5ce call$ dikes 7,plate #i74 ,9 _m regions (t5 "o set ( dikes 0 =m$1 aft] :i* "o or m succe$+ injections f ! same or diff]5t deep-seat$ bodies ( molt5 rock took place1 & "s ( ! lat] dikes 7 =c$ to cut across e>li] ones4 ,dikes ( all l5g?s up to at lea/ ?irty miles1 & ( all wid?s up to _m hundr$s ( feet1 are kn[n1 b !y are g5]ally less ?an a mile long & n m ?an a few feet or rods wide4 ,!y h be5 intrud$ into all k9ds ( rock =mations--igne\s1 s$im5t>y1 & metamorphic4 ,dikes are common 9 _m p>ts ( ! _w & !y (t5 excite ! int]e/ ( lay-m54 ,!y are wond]fully display$ along ! s\!rn coa/ ( ,ma9e4 ,plate #i %[s small dikes :]e ! molt5 mat]ial 0 =c$ f a l>g] mass into a body ( old] d>k rock4 ,! ,palisades ( ! ,hudson ,riv]1 j nor? ( ,new ,york ,city1 consi/s ( a lay] ( igne\s rock sev]al hundr$ feet ?ick :i*1 9 ! molt5 condition1 0 =c$ ne>ly horizontally betwe5 lay]s ( s&/one millions ( ye>s ago1 t is 9 ! e>ly ,mesozoic era4 ,! palisade or column> /ructure 0 caus$ by crack+ ( ! rock dur+ ! cool+ & contraction4 ,?is is ! explanation ( mo/ column> /ructures ( igne\s rocks1 exceptionally f9e exhibitions be+ at ! ,giant's ,causeway 9 ,irel&1 & ,devil's ,t[]1 ,wyom+ 7,plate #aj74 ,a type ( occurr5ce n s common1 b ( special int]e/1 is :]e a body ( molt5 rock ris+ 9 ne>ly horizontal /rata becomes cool] & !re=e /iff] or m visc\s &1 los+ its p[] to p5etrate1 =ces its way betwe5 ! lay]s caus+ ! /rata to be ar*$ or dom$ ov] x4 ,suffici5t removal ( ov]ly+ mat]ial by erosion has reveal$ _m f9e examples ( ?is type ( occurr5ce4 ,ano!r type ( int]e/ is ! volcanic neck1 :i* is ! core or plug fill+ ! fe$+ *annel ( a volcano4 ,9 c]ta9 regions1 l p>ts ( ,arizona & ,new ,mexico1 ext9ct volcanic m\nta9s may be all cut away by erosion1 except ! c5tral cores or necks :i*1 bo? because !y are m resi/ant & are la/ to be rea*$ by erosion1 /& out conspicu\sly z great t[]s on ! l&scape 7,plate #i74 ,mo/ important ( all f ! quantitative /&po9t1 h[ev]1 are ! great bodies ( igne\s rocks1 rang+ up to _m miles across1 :i*1 9 a molt5 condition1 7 =c$ irregul>ly into ! e>?'s cru/ f unkn[n dep?s4 ,! common rock call$ granite belongs 9 ?is category ( rocks1 :i* are ! be/ & mo/ ext5sively develop$ ( all igne\s types4 ,! roots or cores ( great m\nta9 ranges (t5 consi/ ( su* rocks :i* are expos$ to view only aft] removal ( great ?ickness ( ov]ly+ mat]ial4 ,imm5se areas ( granite & o!r plutonic rocks ( extra deep-seat$ orig9 are expos$1 because ( removal ( ov]ly+ mat]ial by erosion1 9 s\!a/]n ,canada1 ! ,adirondack ,m\nta9s1 ,new ,engl&1 ! ,pi$mont ,plateau ( ! ,atlantic ,coa/1 & 9 ! ,si]ra ,nevada ,m\nta9s4 ,all ! rock =m+ ! l(ty walls ( ,yosemite ,valley is granite1 :i* 0 =c$ into ! e>?'s cru/ 9 relatively late ,mesozoic "t1 & :i* has s9ce be5 laid b>e by erosion4 ,,*apt] ,,ix ,,wat]s ,,)9 ,,! ,,e>? ,x has be5 e/imat$ t approximately #a1ejj cubic miles ( wat] fall ^u ! surface ( ! ,unit$ ,/ates ea* ye>4 ,ab\t "o-half ( ?is goes back into ! atmosph]e by evaporation2 ab\t "o-?ird ( x fl[s away 9 surface /reams2 & ! rema9+ "o-six? ent]s ! cru/ ( ! e>?4 ,consid]able wat] :i* ent]s ! e>? returns to ! surface z spr+s1 by capill>ity ( soils & rocks1 or by be+ drawn up into plants & evaporat$4 ,"s idea ( ! am\nt ( gr\nd wat] may be glean$ f ! /atem5t1 bas$ ^u a c>eful e/imate1 t all ! wat] 9 ! rocks & soils ( ! fir/ #ajj feet bel[ ! surface ( ! ,unit$ ,/ates w\ld make a lay] sev5te5 feet ?ick4 ,9 mo/ humid regions ! soils & loose rock =mations are saturat$ ) wat] at great] or less dep?s 7usually less ?an #ajj feet7 bel[ ! surface4 ,! surface ( ?is saturat$ lay] is call$ ! gr\nd-wat] level1 or m famili>ly ! wat] table4 ,! wat] table %ifts up & d[n m or less accord+ to v>iation 9 ra9fall4 ,9 addition to ! wat] held 9 ! loose rocks & soils ne> ! e>?'s surface1 l>ge quantities occur 9 def9ite lay]s 7usually /rata7 ( por\s rocks :i* v commonly ext5d at v>i\s angles1 hundr$s or ev5 ?\s&s ( feet into ! e>?4 ,a v f9e illu/ration ( ?is pr9ciple is ! case ( ! ,dakota s&/one =mation ( ,nebraska4 ,almo/ any:]e across ! ,/ate a well drill$ ?r\gh a b$ ( clay & into ! por\s s&/one lay] enc\nt]s wat]4 7,figure #ai47 ,ano!r pr9ciple is also well illu/rat$1 namely1 t wat] 9 su* a por\s lay] may actually travel hundr$s ( miles1 wat] obta9$ f a well sunk to ! ,dakota s&/one hav+ actually travel$ "u ! surface ( ! ,/ate all ! way f ! ea/]n face ( ! ,rocky ,m\nta9s1 :]e ra9 & melt+ sn[ ent]$ ! upturn$ & expos$ por\s rock lay]4 ,ano!r good example is ,i[a1 :]e c]ta9 por\s rock lay]s outcropp+ 9 ! nor?we/]n & nor!a/]n corn]s ( t & adjac5t ,/ates gradually b5d d[n "u ! ,/ate1 rea*+ ! greate/ dep?s 7up to #c1jjj feet7 f> 9 ! int]ior4 ,f wells #c1jjj feet deep ne> ,boone1 ,i[a1 x is1 !re=e1 a fact t "s ( ! wat] pump$ out ( ! e>? actually travel$ und]gr\nd all ! way f beyond ! corn]s ( ! ,/ate4 ,?is sort ( travel ( und]gr\nd wat] is common 9 _m p>ts ( ! _w4 ,x %\ld be cle>ly und]/ood t su* wat] does n fl[ freely z 9 a pipe along subt]ranean passageways1 b r x sl[ly works its way betwe5 ! gra9s ( por\s rock4 ,:]e su* wat] moves di/9ctly d[nw>d1 & ! por\s lay] has bo? above & bel[ x an imp]vi\s rock lay] l %ale or clay1 x gradually gets "u great] & great] pressure4 ,9 "s cases su* pressure has actually be5 f\nd by deep drill+ to be equival5t to t ( a column ( wat] sev]al ?\s& feet high4 ,! rate ( motion ( wat] 9 por\s und]gr\nd rock lay]s is v sl[1 data f v>i\s s\rces indicat+ a rate ( spe$ ( n m ?an "o-fif? ( a mile a ye> 9 co>se por\s s&/one1 :ile 9 _m rocks x _c be m ?an t5 to fifty feet p] ye>4 ,illu/ration3 ,fig4 #ai4--,v]tical 7/ructure7 section f ! ,rocky ,m\nta9s to ,omaha1 ,nebraska1 illu/rat+ a widespread und]gr\nd por\s rock lay] 7! ,dakota s&/one7 *>g$ ) wat] "u pressure1 ! clay =mation act+ z a cap rock4 7,aft] ,d>ton1 ,u4 ,s4 ,geological ,survey47 ,we /ill h to consid] a ?ird mode ( occurr5ce ( wat]s )9 ! e>?4 ,_m =mations1 l granite & o!r types ( cry/all9e rocks are nei!r 9 def9ite lay]s1 nor are !y suffici5tly por\s to all[ wat] to really fl[ ?r\gh !m4 ,:]e su* rocks ext5d f> d[n f or ne> ! surface1 h[ does ra9 wat] desc5d8 ,x does s along cracks or fractures 7bo? jo9ts & faults7 :i* we h le>n$ are almo/ univ]sally abundantly pres5t 9 all h>d rocks 9 ! upp] 7or zone ( fracture7 portion ( ! e>?'s cru/4 ,jo9t cracks are g5]ally v irregul> 9 direction & spac+1 :ile fault fractures are usually fairly regul> & /raight4 ,_m cracks are n wide en\gh to all[ any?+ l good passageways = wat]1 :ile o!rs are suffici5tly op5 to all[ wat] to travel along !m = hundr$s1 or ev5 ?\s&s ( feet4 ,9 canyons ( ! ,we/1 spr+s n r>ely em]ge f ! bottoms ( great1 ne>ly v]tical l$ges ( granite & o!r h>d cry/all9e rocks1 ! wat]s c]ta9ly hav+ ent]$ ! rocks hundr$s1 or ev5 "s ?\s&s ( feet1 high]4 ,9 rocks ( ! k9d "h consid]$ x is evid5t1 !n1 t ! movem5ts ( subt]ranean wat]s mu/ be mo/ly exce$+ly irregul> & usually n 9 great quantities4 ,9 _m deep m9es ( ! _w1 und]gr\nd wat] causes little or no tr\ble except (t5 ne> ! surface4 ,occasionally a %aft or tunnel /rikes a prom95t jo9t or fault fracture fill$ ) wat]4 ,:at we might really call und]gr\nd /reams may occur only "u exceptional conditions 9 rocks o!r ?an lime/one1 b 9 lime/one !y are n uncommon because ! sl[ solubility ( ! rock all[s und]gr\nd wat]s to sl[ly enl>ge ! passageways to =m di/9ct *annels4 ,e*o ,riv]1 :i* fl[s ?r\gh ,mammo? ,cave1 is a f9e case 9 po9t4 ,mo/ wat] by f> :i* em]ges z spr+s1 0 at "o "t surface wat]4 ,a simple1 b common case is :]e ra9 wat] soak+ ?r\gh por\s soil 7e4g41 s&7 or rock1 s9ks to ! top ( an und]ly+ imp]vi\s lay] 7e4g41 clay7 along ^: surface x fl[s until x rea*es ! side ( a valley :]e a spr+ results4 ,9 fact1 :]ev] ! wat] table is cross$ by ! surface ( ! gr\nd1 wat] mu/ ei!r seep or fl[ out4 ,:]e und]gr\nd /reams :i* are common 9 lime/one regions rea* ! surface on hill or valley sides1 spr+s result4 ,ano!r s\rce ( spr+s is :]e "u prop] conditions ( slope a por\s rock lay]1 *>g$ ) wat] well bel[ ! surface1 appe>s at a l[] level ?an its s\rce ( wat]4 ,/ill ano!r type ( spr+ is :]e a fissure or fracture crosses a wat]-be>+ lay] 9 :i* ! pressure is great en\gh to cause ! wat] to rise to ! surface along ! relatively op5 fissure or fracture4 ,9 v>i\s localities we he> ( spr+s 9 seem+ly p>adoxical situations on tops ( hills & ev5 m\nta9s4 ,su* a my/]y is n difficult to cle> up4 ,9 ! fir/ place1 su* spr+s are r>ely at ! summit ( ! hill or m\nta94 ,a case well kn[n to _m p]sons is ! small1 b nev]-fail+ spr+ a little bel[ ! summit ( ,m\nt ,:iteface1 a peak 9 ! ,adirondacks1 ris+ #c1jjj feet above ! g5]al level ( ! imm$iately surr\nd+ c\ntry4 ,9 ?is case1 a mass ( highly fractur$ rock1 subject$ to mu* ra9fall & ly+ above ! level ( ! spr+1 is suffici5tly l>ge easily to conta9 & give =? en\gh wat] to acc\nt = sev]al su* spr+s4 ,9 r>e cases1 h[ev]1 spr+s or fl[+ wells are locat$ on summits1 & 9 su* places x is only necess>y to be> 9 m9d "s ( ! pr9ciples above set =?1 b ma9ly ! facts t wat] may travel "u pressure long di/ances und]gr\nd1 & t ! po9t ( em]g5ce may be on a hill :i* is actually l[] ?an ! s\rce ( ! wat] f> away4 ,! economic significance ( und]gr\nd wat]s is =cibly br\ght to our att5tion :5 we realize t #ge p] c5t ( ! p ( ! ,unit$ ,/ates dep5d ^u wells = _! wat] supply4 ,_m city supplies1 mo/ f>m supplies1 & mu* irrigation wat] come f wells4 ,! #c1jjj1jjj p ( ,i[a1 = example1 are dep5d5t ^u und]gr\nd wat]s f wells v>y+ 9 dep? f a few feet to sev]al ?\s& feet4 ,illu/ration3 ,fig4 #bj4--;,ideal section illu/rat+ ! *ief requisite conditions ( artesian wells4 ,a1 a por\s /ratum2 ,b & ,c1 imp]vi\s b$s bel[ & above ,a1 act+ z conf9+ /rata2 ,f1 ! height ( ! wat] level 9 ! por\s b$ ,a1 or1 9 o!r words1 ! height ( ! res]voir or f\nta9head2 ,d & ,e1 fl[+ wells spr++ f ! por\s wat]-fill$ b$ ,a4 7,aft] ,u4 ,s4 ,geological ,survey47 ,mo/ wells are simply dug to dep?s a little bel[ ! wat] table4 ,9 humid climate regions ! dep?s seldom exce$ fifty feet4 ,! wat] enc\nt]$ 9 su* wells is r>ely "u pressure4 ,9 "s regions ( deep soils or loose =mations1 wells are actually bor$ ) an aug] to dep?s ( z great z #bjj feet4 ,deep wells 9 relatively h>d rocks are always drill$ to dep?s ( ev5 ?\s&s ( feet4 ,9 su* cases ! purpose is to /rike ei!r a por\s rock lay] *>g$ ) wat]1 or a crack or fissure fill$ ) wat]1 ! wat] almo/ always be+ "u pressure 7sometimes v great71 "u su* conditions4 ,^! are call$ artesian wells :e!r ! wat] "u pressure actually fl[s out at ! surface or n4 ,we may n[ inquire z to ! necess>y conditions = artesian wells4 ,?is may be/ be done by ! aid ( diagrams4 ,figure #bj illu/rates a v common case :]e a por\s lay]1 ly+ betwe5 imp]vi\s lay]s1 pass+ "u a valley1 comes to ! surface ( ! hills on ea* side :]e ! wat] ent]s ! por\s lay]4 ,on s9k+ a well to ! wat]-*>g$ lay]1 ! wat] ru%es ?r\gh ! hole to a great] or less di/ance above ! surface4 ,9 ,figure #ba ! por\s & imp]vi\s lay]s are simply tilt$1 & ! wat] "u pressure rises ?r\gh ! free op5+ to ! surface4 ,wells ( ?is k9d are also common 9 ! ,atlantic ,coa/al ,pla9 ( ! ,unit$ ,/ates4 ,9 ano!r case1 less compreh5sible to ! layman1 ! por\s wat]-be>+ /ratum curves d[nw>d "u a hill or m\nta91 wat] ent]+ x :]e x is expos$ on ea* side4 ,"u su* conditions a fl[+ artesian well _c be drill$ at or ne> ! summit1 b s9ce ! wat] is "u pressure x w rise 9 ! hole to a level approa*+ t ( ! l[e/ "p ( ! outcrop ( ! por\s lay] on ei!r side ( ! hill or m\nta94 ,?is is ess5tially ! condition ( ?+s t[>d ! int]ior ( ,i[a1 :]e wat] f ! deep] wells rises #b1jjj feet or m 9 ! holes1 b does n rea* ! surface4 ,illu/ration3 ,fig4 #ba4--,section illu/rat+ ! ?9n+ out ( a por\s wat]-be>+ b$4 ,a1 inclos$ betwe5 imp]vi\s b$s ,b & ,c1 ?us furni%+ ! necess>y conditions = an artesian f\nta9 at ,d4 7,aft] ,u4 ,s4 ,geological ,survey47 ,! drill+ ( deep wells1 :]e records1 includ+ samples ( rock mat]ials br\ght up1 h be5 kept1 has be5 a great aid to ! geologi/ 9 det]m9+1 or r5d]+ m precise1 ! k ( n only ! k9ds ( rocks und]gr\nd1 b also ! ?icknesses & /ructural relations ( ! =mations4 ,9 yet ano!r way deep wells are ( special significance1 t is 9 reg>d to ! light :i* !y ?r[ ^u ! subt]ranean temp]ature ( ! e>?4 ,v rec5tly ! deepe/ well 9 ! _w 0 drill$ ne> ,fairmont1 ,we/ ,virg9ia1 to a dep? ( #g1egi feet1 9 que/ ( oil or gas4 ,at a dep? ( #g1ejj feet1 ! temp]ature 0 f\nd to be #afh degrees ,f4 ,all[+ = a ne>-surface temp]ature #ej degrees1 ?is means an av]age rate ( increase d[nw>d ( #a degree 9 #fb feet4 ,! second deepe/ well is ne> ,cl>ksburg1 ,we/ ,virg9ia1 sunk to a dep? ( #g1chf feet1 ) a temp]ature ( #agb degrees at ! #g1jjj-;foot level1 or at ! rate ,( #a degree 9 #eg feet1 all[+ = a ne>-surface temp]ature ( #ej degrees4 ,x is a rem>kable fact1 t little or no wat] 0 enc\nt]$ all ! way d[n4 ,a well #g1cdh feet deep 9 s\!a/]n ,g]many gave a temp]ature ( #ahf degrees at ! bottom1 or a rate ( increase ( #a degree 9 #ed feet4 ,^! ?ree records are ab\t ! av]age = ! deep holes ( ! _w4 ,next to ! deepe/ m9+ %afts 9 ! _w are 9 ! copp] m9+ region ( nor!rn ,mi*igan1 :]e ov] #e1jjj feet 7c\nt$ v]tically1 n d[n ! slope7 d[n ! temp]ature is ne>ly #ij degrees ! ye> r\nd4 ,! rate ( increase is "h less ?an 9 mo/ wells ( su* dep?1 because ( ! cool+ air curr5ts4 ,_m ye>s ago a r rem>kable exp]im5t 9 well drill+ 0 tri$ by ! city ( ,budape/1 ,hung>y1 ! attempt be+ to get a supply ( wat] at ! brew+ temp]ature ( #agf degrees 9 ord] to enc\rage ! manufacture ( be]4 ,aft] gett+ a good supply ( wat] at a dep? ( #c1abj feet & a temp]ature ( #aeh degrees1 "w 0 /opp$4 ,9 build+ ! two great tunnels 7,/4 ,got?>d & ,simplon7 ?r\gh portions ( ! ,alps1 su* high temp]atures 7 enc\nt]$ t "w 0 cont9u$ only "u great difficulties4 ,9 ! fam\s ,com/ock gold & silv] m9e ( ,nevada1 ov] =ty ye>s ago1 temp]atures z high z #aeg degrees 7 enc\nt]$ 9 ! %afts at a dep? ( only #b1jjj feet or a little ov]1 ! exceptional temp]ature = su* dep? no d\bt be+ due to occurr5ce ( ! ores 9 geologically rec5t igne\s rocks :i* h n yet cool$ to ! normal temp]ature = ! dep? ( #b1jjj feet4 ,f ! sanit>y /&po9t1 wells are ( v great significance1 especially 9 view ( ! fact t su* a l>ge proportion ( p dep5d ^u well wat]4 ,x is g5]ally und]/ood t typhoid fev] is m common 9 ! c\ntry ?an 9 cities1 9 spite ( :at might reasonably be expect$4 ,:at are "s ( ! causes lead+ up to su* a situation8 ,! idea t wat] purifies itself aft] fl[+ a relatively %ort di/ance is1 9 _m cases1 f> f be+ true1 especially :5 we are deal+ ) und]gr\nd wat]4 ,actual obs]vations prove t g]m-lad5 wat] may travel surpris+ly f> und]gr\nd4 ,g]m-lad5 wat] f b>ns1 cesspools1 or ou?\ses spreads notably on s9k+ to ! wat] table & x is easy to see h[ s _m wells become contam9at$4 ,on g5]al pr9ciples1 a geologi/ is especially w>y ( wat] f a well 9 a b>n y>d4 ,! well = human use at lea/ %\ld be locat$ out ( reasonable range ( su* contam9ation4 ,"u ! condition ( ! diagram a well or spr+ "s di/ance d[n ! side ( ! hill may actually be unfit = use1 ?\gh a s]i\s situation is mu* less likely to develop !re4 ,nor %\ld "o assume t by locat+ ! well on ! uphill side ( ! h\se1 & ! ou?\ses or cesspool on ! d[nhill side1 safety is assur$4 ,f :at we h le>n$ 9 reg>d to e>? movem5ts1 & ! tilt+ ( /rata f _! orig9al positions1 we "k h[ ! movem5t ( wat] 9 ! saturat$ zone ne> ! surface may be d[nhill r\ghly foll[+ ! hill slope1 :ile 9 a tilt$ por\s lay] ( rock f>!r bel[ ! surface ! movem5t ( wat] may be 9 j ! opposite direction4 ,a well drill$ into ! solid rock = safety on ! uphill side ( a h\se might d]ive its wat] f ?is v same por\s lay]1 ^: wat] has be5 contam9at$ f a cesspool or o!r s\rce d[n ! side ( ! hill4 ,su* a case is by no means a !ory or a r>ity4 ,!re is also real dang] ( contam9ation 9 cases :]e ! wat] fl[s m l /reams und]gr\nd ?r\gh cracks or fissures 9 h>d or d5se rocks1 or ?r\gh *annels develop$ by solution 9 lime/one4 ,x may happ5 t wat] becom+ contam9at$ f b>n sites1 cesspools1 or ou?\ses f9ds its way along su* a *annel to ! side or bottom ( a well4 ,! au?or well rememb]s ! case ( a f>m] ^: h\se1 b>n1 & well 7 close toge!r on a little lime/one t]race & :o cont9u$ to use ! well wat] al?\gh he compla9$ ( its disagreeable ta/e1 especially aft] a ra9 :5 he c\ld ta/e ! b>n 9 x4 ,illu/ration3 ,fig4 #bb4--;,diagram illu/rat+ a dang] ( contam9ation ( wells by impure und]gr\nd wat]4 ,s1 soil2 ,b1 b$rock2 ,p1 por\s /ratum4 ,impure wat] f cesspool moves ?r\gh por\s lay] to bottom ( well4 7,by ! au?or47 ,f9ally1 9 ?is connection1 x may be said t wells %\ld be locat$ 9 ! light ( ! pr9ciples above expla9$1 be/ ( all ^u ! advice ( "s "o ) geological tra9+1 & t1 to insure safety to heal? f ! well wat]1 sanit>y analyses 7at small co/7 %\ld be made once or twice a ye>4 ,a bad well %\ld be ab&on$ & a new "o sunk4 ,a l>ge am\nt ( money has be5 wa/$ ^u1 & mu* my/]y & sup]/ition has surr\nd$ s-call$ wat] wit*es1 or ^? :o claim "s special or sup]natural p[] ( locat+ supplies ( und]gr\nd wat]4 ,mo/ common ( all devices us$ is ! s-call$ div9+ rod1 :i* is a =k$ /ick ( will[1 wit*-hazel1 or o!r wood1 accord+ to ! seem+ly special requirem5t ( ! op]ator4 ,c]ta9 me*anical & electrical devices are also employ$4 ,) "o =k ( ! div9+ rod grasp$ 9 ea* h& & ! ma9 "p ( ! /ick upright1 ! op]ator walks ab\t until1 due to "s my/]i\s influ5ce1 a place is f\nd :]e und]gr\nd wat] pulls ! upright portion ( ! /ick d[nw>d 9 spite ( ! grasp ( ! hold]4 ,"s op]ators ev5 claim to "k j h[ deep a well mu/ be sunk4 ,)\t any attempt to "q ! hone/y ( all op]ators1 geologi/s are 9 full accord ) ! foll[+ quotation f a pap] publi%$ by ,m4 ,l4 ,full]1 = ! ,unit$ ,/ates ,geological ,survey3 ,! uselessness ( ! div9+ rod is indicat$ by ! facts t x may be work$ at w by ! op]ator1 t he fails to detect /rong wat] curr5ts 9 tunnels & o!r *annels t af=d no surface indications ( wat]1 & t 8 locations 9 lime/one regions :]e wat] fl[s 9 well-def9$ *annels are no m successful ?an ^? dep5d5t ^u m]e guesses4 ,9 fact1 its op]ators are successful only 9 regions 9 :i* gr\nd wat] occurs 9 def9ite %eets 9 por\s mat]ial1 or 9 m or less clayey deposits1 su* z pebbly clay or till4 ,9 su* regions 7:i* are extremely common7 few failures c occur1 = wells c get wat] almo/ any:]e4 ,gr\nd wat] occurs "u c]ta9 def9ite conditions1 & j z surface /reams may be expect$ :]ev] !re is a valley1 s gr\nd wat] may be f\nd :]e c]ta9 rocks & conditions exi/4 ,no appliance1 ei!r me*anical or electrical1 has yet be5 devis$ t w detect wat] 9 places :]e pla9 common s5se w n %[ its pres5ce j z well4 ,! only advantage ( employ+ a 'wat] wit*1' z ! op]ator ( ! div9+ rod is sometimes call$1 is t crudely skill$ s]vices are ?us occasionally obta9$1 s9ce ! m5 s employ$1 if end[$ ) any natural %rewdness1 become1 ?r\gh _! exp]i5ce 9 locat+ wells1 bett] obs]v]s ( ! occurr5ces & movem5ts ( gr\nd wat] ?an ! av]age p]son4 ,x %\ld n be assum$1 h[ev]1 f ! above /atem5t t ! location or =etell+ ( und]gr\nd wat] is mo/ly hopeless f a sci5tific po9t ( view4 ,9 mo/ regions ! k9ds ( rocks :i* w\ld be pi]c$ by wells c be m or less accurately =etold by c>eful /udies ( ! rocks expos$ at ! surface4 ,b =etell+ ! und]gr\nd wat] is (t5 mu* m unc]ta94 ,:]e ! geologic /ructure or arrangem5t ( rocks 9 a region is fairly regul>1 z 9 ! case ( mo/ s$im5t>y rocks1 & a few scatt]+ deep wells h be5 drill$1 ) records pres]v$1 ! geologi/1 by comb9+ su* data ) 8 surface /udies1 c d mu* t[>d putt+ ! facts reg>d+ ! und]gr\nd wat]s ( ! region on a sci5tific basis4 ,!re are _m su* regions1 an excell5t case 9 po9t be+ ,i[a1 reg>d+ :i* ,/ate ! ,unit$ ,/ates ,geological ,survey has publi%$ a report conta9+ data by ! use ( :i* x is possible to =etell almo/ exactly :at =mations w\ld be pi]c$ by drill+ f #a1jjj to #c1jjj feet or m1 ! ?ickness ( ea*1 :i* ones are wat]-be>+ &1 9 _m cases1 ev5 ! "* ( ! m9]alization ( ! wat] = almo/ any "p ( ! ,/ate4 ,su* k1 ?r\gh ! ye>s1 is wor? untold millions ( doll>s to ! ,/ate4 ,:]e ! rocks are igne\s & r uni=mly d5se1 usually little or no?+ c be accurately =etold ab\t ! und]gr\nd wat] supplies1 because 9 su* rocks ! wat] foll[s exce$+ly v>iable & irregul> cracks & fissures4 ,9 metamorphic rocks ! difficulties are usually ab\t z great4 ,9 lime/one regions1 ) humid climate1 mu* wat] travels 9 *annels und]gr\nd1 b ^! are s exce$+ly irregul> t !re is no way ( locat+ !m by surface /udies4 ,9 humid climates x seldom happ5s1 h[ev]1 t a well does n rea* at lea/ a fair supply ( wat] )9 a few ?\s& feet ev5 9 rock =mations 9 :i* ! wat] travels along irregul> cracks & *annels4 ,c]ta9 o!r important features ( ! geological "w ( und]gr\nd wat] %\ld be br\ght to ! att5tion ( ! read]4 ,"o ( ^! is its p[] to dissolve m9]al sub/ances ( _m k9ds m or less rapidly4 ,z already po9t$ out1 lime/one is especially susceptible to solution 9 wat]1 bo? surface & und]gr\nd4 ,! c>bonate ( lime tak5 into solution f lime/one is ! pr9cipal sub/ance :i* causes s-call$ h>d wat]4 ,mo/ ( ! solution takes place 9 ! upp] "p ( ! zone ( fracture ( ! e>?'s cru/ & ! dissolv$ sub/ances are c>ri$ along g5]ally to ! l[] levels :]e !y t5d to deposit 7& cry/allize71 fill+ fissures1 cracks1 & ev5 t9y spaces betwe5 m9]al gra9s4 ,cracks & fissures ?us fill$ by m9]al matt] f solution are call$ ve9s4 ,9 _m m9+ regions valuable ores & o!r sub/ances h be5 deposit$ f und]gr\nd wat] solutions & conc5trat$ 9 ve9s4 ,9 _m places und]gr\nd wat]s ) c]ta9 sub/ances 9 solution travel ?r\gh v>i\s rocks or enc\nt] solutions ( o!r sub/ances &1 z a result ( *emical action1 _m new m9]al comb9ations result4 ,su* actions ?r\gh ! millions ( ye>s ( geologic "t h effect$ great *anges 9 _m rock =mations4 ,9 ! case ( petrification1 l t ( petrifi$ wood1 ! buri$ organism sl[ly decomposes cell by cell1 & p>ticle by p>ticle x is replac$ by m9]al matt] f und]gr\nd wat] solutions4 ,9 ?is mann] ! rem>kable s-call$ petrifi$ =e/s 7n really =e/s7 ( ,arizona & ! ,yell[/one ,p>k 7 =m$1 ! petrify+ mat]ial !re hav+ be5 ! v common sub/ance call$ silica :i* is ! same 9 composition z ! famili> m9]al qu>tz4 ,m9]al matt] c>ri$ 9 solution 9 surface /reams is d]iv$ f gr\nd wat]s :i* rea* ! surface4 ,an idea ( ! trem5d\s quantity ( m9]al matt] ?us remov$ may be ga9$ f ! /atem5t t by c>eful det]m9ation ! ,mississippi ,riv] c>ries #abj1jjj1jjj tons 9 solution into ! ,gulf ( ,mexico ea* ye>4 ,illu/ration3 ,fig4 #bc4--,/ructure section & "p ( l&scape 9 a lime/one region %[+ h[ caves & natural bridges are =m$ by ! dissolv+ action ( und]gr\nd wat]4 ,,aa1 lime/one2 ,,bb1 s9k holes2 ,,dd1 caves & gall]ies2 & an ar* 7natural bridge7 :i* is ! remnant ( a l>ge cave4 7,aft] ,%al]1 ,u4 ,s4 ,geological ,survey47 ,"o int]e/+ effect ( ! dissolv+ p[] ( und]gr\nd wat] 9 lime/one regions is ! developm5t ( caves or cav]ns4 ,mo/ rem>kable ( all is ,mammo? ,cave1 ,k5tucky1 ) its hundr$s ( miles ( passageways & gall]ies4 ,?is m>vel\s "w ( nature is all a result ( ! action ( und]gr\nd wat] :i* has dissolv$ & c>ri$ away va/ quantities ( lime/one4 ,e*o ,riv]1 :i* fl[s ?r\gh ! cav]n1 is /ill c>ry+ on ! "w aid$ by v>i\s und]gr\nd tribut>ies4 ,! /alactites & /alagmites1 :i* are s /rik+ly display$ 9 _m caves1 z at ,luray1 ,virg9ia1 9 :i* wat] ) c>bonate ( lime drips or oozes f ! ro( &1 due ma9ly to evaporation1 deposits ! lime4 ,_m wond]ful & fanta/ic effects are ?us produc$4 ,:]e "p ( ! ro( ( a cave is dissolv$ out1 or falls 91 a s9k hole results4 ,:]e all b a portion ( ! ro( ( a cave or und]gr\nd *annel has fall5 91 a natural bridge1 l ! fam\s "o 9 ,virg9ia1 results1 ?\gh natural bridges are also =m$ by o!r means4 ,9 conclud+ ?is *apt] we %all briefly discuss hot und]gr\nd wat]s1 hot spr+s1 & geys]s4 ,!re are two well-kn[n ways by :i* und]gr\nd wat]s may become heat$4 ,"o is by ! movem5t ( wat] d[nw>d into ! normally heat$ portion ( ! e>?1 ! rate ( increase d[nw>d be+1 z above /at$1 #a degree ,f4 = ab\t #ej to #fj feet4 ,wat] desc5d+ two miles w\ld1 !re=e1 atta9 a temp]ature ( ab\t #bjj degrees ,f4 ,9 "s regions su* a temp]ature may be rea*$ at dep?s consid]ably less4 ,su* wat] 7"u pressure7 tak+ a %ort c\rse to ! surface 7=m+ spr+s7 at a l[] level w\ld reta9 mu* ( its heat tak5 up f> bel[ ! surface4 ,9 regions :]e !re are great d[n-folds ( ! /rata 7i4e41 syncl9es71 z 9 ! c5tral to s\!rn ,appala*ians1 conditions appe> to be favorable = su* w>m or hot spr+s1 z1 = example1 at ,hot ,spr+s1 ,virg9ia4 ,a second cause ( ! heat+ ( und]gr\nd wat] is by ! desc5t ( surface wat]s into contact ) masses ( /ill hot igne\s rock ( relatively rec5t geologic age4 ,9 "s su* cases ! wat] does n g m ?an "s hundr$s ( feet d[n & :51 "u prop] conditions1 x returns to ! surface hot & ev5 boil+ spr+s may result4 ,illu/ration3 ,plate #g4--;,an ,upb5d ,fold 7anticl9e7 9 ! ,appala*ian ,m\nta9 ,/rata ,ne> ,hancock1 ,m>yl&4 ,! /rata 7 deposit$ 9 horizontal lay]s ^u ! sea bottom1 cov]+ ! region _m millions ( ye>s ago 9 middle ,paleozoic "t4 ,at ! "t ( ! ,appala*ian ,m\nta9 revolution1 ne> ! end ( ,paleozoic "t1 ?is & _m o!r folds develop$ well bel[ ! surface4 ,removal ( ov]ly+ mat]ial by erosion has laid b>e ! fold z we see x to-day4 7,photo by ,russell1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #h4--7;a7 ,a ,l$ge ( ,igne\s ,rock 7,granite7 9 ,nor!rn ,new ,york4 ,?is illu/rates s-call$ jo9ts or natural cracks1 commonly sep>at+ mo/ h>d rock masses into m or less prismatic blocks4 7,photo by ! au?or47 ,illu/ration3 ,plate #h4--7;b7 ,a ,fault ,fracture 9 a ,l$ge at ,ea/ ,canada ,creek 9 ! ,mohawk ,valley1 ,new ,york4 ,! ,ordovician lime/one =mation 9 ?9 lay]s on ! "r has sunk hundr$s ( feet along v]tical fault to ! left ( middle1 br++ x %>ply aga9/ ! old] 7,cambrian7 massive =mation on ! left4 ,! hole is artificial4 7,photo by ,d>ton1 ,u4 ,s4 ,geological ,survey47 ,geys]s are p]iodically eruptive hot spr+s f\nd only 9 a few ( ! volcanic regions ( ! _w4 ,!y are mo/ wond]fully display$ 9 ! ,yell[/one ,national ,p>k1 :]e !y s5d columns ( hot wat] to all heights up to #bej feet at v>i\s int]vals ( "t4 ,almo/ incr$ible am\nts ( hot wat] are s5t into ! air e day 9 ! geys] bas9s ( ,yell[/one ,p>k4 ,! s+le geys] ,old ,fai?ful1 :i* erupts at int]vals ( ab\t sev5ty m9utes1 s5ds a column ( wat] sev]al feet 9 diamet] to heights ( f #abe to #aej feet4 ,dur+ ea* eruption ab\t #a1ejj1jjj gallons ( wat] are s5t =?1 or e day en\gh to supply ! ne$ ( a fairly l>ge city4 ,a v brief explanation ( ! cause ( geys] eruptions may be /at$ z foll[s3 ,! v irregul>1 n>r[1 geys] tube ext5ds ne>ly v]tically d[nw>d into yet uncool$ lava4 ,! tube is m or less rapidly fill$ by und]gr\nd wat]4 ,! bottom1 or ne>-bottom1 portion ( ! wat] gradually becomes heat$ by ! lava until f9ally ! boil+ po9t is rea*$ = t dep?4 ,b1 because ( ! pressure ( ! ov]ly+ wat] column1 ! boil+ po9t at t dep? is consid]ably great] ?an = ! surface4 ,a little /eam develops f> d[n & ?is causes ! :ole column ( wat] above x to lift slightly1 ?us reliev+ ! pressure on ! sup]heat$ wat] f> d[n4 ,?is relief ( pressure all[s mu* ( ! sup]heat$ wat] f> d[n to fla% into /eam1 :i* viol5tly =ces ! column ( wat] out ( ! geys] tube4 ,,*apt] ,x ,,h[ ,,m\nta9s ,,come ,,& ,,g ,m\nta9s con/itute ! gr&e/ relief features ( ! e>?1 & "s ( ! mo/ pr(\nd lessons ( e>? *anges may be le>n$ by /udy+ !m4 ,to ! layman :o views great m\nta9s 9 all _! gr&eur & massiv5ess1 ! expression ev]la/+ hills seems appropriate4 ,b ! geologi/ kn[s t ev5 ! l(tie/ m\nta9s are only tempor>y features on ! face ( ! e>?4 ,l organisms1 !y come & g4 ,= example1 :]e ! great ,rocky ,m\nta9s n[ /& 0 only a few million ye>s ago 79 late ,mesozoic "t7 ! bottom ( an int]ior sea4 ,:]e ! ,appala*ians n[ /& !re 7 no m\nta9s late 9 ! ,paleozoic era 7n less ?an t5 or twelve million ye>s ago71 b in/ead sea wat] cov]$ ! di/rict4 ,!n ! ,appala*ians 7 =m$1 lift+ _! heads mu* high] ?an at pres5t1 aft] :i* !y 7 cut d[n almo/ to sea level1 & !n once m uprais$4 ,! ,coa/ ,range ,m\nta9s ( our ,pacific ,coa/ h come into exi/5ce s9ce ! middle ( ! pres5t 7,c5ozoic7 geologic era4 ,e m\nta91 l e organism1 has a life hi/ory1 9 "s cases simple1 & o!r cases complex4 ,all pass ?r\gh /ages ( bir?1 y\?1 maturity1 old age1 & dea?4 ,"s re> _! heads & disappe> aft] a %ort 7geological7 exi/5ce4 ,o!rs cont9ue _! gr[? & p]si/ mu* long]1 :ile /ill o!rs und]go p]iods ( pr(\nd rejuv5ation4 ,among ! v>i\s processes by :i* m\nta9 ranges h be5 =m$1 ! fold+ & accompany+ g5]al uplift ( /rata are ! mo/ important4 ,9 fact1 9 mo/ ( ! great m\nta9 ranges ( ! _w ! fold$ /ructure is conspicu\sly develop$1 s mu* s t !y may well be call$ fold$ m\nta9s4 ,v commonly1 h[ev]1 m\nta9s ( ?is type h also be5 subject$ to m or less fractur+ ( ! rocks 7fault+71 & n uncommonly !y h also be5 subject$ to igne\s activity1 includ+ bo? intrusion & extrusion ( molt5 mat]ial4 ,x is among ! fold$ m\nta9s ( great] or less degree ( complexity t ! greate/ exhibitions ( geologic ph5om5a are se5 & ! lessons :i* geology z a sci5ces tea*es may be le>n$4 ,if "o desires to "k ! hi/ory ( a region1 "o turns naturally to its m\nta9 ranges1 = "h may be f\nd ! upturn$ & dissect$ /rata1 a /udy ( ^: k9ds1 ?ickness1 & fossils ?r[s light ^u pa/ ev5ts1 :ile _! fold+s & dislocations %[ ! nature & results ( ^? great dynamic ag5cies :i*1 f "t to "t1 h op]at$ ^u ! out] portion ( ! e>?1 & giv5 to x ! broad di/9ctive features :i* *>act]ize x to-day4 7,l4 ,v4 ,pirsson47 ,among ! great m\nta9s we may also see wond]ful exhibitions ( ! results ( wea!r+ & erosion1 especially ! "w ( riv]s & glaci]s4 ,we c1 p]haps1 be/ convey to ! read] "s ( ! ma9 facts & pr9ciples reg>d+ fold$ m\nta9s by consid]+ c]ta9 obs]vations :i* may be readily made 9 a %ort trip across a fold$ range ( n too complex k9d--= example1 across ! ,appala*ian range along ! l9e ( ! ,baltimore & ,ohio ,railroad1 we/ ( ,wa%+ton1 or ! ,p5nsylvania ,railroad1 we/ ( ,philadelphia4 ,x w\ld be mo/ evid5t t ! m\nta9s consi/ ( /rata1 t is s$im5t>y rocks1 su* z s&/one1 %ale & lime/one1 :i* 7 deposit$ "u wat]4 ,a few measurem5ts w\ld reveal ! fact t ?\s&s ( feet 9 ?ickness ( /rata are repres5t$4 ,c>eful measurem5ts by geologi/s h1 9 fact1 %[n t ! /rata 7 orig9ally pil$ up lay] ^u lay] to a ?ickness ( #be1jjj to #cj1jjj feet4 ,! fact t !y are /rata ( su* great ?ickness proves t s$im5ts mu/ !re h accumulat$ "u wat] = "s millions ( ye>s at lea/4 ,clos] exam9ation ( a few good exposures 7i4e41 outcrops7 w\ld fur!r reveal ! pres5ce ( fossil %ells & impressions ( m>9e organisms1 ?us def9itely lead+ u to conclude t ! /rata 7 accumulat$ "u sea wat]1 :i*1 ( c\rse1 means t ! pres5t site ( ! m\nta9 range 0 once sea floor4 ,exam9ation ( ! rock mat]ials also e/abli%es ! fact t ! /rata are su* z 7 deposit$ 9 relatively %all[ sea wat]--t is to say1 none are at all ( ! sort :i* are n[ =m+ "u really deep ocean wat]4 ,mo/ ( ! /rata repres5t orig9al s&s 7& ev5 gravels7 & muds :i* c\ld h accumulat$ only relatively ne> %ore1 t is )9 ab\t #ajj miles1 :i* h>monizes ) a /atem5t made 9 a prec$+ *apt] to ! effect t v little l&-d]iv$ s$im5t is at pres5t deposit+ m ?an #ajj miles out f %ore4 ,! co>se mat]ials 7s&s & gravels7 c\ld n1 ( c\rse1 be c>ri$ _m miles out1 :ile _m ( ! /rata are cov]$ ) ripple m>ks1 ?us positively prov+ _! %all[-wat] orig94 ,we conclude1 !re=e1 t ! ,appala*ian /rata are ( m>9e1 %all[-wat] orig94 ,b we h already /at$ t ^! /rata are at lea/ #be1jjj feet ?ick4 ,h[1 !n1 d we reconcile ^! two seem+ly p>adoxical /atem5ts8 ,all t is necess>y is to realize t ! floor ( ! %all[ sea1 9 :i* ! s$im5ts erod$ f adjac5t l& 7 be+ deposit$1 sl[ly1 ?\gh m or less irregul>ly1 subsid$ or sank dur+ ! long ages 7millions ( ye>s7 ( _! accumulation4 ,x w\ld c>ry u too f> afield to really attempt an explanation ( ?is rem>kable type ( geologic ph5om5on1 & x mu/ suffice to sugge/ t1 />t+ ) ! e>?'s cru/ 9 equilibrium1 ! v weight ( accumulat+ /rata w\ld t5d to de/roy t equilibrium & s cause subsid5ce4 ,9 our trip across ! m\nta9s x w\ld be /rik+ly evid5t t ! /rata are no long] 9 _! orig9al horizontal position1 z !y 7 pil$ up lay] ^u lay]1 b t !y h be5 notably di/urb$ & ?r[n into folds 7,plate #g71 l>ge & small1 "s masses ( ! /rata hav+ be5 b5t upw>d 7anticl9es7 & o!rs d[nw>d 7syncl9es74 ,su* fold$ /ructures c\ld h be5 develop$ only by a great =ce ( lat]al compression 9 ! e>?'s cru/ )9 ! zone ( fl[age4 ,"u compression ! /rata 7 ma%$ toge!r1 notably b5t into curves 7folds71 & m or less uprais$4 ,x w\ld also be readily obs]v$ t ! ma9 axes ( ! folds ext5d ess5tially p>allel to ! ma9 tr5d ( ! m\nta9 range1 ?us prov+ t ! =ce ( compression 0 ex]t$ at "r angles to ! tr5d ( ! range4 ,illu/ration3 ,fig4 #bd4--;,diagrammatic sections illu/rat+ ! developm5t ( a typical fold$ m\nta9 range4 ,upp] figure3 ,a1 ! old l& erod$ to furni% s$im5ts deposit$ "u ! adjac5t sea at ,c4 ,middle figure3 /rata 7,c7 fold$ z !y w\ld appe> if unaffect$ by erosion1 & a d[n-w>p 7,b7 betwe5 ,a & ,c4 ,l[] figure3 condition aft] pr(\nd erosion1 & fill+ ( ,b ) s$im5t4 7,drawn by ! au?or47 ,us+ a biological analogy1 a brief hi/ory ( a typical fold$ m\nta9 range may be /at$ z foll[s3 ,fir/1 !re is ! pr5atal or embryonic /age :5 ! mat]ials ( ! range are ga!r+1 t is :5 ! s$im5ts are pil+ up lay] ^u lay] relatively ne> %ore on a s9k+ sea bottom4 ,next comes ! bir? ( ! range :51 due to ! great lat]al compressive =ce1 ! /rata are ?r[n into folds & =c$ to appe> above sea level1 ! range ?us lit]ally be+ born out ( ! sea4 ,dur+ ! next1 or y\?ful /age1 ! range gr[s 7) increas+ altitudes7 because ( cont9u$ application ( ! compressive =ce4 ,ev5 dur+ ! y\?ful gr[+ /age wea!r+ & erosion attack ! range & t5d to r$uce x4 ,!n comes ! /age ( maturity1 :5 ! upbuild+ 7compressive7 =ce & ! te>+ d[n 7erosive7 =ce ab\t c\nt]balance ea* o!r4 ,at ?is "t ! range has rea*$ its maximum height & rugg$ness ( relief1 ) ridges & valleys high] & deep] ?an at any o!r "t4 ,! old-age /age sets 9 :5 ! upbuild+ p[] wanes or actually ceases1 & erosion dom9ates or reigns supreme4 ,sl[ly b surely1 unless !re be a r5ewal by an upbuild+ p[]1 ! range is cut d[n until little or no?+ ( x rema9s well above sea level1 or1 9 o!r words1 until a p5epla9 is develop$4 ,?is la/ /age may truly be call$ ! dea? ( ! range4 ,usually1 h[ev]1 "s local portions ( ! disappe>+ range1 :i* are m resi/ant or m favorably situat$ aga9/ erosion1 are left /&+ to at lea/ mod]ate heights above ! g5]al level ( ! pla9 ( erosion4 ,! above normal ord] ( ev5ts may be di/urb$ at any /age1 especially aft] maturity1 by r5ew$ uplift :5 ! /reams are reviv$ 9 activity & increas$ rugg$ness results4 ,ev5 aft] ! :ole range z a relief feature has be5 plan$ away1 ! site ( ! range may be uplift$ & a new cycle ( erosion />t$4 ,by ! use ( two well-kn[n examples we %all n only illu/rate ! above pr9ciples ( m\nta9 hi/ory1 b also %[ t no less ?an a few million ye>s mu/ be all[$ = ! gr[? & decay ( a great fold$ range4 ,dur+ ! la/ 7,p]mian7 p]iod ( ! ,paleozoic era ! ,appala*ian /rata began to buckle & ! yield+ to pressure cont9u$ till well into ! succe$+ 7,triassic7 p]iod4 ,! climax 0 rea*$ ab\t ! close ( ! ,p]mian4 ,!n1 ?r\gh\t ! ,mesozoic era1 erosion r$uc$ ! c5tral ,appala*ians to a great pla9 7p5epla97 ne> sea level1 aft] :i*1 ab\t ! beg9n+ ( ! pres5t 7,c5ozoic era71 ! site ( ! =m] range 0 di/9ctly uprais$ 7)\t fold+ ( ! rocks71 caus+ ! reviv$ /reams to beg9 _! "w ( c>v+ out ! pres5t ridges & valleys1 ?is "w /ill be+ 9 progress4 ,9 ! case ( ! ,si]ra ,nevadas1 ! /rata 7 fold$ into a l(ty m\nta9 range relatively late 9 ! ,mesozoic era &1 by ! middle ( ! ,c5ozoic era1 ! old-age /age ( erosion 0 well advanc$ :5 ! range 0 n m ?an a few ?\s& feet high4 ,!n 79 ! middle ( ! ,c5ozoic era7 uplift1 accompani$ by fault+ on a l>ge scale1 b n by fold+1 took place1 & ! range 0 notably rejuv5at$ to ab\t its pres5t height4 ,all ! rem>kably deep canyons ( ! ,si]ras h be5 c>v$ out s9ce ! rejuv5ation4 ,h[ is ! geological bir?day ( a m\nta9 range det]m9$8 ,9 ! prec$+ p>agraph we /at$ t ! ,appala*ians 7 fold$ & born out ( ! sea ab\t ! close ( ! ,paleozoic era4 ,?is is readily prov$ by call+ att5tion to two facts4 ,fir/1 ! y\nge/ /rata involv$ 9 ! fold+ are ( ,p]mian1 or late ,paleozoic ,age 9 ! geologic column1 z prov$ by _! fossil cont5t1 etc41 & obvi\sly ! fold+ mu/ h tak5 place aft] !y _h be5 deposit$4 ,cle>ly1 !n1 ! fold+ c\ld n h tak5 place be=e v late ,paleozoic "t4 ,second1 ! olde/ /rata re/+ ^u ! fold$ rocks are ( e>ly 7n ! v e>lie/7 ,mesozoic ,age1 & ^! /rata are some:at tilt$ b n fold$4 ,obvi\sly1 !n1 ! fold+ mu/ h occurr$ be=e ! nonfold$ /rata 7 deposit$1 :i* means t ! fold+ mu/ h be5 ess5tially complet$ 9 n lat] ?an e>ly ,mesozoic "t4 ,or1 9 ! case ( ! ,rocky ,m\nta9s1 we "k t /rata 7 !re fold$ late 9 ! ,mesozoic era or v e>ly 9 ! ,c5ozoic era1 because fold$ rocks z late 9 age z late ,mesozoic 7,cretace\s7 h re/+ ^u !m1 9 "s places1 nonfold$ /rata ( e>ly ,c5ozoic 7,t]ti>y7 ,age4 ,! figure cle>ly %[s h[ ! ,ordovician /rata mu/ h be5 fold$ be=e ! next 7,silurian & ,devonian7 /rata 7 deposit$ ^u !m 9 s\!a/]n ,new ,york4 ,illu/ration3 ,fig4 #be4--;,diagram illu/rat+ ! topography & fold$ /ructure ( ! ,appala*ian ,m\nta9s we/ ( ,h>risburg1 ,p5nsylvania4 ,! valleys h be5 et*$ out ( belts ( weak rocks1 :ile outcropp+ resi/ant rocks /& out to =m ridges4 ,note ! c\rse ( ! ,susquehanna ,riv] across ! m\nta9 ridges1 ?is be+ a sup]impos$ riv] 7see text1 p4 #bcc74 7,drawn by ,a4 ,k4 ,lobeck47 ,illu/ration3 ,fig4 #bf4--,only slightly tilt$ /rata ( ,silurian & ,devonian ages re/+ ^u fold$ /rata ( ,cambrian & ,ordovician ages 9 an ea/-we/ section across ! ,catskill ,m\nta9s & ,hudson ,valley ( ,new ,york4 ,! fold+ took place at ! "t ( ! ,taconic ,m\nta9 ,revolution t[>d ! end ( ! ,ordovician p]iod4 7,drawn by ! au?or47 ,z already sugge/$1 h[ev]1 fold+ is n ! only me?od by :i* m\nta9s are =m$4 ,_m ranges are ei!r entirely due to ! tilt+ ( e>? blocks by fault+ or fractur+ ( ! e>?1 or _! pres5t altitude1 at lea/1 is a direct result ( fault+4 ,su* may be call$ block m\nta9s4 ,!y are wond]fully repres5t$ by ! v>i\s nor?-s\? ranges ris+ "s ?\s&s ( feet above ! g5]al level ( ! ,great ,bas9 region ( ,utah & ,nevada4 ,^! ranges are1 9 %ort1 some:at erod$ edges ( approximately p>allel-tilt$ fault blocks ly+ betwe5 ! ,si]ra ,nevada ,range & ! ,wasat* ,range4 ,9 s\!a/]n ,oregon a s]ies ( ne>ly p>allel block m\nta9s1 up to =ty miles 9 l5g? & ov] #a1jjj feet 9 height1 %[ v /eep ea/]n fronts only slightly modifi$ by erosion4 ,ano!r mode ( orig9 ( m\nta9s is by ! rise ( molt5 mat]ial to ! surface1 especially :]e a *a9 ( volcanoes is locat$4 ,?us ! ,cascade ,m\nta9s f nor!rn ,cali=nia ?r\gh ,oregon & ,wa%+ton1 includ+ ,m\nts ,lass51 ,%a/a1 ,pitt1 ,bak]1 ,/4 ,hel5s1 & ,ra9i]1 are v l>gely ! result ( volcanic action4 ,! long *a9 ( ,aleutian ,isl&s ( ,alaska1 ref]r$ to 9 our /udy ( volcanoes1 is an excell5t example ( a great m\nta9 range n[ be+ built up out ( ! sea by volcanic action4 ,m locally molt5 rocks "u pressure may n rea* ! surface b in/ead simply bulge or dome ! /rata ov] !m1 z 9 ! case ( ! gr\p kn[n z ! ,h5ry ,m\nta9s ( ,utah1 & also 9 o!r p>ts ( ! ,we/4 ,9 /ill o!r cases m\nta9s ( consid]able area & altitude h result$ f erosion ( uplift$ regions :]e ! uplift has be5 practically unaccompani$ by ei!r fold+1 fault+1 or igne\s activity4 ,any l[-ly+ area1 reg>dless ( ! "* ( its rocks1 /ructure1 or previ\s hi/ory1 may be notably uprais$ & simply subject$ to erosion4 ,an excell5t illu/ration is af=d$ by ! ,catskill ,m\nta9s ( ,new ,york1 :]e num]\s deep valleys & n>r[ ridges h be5 c>v$ out ( uprais$ ne>ly horizontal /rata4 ,! s-call$ ,bad ,l&s region ( p>ts ( ,s\? ,dakota & ,wyom+ is also ess5tially ( ?is type1 :]e deep1 n>r[ valleys & %>p ridges h be5 et*$ out ( high1 relatively s(t1 ne>ly horizontal /rata1 result+ 9 an almo/ impassable maze ( m\nta9s4 ,9 ! high1 rec5tly uprais$ ,colorado ,plateau ( p>ts ( ,arizona1 ,new ,mexico1 ,colorado1 & ,utah1 ne>ly horizontal /rata are be+ et*$ out1 ! result be+ num]\s buttes1 mesas 7flat-topp$ hills & m\nta9s7 & deep canyons1 includ+ ! ,gr& ,canyon ) its maze ( peaks & p9nacles1 _m ( !m ris+ l m\nta9s out ( ! canyon dep?s4 ,m\nta9s ( ! pure types j describ$ are n ! prevail+ ones ( ! e>?4 ,mo/ m\nta9s & _! /ructures1 z we see !m to-day1 are products ( two or m ( ! processes ( fold+1 fault+1 igne\s action1 & erosion4 ,a few well-kn[n examples w suffice to make ?is matt] cle>]4 ,?us1 ! ,appala*ian ,m\nta9s orig9ally develop$ by sev]e fold+ ( ?ick /rata4 ,aft] consid]able erosion1 num]\s small & l>ge ?ru/ faults develop$1 "s ( ! dislocations am\nt+ to miles4 ,!n ! :ole range 0 cut d[n ne>ly to sea level by erosion1 aft] :i* ! di/rict 0 uprais$ 7)\t fold+7 mo/ly f #b1jjj to #d1jjj feet1 & ! pres5t long1 n>r[ m\nta9 ridges & valleys h be5 c>v$ out by /ream erosion4 ,?us fold+1 fault+1 & erosion all ent] into ! height & /ructure ( ! ,appala*ians4 ,a l(ty m\nta9 range /ill m complex 9 its hi/ory is ! ,si]ra ,nevada ( ,cali=nia4 ,fir/1 ?ick /rata 7 highly fold$1 uprais$1 & intrud$ by great masses ( molt5 granite4 ,erosion !n proce$$ to cut ! range d[n to hills1 aft] :i* a great fracture 7fault7 develop$ along ! ea/]n side & ! ,si]ra ,nevada e>? block 0 notably tilt$ ) /eep ea/]n front & long we/]n slope4 ,erosion has consid]ably modifi$ ! ea/]n fault face1 & ! deep canyons l ,yosemite1 ,k+'s ,riv] & ,am]ican ,riv]1 h be5 c>v$ out ( ! we/]n slope ( ! great tilt$ fault block4 ,geologically rec5tly ! c5tral to nor!rn portion ( ! range has be5 affect$ by volcanic action1 /reams ( lava 9 "s cases hav+ fl[$ d[n ! valleys4 ,,*apt] ,,xi ,a ,,/udy ,,( ,,lakes ,lakes are ephem]al features on ! face ( ! e>?4 ,comp>$ to ! t5s ( millions ( ye>s ( kn[n e>? hi/ory1 lakes1 ev5 l>ge ones1 are v %ort liv$4 ,!y may1 9 tru?1 be reg>d$ z m]ely results ( ! tempor>y ob/ructions to dra9age4 ,lake bas9s are kn[n to orig9ate 9 _m ways1 & !re are v>i\s means by :i* !y are de/roy$4 ,n attempt+ an exhau/ive1 sci5tific treatm5t ( ! subject1 our pres5t purpose may be well s]v$ by describ+ & expla9+ "s ( ! bett] kn[n & m rem>kable lakes ( ! _w4 ,ev5 a cursory exam9ation ( a l>ge map ( ! _w reveals ! fact t ! regions ( mo/ num]\s lakes are ^? :i* 7 rec5tly occupi$ by glaci]s--ei!r ! va/ ice %eets ( ! ,glacial epo* or m\nta9 7or valley7 glaci]s4 ,?is is because m lakes ( ! pres5t "t h come into exi/5ce z direct or indirect results ( glaciation ?an by any o!r cause4 ,a consid]able numb] ( ^! lakes occupy rock bas9s :i* h be5 erod$ or excavat$ by ! direct action ( fl[+ ice4 ,small lakes ( ?is sort are commonly f\nd 9 ! upp] p>ts ( valleys =m]ly occupi$ by m\nta9 or s-call$ ,alp9e glaci]s1 because !re ! excavat+ p[] ( su* glaci]s 0 especially effective4 ,m r>ely rock bas9s h be5 sc\r$ out by glaci]s f>!r d[n _! valleys4 ,_m lakes occupy rock bas9s excavat$ by ice 9 ! high ,si]ra ,nevada & ,cascade ,ranges1 9 ! ,rocky ,m\nta9s f ,colorado into ,canada1 9 ! ,alps1 & 9 ! m\nta9s ( ,norway4 ,few1 if any ( !m are1 h[ev]1 l>ge or fam\s4 ,o!r lakes1 "s ( v consid]able size1 occupy rock bas9s sc\r$ out by ! passage ( ! great ice %eets ( ! ,glacial epo* 9 ,nor? ,am]ica & ,europe1 ?\gh !y are less common ?an =m]ly suppos$4 ,"s ( ! _m lake bas9s ( ,ont>io1 ,canada1 are q c]ta9ly ( ?is orig91 z might well be expect$1 because ! p[] ( ! great ice %eet 0 !re 9 g5]al notably great] ?an s\? ( ! ,great ,lakes :]e ! t5d5cy 0 to unload or deposit ! erod$ mat]ials z %[n by ! great accumulations ( glacial dbris 7mora9es74 ,:]e ! ice walls ( c]ta9 exi/+ glaci]s =m dams across valleys1 wat]s are pond$1 a small lake ( ?is k9d occurr+ alongside ! ,great ,alets* ,glaci] ( ! ,alps1 :]e its wall is sl[ly mov+ pa/ a tribut>y valley4 ,lakes ( ?is k9d also occur 9 ,gre5l& & 9 ,alaska1 b none are ( consid]able size4 ,dur+ ! ,great ,ice ,age1 h[ev]1 lit]ally ?\s&s ( l>ge & small lakes 7 =m$1 bo? dur+ ! advance & ! retreat ( ! ice1 :]ev] ! glaci] wall block$ valleys :i* slop$ d[nw>d t[>d ! ice4 ,new ,york ,/ate furni%es _m f9e examples ( l>ge & small lakes ( ?is sort4 ,?us1 :5 ! great glaci] 0 melt+ 9 nor!rn ,new ,york1 wat]s hundr$s ( feet deep & _m miles long 7 pond$ betwe5 two ice lobes--"o retreat+ ea/w>d & ! o!r we/w>d f ! ,mohawk ,valley4 ,an ice dam lake 0 also =m$ a little lat]1 :5 an ice wall block$ ! nor!rn "p ( ! ,black ,riv] ,valley j we/ ( ! ,adirondack ,m\nta9s & caus$ a lake cov]+ ab\t #bjj squ>e miles4 ,"o ( ! l>ge/ ( all kn[n ice dam lakes has be5 call$ ,lake ,agassiz1 :i* atta9$ a maximum l5g? ( ov] #gjj miles & a wid? ( #bej miles 9 ! ,r$ ,riv] ( ! ,nor? region ( ea/]n ,nor? ,dakota1 we/]n & nor?we/]n ,m9nesota1 & nor?w>d into ,canada1 mo/ ( its area hav+ be5 9 ,canada4 ,x began z a small lake ) s\?w>d dra9age into ! ,mississippi :5 ! great nor?w>d retreat+ ice %eet =m$ a dam across ! valley ( ! ,r$ ,riv] ( ! ,nor?4 ,! retreat+ ice cont9u$ to block ! nor?w>d dra9age until ! va/ lake1 cov]+ a great] t]ritory ?an all ( ! pres5t ,great ,lakes comb9$1 0 develop$4 ,bea*es1 b>s1 deltas & ! outfl[ *annel ( ?is rem>kable lake are wond]fully well pres]v$4 ,lake ,w9nipeg is a m]e remnant ( great ,lake ,agassiz4 ,_m ponds & small lakes occupy bas9s =m$ by irregul> accumulations ( glacial 7mora9ic7 mat]ials4 ,/ill o!rs lie 9 depressions :i* =m$ by ! melt+ ( masses ( ice :i* became :olly or p>tly buri$ by ice deposits1 or by s$im5ts wa%$ into bodies ( wat] :i* 7 held up by ice dams4 ,depressions ( ! latt] k9d are commonly f\nd z pits or s-call$ kettle holes bel[ ! g5]al level ( s& flats or s& pla9s ( glacial lake orig94 ,mo/ common ( all lake bas9s ( glacial orig9 are ^? =m$ by accumulation ( glacial dbris or mora9ic mat]ials act+ z natural dams across valleys4 ,?is is1 9 fact1 ! mo/ common ( all ways by :i* exi/+ lake bas9s1 "s ( !m v l>ge1 h be5 =m$4 ,mo/ ( ! ?\s&s ( ponds & lakes ( ,m9nesota1 ,wiscons91 & nor!rn ,new ,york belong 9 ?is category4 ,9 ! ,adirondack ,m\nta9s1 = example1 mo/ ( ! lakes1 l ! well-kn[n ,lake ,placid1 ,s>anac ,lakes1 ,long ,lake1 & ,s*roon ,lake1 h _! wat]s pond$ by s+le dams ( glacial dbris across valleys4 ,9 "s cases a s]ies ( su* dams blockades a valley & =ms a *a9 ( lakes l ! well-kn[n ,fulton ,*a9 9 ! ,adirondacks4 ,less commonly ! lake may h its wat]s pond$ by two natural dams ( glacial dbris1 "o across a valley at ea* end ( a lake4 ,a v f9e1 l>ge scale example ( ! la/-nam$ type is ! fam\s ,lake ,george 9 ! s\!a/]n ,adirondacks4 ,x is ov] #cj miles long & f #a to #b-a_/b miles wide4 ,x lies 9 ! bottom ( a deep1 n>r[ m\nta9 valley1 m\nta9 sides ris+ v /eeply f a few hundr$ feet to #b1jjj or m feet above its %ores4 ,!re are _m isl&s1 especially 9 ! s-call$ ,n>r[s1 ?us greatly enhanc+ ! sc5ic effect4 ,! valley itself has be5 produc$ by a comb9ation ( fault+ & erosion4 ,!re 0 a preglacial /ream divide at ! pres5t location ( ! ,n>r[s4 ,?is divide 0 some:at r$uc$ by ice erosion :5 ! deep1 n>r[ body ( ice pl[$ its way ?r\gh ! valley dur+ ! ,ice ,age4 ,dur+ ! retreat ( ! ice heavy mora9ic accumulations 7 left z dams across ! valley at ea* end ( ! lake4 ,ano!r rem>kable body ( wat]1 simil> to ,lake ,george 9 its orig91 is ,*autauqua ,lake ( we/]n ,new ,york1 fam\s = its ,*autauqua assemblies4 ,x lies #a1cch feet above sea level1 ) its nor!rn end ne> ! edge ( ! /eep front ( ! plateau ov]look+ ,lake ,erie4 ,*autauqua ,lake really consi/s ( p>ts ( two valleys1 "o slop+ nor? & ! o!r slop+ s\?1 ea* damm$ by glacial deposits4 ,! fam\s ,alp9e lakes--,g>da1 ,como1 & ,maggiore--h result$ f deposition ( glacial mora9ic mat]ials "u conditions diff]5t f ^? above describ$4 ,9 ^! cases great m\nta9 or valley glaci]s once fl[$ d[n ! valleys & spread out "p way ^u ! ,italian pla94 ,great accumulations ( glacial dbris took place ar\nd ! bord]s ( ! glaci] lobes1 &1 aft] retreat ( ! ice1 ! glacial deposits act$ z dams pond+ ! wat]s f> back into ! m\nta9 valleys4 ,! orig9 & hi/ory ( ! ,great ,lakes con/itutes "o ( ! mo/ int]e/+ & rem>kable *apt]s 9 ! rec5t geological hi/ory ( ,nor? ,am]ica4 ,mo/ ( ! sali5t po9ts h be5 well work$ out & !y may be v briefly summ>iz$1 z foll[s3 ,be=e ! ,ice ,age ! ,great ,lakes did n exi/1 because ! region1 prior to t "t1 _h be5 l& subject$ to erosion = millions ( ye>s--a "t altoge!r too long = any lake to survive4 ,_! sites 7 occupi$ by broad1 l[1 /ream-cut valleys :i* 7 q c]ta9ly locally some:at deep5$ by ice erosion dur+ ! ,ice ,age4 ,ice erosion is1 h[ev]1 altoge!r insuffici5t to acc\nt = ! great clos$ bas9s4 ,! two mo/ important factors ent]+ into ! =mation ( ! bas9s ( ! ,great ,lakes 7 d\btless ! great glacial 7mora9ic7 accumulations act+ z dams along ! s\? side1 & ! tilt+ ( ! l& d[nw>d on ! nor? side ( ! region4 ,9 support ( ?is explanation x has be5 e/abli%$ t ! great dump+ gr\nd ( ice-transport$ mat]ials f ! nor? 0 9 g5]al along ! s\!rn side ( ! ,great ,lakes & s\?w>d4 ,x has also be5 well e/abli%$ t1 late 9 ! ,ice ,age1 ! l& on ! s\!rn side ( ! ,great ,lakes region 0 l[] ?an at pres5t1 z prov$ by ! tilt$ "* ( bea*es ( ! well-kn[n ext9ct glacial lakes :i* 7 ! ance/ors ( ! pres5t lakes4 ,su* a d[n-w>p ( ! l& mu/ h help$ to =m ! clos$ bas9s by t5d+ to /op ! s\?w>d & s\?we/w>d dra9age ( ! region4 ,illu/ration3 ,fig4 #bg4--,sket* map %[+ a v e>ly /age 9 ! hi/ory ( ! ,great ,lakes :5 two relatively small lakes 9 front ( ! ice wall sep>ately dra9$ into ! ,mississippi ,riv]4 7,drawn by ! au?or f map by ,taylor ,lev]ett47 ,illu/ration3 ,fig4 #bh4--,lake ,:ittlesey /age ( ! ,great ,lakes hi/ory :5 ! ice _h retreat$ f> en\gh to all[ ! ea/]n & we/]n ice m>g9 wat]s to jo9 ) a s+le outlet pa/ ,*icago4 7,drawn by ! au?or f a map by ,taylor ,lev]ett47 ,illu/ration3 ,fig4 #bi4--,! ,algonqu9-,iroquois /age ( ! ,great ,lakes :5 _! :ole area 0 ice-free1 & all _! wat]s dra9$ ?r\gh ! ,mohawk-,hudson ,valleys ( ,new ,york into ! ,atlantic ,ocean4 7,aft] ,taylor1 publi%$ by ,new ,york ,/ate ,museum47 ,we %all n[ v briefly trace out ! pr9cipal /ages 9 ! hi/ory ( ! ,great ,lakes dur+ ! f9al retreat ( ! va/ ice %eet4 ,?is may be/ be done by ! aid ( maps :i* ne$ only brief explanation4 ,:5 ! ice %eet _h retreat$ f> en\gh nor?w>d to uncov] ! v s\!rn end ( ! ,lake ,mi*igan bas9 & a little beyond1 a small glacial lake 7,lake ,*icago7 develop$ aga9/ ! ice wall4 ,its outlet 0 ?r\gh ! ,ill9ois ,riv] & !nce into ! ,mississippi4 ,at ! same "t a l>g] glacial lake1 held up by ! ice wall1 develop$ ov] ! we/]n "p ( ! ,erie bas9 & beyond4 ,its outlet 0 ?r\gh ! ,waba% ,riv]4 ,) fur!r retreat ( ! ice a l>ge lake 7,:ittlesey7 cov]+ consid]ably m ?an ! area ( ,lake ,erie develop$1 ) outlet we/w>d across ,mi*igan into ! enl>g$ ,lake ,*icago :i* cont9u$ to dra9 into ! ,ill9ois ,riv]4 ,dur+ a /ill lat] /age ( ice )drawal ! rem>kable set ( ?ree glacial lakes exi/$--,lakes ,dulu?1 ,*icago1 & ,lundy4 ,ea* ( ^! l>ge lakes _h its own outlet4 ,lake ,dulu? cov]$ ab\t half ( ! ,lake ,sup]ior bas9 & dra9$ ?r\gh ! ,/4 ,croix ,riv] into ! ,mississippi4 ,lake ,*icago exp&$ to cov] ne>ly all ( ! ,mi*igan bas9 & cont9u$ to dra9 ?r\gh ! ,ill9ois ,riv]4 ,lake ,lundy cov]$ n only m ?an ! area ( ! ,erie bas91 b also consid]able t]ritory nor? ( ,detroit1 & dra9$ ea/w>d alongside ! ice lobe ( ! ,ont>io bas9 ?r\gh ! ,mohawk & ,hudson valleys ( ,new ,york1 & into ! ,atlantic ,ocean4 ,j aft] ! ice completely )drew f ! area n[ occupi$ by ! ,great ,lakes1 b /ill block$ ! ,/4 ,lawr5ce ,valley1 ! va/ body ( wat] call$ ,lake ,algonqu9 m ?an cov]$ ! sites ( ! pres5t ,sup]ior1 ,mi*igan1 & ,huron4 ,at ?is "t ! l& 0 di/9ctly l[] t[>d ! nor!a/ ?an at pres5t1 caus+ ! outlets to ! we/ to be ab&on$4 ,! great ,lake ,algonqu9 p\r$ its wat]s ea/w>d ?r\gh ! ,tr5t ,riv] *annel ( ,ont>io1 ,canada1 into glacial ,lake ,iroquois1 :i* 0 ! great ance/or ( ,lake ,ont>io4 ,lake ,iroquois1 9 turn1 _h its outlet ea/w>d ?r\gh ! ,mohawk & ,hudson ,valleys ( ,new ,york4 ,= "p ( ! "t at lea/1 ,lake ,erie ma9ta9$ a sep>ate exi/5ce dis*>g+ into ,lake ,iroquois ne> ,buffalo4 ,dur+ ! ,algonqu9-,iroquois /age ! comb9$ area ( all ! lakes 0 notably great] ?an ! pres5t area ( ! ,great ,lakes4 ,! volume ( wat] dis*>g$ by ! lakes ?r\gh ! ,mohawk ,valley ( ,new ,york 0 d\btless great] ?an t :i* n[ goes ov] ,niag>a ,falls4 ,gradually1 z ! ,/4 ,lawr5ce ice lobe wan$1 ! outlet wat]s ( ! lakes began to move alongside ! ice ?r\gh ! ,/4 ,lawr5ce ,valley4 ,f9ally ! ice )drew f> en\gh to free ! ,/4 ,lawr5ce ,valley & ! wat]s ( ! ,great ,lakes region dropp$ to a /ill l[] level1 br++ ab\t ! ,nipiss+ ,great ,lakes /age n greatly diff]5t f ! pres5t4 ,ea/ & nor!a/ ( ! ,lakes ! l& 0 l[ en\gh to all[ tidewat] 7! s-call$ ,*ampla9 ,sea7 to ext5d ?r\gh ! ,hudson1 ,*ampla91 & ,/4 ,lawr5ce ,valleys1 & possibly into ! ,ont>io bas91 z prov$ by ! occurr5ce ( m>9e bea*es & fossils4 ,! wat]s 9 ! ,erie & ,ont>io bas9s cov]$ ab\t ! pres5t areas1 :ile ! ,nipiss+ ,lakes1 :i* cov]$ a little m ?an ! pres5t areas ( ! ?ree upp] ,great ,lakes1 _h _! outlet ?r\gh ! ,ottawa ,riv] *annel into tidewat] 7,*ampla9 ,sea74 ,po/glacial w>p+ ( ! l& has br\ght ! :ole region to ! pres5t condition4 ,illu/ration3 ,fig4 #cj4--,map %[+ next to ! pres5t /age ( ! ,great ,lakes hi/ory :5 ! l& 0 l[] on ! nor? & ! upp] 7,nipiss+7 lakes dra9$ ?r\gh ! ,ottawa ,riv] ,valley into an arm ( ! sea 7,*ampla9 ,sea7 :i* rea*$ ?r\gh ! ,*ampla9 & ,hudson ,valleys4 7,aft] ,taylor1 publi%$ by ,new ,york ,/ate ,museum47 ,_m lakes1 includ+ "s rem>kable ones1 occupy bas9s :i* are directly due to movem5ts ( ! e>?'s cru/--ei!r fault+ or w>p+4 ,an example ( a lake occupy+ "p ( a fault bas9 is ! fam\s ,dead ,sea ( ,pale/9e4 ,?is lake lies 9 ! l[e/ "p ( ! ,jordan ,valley1 :i* has geologically rec5tly come into exi/5ce by ! s9k+ ( a long1 n>r[ block ( e>? = sev]al ?\s& feet betwe5 two great e>? fractures 7faults74 ,! ,dead ,sea cov]s ab\t #ejj squ>e miles & its surface lies ab\t #a1cjj feet bel[ sea level1 :i* makes x ! l[e/ lake 9 ! _w4 ,almo/ equally rem>kable is ! fact t its dep? is ab\t #a1cjj feet1 s t ! l[e/ "p ( ! lake bas9 is #b1fjj feet bel[ sea level4 ,! lake conta9s approximately #bd p] c5t salt1 mo/ly common table salt1 caus+ x to be a ?ick br9e 9 :i* !re is nei!r plant nor animal life--h5ce ! "n ,dead ,sea4 ,at "o "t1 probably j aft] ! ,ice ,age1 ! lake 0 mu* l>g] & deep]1 :5 x fill$ a consid]able "p ( ! ,jordan ,valley & _h an outlet to ! s\?4 ,dur+ ! high-level /age ! wat] 0 fre%1 b gradually1 z ! climate became dri]1 evaporation 0 great] ?an intake1 ! outlet 0 ab&on$1 & ! m9]al matt] 7mo/ly *loride ( magnesia & common table salt7 c>ri$ by ! /reams 9 solution into ! %r9k+ lake /eadily accumulat$ until ! high degree ( sal9ity ( ! pres5t "t has be5 rea*$4 ,great ,salt ,lake1 ,utah1 is a rem>kable lake ^: hi/ory has be5 c>efully /udi$4 ,x occupies ! l[e/ position ( an ext5sive bas9 :i*1 9 turn1 =ms b "p ( ! :ole great di/rict ( ,utah :i* has geologically rec5tly sunk ?\s&s ( feet on ! we/ side ( ! great fault already describ$ z occurr+ along ! we/]n base ( ! ,wasat* ,m\nta9s4 ,at pres5t ! lake cov]s ab\t #b1jjj squ>e miles1 b its area fluctuates consid]ably4 ,x is sc>cely believable t ?is big lake has an av]age dep? ( only fifte5 feet & a maximum dep? ( only fifty feet4 ,x lies #d1bjj feet above sea level1 & x c>ries ab\t #ah p] c5t salts 9 solution4 ,mo/ abundant by f> is common table salt1 ( :i* !re are no less ?an #e1jjj1jjj1jjj tons 9 solution4 ,! wat]s also conta9 ab\t #ijj1jjj1jjj tons ( o!r salts4 ,%\ld ! lake completely disappe> by evaporation1 ^! salts w\ld be deposit$4 ,all[+ = c>s #dj feet long & ( #dj tons capacity1 a tra9 m ?an #a1jjj1jjj miles long w\ld be requir$ to c>ry ! salts4 ,:at has be5 ! s\rce ( ^! salts8 ,great ,salt ,lake is n1 z suppos$ by "s1 a remnant ( an ocean once cov]+ ! region4 ,briefly1 ! explanation is z foll[s3 ,at "o "t1 :5 ! climate 0 moi/]1 ! bas9 n[ only 9 "p occupi$ by ! lake 0 fill$ to ov]fl[+ ) an outlet nor? into ! ,snake & ,columbia riv]s4 ,t great body ( wat] 7call$ ,lake ,bonneville7 cov]$ ne>ly #bj1jjj squ>e miles & its dep? 0 ab\t #a1jjj feet deep] ?an n[1 ! pres5t dep? be+ v small4 ,because x _h an outlet t lake 01 ( c\rse1 fre%4 ,bea*es & %ore l9es #a1jjj feet above ! pres5t lake1 & at v>i\s l[] levels1 are /ill wond]fully well pres]v$4 ,:51 due to climatic *ange1 evaporation exce$$ intake by /reams1 ! outlet 0 cut (f4 ,b sl[ly1 z ! lake %rank1 /reams 7especially ! ,jordan ,riv]7 c>ri$ a little salt 9 solution1 ! p]c5tage ( salt increas+ until ! pres5t /age has be5 rea*$4 ,9 a real s5se1 mu* ( ! salt 0 once 9 ! sea1 because x has be5 dissolv$ out ( /rata :i* accumulat$ "u sea wat] long be=e ! bas9 ( ,great ,salt ,lake came into exi/5ce4 ,ano!r fam\s lake1 :i* also occupies "p ( a bas9 due to fault+1 is ,lake ,tahoe 9 ! ,si]ra ,nevada ,m\nta9s1 ne> ,truckee1 ,cali=nia4 ,?is lake1 ^: l5g? is #ba miles1 & wid? #ab miles1 lies #f1bbe feet above sea level4 ,on almo/ all sides /eep m\nta9s rise sev]al ?\s& feet above its wat]s4 ,its great dep? ( #a1fce feet makes x1 s f> z kn[n1 ! second deepe/ lake 9 ,nor? ,am]ica1 ,crat] ,lake1 ,oregon1 only outrank+ x4 ,! wat] is exce$+ly cle>4 ,an exp]im5t "s ye>s ago %[$ t a :ite disk eight in*es 9 diamet] c\ld actually be se5 ?r\gh a ?ickness ( #baf feet ( its wat]4 ,! /atem5t sometimes made t ',tahoe is an old volcanic crat]' is n true4 ,! region ab\t ! lake %[s evid5ces ( volcanic activity ( v>i\s k9ds1 & ! lake wat]s !mselves h probably be5 damm$ at times by outp\r+s ( lava4 ,a lava fl[ appe>s to h tempor>ily fill$ ! outlet *annel bel[ ,tahoe ,city4 ,! lake1 h[ev]1 lies 9 a /ructural depression--a dropp$ 7fault7 block 9 ! e>?'s cru/4 7,u4 ,s4 ,geological ,survey47 ,! bas9 ( ! l>ge/ lake 9 ! _w--! ,caspian ,sea--has result$ f w>p+ ( ! e>?'s cru/4 ,x has an area ( #agj1jjj squ>e miles1 a maximum dep? ( #c1bjj feet1 & its surface is ab\t #ij feet bel[ sea level4 ,! composition ( its wat] & "s ( its animal life indicate t x 0 once an arm ( ! sea4 ,x has be5 deta*$ or cut (f by an upw>p ( ! l& betwe5 x & ! ,black ,sea region4 ,if ?is great lake is a cut-(f arm ( ! sea1 ) no outlet1 h[ d we expla9 ! fact t its sal9ity is mu* less ?an t ( ! ocean8 ,t[>d ! nor?1 :]e x is %all[ & f$ by s mu* riv] wat]1 x is1 9 fact1 almo/ fre% wat]4 ,ev5 ! s\!rn "o-half c>ries n ov] #a p] c5t ( salt4 ,! explanation is t a /eady curr5t passes ?r\gh a n>r[ passageway into a gulf or bay on its ea/]n side :]e evaporation is mu* great] ?an ov] ! g5]al surface ( ! ,caspian4 ,! salt is1 !re=e1 gradually accumulat+ at ! e/imat$ rate ( #cej1jjj tons p] day 9 ?is gulf1 :ile ! sea itself is becom+ fre%]4 ,! bas9 ( ,lake ,*ampla91 ab\t #ajj miles long1 0 occupi$ by tidewat] geologically v rec5tly 7t is1 s9ce ! ,ice ,age71 b x has be5 cut (f by uplift ( ! l& on ! nor?1 s9ce :i* "t ! wat]s ( ! lake h be5 completely r9s$ out & fre%5$4 ,_m lake bas9s directly result f volcanic action4 ,9 _m p>ts ( ! _w lakes1 usually ( small size1 occupy crat]s ( volcanoes z1 = example1 9 ! ,eifel region ( ,g]many1 ! ,auv]gne di/rict ( ,france1 & ne> ,rome & ,naples 9 ,italy4 ,su* a lake ( exceptional int]e/ fills "p ( ! great crat]1 sev]al ?\s& feet deep1 :i* result$ f ! explosion ( ,mt4 ,katmai1 ,alaska1 9 #aiab4 ,! wat] ( ?is lake1 m ?an a mile wide & ( unkn[n dep?1 is hot4 ,"o ( ! mo/ unique & beautiful lakes ( ! _w is ,crat] ,lake 9 ! ,cascade ,m\nta9s ( s\!rn ,oregon4 ,x p>tly fills a great1 ne>ly circul> hole1 six miles 9 diamet]1 ) a maximum dep? ( ab\t #d1jjj feet1 9 ! top ( a m\nta9 7,plate #aa74 ,! lake is ov] five miles 9 diamet] & ne>ly #b1jjj feet deep1 mak+ x ! deepe/ 9 ,nor? ,am]ica4 ,its surface is ab\t #f1bjj feet above sea level4 ,precipit\s rock walls ris+ #ejj to #b1jjj feet completely encircle ! lake1 ! ma9 body ( ^: wat] is ( a m>vel\s deep1 sapphire-blue color1 :ile ! %all[ portions ar\nd "s ( ! %ore are ( em]ald-gre54 ,crat] ,lake has v little intake except direct ra9fall & sn[fall1 & its wat] is fre%4 ,! great hole 0 n produc$ by an explosion l t ( ,katmai1 b r by ! s9k+ ( ! top ( a once mu* great] m\nta94 ,t ! m\nta9 0 once ab\t ! size & %ape ( ,mt4 ,%a/a is prov$ by ! fact t deep glaciat$ valleys lead up ! slopes & end abruptly at ! v rim ( ! pres5t m\nta94 ,obvi\sly ^! valleys 7 sc\r$ out 9 rec5t geologic "t by glaci]s ^: s\rces 7 sev]al ?\s& feet up on a =m] cone-%ap$ m\nta94 ,t ! m\nta9 top sank r ?an explod$ is prov$ by ! abs5ce ( volcanic dbris ov] ! sides & base ( ! m\nta94 ,/ill ano!r way by :i* lakes are =m$ by volcanic action is by /reams ( lava block+ valleys4 ,! fam\s ,sea ( ,galilee 9 ,pale/9e 0 ?us =m$ by a /ream ( lava1 :i* geologically rec5tly fl[$ d[n f ! ea/ into ! ,jordan ,valley & across x1 :]e x cool$ to =m a dam pond+ ! wat]s ( ! ,jordan ,riv]4 ,because ! riv] fl[s ?r\gh ! lake1 its wat] is fre%4 ,"o ( ! mo/ rem>kable facts ab\t ?is lake is t its surface lies ne>ly #gjj feet bel[ sea level4 ,a numb] ( lava-dam lakes are kn[n 9 ! ,si]ra ,nevada & ,cascade ,m\nta9s4 ,a v int]e/+ case ( a lake bas91 =m$ by cutt+ (f an arm ( ! sea )\t any movem5t ( ! e>?'s cru/1 is ! ,salton ,s9k ( s\!rn ,cali=nia4 ,?is bas91 _m miles long & wide1 lies bel[ sea level1 its l[e/ po9t be+ #bhg feet bel[ tide4 ,! ,gulf ( ,cali=nia =m]ly rea*$ mu* f>!r nor? & into ,cali=nia :]e x cov]$ ! site ( ! ,salton ,s9k4 ,gradually ! ,colorado ,riv]1 always load$ ) s$im5t1 built a broad delta deposit "r across ! gulf1 ! nor!rn end ( :i* ?us became cut (f1 leav+ a big salt lake4 ,b ! riv] fl[$ into ! gulf1 :ile 9 ! dry climate ! evaporation 0 great en\gh to gradually dry away ! salt lake4 ,?is 0 ! condition ( ?+s until #aijd1 :5 mu* ( ! riv] at a "t ( flood got out ( control &1 foll[+ ! g5]al c\rse ( a great irrigat+ canal1 x fl[$ = sev]al ye>s into ! l[e/ "p ( ! ,salton ,s9k1 p>tly fill+ x to =m a lake #de miles long1 #ag miles wide1 & #hc feet deep4 ,s9ce #aijg ! lake has be5 notably decreas+ 9 size1 & x may entirely disappe>4 ,o!r ways by :i* lakes1 mo/ly relatively small ones1 may develop are by l&slides block+ valley dra9ages2 by /reams cutt+ across w9d+ curves leav+ s-call$ oxb[ lakes :i* are common1 = example1 along ! l[] ,mississippi ,riv]2 by wave & w9d action along %ores ( lakes or sea2 by fill+ s-call$ s9k holes :i* result f dissolv+ or fall+ 9 ( ro(s ( caves2 & by beav]s ?r\gh ^: indu/ry dams are built across valleys or /reams4 ,"s ( ! mo/ common ways by :i* lakes may be de/roy$ are ! foll[+3 by be+ fill$ ) s$im5t c>ri$ 9 by /reams1 or by vegetation1 or by bo?2 by cutt+ d[n outlets2 by evaporation due to a *ange 9 climate2 by removal ( ! ice dam 9 c]ta9 types ( glacial lakes2 & by movem5ts or w>p+ ( ! e>?'s cru/4 ,,*apt] ,,xii ,,h[ ,,! ,,e>? ,,may ,,h ,,orig9at$ ,! problem ( ! orig9 ( ! e>? is ess5tially a/ronomical r ?an geological1 because geological hi/ory is consid]$ to h begun :5 common e>? processes1 su* z erosion1 deposition1 & transportation ( s$im5ts1 etc41 7 br\ght into play4 ,x is q c]ta91 h[ev]1 t ! e>? 9 its pregeologic /ate gradually m]g$ into its geological condition4 ,= ?is reason ! geologi/ is int]e/$ 9 ! m important doctr9es or hypo!ses :i* h be5 put =? to acc\nt = ! orig9 ( ! e>?4 ,9 fact1 "o ( ! few hypo!ses :i* mu/ be tak5 s]i\sly is l>gely ! "w ( a geologi/4 ,! mo/ acceptable hypo!sis n only be/ satisfies ! facts reg>d+ ! e>?'s a/ronomical relation%ips1 b also be/ h>monizes ) our k ( ! olde/ kn[n rocks & _! hi/ory4 ,s9ce ! problem ( ! orig9 ( ! e>? is an ess5tial "p ( ! problem ( ! orig9 ( ! sol> sy/em1 ! foll[+ well-kn[n facts %\ld be cle>ly 9 ! m9d ( ! read]4 ,eight planets1 includ+ ! e>?1 revolve 9 ne>ly circul> pa?s ar\nd ! c5tral sun1 ^: diamet] is #hff1jjj miles4 ,! radius ( ! sol> sy/em is at lea/ #b1hjj1jjj1jjj miles1 ?is be+ ! di/ance ( ! out]mo/ kn[n planet 7,neptune7 f ! ,sun4 ,neptune requires #afd ye>s = a trip ar\nd ! sun1 :ile ! e>?1 :i* av]ages ab\t #ic1jjj1jjj miles f ! sun1 makes its circuit once a ye>4 ,! planets all revolve ar\nd ! sun 9 ! same direction1 & 9 ne>ly ! same plane4 ,! sun & all eight planets rotate on _! axes 9 ! same direction1 ! e>?'s rotation be+ accompli%$ e tw5ty-f\r h\rs4 ,mo/ ( ! planets h "o or m small] bodies call$ satellites revolv+ ab\t !m1 su* z ,e>?1 ) its "o satellite 7! moon71 & ,saturn1 ) its eight satellites1 etc4 ,x is well kn[n t ?is sol> sy/em is only a v small "p ( ! va/ univ]se1 z %[n by ! facts t no /> is ne>] ! e>? ?an sev]al trillion miles1 & t "s />s are s f> away t light travel+ at ! rate ( #ahf1jjj miles p] second requires a ?\s& ye>s to rea* ! e>?6 ,t[>d ! end ( ! eighte5? c5tury ! fam\s nebul> or r+ hypo!sis 0 set =? by ! a/ronom] nam$ ,laplace4 ,?is assumes an orig9al v hot inc&esc5t mass ( gas sph]oidal 9 %ape & great] 9 diamet] ?an ! pres5t sol> sy/em4 ,?is mass rotat$ 9 ! direction ( rotation ( our sun & its planets4 ,loss ( heat by radiation caus$ ! mass to %r9k1 & ?is 9 turn n only made x rotate fa/]1 b also caus$ ! c5trifugal =ce 7i4e41 ! =ce ^: direction 0 f ! c5t]7 9 its equatorial portion to gradually become /rong]4 ,f9ally a "t came :5 ! =ce ( gravity 7i4e41 ! =ce ^: direction 0 t[>d ! c5t]7 & ! c5trifugal =ce became equal & a r+ 0 left 7n ?r[n7 (f1 :ile ! re/ ( ! mass ( gas cont9u$ to %r9k4 ,aft] a "t ! mat]ial ( ! r+ collect$ to =m ! out]mo/ planet4 ,! o!r planets 7 simil>ly =m$ f o!r r+s :i* 7 left (f z contraction ( ! great mass ( gas w5t on4 ,! sun repres5ts ! rema9d] ( ! great mass ( rotat+ gas4 ,:at is ! be>+ ( ?is nebul> hypo!sis ^u ! e>ly geological hi/ory ( ! e>?8 ,accord+ to ! hypo!sis ! e>? mu/ once h be5 mu* m highly heat$ & l>g] ?an n[4 ,x cond5s$ to a liquid & !n x cool$ en\gh to p]mit ! =mation ( a solid cru/ ov] a liquid int]ior4 ,x !n _h a hot d5se atmosph]e conta9+ all ! wat] ( ! e>? 9 ! =m ( vapor1 & ?is atmosph]e /eadily became ?9n] due to absorption by ! e>?4 ,:5 ! pressure & temp]ature conditions became favorable1 mu* ( ! wat] vapor cond5s$ to =m ! ocean & ! atmosph]e gradually *ang$ to its pres5t condition4 ,accord+ to ?is view ! olde/ rocks ( ! e>? mu/ h be5 igne\s because !y result$ f ! solidification ( ! out] "p ( ! molt5 globe4 ,)9 rec5t ye>s c]ta9 s]i\s objections to ! nebul> hypo!sis h be5 rais$1 & ,*amb]l9 & ,m\lton h =mulat$ ! planetesimal or spiral hypo!sis z an attempt at a m rational explanation ( ! orig9 ( ! sol> sy/em4 ,"s ( ! objections to ! old] doctr9e are t among ! _m ?\s&s ( kn[n nebul 9 ! univ]se v few only are ( ! ,laplacian or r+ type1 :ile spiral =ms are abundant4 ,spectroscopic /udy %[s t ! nebul are n gase\s1 b made up ( ei!r liquid or solid p>ticles1 & t ! leav+ (f ( r+s w\ld necessitate ! assumption ( an int]mitt5t process :i* c\ld sc>cely h op]at$ "u ! conditions ( ! hypo!sis4 ,illu/ration3 ,plate #i4--7;a7 ,molt5 ,lava ,fl[+ ,ov] a ,cliff ,into ,wat] 9 ! ,hawaiian ,isl&s4 7,aft] ,dill]1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #i4--7;b7 ,dikes ( ,granite 7,light ,gray7 ,cutt+ an ,old ,d>k ,rock4 ,:ile ! granite on ! "r 0 be+ =c$ 9 molt5 condition upw>d into ! e>?'s cru/1 tongues ( x 7dikes7 7 s5t (f into ! adjac5t rock4 7,photo by ,h[e1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #aj4--7;a7 ,lass5 ,peak1 ,nor!rn ,cali=nia1 9 ,eruption ,augu/ #bb1 #aiad4 ,! great cl\d ( /eam & volcanic a% rose sev]al miles4 ,?is is ! only active volcano 9 ! ,unit$ ,/ates prop]1 & x is n[ includ$ 9 ,lass5 ,volcano ,national ,p>k4 7,by p]mission ( ,r4 ,e4 ,/9son1 ,r$ ,bluff1 ,cal47 ,illu/ration3 ,plate #aj4--7;b7 ,devil's ,t[]1 ,wyom+4 ,?is great mass ( rock 0 =c$ 9 molt5 condition ?r\gh /rata :i*1 because ( _! weakness1 h be5 erod$ away all ar\nd ! h>d igne\s rock4 ,?is is probably ! core or neck ( a =m] volcano4 7,photo by ,d>ton1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,fig4 #ca4--;,diagram %[+ ! orig9 & "* ( a spiral nebula accord+ to ! planetesimal hypo!sis ( ! orig9 ( ! sol> sy/em4 7,modifi$ aft] ,m\lton47 ,any?+ l a full und]/&+ ( ! planetesimal hypo!sis w\ld be difficult to obta91 &1 9 ! brief space at our disposal1 we %all attempt to make cle> only a few ( ! sali5t po9ts4 ,accord+ to ?is hypo!sis ! sol> sy/em 01 dur+ a previ\s /age ( its evolution1 a great1 flat1 spiral nebula1 made up ( f9ely divid$ solid or possibly liquid p>ticles call$ planetesimals1 among :i* 7 scatt]$ "s l>g] knots or masses4 ,ea* t9y p>ticle & l>g] mass or knot is consid]$ to h travel$ 9 its own p>ticul> orbit or pa? ab\t a c5tral v l>ge mass--! future sun4 ,x is ev5 sugge/$ t ! spiral nebula orig9at$ by disruption ( "o /> by a swift-mov+ pass+ />4 ,ea* disrupt$ p>ticle & l>ge mass at fir/ />t$ /raight = ! l>ge pass+ />1 b because ( *ange ( position ( ! latt] ! p>ticles & l>g] masses 7 gradually pull$ ar\nd s t _! pa?s curv$ into spirals4 ,because ( cross+ ( pa?s1 ! l>g] masses or knots gradually increas$ 9 size by accretion ( ! small p>ticles or planetesimals4 ,meteors 7s-call$ %oot+ />s7 :i* n[ /rike ! e>? are ?\ght to be disrupt$ mat]ials /ill be+ ga!r$ 91 ?\gh v sl[ly at pres5t4 ,aft] ! pass+ /> got well out ( range1 ! spiral pa?s ( ! disrupt$ masses gradually *ang$ to ne>ly circul>1 due to a wrapp+-up process ar\nd ! c5tral body 7sun7 :i* !n controll$ ! movem5ts ( ! bo? l>g] masses 7future planets7 & small masses 7planetesimals74 ,let u n[ inquire briefly into ! be>+ ( ?is planetesimal hypo!sis ^u ! e>ly geological hi/ory ( ! e>?4 ,accord+ to ?is doctr9e ! e>? 0 nev] 9 ! =m ( a highly heat$ gas1 nor 0 x ev] necess>ily hott] ?an n[4 ,in/ead ( beg9n+ z a mu* l>g] body :i* has gradually dim9i%$ 9 size1 ! e>? /eadily grew1 up to a c]ta9 /age1 by +a!r+ ( planetesimals4 ,increase 9 size caus$ ! =ce ( gravity to increase & ?is caus$ n only /eady contraction ( ! e>?'s matt]1 b also a developm5t ( great] int]nal heat4 ,! e>? has be5 gett+ small] ev] s9ce ! =ce ( compression has pr$om9at$ ov] ! build+-up process1 because ( ! dim9i%+ supply ( planetesimals4 ,due to /eadily increas+ int]nal pressure & heat ! v>i\s gases1 includ+ wat] vapor1 h be5 driv5 out ( ! e>? to =m an atmosph]e :i* has gradually become l>g] & d5s]4 ,aft] suffici5t accumulation ( wat] vapor1 cond5sation & ra9fall took place2 ! wat]s ( ! e>? began to ga!r to =m ! oceans2 & ! ord9>y geologic processes ( erosion & deposition ( /rata 7 initiat$4 ,accord+ to ?is view /ratifi$ rocks c\ld h be5 =m$ v e>ly 9 ! hi/ory ( ! e>?1 & 9 ?is connection x is int]e/+ to note t ! olde/ kn[n rocks are actually ( s$im5t>y orig94 ,,*apt] ,,xiii ,,v ,,anci5t ,,e>? ,,hi/ory 7,ar*eozoic & ,prot]ozoic ,eras7 ,we %all n[ consid] ! old] rocks ( ! ,e>?1 includ+ ^? ( ,ar*eozoic1 ,prot]ozoic1 & ,paleozoic ages4 ,:at are ! sali5t po9ts 9 ! v e>ly hi/ory ( ! e>? 7n includ+ ! evolution ( organisms7 %[n by ^! v anci5t rocks8 ,beg9n+ ) ! olde/ kn[n rocks1 x w be our purpose to trace out ! pr9cipal record$ ev5ts ( e>? hi/ory 9 ! regul> ord] ( _! occurr5ce4 ,z 9 human hi/ory1 s 9 e>? hi/ory ! record$ ev5ts ( v e>ly times are fewe/ & mo/ difficult ( all to und]/&4 ,9 spite ( ?is difficulty x is be/ to beg9 ) ! olde/ kn[n rocks or1 z ,le ,conte has said1 to foll[ ! natural ord] ( ev5ts4 ,?is has ! great advantage ( br++ out ! philosophy ( ! hi/ory--! law ( evolution4 ,because ( limitation ( space we %all give special att5tion to ! physical hi/ory ( ,nor? ,am]ica1 b ! g5]al pr9ciples br\ght out apply almo/ equally well to ! o!r cont95ts4 ,! ,ar*eozoic rocks conta9 ! e>lie/ kn[n records ( geological hi/ory1 or1 9 o!r words1 ! olde/ record$ ord9>y geological processes su* z wea!r+ & erosion1 deposition ( /rata1 igne\s activity1 etc4 ,al?\gh we are "h deal+ ) ! mo/ obscure records ( any great rock sy/em1 p>tly because ! rocks h be5 s pr(\ndly alt]$ 7metamorphos$71 & p>tly because ( ! abs5ce ( any?+ l def9itely det]m9able fossils1 x is1 nev]!less1 true t c]ta9 v important conclusions h be5 rea*$ reg>d+ ?is v anci5t geological era4 ,among ! v olde/ ( all kn[n rocks ( ,nor? ,am]ica are ! ,gr5ville /rata1 s nam$ f a t[n 9 ! ,/4 ,lawr5ce ,valley4 ,9 fact1 no rocks else:]e 9 ! _w h be5 prov$ to be m anci5t4 ,! ,gr5ville s]ies consi/s ( a great mass ( s$im5ts 7/rata7--orig9al muds1 s&s1 & limes--:i* 7 deposit$ lay] ^u lay] "u wat] 7,plate #ab74 ,! widespread ext5t & "* ( ! s]ies 9 s\!a/]n ,canada & ! ,adirondacks1 & m ?an likely f> beyond ^! limits1 make x c]ta9 t ! ,gr5ville /rata 7 accumulat$ on ! bottom ( a relatively %all[ sea v mu* z s$im5ts are n[ pil+ up on %all[ sea bottoms4 ,?us1 ! mo/ anci5t def9itely kn[n condition ( ! region :]e ! ,gr5ville /rata are expos$ 0 an expanse ( ! sea cov]+ ! :ole area4 ,:]ev]1 9 o!r p>ts ( ! _w1 ! ,ar*eozoic rocks h be5 /udi$1 /ratifi$ rocks also seem to be ! v olde/ :i* are recognizable1 b up to ! pres5t "t no su* rocks h be5 prov$ to be any old] ?an1 or ev5 z old z1 ! ,gr5ville s]ies4 ,x may occur to ! read] to ask1 h[ long ago did ! ,gr5ville ocean exi/8 ,!re are grave difficulties 9 ! way ( answ]+ ?is "q 9 t]ms ( ye>s s9ce we h no?+ l an exact /&>d = su* a measurem5t or comp>ison4 ,al?\gh we mu/ conc$e t n ev5 approximate figures c be giv51 x c1 nev]!less1 be demon/rat$ by sev]al indep5d5t l9es ( reason+ t ! "t mu/ be measur$ by at lea/ t5s ( millions ( ye>s1 a v cons]vative e/imate ( ! m9imum "t :i* mu/ be all[$ be+ ab\t #ej million ye>s4 ,9 any case1 ! "t is s utt]ly inconceivable to u t ! important ?+ to be> 9 m9d is t ! great well-kn[n ev5ts ( e>? hi/ory1 :i* h transpir$ s9ce ! exi/5ce ( ! ,gr5ville ocean1 require a lapse ( _m millions ( ye>s1 z %[n by revolution>y *anges 9 geographic & geologic conditions su* z ! long p]iods ( erosion1 ! enorm\s accumulations ( s$im5t1 ! repeat$ spread+ out & disappe>ance ( sea wat] ov] _m portions ( ! e>?1 & ! build+ up & te>+ d[n ( great m\nta9 ranges at v>i\s times4 ,! ideas "h express$ w be mu* bett] appreciat$ by ! read] aft] foll[+ ?r\gh ! sali5t po9ts 9 ! hi/ory ( ,nor? ,am]ica z set =? 9 ! succe$+ pages4 ,aga91 ! read] may ask1 by :at l9e ( reason+ d we conclude t ^! /ratifi$ rocks are s exce$+ly anci5t8 ,all rocks ( ,ar*eozoic ,age1 includ+ /rata z well z c]ta9 y\ng] igne\s rocks 7see bel[71 inv>iably occupy a basal position 9 relation to all o!r rock sy/ems4 ,!y con/itute a complex lot ( cry/all9e metamorphic rocks1 comb9+ c]ta9 *>act]i/ics :i* lie bel[ ! base ( ! det]m9$ s$im5t>y succession4 ,:]e rocks ) ! *>act]i/ics ( ! ,ar*eozoic are sep>at$ f ! olde/ ,paleozoic 7,cambrian7 /rata by ! great s$im5t>y or metamorphic sy/em kn[n z ! ,prot]ozoic 7see bel[71 we may be sure t we are deal+ ) ,ar*eozoic rocks4 ,if ! s]ies ( rocks 9 "q belongs 9 ! ,ar*eozoic sy/em1 all t rema9s is to det]m9e its age position 9 t sy/em4 ,?is c usually readily be done because :]ev] !y h be5 /udi$ ! ,ar*eozoic rocks may be subdivid$ into two gr\ps ( rocks1 a s$im5t>y & an igne\s4 ,:]e ! igne\s rocks1 ma9ly granites & relat$ types1 occur associat$ ) ! s$im5t>y rocks 7e4g41 ,gr5ville71 !y v cle>ly 7 =c$ or intrud$1 :ile molt51 into ! s$im5t>y rocks1 ?us prov+ ^! latt] to be ! old]4 ,s9ce ! ,ar*eozoic /rata ( ! ,adirondack ,m\nta9s1 s\!a/]n ,canada1 & also all1 or ne>ly all1 o!r kn[n di/ricts are mo/ly badly di/urb$1 tilt$1 & m or less b5t or fold$1 & s9ce nei!r top nor bottom ( ! piles ( /rata has ev] be5 recogniz$ z su*1 x is impossible to give any?+ l an exact figure = ! ?ickness ( ! s]ies4 ,cont9u\s successions ( /rata h1 h[ev]1 be5 obs]v$ 9 en\gh places to %[ t !y 7 commonly deposit$ lay] ^u lay] to a ?ickness ( at lea/ "s t5s ( ?\s&s ( feet4 ,a ?ickness ( ov] #ajj1jjj feet has be5 report$ f s\!a/]n ,canada4 ,! cle> implication is t ! ,ar*eozoic sea :i* receiv$ s$im5ts mu/ h exi/$ = a va/ l5g? ( "t :i* mu/ be measur$ by at lea/ "s millions ( ye>s1 because 9 ! light ( all our k reg>d+ ! rate ( accumulation ( s$im5ts a v long "t 0 necess>y = ! pil+ up ( su* ?ick masses ( /rata4 ,x does n1 h[ev]1 necess>ily foll[ t ! ,gr5ville ocean 0 _m ?\s&s ( feet deep :]e deposition took place4 ,9 fact1 ! v "* ( ! orig9al s$im5ts 7muds1 s&s1 & limes7 cle>ly indicates t ! ,ar*eozoic sea 9 :i* !y accumulat$ 01 = mo/ "p at lea/1 ( %all[ wat] because su* s$im5ts h r>ely1 if ev]1 be5 c>ri$ out into an ocean ( deep wat]4 ,! great ocean abysses ( to-day are n receiv+ any appreciable am\nt ( l&-d]iv$ s$im5t4 ,?us we are =c$ to conclude t 9 ,ar*eozoic "t1 z well z _m times 9 lat] ages1 ! %all[ sea bottom gradually sank :ile ! s$im5ts accumulat$4 ,ev5 m conclusive pro( ( su* subsid5ce has be5 obta9$ f ! /udy ( s-call$ fold$ m\nta9 ranges ( ,paleozoic & lat] "t1 an excell5t example be+ ! ,appala*ian ,range4 ,hav+ e/abli%$ ! s$im5t>y orig9 & great antiquity ( ! ,gr5ville s]ies1 we are l$ to ! int]e/+ & important conclusion t ^! olde/ kn[n rocks are n ! mo/ anci5t :i* ev] exi/$1 because ! ,gr5ville /rata mu/ h be5 deposit$ lay] ^u lay]1 ^u a floor ( /ill old] rocks4 ,if su* /ill old] rocks are any:]e expos$ to view1 !y h nev] be5 recogniz$ z su*4 ,aga91 ! fact t ! mo/ anci5t kn[n rocks 7 deposit$ "u wat] c>ries ) x ! coroll>y t !re mu/ h be5 l&s at no great di/ances f ! areas ( deposition because1 !n z n[1 su* s$im5ts z muds & s&s c\ld h be5 d]iv$ only f ! we> or erosion ( l&s1 & h be5 deposit$ 9 lay]s "u wat] adjac5t to ^? l&s4 ,b we are utt]ly 9 ! d>k reg>d+ any k ( ! location or "* ( su* v anci5t l&s4 ,! mo/ anci5t kn[n /rata1 z we see !m to-day1 d n look l ord9>y s$im5ts su* z %ales1 s&/ones1 & lime/ones4 ,!y h be5 pr(\ndly *ang$ f _! orig9al condition1 t is to say1 !y h und]gone metamorphism4 ,! ,ar*eozoic /rata n[ expos$ to view 7 =m]ly buri$ at lea/ "s miles bel[ ! e>?'s surface1 ! ov]ly+ y\ng] rocks hav+ s9ce be5 remov$ by erosion ?r\gh ! millions ( ye>s ( "t4 ,f> bel[ ! e>?'s surface1 "u conditions ( relatively high temp]ature1 pressure1 & moi/ure1 ! mat]ials ( ! /rata 7 completely cry/alliz$ into v>i\s m9]als4 ,! surfaces ( sep>ation ( ! v anci5t lay]s ( s$im5t are /ill usually m or less cle>ly pres5t 7,plate #ab74 ,orig9al lime/one has be5 *ang$ into cry/all9e lime/one or m>ble2 s&/one has be5 *ang$ into qu>tzite1 & %ale1 s&y %ale1 & %aly s&/one h be5 *ang$ into v>i\s s*i/s & gneisses4 ,9 we/]n ,ont>io !re are also /ratifi$ rocks 7call$ ! ,keewat9 s]ies7 :i* seem to be ( ab\t ! same age z ! ,gr5ville /rata f>!r ea/4 ,a po9t ( special int]e/ 9 connection ) ! ,keewat9 /rata is ! pres5ce ( lay]s ( lava 9 portions ( ! s]ies1 ?us prov+ t molt5 rock mat]ials 7 p\r$ out on ! e>?'s surface dur+ ! mo/ anci5t kn[n era ( ! e>?'s hi/ory4 ,aft] ! accumulation ( ! v anci5t ,ar*eozoic s$im5ts igne\s activity took place on gr& scales :5 great masses ( molt5 rock 7 =c$ 7intrud$7 into ! s$im5ts f bel[4 ,masses ( molt5 mat]ials are kn[n to h be5 ?us intrud$ at sev]al diff]5t times1 b ( ^! ! mo/ common by f> cool$ to =m a great s]ies ( granite & closely relat$ rocks4 ,! g5]al effect 0 to break ! old /rata up into pat*es or masses ( v>y+ sizes z cle>ly %[n by ! pres5t di/ribution & modes ( occurr5ce ( ^! igne\s rocks4 ,9 mo/ cases ! /rata 7 pu%$ aside by1 or tilt$ or dom$ ov]1 ! upwell+ molt5 floods--9 _m cases ! molt5 mat]ials 71 "u great pressure1 intimately =c$ or inject$ into ! /rata2 num]\s l>ge & small masses ( /rata 7 caught up or envelop$ 7z inclusions7 9 ! molt5 floods2 9 "s cases !re 0 local dige/ion or assimilation ( ! /rata by ! molt5 mat]ials1 :ile 9 /ill o!r places l>ge bodies ( /rata seem to h be5 left practically intact & undi/urb$4 ,su* igne\s rocks1 :i* are v widespread1 are all ( ! plutonic or deep-seat$ types2 t is1 !y 7 nev] =c$ up to ! e>?'s surface l lavas1 b !y solidifi$ at consid]able dep?s 7at lea/ "s ?\s&s ( feet7 bel[ ! surface4 ,we see !m expos$ to-day only because a trem5d\s am\nt ( ov]ly+ rock mat]ials has be5 remov$ by erosion4 ,^! igne\s rocks are g5]ally easily di/+ui%$ f ! old s$im5ts ( ,gr5ville age because ( _! m g5]al homog5eity 9 l>ge masses1 & _! lack ( %>ply def9$ b&s or lay]s ( v>y+ composition4 ,! fact t ! m9]als h always cry/alliz$ to =m m$ium to co>se-gra9$ rocks %[s t ^! rocks solidifi$ "u deep-seat$ conditions1 s9ce x is well kn[n t surface fl[s 7lavas7 are mu* f9] gra9$ commonly ) m or less ( ! rock n cry/alliz$ at all4 ,sl[ cool+ "u great pressure favors m complete cry/allization ) gr[? ( l>g] cry/als4 ,z we h j le>n$1 ! v "* & /ructure ( ! ,ar*eozoic rocks n[ expos$ to view %[ conclusively t !y 7 =m]ly deeply buri$1 & ! inf]5ce is p]fectly pla9 t ! ov]ly+ rock mat]ials 7 remov$ by erosion4 ,pr(\nd erosion ( any l& mass means t ! l& mu/ h /ood well above sea level1 & ?us we come to ! important conclusion t ! great mass ( ,ar*eozoic rocks 7bo? /rata & igne\s rocks7 7 uprais$ well above sea level4 ,j :5 ! uplift occurr$ _c be positively /at$1 b 9 e region :]e ! matt] has be5 /udi$ x took place be=e ! /rata ( ! next geological era began to deposit z %[n by ! fact t su* lat] /rata re/ ^u ! pr(\ndly erod$ surface ( ! ,ar*eozoic rocks4 ,su* an erosion surface1 call$ an uncon=mity1 m>ks a gap 9 ! geological record ( ! di/rict :]e x occurs4 ,!re is mu* to support ! view t ! uplift 0 concomitant ) ! great igne\s intrusions1 especially ! granite4 ,x is reasonable to believe t ! same great =ce :i* caus$ ! well+ up ( su* trem5d\s bodies ( liquid rock into ! e>?'s cru/ might easily h caus$ a decid$ uplift ( a :ole l>ge region1 b ev5 s ! process mu/ h be5 geologically sl[4 ,9 reg>d to ! height ( ^? anci5t l&s1 ! "* ( ! topography1 & ! dra9age l9es we are z yet utt]ly 9 ! d>k4 ,! fact t _m ?\s&s ( feet 9 ?ickness ( mat]ials 7 remov$ by erosion to expose ! once deeply buri$ rocks1 does n necess>ily imply t ! l&s at any "t _h great height1 because x is possible t :ile elevation sl[ly progress$1 mu* mat]ial 0 /eadily remov$ by erosion4 ,9 ! light ( our k ( ! orig9 & gr[? ( m\nta9 ranges ( lat] "t !re is little d\bt t at lea/ "s ( ! ,ar*eozoic l&s 7 rais$ to su* m\nta9 heights4 ,?us f> 9 our /udy ( ! ,ar*eozoic rocks att5tion has be5 ma9ly direct$ to s\!a/]n ,canada & ! ,adirondack m\nta9s1 :]e c>eful /udies h be5 made4 ,9 all p>ts ( ! _w :]e ! mo/ anci5t kn[n 7,ar*eozoic7 rocks h be5 /udi$ 9 detail ! same g5]al pr9ciples apply4 ,p>ticul> att5tion has be5 giv5 to ! ,ar*eozoic rocks s\? ( ,lake ,sup]ior1 & 9 ! ,pi$mont ,plateau ( ! ea/]n ,unit$ ,/ates4 ,9 ! accompany+ map ,ar*eozoic rocks are widely expos$ to view )9 ! areas %[n 9 black4 ,x has be5 e/imat$ t ,ar*eozoic rocks appe> at ! surface ov] ab\t "o-fif? ( ! l& area ( ! e>?4 ,:]e !y are n at ! surface x is believ$ t !y ev]y:]e exi/ "u cov] ( lat] rocks4 ,9 o!r words1 ,ar*eozoic rocks are consid]$ to be almo/ univ]sally pres5t ei!r at or "u ! e>?'s surface4 ,?is is true ( ! rocks ( no o!r age4 ,special m5tion %\ld be made ( ! f9e exhibitions ( ,ar*eozoic rocks 9 ,sc&9avia & ! ,highl&s ( ,scotl&4 ,illu/ration3 ,fig4 #cb4--,map %[+ ! surface di/ribution ( ,ar*eozoic & ,prot]ozoic rocks 9 ,nor? ,am]ica4 7,r$rawn by ! au?or aft] ,u4 ,s4 ,geological ,survey47 ,all kn[n evid5ce leads u to ! rem>kable conclusion t ! climate ( mu*1 or possibly all1 ( ,ar*eozoic "t 0 n fundam5tally diff]5t f t ( to-day4 ,!re mu/ h be5 wea!r+ ( rocks1 ra9fall1 & /reams mu* z at pres5t z prov$ by ! "* & composition ( ! /ratifi$ rocks :i* =m$ 9 t remote era4 ,! pres5ce ( graphite 7black lead7 9 cry/all9e flakes scatt]$ ?r\gh _m ( ! /rata %[s t ! climate mu/ h be5 favorable to "s =m ( life1 because graphite ?us occurr+ q c]ta9ly repres5ts ! rema9s ( organisms1 ?is matt] be+ m fully discuss$ 9 a succe$+ *apt]4 ,9 pass+ x may be /at$ t climatic zones 7 !n probably sc>cely if at all m>k$ (f1 z !y q c]ta9ly 7 n ev5 dur+ ,paleozoic "t4 ,"o ( ! great contributions ( geology to human k is t dur+ ! t5s ( millions ( ye>s f ,ar*eozoic times to ! pres5t ! e>?'s climate has und]gone no fundam5tal *ange or evolution4 ,9 ! e>li] ages !re 0 great] uni=mity ( climate ov] ! e>?1 &1 dur+ kn[n geologic "t !re h be5 r localiz$ relatively m9or fluctuations giv+ rise to glaci]s1 des]ts1 etc41 b !re has be5 no real evolution ( climate at all comp>able to ! m>vel\s evolution ( organisms--bo? animals & plants4 ,we %all n[ turn our att5tion briefly to a consid]ation ( ! second great subdivision ( geologic "t--! ,prot]ozoic era4 ,rocks ( ,prot]ozoic ,age comprise all ( ^? :i* 7 =m$ aft] ! ,ar*eozoic rocks & be=e ! deposition ( ! e>lie/ ,paleozoic 7,cambrian7 /rata1 ^! latt] be+ r def9itely recognizable because !y conta9 fossils *>act]i/ic ( ! "t4 ,cambrian /rata are1 9 fact1 ! olde/ rocks :i* conta9 any?+ l an abundance ( fossils1 s t ! sep>ation ( rocks ( ei!r ,ar*eozoic or ,prot]ozoic ,age f ! e>lie/ ,paleozoic is seldom difficult4 ,b h[ may we sep>ate ! ,prot]ozoic rocks f ! ,ar*eozoic8 ,fossils af=d u no aid :atev]1 because no det]m9able fossils h be5 f\nd 9 rocks z old ev5 z ! e>li] ,prot]ozoic4 ,! two great gr\ps ( v anci5t rocks d1 h[ev]1 %[ a numb] ( diff]5ces :i* mu/ be consid]$ toge!r4 ,?us1 igne\s rocks di/9ctly pr$om9ate 9 ! ,ar*eozoic1 :ile /ratifi$ rocks pr$om9ate 9 ! ,prot]ozoic4 ,all ,ar*eozoic /rata are ?or\ghly metamorphos$ 7*ang$ f _! orig9al condition71 :ile l>ge masses ( ! ,prot]ozoic /rata are only mod]ately metamorphos$1 or ev5 unalt]$1 & !re=e look mu* l ord9>y /rata ( lat] ages4 ,ar*eozoic rocks h almo/ inv>iably be5 notably de=m$ by m or less fold+1 tilt+1 etc41 :ile ! ,prot]ozoic rocks %[ relatively mu* less de=mation4 ,ano!r important crit]ion is ! fact t ! ,prot]ozoic rocks1 :]ev] !y h be5 /udi$ 9 relation to ! ,ar*eozoic rocks1 always re/ ^u a pr(\ndly erod$ surface ( ! latt]1 t is1 an uncon=mity sep>ates ! two great sets ( rocks4 ,?is erosion surface is ( /ill fur!r int]e/ because x is ! v olde/ "o kn[n1 none hav+ be5 recogniz$ )9 ! ,ar*eozoic gr\p itself4 ,ev5 :]e ! ,prot]ozoic /rata h be5 consid]ably metamorphos$ & de=m$1 ?is old erosion surface may be recogniz$1 & if ! rocks bel[ t surface possess ! *>act]i/ics ( ! ,ar*eozoic rocks z describ$ above1 ! two great v anci5t rock gr\ps may be di/+ui%$4 ,"o ( ! triumphs ( geology dur+ ! la/ #be to #cj ye>s has be5 ! recognition ( ! great rock gr\p 7,prot]ozoic7 betwe5 ! ,ar*eozoic & ,paleozoic1 ?us br++ to light ! records ( an era :i* la/$ _m millions ( ye>s4 ,! l5g? ( "t repres5t$ by ! ,prot]ozoic era is by _m believ$ to h be5 fully z long z all succe$+ eras--,paleozoic1 ,mesozoic1 & ,c5ozoic--comb9$4 ,tw5ty million ye>s w\ld be a v cons]vative e/imate = ! duration ( ! era4 ,:at is ! nature ( ! evid5ce z record$ 9 ! rocks :i* lead u to conclude t ! ,prot]ozoic era la/$ su* a va/ l5g? ( "t8 ,! great ?ickness ( ,prot]ozoic /rata 7ov] #cj1jjj feet 9 ! ,lake ,sup]ior region71 9 ! light ( :at we h already le>n$ reg>d+ ! pres5t rate ( we> 7erosion7 ( l&s & deposition ( ! erod$ mat]ials "u ord9>y conditions1 cle>ly implies millions ( ye>s ( "t = _! accumulation4 ,b ! ,prot]ozoic /rata z we n[ see !m are 9 mo/ places n a cont9u\s pile1 t is !y 7 n accumulat$ lay] ^u lay] )\t notable int]ruption4 ,?us1 ! ?ick ,prot]ozoic gr\p ( ! ,lake ,sup]ior region has be5 divid$ into f\r di/9ct1 ma9ly s$im5t>y s]ies sep>at$ f ea* o!r by erosion surfaces 7uncon=mities74 ,ea* erosion surface repres5ts a long "t :5 ! area 0 elevat$ & und]w5t pr(\nd we> be=e ! next s]ies ( /rata accumulat$ on ! worn surface4 ,t su* times ( erosion 7 geologically long is prov$ n only by ! pr(\nd alt]ation 7metamorphism7 ( "o set ( /rata be=e ano!r accumulat$1 b also by ! fact t granite1 :i*1 z we h le>n$1 is nev] expos$ except :]e mu* ov]ly+ mat]ial has be5 erod$1 actually =m$ p>ts ( surfaces ( e>li] ,prot]ozoic rocks ^u :i* lat] ones 7 deposit$4 ,9 ! ,lake ,sup]ior region !re are n only ?ree great erosion surfaces 7uncon=mities7 )9 ! ,prot]ozoic gr\p1 b also "o at ! base sep>at+ x z a :ole f ! ,ar*eozoic gr\p1 & ano!r at ! top sep>at+ x f ! ,paleozoic gr\p4 ,x is1 !re=e1 fair to conclude t ! am\nt ( "t 7millions ( ye>s7 repres5t$ by ^! great erosion int]vals 0 fully z great z ! "t ne$$ = deposition ( ! exi/+ ,prot]ozoic /rata4 ,9 ! ,lake ,sup]ior region ! old] ,prot]ozoic /rata are ne>ly all m or less fold$ & alt]$ 7metamorphos$71 & !y h be5 intrud$ by consid]able bodies ( molt5 rock1 mo/ly granite4 ,! lat] ,prot]ozoic /rata h be5 mu* less de=m$ & 9 _m cases !y are practically unalt]$4 ,9 ?is region a v rem>kable ev5t took place 9 late ,prot]ozoic "t4 ,?is 0 volcanic activity on a gr& scale4 ,we may ga9 "s idea ( ! /up5d\s & long-cont9u$ volcanic outp\r+s f ! fact t1 bas$ ^u actual measurem5ts ( ?ickness1 lava %eets1 av]ag+ ab\t #ajj feet ?ick1 p\r$ out "o ^u ano!r until a pile ab\t six miles high _h accumulat$4 ,9 p>ts ( ! ,gr& ,canyon ( ! ,colorado tilt$ ,prot]ozoic /rata may be se5 re/+ ^u ! pr(\ndly erod$ surface ( ! ,ar*eozoic rocks ( ! inn] gorge4 ,! ,prot]ozoic /rata1 #ab1jjj feet ?ick1 consi/ ( practically unalt]$ s&/ones1 %ales1 & lime/ones1 associat$ ) "s lay]s ( basaltic lava4 ,an erosion surface 7uncon=mity7 sep>ates ! :ole gr\p into two di/9ct s]ies1 & ! gr\p is sep>at$ f ! ov]ly+ ne>ly horizontal ,paleozoic 7,cambrian7 /rata 9 ! walls ( ! ,canyon by ano!r erosion surface4 ,m rec5tly ! ,prot]ozoic /rata s f9ely display$ 9 ! ,rocky ,m\nta9s ( ,montana & s\!rn ,canada h be5 /udi$4 ,^! /rata1 at lea/ two or ?ree miles ?ick1 are mo/ly unalt]$ s&/ones1 %ales1 & lime/ones1 associat$ ) "s metamorphic & igne\s rocks4 ,z usual1 ^! /rata re/ ^u ! erod$ ,ar*eozoic4 ,!y 7 m or less upturn$ & fold$ be=e deposition ( ! succe$+ ,paleozoic /rata4 ,satisfactory subdivisions h n yet be5 work$ out4 ,9 ,nor? ,am]ica mo/ ( ! areas %[n on ! accompany+ map conta9 m or less ,prot]ozoic rocks4 ,rocks ( ?is age are kn[n to "s ext5t 9 all cont95ts :]e _! g5]al relation%ips seem to be mu* l ^? ( ,nor? ,am]ica4 ,!y h p]haps be5 mo/ c>efully /udi$ 9 ,sc&9avia & ! ,highl&s ( ,scotl&1 :]e ! /rata portions are ab\t two miles ?ick4 ,! climate ( ,prot]ozoic "t mu/1 = mo/ "p1 h be5 ab\t l t ( to-day except1 ( c\rse1 = its mu* great] uni=mity ov] ! e>?4 ,ab\t a doz5 ye>s ago v typical glacial deposits 7 discov]$ )9 ! e>ly ,prot]ozoic rocks ( we/]n ,ont>io1 ,canada4 ,a climatic condition favorable = ! developm5t ( glaci]s s e>ly 9 ! hi/ory ( ! e>? is1 to say ! lea/1 directly oppos$ to an idea 7bas$ ^u ! nebul> hypo!sis7 long held t ! climate ( e>ly geologic "t mu/ h be5 mu* w>m] ?an t ( ! pres5t4 ,,*apt] ,,xiv ,,anci5t ,,e>? ,,hi/ory 7,paleozoic ,era7 ,beg9n+ ) ! e>lie/ ,paleozoic1 ! legible records ( ev5ts ( e>? hi/ory are f> m abundant & less defac$ ?an ^? ( e>li] times4 ,/ratifi$ rocks ( ! ord9>y k9ds greatly pr$om9ate ov] ! igne\s & metamorphic rocks1 & ! /rata are 9 g5]al f> less di/urb$ ?an ^? ( ! ,ar*eozoic & ,prot]ozoic gr\ps4 ,f ! e>lie/ ,paleozoic we h also ! fir/ abundant records 7fossils7 ( ! life ( ! e>?1 s t ! ord9>y me?ods ( subdivid+ & det]m9+ ! relative ages ( ! ,paleozoic & lat] /rata1 z well z correlat+ ! subdivisions 7=mations7 9 widely sep>at$ regions1 c be us$4 ,f "h on 9 our discussion ( e>? hi/ory we %all be able to trace ! sali5t features ( ! *ang+ outl9es ( ! face ( ! e>?1 ! com+ & go+ ( ! seas ov] ! l&s1 & ! evolution ( animals & plants ) a consid]able degree ( def9it5ess & satisfaction4 ,fir/1 we %all trace out1 9 ! regul> ord] ( _! occurr5ce1 ! ma9 physical hi/ory ev5ts ( ,paleozoic "t1 leav+ a consid]ation ( ! evolution ( life = o!r *apt]s4 ,because ( limitation ( space1 our att5tion w be almo/ :olly c5t]$ ^u ! cont95t ( ,nor? ,am]ica1 b ! read] %\ld be> 9 m9d t ! g5]al pr9ciples & facts set =? apply ) ab\t equal =ce to mo/ o!r cont95ts4 ,9 ,europe ! wond]ful records ( ,paleozoic hi/ory are f\nd 9 /rata1 ^: e/imat$ maximum ?ickness is ab\t #ajj1jjj feet6 ,x mu/ n be ?\ght1 h[ev]1 t all ^! /rata are pil$ up 9 a s+le locality1 b ! figure does actually repres5t ! sum total ( ! greate/ ?ickness ( ! _m subdivisions 7=mations7 ( ! ,paleozoic rocks 9 diff]5t portions ( ! cont95t4 ,9 ,nor? ,am]ica ! maximum ?ickness ( all ,paleozoic rocks seems to be no less ?an #ej1jjj feet4 ,m ?an #be1jjj feet ( /rata may actually be obs]v$ pil$ lay] ^u lay] 9 ! highly fold$ & deeply erod$ c5tral ,appala*ian ,m\nta9s4 ,! great ?ickness ( ! /rata1 comb9$ ) ! facts t ! fossils %[ t _m m>vel\s1 mo/ly progressive1 *anges took place among liv+ ?+s1 t seas came & w5t repeat$ly ov] _m p>ts ( ! cont95t1 & t great *anges took place 9 ! configuration ( ! l&1 =ce u to conclude t ,paleozoic "t mu/ h la/$ = _m millions ( ye>s4 ,j be=e ! op5+ ( ! ,paleozoic era practically all ( ,nor? ,am]ica appe>s to h be5 dry l&1 :i* _h und]gone s mu* erosion t x 0 l[ & f> less rugg$ 9 relief ?an at pres5t4 ,?is we "k1 because ! r widespread e>ly ,paleozoic 7,cambrian7 /rata almo/ ev]y:]e re/ ^u deeply erod$ rocks ( ei!r ,ar*eozoic or ,prot]ozoic age4 ,consid]+ bo? ! "t involv$ & ! wide area affect$1 we h no record ( any?+ l su* a pr(\nd erosion int]val s9ce ! beg9n+ ( ! ,paleozoic era4 ,x seems t ! con/ructive or upbuild+ =ces )9 ! e>? 7 !n rem>kably quiesc5t1 :ile ! de/ructive =ces 7erosion7 7 almo/ unhamp]$ 9 _! "w ( cutt+ d[n ! l&4 ,h we any def9ite idea ( ! relations ( l& & wat] 9 ,nor? ,am]ica dur+ ! fir/ or ,cambrian p]iod ( ! ,paleozoic era8 ,9 ! affirmative answ] to ?is "q1 c]ta9 pr9ciples w be br\ght out :i* ! read] %\ld keep 9 m9d z we trace out ! succe$+ great physical *anges 9 ! hi/ory ( ,nor? ,am]ica4 ,x %\ld1 h[ev]1 be rememb]$ t1 9 ! brief space at our disposal1 only ! mo/ g5]al1 or ! mo/ significant localiz$1 physical *anges 9 ! long & intricate kn[n hi/ory ( ! cont95t s9ce ! op5+ ( ! ,paleozoic era c be br\ght out4 ,9 e>ly ,cambrian "t a n>r[ arm ( ! sea 7l a /rait7 ext5d$ f ! ,gulf ( ,/4 ,lawr5ce s\?w>d across ea/]n ,new ,york & ov] ! site ( ! pres5t ,appala*ian ,m\nta9s connect+ ) ! ,gulf ( ,mexico on ! s\?4 ,on ! we/1 a mu* l>g] & broad] arm ( ! sea 7l a m$it]ranean7 ext5d$ f ,alaska s\?w>d ov] ! site ( ! ,rocky ,m\nta9s ( ,canada & across ! sites ( ! ,columbia ,plateau to ,great ,bas9 ( ! we/]n ,unit$ ,/ates4 ,all ! re/ ( ! cont95t 0 l&1 app>5tly almo/ or :olly devoid ( high m\nta9s4 ,by :at process ( reason+ d we conclude t arms ( ! e>ly ,cambrian sea rea*$ across ea/]n & we/]n ,nor? ,am]ica8 ,fir/1 :]ev] m>9e /rata ( def9itely det]m9$ e>ly ,cambrian age n[ occur1 ! e>ly ,cambrian sea mu/ h exi/$ because ^? /rata 7 obvi\sly deposit$ 9 t sea4 ,second1 to ^? areas we mu/ add o!rs f :i* x c be demon/rat$ t e>ly ,cambrian m>9e /rata h be5 remov$ by erosion4 ,en\gh field "w along ^! l9es has be5 done 9 ,nor? ,am]ica to r5d] x practically c]ta9 t ! relations ( l& & wat] dur+ e>ly ,cambrian "t 7 ess5tially z above outl9$4 ,illu/ration3 ,fig4 #cc4--,map %[+ ! relations ( l& & wat] 9 ,nor? ,am]ica dur+ e>ly ,cambrian "t1 at lea/ #be1jjj1jjj ye>s ago4 ,l9$ areas repres5t l&4 7,pr9cipal data f a map by ,willis publi%$ 9 ! ,j\rnal ( ,geology47 ,illu/ration3 ,fig4 #cd4--,map %[+ ! relations ( l& & wat] 9 ,nor? ,am]ica dur+ ,middle ,ordovician "t4 ,l9$ areas repres5t l&4 7,pr9cipal data f a map publi%$ by ,willis 9 ! ,j\rnal ( ,geology47 ,z ,cambrian "t w5t on1 ! m>9e wat]s gradually spread f s\? to nor? across mo/ ( ! ,mississippi ,valley area1 caus+ ! ea/]n & we/]n arms ( ! sea to be connect$1 ?us =m+ an int]ior cont95tal sea4 ,o!rwise ! relations ( l& & wat] 7 mu* z 9 e>ly ,cambrian "t4 ,we "k t ! sea transgress$ nor?w>d across ! ,mississippi ,valley di/rict because1 on ! s\?1 ! :ole ,cambrian sy/em ( /rata 7l[]1 middle1 & upp]7 is pres5t1 :ile1 f>!r nor?1 only middle & upp] ,cambrian are pres5t1 &1 f>!/ nor?1 only upp] ,cambrian /rata occur4 ,?is progressive nor?w>d ov]lap ( y\ng] & y\ng] 7lat]7 ,cambrian /rata ^u ! old rock floor proves1 t ! ,cambrian sea /eadily spread f>!r & f>!r nor?w>d ov] ! ,mississippi ,valley area4 ,t ?is spread+ sea 0 %all[ is amply demon/rat$ by ! deposits x left1 su* z %ales1 conglom]ates 7i4e41 consolidat$ gravels7 & s&/ones1 (t5 ripple-m>k$4 ,! ,cambrian /rata ( ,nor? ,am]ica v>y 9 ?ickness f less ?an #a1jjj feet to ab\t #ab1jjj feet4 ,9 ! ,mississippi ,valley ! ,cambrian /rata are unalt]$ & almo/ undi/urb$ f _! orig9al horizontal position4 ,9 ! ,appala*ian ,m\nta9s ( ! ea/1 & ! ,rocky ,m\nta9s ( ! we/1 ! /rata are commonly notably fold$ & fault$4 ,9 "s places1 z 9 we/]n ,new ,engl&1 ! /rata h be5 notably alt]$ 7metamorphos$74 ,! be/ e/imates = ! duration ( ! ,cambrian p]iod range f #b1jjj1jjj to #c1jjj1jjj ye>s4 ,x is a rem>kable fact t1 dur+ ?is great lapse ( "t1 ,nor? ,am]ica 0 unaffect$ by any great physical di/urbances su* z m\nta9 mak+1 em]g5ce ( l>ge tracts ( l&1 or igne\s activity4 ,! "o great physical ev5t ( ! ,cambrian 0 ! gradual subm]g5ce ( a consid]able portion ( ! cont95t4 ,t ! climate ( ! e>lie/ ,cambrian 0 at lea/ locally favorable = ! exi/5ce ( glaci]s1 is prov$ by ! occurr5ces ( true glacial deposits 9 rocks ( t age 9 ,*9a1 ,norway1 & ,au/ralia4 ,x is a rem>kable fact t ! glacial mat]ials ( ,*9a occur along ! ,yangtse ,riv]1 ?us demon/rat+ t conditions = glaci]s !n exi/$ at a latitude z f> s\? z ,new ,orleans4 ,^! evid5ces ( glaciation directly refute ! old idea1 bas$ ^u ! nebul> hypo!sis1 t ! climate ( ! ,paleozoic 0 di/9ctly w>m] ?an n[4 ,! glacial evid5ce1 add$ to our k ( ! "* & _w-wide di/ribution ( _m id5tical species ( animals1 leads u to conclude t e>ly ,paleozoic climate 0 n ess5tially diff]5t f t ( v rec5t geologic "t1 b t ! climate 0 !n mu* m uni=m ?an at pres5t4 ,dur+ ! second or ,ordovician p]iod ( ! ,paleozoic era1 ! progressive subm]g5ce ( ,cambrian "t cont9u$ until a climax 0 rea*$ t[>d ! middle ( ! p]iod :5 fully f\r-fif?s ( ! cont95t 0 subm]g$ "u %all[ sea wat]4 ,s9ce middle ,ordovician m>9e /rata are m widespread ?an ! rocks ( any succe$+ age1 we c be reasonably sure t s mu* ( ! cont95t 0 nev] aga9 cov]$ by ! sea4 ,9 fact1 s f> z ! records h be5 int]pret$1 ?is came ne>e/ to be+ a univ]sal flood 9 ! :ole kn[n hi/ory ( ! cont95t4 ,by ! v "* ( ! rocks deposit$ 7seldom ov] a few ?\s& feet ?ick71 we c be sure t ! middle ,ordovician cont95tal sea 0 ev]y:]e f> %all[] ?an ! great ocean abysses ( to-day4 ,because ! l&s 7 s l[ & re/rict$1 relatively little l&-d]iv$ s$im5t wa%$ into ! sea4 ,b ! %all[ sea wat] 0 inhabit$ by millions ( animals1 ! %ells ( _m ( :i* sl[ly accumulat$ to build up ! ?ick bodies ( lime/one /rata 7,plate #ad7 :i* con/itute ! ma9 bulk ( rock ( e>ly & middle ,ordovician age4 ,! fam\s ,tr5ton lime/one1 nam$ f a locality 9 c5tral ,new ,york1 ) its great abundance ( fossils1 0 =m$ mo/ly by ! accumulation ( %ells ( animals dur+ middle ,ordovician "t4 ,lat] 9 ! ,ordovician !re 0 a consid]able %ift 9 level betwe5 l& & wat] caus+ a )drawal ( mu* ( ! widespread sea4 ,z a result ( ! g5]ally m elevat$ l&s1 erosion proce$$ m vigor\sly1 & s&s & muds 7 m abundantly deposit$ 9 ! re/rict$ sea1 ^! s$im5ts hav+ consolidat$ to =m ! %ales & s&/ones :i* pr$om9ate among ! upp] ,ordovician rocks4 ,a pr9ciple above briefly expla9$ 9 ! discussion ( ! ,cambrian may be reemphasiz$ "h4 ,x is z foll[s3 ,9 mak+ a map to %[ ! relations ( l& & wat]1 say dur+ middle ,ordovician "t1 ! geologi/ is by no means dep5d5t only ^u actual surface exposures ( middle ,ordovician /rata4 ,su* exposures fall f> %ort ( giv+ an adequate conception ( ! =m] or ev5 pres5t real ext5t ( su* /rata4 ,9 _m places orig9ally pres5t ,ordovician /rata h be5 remov$ by erosion4 ,an excell5t case 9 po9t is ! ,adirondack region ( nor!rn ,new ,york4 ,on ! we/ side ( ! ,adirondacks a great pile ( m>9e ,ordovician /rata #a1ejj feet ?ick end abruptly on ! g5tly slop+ flank ( ! m\nta9s1 ?us cle>ly prov+ t ! /rata =m]ly ext5d$ at lea/ tw5ty to ?irty miles ea/w>d4 ,aga91 9 ! s\!rn ,adirondacks a small area ( v typical m>9e middle ,ordovician /rata lies fully fifte5 miles f ! g5]al area ( su* rocks to ! s\?4 ,?is small body ( rock is v cle>ly only an erosion remnant ( a g5]al %eet ( middle ,ordovician rock :i* once cov]$ ! :ole int]v5+ di/rict4 ,9 _m o!r regions ! middle ,ordovician /rata are def9itely kn[n to be conceal$ "u cov] ( lat] rocks1 z 9 ! ,mississippi ,valley1 :]e ! actual surface exposures con/itute only a fraction ( ! middle ,ordovician /rata :i* und]lie ne>ly all ! valley1 z prov$ by deep well drill+s1 /udy ( ! scatt]+ outcrops1 etc4 ,9 /ill o!r places1 middle ,ordovician /rata1 associat$ ) o!r rocks1 are highly fold$1 z 9 ! ,appala*ians1 :]e su* /rata outcrop 9 only n>r[ belts foll[+ ! tr5d ( ! folds4 ,9 %ort1 !n1 :]ev] x c be prov$ t middle ,ordovician m>9e /rata are visible at ! surface1 or are conceal$ "u o!r rocks1 or 7 once pres5t1 we c be sure t ! middle ,ordovician sea exi/$4 ,exactly ?is pr9ciple applies to any subdivision ( geologic "t4 ,illu/ration3 ,fig4 #ce4--,/ructure section %[+ rocks repres5t+ ?ree geologic eras sep>at$ by millions ( ye>s ( "t4 ,l5g? ( section #ab miles1 v]tical scale mu* exagg]at$4 ,at ! bottom are ,ar*eozoic 7,precambric7 rocks & re/+ ^u !m on ! left are e>ly ,paleozoic /rata #a1ejj feet ?ick4 ,a glacial lake deposit ( late ,c5ozoic age lies on ! ,ar*eozoic rock t[>d ! "r4 ,x is evid5t t ! ,paleozoic /rata =m]ly ext5d$ mu* f>!r ea/w>d4 7,by ! au?or z publi%$ 9 a ,new ,york ,/ate ,museum ,bullet947 ,! ,ordovician p]iod clos$ ) a great m\nta9-mak+ di/urbance 9 ea/]n ,nor? ,am]ica1 & at ! same "t all1 or ne>ly all1 ( ! cont95t 0 l&4 ,?r\gh\t mo/ ( ! ,cambrian & ,ordovician p]iods1 ! /rata accumulat$ to a ?ickness ( ?\s&s ( feet 9 ! m>9e wat]s :i* spread ov] ! ea/]n bord] ( ,new ,york1 ! sites ( ! ,gre5 ,m\nta9s ( ,v]mont1 ! ,b]k%ire ,hills ( ,massa*usetts1 & s\?w>d at lea/ z f> z ,virg9ia1 ov] ! area ( ! ,pi$mont ,plateau4 ,at1 or t[>d ! close ( ! ,ordovician p]iod1 a great compressive =ce 9 ! e>?'s cru/ 0 br\ght to be> ^u ! mass ( /rata & !y 7 tilt$1 highly fold$1 & rais$ above sea level into a great m\nta9 range kn[n to geologi/s z ! ,taconic ,range4 ,x is q ! rule ?r\gh\t ?is region ( ,taconic di/urbance to f9d ! /rata ei!r on edge or mak+ high angles ) ! plane ( ! horizon4 ,_m ( ! folds 7 actually ov]turn$1 & 9 "s cases notable ?ru/ faults develop$1 t is1 ! upp] /rata broke across & great masses 7 %ov$ ov] ea* o!r4 ,^! facts all g to %[ t ! m\nta9-mak+ compressive =ce appli$ to ! region 0 ( r an extreme type4 ,s9ce ! orig9 ( ! ,taconic ,range a trem5d\s am\nt ( erosion has tak5 place1 s t lit]ally only ! roots ( ! range are n[ expos$ 9 ! ,gre5 ,m\nta9s1 ,b]k%ire ,hills1 ,highl&s-(-!-,hudson1 & ! nor!rn ,pi$mont ,plateau4 ,h[ d we "k t ! ,taconic di/urbance took place t[>d ! close ( ! ,ordovician p]iod8 ,by way ( answ] to ?is "q two facts ne$ to be consid]$4 ,fir/1 relatively late 7or "y7 ,ordovician /rata are involv$ ) ! folds1 ?us prov+ t ! folds =m$ aft] ^? late ,ordovician s$im5ts 7 deposit$4 ,second1 undi/urb$ /rata =m$ dur+ ! middle ( ! next 7,silurian7 p]iod1 re/ ^u ! erod$ edges ( ! folds1 :i* proves t ! folds mu/ h develop$ well be=e middle ,silurian "t because ! only "t !y 7 subject$ to erosion mu/ h be5 dur+ e>ly ,silurian "t4 ,illu/ration3 ,fig4 #cf4--,/ructure section %[+ pr(ile & und]gr\nd relations ( ! rocks across "p ( ! ,highl&s-(-!-,hudson region 9 s\!a/]n ,new ,york4 ,l5g? ( section1 sixte5 miles4 ,! rocks are mo/ly ( ,prepaleozoic ,age1 b ) belts ( highly infold$ e>ly ,paleozoic /rata t[>d ! middle "r4 7,aft] ,b]key1 ,new ,york ,museum ,report47 ,m5tion %\ld also be made ( ! pr(\nd metamorphism 7alt]ation7 ( ! ,cambrian & ,ordovician /rata along ! ma9 axis ( ! range1 :]e ! int5se compression1 aid$ by heat & moi/ure1 caus$ ! deeply buri$ portions ( ! /rata to become pla/ic1 & h5ce !y became m or less foliat$ 7cleavable7 & cry/alliz$ into v>i\s metamorphic rock types1 ! lime/one hav+ *ang$ to m>ble1 ! %ale to slate or s*i/1 & ! s&/one to qu>tzite4 ,?us we expla9 ! rocks ( ! ext5sive m>ble qu>ries ( ,v]mont & we/]n ,massa*usetts1 ! slate qu>ries ( c5tral ea/]n ,new ,york1 & ! ,b]k%ire s*i/ ( ! ,b]k%ire ,hills ( ,massa*usetts4 ,"o ( ! gr&e/ & mo/ significant ( all ! pr(\nd geological processes is ! bir? & hi/ory ( a great fold$ m\nta9 range4 ,s9ce ! ,taconic ,range af=ds u su* an excell5t example ( a l>ge-scale1 well-und]/ood fold$ range ( great antiquity we may d well to consid] x 9 ! light ( c]ta9 o!r broad relation%ips4 ,! great compressive =ce :i* fold$ & uprais$ ! ,taconic ,m\nta9s did n accompli% its "w rapidly 9 ! ord9>y human hi/ory s5se ( ! ^w4 ,! =ce 0 sl[ly & irresi/ibly appli$1 & ! /rata well bel[ ! surface 7 gradually bulg$ or fold$1 or fractur$ :]e ne> ! surface1 ! l5g? ( "t requir$ = ! op]ation hav+ be51 at ! v lea/ calculation1 "s hundr$s ( ?\s&s ( ye>s1 & m ?an likely a million ye>s or m4 ,su* a l5g? ( "t is1 h[ev]1 s %ort comp>$ ) all kn[n e>? hi/ory1 t we are accu/om$ to ref] to ! =mation ( su* a m\nta9 range z simply an ev5t ( geological hi/ory4 ,ev5 be=e su* a range atta9s its maximum height a v consid]able am\nt ( erosion has already tak5 place4 ,:5 ! fir/ fold appe>s above sea level1 erosion beg9s its "w & cont9ues ) increas+ vigor z ! m\nta9 masses get high] & high]4 ,?us we h w>f>e betwe5 two great natural processes--! build+ up & ! te>+ d[n4 ,aft] a "t ! build+-up process wanes & !n ceases1 :ile ! te>+-d[n process 7erosion7 cont9ues ei!r until ! :ole range has be5 completely worn d[n or until "s rejuv5at+ =ce causes a r5ew$ uplift4 ,"h is an example ( "o ( ! rem>kable proc$ures ( nature4 ,aft] millions ( ye>s ( "w caus+ ! deposition ( ?\s&s ( feet ( /rata1 pil$ lay] ^u lay] on ! sea floor1 a =ce ( lat]al pressure is br\ght to be> & a m\nta9 range is lit]ally born out ( ! sea4 ,no soon] is ! range well =m$ ?an ! de/ructive processes 7erosion7 unceas+ly set to "w to de/roy ?is m>vel\s "w4 ,b ! s$im5ts d]iv$ f ! we> ( ! range are c>ri$ into ! ne>e/ ocean aga9 to accumulate &1 p]*ance1 aft] long ages1 to be rais$ into ano!r range2 & s ! process may be (t5 repeat$4 ,f ?is we le>n t ! m\nta9 ranges ( ! e>? are by no means all ( ! same age4 ,! orig9al ,adirondacks 7 =m$ long be=e ! ,taconics1 :i* orig9at$ millions ( ye>s be=e ! ,appala*ians1 ^! latt] hav+ be5 fold$ up long be=e ! ,si]ras4 ,! ,rockies1 foll[$ by ! ,coa/ ,ranges1 are ea* y\ng] ?an ! ,si]ras z reg>ds _! orig9al fold+ & uplift4 ,among =eign c\ntries special m5tion %\ld be made ( ! ,briti% ,isles1 :]e ,ordovician /rata ?\s&s ( feet ?ick 71 late 9 ! p]iod1 notably fold$ & uprais$1 ! cru/al di/urbance hav+ be5 accompani$ by great intrusions ( molt5 rocks & va/ outp\r+s ( lavas1 s t ?is region ranks among ! greate/ ( ! anci5t volcanic areas ( ,europe4 ,illu/ration3 ,fig4 #cg4--,map %[+ ! g5]al relations ( l& & wat] 9 ,nor? ,am]ica dur+ middle & late middle ,devonian "t fully #ae1jjj1jjj ye>s ago4 7,aft] ,willis1 c\rtesy ( ! ,j\rnal ( ,geology47 ,we %all n[ turn our att5tion to a v brief consid]ation ( ! sali5t po9ts 9 ! physical hi/ory ( ,nor? ,am]ica dur+ ! next great p]iod 7,silurian7 ( ! ,paleozoic era4 ,z a result ( ! physical di/urbance late 9 ! ,ordovician ! great int]ior sea 0 l>gely or :olly expell$ f ! cont95t1 & ?is 0 ess5tially ! condition ( ! cont95t at ! beg9n+ ( ! ,silurian4 ,b ?is condition 0 ( %ort duration1 = e>ly 9 ! ,silurian ! sea aga9 began to spread1 gradually increas+ 9 ext5t to a climax 9 ab\t ! middle ( ! p]iod4 ,at ?is "t ! fam\s & ext5sive ,niag>a lime/one1 s nam$ f ! rock at ! cre/ ( ,niag>a ,falls1 0 deposit$4 ,except = ! newly =m$ ,taconic ,range1 /&+ out z a bold topographic feature along ! middle ,atlantic ,coa/1 & a some:at wid] ext5t ( l&1 ! condition ( ! cont95t dur+ middle ,silurian "t 0 v simil> to t ( middle ,ordovician "t4 ,illu/ration3 ,fig4 #ch4--,map %[+ ! g5]al relations ( l& & wat] 9 ,nor? ,am]ica dur+ middle ,mississippian "t4 7,aft] ,willis1 c\rtesy ( ! ,j\rnal ( ,geology47 ,soon aft] mid-,silurian "t ! seas became greatly re/rict$ almo/ to disappe>ance z su*4 ,9 ! ea/]n ,unit$ ,/ates & s\!a/]n ,canada /rata ( t p>ticul> age are f\nd only 9 p>ts ( ,ont>io1 ,new ,york1 ,ohio1 ,mi*igan1 & f ,p5nsylvania s\?w>d to ,we/ ,virg9ia1 :]e !y are *>act]iz$ by r$ %ales & s&/ones1 & salt & gypsum deposits4 ,su* mat]ials conta9+ few fossils v cle>ly indicate deposition 9 ei!r ext5sive lagoons or m or less cut-(f arms ( ! sea "u arid climate conditions r ?an 9 ord9>y m>9e wat]4 ,/ill lat] 9 ! ,silurian ! int]ior seas 7 p>tially re/or$1 z %[n by ! fact t true m>9e /rata correspond+ to t age n only cov] ! salt & gypsum deposits1 b are notably m ext5sive ?an !y4 ,ab\t ! close ( ! ,silurian p]iod almo/ all ( ! cont95t 0 dry l&4 ,unlike ! ,ordovician p]iod1 ! ,silurian clos$ )\t any m\nta9-mak+ di/urbance or great uplift ( l&4 ,! ,silurian p]iod1 l ! prec$+ ,ordovician & ,cambrian1 seems to h be5 free f any m ?an slight igne\s activity z1 = example1 9 ,ma9e & ,new ,brunswick4 ,! total ?ickness ( ,silurian /rata 9 ,nor? ,am]ica is seldom m ?an a few ?\s& feet4 ,! sali5t features ( ! physical hi/ory ( ! next1 or ,devonian p]iod1 are mu* l ^? ( ! prec$+ ,silurian4 ,at ! beg9n+ ( ! ,devonian almo/ all ( ! cont95t 0 dry l&1 b soon a long1 n>r[ arm ( ! sea ext5d$ across ! ea/]n side ( ! cont95t f ! ,gulf ( ,/4 ,lawr5ce s\?w>d ?r\gh we/]n ,new ,engl&1 s\!a/]n ,new ,york & ?r\gh\t ! ,appala*ian di/rict1 ?us rem9d+ u ( ! long1 n>r[ s\nd :i* occupi$ almo/ exactly ! same t]ritory dur+ ! e>ly "p ( ! ,cambrian p]iod4 ,9 ! we/ ! only wat] 0 a small embaym5t rea*+ across s\!rn ,cali=nia into ,nevada4 ,by middle ,devonian "t ^! wat] areas _h consid]ably exp&$4 ,dur+ relatively late ,devonian "t ! sea 0 s exp&$ z to cov] mu* ( ! ,mississippi ,valley area1 ! ,appala*ian ,m\nta9s & ,/4 ,lawr5ce ,valley areas1 & mo/ ( ! site ( ! ,rocky ,m\nta9s1 except = an isl& ( consid]able size rea*+ f ,new ,mexico ?r\gh ,wyom+4 ,! ma9 l&s 7 mo/ ( nor!a/]n ,nor? ,am]ica1 a l>ge l& area ext5d+ f ,florida to ,nova ,scotia1 & a l>ge area on ! we/]n side ( ! cont95t f ,cali=nia to ,alaska4 ,a rem>kable =mation ( late ,devonian ,age %\ld be briefly describ$4 ,9 s\!a/]n ,new ,york & ! nor!rn ,appala*ian region !re 0 a trem5d\s accumulation ( s$im5ts :i* h consolidat$ into s&/one1 toge!r ) "s %ale & conglom]ate4 ,?is s-call$ ,catskill =mation is f #a1ejj to #h1jjj feet ?ick & is well %[n z ! ma9 body ( rock 9 ! ,catskill ,m\nta9s4 ,x is l>gely a %all[-wat] deposit ( ess5tially nonm>9e orig91 z prov$ by co>s5ess ( mat]ial1 ripple m>ks1 & nonm>9e fossils4 ,all evid5ce po9ts to ! orig9 ( ?is rem>kable =mation z a great delta deposit built out into ! %all[ int]ior sea4 ,notable ?9n+ t[>d ! we/1 ) increas+ f95ess ( gra9 ( mat]ial1 %[s t ! s$im5t came f ! ea/1 no d\bt c>ri$ by a l>ge riv] f ! small cont95tal l& mass 7call$ ,appala*ia7 on ! ea/]n side ( ,nor? ,am]ica4 ,! maximum ?ickness ( ! ,nor? ,am]ican ,devonian seems to be ab\t #ae1jjj feet 9 ! nor!rn ,appala*ian region1 b else:]e x g5]ally ranges f #a1jjj to #d1jjj feet ?ick4 ,9 ,nor? ,am]ica ! subdivisions ( ! ,devonian /rata ( ,new ,york are tak5 z a /&>d = comp>ison1 bo? because ( ! wond]ful complet5ess & almo/ undi/urb$ "* ( ! rocks !re1 & because !y h be5 s c>efully /udi$4 ,! ,devonian sy/em is !re fully #d1jjj feet ?ick1 ) sc>cely a m9or subdivision miss+1 & x cov]s a wide area 7"o-?ird ( ! ,/ate7 ) _m excell5t outcrops4 ,!re 0 practically un9t]rupt$ deposition ( ,devonian /rata 9 s\!rn ,new ,york4 ,x is d\btful if !re is great] ref9em5t ( k reg>d+ ! ,devonian or any o!r ,paleozoic sy/em ( /rata any:]e else 9 ,nor? ,am]ica4 ,dur+ middle to late ,devonian "t ! region f s\!rn ,new ,engl& to ,nova ,scotia & ! ,/4 ,lawr5ce ,valley 0 notably di/urb$ by e>? movem5ts1 ! l&s hav+ be5 consid]ably elevat$ & ! rocks m or less fold$4 ,! great delta deposit ( late ,devonian "t1 already describ$ z be+ ?\s&s ( feet ?ick 9 ,new ,york & ,p5nsylvania1 0 =m$ by "o or m /reams :i* c>v$ mu* s$im5t f ! newly uprais$ l&s4 ,accompany+ ! uplift & fold+ ( ! rocks consid]able masses ( molt5 granite 7 =c$ into ! e>?'s cru/ & "s molt5 rock 0 =c$ to ! surface1 produc+ volcanoes4 ,mu* ( ! granite may n[ be se5 at ! surface 9 v>i\s portions ( ! region1 :ile deeply erod$ volcanoes occur ne> ! city ( ,montreal4 ,except = ! di/urbance ( ! region f ,new ,engl& to ! ,/4 ,lawr5ce1 ! ,devonian p]iod seems to h clos$ r quietly1 ) fairly widespread sea wat] ov] ! l& z already outl9$4 ,?is is prov$ by ! fact t ! e>ly /rata ( ! next p]iod mo/ly re/ 9 regul> ord] ^u ! undi/urb$ late ,devonian /rata4 ,= _m ye>s ! t]m ,c>bonif]\s p]iod 0 us$ to designate a s+le p]iod ( geologic "t :i*1 9 ,am]ica at lea/1 is n[ divid$ into two p]iods--! ,mississippian & ,p5nsylvanian--correspond+1 respectively1 to ! e>lie/ & late/ ,c>bonif]\s4 ,9 reg>d to ! relations ( l& & wat] dur+ ! ,mississippian p]iod1 ! g5]al /atem5t may be made t ! sea1 already fairly ext5sive 9 ! late ,devonian1 cont9u$ to spread until dur+ ! second half ( ! ,mississippian1 :5 mo/ ( ! ,unit$ ,/ates we/ ( ! ea/]n bord] ( ! ,appala*ians 7except ! ,pacific ,nor?we/71 & also ! ,rocky ,m\nta9 region ?r\gh ,canada1 7 subm]g$4 ,a significant physical *ange m>k$ ! close ( ! ,mississippian4 ,?is 0 ! )drawal ( sea wat] f ne>ly all ( ! cont95t1 ! em]g5ce ( ! l& hav+ be5 g5]ally suffici5t to all[ consid]able erosion4 ,! fact t ! ,mississippian & ! next1 or ,p5nsylvanian1 /rata are sep>at$ by ! mo/ ext5sive di/9ct erosion surface 9 ! :ole ,paleozoic gr\p ( rocks is ! *ief reason = consid]+ ^? two sets ( /rata to h =m$ dur+ sep>ate p]iods ( geologic "t4 ,9 ea/]n ,nor? ,am]ica ! ,mississippian /rata v>y 9 ?ickness f a few hundr$ feet to a maximum ( ab\t #e1jjj feet 9 ea/]n ,p5nsylvania4 ,9 ! ,we/1 :]e ! ?ickness is commonly sev]al ?\s& feet1 lime/one greatly pr$om9ates4 ,!re appe>s to h be5 vigor\s volcanic activity dur+ ! p]iod f nor!rn ,cali=nia to ,alaska4 ,c]ta9 pr(\nd cru/al di/urbances m>k$ ! close ( ! p]iod 9 we/]n ,europe1 result+ 9 upturn+ & fold+ ( rocks dur+ ! process ( m\nta9 =m+ f ,irel& to ,g]many1 & f ,bohemia to s\!rn ,france4 ,abundant intrusions & extrusions ( molt5 rocks accompani$ ! di/urbances4 ,we turn next to a consid]ation ( ! ,p5nsylvanian p]iod1 :i* is ( v special int]e/1 because )9 ! rocks ( t age 9 ,nor? ,am]ica1 ,europe1 & ,*9a occur ! greate/ kn[n coal deposits4 ,! p]iod op5$ ) almo/ all ( ,nor? ,am]ica dry l& und]go+ m or less erosion4 ,e>ly 9 ,p5nsylvanian "t m>9e wat] began to ov]spread ! we/]n side ( ! cont95t1 especially mo/ ( ! we/]n two-?irds ( ! area ( ! ,unit$ ,/ates1 :]e /rata ?\s&s ( feet ?ick pil$ up4 ,! sea 0 mo/ widespread be=e ! middle ( ! p]iod1 :5 ! relations ( l& & wat] 7 ab\t z %[n by ,figure #ci4 ,ov] ! site ( ! ,appala*ians & mo/ ( ! ea/]n half ( ! ,mississippi ,valley area ! l& ei!r /ood ne> sea level & 0 (t5 swampy or m>%y1 or at o!r times x 0 a little bel[ sea level1 all[+ tidewat] to ov]spread ! area4 ,su* conditions alt]nat$ repeat$ly1 usually m or less locally1 ov] diff]5t p>ts ( ! di/ricts 9 :i* ! great coal m9es ( ! ea/ are locat$4 ,"u su* conditions /rata f #a1jjj to #h1jjj feet ?ick accumulat$4 ,rem>kable physical geography ( ?is k9d result$ 9 ! gr[? & accumulation ( va/ quantities ( vegetable matt] :i* has *ang$ into ! _w's greate/ coal b$s4 ,simil> conditions prevail$ ov] p>ts ( ,nova ,scotia1 ,new ,brunswick1 & ,rhode ,isl&1 :]e /rata fully #ac1jjj feet ?ick accumulat$4 ,p]haps ! mo/ p]fect resemblance to coal-=m+ condition is t n[ f\nd on su* coa/al pla9s z t ( s\!rn ,florida & ! ,dismal ,swamps ( ,virg9ia & ,nor? ,c>ol9a4 ,bo? ( ^! areas are v level1 ?\gh ) slight depressions 9 :i* !re is ei!r /&+ wat] or swamp condition4 ,9 bo? regions !re is su* g5]al int]f]5ce ) free dra9age t !re are ext5sive areas ( swamp1 & 9 bo? !re are b$s ( vegetable accumulations4 ,9 ea* ( ^! areas !re is a g5]al abs5ce ( s$im5t & !re=e a m>k$ v>iety ( vegetable deposit4 ,if ei!r ( ^! areas 7 subm]g$ b5ea? ! sea1 ! vegetable rema9s w\ld be buri$ & a fur!r /ep made t[>d ! =mation ( a coal b$4 ,reelevation1 mak+ a coa/al pla91 w\ld p]mit ! accumulation ( ano!r coal b$ above ! fir/1 & ?is process might be cont9u$ aga9 & aga94 7,h4 ,ries47 ,b x is n necess>y to assume repeat$ oscillations ( a swamp area up & d[n z ! only way ( acc\nt+ = a succession ( coal b$s "o above ano!r 9 a giv5 region1 because a g5]al1 b int]mitt5t1 subsid5ce1 ) possibly "s upw>d movem5ts1 w\ld occasionally cause ! prolific plant life ( a swamp to be kill$1 aft] :i* s$im5t w\ld deposit ov] ! site4 ,%oal+ ( wat] by accumulation ( s$im5t w\ld p]mit ! developm5t ( m swamp plant life4 ,illu/ration3 ,fig4 #ci4--,map %[+ ! g5]al relations ( l& & wat]1 includ+ ! great coal-plant swamp areas 7v]tical l9es71 9 ,nor? ,am]ica dur+ ! ,p5nsylvanian p]iod at lea/ #aj1jjj1jjj ye>s ago4 ,l9$ areas repres5t l&4 7,aft] ,willis1 c\rtesy ( ! ,j\rnal ( ,geology47 ,9 mo/ coal-m9+ di/ricts !re are at lea/ sev]al coal b$s1 "o above ano!r4 ,9 ,ill9ois !re are n9e2 9 ,p5nsylvania at lea/ tw5ty2 9 ,alabama1 ?irty-five2 & 9 ,nova ,scotia sev5ty-six1 b n all are important comm]cially4 ,ea* coal b$ 9 su* a region repres5ts a swamp :i* exi/$ 9 ,p5nsylvanian "t at lea/ t5 or twelve million ye>s ago1 & 9 :i* !re grew a luxuriant vegetation4 ,_m individual swamps ( t "t 7 ( wide ext5t4 ,! fam\s ,pittsburgh bitum9\s coal b$ repres5ts probably ! l>ge/ "o ( all4 ,x ext5ds f we/]n ,p5nsylvania into p>ts ( ,ohio & ,we/ ,virg9ia ov] an area ( fully #ae1jjj squ>e miles4 ,m ?an #f1jjj squ>e miles ( x are be+ work$ & ! coal b$ av]ages sev5 feet 9 ?ickness ov] an area ( #b1jjj squ>e miles4 ,among ! v>i\s an?racite coal b$s ( ! same age 9 ea/]n ,p5nsylvania ! ,mammo? b$ is exceptionally ?ick1 rea*+ a maximum ( fifty feet or m4 ,9 ord] t ! read] may n ga9 ! impression t coal b$s make up a v consid]able bulk ( ! /rata 9 coal-m9+ regions1 we %\ld /ate t1 on ! av]age1 coal actually con/itutes less ?an #b p] c5t ( ! conta9+ /rata4 ,"s idea ( ! trem5d\s l5g? ( ! geologic ages may be ga9$ by a consid]ation ( ! "t :i* mu/ reasonably be all[$ = ! accumulation ( s _m coal b$s & _! conta9+ /rata4 ,x has be5 e/imat$ t a luxuriant gr[? ( vegetation w\ld produce #ajj tons ( dri$ organic matt] p] hundr$ ye>s4 ,compress$ to ! specific gravity ( coal 7#a4d7 ?is w\ld =m a lay] less ?an two-?irds ( an in* deep on an acre4 ,dur+ ! *emical alt]ation ( vegetable matt] to coal ab\t f\r-fif?s ( ! organic matt] disappe>s 9 ! =m ( gases4 ,on ?is basis1 !n1 x w\ld take ab\t #aj1jjj ye>s to accumulate ! vegetable matt] repres5t$ 9 a coal b$ "o foot ?ick4 ,:5 we realize t ! total ?ickness ( ! coal b$s ( ! ,p5nsylvanian sy/em ( /rata 9 ! great m9+ regions is commonly f #ajj to #bej feet1 we conclude t ! "t !y repres5t is f #a1jjj1jjj to #b1ejj1jjj ye>s4 ,x seems mo/ reasonable t ! "t necess>y = ! deposition ( ! conta9+ /rata mu/ h be5 at lea/ z long4 ,x is1 !re=e1 a fair conclusion t ! ,p5nsylvanian p]iod la/$ f #b1jjj1jjj to #e1jjj1jjj ye>s4 ,t ! climate ( ! great ,coal ,age 0 w>m 7n tropical71 v moi/1 & uni=m1 is borne out by su* facts z ! foll[+1 accord+ to ,d4 ,:ite3 ,! succul5t nature ( ! plants ) _! spongy leaves indicates prolific gr[? 9 moi/1 mild climate2 lack ( ye>ly r+s ( gr[? po9ts to lack ( di/9ct seasons2 z 9 ! case ( _m exi/+ plants ! a]ial roots signify a w>m1 moi/ climate2 plants ( to-day ne>e/ l ! coal plants ?rive be/ 9 w>m1 moi/ regions2 vegetable matt] at pres5t accumulates be/ 9 temp]ate r ?an tropical climates1 because !re decay is n s rapid2 & ! rem>kable uni=mity ( climate ov] ! e>? is cle>ly indicat$ by f9d+ fossil plants ( almo/ or exactly id5tical types 9 rocks ( ,p5nsylvanian ,age f ! ,pol> regions to ! ,tropics4 ,! m rem>kable plants ( ! great ,coal ,age "t are describ$ 9 ! *apt] on ! evolution ( plants 7,plate #ae74 ,dur+ ! la/ 7,p]mian7 p]iod ( ! ,paleozoic era ! m>9e wat]s ( ! we/1 & ! alt]nat+ %all[ tidewat]1 swamps1 & ne> sea level l&s ( ! ea/ gradually gave way to dry l&s1 s t by ! close ( ! p]iod m>9e wat] cov]$ only a small "p ( ! ,s\?we/ f ,oklahoma across c5tral ,texas to s\!rn ,cali=nia & nor?we/]n ,mexico1 :]e /rata z mu* z sev]al ?\s& feet ?ick =m$4 ,9 ! middle we/]n "p ( ! area ( ! ,unit$ ,/ates1 especially f nor!rn ,texas to ,nebraska & ,wyom+1 ! climate 0 arid & r$ /rata 7s-call$ ,r$ ,b$s71 salt1 & gypsum 7 ext5sively deposit$ on l& & 9 great salt lakes or m or less cut-(f arms ( ! sea4 ,/rata commonly f #b1jjj to #g1jjj feet ?ick 7 !re deposit$4 ,simil> conditions prevail$ 9 p>ts ( ,nova ,scotia1 ,new ,brunswick1 & ,newf\ndl&1 :]e /rata #h1jjj feet ?ick accumulat$4 ,ov] ! site ( mo/ ( ! ,appala*ians ! coal swamp conditions1 ) local sea incursions1 cont9u$ f ! prec$+ p]iod1 z %[n by ! "* ( ! /rata 7#a1jjj feet ?ick7 conta9+ "s coal4 ,vigor\s volcanic activity :i*1 z already m5tion$1 began 9 ! ,mississippian p]iod f nor!rn ,cali=nia to ,alaska cont9u$ n only ?r\gh ! ,p5nsylvanian & ,p]mian b also into ! e>ly ,mesozoic era1 z %[n by ! great quantities ( volcanic mat]ials associat$ ) rocks ( ^? ages4 ,! ,p]mian pres5ts a puzzl+ comb9ation ( climatic conditions :i* causes x to /& out 9 m>k$ contra/ aga9/ ! g5]ally mild & uni=m climates ( ne>ly all ( prec$+ ,paleozoic "t4 ,mo/ rem>kable ( all are ! records ( a great ,ice ,age dur+ e>ly ,p]mian "t4 ,"o surpris+ fact is ! widespread di/ribution ( ! glacial deposits 9 bo? ! nor? & s\? temp]ate zones1 & ev5 well )9 ! torrid zone4 ,!y are p]haps mo/ ext5sive & be/ kn[n 9 ,au/ralia1 ,s\? ,africa1 ,india1 & ,brazil4 ,glacial deposits almo/ c]ta9ly ( ! same age on small] scales occur 9 ea/]n ,massa*usetts1 s\!rn ,engl&1 ea/]n ,russia & ! ,caucasus region4 ,al?\gh ! areas occupi$ by ! ,p]mian glaci]s1 :i* 9 _m cases mu/ h be5 ext5sive ice %eets1 _c be accurately delimit$1 x is1 nev]!less1 q c]ta9 t ! ice 0 notably m ext5sively develop$ ?an x 0 dur+ ! great ,ice ,age ( late 7,quat]n>y7 geologic "t4 ,ano!r surpris+ fact is t c]ta9 ( ! glaci]s mu/ h come d[n to1 or ne>ly to1 sea level1 z %[n by ! direct association ( m>9e /rata ) glacial deposits4 ,?us1 9 s\!rn ,au/ralia at lea/ eight b$s ( glacial mat]ials 7"s ( !m #ajj to #bjj feet ?ick7 occur )9 true m>9e /rata #b1jjj feet ?ick4 ,a ?ird rem>kable fact is t ! ,p]mian ,ice ,age1 l ! ,quat]n>y ,ice ,age1 _h int]glacial epo*s ( relatively mild climate1 z prov$ by ! occurr5ces ( b$s ( coal betwe5 c]ta9 ( ! lay]s ( glacial mat]ials 9 ,au/ralia1 ,s\? ,africa1 & ,brazil4 ,dur+ mu* ( ,p]mian "t ! climate 0 arid ov] l>ge areas z1 = example1 mu* ( ! we/]n int]ior ( ! ,unit$ ,/ates1 f ,irel& to c5tral ,g]many1 & 9 ea/]n ,russia1 z prov$ by great deposits ( salt1 gypsum1 & r$ s$im5ts4 ,dur+ late ,p]mian "t ! greate/ salt b$s 9 ! _w 7 deposit$ 9 nor!rn ,g]many1 a well ne> ,b]l9 hav+ p5etrat$ a practically solid body ( salt associat$ ) c]ta9 pota% & magnesia salts to a dep? ( ab\t #d1jjj feet )\t rea*+ ! bottom4 ,! occurr5ce ( "s coal b$s1 especially 9 ! e>li] ,p]mian rocks %[s t1 tempor>ily at lea/1 climatic conditions mu/ h favor$ luxuri\s gr[?s ( coal-=m+ plants 9 ,s\? ,africa1 ,brazil1 ,au/ralia1 & our own ,appala*ian di/rict4 ,f ! above facts we see t ! ,p]mian repres5ts a rem>kable comb9ation ( v ext5sive glaciation1 widespread aridity1 & w>m? & moi/ure favorable to prolific plant gr[? all 9 a s+le p]iod ( geologic "t4 ,! ,p]mian p]iod1 &1 !re=e1 ! great ,paleozoic era1 0 br\ght to a close by "o ( ! mo/ pr(\nd physical di/urbances 9 ! kn[n hi/ory ( ,nor? ,am]ica4 ,?is has be5 call$ ! ,appala*ian ,revolution because at t "t ! ,appala*ian ,m\nta9 range 0 born out ( ! sea by fold+ & upheaval ( ! /rata4 ,9 fact1 ! ,appala*ian ,revolution 0 "o ( ! mo/ critical p]iods 9 ! hi/ory ( ! e>?1 & may h be5 ! greate/ ( !m all 9 its results4 7,c4 ,s*u*]t74 ,m\nta9s 7 br\ght =? 9 all ! cont95ts1 includ+ ,au/ralia4 ,all ( ! m\nta9s :i* 7 =m$ late 9 ! ,paleozoic h s9ce be5 pr(\ndly affect$ by erosion1 & ! only ones 7e4g41 ,appala*ians7 :i* n[ %[ consid]able altitudes are ^? :i* h be5 rejuv5at$ by relatively 7geologically7 rec5t e>? movem5ts4 ,we %all n[ turn our att5tion to ! orig9 ( ! ,appala*ian ,range4 ,all ?r\gh ! va/ "t 7probably fully #bj1jjj1jjj ye>s7 ( ! ,paleozoic era a l>ge l& mass 0 rem>kably p]si/5t along ! ea/]n side ( ,nor? ,am]ica4 ,?is l&1 :i* has be5 call$ ,appala*ia1 _h its we/]n b\nd>y approximately along ! ea/]n bord] ( ! sites ( ! ,appala*ian ,range & ! we/]n "p ( ,new ,engl&4 ,x ext5d$ ea/ ( ! pres5t coa/ l9e at lea/ to ! bord] ( ! cont95tal %elf f #ajj to #bjj miles out4 ,conc]n+ ! actual altitude & topography ( ,appala*ia we "k little or no?+1 b ! trem5d\s quantities ( s$im5t d]iv$ f its erosion %[ t x 0 high en\gh dur+ ne>ly all ( its hi/ory to und]go vigor\s erosion4 ,b>r+ c]ta9 m9or oscillations ( level1 ! region j we/ ( ,appala*ia 0 mo/ly occupi$ by sea wat] ?r\gh\t mu* ( ,paleozoic "t1 & s$im5ts d]iv$ f ! erosion ( ,appala*ia 7 laid d[n lay] ^u lay] z /rata ^u t sea bottom4 ,9 g5]al1 ! co>se/ & greate/ ?ickness ( s$im5ts accumulat$ relatively ne> ! l&1 :ile f9] mat]ials1 9 ?9n] %eets1 deposit$ well out ov] mu* ( ! ea/]n ,mississippi ,valley area 9 ! %all[ seas :i* 7 !re s commonly pres5t4 ,by actual measurem5t we "k t ! ?ickness ( /rata deposit$ ov] ! site ( ! ,appala*ians 0 at lea/ #be1jjj feet4 ,s9ce ^! latt] /rata are mo/ly ( comp>atively %all[ sea-wat] orig91 z prov$ by co>s5ess ( gra9 ( mat]ial1 ripple m>ks1 fossil coral reefs1 etc41 we are =c$ to conclude t ?is m>g9al sea bottom gradually sank :ile ! process ( s$im5tation 0 9 progress4 ,o!rwise we _c possibly expla9 ! great pile ( /rata ( %all[ wat] orig94 ,! v weight ( accumulat+ /rata may ei!r h aid$ or actually caus$ ! s9k+ ( ! long1 relatively n>r[ tr\gh4 ,f9ally1 t[>d ! close ( ! ,paleozoic era1 s9k+ ( ! m>g9al sea floor & deposition ( s$im5ts gave way to a yield+ ( ! e>?'s cru/ by a great =ce ( lat]al compression1 caus+ ! /rata to be ?r[n into folds well bel[ ! surface & m or less fractur$ 9 _! upp] portion4 ,?us1 along ! ea/]n side ( ! site ( ! great int]ior ,paleozoic sea1 ! ,appala*ian ,m\nta9s rose out ( :at = millions ( ye>s _h be5 a long1 n>r[1 s9k+ sea floor4 ,!re 0 m or less fold+ f ! ,gulf ( ,/4 ,lawr5ce to c5tral ,alabama4 ,figure #bd diagrammatically repres5ts ! pr9cipal /ages 9 ! hi/ory ( ! ,appala*ian ,range4 ,:ile ! mo/ pron\nc$ e>? di/urbance occurr$ ?r\gh ! long ,appala*ian belt1 ! :ole ea/]n side ( ! cont95t 0 pr(\ndly affect$4 ,?us ! ,mississippi ,valley area ea/ ( ! ,great ,pla9s 0 consid]ably uprais$ nev] aga9 to be subm]g$ except along ! ,gulf ,coa/1 & an ea/]n int]ior sea has nev] s9ce ov]spread ! region :i* 0 repeat$ly sea-cov]$ dur+ ,paleozoic "t4 ,,*apt] ,,xv ,,m$ieval ,,e>? ,,hi/ory 7,mesozoic ,era7 ,:at 0 ! condition ( ,nor? ,am]ica dur+ ! fir/ or ,triassic p]iod ( ! ,mesozoic era1 approximately #h or #aj million ye>s ago8 ,z a result ( ! ,appala*ian ,revolution ! sea 0 exclud$ f all ! l& except along mu* ( ! we/]n side f s\!rn ,cali=nia to p>ts ( ,alaska4 ,on ?is we/]n side ( ! cont95t ! ,appala*ian ,revolution _h little or no effect & ! ,p]mian conditions cont9u$1 ess5tially )\t *ange ?r\gh ! ,triassic4 ,! ,triassic /rata up to #d1jjj feet ?ick are !re ( typical m>9e orig94 ,9 ,briti% ,columbia & ,alaska !re 0 mu* igne\s activity4 ,?r\gh\t mu* ( ! ,rocky ,m\nta9s & ,great ,pla9s region ( ! we/]n ,unit$ ,/ates !re are ext5sive deposits ( r$ s$im5ts 7s-call$ ,r$ ,b$s71 conta9+ lay]s ( salt & gypsum1 f #bjj to #a1jjj or m feet ?ick4 ,^! /rata commonly re/ 9 regul> ord] on ,p]mian ,r$ ,b$s1 s t conditions ( deposition ( ,p]mian "t cont9u$ ?r\gh ,triassic "t1 t is cont95tal deposits =m$ mo/ly 9 salt lakes1 fre% lakes1 along /ream c\rses1 & on l& 9 "p by ! action ( w9d4 ,illu/ration3 ,fig4 #dj4--,map %[+ ! g5]al relations ( l& & wat] 9 ,nor? ,am]ica dur+ ! ,triassic p]iod4 ,l9$ areas repres5t l&2 v]tical-l9$ areas1 bas9s 9 :i* cont95tal deposits =m$4 7,bas$ ^u map by ,willis2 c\rtesy ( ! ,j\rnal ( ,geology47 ,9 ! ea/]n half ( ,nor? ,am]ica !re is no record ( accumulation ( any m>9e /rata :atev]1 because1 z a result ( ! ,appala*ian ,revolution1 ! l& 0 br\ght well above sea level4 ,!re 01 h[ev]1 deposition ( a rem>kable s]ies ( nonm>9e /rata 9 sev]al long1 n>r[1 tr\ghlike depressions ^: tr5d 0 p>allel to1 & j ea/ (1 ! ma9 axis ( ! newly =m$ ,appala*ian ,range4 ,^! tr\ghs lay betwe5 ! ,appala*ians & ! v p]si/5t old l& mass call$ ,appala*ia :i* we h already describ$4 ,! facts t ^! tr\ghs are truly d[n-w>ps2 t !y s p]fectly foll[ ! tr5d ( ! ,appala*ian ,m\nta9 folds2 & t ! /rata 9 !m are ( late ,triassic ,age1 make x c]ta9 t !y 7 =m$ by a great lat]al pressure :i* mu/ h be5 a cont9uation ( ! ,appala*ian ,revolution4 ,?us ! ,appala*ian ,m\nta9s cont9u$ to gr[ well into ! ,triassic p]iod1 &1 :ile ! ,paleozoic /rata 7 be+ fold$1 ! surface ( old ,appala*ia 7includ+ "p ( ! ,taconic ,m\nta9 region7 0 d[n-w>p$ to =m ! tr\ghs 9 :i* ! late ,triassic /rata accumulat$4 ,"o tr\gh ext5d$ ?r\gh ! ,connecticut ,valley2 ano!r 7! l>ge/7 f s\!a/]n ,new ,york ?r\gh nor!rn ,new ,j]sey1 s\!a/]n ,p5nsylvania1 ,m>yl&1 & into ,virg9ia2 :ile sev]al small] ones occurr$ 9 ,virg9ia & ,nor? ,c>ol9a4 ,! d[n-w>ps or tr\ghlike bas9s 7 v favorably situat$ = rapid accumulation ( ?ick s$im5t>y deposits because ( _! position j betwe5 l>ge1 high l& masses :i* 7 be+ vigor\sly erod$4 ,! s$im5ts d]iv$ f ! erosion ( ! "y ,appala*ians 7 especially abundant because ( ! vigor\s we>+ d[n ( ! newly =m$ high m\nta9s4 ,a ?ickness ( f #e1jjj to fully #ae1jjj feet ( mo/ly r$ s&/ones & %ales accumulat$ 9 ^! d[n-w>ps1 ! "* & great ?ickness ( ! /rata /rongly po9t+ to gradual d[n-w>p+ z ! deposition ( ! s$im5ts w5t on4 ,x is (t5 /at$ t ^! /rata 7 =m$ 9 e/u>ies1 b1 9 ! nor!rn areas1 at lea/ f ,massa*usetts to ,m>yl&1 _m ( ! lay]s %[ ripple m>ks1 sun cracks1 ra9-drop pits1 fossil plants1 & fossil bones & tracks ( l& reptiles4 ,su* /rata may well h =m$ 9 v %all[ wat]1 su* z riv]-flood pla9s or tempor>y lakes1 :]e *ang+ conditions frequ5tly all[$ ! surface lay]s to lie expos$ to ! sun4 ,illu/ration3 ,fig4 #da4--;,block diagram ( ! region we/w>d f ,new ,york ,city & vic9ity1 %[+ ! ma9 relief features1 ! und]gr\nd relations ( rocks ( widely diff]5t ages1 & ! relation ( ! relief to ! rock =mations4 7,"p ( l>g] draw+ by ,a4 ,k4 ,lobeck47 ,dur+ ! "t ( ! accumulation ( ! late ,triassic /rata 9 ! d[n-w>p bas9s !re 0 consid]able igne\s activity1 z prov$ by ! occurr5ce ( %eets ( igne\s rock )9 ! body ( /rata4 ,9 "s cases true lava fl[s ) c9d]y tops 7 =c$ out on ! surface & !n buri$ "u lat] s$im5ts1 :ile 9 o!r cases ! %eets ( molt5 rock 7 =c$ up ei!r betwe5 ! /rata or obliquely ?r\gh !m1 ?us prov+ _! intrusive "*4 ,z a result ( subsequ5t erosion1 ^! v resi/ant lava masses (t5 /& out conspicu\sly z relief features4 ,p]haps ! mo/ notewor?y example is ! great lay] ( su* intrusive igne\s rock1 "p ( :i* outcrops = sev5ty miles mo/ly z a bold cliff =m+ ! fam\s ,palisades ( ! ,hudson1 ne> ,new ,york ,city4 ,dur+ ! process ( cool+ & solidification ( ! molt5 mass !re 0 contraction :i* express$ itself by break+ ! rock mass into great1 crude1 ne>ly v]tical columns1 & h5ce ! orig9 ( ! "n ,palisades4 ,! cliff "* ( ! outcrop is due to ! fact t ! lava is mu* m resi/ant to erosion ?an ! s&/one above & bel[ x4 ,9 ! ,connecticut ,valley ( ,massa*usetts a lay] ( lava sev]al hundr$ feet ?ick boldly outcrops1 =m+ ! cre/ ( ! well-kn[n ,m\nt ,tom-,m\nt ,holyoke ,range4 ,! close ( ! ,triassic p]iod 0 m>k$ by en\gh uplift to leave ! :ole ea/]n two-?irds ( ! cont95t dry l& und]go+ erosion4 ,! ,triassic deposits ( ! ,atlantic ,coa/ are mu* brok5 up into l>ge fault blocks1 & ?is fault+ probably took place z a result ( ! cru/al di/urbances t[>d ! end ( ! p]iod4 ,9 ! we/ ! ,triassic conditions seem to h cont9u$ )\t mu* *ange into ! next 7or ,jurassic7 p]iod4 ,dur+ ! ,jurassic p]iod ! relations ( l& & wat] 9 ,nor? ,am]ica 7 v simple4 ,9 ! e>li] ,jurassic all 0 dry l& except portions ( ! we/]n fr+e ( ! cont95t f s\!rn ,cali=nia to ,alaska1 :]e m>9e /rata #b1jjj to #aj1jjj feet ?ick accumulat$4 ,late 9 ! p]iod ! conditions 7 ! same1 except = a long1 n>r[ arm ( ! sea or m$it]ranean :i* ext5d$ f ! ,arctic ,ocean s\?w>d across ! site ( ! ,rocky ,m\nta9s to ,arizona4 ,!re is no evid5ce = ! exi/5ce ( any?+ l real m\nta9s any:]e on ! cont95t dur+ ! p]iod4 ,illu/ration3 ,fig4 #db4--,/ructure section %[+ pr(ile & und]gr\nd relations ( rocks across ! ,connecticut ,valley 7?r\gh ,m\nt ,tom7 ( ,massa*usetts4 ,js & ,jl are s&/one /rata1 ) includ$ lava %eets 79 black7 re/+ ^u ,paleozoic rocks on ei!r side4 ,! rocks h be5 notably tilt$ & fault$4 7,aft] ,em]son1 ,u4 ,s4 ,geological ,survey47 ,pr(\nd cru/al di/urbances m>k$ ! close ( ! ,jurassic p]iod 9 ! we/]n "p ( ! cont95t4 ,/rata :i* _h accumulat$ to great ?ickness dur+ millions ( ye>s ( "t1 ma9ly ov] ! sites ( ! ,si]ra ,nevada & ,cascade ,m\nta9s1 f9ally yield$ to a trem5d\s =ce ( lat]al compression1 especially 9 ! ,si]ra region1 & 7 fold$1 crumpl$1 & uprais$4 ,?us ! ,si]ra-,cascade di/rict 0 orig9ally built up into a high m\nta9 range4 ,s9ce t "t ! ,si]ras h be5 mu* cut d[n by erosion & !y h be5 rejuv5at$ by fault+ & tilt+ ( ! great e>? block4 ,! ,cascade ,range f nor!rn ,cali=nia into ,briti% ,columbia 0 app>5tly n s pr(\ndly rais$1 & its pres5t height is ma9ly due to subsequ5t volcanic activity4 ,! rocks ( ! ,klama? ,m\nta9s ( nor?we/]n ,cali=nia1 & ( ! ,humboldt ,range ( ,nevada1 7 also fold$ at t "t4 ,dur+ ! m\nta9-mak+ di/urbances on ! we/]n side ( ! cont95t great quantities ( molt5 granite 7 =c$ up into ! l[] portions ( ! fold+ /rata4 ,because ( pr(\nd subsequ5t erosion ?is granite is n[ widely expos$ z1 = example1 9 ! great walls ( ! ,yosemite ,valley4 ,dur+ ! e>li] half ( ! la/ p]iod 7! ,cretace\s7 ( ! ,mesozoic era1 sea wat] spread f ,mississippi nor?we/w>d to ! site ( ,d5v] & s\?w>d ov] ,texas & mu* ( ,mexico4 ,at ! same "t mu* ( ! we/]n m>g9 ( ! cont95t f ,alaska to ,cali=nia 0 subm]g$4 ,all ! re/ ( ! cont95t 0 l&4 ,dur+ ?is "t s$im5ts accumulat$ on l[ l&s j ea/ ( ! site ( ! pres5t ,rocky ,m\nta9s1 & also ea/ ( ! ,appala*ians1 z prov$ by ! num]\s fossils ( l& plants f\nd 9 ^! deposits4 ,illu/ration3 ,fig4 #dc4--,map ,%[+ ! g5]al rotations ( l& & wat] 9 ,nor? ,am]ica dur+ lat] ,cretace\s "t1 sev]al million ye>s ago4 ,l9$ areas repres5t l&2 v]tical l9es1 ma9ly cont95tal deposits4 7,pr9cipal data f a map by ,willis1 publi%$ 9 ! ,j\rnal ( ,geology47 ,z ,cretace\s "t w5t on ! m>9e wat]s gradually spread until ! :ole ,atlantic & ,gulf coa/al pla9 regions f ,long ,isl&1 ,new ,york1 to ,mexico became subm]g$ "u m>9e wat]1 & a wide arm ( ! sea1 or great m$it]ranean1 spread f ,texas nor? to ! m\? ( ! ,mack5zie ,riv]4 ,! ,gulf ( ,mexico 0 ?us directly connect$ ) ! ,arctic ,ocean4 ,?is great int]ior sea 0 n[h]e connect$ ) ! ,pacific ,ocean1 ?\gh portions ( ! ,pacific bord] ( ! cont95t 7 subm]g$4 ,?is va/ int]ior sea 0 n only ! l>ge/ ( any :i* rea*$ well into ! cont95t s9ce ! ,mississippian p]iod ( ! ,paleozoic era1 b x 0 ! la/ body ( m>9e wat] :i* ev] ext5d$ well into ! cont95t4 ,x %\ld be /at$ t ! lat] ,cretace\s 0 also a "t ( unusually widespread subm]g5ce ( ! cont95ts1 :5 mo/ ( s\!rn ,europe & s\!a/]n ,asia1 z well z ab\t "o-half ( bo? ,africa & ,s\? ,am]ica 7 subm]g$4 ,ov] mu* ( ! site ( ! ,rocky ,m\nta9s dur+ ! late ,cretace\s !re 7 l[ l&s receiv+ cont95tal deposits1 & ext5sive m>%es support+ prolific vegetation 7 common4 ,mu* ( ?is vegetable matt] became buri$1 & has s9ce be5 conv]t$ into workable coal4 ,! maximum ?ickness ( /rata accumulat$ dur+ all ( ,cretace\s "t ov] ! ,atlantic coa/al pla9 area 0 ab\t #a1gjj feet2 ov] ! ,gulf coa/al pla9 region fully #g1ejj feet2 ov] ! we/]n int]ior #aj1jjj to #ae1jjj2 & ov] p>ts ( ! ,pacific bord] #be1jjj to #cj1jjj feet1 z 9 ,cali=nia4 ,! la/-nam$ figures are truly ph5om5al1 repres5t+ a ?ickness ab\t equal to ! total ?ickness ( all ! /rata accumulat$ dur+ ! :ole ,paleozoic era 7sev5 p]iods7 & pil$ up 9 ! ,appala*ian ,m\nta9 region4 ,?is great deposit ( /rata ( mo/ly e>ly ,cretace\s ,age is readily acc\nt$ = :5 we realize t ^! s$im5ts1 :i* accumulat$ 9 ! m>g9al sea bottom1 7 d]iv$ f ! v rapidly erod+1 newly =m$ l(ty ,si]ra ,nevada ,range4 ,illu/ration3 ,fig4 #dd4--,sket* ( a m\nta9 range along ,skolat ,creek1 ,alaska1 %[+ ,t]ti>y lava b$s re/+ ^u deeply erod$ tilt$ lime/ones & lavas ( late ,paleozoic 7,c>bonif]\s7 ,age4 ,! pres5t topography has be5 produc$ by erosion s9ce ! ,t]ti>y lavas fl[$ out4 7,aft] ,u4 ,s4 ,geological ,survey47 ,especially 9 ,alabama & ,texas ! ,cretace\s sy/em is rem>kable = its ri*ness 9 *alk deposits4 ,9 ,alabama a widespread =mation ( late ,cretace\s ,age1 ab\t #a1jjj feet ?ick1 conta9s mu* ne>ly pure :ite *alk1 & 9 ,texas a simil>ly con/itut$ =mation ( e>ly middle ,cretace\s ,age is f #a1jjj to #e1jjj feet ?ick4 ,^! *alk deposits consi/ almo/ :olly ( c>bonate ( lime %ells or v t9y s+le-cell$ animals :i* accumulat$ "u exceptionally cle> sea wat] :i* spread ov] ^? p>ts ( ,alabama & ,texas :]e ! *alk n[ occurs4 ,"h aga9 we h a bit ( evid5ce support+ ! fact ( v long geologic "t4 ,?9k ( h[ long x mu/ h tak5 = ! t9y 7ev5 microscopic7 %ells to =m a widespread lay] ( *alk ne>ly a mile ?ick6 ,! close ( ! ,cretace\s p]iod1 or :at is ! same1 ! close ( ! ,mesozoic era1 0 m>k$ by "s ( ! gr&e/ cru/al di/urbances 9 ! kn[n hi/ory ( ! e>?4 ,9 fact1 x is n kn[n t ! we/]n hemisph]e 0 ev] affect$ by m pr(\nd & widespread m\nta9-mak+ di/urbances ?an ^? :i* took place t[>d ! close ( ! ,mesozoic era1 & cont9u$ into ! succe$+ ,t]ti>y p]iod4 ,^! di/urbances 7 ( ?ree k9ds3 fold+ ( /rata1 volcanic activity1 & r5ew$ uplift ( old m\nta9s )\t fold+ ( ! rocks4 ,greate/ ( all 0 ! ,rocky ,m\nta9 ,revolution1 dur+ :i* ! ?ick /rata1 :i* accumulat$ dur+ ! ,paleozoic & ,mesozoic eras ov] ! site ( ! ,rockies1 yield$ to vigor\s de=mation :5 !y 7 m or less fold$ & dislocat$ f ,alaska to ,c5tral ,am]ica4 ,?is 0 9 tru? ! bir? ( ! ,rocky ,m\nta9s1 al?\gh _! exi/+ altitude & configuration h1 to a v consid]able degree1 result$ f lat] uplift & erosion4 ,9 ! nor!rn ,unit$ ,/ates & s\!rn ,canada ! ,rocky ,m\nta9 /rata1 up to ov] #dj1jjj feet ?ick1 7 mo/ sev]ely fold$ & fractur$1 =m+ a range :i* q c]ta9ly 0 fully #bj1jjj feet high4 ,9 ?is di/rict a great ?ru/ fault1 hundr$s ( miles long1 develop$1 & rocks z old z ! ,prot]ozoic 7 %ov$ at lea/ sev5 miles1 & probably z mu* z tw5ty miles1 we/w>d1 ov] ,cretace\s & o!r rocks mu* lat] ?an ! ,prot]ozoic4 ,at ! same "t ! ,&es ,m\nta9s ?r\gh\t ,s\? ,am]ica 7 notably uprais$ & ! rocks fold$4 ,! second type ( physical di/urbance 0 volcanic activity :i* took place on a trem5d\s scale1 & :i* appe>s to h />t$ z a direct accompanim5t ( ! ,rocky ,m\nta9 ,revolution4 ,?is igne\s activity took place n only 9 ! ,rocky ,m\nta9s b also we/w>d to & 9 ! ,si]ra-,cascade ,range1 z well z 9 ! m\nta9s ( we/]n ,briti% ,columbia & ,alaska4 ,?is activity cont9u$ well into ! succe$+ ,c5ozoic era1 & x is m fully consid]$ 9 ! next *apt]4 ,! ?ird type ( cru/al di/urbance took place on a l>ge scale :5 ! ,appala*ian ,m\nta9s1 :i* _h be5 almo/ :olly plan$ away by erosion dur+ ,mesozoic "t1 7 reelevat$ f #a1jjj to #c1jjj feet by an uplift+ =ce n accompani$ by fold+4 ,all or ne>ly all ( ,new ,york & ,new ,engl&1 z well z mu* ( s\!a/]n ,canada1 7 simil>ly uprais$ at ! same "t4 ,?is notable uplift ( s mu* ( ea/]n ,nor? ,am]ica is a matt] ( great importance because ! major relief features ( t area h be5 produc$ by erosion or dissection ( ! uprais$ surface s9ce late ,mesozoic or e>ly ,c5ozoic "t4 ,9 view ( ! fact t ?is "w ( erosion took place almo/ :olly dur+ ! ,c5ozoic era1 x w be discuss$ 9 ! next *apt]4 ,9 conclusion1 brief m5tion may be made ( ! k9d ( climate ( ! ,mesozoic era4 ,z %[n by ! "* & di/ribution ( fossil plants & animals1 ! ,mesozoic climate 0 9 g5]al mild & r uni=m ov] ! e>?1 b ) "s di/9ction ( climatic zones4 ,su* di/9ction ( climatic zones is unkn[n = ! ,paleozoic era1 :ile x 0 notably less ?an at pres5t4 ,,*apt] ,,xvi ,,mod]n ,,e>? ,,hi/ory 7,c5ozoic ,era7 ,s9ce ! ,c5ozoic era is ! la/ "o ( geologic "t1 x w be ( p>ticul> int]e/ to trace out ! ma9 ev5ts :i* h l$ up to ! pres5t day conditions1 especially 9 ,nor? ,am]ica4 ,bo? because ( ! rec5cy ( ! "t & ! unusual accessibility ( ! rocks1 :i* are mo/ly at or ne> ! surface1 our k ( ! ,c5ozoic era is exceptionally detail$ & accurate4 ,x w1 !re=e1 be m necess>y ?an ev] to select only ! v significant features ( ?is hi/ory = our brief discussion4 ,dur+ ! fir/ half ( ! ,t]ti>y p]iod portions only ( ! ,atlantic coa/al pla9 7 subm]g$ "u %all[ wat]1 b soon aft] ! middle ( ! p]iod 7,mioc5e epo*7 ! sea spread ov] practically ! :ole ,atlantic coa/al pla9 area f ,m>?a's ,v9ey>d s\? to & includ+ ,florida4 ,dur+ ! late ,t]ti>y ! m>9e wat]s _h become greatly re/rict$1 & by ! close ( ! p]iod ! sea 0 entirely exclud$ f ! ,atlantic seabo>d4 ,! total ?ickness ( ^! ,t]ti>y /rata is less ?an #a1jjj feet1 & !y all tilt d[nw>d g5tly t[>d ! sea4 ,! /rata consi/ mo/ly ( unconsolidat$ s&s1 gravels1 clays1 m>ls1 etc4 ,! ,gulf coa/al pla9 area f ,florida ?r\gh ,texas & s\? ?r\gh ea/]n ,mexico 0 l>gely ov]spread by ! sea dur+ mo/ ( ,t]ti>y "t1 except ! late/4 ,dur+ e>ly ,t]ti>y "t an arm ( ! ,gulf rea*$ nor? to ! m\? ( ! ,ohio ,riv]4 ,late 9 ! p]iod b little ( ! ,gulf ,pla9 0 subm]g$1 & at its close sea wat] 0 :olly exclud$4 ,on ! ,gulf ,coa/ ! ,t]ti>y /rata f #b1jjj to #d1jjj feet ?ick are also ma9ly s&s1 gravels1 clays1 & m>ls4 ,!y are commonly ri* 9 fossils1 & !y %[ a g5tle tilt d[nw>d t[>d ! ,gulf4 ,?r\gh\t ,t]ti>y "t local portions ( ! ,pacific bord] ( ! cont95t 7 subm]g$1 ?is hav+ be5 especially true ( portions ( ,cali=nia1 ,oregon1 & ,wa%+ton4 ,9 spite ( ! v re/rict$ m>9e wat]s1 ! ,t]ti>y /rata ( ! ,pacific ,coa/1 especially 9 ,cali=nia1 are rem>kably ?ick1 #aj1jjj to #bj1jjj feet be+ common1 :ile ! maximum ?ickness is fully #cj1jjj feet4 ,su* great ?icknesses are readily expla9$ :5 we realize t erosion 0 notably spe$$ up by pron\nc$ uplifts result+ f cru/al di/urbances t[>d ! close ( ! prec$+ p]iod1 & aga9 9 ! mid/ ( ! ,t]ti>y p]iod itself4 ,to summ>ize ! ,t]ti>y relations ( sea & l& = ,nor? ,am]ica we may say t only local portions ( ! cont95tal bord] ev] became subm]g$1 & t1 by late ,t]ti>y "t1 practically ! :ole cont95t 0 a l& area4 ,at ! close ( ! p]iod ! cont95t 01 z we %all see1 ev5 l>g] ?an n[ because ! cont95tal %elves ( ! ocean 7 !n also l>gely above wat]4 ,illu/ration3 ,fig4 #de4--,map %[+ ! g5]al relations ( l& & wat] 9 ,nor? ,am]ica dur+ "p ( ! middle ,t]ti>y p]iod4 7,aft] ,willis1 c\rtesy ( ! ,j\rnal ( ,geology47 ,! :ole ( ! ,c5ozoic era1 includ+ bo? ! ,t]ti>y & ,quat]n>y p]iods1 has be5 a "t ( pr(\nd cru/al di/urbances ?r\gh\t mu* ( ! cont95t1 c]ta9 ( ^! movem5ts hav+ cont9u$ "r up to ! pres5t "t1 ) positive evid5ce t "s ( !m are /ill cont9u+4 ,^! great movem5ts h includ$ notable fold+s ( /rata1 uplifts )\t fold+1 fault+1 & igne\s activity1 ! :ole effect hav+ be5 to greatly increase ! g5]al altitude & rugg$ness ( ! cont95t4 ,9 fact1 ,nor? ,am]ica is n kn[n ev] to h be5 at once high]1 broad]1 & m rugg$ ?an x 0 v late 9 ! ,t]ti>y1 or e>ly 9 ! ,quat]n>y1 p]iod4 ,s9ce t "t ! only notable *ange 7b>r+ ! great ,ice ,age & its effects7 has be5 a re/riction ( ! area ( ! cont95t to its pres5t size by spread+ ( sea wat]s ov] ! bord]s ( ! cont95t1 t is ov] ! cont95tal %elves4 ,we %all n[ r sy/ematically consid] ! m pr(\nd e>? *anges :i* h affect$ ! cont95t1 produc+ ! exi/+ major relief features1 f we/ to ea/4 ,! ,coa/ ,range ,revolution took place 9 ! mid/ ( ! ,t]ti>y p]iod4 ,ov] ! site ( ! ,coa/ ,ranges1 /rata _h accumulat$1 especially dur+ ,cretace\s & e>li] ,t]ti>y times1 to a ?ickness ( ?\s&s ( feet4 ,9 middle ,t]ti>y "t ^! /rata 7 subject$ to a m\nta9-mak+ =ce ( compression & m or less fold$1 fault$ 7fractur$71 & uplift$ into ! ,coa/ ,range ,m\nta9s4 ,"s portions ( ! range 7 int5sely fold$ & fault$ & uprais$ _m ?\s&s ( feet1 :ile o!r portions 7 only mod]ately fold$ & uplift$4 ,x is an int]e/+ fact t ! great ,san ,francisco e>?quake rift or fault orig9at$ at ?is "t4 ,x 0 a r5ew$1 sudd5 movem5t ( a few feet along ?is fault :i* caus$ ! disa/r\s e>?quake ( #aijf4 ,/ill o!r consid]able e>? movem5ts took place 9 ! ,coa/ ,range region dur+ late ,t]ti>y & ,quat]n>y times1 z1 = example1 uplift )\t fold+1 z prov$ by di/9ct sea-cut t]races at altitudes ( m ?an a ?\s& feet1 l ^? nor? ( ,san ,francisco & s\? ( ,los ,angeles4 ,a mod]ate am\nt ( /ill lat] subsid5ce has caus$ ! developm5t ( ,san ,francisco ,bay4 ,! l>ge isl&s (f ! coa/ ( s\!rn ,cali=nia h 9 v rec5t geologic "t 7probably ,quat]n>y7 be5 cut (f f ! ma9l& by s9k+ ( ! l&4 ,illu/ration3 ,plate #aa4--7;a7 ,"p ( ! ,mammo? ,hot ,spr+s ,t]race 9 ! ,yell[/one ,p>k4 ,! view %[s ! deposit ) boil+ wat] fl[+ ov] x4 ,! wat] ent]s ! e>? back on ! m\nta91 travels und]gr\nd 9 contact ) hot lava1 rises ?r\gh lime/one1 f :i* ! boil+ wat] takes into solution mu* c>bonate ( lime :i* is deposit$ :5 ! wat] rea*es ! surface4 7,photo by ,jackson1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #aa4--7;b7 ,view ,across ,"p ( ,crat] ,lake1 ,oregon4 ,?is great hole1 #c1jjj to #d1jjj feet deep & #f miles 9 diamet] & n[ p>tly fill$ ) a lake #b1jjj feet deep1 0 =m$ by a subsid5ce ( ! top ( a once great cone-%ap$ volcano fully #ad1jjj feet high above ! sea4 ,! high rock 9 ! di/ance rises #b1jjj feet above ! lake :i* is ov] #f1jjj feet above sea level4 ,! isl& is a small volcano ( rec5t orig94 7,photo by ,russell1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #ab4--7;a7 ,detail$ ,view ( ,"p ( ! ,v ,olde/ ,kn[n 7,ar*eozoic7 ,rock ,=mation ( ! ,e>?4 ,! rock is di/9ctly /ratifi$ & repres5ts s&s & muds deposit$ lay] ^u lay] ^u a sea floor at lea/ #ej1jjj1jjj ye>s ago4 ,! s&s & muds fir/ consolidat$ into s&/one & %ale bel[ ! e>?'s surface4 ,!n1 "u conditions ( heat1 moi/ure1 & pressure1 !y 7 notably alt]$1 ma9ly by cry/allization ( m9]als1 & rais$ high above sea level4 ,f9ally ! /rata 7 laid b>e by erosion4 7,photo by ! au?or47 ,illu/ration3 ,plate #ab4--7;b7 ,a ,twi/$ ,mass ( ,/ratifi$ ,ar*eozoic ,lime/one ,surr\nd$ by ,granite 9 ,nor!rn ,new ,york4 ,! lime/one 0 envelop$ 9 ! granite :ile x 0 be+ =c$ 9 molt5 condition into ! e>?'s cru/4 7,photo by ! au?or47 ,! ,si]ra ,nevada ,range1 :i* orig9at$ by int5se fold+ ( rocks late 9 ! ,jurassic p]iod1 und]w5t pr(\nd erosion until ab\t ! middle ( ! ,t]ti>y p]iod1 by :i* "t x _h be5 cut d[n to a range ( hills or l[ m\nta9s4 ,!n ! great fault 7fracture7 previ\sly describ$ began to develop along ! ea/]n side4 ,z a result ( _m sudd5 movem5ts along ?is fault1 :i* is hundr$s ( miles long1 ! va/ e>? block has be5 tilt$ we/w>d ) a v /eep ea/]n face & a long1 m gradual we/]n slope1 ! cre/ ( ! fault block =m+ ! summit ( ! range4 ,! am\nt ( ne>ly v]tical displacem5t along ?is fault has be5 commonly f #aj1jjj to #bj1jjj feet1 &1 9 spite ( consid]able erosion ( ! top ( ! fault block & accumulation ( s$im5t at its ea/]n base1 ! modifi$ fault face n[ usually /&s out boldly f #b1jjj to #aj1jjj feet high4 ,z an evid5ce t ?is movem5t ( fault+ has n yet ceas$ we may cite ! ,inyo e>?quake ( #ahgb1 :5 !re 0 a sudd5 r5ewal ( movem5t ( t5 to tw5ty-five feet along ?is fault = _m miles4 ,s9ce ! great ,si]ra block began to tilt1 ! _m mighty canyons1 l ,yosemite1 ,het*-,het*y1 ,k+'s ,riv]1 & ,fea!r ,riv]1 h be5 c>v$ out by ! action ( /reams1 9 "s cases aid$ by =m] glaci]s4 ,k+'s ,riv] canyon has be5 sunk to a maximum dep? ( #f1ijj feet 9 solid granite solely by ! erosive action ( ! riv]6 ,! ,cascade ,m\nta9s1 too1 7 r$uc$ to ne>ly a p5epla9 condition by late ,t]ti>y "t :5 !y began to be rejuv5at$ by ar*+ or b[+ ( ! surface unaccompani$ by great fault+ or fractur+1 & _m canyons1 l t ( ! ,columbia ,riv]1 h s9ce be5 c>v$ out4 ,m5tion %\ld n[ be made ( ! vigor\s volcanic activity :i* took place 9 ! ,cascade & ,si]ra ,nevada ,ranges4 ,mo/ ( ?is activity occurr$ dur+ ,t]ti>y "t 7p>ticul>ly 9 ! latt] "p7 & x has cont9u$ ) dim9i%+ =ce practically to ! pres5t "t4 ,9 ,cali=nia /reams ( lava buri$ _m gold-be>+ riv] gravels :i* h yield$ ri* m9es4 ,_m well-kn[n m\nta9 peaks1 su* z ,%a/a1 ,lass51 ,pitt1 ,hood1 & ,ra9i]1 f nor!rn ,cali=nia to ,wa%+ton1 are great volcanic cones :i* date f ,t]ti>y "t1 & :i* are n[ mo/ly inactive4 ,t ?is volcanic activity has n yet altoge!r ceas$ is %[n by r5ew$ eruptions ( ,m\nt ,lass5 7or ,lass5 ,peak1 altitude #aj1dcg feet7 9 nor!rn ,cali=nia4 ,s9ce ! beg9n+ ( ?is r5ew$ activity 9 #aiad1 sev]al hundr$ outbur/s h occurr$4 ,no molt5 rock has fl[$ out1 b l>ge quantities ( rock fragm5ts1 du/ & /eam h be5 erupt$1 9 _m cases =m+ great cl\ds two or ?ree miles high ov] ! top ( ! m\nta9 7,plate #aj74 ,at ?is writ+ 7,octob]1 #aibj71 ,m\nt ,lass5 is /ill %[+ vigor\s activity4 ,at ,c9d] ,cone1 only t5 miles f ,m\nt ,lass51 !re 7 two eruptions ( c9d]s & a consid]able outp\r+ ( lava )9 ! la/ #bjj ye>s4 ,/ill o!r v rec5t c9d] cones occur 9 s\!a/]n ,cali=nia & ,arizona4 ,illu/ration3 ,fig4 #df4--,sket* map %[+ ! di/ribution ( volcanic rocks ( ,c5ozoic 7mo/ly ,t]ti>y7 ,age 9 we/]n ,nor? ,am]ica4 ,only "o volcano 7,m\nt ,lass51 ,cali=nia7 is n[ active 9 ! ,unit$ ,/ates prop]1 b a numb] are m or less active 9 ,mexico & ,c5tral ,am]ica4 7,data f ,willis1 ,u4 ,s4 ,geological ,survey47 ,"o ( ! greate/ lava fields 9 ! _w =ms ! ,columbian ,plateau betwe5 we/]n ,wyom+ 7includ+ ! ,yell[/one ,national ,p>k7 & ! ,cascade ,m\nta9s f nor!a/]n ,cali=nia to nor!rn ,wa%+ton4 ,x cov]s fully #bjj1jjj squ>e miles & is really consid]ably l>g] ?an %[n on ! map because ! lava 9 p>ts ( ! plateau region are cov]$ by v rec5t s$im5t>y mat]ials4 ,! great lava fields ( ! ,deccan1 ,india1 & ( ! plateau region ( we/]n ,mexico are comp>able 9 size to ! ,columbian field & ^! lava fields are all ( ! same age4 ,9 ! ,columbian ,plateau mo/ ( ! lava 0 p\r$ out dur+ lat] ,t]ti>y "t4 ,%eets ( molt5 rock1 av]ag+ fifty to "o hundr$ feet 9 ?ickness1 spread out ov] v>i\s p>ts ( ! region & pil$ up by ov]lapp+ lay]s "o ov] ano!r until ! lava plateau m ?an a mile high 0 built up4 ,_m hills & l[ m\nta9s 7 completely buri$ "u ! molt5 floods1 & 9 o!r places ! liquid rock masses fl[$ aga9/ ! high] m\nta9s4 ,= ?\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/4444 ,! plateau 0 long 9 build+4 ,betwe5 ! lay]s are f\nd 9 places old soil b$s & =e/ gr\nds & ! s$im5ts ( lakes4444 ,s anci5t are ! late/ floods 9 ! ,columbia ,riv] ,bas9 t !y h wea!r$ to a residual yell[ clay f ?irty to sixty feet 9 dep?1 & m>vel\sly ri* 9 ! m9]al sub/ances on :i* plants fe$4 ,9 ! ,snake ,riv] ,valley ! late/ lavas are mu* y\ng] 7,quat]n>y74 ,_! surfaces are s fre% & undecay$ t "h ! effusive eruptions may h cont9u$ to )9 ! p]iod ( human hi/ory4 7,w4 ,h4 ,norton47 ,_m ( ! lava lay]s are pla9ly visible :]e ! ,columbia ,riv] has cut its great gorge or canyon4 ,! ,snake ,riv] 9 places has sunk its *annel sev]al ?\s& feet into ! lava plateau )\t rea*+ und]ly+ rock4 ,bo? nor? & s\? ( ! ,columbian ,plateau !re 0 also mu* volcanic activity 9 ! ,rocky ,m\nta9 region dur+ ,t]ti>y "t4 ,a s+le =mation 9 ,colorado consi/s mo/ly ( volcanic a% or du/ ov] #b1jjj feet ?ick4 ,!re 0 also mu* volcanic activity ov] ! ,colorado ,plateau area ( s\!rn ,utah1 ,new ,mexico1 & ,arizona4 ,! volcanoes !re exhibit all /ages f ^? :i* are v rec5t & practically unaffect$ by erosion to o!rs :i* h be5 completely cut away ) ! exception ( ! cores or volcanic necks4 ,dur+ ! second half ( ! ,t]ti>y p]iod ! :ole region kn[n z ! ,great ,bas91 betwe5 ! ,si]ra ,nevada ,m\nta9s ( ,cali=nia & ! ,wasat* ,m\nta9s ( ,utah1 began to be affect$ by pr(\nd fault+ or fractur+ & tilt+ ( portions ( ! e>?'s cru/4 ,! two l>ge/ faults1 "o on ! we/]n side ( ! ,wasat* ,range & ! o!r on ! ea/]n side ( ! ,si]ra ,range1 are ea* hundr$s ( miles long4 ,ea* ( ^! ranges owes mo/ ( its pres5t altitude to ! uptilt+ ( great fault blocks1 & mo/ ( ! _m ne>ly nor?-s\? ,bas9 ,ranges ( ,nevada & ,utah are 9 reality rec5tly tilt$ fault blocks4 ,turn+ n[ to ! ,colorado ,plateau1 /udies h %[n t region to h be5 m or less p]iodically rais$ fully #bj1jjj feet s9ce ! beg9n+ ( ,t]ti>y "t1 b because ( pr(\nd erosion 9 ! meantime its pres5t altitude is only #f1jjj to #i1jjj feet4 ,dur+ late ,t]ti>y "t ! l& /ood at a mu* l[] level ?an to-day1 s t1 practically dur+ ! la/ p]iod 7,quat]n>y7 ( geologic "t1 ! region has be5 elevat$ to its pres5t position4 ,z a direct result ( ?is pr(\nd rejuv5ation ! ,colorado ,riv] has _h its erosive activity trem5d\sly increas$1 & x has c>v$ out ! mightie/ ( all exi/+ canyons--! ,gr& ,canyon4 ,! "w ( deep5+ & wid5+ ! canyon is /ill proce$+ at a rapid geologic rate4 ,z we h le>n$1 ! ,rocky ,m\nta9s & _m ( its subsidi>y ranges 7 =m$ by fold+ & uplift ( /rata t[>d ! close ( ! ,mesozoic era 7,cretace\s p]iod74 ,dur+ mu* ( ,t]ti>y "t ! newly =m$ m\nta9s _h be5 consid]ably r$uc$ by erosion4 ,!n1 late 9 ! ,t]ti>y p]iod1 mu* ( ! ,rocky ,m\nta9 region1 z well z mu* ( ! ,great ,pla9s area j ea/ ( ! m\nta9s1 became rejuv5at$ by diff]5tial uplift )\t any notable fold+ ( /rata4 ,we c tell t ?is g5]al uplift am\nt$ to at lea/ sev]al ?\s& feet because def9ite =mations ( relatively late ,t]ti>y /rata1 orig9ally horizontally deposit$ "u inl& bodies ( wat]1 gradually rise s t at ! base ( ! ,front ,range ( ! ,rockies !y are fully #c1jjj feet high] ?an !y are #bjj miles or m f>!r ea/4 ,?us1 ! orig9al fold+ & fault+ ( ! ,rockies1 ,t]ti>y volcanic activity1 late ,t]ti>y rejuv5ation1 & subsequ5t erosion acc\nt = ! pres5t altitude & relief features ( ! great ,rocky ,m\nta9 sy/em4 ,portions ( ! rejuv5at$ ,great ,pla9s region h be5 notably dissect$ by erosion s9ce ! late ,t]ti>y1 ?is be+ p>ticul>ly true ( ! s-call$ ,bad ,l&s1 especially 9 p>ts ( ,wyom+ & ,s\? ,dakota1 :]e mo/ly relatively s(t ,t]ti>y /rata h be5 cut to pieces4 ,turn+ our att5tion n[ to ! ea/]n half ( ! cont95t we f9d t all1 or ne>ly all1 ( x 0 m or less rais$ t[>d ! close ( ! ,t]ti>y p]iod4 ,practically ! :ole ,mississippi ,valley ea/ ( ! ,great ,pla9s1 z well z mu* ( ! c\ntry to ! nor? 9 ,canada1 0 elevat$ "s hundr$s ( feet & ! /reams h s9ce ! late ,t]ti>y uplift 7except :]e ! l& 0 ice-cov]$ dur+ ! ,ice ,age7 be5 at "w s9k+ _! *annels bel[ ! newly uprais$ surface4 ,z already po9t$ out1 ! l[l&s ( ! ,atlantic & ,gulf ,coa/al ,pla9s 7 mo/ly subm]g$ "u ! sea dur+ e>ly middle ,t]ti>y "t4 ,by ! close ( ! p]iod !y _h em]g$ practically to _! pres5t positions1 & !y h be5 only mod]ately affect$ by erosion4 ,we h /ill to expla9 ! exi/+ topography or relief ( a l>ge & important "p ( ea/]n ,nor? ,am]ica1 includ+ ! :ole ( ! ,appala*ian ,m\nta9s1 ,allegh5y ,plateau1 ,pi$mont ,plateau1 ,new ,york1 ,new ,engl&1 & ! ,canadian region to ! nor?4 ,z a />t+ po9t 9 ?is discussion we %\ld recall ! fact t1 aft] ! great ,appala*ian ,m\nta9 ,revolution t[>d ! close ( ! ,paleozoic era1 ! pr$om9ant geologic process :i* affect$ ! region "u consid]ation 0 erosion ?r\gh\t ! succe$+ ,mesozoic era4 ,by ab\t ! close ( ! ,mesozoic 7,cretace\s p]iod7 ! :ole region1 ) "s local exceptions1 has be5 worn d[n to a comp>atively smoo? pla9 7p5epla97 n f> above sea level4 ,local exceptions 7 ma9ly 9 ! ,new ,york & ,new ,engl& region z1 = example1 "s ( ! high] p>ts ( ! ,adirondack & ,:ite ,m\nta9s1 ,m\nt ,monadnock 9 s\!rn ,new ,hamp%ire1 & ,m\nt ,greylock 9 we/]n ,massa*usetts4 ,^! & o!r masses rose r conspicu\sly above ! g5]al level ( ! great pla9 ( erosion commonly call$ ! ,cretace\s p5epla9 because x is believ$ to h be5 well develop$ by ! close ( t p]iod4 ,! uplift ( ! va/ ,cretace\s p5epla9 ab\t ! beg9n+ ( ! ,c5ozoic era 7,t]ti>y p]iod7 0 an ev5t ( prime importance 9 ! rec5t geological hi/ory ( ea/]n ,nor? ,am]ica because x 0 lit]ally ! initial /ep 9 br++ ab\t ne>ly all ( ! exi/+ major relief features ( ! ,appala*ian-,new ,york-,new ,engl&-,/4 ,lawr5ce region4 ,! am\nt ( uplift 7unaccompani$ by fold+7 ( ! p5epla9 0 commonly f a few hundr$ to a few ?\s& feet ) ! greate/ am\nt 9 g5]al along ! ma9 tr5d ( ! ,appala*ians4 ,! fact %\ld be emphasiz$ t ne>ly all ! pr9cipal topographic features ( ! great uprais$ region h be5 produc$ by dissection 7erosion7 ( ! uplift$ p5epla9 surface4 ,?us ne>ly all ! valleys1 small & l>ge1 includ+ ^? ( ! ,/4 ,lawr5ce1 ,hudson1 ,mohawk1 ,connecticut1 & ,susquehanna1 h be5 c>v$ out by /reams s9ce ! uplift ( ! great p5epla94 ,! /reams :i* fl[$ ^u ! old l[-ly+ p5epla9 surface me&]$ sluggi%ly ov] deep alluvial or flood-pla9 deposits1 & _! c\rses 7 little if any det]m9$ by ! "* & /ructure ( ! und]ly+ rocks1 because1 ) few exceptions1 all rocks 7 worn d[n to ! g5]al pla9 level4 ,! uplift ( ! p5epla91 h[ev]1 caus$ great revival ( activity ( erosive p[] by ! /reams1 ! l>g] ones ( :i* soon cut ?r\gh ! loose sup]ficial alluvial deposits & !n into ! und]ly+ b$rock4 ,?us ! l>ge1 orig9al /reams _h _! c\rses well det]m9$ 9 ! ov]ly+ deposits1 & :5 ! und]ly+ rocks 7 rea*$ ! same c\rses _h to be pursu$ entirely )\t ref]5ce to ! und]ly+ rock "* & /ructure4 ,su* /reams are said to be sup]impos$ because !y h1 s to speak1 be5 let d[n ^u & into ! und]ly+ rock masses4 ,z ,pr(essor ,b]key has well said3 ,! l>g] riv]s1 ! great ma/] /reams1 ( ! sup]impos$ dra9age sy/em1 9 "s cases 7 s effici5t 9 ! corrosion ( _! *annels t ! discov]y ( discordant /ructures 79 ! und]ly+ rocks7 has n be5 ( suffici5t influ5ce to displace !m1 or rev]se !m1 or ev5 to %ift !m v f> f _! orig9al direct c\rse to ! sea4 ,!y cut directly across m\nta9 ridges because !y fl[$ ov] ! pla9 out ( :i* ^! ridges h be5 c>v$1 & because _! own erosive & transport+ p[] h exce$$ ^? ( any ( _! tribut>ies or neighbors4 ,f9e examples ( su* sup]impos$ /reams :i* are n[ entirely out ( h>mony ) ! /ructure ( regions ?r\gh :i* !y fl[ are ! ,susquehanna1 ,delaw>e1 & ,hudson4 ,?us ! ,susquehanna cuts across a :ole succession ( ,appala*ian ridges :ile1 9 accordance ) ! same explanation1 ! ,delaw>e cuts ?r\gh ! ,kittat9y range or ridge at ! fam\s ,delaw>e ,wat] ,gap4 ,! ridges are expla9$ z foll[s3 :ile ! great ma/] /reams 7 cutt+ deep tr5*es or *annels 9 h>d & s(t rock alike1 num]\s side /reams 7tribut>ies7 came into exi/5ce & naturally mo/ly develop$ along belts ( weak1 easily erod$ rock p>allel to geologic 7fold$7 /ructure4 ,?us ! ,appala*ian valleys h be51 & are be+1 =m$1 :ile ! ridges repres5t ! m resi/ant rock =mations :i* h m effectually /ood out aga9/ erosion4 ,! l[] ,hudson ,riv] fl[s at a consid]able angle across fold$ =mations above ! ,highl&s1 aft] :i* x passes ?\gh a deep gorge :i* x has cut into ! h>d granite & o!r rocks ( ! ,highl&s4 ,! simple explanation is t ! ,hudson _h its c\rse det]m9$ ^u ! surface ( ! uprais$ ,cretace\s p5epla91 & t x has be5 able to keep t c\rse 9 spite ( discordant /ructure & "* ( ! und]ly+ rocks4 ,9 a simil> mann] we may readily acc\nt = ! passage ( ! ,connecticut ,riv] ?r\gh a great gap 9 ! ,holyoke ridge or range ( h>d lava 9 we/]n ,massa*usetts4 ,be=e leav+ ?is "p ( our discussion we %all briefly pres5t "s evid5ce %[+ t ! ,new ,york-,new ,engl&-,/4 ,lawr5ce region at lea/ mu/ h be5 consid]ably high] %ortly be=e ! ,ice ,age 7,quat]n>y p]iod74 ,an old *annel ( ! ,hudson ,riv] has be5 trac$ ab\t #ajj miles ea/w>d beyond ! pres5t m\? ( ! riv] & x =ms a di/9ct tr5* "u ! %all[ sea 9 ! cont95tal %elf4 ,ev5 9 ! ,hudson ,valley1 _m miles above ,new ,york ,city1 ! b$rock bottom ( ! riv] lies hundr$s ( feet 7ne> ,we/ ,po9t1 #hjj feet7 bel[ sea level4 ,obvi\sly ?is subm]g$ *annel mu/ h be5 cut :5 ! l& 9 ! g5]al vic9ity ( ,new ,york ,city 0 fully #a1jjj feet high] ?an at pres5t4 ,t ! l& ?us /ood high] late 9 ! ,t]ti>y & possibly e>ly 9 ! ,quat]n>y p]iods is prov$ z foll[s3 7#a7 because mo/ ( ,t]ti>y "t mu/ h be5 ne$$ = ! riv] to erode su* a deep valley aft] ! initial uplift ( ! p5epla9 ab\t ! beg9n+ ( ! p]iod2 & 7#b7 because glacial deposits ( ,quat]n>y age fill$ ! =m] *annel to a consid]able dep?4 ,! valleys ( ! coa/ ( ,ma9e1 & ! subm]g$ l[] ,/4 ,lawr5ce ,valley 7,gulf ( ,/4 ,lawr5ce71 9 a simil> way lead u to conclude t ! region f>!r nor? 0 also notably high] j be=e ! ,ice ,age4 ,9 ! ea/]n hemisph]e e>ly 9 ! ,t]ti>y p]iod a great subm]g5ce set 9 & m>9e wat]s spread ov] mu* ( we/]n & s\!rn ,europe1 nor!rn ,africa1 & s\!rn ,asia4 ,! sites ( ! ,himalayas1 ,alps1 ,pyr5ees1 ,ap5n9es & o!r m\nta9s 7 !n mo/ly subm]g$4 ,a v rem>kable m>9e deposit1 made up almo/ :olly ( c>bonate ( lime %ells ( a s+le-cell$ animal call$ ,nummulites1 =m$ on ! floor ( ?is va/ly exp&$ e>ly ,t]ti>y m$it]ranean4 ,?is rock atta9s a ?ickness ( sev]al ?\s& feet4 ,x is d\btful if any o!r s+le =mation made up almo/ entirely ( ! %ells ( b "o species is at once s widespread & ?ick4 ,9 ! ,alps ?is rem>kable m>9e deposit may be se5 #aj1jjj feet above sea level1 & 9 ,tibet fully #bj1jjj feet4 ,mu* ( ! rock 9 ! ,egyptian pyramids 0 qu>ri$ f ?is =mation4 ,lat] 9 ! ,t]ti>y 9 ,eurasia & ,africa ! m>9e wat]s gradually became v re/rict$1 s t by ! close ( ! p]iod ! relations ( l& & sea 7 n /rik+ly diff]5t f ! pres5t1 al?\gh nor?we/]n ,europe1 l nor!a/]n ,nor? ,am]ica1 0 notably high] j be=e ! ,ice ,age ?an x is to-day4 ,eurasia witness$ trem5d\s cru/al di/urbances dur+ ! middle & lat] ,t]ti>y "t :51 due to int5se fold+ & uplift ( great zones1 ! ,himalayas1 ,caucasus1 ,alps1 ,pyr5ees1 ,ap5n9es1 & o!r great ranges 7 =m$4 ,! cru/al di/urbance 0 mo/ rem>kable 9 ! region ( ! ,alps1 :]e ! movem5t result$ 9 elevat+ & fold+ ! ,t]ti>y & old] /rata into ov]turn$1 recumb5t1 & ne>ly horizontal folds1 & pu%+ ! s\!rn or ,lepont9e ,alps ab\t sixty miles 7ov] a l[ angle fault fracture7 to ! nor?w>d into ! ,helvetic region4 ,erosion has s9ce c>v$ up ^! ov]?ru/ %eets1 leav+ remnants ly+ on f\ndations :i* belong to a m nor!rn portion ( ! anci5t 7e>ly ,t]ti>y7 sea4 ,mo/ not$ ( ^! residuals ( ov]?ru/ masses is ! ,matt]horn1 a mighty m\nta9 )\t roots1 a /rang] 9 a =eign geologic environm5t4 7,c4 ,s*u*]t47 ,! la/ p]iod ( geological "t--! ,quat]n>y--0 u%]$ 9 by ! spread+ ( va/ %eets ( ice ov] mu* ( nor!rn ,nor? ,am]ica & nor!rn ,europe1 & ?is ranks among ! mo/ int]e/+ & rem>kable ev5ts ( kn[n geological "t4 ,on fir/ ?\ght ! =m] exi/5ce ( su* va/ ice %eets seems unbelievable1 b ! ,ice ,age occurr$ s %ort a "t ago t ! records ( ! ev5t are p]fectly cle> & conclusive4 ,! fact ( ?is great ,ice ,age 0 discov]$ by ,l\is ,agassiz 9 #ahcg1 & fully ann\nc$ be=e ! ,briti% ,sci5tific ,association 9 #ahdj4 ,= "s ye>s ! idea 0 oppos$1 especially by advocates ( ! s-call$ iceb]g !ory4 ,n[1 h[ev]1 no important ev5t ( e>? hi/ory is m firmly e/abli%$1 & no /ud5t ( ! subject ev] que/ions ! fact ( ! ,quat]n>y ,ice ,age4 ,"s ( ! pro(s ( ! =m] pres5ce ( ! great ice %eet are z foll[s3 7#a7 poli%$ & /riat$ rock surfaces :i* are precisely l ^? produc$ by exi/+ glaci]s1 & :i* c\ld n possibly h be5 produc$ by any o!r ag5cy2 7#b7 glacial b[ld]s or erratics :i* are (t5 some:at r\nd$ & scrat*$1 & :i* h (t5 be5 transport$ _m miles f _! p>5t rock l$ges 7,plate #bj72 7#c7 true glacial mora9es1 especially t]m9al mora9es1 l t :i* ext5ds ! full l5g? ( ,long ,isl& & m>ks ! s\!rnmo/ limit ( ! great ice %eet2 & 7#d7 ! g5]ally widespread di/ribution ov] mo/ ( ! glaciat$ area ( het]og5e\s glacial dbris1 bo? un/ratifi$ & /ratifi$1 :i* is cle>ly transport$ mat]ial & typically re/s ^u ! b$rock by %>p contact4 ,! be/ kn[n exi/+ great ice %eets are ^? ( ,gre5l& & ,ant>ctica1 especially ! =m]1 :i* cov]s ab\t #ejj1jjj squ>e miles4 ,?is glaci] is s l>ge & deep t only an occasional high rocky m\nta9 projects above its surface1 & ! ice is kn[n to be sl[ly mov+ outw>d 9 all directions f ! int]ior to ! m>g9s ( ,gre5l&4 ,along ! m>g9s1 :]e melt+ is m rapid1 "s l& is expos$1 & (t5 ! ice fl[s out into ! ocean :]e x breaks (f to =m l>ge iceb]gs4 ,illu/ration3 ,fig4 #dg4--,map ( ,nor? ,am]ica %[+ ! area buri$ "u ice dur+ ! ,great ,ice ,age ( ! ,quat]n>y p]iod2 ! ?ree great glacial c5t]s2 & ! ext5t ( m\nta9 glaci]s 9 ! we/4 7,aft] ,u4 ,s4 ,geological ,survey47 ,! accompany+ map %[s ! area ( ne>ly #d1jjj1jjj squ>e miles ( ,nor? ,am]ica cov]$ by ice at ! "t ( maximum glaciation1 & also ! ?ree great c5t]s ( accumulation & disp]sal ( ! ice4 ,! directions ( fl[ f ^! c5t]s h be5 det]m9$ by ! /udy ( ! directions ( _m ?\s&s ( glacial scrat*es on rock l$ges4 ,! ,labradorean 7or ,laur5tide7 glaci] spread out #a1fjj miles to ! s\? to ,long ,isl& & ne> ! m\? ( ! ,ohio ,riv]4 ,! va/ ,keewat9 glaci] s5t a great lobe ( ice ne>ly z f> s\?1 t is into nor!rn ,miss\ri4 ,"o ( ! mo/ m>vel\s features ( ! ice disp]sion 0 ! great ext5sion ( ! ,keewat9 %eet f a l[ flat c5t] we/w>d & s\?w>d ov] :at is n[ a semi>id pla91 ris+ 9 ! direction 9 :i* ! ice mov$1 :ile ! m\nta9 glaci]s on ! we/ 7,cordill]an region71 :]e n[ kn[n1 pu%$ ea/w>d b little beyond ! foot-hills4 7,*amb]l9 & ,salisbury47 ,! ,labradorean & ,keewat9 ice %eets ev]y:]e coalesc$ except 9 two places4 ,"o ( ^! is an area ( ab\t #aj1jjj squ>e miles mo/ly 9 s\?we/]n ,wiscons94 ,9 spite ( sev]al ice invasions dur+ ! ,ice ,age1 ?is area1 hundr$s ( miles nor? ( ! s\!rn limit ( ! ice %eets1 0 nev] ice-cov]$4 ,!re is a total abs5ce ( records ( glaciation )9 ?is area1 & s we "h h an excell5t sample ( ! k9d ( topography :i* prevail$ ov] ! nor!rn ,mississippi ,valley j be=e ! adv5t ( ! ice4 ,a mu* small]1 nonglaciat$ area occurs 9 nor!a/]n ,miss\ri ne> ! s\!rn limit ( ice ext5sion4 ,! ,cordill]an ice %eet 0 ! smalle/ ( ! ?ree1 & x 0 probably n su* a cont9u\s mass ( ice1 ! high] m\nta9s project+ above its surface4 ,a surpris+ fact is t nei!r ?is ice %eet nor any o!r ov]spread nor!rn ,alaska1 :i* is well )9 ! ,arctic ,circle1 dur+ ! ,ice ,age4 ,m ?an likely ! temp]ature 0 l[ en\gh1 b precipitation ( sn[ 0 n suffici5t to p]mit ! build+ up ( a great glaci]4 ,at ! same "t t ne>ly #d1jjj1jjj squ>e miles ( ,nor? ,am]ica 7 ice-cov]$1 ab\t #fjj1jjj squ>e miles ( nor!rn ,europe 7 buri$ "u ice :i* spread f ! "o great c5t] ov] ,sc&9avia s\?we/1 s\?1 & s\!a/ ov] mo/ ( ! ,briti% ,isles1 well into ,g]many1 & well into ,russia4 ,9 bo? ,nor? ,am]ica & ,europe ! high m\nta9s1 well s\? ( ! great glaci] limits1 especially ! ,si]ras1 ,rockies1 ,alps1 ,pyr5ees1 & ,caucasus1 support$ _m l>ge local glaci]s 9 valleys :i* n[ conta9 none at all or only relatively small ones4 ,records ( glaciation1 su* z glacial scrat*es1 b[ld]s1 lakes1 etc41 occur high up 9 ! ,:ite & ,gre5 ,m\nta9s1 ,adirondacks1 ,catskills1 & ! ,b]k%ire ,hills1 ?us prov+ t ! ice mu/ h be5 at lea/ "s ?\s&s ( feet ?ick ov] ,new ,engl& & ,new ,york4 ,we h good reason to believe t ev5 ! highe/ summits1 except possibly 9 ! ,catskills1 f #d1jjj to ov] #f1jjj feet above sea level1 7 completely subm]g$ "u ! ice4 ,on top ( a m\nta9 ( ,ar*eozoic granite ne>ly #d1jjj feet 9 altitude1 fac+ ! ,/4 ,lawr5ce ,valley 9 nor!rn ,new ,york1 ! writ] has f\nd _m fragm5ts ( s&/one :i* 7 pick$ (f by ! ice 9 ! l[ valley1 mov$ s\?w>d a good _m miles1 & uphill sev]al ?\s& feet to ! top ( ! m\nta94 ,! read] may wond] h[ a great glaci] at lea/ a mile ?ick 9 nor!rn ,new ,york c\ld h ?9n$ out to disappe>ance )9 ! %ort di/ance to ! s\!rn bord] ( ! ,/ate1 b obs]vations on exi/+ l>ge glaci]s %[ t x is q ! habit = !m to ?9 out v rapidly ne> _! m>g9s1 ?us produc+ /eep ice fronts4 ,! fact t glacial ice fl[s z ?\gh x 7 a visc\s sub/ance is well kn[n f /udies ( valley glaci]s 9 ! ,alps & ,alaska1 & ! great ice %eet ( ,gre5l&4 ,a common assumption1 ei!r t ! l& at "o ( ! great c5t]s ( ice accumulation dur+ ! ,ice ,age mu/ h be5 _m ?\s&s ( feet high]1 or t ! ice mu/ !re h be5 imm5sely ?ick1 9 ord] to p]mit ice fl[age s f> out f ! c5t]1 is n necess>y4 ,visc\s t> sl[ly p\r$ ^u a level surface w gradually fl[ out 9 all directions1 & at no "t ne$ ! t> at ! c5t] ( accumulation be v mu* ?ick] ?an else:]e4 ,! movem5t ( glacial ice f ! great c5t]s ( disp]sal dur+ ! ,ice ,age 0 mu* ! same 9 pr9ciple1 only 9 ! case ( ! glaci]s ! accumulations ( sn[ & ice 7 by no means conf9$ to ! imm$iate c5t]s4 ,! fronts ( ! va/ ice %eets1 l ^? ( ord9>y valley glaci]s1 mu/ h und]gone _m advances & retreats ( great] or less consequ5ce4 ,9 ! nor!rn ,mississippi ,valley1 & also 9 ,europe1 !re is positive pro( = five or six important advances & retreats ( ! ice :i* gave rise to ! true int]glacial /ages4 ,! /ronge/ evid5ce is ! pres5ce ( successive lay]s ( glacial 7mora9ic7 dbris pil$ "o ^u ano!r1 a giv5 lay] (t5 hav+ be5 oxidiz$1 erod$1 & ev5 cov]$ ) plant life be=e ! next or ov]ly+ lay] 0 deposit$4 ,su* is ! condition ( ?+s ?r\gh\t mu* ( ,i[a1 :]e wells sunk into ! glacial deposits commonly pass ?r\gh lay]s ( p>tly decompos$ vegetable matt] at dep?s ( f #ajj to #cjj feet4 ,ne> ,toronto1 ,canada1 ! f9d+ ( w>m climate plants betwe5 two glacial deposits proves t ! climate !re dur+ an int]glacial /age 0 mu* l t ( ! s\!rn ,/ates to-day4 ,dur+ ! great int]glacial /ages ! va/ glaci]s 7 notably re/rict$ 9 size1 & 9 "s or possibly all1 cases !y may h :olly disappe>$ f ! cont95t4 ,9 =m] ye>s !re 0 a t5d5cy to ascribe mighty erosive p[] to ! va/ sl[-mov+ ice %eets1 b to-day sc>cely any geologi/ w\ld hold t ! ice really produc$ l>ge valleys solely by ice erosion1 or t m\nta9s 7 notably cut d[n4 ,?r\gh\t ! glaciat$ region1 especially t[>d ! nor?1 ! deep preglacial residual soils & rott5 rocks 7 ne>ly all sc\r$ (f by ! passage ( ! ice4 ,t ! ice1 :]e prop]ly %od ) rock fragm5ts1 actually erod$ to at lea/ little dep?s into h>d & fre% rocks is well kn[n1 b ! evid5ce is cle> & conclusive t ! preglacial hills & m\nta9s1 & mo/ ( ! valleys 7includ+ all ! l>ge ones71 7 r>ely m ?an a little modifi$ 9 %ape & size4 ,"o ( ! pr9cipal effects ( ! ,ice ,age is ! widespread di/ribution ( glacial deposits1 & o!r deposits :i* 7 =m$ "u wat] 9 direct association ) ! ice4 ,su* mat]ials h be5 describ$ 9 ! *apt] on ,glaci]s & ,_! ,"w4 ,z a direct result ( ! ,ice ,age1 _m ?\s&s ( lakes came into exi/5ce ?r\gh\t ! glaciat$ region :]e few1 if any1 previ\sly exi/$4 ,_m ( ^! la/$ only :ile ! ice 0 pres5t because _! wat]s 7 held up by walls ( ice act+ z dams4 ,?\s&s ( o!rs /ill p]si/1 mo/ ( ^! hav+ _! wat] levels ma9ta9$ by dams ( glacial dbris left by ! ice across valleys4 ,good examples ( lakes ( bo? types1 includ+ a summ>y ( ! rem>kable hi/ory ( ! ,great ,lakes1 are consid]$ 9 ! *apt] on ,a ,/udy ( ,lakes4 ,_m dra9age *anges1 gorges1 & wat]falls h also directly result$ f ! great ,ice ,age4 ,9 fact x is n too mu* to say t practically all true gorges & wat]falls ( ! glaciat$ region h orig9at$ z a direct result ( ! ,ice ,age4 ,! mo/ rem>kable comb9ation ( wat]fall & gorge ?us produc$ is t ( ! _w-fam\s ,niag>a1 describ$ 9 ! *apt] on ,/ream ,"w4 ,n only are ,niag>a ,falls & gorge ( po/glacial orig9 b !re 0 no ,niag>a ,riv] z su* be=e ! ,ice ,age4 ,9 ,new ,york ! well-kn[n ,ausable ,*asm1 ,tr5ton ,falls ,gorge1 & ,watk9s ,gl5 are all excell5t examples ( gorges cut s9ce ! ,ice ,age by /reams :i*1 because _! old valleys 7 fill$ ) glacial dbris1 h be5 =c$ to take new c\rses4 ,a gorge ( v special int]e/ is t at ,little ,falls 9 c5tral ,new ,york4 ,?is gorge1 two miles long1 ) its precipit\s walls hundr$s ( feet high1 is ! mo/ important gateway = traffic betwe5 ! ,atlantic bord] & ! ,great ,lakes region4 ,! bottom ( ?is defile conta9s six tracks ( ! ,new ,york ,c5tral & ,we/ ,%ore ,railroads1 ! ,b>ge ,canal1 an important highway1 & ! ,mohawk ,riv]4 ,be=e ! ,ice ,age !re 0 a /ream divide in/ead ( a gorge1 sev]al hundr$ feet above ! pres5t riv] level4 ,dur+ a late /age ( ! ,ice ,age1 :5 ! ,great ,lakes dra9$ ?r\gh ! ,mohawk ,valley1 a trem5d\s volume ( wat] pass$ ov] ! divide & cut x d[n to =m ne>ly all ( ! gorge except ! inn] or bottom tr5* :i* has s9ce be5 erod$ by ! ,mohawk ,riv]4 ,illu/ration3 ,fig4 #dh4--,sket* map ( ! region betwe5 ,lake ,george & ,s*5ectady1 ,new ,york1 %[+ h[ c]ta9 ( ! ma9 dra9age c\rses h be5 revolutioniz$ by ! great retreat+ ice %eet & ! deposits x left4 ,preglacial c\rses %[n by dott$ l9es only :]e ess5tially diff]5t f ! pres5t /reams4 7,by ! au?or1 z publi%$ by ,new ,york ,/ate ,museum47 ,only a few ( ! num]\s /ream *anges directly due to ! ,ice ,age w be briefly ref]r$ to4 ,c]ta9 ( ! pr9ciples involv$ are exceptionally well illu/rat$ 9 ! g5]al vic9ity ( ,s>atoga ,spr+s & ,lake ,george1 ,new ,york4 ,dur+ ! retreat ( ! great glaci] a lobe ( ice occupi$ ! ,lake ,george ,valley & =c$ ! ,hudson ,riv] we/ ov] a divide at ,/ony ,creek4 ,!n1 because ( heavy glacial deposits ne> ,cor9?1 ! ,hudson c\ld n cont9ue s\? ?r\gh :at _h be5 ! preglacial valley ( ,luz]ne ,riv]1 b x 0 =c$ ea/w>d ov] a divide 9 a l[ m\nta9 ridge to ,gl5s ,falls4 ,! rem>kable %ift ( ! ,sac&aga ,riv] f its preglacial *annel 0 caus$ by ! build+ up ( a great mora9ic ridge across ! valley 9 ! vic9ity ( ,broadalb94 ,! dra9age ( ! bas9 ( ! upp] ,ohio ,riv] has also be5 revolutioniz$ z a result ( ! glaciation4 ,all ! dra9age ( we/]n ,p5nsylvania pass$ nor?w>d into ,lake ,erie j be=e ! ,ice ,age in/ead ( s\?we/w>d ?r\gh ! ,ohio ,riv] z at pres5t4 ,riv]s z l>ge z ! ,mississippi & ! ,miss\ri 7 also m or less locally deflect$ f _! preglacial c\rses4 ,?us ! ,miss\ri1 :i* 9 preglacial "t foll[$ ! ,james ,riv] ,valley ( ea/]n ,s\? ,dakota1 0 =c$1 by a great lobe ( retreat+ ice1 to f9d its pres5t c\rse _m miles f>!r we/4 ,h[ long ago did ! ,ice ,age end8 ,9 seek+ an answ] to ?is "q we %\ld be> 9 m9d n only ! fact t ! ,ice ,age end$ at diff]5t times1 accord+ to latitude1 ! m s\!rn di/ricts hav+ be5 fir/ fre$ f ice1 b also ! fact t approximately #d1jjj1jjj squ>e miles ( ! pol> regions are n[ ice-cov]$1 s t 9 a real s5se ^? portions ( ! e>? are /ill 9 an ,ice ,age4 ,"s ( ! be/ e/imates ( ! l5g? ( po/glacial "t = a giv5 place are bas$ ^u ! rate ( recession ( ,niag>a ,falls1 ! av]age ( ! e/imates be+ ab\t #be1jjj ye>s4 ,! evid5ce = ?is conclusion is briefly set =? 9 ,*apt] ,,iii4 ,a c>eful /udy ( ! rate ( recession ( ,/4 ,an?ony ,falls1 ,m9nesota1 has l$ to ! conclusion t ! la/ retreat ( ! ice occurr$ !re f #aj1jjj to #af1jjj ye>s ago4 ,c]ta9 clays deposit$ "u tidewat] s9ce ! la/ )drawal ( ice 9 ,sw$5 %[ a rem>kable succession ( alt]nat+ lay]s ?\ght to repres5t seasonal *anges4 ,by c\nt+ ! lay]s x has be5 e/imat$ t ,/ockholm 0 fre$ f ice only #i1jjj ye>s ago4 ,al?\gh ! actual duration ( ! ,ice ,age is by no means accurately kn[n1 we c be q sure t ! "t repres5t$ is f> long] ?an t ( po/glacial "t4 ,t x mu/ h la/$ fully #ejj1jjj ye>s seems c]ta9 :5 due consid]ation is giv5 to am\nt ( "t necess>y to br+ ab\t ! repeat$ *anges ( climate betwe5 ! glacial & int]glacial /ages2 ! am\nt ( plant accumulation dur+ ! int]glacial /ages2 ! am\nt ( wea!r+ & erosion ( ! v>i\s lay]s ( glacial deposits4 ,"s e/imates run z high z #a1ejj1jjj ye>s = ! duration ( ! ,ice ,age1 & an av]age is ab\t #a1jjj1jjj ye>s1 :i* probably indicates1 at lea/ r\ghly1 ! ord] ( magnitude ( ! "t involv$4 ,:5 x is consid]$ n only t ! fact ( ! great ,ice ,age 0 n ev5 ?\ght ( until #ahcg1 b also t _m factors ent] into ! g5]al problem ( ! climate ( geologic "t1 x is n surpris+ t ! cause 7or causes7 ( ! glacial climate is /ill n def9itely kn[n4 ,a few ( ! v>i\s hypo!ses :i* h be5 advocat$ to acc\nt = ! glacial climate w n[ be v briefly ref]r$ to4 ,"o is t ! increas$ cold 7n m ?an #aj to #ae degrees = ! ye>ly av]age7 0 br\ght ab\t by ! notably increas$ altitudes ( late ,t]ti>y & e>ly ,quat]n>y times 9 nor!rn ,nor? ,am]ica & ,europe4 ,9 ?is connection x is int]e/+ to note t ! f\r times ( real glaciation dur+ geologic "t 7mid-,prot]ozoic1 e>ly ,paleozoic1 late ,paleozoic1 & e>ly ,c5ozoic7 did occur directly aft] great cru/al di/urbances & notable uplifts ( l&4 ,accord+ to ?is hypo!sis ! int]glacial /ages w\ld h to be expla9$ by a r unreasonable assumption ( repeat$ ris+ & s9k+ ( ! glaciat$ l&s4 ,ano!r hypo!sis1 long held 9 favor1 is bas$ ^u c]ta9 a/ronomical consid]ations4 ,?us we n[ h w9t] 9 ! nor!rn hemisph]e :5 ! e>? is ne>e/ ! sun1 b 9 ab\t #aj1ejj ye>s1 due to wobbl+ ( ! e>? on its axis1 our w9t] w occur :5 ! e>? is f>!/ f ! sun1 ?us mak+ ! w9t]s long] & cold]1 & ! summ]s %ort] & hott]4 ,aft] a mu* long] p]iod ( "t ! e>? w be millions ( miles f>!r f ! sun 9 w9t] ?an 9 summ] & ?is w\ld /ill fur!r acc5tuate ! l5g? & coldness ( ! w9t]s4 ,! int]glacial /ages repres5t ! #aj1ejj ye> p]iods :5 ! e>? 9 w9t] 7nor!rn hemisph]e7 is ne>e/ ! sun4 ,a difficulty 9 ! way ( accept+ ?is hypo!sis is t x is inconceivable t ea* glacial & int]glacial /age la/$ only #aj1ejj ye>s4 ,ano!r objection to ! hypo!sis z an explanation ( ,ice ,ages is t x is directly oppos$ by ! fact ( widespread glaciation at l[ latitudes ei!r side ( ! equator dur+ ! late ,paleozoic ,ice ,age4 ,ano!r hypo!sis is bas$ ^u v>iations 9 quantity ( c>bonic acid gas & wat] vapor 9 ! air4 ,increase or decrease ( ^! con/itu5ts causes increase or decrease ( temp]ature because !y h high capacities = absorb+ heat4 ,! great elevation ( ! l& at ! close ( ! ,t]ti>y seems to af=d conditions favorable bo? = ! consumption ( c>bon dioxide 9 l>ge quantities 7by wea!r+ ( rocks7 & = ! r$uction ( ! wat] cont5t ( ! air4 ,depletion ( ^! heat-absorb+ elem5ts 0 equival5t to ! ?9n+ ( ! !rmal blanket :i* !y con/itute4 ,if x 0 ?9n$1 ! temp]ature 0 r$uc$4444 ,by v>iations 9 ! consumption ( c>bon dioxide1 especially 9 its absorption & escape f ! ocean1 ! hypo!sis attempts to expla9 ! p]iodicity ( glaciation 7i4e41 glacial & int]glacial /ages74 7,*amb]l9 & ,salisbury47 ,/ill ano!r sugge/$ explanation is bas$ ^u v>iability ( am\nt ( heat radiat$ by ! sun4 ,slight v>iations are n[ kn[n to take place1 & possibly 9 ! pa/ dur+ c]ta9 p]iods ( "t ^! v>iations may h be5 suffici5tly great to cause a glacial climate ) int]glacial /ages4 ,"h1 z 9 ! case ( s _m o!r great natural ph5om5a1 a s+le1 simple explanation does n seem suffici5t to acc\nt = all ! features ( ! sev]al well-kn[n glacial epo*s ( geologic "t4 ,two or m hypo!ses1 or p>ts ( hypo!ses1 mu/ m ?an likely be comb9$ to expla9 a p>ticul> ,ice ,age4 ,,*apt] ,,xvii ,,evolution ,,( ,,plants ,h we any k reg>d+ ! beg9n+ ( life on our planet8 ,our answ] to ?is "q mu/ be decid$ly 9 ! negative4 ,we c1 h[ev]1 be v positive 9 reg>d to two important matt]s conc]n+ life 9 e>ly geological "t1 namely1 t plants mu/ h exi/$ be=e animals1 & t ! v olde/ kn[n 7,ar*eozoic7 rocks ( ! e>? conta9 ve/iges ( organisms4 ,we may be sure t plants prec$$ animals because animal life ultimately dep5ds ^u plants = its food supply or1 9 o!r words1 all animals c\ld nev] h be5 c>nivor\s4 ,n[1 if we c prove t organisms exi/$ dur+ ,ar*eozoic "t1 x is evid5t t plants at lea/ mu/ h liv$ 9 t olde/ kn[n era ( e>? hi/ory4 ,t liv+ ?+s did !n exi/ is prov$ by ! common occurr5ce ( graphite1 a cry/alliz$ =m ( c>bon1 9 ! olde/ kn[n ( ! ,ar*eozoic rocks4 ,! facts t flakes ( graphite are abundantly scatt]$ ?r\gh _m lay]s ( /rata ( ,ar*eozoic ,age1 & t adjac5t lay]s ( /rata conta9 su* v>y+ am\nts ( graphite1 r5d] x practically c]ta9 t su* graphite repres5ts ! c>bon ( organisms4 ,graphite exi/+ "u su* conditions c\ld n be ( igne\s orig94 ,c>bonace\s or bitum9\s /rata1 s call$ because !y conta9 m or less decompos$ organic matt]1 w\ld1 :5 cry/alliz$ "u conditions ( metamorphism1 yield graphite-be>+ rocks exactly l ^? ( ,ar*eozoic ,age1 & !re is e reason to believe t ?is 0 _! orig94 ,b1 s9ce only graphite 7c>bon7 ( ! ,ar*eozoic organisms rema9s1 ! re/ hav+ disappe>$ ?r\gh *emical *ange or decomposition1 x is impossible to say :e!r mu* or all ( x repres5ts orig9al plants or animals4 ,9 any case we c be v sure ab\t ! exi/5ce ( plants 7probably v simple or primitive types7 9 ,ar*eozoic "t1 b ! pres5ce ( any =m ( animal life has n be5 prov$4 ,9 ! next1 or ,prot]ozoic era1 "s plants & animals ( def9ite types are kn[n to h exi/$ &1 f "h on 9 ! pres5t *apt]1 x is our purpose to consid] ! sali5t po9ts 9 ! geological hi/ory ( plants1 tak+ up ! ma9 types 9 ! regul> ord] ( _! appe>ance f ! remote ,prot]ozoic days to ! pres5t4 ,! v olde/ kn[n def9itely det]m9able fossils ( any k9d are ! m or less r\nd$ masses ( crudely conc5tric lay]s ( c>bonate ( lime f "o to fifte5 in*es 9 diamet] f\nd 9 middle ,prot]ozoic lime/one ( we/]n ,ont>io1 ,canada4 ,simil> =ms are abundant 9 late ,prot]ozoic /rata ( ,montana4 ,!y occur 9 l>ge numb]s z lay]s or reefs1 9 _m cases repeat+ !mselves ?r\gh hundr$s or ev5 ?\s&s ( feet ( /rata4 ,c>eful /udies h %[n t ^! =ms are ! limey secretions ( "s ( ! v simple/ types ( plants1 t is ?allophytes 7e4g41 seawe$s71 :i* liv$ 9 wat]4 ,be=e proce$+ to describe ! plants ( ,paleozoic & lat] "t1 ! read] %\ld be impress$ ) ! important fact t plants ( high] & high] types came into exi/5ce ?r\gh\t geological "t 9 almo/ exactly ! botanical ord] ( _! classification1 t is to say1 f ! v simple/ types 7?allophytes7 ( ,prot]ozoic "t !re 7 gradually evolv$1 ?r\gh ! long geological ages1 high] & high] plant =ms rea*+ a climax 9 ! complex & highly organiz$ plants ( ! pres5t "t4 ,?is is ! mo/ significant g5]al fact 9 reg>d to ! geological hi/ory ( plants4 ,= ! conv5i5ce ( ! read] ! l>ge/ subdivisions 9 ! classification ( plants are "h giv54 ,,outl9e ,,classification ,,( ,,plants ,i4 ,cryptogams #a4 ,?allophytes 7e4g41 seawe$s1 mu%rooms7 7se$less & #b4 ,bryophytes 7e4g41 mosses7 fl[]less7 #c4 ,pt]idophytes 7e4g41 club mosses1 horsetails1 f]ns7 ,,ii4 ,pt]idosp]ms 7se$-be>+1 7e4g41 se$ f]ns--:olly ext9ct7 fl[]less7 ,,iii4 ,phan]ogams #a4 ,gymnosp]ms 7e4g41 cycads1 conif]s7 7se$-be>+1 #b4 ,angiosp]ms 7e4g41 grasses1 lilies1 fl[]+7 oaks1 roses7 ,?r\gh\t ! fir/ two p]iods--,cambrian & ,ordovician--( ! ,paleozoic era1 plant life appe>s to h made little or no progress t[>d high] =ms4 ,! v simple ,?allophytes 7e4g41 seawe$s7 cont9u$ to secrete conc5tric lay]s ( c>bonate ( lime 9 almo/ exactly ! same way z dur+ ! middle & late ,prot]ozoic era4 ,rem>kable reefs ( su* =ms occur 9 ! late ,cambrian lime/one ne> ,s>atoga ,spr+s1 ,new ,york1 :]e "o locality has be5 set aside z a /ate p>k4 ,dur+ ! ,ordovician !re 7 seawe$s ( ! m famili> bran*+ types )\t c>bonate ( lime supports1 & ^! h left v p]fect impressions 9 "s ( ! ,ordovician /rata4 ,dur+ ! ,silurian p]iod seawe$s cont9u$1 z1 9 fact1 !y did ?r\gh\t succe$+ geologic "t to ! pres5t4 ,! ,silurian /rata seem to conta9 "s ve/iges ( ! fir/-kn[n l& plants1 ?\gh ! records are meag] & "s ( ! specim5s are ( a d\btful "*4 ,mo/ int]e/+ ( all is a f]n or f]nlike plant f\nd 9 ,france4 ,:5 we consid] ! pr(usion ( l& plants 7all ( relatively simple types7 ( ! next or ,devonian p]iod1 x seems c]ta9 t _! prog5itors mu/ h exi/$ 9 ! ,silurian1 & _! rema9s may v likely be discov]$4 ,beg9n+ ) ! ,devonian p]iod ( ! ,paleozoic era ! records %[ t important advances _h tak5 place 9 ! evolution ( ! plant k+dom4 ,among ! v simple ,?allophyte plants "s seawe$s ( unusually l>ge size occur 9 fossil =m1 b ! important fact is t all ! pr9cipal subdivisions ( ! typical high] non-fl[]+ plants 7,pt]idophytes7 z well z ,pt]idosp]ms1 & ev5 "s primitive repres5tatives ( ! l[] ord] fl[]+ plants 7gymnosp]ms7 7 well repres5t$ 9 ! ,devonian4 ,our k ( l& plants e>li] ?an ! ,devonian am\nts to almo/ no?+ & !y c]ta9ly c\ld n h be5 at all prom95t1 b ! fossil records make x v cle> t _m ,devonian l& areas 7 clad ) ri* & div]sifi$ plant life4 ,!re 7 ev5 =e/s1 probably ! fir/ on e>?1 b !y 7 f> diff]5t1 bo? 9 g5]al & 9 p>ticul>1 f ^? ( to-day because ! trees 7 all ( exceptionally l[ organization types4 ,dur+ ! next two p]iods--,mississippian & ,p5nsylvanian--!re 0 no really important progress 9 ! evolution ( plants1 & s9ce ^! rem>kable types ( l& plants h left su* wond]fully pres]v$ records 9 /rata ( ! ,p5nsylvanian or great ,coal ,age1 we %all proce$ to descriptions ( ! ma9 types ( t "t1 especially ^? :i* contribut$ to ! =mation ( b$s ( coal4 ,z %[n by ! abundant records1 ! l& plant life ( ,p5nsylvanian "t mu/ h be5 n only prolific b exce$+ly v>i$4 ,?\s&s ( species h be5 une>!d f ! coal-be>+ =mations alone1 & ^! mu/ repres5t only a fraction ( all species ( plants :i* liv$ dur+ ! p]iod4 ,mo/ prom95t ( all 7 ! giant ,lycopods con/itut+ ! l[e/ ma9 subdivision ( ! ,pt]idophytes 7see above classification74 ,^! great1 non-fl[]+ plants 7 at once ! bigge/1 mo/ common & conspicu\s trees ( ! ext5sive swamp =e/s1 & !y 7 ! greate/ contributors to ! =mation ( coal 7,plate #ae74 ,_m species h be5 describ$4 ,!y commonly atta9$ heights ( #ej to #ajj feet & diamet]s ( #b to #f feet4 ,9 "o important type ! fairly num]\s bran*es bri/l$ ) /iff1 ne$le-%ap$ leaves4 ,:5 ! leaves dropp$ (f ! old] or trunk portions1 sc>s 7 left spirally arrang$ ar\nd ! trunks ( ! trees4 ,9 ano!r important type ! leaf sc>s 7 v]tically arrang$ on ! l[] portions ( ! tree trunks4 ,! upp] portions ( ! trunks 7r>ely bran*$7 7 ?ickly set ) long1 sl5d] leaves1 :i* 9 "s species 7 two or ?ree feet long4 ,an int]e/+ fact is t ! inn] p>ts ( ! trunks ( ! great ,lycopods 7 fill$ ) s(t1 pi?y mat]ial4 ,?is expla9s :y ! fossil trees are ne>ly always flatt5$ out1 z a result ( burial )9 ! e>?4 ,! nonbran*+ type ( ,lycopod has be5 totally ext9ct = millions ( ye>s1 :ile ! bran*+ type is to-day repres5t$ only by small1 mo/ly delicate1 trail+ plants famili>ly kn[n z club mosses & gr\nd p9es4 ,! mo/ conspicu\s trees ( ! great ,p5nsylvanian l[l&s & swamps h1 inde$1 left meag] mod]n repres5tatives1 & "h we h an excell5t illu/ration ( a once prom95t gr\p ( plants :i* has dw9dl$ away almo/ to ext9ction4 ,ano!r common type ( ,p5nsylvanian vegetation 0 ! s-call$ horsetail plant or giant ru%4 ,! mu* small] sc\r+ ru%1 repres5t$ by sev]al species to-day1 is ! direct desc5dant ( ?is type :i*1 dur+ lat] ,paleozoic "t1 grew to be #ej to #ij feet high & #a to #b feet 9 diamet]4 ,! long1 sl5d] trunks fill$ ) pi? 7 segm5t$ ) v>i\sly %ap$ leaves arrang$ 9 :orls ar\nd ! jo9ts4 ,a f9e1 v]tical-flut$ /ructure )\t leaf sc>s *>act]iz$ ! surfaces ( ! trunk4 ,rec5t /udy has %[n t _m ( ! ,p5nsylvanian plants1 long class$ z true f]ns1 7 really se$ f]ns1 z describ$ bel[4 ,_m ( ! true f]ns grew to be real trees up to fifty or sixty feet high1 b all ,paleozoic types 7 primitive 9 /ructure z comp>$ ) mod]n f]ns4 ,v rem>kable among ! lat] ,paleozoic plants 7 ! ,pt]idosp]ms1 repres5t$ by ! s-call$ se$ f]ns4 ,^! n[ :olly ext9ct plants seem to h =m$ ! connect+ l9k betwe5 ! se$less1 fl[]less plants 7,cryptogams7 & ! se$-be>+1 fl[]+ plants 7,phan]ogams71 because !y bore se$s b n fl[]s4 ,_m ( !m 7 small & h]bace\s1 b o!rs 7 tall trees1 9 g5]al appe>ance resembl+ ! tree f]ns4 ,se$ f]ns1 :i* play su* an important "p 9 ! evolution ( plants1 are n kn[n to h exi/$ aft] ,paleozoic "t4 ,dur+ ! latt] half ( ! ,paleozoic era "s v primitive types ( fl[]+ plants 7,gymnosp]ms7 exi/$4 ,mo/ abundant ( ^! 7 ! s-call$ ,cordaites1 :i* 7 ! talle/ trees ( ! "t1 "s hav+ rea*$ heights ( ov] #ajj feet4 ,! upp] portions only bore num]\s bran*es suppli$ ) _m simple1 p>allel-ve9$1 /rap-%ap$ leaves up to six feet long & six in*es wide4 ,except+ ! pi?y cores ! trunks ( ^! trees 7 ( real wood cov]$ ) ?ick b>k4 ,trees ( ?is k9d became ext9ct 9 ! e>ly ,mesozoic era4 ,v late 9 ! ,paleozoic 7,p]mian p]iod7 two o!r types ( ! simple fl[]+ plants 7,gymnosp]ms7 made _! appe>ance4 ,^! 7 ! cycads & conif]s1 :i* 7 ! mo/ conspicu\s trees dur+ ! fir/ two p]iods ( ! ,mesozoic era4 ,! cycads rea*$ _! culm9ation 9 ! ,jurassic p]iod1 b !y /ill exi/ 9 modifi$ =m 9 "s p>ts ( ! _w4 ,! %ort1 /\t trunk 0 cr[n$ ) long1 /iff1 palm-l leaves4 ,9 fact1 ! cycads are di/antly relat$ to ! palms1 :i* belong to a high] gr\p ( plants4 ,"s specim5s ( cycads1 especially f ! ,mesozoic /rata ( ,s\? ,dakota1 are s wond]fully fossiliz$ t ev5 ! detail$ /ructures ( trunks1 leaves1 fl[]s1 & se$s are s p]fectly pres]v$ t almo/ z mu* is kn[n ab\t ^! plants ( millions ( ye>s ago z ?\gh !y 7 liv+ =ms4 ,! conif]s1 ) :i* are class$ pres5t-day p9es1 spruces1 & _m o!r ev]gre5 trees1 gradually took on a m mod]n aspect1 s t late 9 ! ,mesozoic era !y 7 mu* l ^? n[ liv+4 ,among ! mo/ int]e/+ trees 7 ! sequoias1 to :i* ! liv+ big trees & r$-woods ( ,cali=nia belong4 ,^! began 9 relatively late ,mesozoic "t1 rea*$ _! climax 9 numb]s1 v>iety ( species1 & widespread di/ribution 9 ! e>ly ,c5ozoic era2 & are n[ almo/ ext9ct1 be+ repres5t$ by only two species 9 local portions ( ,cali=nia4 ,cordaites1 trees :i* 7 s l>ge & abundant 9 lat] ,paleozoic "t1 7 r$uc$ to ext9ction 9 ! e>ly ,mesozoic era4 ,dur+ ,mesozoic "t ! ,?allophytes1 repres5t$ by seawe$s1 7 common4 ,among ! ,pt]idophytes ! f]ns & horsetail plants 7 fairly common1 b ! v l>ge =ms gradually gave way to mu* small] ones dur+ ,mesozoic "t4 ,! giant ,lycopods ( lat] ,paleozoic "t dw9dl$ almo/ to ext9ction ev5 9 e>ly ,mesozoic "t1 s t f t "t to ! pres5t !y h be5 v small & relatively insignificant4 ,t5s ( millions ( ye>s ( e>? hi/ory _h pass$ be=e ! true fl[]+ plants--! ,angiosp]ms--appe>$ ^u ! e>?4 ,! ,cretace\s p]iod m>ks _! adv5t4 ,s f> z kn[n1 ^! plants orig9at$ along ! ea/]n side ( ,nor? ,am]ica1 & v soon aft] _! e/abli%m5t !y spread ov] ! e>? ) amaz+ rapidity & dom9at$ ! vegetation z !y d to-day1 m ?an half ( ! exi/+ species ( plants be+ ,angiosp]ms4 ,among ! common types :i* h be5 une>!d f ,cretace\s /rata are palms1 grasses1 maples1 oaks1 elms1 figs1 magnolias1 will[s1 bee*es1 *e/nuts1 & popl>s4 ,illu/ration3 ,plate #ac4--;,a ,slab ( ,v ,e>ly ,paleozoic 7,cambrian7 ,rock1 ,cov]$ ) ,"s ( ! ,olde/ ,kn[n ,def9itely ,det]m9able ,animal ,rema9s4 ,^! creatures liv$ 9 a sea :i* ov]spread ! site ( ! ,rocky ,m\nta9s ( s\!rn ,canada fully #be1jjj1jjj ye>s ago4 ,mo/ ( ! fossils are trilobites 7includ+ "s v small ones7 & o!r relat$ cru/acean =ms 7light] portions74 7,aft] ,c4 ,d4 ,wolcott1 ,smi?sonian ,in/itution1 ,wa%+ton1 ,d4 ,c47 ,illu/ration3 ,plate #ad4--7;a7 ,photographs ( ,small ,slabs ( ,ordovician ,/rata ,full ( ,fossils4 ,^! slabs are actual bits ( sea bottom at lea/ #bj1jjj1jjj ye>s old4 ,! left picture %[s /one-lily /ems1 s-call$ sea mosses1 bra*iopods4 ,"r picture %[s v>i\s species ( bra*iopods4 7,photo by ! au?or47 ,illu/ration3 ,plate #ad4--7;b7 ,an ,outcrop ( ,middle ,ordovician ,/ratifi$ ,lime/one 9 ,nor!rn ,new ,york4 ,?is l$ge is full ( fossils simil> to ^? above4 ,! mat]ial 0 deposit$ on ! floor ( ! ,ordovician sea :i* ov]spread mu* ( ! cont95t4 7,photo by ! au?or47 ,! introduction ( ! high] fl[]+ plants 7,angiosp]ms7 01 p]haps1 ! mo/ important & f>-rea*+ ev5t 9 ! :ole hi/ory ( vegetation1 n only because !y almo/ imm$iately became dom9ant1 b also because ( _! influ5ce ^u ! animal life ( ! succe$+ p]iods4 ,h>dly _h fl[]s appe>$1 be=e a great horde ( insects1 :i* f$ ^u _! honey or poll51 seem to h sprung into exi/5ce4 ,! nutriti\s grasses & ! v>i\s nuts1 se$s1 & fruits af=d$ a bett] food = nonc>nivores ?an ev] be=e 9 ! hi/ory ( ! _w4 ,x 0 to be expect$1 !re=e1 t "s new type ( animal life w\ld be develop$ to take advantage ( ?is sup]ior food supply4 ,z we %all see 9 ! discussion ( ! ,t]ti>y 7next *apt]71 ! mammals1 :i* kept a subord9ate position ?r\gh\t ! ,mesozoic1 rapidly took on bulk & v>iety & acquir$ possession ( ! e>? z soon z !y became adapt$ to ?is new food1 quickly supplant+ ! great reptiles ( ! ,mesozoic4 7,clel&47 ,dur+ ! pres5t or ,c5ozoic era vegetation gradually took on a m & m mod]n aspect until ! exi/+ species 7 develop$4 ,! grasses especially develop$ & spread rapidly1 b ! c]eals did n evolve until late 9 ! era4 ,c]ta9 s+le-cell$ plants1 call$ diatoms1 may be especially m5tion$1 = !y mu/ h lit]ally sw>m$ 9 "s ( ! ,t]ti>y seas :i* spread ov] p>ts ( ! pres5t l&s4 ,! microscopic plants :i* =m silice\s %ells1 call$ diatoms1 make ext5sive deposits 9 "s places4 ,"o /ratum ne> ,ri*mond1 ,virg9ia1 is ?irty feet ?ick & is _m miles 9 ext5t2 ano!r1 ne> ,mont]ey1 ,cali=nia1 is fifty feet ?ick1 & ! mat]ial is z :ite & f9e z *alk1 :i* x resembles 9 appe>ance2 ano!r1 ne> ,bil91 9 ,bohemia1 is f\rte5 feet ?ick4444 ,ehr5b]g has calculat$ t a cubic in* ( ! f9e1 e>?y rock conta9s ab\t =ty-"o ?\s& millions ( organisms4 ,su* accumulations ( diatoms are made bo? 9 fre% wat]s & salt1 & 9 ^? ( ! ocean at all dep?s4 7,j4 ,d4 ,dana47 ,,*apt] ,,xviii ,,geological ,,hi/ory ,,( ,,animals 7,,exclud+ ,,v]tebrates7 ,a /udy ( ! animals ( ! pa/ is n only ( great int]e/ 9 itself1 b also x furni%es a ma9/ay ( ! great doctr9e ( organic evolution4 ,at ! v outset ( our discussion ! read] %\ld h already 9 m9d at lea/ ! ma9 subdivisions ( ! animal k+dom 9 ord] to reasonably well und]/& :]e ! important animal types ( ! diff]5t geological ages fit 91 & h[ ^? types be> ^u ! doctr9e ( evolution4 ,! accompany+1 v brief1 g5]al classification includes ! usually recogniz$ subk+doms ) special ref]5ce to repres5tatives ( ^? :i* are ( mo/ geological & evolution>y significance4 ,read+ d[nw>d 9 ?is classification1 ! degree ( complexity ( organization /eadily increases f s+le-cell$ animals to man himself4 ,i4 ,protozoans1 e4g4 =am9if]s 7) lime c>bonate %ells7 ,sponges ,,ii4 ,coel5t]ates1 e4g4 ,s-call$ jellyfi%es1 graptolites ,corals ,s-call$ sea lilies ,,iii4 ,e*9od]ms1 e4g4 ,s-call$ />fi%es ,s-call$ sea ur*9s ,,iv4 ,worms1 ,v4 ,molluscoids1 e4g4 ,s-call$ sea mosses ,bra*iopods ,clams1 oy/]s ,snails ,pe>ly nautilus1 ,,vi4 ,mollusks1 e4g4 ammonites ,cephalopods1 e4g4 ,s-call$ cuttle fi%es ,trilobites ,,vii4 ,ar?ropods1 e4g4 ,crabs1 lob/]s ,s-call$ sea scorpions ,insects ,o/racod]ms ,fi%es ,,viii4 ,v]tebrates1 e4g4 ,amphibians ,reptiles ,birds ,mammals 7includ+ man7 ,be=e ent]+ into a brief b r sy/ematic discussion ( "s ( ! mo/ important types ( animals :i* liv$ dur+ geological "t1 x may be well = ! read] to h 9 m9d "s ( ! mo/ important conclusions :i* h be5 rea*$ z a result ( ! /udy ( ! fossil animal records4 ,^! conclusions may be summ>iz$ z foll[s3 #a4 ,animal life exi/$ _m millions ( ye>s ago4 #b4 ,n only ! animals ( to-day1 b also ^? ( any giv5 geological p]iod1 directly desc5d$ f ^? ( prec$+ geological p]iods4 #c4 ,animal life has und]gone cont9u\s *ange s9ce its introduction ^u ! e>?1 s t ea* gr\p ( /rata1 repres5t+ a p>ticul> geological age1 conta9s a *>act]i/ic assemblage ( fossil animals4 #d4 ,_m ( ! *anges 9 ! hi/ory ( animals h be5 progressive or evolution>y1 s t /rata ( e>ly geological "t conta9 di/9ctly m primitive or l[] ord] =ms ?an ! /rata ( late geological "t4 ,b1 :ile ! l9e ( evolution has be5 ma9ta9$ )\t a break1 culm9at+ 9 man1 !re h be5 _m (f%oots ( a retrogressive nature4 #e4 ,ev5 z f> along 9 geological "t z ! e>ly ,paleozoic era1 ! highe/ subk+dom--v]tebrates--_h no repres5tative :atev]4 ,9 o!r words1 all ! important subdivisions ( animal life f a little bel[ fi%es to man h be5 evolv$ s9ce ab\t ! close ( ! ,ordovician p]iod4 #f4 ,any species ( animal :i* ev] became ext9ct has nev] be5 kn[n to reappe>1 & lit]ally t5s ( ?\s&s ( species are kn[n to h become ext9ct4 #g4 ,no species l ^? n[ liv+ are f\nd 9 ! m anci5t /rata1 su* be+ conf9$ to ! /rata ( relatively rec5t geological dates4 #h4 ,:ile m & m highly organiz$ animals h cont9u\sly be5 evolv$1 _m ( ! e>li] & simpl] types h p]si/$1 a rem>kable case 9 po9t be+ ! s+le-cell$ animals call$ =am9if]s :i* may be trac$1 )\t v notable *ange1 ?r\gh ! t5s ( millions ( ye>s ( geological "t f ! late ,prot]ozoic era to ! pres5t day4 #i4 ,_m species h be5 able to ma9ta9 !mselves practically )\t *ange ?r\gh long /ret*es ( geological "t1 :ile o!rs h _h only v brief exi/5ce4 ,:5 did animal life beg9 on ! e>?1 & :at 7 ! fir/ =ms l8 ,we c only p>tially answ] ! fir/ "q by say+ t animals h exi/$ = t5s ( millions ( ye>s1 c]ta9ly z e>ly at lea/ z ,prot]ozoic "t4 ,up to ! pres5t "t we are utt]ly 9 ! d>k z to :at ! e>lie/ animal =ms look$ l1 b we h positive k t ! olde/ =ms f\nd z fossils 9 ! rocks repres5t creatures :i* 7 f> m primitive & l[] 9 organization ?an _m animals ( to-day1 & t s9ce ^? olde/ kn[n =ms liv$1 ! animal k+dom has und]gone v>i\s pr(\nd alt]ations4 ,9 view ( ! above /atem5ts1 & also ! fact t ! olde/ kn[n plant =ms 7 extremely simple or s+le-cell$1 x is m ?an likely t ! fir/ animal life ( ! e>? 0 s+le-cell$4 ,9 h>mony ) ?is view is ! fact t fossil s+le-cell$ animals are f\nd 9 ! v olde/ 7,prot]ozoic7 rocks :i* conta9 any def9itely det]m9able fossil animals4 ,d ! mo/ anci5t kn[n rocks %[ t animal life exi/$ dur+ ,ar*eozoic "t8 ,9 ! prec$+ *apt] we po9t$ out ! fact t ! c>bon 79 ! =m ( graphite71 s commonly pres5t 9 ^? mo/ anci5t kn[n /rata1 proves ! exi/5ce ( life ( "s k9d dur+ ,ar*eozoic "t4 ,b because no?+ l def9itely det]m9able fossil =ms h ?us f> be5 discov]$ 9 ^? rocks1 we _c be sure :e!r ! c>bon repres5ts plant or animal life or bo?1 ?\gh c]ta9ly plants ( v l[ ord] at lea/ mu/ h exi/$4 ,because ( ! int5se alt]ation 7metamorphism7 ( ^? v old /rata1 all def9ite =ms h long s9ce be5 oblit]at$ z su*4 ,we may1 h[ev]1 9 ! light ( ! va/ evolution :i* took place ?r\gh succe$+ geological "t1 be v sure t any animals :i* may h exi/$ dur+ ,ar*eozoic "t 7 9 g5]al mu* simpl] =ms ?an ^? ( ev5 e>ly ,paleozoic "t4 ,! e>ly & middle ,prot]ozoic /rata ?r[ no m light ^u ! e>ly hi/ory ( animal life ?an d ! ,ar*eozoic /rata4 ,! upp] or lat] ,prot]ozoic rocks1 h[ev]1 conta9 ! olde/ recognizable animal fossils4 ,v rec5tly fossil rema9s ( s+le-cell$1 %ell-be>+ ,protozoans h be5 f\nd 9 nor!rn ,france1 :ile ! upp] ,prot]ozoic /rata ( ! ,rocky ,m\nta9s 9 ,montana1 & ! ,gr& ,canyon ( ,arizona h yield$ worm tracks1 a ,molluscoid 7bra*iopod7 & fragm5ts ( l[] =ms ( ,ar?ropods4 ,?is record1 al?\gh v meag]1 cle>ly proves t animal life 0 s well advanc$ by late ,prot]ozoic "t1 t next to ! highe/ subk+dom 0 actually repres5t$ 7see above classification71 & t !re mu/ h be5 a long l9e ( simpl] & simpl] ance/ors1 probably ext5d+ f> back into ! ,ar*eozoic era4 ,:5 we /op to consid] t ,ar*eozoic & ,prot]ozoic "t 0 fully z long z all succe$+ geological "t1 x is n s surpris+ t fairly highly develop$ animals 7except ,v]tebrates7 _h be5 evolv$ be=e ! close ( ! ,prot]ozoic era4 ,9 reg>d to abundance ( fossil animals ! olde/ 7,cambrian7 ,paleozoic /rata /& out 9 m>k$ contra/ to ! ,prot]ozoic4 ,_m hundr$s ( species ( animal fossils h be5 describ$ f ,cambrian /rata1 & a great _m o!rs yet rema9 to be discov]$4 ,cambrian fossils are rem>kably num]\s1 v>i$ 9 species1 & complex 9 organization 7,plate #ac74 ,all subk+doms ( animals except ! ,v]tebrates 7 repres5t$1 ?\gh usually only by ! simpl] types 9 ea* subk+dom4 ,x is q g5]ally agre$ t no less ?an #ej p] c5t ( animal evolution _h tak5 place be=e ! beg9n+ ( ! ,cambrian p]iod4 ,! read] %\ld1 h[ev]1 cle>ly be> 9 m9d t trem5d\s advances 9 evolution h tak5 place s9ce e>ly ,cambrian "t :5 n only all =ms f l[] scale ,ar?ropods to ! highe/ mammals 7includ+ man7 h evolv$1 b also :5 _m ?\s&s ( species ( l[] subk+dom animals develop$4 ,:y are ! v e>ly ,paleozoic /rata s ri* 9 fossils1 :ile ! imm$iately prec$+ ,prot]ozoic rocks %[ s few8 ,! seem+ly sudd5 appe>ance ( s _m highly develop$ animals 9 e>lie/ ,paleozoic 7,cambrian7 "t is "o ( ! mo/ important consid]ations 9 ! hi/ory ( animal life1 & x is by no means def9itely und]/ood4 ,! foll[+ /atem5ts be> directly ^u ! problem3 ,! e>ly animal =ms 7 probably s(t or gelat9\s )\t %ells & liv$ mo/ly 9 ! op5 sea :]e food 7seawe$s1 etc47 0 abundant4 ,su* animals 7 v unfavorable = pres]vation 9 fossil =m4 ,!n1 late 9 ,prot]ozoic "t or v e>ly 9 ! ,paleozoic1 a sev]e /ruggle = exi/5ce set 91 probably due to cr[d+ along %ores1 & h>d p>ts began to develop bo? = support & def5sive purposes4 ,su* h>d p>ts or %ells 7 commonly favorable = fossilization4 ,?is view is /rongly support$ by ! fact t v ?9 %ells only are kn[n f late ,prot]ozoic rocks1 & mo/ly v ?9 %ells f ! e>lie/ ,cambrian1 ! heavi] %ells hav+ be5 evolv$ lat]4 ,a fact ( importance to be> 9 m9d 9 ?is connection is t j at ! critical "t 7late ,prot]ozoic7 9 %ell developm5t1 ! l&s ( ! e>? 7 und]go+ widespread & deep erosion z po9t$ out e>ly 9 ! *apt] on ,anci5t ,e>? ,hi/ory4 ,! e>lie/ ,cambrian /rata1 !re=e1 ne>ly ev]y:]e re/ ^u ! deeply erod$ surface ( ! ,prot]ozoic rocks s t ! transition /rata--! v ones :i* w\ld conta9 mo/ fossils ( ! e>ly %ell developm5t /age--are ne>ly ev]y:]e miss+4 ,f9ally1 m5tion %\ld be made ( ! fact1 t all ,ar*eozoic /rata are pr(\ndly alt]$ 7metamorphos$71 & s are ne>ly all ,prot]ozoic /rata1 except ! lat]4 ,fossils once pres5t 9 ^? rocks w\ld ( c\rse h be5 oblit]at$ by ! process ( metamorphism1 b ! fact rema9s t v consid]able ?icknesses ( practically unalt]$ ,prot]ozoic /rata %[ few if any animal fossils4 ,we %all n[ proce$ to a r sy/ematic consid]ation ( ! mo/ int]e/+ & significant types ( creatures :i* h inhabit$ ! e>? s9ce ! beg9n+ ( ,paleozoic "t at lea/ tw5ty-five million ye>s ago4 ,x is our purpose to br+ out ! sali5t features 9 ! hi/ory ( ea* subk+dom ( animals1 beg9n+ ) ! l[e/ or simple/1 & tak+ up 9 turn ! high] & high] subk+doms4 ,by ?is me?od ! read] may easily foll[ ! ma9 ?read ( organic evolution or progressive *ange :i* runs ?r\gh mo/ ( ! kn[n hi/ory ( animal life ( our planet1 & :i* is s important 9 ! sci5ce ( geology4 ,protozoans1 :i* include all ! t9y s+le-cell$ animals1 are kn[n 9 fossil =m ev5 9 late ,prot]ozoic rocks &1 z prov$ by ! fossil records1 !y h be5 m or less abundant ev] s9ce1 ev5 n[ sw>m+ 9 l>ge portions ( ! surface sea wat]s4 ,"o ( ! mo/ rem>kable facts 9 ! hi/ory ( animal life is1 t su* exce$+ly simple creatures p]si/$ almo/ )\t *ange ?r\gh ! t5s ( millions ( ye>s :5 su* pr(\nd & ev5 revolution>y *anges took place 9 ! animal k+dom 9 g5]al4 ,! only fossil ,protozoans are ^? :i* develop$ delicate %ells ei!r ( c>bonate ( lime 7! =am9if]s7 or silica4 ,special m5tion %\ld be made ( ! ,cretace\s p]iod :5 =am9if]s mu/ h be5 exce$+ly pr(use 9 cle> sea wat]s :i* spread ov] ! ,gulf ,coa/al ,pla9 ( ! ,unit$ ,/ates1 p>ts ( s\!rn ,engl&1 mu* ( ,france1 & o!r areas1 z prov$ by _! accumulat$ %ells :i* make up =mations ( *alk hundr$s ( feet 9 ?ickness & _m miles 9 ext5t4 ,illu/ration3 ,fig4 #di4--;,a comp\nd colony ( fossil graptolites *>act]i/ic ( late ,ordovician "t1 fully #bj1jjj1jjj ye>s ago4 ,ea* little prong once held a t9y individual liv+ graptolite :i* 0 a v simple type ( animal belong+ to ! subk+dom call$ ,coel5t]ates4 7,modifi$ aft] ,ru$emann47 ,! ,coel5t]ates1 :i* comprise ! simple/ ( ! _m-cell$ animals1 are saclike =ms ) m\? op5+s1 b ) few o!r diff]5tiations ( p>ts4 ,all are m>9e animals4 ,( ^! ! sponges are por\s1 & ! o!r types 7includ+ corals7 h t5tacles ar\nd _! m\?s4 ,sponges h be5 m or less common f e>ly ,paleozoic "t to ! pres5t1 & !y h und]gone relatively little *ange4 ,jellyfi%es1 :i* are 9 tru? n fi%es at all1 are :olly s(t or gelat9\s ,coel5t]ates :i* h left "s v rem>kable impressions & ca/s 9 /rata ( v e>ly ,paleozoic age1 ^? v anci5t =ms evid5tly hav+ be5 almo/ exactly l ^? ( to-day4 ,graptolites 7 sl5d]1 plumelike1 delicate =ms consi/+ ( colonies ( t9y individuals1 9 _m cases 9 bran*+ or radiat+ comb9ations4 ,!y exi/$ only dur+ ! fir/ half ( ! ,paleozoic era4 ,bo? because !y float$ 9 ! op5 sea1 ?us p]mitt+ widespread di/ribution1 & because !y und]w5t _m di/9ct species *anges dur+ %ort geologic int]vals1 !y are among ! mo/ useful fossils = sep>at+ ! v>i\s subdivisions ( /rata ( ! e>li] ,paleozoic4 ,illu/ration3 ,fig4 #ej4--;,corals1 repres5t+ ! v simple subk+dom ( animals call$ ,coel5t]ates3 a1 fossil %ell ( an individual cup coral f\nd only 9 ,paleozoic /rata2 b1 a comp\nd or *a9 coral skeleton f\nd only 9 relatively old ,paleozoic /rata2 & c1 "p ( a mod]n coral colony %[+ liv+ corals4 ,corals comprise ano!r important bran* ( ! ,coel5t]ates4 ,dur+ ! ,cambrian p]iod !re 7 corallike sponges & possibly simple corals1 b f ! e>ly ,ordovician to ! pres5t true corals h be5 common1 especially 9 ! cle>]1 w>m] seas4 ,_! c>bonate ( lime skeletons h accumulat$ to help build up great lime/one =mations repres5t+ almo/ e geologic age f e>ly ,paleozoic "t to ! pres5t4 ,paleozoic corals 7 9 g5]al notably diff]5t f ^? ( lat] "t4 ,!re 7 ?ree ma9 types includ+ ! comp\nd honeycomb & *a9 types1 & ! solit>y or comp\nd cup type4 ,!y all _h f\r1 or multiples ( f\r1 radiat+ p>titions2 7 r>ely bran*$2 & 7 g5]ally l>ge1 "s individual cup corals rang+ 9 l5g? f half an in* to a foot or m4 ,mod]n corals 7beg9n+ ) ! ,mesozoic7 h six or eight p>titions2 are ne>ly all pr(usely bran*$2 & are mo/ly t9y individuals4 ,e*9od]ms are all m>9e animals1 includ+ ! s-call$ />fi%es1 :i* are n really fi%es4 ,!y h body cavity1 ) dige/ive canal1 l[ ord] n]v\s sy/em1 & a wat] circulatory sy/em4 ,mo/ ( !m h radially segm5t$ %ells or skeletons4 ,! olde/ fossil =ms are f\nd 9 ,cambrian /rata1 ^! be+ v simple or primitive types1 ) a bladd]like head set on ! end ( a segm5t$ /em1 bo? head & /em hav+ be5 support$ by c>bonate ( lime4 ,su* =ms liv$ only to middle ,paleozoic "t4 ,ordovician /rata conta9 repres5tatives ( all ! ma9 types ( ,e*9od]ms 9 well-fossiliz$ =ms4 ,illu/ration3 ,fig4 #ea4--;,fossil ,e*9od]ms or s-call$ />fi%es3 a1 simple type kn[n z ! /one lily ) head1 /em1 & roots intact f ,silurian /rata2 b & c1 irregul> & regul> high] type ,e*9od]ms call$ sea ur*9s f ,cretace\s /rata4 ,a /emm$ ,e*9od]m ( special int]e/1 fir/ kn[n f ! ,ordovician1 has p]si/$ to ! pres5t day4 ,x is ! s-call$ sea lily or /one lily1 consi/+ ( a complex1 headlike portion atta*$ to ! sea bottom by a long segm5t$ /em1 ! :ole be+ support$ by lime c>bonate4 ,!y 7 v num]\s dur+ ! ,silurian1 b !y seem to h culm9at$ 9 v>iety ( species & numb]s ( individuals dur+ ! ,mississippian p]iod :5 !y 7 exce$+ly pr(use4 ,hundr$s ( species ( /one lilies are kn[n f ,mississippian /rata alone1 & 9 c]ta9 localities1 z at ,craw=dsville1 ,ind41 & ,burl+ton1 ,ia41 ! /one lily rema9s are s num]\s t :5 liv+ !y mu/ h lit]ally =e/$ p>ts ( ! sea bottom4 ,f ,mississippian "t to middle ,mesozoic "t !y occupi$ a relatively subord9ate position :5 !y aga9 develop$ 9 great pr(usion4 ,! ,mesozoic =ms 7 di/9ctly m l ^? ( to-day1 & x sc>cely seems cr$ible t any creature c\ld h conta9$ su* a multiplicity ( h>d p>ts1 m ?an #fjj1jjj segm5ts hav+ be5 c\nt$ 9 a s+le fossil f ,jurassic /rata4 ,! sea lilies ( to-day are relatively unimportant4 ,! famili> five-po9t$ />fi%es1 s common along our seacoa/s1 are fir/ kn[n f ! ,ordovician1 & !y p]si/$ ?r\gh ! _m millions ( ye>s to ! pres5t "t ) rem>kably little *ange4 ,! s-call$ sea ur*9s live 9 r\nd$1 segm5t$ lime-c>bonate %ells bri/l+ ) movable sp9es4 ,sea ur*9s are fir/ kn[n f ! ,ordovician1 b !y did n become abundant & div]sifi$ until ,mesozoic "t1 :5 _m ( !m took on a v mod]n aspect4 ,worms are kn[n to h exi/$ ev] s9ce late ,prot]ozoic "t1 z prov$ by ! occurr5ce ( tracks1 bor+s & m r>ely delicate impressions on rock surfaces4 ,because ( _! s(tness !y h r>ely be5 well fossiliz$ & are1 !re=e1 ( no great evolution>y or geological importance4 ,illu/ration3 ,fig4 #eb4--;,fossil bra*iopods belong+ to ! subk+dom ( animals kn[n z ,molluscoids3 a1 b1 c1 =ms *>act]i/ic ( ! ,ordovician1 ,devonian1 & ,triassic p]iods1 respectively4 ,! subk+dom ,molluscoids has be5 ri*ly repres5t$ by bo? ! s-call$ sea mosses & bra*iopods4 ,! sea mosses =m colonies ( t9y mosslike tufts1 resembl+ corals outw>dly1 ?\gh !y are mu* m highly organiz$4 ,!y h be5 common f ,ordovician "t to ! pres5t1 _! c>bonate ( lime skeletons (t5 hav+ contribut$ to ! build+ ( lime/one =mations4 ,bra*iopods always h two ext]nal %ells or valves1 9 mo/ cases work+ on a h+e1 & also a pair ( long1 spiral-fr+$ arms associat$ ) ! s(t "p ( ! animal inside ! %ells4 ,!y diff] f ! o!r type ( bivalve 7e4g41 clam1 oy/]7 9 t !y are symmetrical ) ref]5ce to a plane pass$ ?r\gh ! middle ( ! %ells at "r angles to ! h+e l9e4 ,!y h r>ely gr[n to be m ?an a few in*es long4 ,a few scant bra*iopod rema9s are kn[n f ! late ,prot]ozoic1 b ?r\gh\t kn[n geologic "t !y rea*$ _! greate/ developm5t 9 ! ,paleozoic era1 m especially 9 ! ,devonian p]iod4 ,comb9+ numb] ( species & numb] ( individuals1 ! bra*iopods probably hold ! record ( all important gr\ps ( fossil animals1 m ?an #g1jjj species be+ kn[n4 ,_m lay]s ( rock are fill$ ) _! %ells 7,plate #ad74 ,s9ce ! close ( ! ,paleozoic !y h fall5 (f notably1 & are n[ repres5t$ by relatively few small =ms4 ,f ! /&po9t ( evolution x is int]e/+ to note t 9 v e>ly ,paleozoic "t ! bra*iopods 7 mo/ly small1 ( relatively simple organization1 & _! ?9 %ells 7 n jo9$ by h+es4 ,lat] !y became l>g] & m complex & _! ?ick] %ells work$ on h+es4 ,ne>ly all ! ,paleozoic =ms _h long1 /raight h+e l9es1 :i* made x difficult = _! enemies to op5 !m4 ,along ) ! *ange to n>r[]1 curv$ h+e l9es came ! decl9e ( ! tribe4 ,!y h be5 ( great value to ! geologi/ 9 subdivid+ ! geological column ( /rata into its _m =mations4 ,! ,mollusks1 :i* are m highly organiz$ ?an ! ,molluscoids1 h m or less di/9ctly develop$ heads & locomotive organs4 ,_m ?\s&s ( species are n[ ext9ct1 ! classes ( mo/ geological importance be+ repres5t$ by clams1 snails1 & ! pe>ly nautilus4 ,mo/ ( !m h %ells & gills = brea?+4 ,! memb]s ( ! simple/ gr\p1 well repres5t$ by ! clam tribe1 possess two simil> %ells work+ on h+es1 s t 9 ?is reg>d !y are mu* l bra*iopods1 b1 unlike ! latt]1 !y are n symmetrical ) ref]5ce to a plane at "r angles to ! h+e l9e4 ,cambrian /rata conta9 ! olde/ kn[n ( ! fossil =ms :]e !y are small1 relatively ?9-%ell$1 & r>e4 ,9 m>k$ contra/ to ! bra*iopods ^! bivalves h r /eadily increas$ 9 numb]s ( species & individuals to ! pres5t "t1 n[ be+ repres5t$ by ?\s&s ( =ms4 ,dur+ ! ,mesozoic era !y greatly out-numb]$ ! bra*iopod bivalves & took on a m di/9ctly mod]n aspect1 :5 ! oy/] tribe & closely relat$ types 7 prom95tly develop$4 ,culm9ation 9 size & ?ickness ( %ell seem to h be5 rea*$ 9 e>ly ,c5ozoic "t1 /rata ( t age 9 c]ta9 places1 = example 9 ,georgia & s\!rn ,cali=nia1 be+ fill$ ) oy/] %ells #aj to #bj in*es long & #d to #f in*es ?ick6 ,9 addition to _! gigantic size & ?ickness1 _m ( ! %ells 7 flut$ or ribb$1 & s !y repres5t$ an extreme type ( def5sive armor among ! l[] animals4 ,snails h exi/$ f ! e>lie/ ,paleozoic era to ! pres5t "t1 & ! out/&+ fact ( int]e/ conc]n+ !m is t !y furni% "o ( ! f9e/ illu/rations ( an important class ( animals :i* has und]gone practically no conspicu\s *ange or evolution dur+ all ^? millions ( ye>s ( "t4 ,illu/ration3 ,fig4 #ec4--,sket*es ( *amb]$ cephalopods %[+ ! ma9 /eps 9 ! evolution ( ! %ell =ms & comp>tm5t p>titions3 a1 b1 ! only k9ds 9 ,cambrian "t2 c1 d1 =ms add$ 9 ! ,ordovician2 e1 add$ 9 ! ,devonian2 f1 add$ 9 ! late ,paleozoic2 g1 h1 *>act]i/ic ( ! ,mesozoic era2 & i1 a liv+ =m 7pe>ly nautilus7 cut ?r\gh4 7,drawn by ! au?or47 ,we %all n[ turn our att5tion to ! highe/ ord] ( ,mollusks--! cephalopods4 ,^! creatures1 ^: heads are arm$ ) p[]ful t5tacles & suppli$ ) complex eyes1 propel !mselves by =cible ejection ( wat]4 ,"o g5]al type--! *amb]$ cephalopod--has a %ell divid$ into comp>tm5ts 7e4g41 mod]n pe>ly nautilus7 :i* are successively built up & ab&on$ by ! animal z x gr[s l>g]4 ,^! *amb]-%ell$ cephalopods con/itute "o ( ! mo/ rem>kable & in/ructive illu/rations ( evolution>y *ange )9 any important subgr\p ( inv]tebrate animals1 rang+ f e>ly ,paleozoic to ! pres5t4 ,bo? because ( ! abundance ( fossil =ms 9 rocks ( all ^! p]iods ( geological times1 & because c]ta9 ( ! evolution>y *anges are s cle>ly express$ 9 ! well pres]v$ %ell portions1 !y are specially adapt$ = /udy4 ,9 ! late ,cambrian only /raight & slightly curv$ =ms ) smoo?1 ne>ly /raight *amb] p>titions exi/$4 ,notable advance took place dur+ ! next 7,ordovician7 p]iod :5 !re 7 /raight1 curv$1 op5-coil$1 & ev5 close-coil$ =ms4 ,all _h simple p>titions1 & ! /raight] =ms pr$om9at$4 ,! size atta9$ by ! ,ordovician cephalopods 0 probably nev] surpass$ by repres5tatives ( ! class4 ,"s ( ! 7/raight7 %ells 7 twelve to fifte5 feet 9 l5g?1 & a foot 9 diamet]4 ,f ?is great size !y rang$ d[n to or bel[ ! size ( a pipe /em4 7,*amb]l9 & ,salisbury47 ,!y 7 m ?an likely ! undisput$ ma/]s ( ! ,ordovician seas4 ,silurian "t m>k$ no important *ange 9 _! /ructures1 b ! coil$ =ms pr$om9at$ = ! fir/ "t4 ,dur+ ! second half ( ! ,paleozoic era all prec$+ types ) simple p>titions p]si/$1 b 9 "s =ms ! simple p>titions gradually became angl$ & f9ally r complexly curv$4 ,dur+ ! ,mesozoic era ! p>tition l9es ( ! close-coil$ =ms evolv$ until a mo/ rem>kable degree ( complexity 0 atta9$1 comp>able1 inde$1 to ! sutures ( ! human skull plates4 ,^! rem>kable =ms call$ ammonites1 ( :i* m ?an #b1jjj species are kn[n1 began ) ! ,mesozoic1 rea*$ _! climax1 & pass$ out ( exi/5ce t[>d ! close ( ! same era4 ,c]ta9 /rata ( ,jurassic age are lit]ally fill$ ) ammonites1 "s %ells be+ sev]al feet 9 diamet]4 ,v>i\s ecc5tric *anges took place 9 ! ammonites %ortly be=e _! ext9ction4 ,"s %ells became uncoil$ & ev5 /raight1 ?us outw>dly at lea/ %[+ rev]sion to ! orig9al e>ly ,paleozoic ance/ors1 b ) ret5tion ( ! complex p>titions4 ,o!rs assum$ spiral %apes & /ill o!rs became curv$ or coil$ at ea* end4 ,:ile ^! extraord9>y evolution>y *anges 7 go+ on among ! *amb]s ( cephalopods dur+ ,mesozoic "t1 "s ( ! anci5t close-coil$ =ms ) v simple p>titions manag$ to p]si/4 ,9 fact ?is simple type1 almo/ exactly l its e>ly ,paleozoic ance/or1 has be5 ! only "o out ( ?is :ole rem>kable class ( animals to p]si/ to ! pres5t "t1 be+ n[ b>ely repres5t$ by ! well-kn[n pe>ly nautilus ( ! ,indian ,ocean4 ,dur+ ! ,mesozoic era ! highe/ type ( cephalopod1 repres5t$ by mod]n squids & s-call$ cuttlefi%es1 bran*$ (f & develop$ 9 great pr(usion4 ,^! _h sl5d] int]nal %ells1 b no ext]nal *amb]$ %ells4 ,an inky black liquid secret$ 9 a bag 0 =c$ out to cl\d ! wat] :5 ! animal 0 escap+ its enemy1 ?us ant$at+ by millions ( ye>s ! pr9ciple ( smoke scre5 s effectively us$ by %ips dur+ ! ,_w ,w>4 ,"s ,jurassic species got to be ov] two feet long1 & a few specim5s ( t age h be5 f\nd 9 su* p]fect /ate ( pres]vation t draw+s ( ! fossils h actually be5 made ) ! ink 7aft] moi/5+7 tak5 f _! own ink bags4 ,illu/ration3 ,fig4 #ed4--;,a fossil non*amb]$ cephalopod ( ,jurassic age4 ,x 0 closely relat$ to ! mod]n squid1 & its ink bag is well %[n j to ! left ( ! middle4 7,modifi$ aft] ,mantell47 ,be=e conclud+ ?is *apt] we %all take up ! sali5t po9ts 9 ! geological hi/ory ( ,ar?ropods :i* con/itute ! highe/ subk+dom ( all animals except ! ,v]tebrates4 ,!y are n[ v abundant & v>i$1 famili> examples be+ crabs & insects4 ,a few scant rema9s ( simpl] =ms are kn[n f ! ,prot]ozoic1 b s9ce v e>ly ,paleozoic "t !y h be5 v common & h und]gone great evolution>y *anges4 ,a few /rik+ examples only w be dwelt ^u4 ,among ! mo/ common & int]e/+ ( all ,paleozoic animals 7 ! trilobites1 di/antly relat$ to mod]n lob/]s & crabs4 ,illu/ration3 ,fig4 #ee4--,re/orations ( trilobites bas$ ^u actual fossils *>act]i/ic ( e>li] ,paleozoic "t3 a1 ,cambrian2 b1 ,ordovician2 c1 ,devonian2 b %[s ! app5dages4 ,"s ( ^! grew to be two feet long1 b usually !y 7 only "o or two in*es long4 ,fir/ kn[n f ! e>lie/ ,paleozoic1 !y rea*$ _! culm9ation relatively e>ly 9 ! era & !n dw9dl$ away to utt] ext9ction be=e its close4 ,!y 7 *>act]i/ic ( ! ,paleozoic era1 beg9n+ 9 great v>iety 9 ! ,l[] ,cambrian & dom9at+ ! seas ( ! ,cambrian 7#cjj species7 & ,ordovician 7#iej species74 ,9 ! ,silurian1 ?\gh !y 7 /ill common1 ! trilobites 7 nev]!less on ! decl9e 7#dhe species71 & ?is ebb+ ( _! vital =ce is seem+ly %[n 9 _m picturesque =ms replete ) protub]ances1 sp9es1 & exagg]ation ( p>ts4 ,z a rule1 9 evolution1 "o f9ds t :5 an organic /ock is los+ its vital =ce !re arises 9 x an exagg]ation ( p>ts1 z if h]oic ef=ts 7 be+ made to ma9ta9 ! race4 ,sp9osity 9 animals is (t5 ! prophecy ( tribal dea?4 ,9 ! ,devonian1 ! v>iety & numb] ( ! trilobites 7 greatly r$uc$ 7#aje species71 at a "t :5 ! anci5t types ( fi%es1 :i* und\bt$ly f$ on ^! cru/aceans 7trilobites71 began to be common 9 ! seas4 ,9 ! lat] ,paleozoic seas1 ! trilobites 7 relics1 or animals surviv+ f a "t bett] suit$ to _! ne$s1 & "o by "o !y vani%$1 until a little be=e ! close ( ! ,paleozoic era none 7 left4 7,s*u*]t47 ,illu/ration3 ,fig4 #ef4--;,a giant1 sea scorpion ( ,devonian "t4 ,l5g? ne>ly #c feet4 7,aft] ,cl>ke & ,ru$emann1 ,new ,york ,/ate ,museum47 ,an extraord9>y type ( ,ar?ropod :i* rang$ ?r\gh\t ,paleozoic "t & became ext9ct at its close 0 ! s-call$ sea scorpion1 closely relat$ to ! mod]n scorpion4 ,_! five or six pairs ( app5dages all came out f ! head portion1 "o pair 9 "s cases hav+ be5 develop$ z p[]ful p9c]s4 ,_! culm9ation 9 size 0 rea*$ dur+ ! ,devonian :5 "s =ms grew to ! a/oni%+ l5g? ( ov] eight feet6 ,su* gigantic creatures mu/ h be5 tyrants ( ! seas until !y 7 subdu$ by ! oncom+ p[]ful fi%es4 ,true scorpions are kn[n f rocks z old z ! ,silurian4 ,lob/]s & crabs made _! appe>ance dur+ ! ,mesozoic era4 ,s9ce insects con/itute ! highe/ subdivision ( ,ar?ropods1 !y include ! v highe/ =ms ( animal life except ! ,v]tebrates4 ,! olde/ kn[n fossil insects are f ,p5nsylvanian /rata1 m ?an #a1jjj species hav+ be5 describ$ f rocks ( t age4 ,!y 7 all simple or primitive types l cockroa*es & dragon flies1 & 7 rem>kable = size4 ,giant cockroa*es got to be f\r in*es long4 ,"o =m ( dragon fly1 ) a spread ( w+ ( ov] two feet1 0 probably ! l>ge/ insect :i* ev] liv$ 7,plate #ae74 ,developm5t ( insect life 0 especially favor$ dur+ ! great ,coal ,age because ( ! prolific vegetation1 b m ?an likely insects orig9at$ some:at e>li]4 ,e>ly 9 ! ,mesozoic era a great progressive *ange began to come ov] insect life & high] =ms gradually evolv$ until by ! close ( ! era _m ( ! highe/ types l flies1 ants1 & bees 7 common4 ,z might be expect$1 ! highe/ insects did n develop until aft] ! appe>ance ( ! true fl[]+ plants 9 lat] ,mesozoic "t1 butt]flies app>5tly n hav+ evolv$ until e>ly 9 ,c5ozoic "t4 ,_m ( ! ?\s&s ( kn[n species ( fossil insects are f /rata ( ,t]ti>y age dur+ :i* "t !y may h be5 ev5 m num]\s ?an to-day1 al?\gh !re are ab\t #djj1jjj species n[ liv+4 ,an almo/ incr$ible case is a ,t]ti>y /ratum only a few feet ?ick 9 ,switz]l& f :i* ne>ly #a1jjj species ( insects h be5 une>!d4 ,ano!r fam\s locality is ,florissant1 ,colorado1 :]e dur+ e>ly ,t]ti>y "t !re 0 a small lake into :i* %[]s ( f9e volcanic du/ fell & entomb$ va/ numb]s ( insects1 m ?an #b1jjj species hav+ be5 une>!d4 ,/ill ano!r extraord9>y occurr5ce is along ! %ores ( ! s\!rn ,baltic ,sea :]e m ?an #b1jjj species ( insects h be5 f\nd 9 a fossil res9 call$ amb]4 ,! insects 7 caught 9 ! /ill s(t /icky res9 :ile x 0 exud+ f ! trees1 & ?us we h ! insects1 fully two or ?ree million ye>s old1 lit]ally embalm$ & m>vel\sly pres]v$1 (t5 9 beautifully transp>5t amb]4 ,,*apt] ,,xix ,,geological ,,hi/ory ,,( ,,v]tebrate ,,animals 7,,includ+ ,,man7 ,v]tebrates comprise ! highe/ subk+dom ( all animals ) man himself at ! v top4 ,!y are *>act]iz$ by ! possession ( a v]tebral column1 :i*1 9 all b ! v simple or primitive =ms1 is an ossifi$ backbone4 ,_! ma9 subdivisions are giv5 9 ! classification table ne> ! beg9n+ ( ! prec$+ *apt]4 ,! olde/ kn[n ,v]tebrates1 f\nd 9 fossil =m 9 middle ,ordovician /rata1 7 repres5t$ by curi\s & biz>re creatures call$ o/racod]ms1 or m popul>ly armor fi%es4 ,!y 7 n true fi%es because !y 7 really some:at l[] 9 ! scale ( organization ?an fi%es4 ,"s 7 di/9ctly fi%like 9 appe>ance1 & o!rs notably resembl$ c]ta9 ( ! ,ar?ropods1 s t "s /ud5ts consid] !m to h =m$ ! connect+ l9k betwe5 ! highe/ ,inv]tebrates 7,ar?ropods7 & l[ ord] fi%es ( ! ,v]tebrates4 ,! v]tebral column always consi/$ ( c>tilage or gri/le &1 9 mo/ =ms1 x ext5d$ ?r\gh tail f94 ,none _h true side f9s l fi%es1 b _m 7 provid$ ) a pair ( jo9t$ flapp]s or paddles4 ,! jawlike portions ( ! heads mov$ ov] ea* o!r sidewise z1 = example1 9 beetles & n up & d[n 9 true ,v]tebrate fa%ion4 ,two eyes 7 always v close toge!r4 ,"o ( ! mo/ /rik+ features 0 ! protection ( ! head & =e "p ( ! body by an armor ( bony plates1 :ile ! re/ ( ! body _h scales4 ,!y seldom grew to be m ?an six or sev5 in*es long4 ,beg9n+ 9 ! ,devonian1 !y rema9$ r>e dur+ ! ,silurian1 & !n 9 ! ,devonian p]iod !y rea*$ _! climax ( developm5t only to become ext9ct at its close4 ,_m species 7 abundantly repres5t$ 9 _m p>ts ( ! _w4 ,by "s ! ,o/racod]ms are ?\ght to h be5 a primitive 7%>klike7 fi% developm5t 9 ! wrong direction1 & h5ce !y became ext9ct4 ,illu/ration3 ,fig4 #eg4--,two re/or$ =ms ( v primitive & anci5t 7,devonian7 types ( ,v]tebrates call$ o/racod]ms4 ,!y 7 l[] 9 organization ?an true fi%es4 7,aft] ,dean-,woodw>d & ,briti% ,museum1 respectively47 ,fi%es1 repres5t$ only by v primitive %>ks1 are kn[n to h exi/$ z e>ly z ! ,silurian p]iod1 b ! rema9s are scant4 ,dur+ ! ,devonian p]iod1 h[ev]1 !y %[$ a m>vel\s developm5t into _m species & c\ntless myriads ( individuals4 ,! ,devonian is1 !re=e1 commonly call$ ! ,age ( ,fi%es4 ,^! v anci5t 7,devonian7 primitive 7fi%7 types ( ,v]tebrate animal life are ( pr(\nd significance 9 organic evolution because !y 7 ! direct prog5itors ( ! great gr\ps ( /ill high] ,v]tebrates :i* s9ce lat] ,paleozoic "t gradually increas$ 9 div]sity & complexity ( /ructure ?r\gh amphibians1 reptiles1 birds1 & mammals f9ally to man himself4 ,illu/ration3 ,fig4 #eh4--,re/orations ( *>act]i/ic ,devonian fi%es1 bas$ ^u actual fossils3 a1 a lung fi% ) leglike f9s 7aft] ,huasak(72 b1 a ganoid4 7,aft] ,ni*olson47 ,9 m>k$ contra/ to ! mo/ typical & highly organiz$ fi%es s abundant to-day1 all ,devonian fi%es 7 ( simple types ) c>tilag9\s skeletons & v]tebrat$ tails4 ,_m ( !m 7 also g5]aliz$ types1 t is1 associat$ ) _! cle>ly def9$ fi% *>act]s 7 o!rs connect+ !m ) c]ta9 high] ,v]tebrates1 z1 = example1 amphibians & reptiles4 ,?us all _! tail f9s 7 v]tebrat$ z 9 reptiles2 _! labyr9?9e1 int]nal too? /ructure 0 to be an amphibian feature :5 ^? creatures evolv$2 _m _h protective armor or bony scales l mo/ e>ly amphibians & _m mod]n reptiles2 & _m _h pair$ f9s :i* 7 some?+ l jo9t$ legs4 ,mo/ abundant & highly organiz$ ( ! ,devonian fi%es 7 ganoids1 *>act]iz$ by a cov]+ ( small plates or bony scales set toge!r b n ov]lapp+ l 9 typical mod]n fi%es4 ,_! intricate too? /ructure & limblike f9s /rongly sugge/ ! amphibians ( lat] ,paleozoic "t4 ,! skeleton ( c>tilage gradually became some:at ossifi$ dur+ succe$+ geologic p]iods4 ,f _! great pr(usion & div]sity 9 ! ,devonian p]iod ! ganoids h /eadily fall5 away until !y n[ h v few desc5dants l ! g> pike4 ,ano!r important gr\p ( rem>kable fi%es1 n[ totally ext9ct1 b common 9 ,devonian & some:at lat] "t1 _h heavy1 bony armor plates ov] ! =e "p ( ! body4 ,^? :i* grew to be fifte5 to tw5ty-five feet long 7 probably ! rul]s ( ! middle ,paleozoic seas4 ,ano!r rem>kable ,devonian fi% 0 able to brea! 9 bo? wat] & air because1 l _! few mod]n desc5dants1 !y _h bo? gills & lungs4 ,because ( _! leglike f9s & lung sac1 x is commonly believ$ t !y 7 prog5itors ( ! lat] ,paleozoic amphibians4 ,! simple/ ( all fi%es1 ! %>ks1 began 9 ! ,silurian1 und]w5t no important *ange ?r\gh ! millions ( ye>s s9ce1 & are n[ ( c\rse well repres5t$4 ,dur+ e>ly ,c5ozoic "t ! %>ks seem to h rea*$ culm9ation 9 size--sixty to eighty feet long1 ) tee? five or six in*es long4 ,among mod]n fi%es ! mo/ abundant by f>1 & ! mo/ highly organiz$1 are ! true bony fi%es1 call$ ! teleo/s1 :i* made _! fir/ appe>ance 9 ! middle ( ! ,mesozoic era4 ,^? e>lie/ =ms cle>ly %[ _! desc5t f ! ganoids4 ,app>5tly !y h n yet pass$ _! prime4 ,we %all n[ consid] ! next high] gr\p ( ,v]tebrates1 ! amphibians1 :i* brea! by gills :5 "y & lat] develop lungs4 ,_m live bo? on l& & 9 wat] l ! frogs4 ,unlike fi%es !y h legs ) toes & n f9s4 ,beg9n+ probably 9 ! ,devonian z a bran* ( ! fi%es1 amphibians %[$ a m>vel\s developm5t dur+ lat] ,paleozoic & v e>ly ,mesozoic times :5 !y rea*$ _! climax1 aft] :i* !y fell (f rem>kably1 be+ n[ relatively unimportant l ! frogs & salam&]s4 ,!y are ( special significance because !y 7 ! fir/ ( all ! back-bon$ animals 7,v]tebrates7 to inhabit ! l& :i* !y dom9at$ only until ! great rise ( reptiles ( ,mesozoic "t4 ,! reptiles 9 fact evolv$ f ! amphibians 9 ! late ,paleozoic :5 _m transition =ms occurr$4 7,plate #ae47 ,dur+ ^? anci5t days ! num]\s & v div]sifi$ amphibians 7 l giant salam&]s1 commonly five to eight feet long1 ) "o ,triassic =m fifte5 to tw5ty feet long1 & ) heavily armor$ skulls two to f\r feet long4 ,turn+ n[ to ! reptiles we f9d t !y are mu* m di/9ctly l& animals ?an ! prec$+ types ( ,v]tebrates4 ,reptilian life ( ! e>? began 9 late ,paleozoic "t z an evolution>y bran* ( ! amphibians4 ,! e>lie/ =ms 7 9 _m ways mu* l ! amphibians1 b gradually !y div]sifi$ & progress$ s t be=e ! close ( ! ,mesozoic era1 :i* has long be5 call$ ! ,age ( ,reptiles1 !y 7 ! rul]s ( ! _w4 ,!y cov]$ ! l& ) gigantic h]bivor\s & c>nivor\s =ms2 !y sw>m$ 9 ! sea1 &1 z lit]al dragons1 !y dom9at$ ! air4 7,scott47 ,mesozoic reptiles are ( special int]e/ & significance n only 9 !mselves1 b also because f "o ( _! bran*es ! birds 7 evolv$1 & f ano!r ! mammals4 ,9 advanc+ f ! amphibian to ! reptile ! evolution ( ! ,v]tebrates 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 7,norton47 ,s9ce ! reptiles ( ! ,mesozoic era con/itute "o ( ! few mo/ rem>kable & div]sifi$ classes ( animals :i* ev] inhabit$ ! e>?1 we %all attempt to give ! read] a fair idea ( ! mo/ typical gr\ps :i* h be5 totally ext9ct s9ce ! close ( ! ,mesozoic era "s millions ( ye>s ago4 ,( ! swimm+ reptiles :i* liv$ 9 ! seas _m types are kn[n & only a few w be describ$4 ,among ^! "o important type 0 ! i*?yosaur1 a fi%like =m :i* n uncommonly grew to be tw5ty to ev5 =ty feet long 7,plate #ah74 ,! l>ge head1 sometimes f\r or five feet long1 conta9$ z _m z #bjj big %>p tee? & enorm\s eyes up to a foot 9 diamet]4 ,! body 0 heavy set1 & ! neck v %ort4 ,!re 7 f\r %ort1 /\t swimm+ paddles1 & ! tail 0 v]tebrat$4 ,"s specim5s ( i*?yosaurs h be5 s p]fectly pres]v$ 9 ,mesozoic /rata t ev5 ! unborn "y are pla9ly se5 9 ! bodies6 ,9 "s cases x is actually possible to tell :at 0 ! la/ meal ( a p>ticul> i*?yosaur ^? millions ( ye>s ago2 9 "o specim51 = example1 rema9s ( #bjj creatures ( ! cuttle-fi% tribe hav+ be5 f\nd 9 ! exact position ( ! /oma*4 ,illu/ration3 ,fig4 #ei4--;,*>t %[+ ! ma9 bran*es 9 ! hi/ory ( ,v]tebrate 7back-bon$7 animal life rea*+ its culm9ation 9 man4 7,by ! au?or1 9 "p aft] ,clel&47 ,! mosasaurs ( ! late ,mesozoic 7 ! only real sea s]p5ts ( ! geologic ages4 ,!y 7 some?+ l ! i*?yosaurs1 b ) small] heads & mu* long]1 m sl5d]1 s]p5tlike bodies4 ,"s grew to be ?irty or =ty feet long4 ,plesiosaurs 7 p]haps ! /range/ ( all ! ,mesozoic m>9e reptiles4 ,!y grew to be =ty to fifty feet long1 ) /\t body1 v long1 sl5d] neck1 small head1 %ort tail1 & f\r long1 p[]ful swimm+ paddles :i* 7 di/9ctly leglike4 ,^! & ! mosasaurs 7 bo? fle% eat]s1 z %[n by ! %>p tee?4 ,illu/ration3 ,plate #ae4--7;a7 ,re/oration ( a ,late ,paleozoic 7,coal ,age7 ,l&scape4 ,%[+ ! ma9 k9ds ( plants :i* h ent]$ into ! mak+ ( mo/ ( our coal4 ,giant club mosses bo? ) & )\t bran*es1 9 ! left backgr\nd2 giant horsetail 7or sc\r+ ru%7 plants on ! "r2 & se$ f]ns 9 ! left =egr\nd4 ,a primitive reptile 9 ! wat]2 two l>ge amphibians or giant salam&]s1 call$ /egocephalians1 on ! l&2 & a great dragon fly1 two feet wide1 9 ! air4 7,f a draw+ by ,pr(4 ,willi/on4 ,c\rtesy ( ,d4 ,van ,no/r& ,co47 ,illu/ration3 ,plate #ae4--7;b7 ,photograph ( a ,fossil ,f]n or ,se$ ,f]n ,frond on a ,piece ( ,%ale ,millions ( ,ye>s ,old4 ,! specim5 is ( ! ,p5nsylvanian ,age & 0 tak5 f ! coal fields ( ,p5nsylvania4 7,aft] ,:ite1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #af4--,re/oration ,%[+ ! ,g5]al ,appe>ance ( ,"s ( ! ,l>ge/ ,animals ,:i* ,ev] ,trod ! ,e>?4 ,a m\nt$ skeleton 9 ! ,am]ican ,museum ( ,natural ,hi/ory is sixty-sev5 feet long1 & ! skeleton ( a simil> creature 9 ! ,c>negie ,museum1 ,pittsburgh1 is eighty-sev5 feet long4 ,!y liv$ millions ( ye>s ago dur+ ! middle & late ,mesozoic era4 7,aft] ,c4 ,r4 ,knight4 ,c\rtesy ( ! ,am]ican ,museum ( ,natural ,hi/ory1 ,new ,york47 ,! mo/ rem>kable walk+ reptiles ( all "t 7 ! d9osaurs or t]rible liz>ds4 ,we %all describe en\gh types ( ^! unique creatures to give ! read] a fair idea ( _! appe>ance & habits4 ,mo/ a/oni%+ ( all 7 ! sauropods includ+ ! l>ge/ animals :i* ev] trod ! e>?4 ,!y grew to be z mu* z sixty to n9ety feet or m 9 l5g?4 ,rem>kably well pres]v$ skeletons h be5 f\nd1 "o f ,utah1 eighty-sev5 feet long1 be+ m\nt$ 9 ! ,c>negie ,museum ( ,pittsburgh4 ,! l>ge/ ( ^! brutes /ood fifte5 to tw5ty feet high & !y mu/ h weigh$ ?irty to fifty tons4 ,! v long1 s]p5tlike neck & tail1 & v small head 7 grotesque features4 ,consid]+ ! /ructure ( ! d9osaurs1 ! k9d ( /rata 9 :i* !y are emb$d$1 & ! associat$ fossil rema9s1 x seems cle> t !y mo/ly liv$ 9 & ne> fre% wat] & on ne>-by l[l&s4 ,! "* ( _! tee? %[s t !y f$ entirely on s(t plants :i* !y mu/ h habitually bolt$ because _! tee? 7 n well adapt$ to gr9d+ food4 ,x is difficult to believe t a s+le huge bea/ c\ld h consum$ less ?an a few hundr$ p\nds ( vegetable matt] p] day1 &1 on acc\nt ( ! v small size ( ! head1 he mu/ h sp5t mo/ ( 8 "t eat+4 ,also ! comp>atively v small size ( ! bra91 & its simplicity ( /ructure1 r5d] x c]ta9 t !y 7 extremely /upid creatures4 ,to make up = ?is !y _h an enorm\s enl>gem5t ( ! sp9al cord 9 ! sacral region 7i4e41 ov] ! h9d legs74 ,?is sacral bra9--if we may s call x--0 t5 to tw5ty times bigg] ?an ! cranial bra94 ,x 0 necess>y 9 ord] to "w ! p[]ful h9d legs & tail4 7,le ,conte47 ,illu/ration3 ,fig4 #fj4--,skeleton ( a great f\r-legg$ 7sauropod7 d9osaur4 ,a m\nt$ skeleton 9 ! ,am]ican ,museum ( ,natural ,hi/ory1 ,new ,york1 is sixty-sev5 feet long4 ,?is creature liv$ millions ( ye>s ago dur+ ! ,jurassic p]iod4 7,aft] ,m>%47 ,ano!r d9osaur1 9 "s respects l ! sauropod1 0 ! /egosaur :i* grew to be tw5ty to ?irty feet long1 & heavi] ?an ! elephant4 ,unlike ! sauropod1 x _h a %ort neck & 0 armor$ ) a d\ble r[ ( great plates ov] its back1 & %>p sp9es 7"o to ?ree feet long7 t[>d ! end ( ! tail4 ,! excessive /upidity ( ! creature is prov$ by ! fact t its v simple bra9 weigh$ less ?an ?ree ounces6 ,/egosaurs 7 plant eat]s z indicat$ by ! too? /ructure1 &1 ?\gh !y look$ f]oci\s1 !y 7 probably n fight]s1 c]ta9ly at lea/ no?+ l ! c>nivor\s types ( d9osaurs we %all soon describe4 ,illu/ration3 ,fig4 #fa4--,skeleton ( ! curi\s k9d ( d9osaur 7/egosaur7 ( ,mesozoic ,age ) great bony plates ov] ! back4 ,l5g? ab\t ?irty feet4 7,aft] ,m>%47 ,! f]oci\s d9osaurs ( ,mesozoic "t 7 c>nivor\s1 or fle% eat]s1 z %[n by _! num]\s %>p tee? 9 relatively l>ge heads4 ,! l>ge/ kn[n type is ! tyrannosaur1 an almo/ p]fect skeleton ( :i*1 #dj feet long & #af feet high1 is m\nt$ 9 ! ,am]ican ,museum ( ,natural ,hi/ory 9 ,new ,york 7,plate #ag74 ,s f> z kn[n1 ?is 0 ! l>ge/ c>nivor\s animal :i* ev] walk$ on ! e>?4 ,x is evid5t f ! /ructure t x walk$ on its h9d legs1 ! front ones hav+ be5 mu* %ort] & us$ some?+ l arms4 ,!re 7 also v>i\s o!r small] =ms ( two-legg$ fle%-eat+ d9osaurs1 _m ( ! wond]fully pres]v$ tracks 9 ! ,triassic s&/ones ( ! ,connecticut ,riv] ,valley hav+ be5 made by su* creatures :5 !y walk$ ar\nd ov] s(t1 s&y mud flats at lea/ eight or t5 million ye>s ago4 ,! s&y mud ) its tracks became some:at h>d5$ & !n deeply buri$ "u mu* m s$im5t :i*1 ?r\gh ! ages1 has be5 erod$ (f1 ?us expos+ to view c]ta9 ( ! lay]s cov]$ ) tracks4 ,"s bones ( d9osaurs h also be5 f\nd 9 ! ,connecticut ,valley4 ,illu/ration3 ,fig4 #fb4--,skeleton 7re/or$7 ( a great two-legg$ d9osaur ( ! ,mesozoic era4 ,?is type ( plant eat] grew to be fully tw5ty-five feet long4 7,aft] ,m>%47 ,ano!r rem>kable type ( two-legg$ d9osaur 0 mu* l ! fle% eat]s j describ$1 b !y 7 plant eat]s4 ,! l>ge/ ( ^! grew to be #cj feet long & #ae to #bj feet high1 comp>able1 !re=e1 to ! tyrannosaur 9 size4 ,a wond]ful collection ( almo/ p]fect skeletons may be se5 9 ! museum 9 ,brussels1 ,belgium4 ,9 m9+ coal #a1jjj feet bel[ ! surface 9 ,belgium1 tw5ty-two complete skeletons & sev]al p>tial skeletons 7 f\nd 9 an anci5t riv] deposit ( ,cretace\s ,age4 ,a m>vel\sly pres]v$ specim5 ( "o ( ^! two-legg$ plant eat]s f\nd 9 ,wyom+1 has be5 call$ a d9osaur mummy because ! sk9 & mu* ( ! fle% ( ! creature _h %rivel$ d[n ^u its bones4 ,! m9ute/ details ( ! texture ( its sk9 are almo/ p]fectly pres]v$4 ,illu/ration3 ,fig4 #fc4--,skeleton ( a d9osaur 7tric]atops7 ) a l>ge rem>kable head4 ,?is creature grew to be tw5ty-five feet long dur+ ,cretace\s "t4 7,aft] ,m>%47 ,ano!r type ( d9osaur1 s diff]5t f ! o!rs1 %\ld be briefly describ$4 ,?is 0 tric]atops1 or ! ?ree-horn$ face bea/1 s nam$ because ( ! ?ree p[]ful horns :i* project$ =w>d f ! top ( ! v l>ge1 flatt5$ skull4 ,x grew to be tw5ty to tw5ty-five feet long4 ,skulls six to eight feet long h be5 une>!d4 ,j :]e ! bra9 might h develop$1 ! skull di%$ d[nw>d1 & s "o au?ority consid]s tric]atops to h _h ! l>ge/ head & smalle/ bra9 ( all ! great reptiles4 ,x is well kn[n t d9osaurs ( _m types liv$ dur+ ! great ,age ( ,reptiles1 ?\gh by no means all types rang$ ?r\gh ! :ole era4 ,no d9osaurs are def9itely kn[n to h cross$ ! l9e into ! ,c5ozoic era4 ,"o ( ! mo/ a/oni%+ facts 9 ! hi/ory ( animal life is ! ext9ction ( ! mighty d9osaurs1 b no v satisfactory explanation has yet be5 (f]$4 ,probably _! great size 0 a contribut+ factor1 = x is well kn[n t :ile v l>ge animals sp5d ne>ly all _! "t 9 eat+1 small animals sp5d a small proportion ( !irs1 & mo/ ( x 9 o!r activities4 ,n[1 z long z food is abundant1 ! l>g] animals ( a race h ! bett] *ances1 b if a sc>city ( food ensues1 ! l>g] animals may all be sudd5ly swept out ( exi/5ce4 7,mat!w47 ,:atev] may h be5 ! real reason = d9osaur ext9ction we c at lea/ be sure t ) ! ext5sive *anges 9 ! elevation ( l& areas 7,rocky ,m\nta9 ,revolution7 :i* m>k ! close ( ! ,mesozoic1 came ! )draw+ ( ! great inl& ,cretace\s seas along ! l[-ly+ %ores ( :i* ! d9osaurs _h _! home1 & ) ! consequ5t re/riction ( old haunts1 came ! blott+ out ( a h]oic race4 ,_! c>e] 0 n a brief "o1 = ! duration ( _! record$ evolution 0 twice t ( ! subsequ5t mammalian 7,c5ozoic7 age4 ,!y d n repres5t a futile attempt on ! "p ( nature to p ! _w ) creatures ( insignificant mom5t1 b are comp>able 9 maje/ic rise1 sl[ culm9ation1 & dramatic fall to ! greate/ nations ( antiquity4 7,s*u*]t47 ,among ! mo/ extraord9>y animals n only ( ! ,mesozoic1 b also ( all "t1 7 ! fly+ reptiles or lit]al dragons ( ! air4 ,"s 7 v small1 :ile o!rs 7 ! l>ge/ creatures :i* ev] flew1 ) a spread ( w+ ( tw5ty to tw5ty-five feet--twice t ( any mod]n bird4 ,unlike birds !y _h no fea!rs1 b ! two w+s consi/$ ( l>ge membranes 7batlike7 support$ by "o enorm\sly elongat$ f+] ( ea* front limb4 ,! o!r f+]s 7 arm$ ) %>p claws4 ,! e>ly ,mesozoic fly+ reptiles _h %>p tee?1 :ile ! lat] ones 7 mo/ly entirely too?less1 b all 7 c>nivor\s4 ,_! %ort bodies 7 suppli$ ) tails ( v>y+ l5g?s1 "o long-tail$ species hav+ a rudd] at ! end4 ,_! heads 7 fairly l>ge1 b ( light build4 ,! creature call$ pt]anodon 0 n only ! l>ge/ ( ! fly+ reptiles1 b also probably ! mo/ highly specializ$ creature :i* ev] liv$1 ev]y?+ possible app>5tly hav+ be5 sacrific$ to facilitate flight 7,plate #ah74 ,! holl[ bones 7 s wond]fully light & /rong t x has be5 e/imat$ t ! liv+ animal1 ) tw5ty-five foot spread ( w+1 & head f\r feet long1 c\ld n h weigh$ m ?an tw5ty-five p\nds6 ,! re> portions ( ! body & h9d limbs 7 v weak4 ,illu/ration3 ,fig4 #fd4--;,a small c>nivor\s fly+ reptile ( ,mesozoic "t4 ,spread ( w+s ab\t two feet4 7,re/or$ by ,m>%47 ,x %\ld n be ?\ght t ! above-describ$ gr\ps ( reptiles 7 ! only ones :i* exi/$ dur+ ,mesozoic "t4 ,!re 7 also c]ta9 gr\ps /ill liv+1 l turtles1 liz>ds1 & crocodiles1 b !y 7 d\btless mo/ly completely "u ! dom9ance ( c]ta9 ( ! n[ long-ext9ct types above describ$4 ,! olde/-kn[n fossil snakes are f v late ,mesozoic rocks1 :]e !y are small & comp>atively r>e4 ,m ?an likely !y evolv$ f liz>ds by det]ioration ( ! legs4 ,poison\s snakes 7 n evolv$ until e>ly 9 ! next 7,c5ozoic7 era4 ,we %all n[ turn our att5tion to next to ! highe/ class ( ,v]tebrate animals--! birds4 ,!y & ! mammals are ! only w>m-blood$ animals4 ,:at is _! ance/ry8 ,f :at orig9al /ock did !y bran* (f8 ,! olde/-kn[n bird liv$ dur+ ! ,jurassic p]iod1 & x 0 s decid$ly reptilian 9 "* z to r5d] x practically c]ta9 t birds are specializ$ desc5dants ( c]ta9 ,mesozoic reptiles1 ?\gh n1 z might be suppos$1 ( ! fly+ reptiles4 ,! few kn[n specim5s ( ! ,jurassic birds 7 f\nd 9 ! fam\s li?ographic lime/one qu>ries ( ,bav>ia4 ,at lea/ two ( ! specim5s are 9 a m>vel\s /ate ( pres]vation1 ) practically ! :ole skeleton intact & almo/ p]fect impressions ( ! fea!rs on ! rock4 ,t ! creature 0 really a bird is prov$ n only by its fea!rs1 b also its beak1 bra91 limb bones1 & feet4 ,among ! reptilian *>act]s are its long1 v]tebrat$ tail1 tee? set 9 sockets1 & long claws on ! w+s4 ,?is reptilian bird 0 ab\t ! size ( a small cr[4 ,by late ,cretace\s "t ! birds made notable evolution>y progress & !y became div]sifi$1 m ?an ?irty species be+ kn[n f ,cretace\s rocks4 ,^! 7 di/9ctly m mod]n 9 /ructure & appe>ance ?an ! ,jurassic bird4 ,! only important reptilian *>act]i/ic /ill reta9$ 0 ! possession ( tee?4 ,! tail _h become mu* %ort5$ & ! bra9 0 /ill relatively small] ?an 9 mod]n birds4 ,"o type1 ab\t n9e in*es high1 0 a p[]ful fli]1 z %[n by ! /rong keel & w+ bones4 ,ano!r important ,cretace\s type 0 almo/ :olly a wat] dwell]1 ) p[]fully develop$ legs us$ 9 swimm+4 ,its tee? 7 set 9 grooves in/ead ( 9 sockets1 ?us indicat+ deg5]ation ( too? /ructure4 ,?is type 0 notable = its size--five to six feet 9 l5g?4 ,illu/ration3 ,fig4 #fe4--;,an e>ly type ( bird ) tee?4 ,?is bird grew to a height ( ab\t n9e in*es 9 ,cretace\s "t1 millions ( ye>s ago4 7,re/or$ by ,m>%47 ,dur+ ! e>ly "p ( ! ,c5ozoic era birds became /ill m advanc$ & num]\s1 ) _m mod]n gr\ps repres5t$4 ,"s ( ! m primitive types 71 h[ev]1 /ill left ov] dur+ ! ,t]ti>y1 z1 = example1 a too!d bird1 9 :i* ! tee? 7 m]ely d5tations ( ! bill1 ?us be+ ! mo/ deg5]ate ( all types ( too? /ructure4 ,mammals comprise ! highe/ class ( all animals4 ,!y are1 ( c\rse1 all w>m blood$ & *>act]iz$ by suckl+ _! "y4 ,s f> z kn[n1 mammal life began 9 ! e>ly ,mesozoic era z a bran* ( primitive reptiles1 b !y made little progress ?r\gh\t ! era :5 !y occupi$ a v subord9ate position 9 ! animal _w4 ,!y 7 few 9 numb]1 small1 & primitive 9 /ructure4 ,!re is no evid5ce = ! ,mesozoic exi/5ce ( any ( ! high] =ms ( mammals1 t is1 ^? :i* give bir? to well-=m$ "y :i* are pr5atally atta*$ to ! "m by ! s-call$ plac5tum4 ,dur+ ! eons ( ! ,mesozoic1 f late ,triassic "t until its close1 ! mammals 7includ+ ! remote prog5itors ( humanity7 7 9 exi/5ce1 b held 9 su* effective *eck 7by reptiles7 t _! evolution>y progress 0 practically insignificant4 ,?is curb is /rik+ly illu/rat$ by ! wond]ful s]ies ( t9y jaws & tee? ( ^! dim9utive creatures f\nd 9 ! ,coman*ian 7e>ly ,cretace\s7 ( ,wyom+1 9 actual association ) ! s+le too? ( a c>nivor\s d9osaur1 _m times ! bulk ( ! l>ge/ mammalian jaw4 ,! removal ( ?is *eck result$ 79 ! ,t]ti>y p]iod7 9 ! spe$y evolution ( ! ar*aic mammals4 7,s*u*]t47 ,! ph5om5al developm5t ( mammals dur+ ! ,t]ti>y p]iod =ms "o ( ! mo/ wond]ful *apt]s 9 ! :ole evolution ( organisms4 ,ev5 v e>ly 9 ! ,t]ti>y1 _m important high] 7plac5tal7 types ( mammals _h evolv$1 & ! simpl]1 m primitive ,mesozoic =ms became v subord9ate4 ,by ! close ( ! ,t]ti>y ! high] types ( mammals _h become m>vel\sly diff]5tiat$ into mo/ ( ! pres5t-day gr\ps or types4 ,a v significant feature ( ! evolution 0 ! /eady increase 9 relative size ( bra94 ,! va/ numb]s ( fossil skeletons & bones ( mammals f\nd 9 ,t]ti>y /rata is sc>cely believable4 ,9 our brief discussion we c d no m ?an describe a few repres5tative examples ( ! ,c5ozoic evolution ( mammals4 ,! great div]sity ( mod]n plac5tal animals may be sugge/$ by a few examples1 z ! tig]1 dog1 horse1 camel1 elephant1 squirrel1 h$gehog1 :ale1 monkey1 & man4 ,=ms l ^!1 trac$ back ?r\gh _! ance/ors to ! v e>ly "p ( ! ,t]ti>y p]iod1 gradually become less & less di/9ct until !y _c be at all di/+ui%$ z sep>ate gr\ps1 b r !re are ance/ral g5]aliz$ =ms :i* %[ comb9ations ( features ( ! lat] gr\ps4 ,^? e>ly ,t]ti>y g5]aliz$ plac5tal mammals _h f\r feet ( primitive "*1 ) five toes on ea* foot2 ! :ole foot1 :i* f toe to heel t\*$ ! gr\nd1 0 n adapt$ to swift runn+2 ! tee? 7 simple 7primitive7 9 type & ( full orig9al numb] 7=ty-f\r72 ! toes 7 suppli$ ) nails :i* 7 ab\t int]m$iate betwe5 real claws & ho(s 9 /ructure2 & ! bra9 0 relatively mu* small] & simpl] 9 /ructure ?an 9 mo/ mod]n mammals4 ,illu/ration3 ,fig4 #ff4--;,*>t %[+ ! ma9 features ( int]e/ 9 ! evolution ( ! horse family ?r\gh sev]al million ye>s ( ! pres5t 7,c5ozoic7 era ( geologic "t4 7,aft] ,mat!w1 ,am]ican ,museum ( ,natural ,hi/ory47 ,! hi/ory ( ! horse family furni%es an excell5t illu/ration ( c]ta9 evolution>y *anges among mammals4 ,skeletons ( _m species1 rang+ f ! e>ly ,t]ti>y to ! pres5t1 h be5 f\nd 9 rem>kable /ate ( pres]vation repres5t+ e important *ange 9 ! hi/ory ( ! horse family4 ,a /udy ( ! *>t w make cle> "s ( ! mo/ /rik+ *anges :i* h tak5 place4 ,! olde/ memb] ( ! horse family repres5t$ on ! *>t 0 ab\t ! size ( a small fox1 ) f\r toes & a deg5]at$ fif? toe 7spl9t7 on ! front foot1 & ?ree toes & spl9t on ! h9d foot4 ,s9ce ! *>t 0 made a /ill m primitive =m1 ev5 m closely resembl+ ! orig9al five-to$ ance/or1 has be5 f\nd4 ,gradually ! middle toe enl>g$1 :ile ! o!rs disappe>$ except ! two spl9ts or v deg5]ate toes /ill left 9 ! mod]n horse4 ,increase 9 size ( ! animal & bra9 capacity accompani$ ^! *anges4 ,also ! tee? und]w5t notable *ange1 & two orig9ally sep>ate bones 7radius & ulna7 ( ! =eleg became consolidat$ into a s+le /rong] bone4 ,! ev5-to$ ho($ mammals ( to-day1 l ! de]1 pig1 & camel1 are also ! product ( evolution mu* l t ( ! horse1 except t two ( ! orig9al five toes h be5 equally develop$1 :ile ! o!rs h ei!r greatly deg5]at$1 z 9 ! pig1 or disappe>$ entirely1 z 9 ! camel4 ,! elephants1 or trunk-be>+ animals1 illu/rate a v diff]5t k9d ( evolution4 ,!y seem to h rea*$ _! climax ( developm5t 9 ! late ,t]ti>y :5 !y grew to be z mu* z #ad feet high1 & 7 m abundant & widespread ov] ! e>? ?an at any o!r "t4 ,! mod]n elephant1 l ! horse1 has be5 trac$ back ?r\gh _m int]m$iate =ms to its primitive e>ly ,t]ti>y ance/ry4 ,"s ( ! mo/ important evolution>y *anges took place 9 ! head portion4 ,! trunk is a highly develop$ =m ( sn\t1 ! e>lie/ =m ( :i* 0 mu* l t ( ! mod]n tapir4 ,! tusks are highly specializ$ & elongat$ tee?4 ,dur+ ! e>li] hi/ory ! *9 0 v long & support$ %ort tusks1 s t !re 7 !n f\r tusks4 ,c>nivor\s mammals1 l tig]s & wolves1 & gnaw]s1 l rats & squirrels1 may also be trac$ back to g5]aliz$ e>ly ,t]ti>y types4 ,ano!r k9d ( evolution is well illu/rat$ by c]ta9 mammals :i*1 ev5 9 e>ly ,t]ti>y "t1 s ?or\ghly adapt$ !mselves to a wat] environm5t z to become :ales1 porpoises1 etc4 ,illu/ration3 ,fig4 #fg4--;,comp>ison ( feet ( monkeys & man4 ,! primates include ! highe/ gr\p ( all ,v]tebrates1 & !re=e ( all animals4 ,monkeys1 apes1 & man belong to ! primates4 ,!re is no evid5ce :atev] = ! appe>ance ( ev5 ! simple/ & mo/ primitive =ms be=e ! op5+ ( ! ,c5ozoic era1 b ev5 v e>ly 9 ,t]ti>y "t1 lemurs & primitive types ( monkeys exi/$4 ,lat] 9 ! ,t]ti>y true monkeys & apes 7 common1 & by ! close ( ! p]iod "s apes 7 highly en\gh develop$ to /rongly resemble c]ta9 ( ! olde/ & mo/ primitive types ( man4 ,we h1 h[ev]1 no positive k ( ! exi/5ce ( man 9 ev5 ! late/ ,t]ti>y4 ,9 ! light ( mu* evid5ce 9 reg>d to ! antiquity ( man1 x seems improbable t true human fossils w ev] be f\nd 9 rocks old] ?an ! ,quat]n>y1 ?\gh if we are will+ to desc5d 7f> en\gh 9 ! human scale t[>d apes7 x is n unlikely t man-apes may be discov]$ 9 v late ,t]ti>y rocks4 ,! difficulty comes 9 ! classification4 ,:]e are we to draw ! l9e betwe5 ! high] apes & ! l[e/ =ms ( man8 ,b ?is v difficulty is "o ( ! /ronge/ argum5ts 9 favor ( ! organic evolution ( man because practically all int]m$iate =ms betwe5 true man & c]ta9 o!r high-grade primates are kn[n f ! /rata4 ,! foll[+ tabul> summ>y ( ! geological hi/ory ( man is bas$ ^u ! "w ( mo/ ( ! able/ /ud5ts ( ! subject4 #c4 ,homo sapi5s ,hi/oric 7bronze & iron7 age4,mod]n 7e4g41 mod]n man7 ,neoli?ic 7rec5t /one7 age ,po/glacial 7c>efully %ap$ & b poli%$ /one implem5ts7 prehi/oric ---------------------------------------- ------------------------------- #b4 ,homo primig5ius ,upp] ,paleoli?ic 7anci5t ,late ,glacial 7e4g41 ,ne&]?al /one7 age 7r\gh bone man7 & /one implem5ts1 cave frescoes1 bone c>v+s1 etc47 ,l[] ,paleoli?ic 7anci5t ,middle ,glacial /one7 age 7rude /one implem5ts ( s-call$ riv] man7 ---------------------------------------- ------------------------------- #a4 ,e>ly ance/ral =ms ,possibly "s v crude ,e>ly ,glacial 7e4g41 ,pi!can?ropus /one implem5ts & possibly erectus7 late ,t]ti>y ---------------------------------------- ------------------------------- ,( ! e>ly ance/ral =ms1 t is1 ^? :i* 7 r di/9ctly man-apes1 two w be v briefly ref]r$ to4 ,"o ( ^!1 kn[n z ,pi!can?ropus erectus1 0 a rem>kable creature ^: p>tial skeleton1 consi/+ ( ! upp] "p ( a skull1 l[] jaw1 sev]al tee?1 & a ?igh bone1 0 f\nd 9 e>ly ,quat]n>y deposits 9 ,java 9 #ahia4 ,x 0 c]ta9ly a man-ape or possibly ape-man ( l[ ord]1 ab\t #e-a_/b feet high4 ,! skull has a l[ cr[n1 v rec$+ =ehead1 & prom95t br[ ridges1 b ! bra9 capacity is #hej cubic c5timet]s1 z comp>$ to #ejj cubic c5timet]s 9 ord9>y high] apes1 & ne>ly #a1ejj cubic c5timet]s 9 ! av]age mod]n man4 ,! v rec5tly ext9ct v l[-type aborig9es ( ,tasmania _h a skull capacity ( #a1aii cubic c5timet]s4 ,9 #aijg ! l[] jaw ( an an?ropoid or manlike ape set ) r human tee? 0 f\nd associat$ ) v crude /one implem5ts sev5ty-five feet bel[ ! surface 9 riv]-deposit$ s& 9 ,g]many4 ,x is ( ei!r e>ly or middle ,glacial "t & q c]ta9ly repres5ts a l[] ord] creature ?an ! olde/ ,paleoli?ic man z describ$ bel[4 ,_m bones & implem5ts ( ,paleoli?ic man 7see above table7 h be5 f\nd ma9ly 9 riv] gravels & caves4 ,! relative ages ( ,paleoli?ic human bones & implem5ts are be/ det]m9$ by ! associat$ fossil animals4 ,?us ! mo/ anci5t truly human fossils are f\nd directly associat$ ) bones ( v old types ( elephants1 rh9oc]oses1 & hippopotamuses :i* are def9itely kn[n to h liv$ dur+ middle or e>ly middle ,glacial 7,quat]n>y7 "t correspond+ to e>ly ,paleoli?ic "t4 ,a v cons]vative e/imate w\ld make ! age ( su* v old human rema9s at lea/ #aej1jjj to #bej1jjj ye>s because ! ,ice ,age 0 at lea/ #ejj1jjj ye>s long4 ,9 a lat] human /age !re are _m associations ) ext9ct animals l an old] type ( mammo?1 cave be>1 cave hy5a1 & o!rs ( lat] ,glacial "t e/imat$ at #ej1jjj to #aej1jjj ye>s ago4 ,la/ ( all 0 ! late/ ,paleoli?ic /age correspond+ to ! close ( ! ,ice ,age1 ! human rema9s ( :i* are f\nd associat$ ) re9de] & ! late/ mammo?s :i* roam$ 9 great numb]s across ,europe4 ,?is 0 probably n m ?an #cj1jjj to #ej1jjj ye>s ago4 ,paleoli?ic man is s call$ because he fa%ion$ /one weapons & implem5ts4 ,! /ructure ( skull & skeleton %[s him to h be5 a l[-type savage1 some?+ ov] five feet high on ! av]age1 ) a =w>d /oop+ c>riage4 ,! av]age ,paleoli?ic bra9 0 n greatly inf]ior 9 size to t ( mod]n civiliz$ man1 b x 0 n s highly organiz$ & occupi$ a ?ick skull ) mu* l[] =ehead & heavy br[ ridges4 ,! bu%m5 ( ,au/ralia & ! rec5tly ext9ct ,tasmanians are ! ne>e/ mod]n resemblances4 ,_m f9e specim5s ( ,paleoli?ic man h be5 f\nd1 especially 9 cave deposits4 ,t he 0 an exp]t hunt] is prov$ by ! great accumulation ( bones ( n[ ext9ct animals f\nd 9 & ab\t 8 haunts or camps1 bones repres5t+ at lea/ #ajj1jjj horses hav+ be5 f\nd ar\nd a s+le camp site6 ,illu/ration3 ,fig4 #fh4--;,comp>ison ( skulls3 a1 ,paleoli?ic 7,ne&]?al7 man2 b1 mod]n man4 7,aft] ,woodw>d1 ,briti% ,museum47 ,only two among ! _m kn[n ,paleoli?ic man localities w be briefly describ$4 ,9 ! ,p]igord di/rict ( s\?we/]n ,france a numb] ( caves conta9 human relics rang+ 9 age f e>ly to late ,paleoli?ic4 ,( special int]e/ among ^! relics are fi%hooks made ( bone1 & crude sket*es ( animals su* z ! mammo? & re9de] n[ ext9ct 9 t region4 ,! ,aurignac cave1 also 9 ,france1 0 no d\bt a family or tribal burial place4 ,sev5te5 ,paleoli?ic human skeletons1 associat$ ) bones ( ext9ct animals & crude art works1 7 f\nd 9 ! cave4 ,ne> ! entrance !re 7 a%es & *>coal mix$ ) burn$ & split bones ( ext9ct animals4 ,c]ta9 ( ! caves occupi$ by late ,paleoli?ic man h _! walls decorat$ ) sket*es & ev5 color$ pictures4 ,^! are1 !re=e1 ! olde/ kn[n art gall]ies4 ,an excell5t example is ! cave at ,altamira 9 nor!rn ,spa94 ,z we glance at ! pictures "o ( ! fir/ ?+s to impress u is ! excell5ce ( ! draw+1 ! proportions & po/ures be+ unusually good4444 ,! next obs]vation may be t1 9 spite ( ?is p]fection ( te*nique1 !re is no p]spective composition--t is1 no attempt to comb9e or gr\p ! figures4444 ,x is also cle> t ! "w ( _m diff]5t arti/s is repres5t$1 cov]+ a consid]able p]iod ( "t4 ,! walls %[ traces ( _m o!r pa9t+s t 7 eras$ to make way = new "w4 7,wissl]47 ,illu/ration3 ,fig4 #fi4--,sket* ( a pa9t+ by ,paleoli?ic man f\nd 9 a cave 9 we/-c5tral ,france4 ,v>i\s animals1 includ+ ! ext9ct mammo? elephant1 are repres5t$4 7,c\rtesy ( ,am]ican ,museum ( ,natural ,hi/ory47 ,! ,neoli?ic1 or rec5t /one age 0 a gradual developm5t f ! late ,paleoli?ic1 & man 0 !n m highly develop$ & m simil> 9 /ructure to mod]n man4 ,8 /one implem5ts 7 m p]fectly made1 & (t5 m or less poli%$ & gr\nd at ! edges4 ,! 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 piles4444 ,neoli?ic man 9 ,europe _h le>n$ to make pott]y1 to sp9 & weave l951 to hew timb]1 & build boats1 & to gr[ :eat & b>ley4 ,! dog1 horse1 ox1 %eep1 goat1 & hog _h be5 dome/icat$4 7,norton47 ,man is l9k$ to ! pa/ ?r\gh ! sy/em ( life1 ( :i* he is ! la/1 ! complet+ creation4 ,b1 unlike o!r species ( t clos+ sy/em ( ! pa/1 he1 ?r\gh 8 spiritual nature1 is m intimately connect$ ) ! op5+ future4 7,j4 ,d4 ,dana47 ,,*apt] ,,xx ,,m9]alogy ,we are m or less famili> ) ! division ( all mat]ials ( nature into ! animal1 vegetable1 & m9]al k+doms4 ,) slight exceptions m9]als are ! mat]ials :i* make up ! kn[n "p ( ! e>?4 ,9 a v real s5se1 !n1 m9]alogy is ! mo/ fundam5tal ( ! v>i\s bran*es ( ! great sci5ce ( geology because ! ev5ts ( e>? hi/ory1 z int]pret$ by ! geologi/1 are record$ 9 ! m9]al matt] 7includ+ mo/ rocks7 ( ! e>?4 ,:5 we exam9e ! rocky mat]ial or m9]al matt] ( ! e>? 9 any region we f9d t x consi/s ( v>i\s k9ds ( sub/ances ea* ( :i* may be recogniz$ by c]ta9 *>act]i/ics4 ,ea* def9ite sub/ance 7b>r+ ^? ( organic orig97 is call$ a m9]al4 ,or1 m specifically1 a m9]al is a natural1 inorganic1 homog5e\s sub/ance ( def9ite *emical composition4 ,accord+ to ?is def9ition a m9]al mu/ be f\nd ready made 9 nature1 mu/ n be a product ( life1 mu/ be ( ! same nature ?r\gh\t1 & its composition mu/ be s def9ite t x c be express$ by a *emical =mula4 ,all artificial sub/ances1 su* z laboratory & furnace products1 are exclud$ f ! category ( m9]als4 ,coal is n a m9]al because x is bo? organic & ( indef9ite composition4 ,a few examples ( v common sub/ances :i* p]fectly satisfy ! def9ition ( a m9]al are qu>tz1 feldsp>1 mica1 calcite1 & magnetite4 ,only two sub/ances--wat] & m]cury--are ord9>ily liquid m9]als4 ,!re are ne>ly a ?\s& di/9ct m9]al species1 & to !m & _! v>ieties sev]al ?\s& names h be5 appli$4 ,x is a surpris+ fact t ( ! eighty or m *emical elem5ts1 t is sub/ances :i* _c be subdivid$ into simpl] ones1 only eight make up m ?an #ih p] c5t ( ! weight ( ! cru/ ( ! e>?1 ?\gh1 ) "o v slight exception1 none ( ! eight exi/ z su* 9 m9]al =m4 ,! eight elem5ts are oxyg5 7ne>ly #ej p] c5t71 silicon 7ov] #be p] c5t71 alum9um 7ov] #g p] c5t71 iron 7ov] #e p] c5t71 calcium 7or lime71 magnesium 7or magnesia71 sodium 7or soda71 & potassium 7or pota%74 ,c]ta9 rock =mations are made up ess5tially ( b "o m9]al 9 ! =m ( num]\s gra9s z1 = example1 lime/one1 :i* consi/s ( calcite 7c>bonate ( lime74 ,mo/ ( ! ord9>y rocks are1 h[ev]1 made up ( two or m m9]als me*anically b\nd toge!r4 ,?us1 9 a specim5 ( granite on ! au?or's desk sev]al di/9ct m9]al sub/ances are di/+ui%able by ! nak$ eye4 ,^! m9]al gra9s are f "o to five millimet]s across4 ,mo/ common among !m are h>d1 cle>1 glassy gra9s call$ qu>tz2 ne>ly :ite1 h>d gra9s1 ) smoo? faces1 call$ feldsp>2 small1 silv]y :ite plates1 easily sep>able into v ?9 flakes1 call$ mica2 & small1 h>d1 black gra9s1 call$ magnetite4 ,x is ! bus9ess ( ! m9]alogi/ to le>n ! *>act]s ( ea* m9]al1 h[ !y may be di/+ui%$ f ea* o!r1 h[ !y may be classifi$1 h[ !y are f\nd 9 nature1 & :at economic value !y may h4 ,x is an important "p ( ! bus9ess ( ! geologi/ to le>n :at individual m9]als comb9e to =m ! _m k9ds ( rocks1 h[ su* rocks orig9ate1 :at *anges !y h und]gone1 & :at geological hi/ory !y record4 ,x is ?us cle> t ! great sci5ce ( geology is mu* broad] 9 its scope ?an m9]alogy4 ,"o ( ! mo/ rem>kable facts ab\t m9]als is t mo/ ( !m by f> h a cry/all9e /ructure1 t is !y are built up ( t9y p>ticles kn[n z molecules4 ,su* cry/all9e m9]als are (t5 m or less regul> solid =ms b\nd$ by plane faces & %>p angles1 su* =ms be+ kn[n z cry/als4 ,h[ d cry/als develop su* regul>ity ( =m8 ,any solid is consid]$ to be made up ( _m v t9y 7submicroscopic7 molecules held toge!r by an attractive =ce call$ cohesion4 ,9 liquids ! molecules may m or less freely roll ov] ea* o!r1 ?us alt]+ ! %ape ( ! mass )\t disrupt+ x4 ,9 gases ! molecules are consid]$ to be relatively long di/ances ap>t & mov+ rapidly4 ,dur+ ! process ( *ange ( a sub/ance f ! condition ( a liquid or gas to t ( a solid1 due to l[]+ ( temp]ature or evaporation1 ! cohesive =ce pulls ! p>ticles 7molecules7 toge!r into a rigid mass4 ,"u favorable conditions su* a solid has a regul> polyh$ral =m4 ,?is results f ! fact t ! p>ticles or molecules ( ! sub/ance :i*1 :ile x 0 liquid or gase\s1 roll$ ab\t on "o ano!r1 h be5 9 "s way arrang$1 gr\p$ & built up4 ,to illu/rate ?is1 suppose a quantity ( small %ot to be p\r$ into a glass3 ! %ot w repres5t ! molecules ( a sub/ance 9 ! liquid /ate1 z = example a solution ( alum4 ,if1 n[1 we suppose ^! same %ot to be coat$ ) v>ni% or glue s t !y w adh]e to ea* o!r1 & imag9e !m gr\p$ z %[n 9 ,figure #gj;a1 !y w repres5t ! arrangem5t ( ! molecules ( ! alum aft] x has become solid or cry/alliz$4 ,?is arrang+1 gr\p+1 & pil+ up ( molecules is call$ cry/allization1 & ! solid =m$ 9 ?is way is call$ a cry/al4 ,figures #gj;b & #gj;c %[ ! %ot arrang$ to reproduce two common =ms ( cry/als 7e4g41 fluorite & calcite74 7,:itlock47 ,illu/ration3 ,fig4 #gj4--,piles ( %ot arrang$ to give "s idea ( ! mann] 9 :i* molecules are b\nd toge!r 9 v>i\s cry/al =ms4 7,aft] ,:itlock1 ,new ,york ,museum47 ,a comb9ation ( c]ta9 facts reg>d+ cry/als furni% all b absolute pro( ( "s sort ( regul>ity ( arrangem5t ( p>ticles )9 !m4 ,among su* facts are ! foll[+3 7#a7 ! wond]ful regul>ity ( arrangem5t ( faces ^u cry/als is practically impossible to acc\nt = except z ! outw>d manife/ation ( regul>ity ( /ructure or sy/ematic network arrangem5t ( ! int]ior2 7#b7 mo/ cry/als split or cleave m or less p]fectly 9 "o or m directions presumably 9 accordance ) c]ta9 lay]$ /ructure ( ! con/itu5t p>ticles2 7#c7 all ( ! _m kn[n =ms ( cry/als c be accurately gr\p$ 9 reg>d to _! effects ^u ! passage ( light 7especially pol>iz$ light7 ?r\gh !m1 ea* k9d or type ( network /ructure presumably produc+ a diff]5t effect ^u light2 & 7#d7 ,x-ray photographs h prov$ t p>ticles1 or at lea/ gr\ps ( p>ticles1 are v sy/ematically arrang$ )9 cry/als4 ,x w be in/ructive = u to make a comp>ison betwe5 ! gr[? ( cry/als & organisms4 ,bo? really gr[1 b ea* species ( organism is r def9itely limit$ 9 size :ile !re is no kn[n limit to ! size :i* may be atta9$ by a cry/al s long z mat]ial is suppli$ to x "u prop] conditions4 ,z a matt] ( fact cry/als v>y 9 size f microscopic to sev]al feet 9 l5g?1 ^? less ?an an in* 9 l5g? be+ mo/ abundant by f>4 ,organisms mo/ly gr[ f )91 :ile cry/als gr[ f mat]ial ext]nally add$4 ,x is an a/oni%+ fact t 9 cry/als z well z organisms gr[? takes mo/ rapidly on a w\nd or brok5 place4 ,?us if a cry/al is remov$ f ! solution 9 :i* x is gr[+ & put back aft] a corn] has be5 brok5 (f1 ! fractur$ surface w build up m rapidly ?an ! re/4 ,f9ally1 cry/als are n necess>ily limit$ 9 age l organisms4 ,"u c]ta9 natural conditions1 z1 = example1 wea!r+1 cry/als may decay or be brok5 up2 b :]e !y are protect$ z con/itu5t p>ts ( rock =mations well bel[ ! e>?'s surface !y may rema9 un*ang$ = indef9ite millions ( ye>s4 ,?us 9 a l$ge ( ! mo/ anci5t kn[n or ,ar*eozoic rock only rec5tly laid b>e by erosion "o may see cry/als :i* are precisely z !y 7 :5 !y cry/alliz$ _m millions ( ye>s ago4 ,"o ( ! mo/ rem>kable prop]ties ( a cry/al is its symmetry1 by :i* is meant ! great] or less degree ( regul>ity 9 ! arrangem5t ( its faces1 edges1 & v]tices4 ,a giv5 sub/ance may1 accord+ to circum/ances1 cry/allize 9 a v>iety ( =ms or comb9ations ( =ms1 b1 ) v few exceptions1 all cry/als ( a giv5 sub/ance exhibit ! same k9d or grade ( symmetry4 ,!re are ?ree k9ds ( cry/al symmetry1 namely1 9 respect to a plane1 a l9e or axis1 & a po9t or c5t]4 ,a plane ( symmetry divides a cry/al into halves 9 su* a way t = e po9t on "o side ( ! plane !re is a correspond+ po9t directly opposite on ! o!r side4 ,cry/als may be cut into halves along v>i\s surfaces :i* are n symmetry planes4 ,an axis ( symmetry is a l9e ab\t :i* a complete rotation 7or 9 a few cases rotation comb9$ ) reflection7 br+s ! cry/al into ! same relative position two1 ?ree1 f\r or six times1 ^! be+ call$ two1 ?ree1 f\r1 & sixfold axes ( symmetry--no o!rs be+ possible4 ,a cry/al has a c5t] ( symmetry :5 any l9e pass+ ?r\gh x enc\nt]s correspond+ po9ts at equal di/ances f x on opposite sides4 ,!re are j #cb classes or comb9ations ( ! symmetry elem5ts among cry/als & j #bcb def9ite cry/al =ms4 ,n only is x demon/rable t no m c exi/1 b actual exp]i5ce ) cry/als ( hundr$s ( species ( m9]als has nev] reveal$ any m4 ,obvi\sly1 !n1 symmetry furni%es u ) a v sci5tific basis ( classification ( cry/als1 all ( ! #bcb cry/al =ms con/itut+ ! #cb symmetry classes be+ 9 turn ref]able to sev5 fundam5tal cry/al sy/ems4 ,to br+ out ! relations ( ! faces ( a cry/al & fur!r aid 9 classification1 prom95t1 /raight l9es or directions pass+ ?r\gh ! c5t] ( a cry/al are *os5 z cry/allographic axes4 ,su* axes may or may n co9cide ) symmetry axes4 ,bas+ our def9itions ^u bo? symmetry axes & cry/allographic axes1 ! sev5 sy/ems are z foll[s3 #a4 ,isometric4 ,!re mu/ be at lea/ f\r ?reefold axes ( symmetry1 :ile ! highe/ grade symmetry class ( ! five 9 ! sy/em includes ?ree f\rfold1 f\r ?reefold1 & six tw(old axes ( symmetry2 n9e planes ( symmetry2 & a c5t] ( symmetry4 ,!re are ?ree int]*angeable cry/allographic axes at "r angles to ea* o!r4 ,illu/ration3 ,fig4 #ga4--;,figures %[+1 a1 cry/al axes ( ,isometric sy/em2 b1 po9ts ( em]g5ce ( ! n9e axes ( symmetry 9 a cube ( ! ,isometric sy/em2 c1 n9e planes ( symmetry 9 a cubic cry/al4 7,aft] ,:itlock1 ,new ,york ,/ate ,museum47 #b4 ,tetragonal4 ,!re mu/ be "o & only "o f\rfold symmetry axis1 :ile ! highe/ ( its sev5 symmetry classes conta9s also f\r tw(old axes ( symmetry2 five planes2 & a c5t]4 ,*>act]iz$ by ?ree cry/allographic axes at "r angles to ea* o!r1 only two ( !m int]*angeable4 #c4 ,trigonal4 ,*>act]iz$ by "o & only "o ?reefold symmetry axis1 ! highe/ ( ! five classes hav+ also ?ree tw(old axes2 f\r planes2 & a c5t]4 ,cry/allographic axes z = hexagonal4 #d4 ,hexagonal4 ,"o & only "o sixfold axis ( symmetry mu/ be pres5t1 b ! highe/ ( ! sev5 classes also has six tw(old axes2 sev5 planes2 & a c5t]4 ,*>act]iz$ by f\r cry/allographic axes1 "o v]tical & ?ree int]*angeable horizontal axes mak+ angles ( #fj degrees ) ea* o!r4 #e4 ,or?orhombic4 ,!re mu/ be no axis ( symmetry high] ?an a tw(old & ?ree prom95t directions 7i4e41 p>allel to important faces7 at "r angles to ea* o!r1 ! highe/ grade ( ! ?ree classes hav+ ?ree tw(old axes2 ?ree planes2 & a c5t]4 ,!re are ?ree non9t]*angeable cry/allographic axes at "r angles4 #f4 ,monocl9ic4 ,!re is no axis ( symmetry high] ?an a tw(old & only two prom95t directions at "r angles to ea* o!r1 ! highe/ ( ! ?ree classes hav+ "o tw(old axis2 "o plane2 & a c5t]4 ,!re are ?ree non9t]*angeable cry/allographic axes1 only two ( :i* are at "r angles4 #g4 ,tricl9ic4 ,!re is no axis ( symmetry ( any k9d1 & !re are no prom95t directions at "r angles4 ,"o ( ! two classes has a c5t] ( symmetry only1 & ! o!r no symmetry at all4 ,*>act]iz$ by ?ree non9t]*angeable cry/allographic axes1 none at "r angles4 ,a fact :i* %\ld be /rongly emphasiz$ is t cry/als only1 ( all ! objects ( nature1 c be def9itely ref]r$ to ! above sev5 sy/ems compris+ ! #cb classes ( symmetry1 & #bcb cry/al =ms4 ,s9ce !re are ab\t #a1jjj m9]al species & only #bcb fundam5tal =ms1 x necess>ily foll[s t two or m species may cry/allize 9 ! same =m )9 a class1 s t x is n always possible to tell ! species ( m9]al m]ely by its cry/al =m4 ,x is1 h[ev]1 a rem>kable fact t1 :]e two or m sub/ances cry/allize 9 ! same class 7i4e41 %[ ! same grade ( symmetry7 ea* sub/ance almo/ inv>iably exhibits cry/al habit :i* is a pron\nc$ t5d5cy to cry/allize 9 c]ta9 relatively few =ms or comb9ations ( =ms out ( ! _m possibilities4 ,x is cle>1 !n1 t grade ( symmetry comb9$ ) habit are ( great practical value 9 det]m9+ cry/alliz$ m9]als1 because1 on ! basis ( symmetry1 a cry/al is ref]r$ to a c]ta9 def9ite symmetry class 9 :i* only a limit$ numb] ( sub/ances cry/allize1 & !n1 by its *>act]i/ic habit1 ! p>ticul> sub/ance c be told4 ,illu/ration3 ,fig4 #gb4--;,figures illu/rat+ ?ree cry/al =ms ) exactly ! same symmetry elem5ts2 a & b are sep>ate =ms1 & c is a comb9ation ( ! two4 ,! m9]al g>net ne>ly always cry/allizes 9 "o ( ^! =ms4 ,f ! above discussion x %\ld n be presum$ t cry/als always develop ) p]fect geometric symmetry4 ,z a matt] ( fact su* is seldom ! case because1 due to v>iations ( conditions or int]f]5ce ( surr\nd+ cry/als 9 liquids 7ord9>y or molt571 a cry/al usually gr[s m rapidly 7by build+ out faces7 9 c]ta9 directions ?an 9 o!rs4 ,"u su* conditions actual cry/als are said to become di/ort$ because !y are n geometrically p]fect4 ,:e!r geometrically p]fect or n1 all cry/als respond to ! law ( con/ancy ( int]facial angles :i* means t on all cry/als ( ! same sub/ances ! angles betwe5 simil> 7correspond+7 faces are always equal4 ,?is is "o ( ! mo/ fundam5tal & rem>kable laws ( m9]als4 ,t x mu/ be true foll[s f ! fact t ! cry/al faces m]ely outw>dly express 9 def9ite =m ! def9ite int]nal /ructure or arrangem5t ( p>ticles :i* h built up ! cry/al4 ,9 o!r words1 ! real /ructural symmetry ( a cry/al nev] v>ies no matt] h[ mu* its geometric symmetry may v>y4 ,! practical application ( ! law ( con/ancy ( int]facial angles lies 9 ! fact t 9 _m cases a m9]al may actually be id5tifi$ m]ely by measur+ ! int]facial angles ( its cry/al =m4 ,! relative l5g?s ( ! cry/allographic axes is a v important feature ( all cry/als except ^? ( ! isometric sy/em 9 :i* ! axes are always ( equal l5g? s t ! ratio is #a3a3a4 ,9 all ! o!r sy/ems1 h[ev]1 at lea/ "o axis diff]s 9 l5g? f ! o!rs &1 s9ce ! am\nt ( diff]5ce is absolutely *>act]i/ic ( ea* sub/ance1 ! axial ratio ( a cry/al1 :5 c>efully det]m9$ by measurem5t ( ! angles betwe5 ! diff]5t faces1 af=ds a nev]-fail+ me?od ( det]m9+ ! m9]al = all sy/ems except ! isometric4 ,by way ( illu/ration1 ! tetragonal cry/al ( ! m9]al zircon1 ) only "o axis diff]5t 9 l5g?1 %[s ! v def9ite axial ratio #a3a3j4fd1 :ile ! or?orhombic cry/al ( sulphur1 ) all ?ree axes ( diff]5t l5g?s1 has an axial ratio #j4hac3a3a4ijc4 ,^! ratios ( c\rse always hold true no matt] :at ! size or p>ticul> outw>d =m ( ! cry/al4 ,z might be expect$ f ! above discussion ( ! rem>kable /ructure ( cry/als1 exp]i5ce has prov$ t ! relative l5g?s ( all int]cepts 7or di/ances f ! c5t]7 ( all faces ^u any cry/al c be express$ by :ole numb]s1 def9ite fractions1 or inf9ity4 ,x necess>ily foll[s t ! ratios betwe5 ! int]cepts ( ! faces ( any face on a cry/al to ^? ( any o!r face on ! same cry/al may always be express$ by rational numb]s1 & ?is is kn[n z ! law ( def9ite ma!matical ratio4 ,x is a rem>kable fact t v small :ole numb]s or fractions1 or inf9ity or z]o1 w always express ! int]cepts ( any cry/al face4 ,?us f> our discussion has c5t]$ ab\t cry/als z individuals1 b1 9 mo/ cases by f>1 !y =m gr\ps or aggregates4 ,mo/ commonly cry/al gr\p+ is v irregul>1 b by no means r>e is p>allel gr\p+ :]e :ole cry/als1 or m usually p>ts ( cry/als1 h all correspond+ p>ts exactly p>allel4 ,b mo/ rem>kable ( all are ! tw9 cry/als 9 :i* two or m cry/als int]gr[n or 9 contact h all correspond+ p>ts 9 exactly rev]se ord]4 ,! condition+ circum/ances "u :i* tw9 cry/als develop are unkn[n4 ,9 ! light ( ! facts & pr9ciples above expla9$1 ! read] w m ?an likely agree ) ! au?or t cry/als rank v high among nature's mo/ wond]ful objects4 ,b !re are /ill o!r *>act]i/ic features ( cry/als naturally result+ f _! m>vel\s /ructure4 ,"s ( ^! w n[ be briefly ref]r$ to4 ,illu/ration3 ,fig4 #gc4--;,figures illu/rat+ tw9 cry/als3 a1 gypsum 7,monocl9ic sy/em72 b1 fluorite 7,isometric sy/em72 c1 cassit]ite 7,tetragonal sy/em74 7,aft] ,new ,york ,/ate ,museum ,bullet947 ,_m cry/als & cry/all9e sub/ances exhibit ! important prop]ty kn[n z cleavage :i* is ! m>k$ t5d5cy to break easily 9 c]ta9 directions yield+ m or less smoo? plane surfaces4 ,z w\ld be expect$1 a cleavage surface is always p>allel to an actual1 or at lea/ a possible1 cry/al face1 & x takes place along ! surfaces ( weak] molecul> cohesion4 ,! degree ( cleavage v>ies f almo/ p]fect1 z 9 mica1 to v poor or none at all1 z 9 qu>tz4 ,! numb] ( cleavage directions exhibit$ by common m9]als is illu/rat$ z foll[s3 mica1 "o2 feldsp>1 two2 calcite1 ?ree2 & fluorite1 f\r4 ,x is a /rik+ fact t :5 a cry/al or cleavage piece is plac$ 9 a solv5t1 ! action proce$s ) diff]5t velocities 9 cry/allographically diff]5t directions & little pits or cavities1 call$ et*+ figures1 are develop$ on "s or all ( ! faces4 ,s9ce ! symmetry ( ^! et*+ figures & _! arrangem5t ^u ! faces are directly relat$ to1 & natural effects ( ! cry/al symmetry1 ! figures (t5 furni% an important me?od ( plac+ a d\btful cry/al or ev5 m]ely a cleavage fragm5t 9 its prop] symmetry class4 ,ano!r m>vel\s prop]ty ( cry/als & cry/all9e sub/ances is _! effect ^u light4 ,s9ce ! /udy ( ! passage ( light ?r\gh cry/als has really become a l>ge sep>ate bran* ( m9]alogical /udy1 we c no m ?an /ate a few fundam5tal facts & pr9ciples 9 ! %ort space at our disposal4 ,light is caus$ by vibrations ( ! s-call$ e!r1 & always travels 9 /raight l9es4 ,! vibration directions are at "r angles to ! direction ( transmission ( ! light4 ,:5 a ray ( light ent]s a cry/al or cry/all9e m9]al repres5t+ any cry/al sy/em except ! isometric x is d\bly refract$ 7i4e41 brok5 into two rays71 ea* ( ! two rays is pol>iz$ 7i4e41 made to vibrate 9 a s+le plane only71 & "o ray vibrates almo/ at "r angles to ! o!r4 ,d\ble refraction is /rik+ly %[n by plac+ a piece ( cle> calcite 7,icel& sp>7 ov] a dot on pap] :5 two dots in/ead ( "o are visible4 ,! am\nt ( d\ble refraction v>ies ) ! sub/ance1 & 9 "s degree accord+ to ! direction ( passage ( light ?r\gh a cry/al4 ,isometric cry/als only are s+ly refract+ & h5ce a ray ( light is n affect$ 9 pass+ ?r\gh !m4 ,cry/als ( all ! o!r six sy/ems d\bly refract & pol>ize light & 9 ?ree sy/ems--tetragonal1 hexagonal1 & trigonal--"o direction 7co9cid5t ) ! ma9 axis ( symmetry7 produces s+le refraction only1 :ile 9 ! rema9+ ?ree sy/ems--or?orhombic1 monocl9ic1 & tricl9ic--!re are always two directions ( s+le refraction ^: positions v>y ) ! sub/ance4 ,_m cry/als outside ! isometric sy/em also exhibit a rem>kable t5d5cy to absorb light diff]5tly 9 diff]5t cry/allographic directions1 ?us produc+ two or ?ree color t9ts1 :i* v>y accord+ to ! sub/ance4 ,aft] ga9+ a practical k ( ! above & _m o!r optical prop]ties ( cry/als1 x is possible by ! aid ( a specially con/ruct$ 7pol>iz+7 microscope1 to recognize 7) few exceptions7 ea* "o ( ! _m m9]al species4 ,?is me?od is ( great value 9 det]m9+ ! v>i\s m9]als :i* are aggregat$ 9 ! =m ( a rock1 9 :i* case a v ?9 slice ( ! rock is /udi$ ) ! microscope4 ,an important crit]ion = ! recognition ( m9]als is h>dness1 by :i* is meant ! resi/ance ( a smoo? surface to abrasion or scrat*+4 ,! g5]ally adopt$ scale ( h>dness foll[s3 #a4--,s(t1 greasy feel1 & easily scrat*$ by ! f+] nail 7e4g41 talc74 #b4--;,j scrat*$ by ! f+] nail 7e4g41 gypsum74 #c4--;,j scrat*$ by a copp] co9 7e4g41 calcite74 #d4--;,easily cut by a knife1 b does n cut glass 7e4g41 fluorite74 #e4--;,j scrat*es s(t glass1 & is cut by a knife 7e4g41 apatite74 #f4--;,h>d] ?an /eel1 & scrat*es glass easily 7e4g41 or?oclase74 #g1 #h1 #i1 & #aj4--;,h>d] ?an any ord9>y sub/ance & repres5t$ 9 ord] by qu>tz1 topaz1 corundum1 & diamond4 ,illu/ration3 ,plate #ag4--,skeleton ( ! ,great ,two-,legg$1 ,c>nivor\s ,d9osaur ,reptile1 ,call$ ,tyrannosaurus1 ,:i* ,liv$ ,dur+ ,cretace\s ,"t4 7,c\rtesy ,am]ican ,museum ( ,natural ,hi/ory47 ,small ,picture4--,re/oration ( ! ,e>lie/ ,kn[n ,bird ( ,:i* ,sev]al ,ne>ly ,p]fect ,skeletons ,h ,be5 ,f\nd4 ,?is fea!r$ creature ) reptilian *>act]i/ics liv$ at lea/ #e1jjj1jjj ye>s ago4 ,x _h a long v]tebrat$ tail1 claws on ! ends ( ! w+s1 & tee?4 7,by ,e4 ,w4 ,b]ry47 ,plate #ah4--7;a7 ,skeleton ( ! ,l>ge/ ,kn[n ,creature ,t ,ev] ,flew4 ,x 0 a fly+ reptile ) spread w+s ( ne>ly tw5ty-five feet1 & liv$ dur+ ! ,cretace\s p]iod sev]al million ye>s ago4 7,c\rtesy ( ! ,am]ican ,museum ( ,natural ,hi/ory47 ,plate #ah4--7;b7 ,skeleton ( a ,rem>kable ,swimm+ ,reptile ( ! ,mesozoic ,era4 ,l5g? ab\t twelve feet4 ,p>ts ( skeletons ( unborn "y are se54 7,c\rtesy ( ! ,am]ican ,museum ( ,natural ,hi/ory47 ,m9]als also %[ a great v>iety ( colors4 ,_m ( !m l qu>tz & calcite are colorless or :ite1 o!rs l gal5a 7/eel-gray7 & pyrite 7brass-yell[7 %[ inh]5tly *>act]i/ic colors1 :ile /ill o!rs l ame?y/ 7purple7 & sapphire 7blue7 are color$ by impurities4 ,!re is also a great range 9 relative weights or d5sity ( m9]als1 commonly call$ ! specific gravity1 :i* range f less ?an "o = ice to #ba4e = plat9um1 & ev5 some:at high]4 ,! av]age specific gravity ( all m9]als ( ! e>? is ab\t #b4f4 ,9 ! light ( ! above discussion ( ! g5]al prop]ties ( m9]als1 we %all n[ proce$ to "n & briefly describe "s ( ! m9]als :i* are ei!r v common1 or ( special int]e/1 or ( special economic importance4 ,only ^? features are li/$ by :i* ! m9]al species may be recogniz$ at sight1 or by ! aid ( v simple non*emical te/s4 ,illu/ration3 ,fig4 #gd4--;,draw+s %[+ =ms ( cry/als ( common m9]als3 a & b1 g>net 7,isometric72 c & d1 feldsp>s 7,monocl9ic72 e1 f1 & g1 qu>tz 7,trigonal72 h1 i1 & j1 calcite 7,hexagonal72 k1 augite 7,monocl9ic72 l4 hornbl5de 7,monocl9ic72 m1 pyrite 7,isometric74 ,amphibole4 ,a numb] ( species closely relat$ 9 composition1 cry/al =m1 & prop]ties are "h includ$4 ,!y are silicates ( lime & magnesia usually ) alum9um & iron4 ,mo/ common by f> are ^? :i* cry/allize 9 ! monocl9ic sy/em ) prismatic faces & two good prismatic cleavages meet+ at ab\t #bd degrees4 ,color1 commonly br[n to black1 b sometimes gre5 or :ite4 ,h>dness v>ies f #e to #f1 & specific gravity f #c to #c4d4 ,hornbl5de1 ! mo/ common species1 is a d>k color$ silicate ( lime1 magnesia1 alum9um1 & iron4 ,x is "o ( ! few mo/ common ( all m9]al species1 especially 9 igne\s & metamorphic rocks4 ,tremolite is a :ite to light gray silicate ( lime & magnesia f\nd especially 9 metamorphic lime/ones4 ,act9olite is a gre5 silicate ( lime1 magnesia1 & iron especially common 9 c]ta9 metamorphic rocks4 ,"o k9d ( jade is an amphibole simil> to tremolite & act9olite 9 composition1 :ile ! o!r k9d is a pyrox5e 7see bel[74 ,jade is & has be5 highly priz$ 9 ! ea/ 7especially 9 ,*9a7 :]e x has be5 c>v$ into _m objects ( exceptional v>iety & beauty4 ,jade is probably ! t\ghe/ 7n h>de/7 ( all m9]als because ( its wond]ful microscopically fibr\s /ructure4 ,9 color x is :ite1 gray1 & gre54 ,apatite4 ,cry/allizes 9 ! hexagonal sy/em ) a six-sid$ prism usually capp$ at ea* end by a six-sid$ pyramid 7see ,figure #ge;g74 ,composition1 a phosphate ( lime4 ,color v>iable1 b mo/ly :ite1 gre51 or br[n4 ,h>dness ( #e1 or j en\gh to scrat* s(t glass4 ,specific gravity1 #c4b4 ,no good cleavage4 ,t9y cry/als are widely dissem9at$ ?r\gh _m common rocks--igne\s1 metamorphic1 & s$im5t>y4 ,9 c]ta9 metamorphic lime/ones excell5t cry/als a foot or m 9 l5g? h be5 f\nd4 ,apatite1 mo/ly 9 uncry/alliz$ =m1 is ! s\rce ( mo/ ( our phosphate f]tiliz]s4 ,azurite4 ,an azure-blue hydr\s c>bonate ( copp] :i* cry/allizes commonly 9 small monocl9ic cry/als4 ,h>dness1 ne>ly #d1 & specific gravity1 ne>ly #d4 ,commonly occurs 9 ve9s deposit$ by und]gr\nd wat]4 ,"o ( ! great ores ( copp]1 especially 9 ,arizona1 ,*ile1 & ,au/ralia4 ,b>ite4 ,a sulphate ( b>ium cry/alliz+ 9 or?orhombic prisms usually ( tabul> habit4 ,:ite to light color %ades4 ,h>dness1 #c4e2 specific gravity1 #d4e1 :i* is notably high] ?an ! av]age ( light-color$ m9]als4 ,?ree good cleavages p>allel to pr9cipal cry/al faces4 ,a common & widely di/ribut$ m9]al1 especially 9 _m ve9 deposits associat$ ) c]ta9 ores4 ,us$ 9 gr\nd =m to give weight to c]ta9 k9ds ( pap] & clo?1 & a b>ium comp\nd us$ = ref9+ sug> is made f x4 ,illu/ration3 ,fig4 #ge4--;,cry/al =ms cf common m9]als3 a1 gal5a 7,isometric72 b1 sphal]ite 7,isometric72 c1 b]yl 7,hexagonal72 d1 hematite 7,hexagonal72 e1 magnetite 7,isometric72 f1 b>ite 7,or?orhombic72 g1 apatite 7,hexagonal72 h4 sulphur 7,monocl9ic72 i1 gypsum 7,monocl9ic72 j1 *alcopyrite 7,tetragonal72 k1 fluorite 7,isometric72 l1 zircon 7,tetragonal72 m1 t\rmal9e 7,trigonal72 n1 corundum 7,hexagonal74 ,b]yl4 ,a silicate ( alum9um & ! r>e *emical elem5t b]yllium4 ,hexagonal cry/als usually ( v simple six-sid$ prismatic habit 7see ,figure #ge;c74 ,color :ite1 gre51 blue1 or yell[4 ,specific gravity1 #b4h4 ,cleavage practically abs5t4 ,x is a v exceptionally h>d m9]al1 be+ #h 9 ! scale4 ,v l>ge cry/als h be5 f\nd1 z1 = example1 9 ,new ,hamp%ire1 :]e s+le cry/als sev]al feet long weigh a ton or m4 ,b]yl is also ( special int]e/ because two ( its v>ieties--em]ald 7gre57 & aquam>9e 7blue7--are well-kn[n gem /ones1 ! em]ald be+ "o ( ! mo/ highly priz$ gems4 ,! colors are due to slight impurities4 ,b]yl mo/ commonly occurs 9 dikes ( co>se granite call$ pegmatite1 b also 9 c]ta9 metamorphic & s$im5t>y rocks4 ,calcite4 ,commonly call$ calc sp>4 ,a c>bonate ( lime4 ,hexagonal cry/als 9 a great v>iety ( =ms1 b all ) cry/al faces arrang$ 9 sixes ar\nd ! pr9cipal or v]tical axis =m+ rhomboh$rons1 prisms1 or d\ble-po9t$ pyramids4 ,! pr9cipal axis ( symmetry is sixfold by a comb9ation ( rotation & reflection4 ,v p]fect cleavages 9 ?ree directions yield+ fragm5ts ^: faces make angles ( #ge & #aje degrees4 ,color1 :ite :5 pure1 b v>i\sly color$ :5 impure4 ,h>dness1 #c 7v easily scrat*$ by a knife72 specific gravity1 #b4g4 ,calcite is a v common m9]al1 especially 9 lime/one 7includ+ *alk7 & m>ble :i* are usually l>gely made up ( x4 ,also commonly f\nd 9 ve9s1 & z spr+ & cave deposits 7/alactites74 ,a por\s1 /r+y v>iety1 call$ trav]t9e1 is deposit$ by c]ta9 hot spr+s1 z at ,mammo? ,hot ,spr+s 9 ,yell[/one ,p>k4 ,a v transp>5t cry/all9e v>iety is call$ ,icel& sp>4 ,calcite is a v useful m9]al4 ,lime/one & m>ble are widely us$ z a build+ /one1 & = decorative purposes1 /atu>y1 etc4 ,lime/one is burn$ = quicklime1 us$ z a flux 9 smelt+ c]ta9 ores1 9 glass mak+1 etc4 ,cassit]ite4 ,! "o great ore ( t9 ^: composition is oxide ( t94 ,tetragonal cry/allization 7,figure #gc;c74 ,h>dness great] ?an /eel1 be+ ov] #f 9 ! scale4 ,specific gravity #g1 :i* is notably high4 ,color1 br[n to ne>ly black4 ,cleavage1 practically abs5t4 ,fairly widespread 9 small am\nts1 & 9 comm]cial quantities 9 only a few localities1 usually 9 ve9s 9 granite or metamorphic rocks ne> granite1 z at ,cornwall1 ,engl&1 also 9 ! =m ( r\nd$ masses 9 gravel deposition z 9 ! ,malay region4 ,*alcocite4 ,cry/allizes 9 ! or?orhombic sy/em1 usually 9 tabul> =m1 b cry/als n common4 ,a black sulphide ( copp] ) metallic lu/]4 ,h>dness1 ne>ly #c2 specific gravity1 ne>ly #f4 ,no cleavage4 ,*alcocite occurs 9 ve9 deposits z "o ( ! important copp] ores1 especially at ,butte1 ,montana4 ,*alcopyrite4 ,kn[n z copp] pyrites1 7,figure #ge;j74 ,a deep brass-yell[ sulphide ( iron & copp]4 ,seldom cry/alliz$ 9 tetragonal =ms4 ,h>dness1 #c4e2 specific gravity1 ov] #d4 ,no cleavage4 ,metallic lu/]4 ,widely di/ribut$ 9 ve9 deposits associat$ ) o!r metal-be>+ m9]als4 ,a v important ore ( copp]1 especially at ,rio ,t9to1 ,spa94 ,*lorite4 ,a s(t1 gre5 m9]al1 usually 9 small tabul> cry/als1 9 g5]al appe>ance mu* l mica 7see bel[71 b unlike mica1 ! almo/ p]fect cleavage leaves are n ela/ic1 ?\gh !y are flexible4 ,composition1 a silicate ( alum9um & magnesia4 ,always ( second>y orig9 z a result ( *emical alt]ation ( c]ta9 o!r m9]als1 su* z biotite-mica1 pyrox5e or amphibole4 ,c9nab>4 ,a v]milion-r$ sulphide ( m]cury4 ,an extra s(t metallic m9]al1 only #b4e 9 ! scale4 ,specific gravity ov] #h1 :i* is notably high4 ,completely vaporizes on be+ heat$4 ,small trigonal cry/als r>e4 ,c9nab> is ! "o great ore ( m]cury1 occurr+ 9 ve9s1 especially 9 ,cali=nia & ,spa94 ,copp]4 ,copp] z su* 7s-call$ native copp]7 is widely di/ribut$ 9 ve9s1 usually 9 small am\nts ) o!r copp] m9]als1 b 9 ! great m9es ( nor!rn ,mi*igan x occurs 9 imm5se quantities z ! only important ore4 ,x is readily recogniz$ by its color1 s(tness 7less ?an #c71 & notable weight 7specific gravity1 ne>ly #i74 ,isometric cry/als uncommon4 ,corundum4 ,an oxide ( alum9um ( hexagonal cry/allization1 usually 9 six-sid$ prisms1 capp$ by v /eep pyramidal faces 7see ,figure #gen74 ,x is next to ! h>de/ ( all kn[n m9]als 7#i 9 ! scale71 ! diamond only exce$+ x4 ,specific gravity ab\t #d4 ,?ree good cleavages mak+ angles ( ne>ly #ij degrees ) ea* o!r4 ,! color ( corundum is usually br[n1 b x v>ies greatly4 ,two ( ! mo/ highly priz$ ( all preci\s /ones--ruby 7r$7 & sapphire 7blue7--are ne>ly transp>5t v>ieties ( corundum1 color$ by c]ta9 impurities4 ,ori5tal topaz 7yell[71 ori5tal em]ald 7gre571 & ori5tal ame?y/ 7purple7 are also cle> v>ieties ( corundum4 ,x occurs 9 v>i\s igne\s & metamorphic rocks1 & 9 "s /ream gravels4 ,! f9e/ rubies1 associat$ ) "s sapphires1 occur 9 gravels 9 ,burma1 ,siam1 & ,ceylon4 ,em]y is a f9e-gra9$ mixture ( corundum & o!r m9]als1 especially magnetite4 ,diamond4 ,?is m9]al is rem>kable n only because x is ! k+ ( preci\s /ones1 b also because x is easily ! h>de/ kn[n sub/ance 7#aj 9 ! scale74 ,specific gravity1 #c4e4 ,v brilliant lu/]4 ,cry/als ( usually octah$ral habit 9 ! isometric sy/em4 ,usually colorless1 b (t5 v>i\sly t9t$4 ,composition1 pure c>bon4 ,burns completely away at high temp]ature4 ,! greate/ m9es 9 ! _w are 9 ,s\? ,africa1 :]e ! diamonds occur 9 masses ( r s(t 7decompos$7 igne\s rock1 evid5tly hav+ cry/alliz$ dur+ ! cool+ ( ! molt5 masses4 ,9 ,brazil & ,india diamonds are f\nd 9 /ream gravels4 ,feldsp> ,gr\p4 ,! feldsp>s are by f> ! mo/ abundant ( all m9]als 9 ! cru/ ( ! e>?4 7,figures #gd;c1 #gd;d47 ,!re are sev]al important species or v>ieties ( feldsp> ) c]ta9 features 9 common z foll[s3 cry/al =ms1 ei!r monocl9ic or tricl9ic 7closely resembl+ monocl9ic71 9 prismatic =ms ^: faces usually meet at or ne> #ij or #abj degrees2 two good cleavages at or ne> #ij degrees1 h>dness at or ne> #f2 specific gravity1 a little ov] #b4e2 color1 usually :ite1 gray1 or p9k2 & composition1 silicate ( alum9um ) pota%1 soda1 or lime4 ,! two pota% feldsp>s are or?oclase & microcl9e1 ! =m] be+ monocl9ic1 ) cleavages at exactly #ij degrees1 & ! latt] tricl9ic1 ) cleavages a little less ?an #ij degrees4 ,a k9d ( gre5 microcl9e is kn[n z ,amazon /one4 ,! soda-lime feldsp>s g by ! g5]al "n plagioclase4 ,!y are tricl9ic1 ) cleavages meet+ at approximately #hf degrees4 ,v commonly "o ( ! cleavage faces exhibits *>act]i/ic1 well def9$ /riations or f9e p>allel l9es caus$ by multiple tw9n+ dur+ cry/al gr[?4 ,"s ( ! common plagioclases are albite1 a :ite soda feldsp>1 includ+ mo/ s-call$ moon/one2 oligoclase1 a usually gre5i%-:ite to r$di%-gray soda-lime feldsp> includ+ sun/one2 & labradorite1 a lime-soda feldsp>1 usually gray to gre5i%-gray ) a beautiful play ( colors4 ,! feldsp>s occur 9 all ?ree great gr\ps ( rocks1 b !y h mo/ commonly cry/alliz$ dur+ ! cool+ ( molt5 masses ( igne\s rocks4 ,:]e _m s$im5t>y rocks h und]gone great *ange 7metamorphism7 "u conditions ( heat1 pressure1 & moi/ure1 feldsp>s h v commonly =m$4 ,or?oclase & microcl9e feldsp> are us$ 9 ! manufacture ( porcela9 & *9aw>e4 ,"s special v>ieties ( feldsp> are cut or poli%$ = semipreci\s /ones or decorative purposes4 ,fluorite4 ,a common m9]al ^: composition is fluoride ( lime4 7,figure #gc;b47 ,isometric cry/als1 usually cubes ) edges modifi$1 are common4 ,tw9n$ cubes are also common4 ,easily scrat*$ by a knife 7h>dness1 #d71 & specific gravity a little ov] #c4 ,cle> & colorless :5 pure1 b v>i\sly color$1 especially gre51 blue1 yell[1 & br[n1 due to impurities 9 solution dur+ cry/allization4 ,rem>kable because ( its f\r good cleavages meet+ at su* angles z to p]mit good cleavage octah$rons to be brok5 out ( cry/als4 ,fluorite is widely di/ribut$1 mo/ commonly 9 ve9 deposits1 (t5 associat$ ) metallic ores4 ,occurs also z cry/als 9 "s lime/ones & igne\s rocks4 ,"s fissure ve9s ( fluorite 9 lime/one 9 s\!rn ,ill9ois are tw5ty to =ty feet wide4 ,us$ mo/ly z a flux 9 ! manufacture ( c]ta9 /eel1 9 glass mak+1 & 9 mak+ enamel w>e4 ,gal5a4 ,commonly z isometric cry/als ei!r z cubes or comb9ations ( cubes & octah$rons4 ,composition1 sulphide ( lead4 7,figure #ge;a47 ,color1 lead-gray ) metallic lu/]4 ,h>dness1 #b4e2 specific gravity high1 #g4e4 ,v brittle4 ,?ree excell5t cleavages at "r angles & p>allel to ! cry/al faces ( ! cube4 ,ne>ly all ( ! lead ( comm]ce comes f ! smelt+ ( gal5a4 ,x is m9$ 9 _m p>ts ( ! _w :]e x ne>ly always occurs 9 typical ve9 deposits (t5 associat$ ) sphal]ite 7see bel[74 ,g>net ,gr\p4 ,! memb]s ( ?is v int]e/+ m9]al gr\p v commonly occur 9 isometric cry/alliz$ =ms1 mo/ly twelve & tw5ty-f\r fac$ figures or bo? comb9$1 z %[n by ,figure #gb4 ,all ! six species ( g>nets are silicates1 mo/ly ( alum9um usually ) ei!r lime1 magnesia1 or iron4 ,cleavage1 v imp]fect or abs5t4 ,h>dness great1 #f4e to #g4e1 & specific gravity #c4a to #d4c1 v>y+ accord+ to species4 ,color also v>ies ) composition1 b mo/ commonly r$1 br[n1 & m r>ely yell[1 black1 & gre54 ,g>nets are mo/ common z cry/als emb$d$ 9 metamorphic rocks1 especially highly alt]$ /rata4 ,also occurs 9 _m igne\s rocks & 9 "s s&s4 ,commonly us$ z a semipreci\s /one1 & also gr\nd = use z an abrasive1 especially 9 mak+ a k9d ( s& 7or g>net7 pap]4 ,gold4 ,gold z su* 7native gold7 is1 9 small am\nts1 really a v widely di/ribut$ m9]al4 ,x is *>act]iz$ by its yell[ color1 s(tness 7less ?an #c 9 ! scale71 great weight 7specific gravity1 ov] #ai71 & extreme malleability4 ,mo/ ( ! comm]cial gold occurs 9 riv] gravels 7s-call$ plac] deposits71 & 9 ve9s associat$ ) ! v common m9]al qu>tz4 ,graphite4 ,commonly call$ black lead1 b x is n lead at all4 ,its composition is pure c>bon--! same z t ( ! diamond4 ,we "h h a v rem>kable example ( a s+le sub/ance 7c>bon7 :i*1 accord+ to circum/ances1 cry/allizes 9 two di/9ctly diff]5t sy/ems 7diamond 9 isometric1 & graphite 9 hexagonal7 yield+ v ?91 flexible flakes2 greasy 9 feel2 & easily rubs (f on pap]4 ,x weighs less ?an ! av]age m9]al 7specific gravity1 a little ov] #b74 ,good cry/als ( hexagonal tabul> =m are r>e4 ,! mo/ natural home ( graphite is 9 ! metamorphic rocks1 especially c]ta9 ( ! highly alt]$ /rata1 :]e x occurs 9 ! =m ( m or less abundant flakes1 hav+ orig9at$ f organic matt]4 ,"s also occurs 9 igne\s rocks & 9 ve9s4 ,l>ge quantities are made at ,niag>a ,falls f an?racite by electricity4 ,gypsum4 ,monocl9ic cry/als common1 usually ( simple =ms1 z %[n by ,figure #ge;i4 ,sometimes tw9 cry/als4 ,composition1 sulphate ( lime4 ,colorless or :ite :5 pure4 ,c be scrat*$ by ! f+] nail 7h>dness1 #b74 ,specific gravity1 #b4c4 ,?ree good cleavages1 especially ! prismatic1 yield+ cleavage plates ) angles ( #ff & #aad degrees4 ,?9 cleavage lay]s1 mod]ately flexible4 ,!re are sev]al v>ieties3 7#a7 sel5ite1 :i* is cle>1 cry/all9e2 7#b7 sat9 sp>1 fibr\s ) silky lu/]2 7#c7 alaba/]1 f9e-gra9$ & compact cry/all9e2 & 7#d7 rock gypsum1 massive granul> or e>?y4 ,gypsum is common & widespread especially among /ratifi$ rocks (t5 z ?ick b$s :i* h mo/ly result$ f evaporation ( bodies ( wat] conta9+ x 9 solution1 & (t5 associat$ ) salt b$s4 ,also occurs z scatt]+ cry/als 9 %ales & clays1 & 9 "s ve9s4 ,9 greate/ quantities x is burn$ to make pla/] ( ,p>is4 ,sat9 sp> & alaba/] are (t5 cut & poli%$ = ornam5ts1 etc4 7,see ,figure #gc;a47 ,halite4 ,common salt4 ,composition1 *loride ( soda4 ,isometric cry/als1 ne>ly always 9 cubes ) ?ree good cleavages at "r angles1 & p>allel to ! faces ( ! cube4 ,h>dness1 #b4e2 specific gravity1 #b4e4 ,colorless to :ite :5 pure4 ,*>act]i/ic salty ta/e4 ,abundant & widespread1 (t5 z ext5sive /rata 9 rocks ( ne>ly all ages1 hav+ result$ f evaporation ( inl& bodies ( salt wat]4 ,also 9 va/ quantities 9 solution 9 salt lakes & ! sea4 ,halite has _m uses1 z = example1 cook+ & pres]vative purposes1 indirectly 9 glass mak+ & soap mak+1 glaz+ pott]y1 & 9 _m ore-smelt+ & *emical processes4 ,hematite4--,"o ( ! common & important iron oxides ) less iron ?an magnetite & no wat] z has limonite4 ,cry/allizes 9 hexagonal =ms4 ,color1 black1 ) metallic lu/]1 :5 cry/all9e1 o!rwise usually dull r$4 ,h>dness1 ab\t #f2 specific gravity1 ab\t #e4 ,no cleavage4 ,r$ /reak :5 rubb$ on r\gh porcela94 ,hematite is extremely widespread 9 rocks ( all ages1 especially 9 metamorphic & s$im5t>y rocks4 ,"s occurs z cry/als 9 igne\s rocks1 & "s 9 ve9 deposits4 ,x is ! greate/ ore ( iron 9 ! ,unit$ ,/ates1 especially 9 ,m9nesota1 ,mi*igan1 ,wiscons91 & ,alabama4 ,kaol94 ,commonly call$ ,*9a clay4 ,composition1 a hydr\s silicate ( alum9um4 ,cry/allizes 9 scalelike monocl9ic =ms1 b usually =ms compact claylike masses4 ,h>dness1 a little ov] #b2 specific gravity1 #b4f4 ,color :5 pure1 :ite4 ,usually feels smoo? & pla/ic4 ,v abundant & widespread1 especially =m+ ! ma9 body ( clay & ( mu* %ale4 ,always ( second>y orig91 g5]ally result+ f ! decomposition ( feldsp>4 ,x is ! ma9 con/itu5t ( *9aw>e1 pott]y1 porcela91 tiles1 bricks1 etc4 ,limonite4 ,an important oxide ( iron 9 composition l hematite except = its v>iable wat] cont5t4 ,nev] cry/alliz$4 ,h>dness1 ab\t #e2 specific gravity1 ne>ly #d4 ,color1 light to d>k br[n to ne>ly black4 ,leaves a *>act]i/ic yell[i%-br[n /reak :5 rubb$ on r\gh porcela94 ,exce$+ly common & widely di/ribut$1 always z a m9]al ( second>y orig9 z a product ( wea!r+ ( v>i\s iron-be>+ m9]als4 ,:]e accumulat$ 9 consid]able deposits x is an iron ore ( "s importance4 ,magnetite4 ,"o ( ! ?ree important oxides ( iron conta9+ no wat]1 & ri*] 9 iron ?an hematite4 7,see ,figure #ge;e47 ,commonly cry/allizes 9 isometric octah$ral =ms alone or comb9$ ) twelve-fac$ =ms4 ,h>dness1 #f2 specific gravity1 #e4 ,color1 black ) metallic lu/]4 ,leaves black /reaks on r\gh porcela94 ,*>act]i/ically highly magnetic4 ,wide-spread z cry/als 9 ne>ly all k9ds ( igne\s rocks1 & z l>ge segregation masses 9 c]ta9 igne\s rocks4 ,also v common 9 metamorphic rocks1 9 _m cases =m+ l5ses & b$s z ore deposits4 ,occurs 9 "s /rata & s&s4 ,x is an important ore ( iron4 ,mala*ite4 ,a light-gre5 hydr\s c>bonate ( copp]4 ,9 almo/ e way1 except diff]5ce 9 color & slight diff]5ce 9 composition1 x is v mu* l azurite 7see above74 ,mica ,gr\p4 ,! micas rank high 9 abundance among ! mo/ common m9]als ( ! e>?4 ,all ( ! sev]al species are silicates ( alum9um comb9$ ) o!r *emical elem5ts accord+ to ! species4 ,all cry/allize 9 monocl9ic six-sid$ prisms ^: angles are ne>ly #abj degrees4 ,^! prisms closely approa* true hexagonal =ms4 ,all are *>act]iz$ by "o exce$+ly good cleavage at "r angles to ! prismatic faces1 yield+ v ?9 ela/ic cleavage %eets4 ,h>dness1 #b to #b4e2 specific gravity1 #b4g to #c4 ,! v>i\s species or v>ieties are n always %>ply sep>at$ f ea* o!r4 ,mo/ common are3 muscovite1 or s-call$ is+lass1 a pota% mica :i* is colorless & transp>5t 9 ?9 %eets :5 pure2 biotite1 an iron-magnesia mica1 black to d>k gre52 & phlogopite1 a br[n magnesia mica4 ,oliv9e4 ,(t5 call$ *rysolite4 ,a silicate ( iron & magnesia4 ,or?orhombic cry/als1 usually 9 /\t prismatic =m4 ,color1 usually yell[i% gre54 ,h>dness1 ne>ly #g2 specific gravity1 #c4c4 ,transp>5t to transluc5t4 ,no real cleavage4 ,its h>dness1 color1 & cry/al =m g5]ally *>act]ize x4 ,x is a fairly common m9]al f\nd ma9ly z cry/all9e gra9s 9 c]ta9 d>k-color$ igne\s rocks4 ,a cle> gre5 v>iety1 call$ p]idot1 is us$ z a gem /one4 ,opal4 ,an oxide ( silicon1 l qu>tz 9 composition except t x is comb9$ ) a v>y+ am\nt ( wat]4 ,x nev] cry/allizes1 probably because ( its r indef9ite composition4 ,h>dness #e4e to #f4e 7s(t] ?an qu>tz72 specific gravity1 ab\t #b4 ,v>ieties v>i\sly color$4 ,common opal1 usually transluc5t ) greasy lu/]4 ,preci\s opal1 transluc5t ) beautiful play ( colors1 us$ z a gem4 ,fire opal1 ) bright r$ to orange int]nal reflections4 ,hyalite1 colorless & transp>5t 9 small r\nd$ masses4 ,wood opal1 wood petrifi$ by opal4 ,geys]ite1 a :ite1 por\s1 /r+y v>iety deposit$ by c]ta9 hot spr+s l ! ,yell[/one geys]s4 ,tripolite1 f9e-gra9$1 *alklike 9 appe>ance1 consi/+ ( t9y silice\s %ells ( v simple plants call$ diatoms4 ,plat9um4 ,?is m9]al occurs z an impure native metal1 usually alloy$ ) c]ta9 o!r metals4 ,native plat9um1 h>dness1 #d4e 7exceptionally high = a metal72 specific gravity z usually alloy$1 #ad to #ai4 ,pure plat9um1 specific gravity1 ov] #ba1 or "o ( ! v heavie/ kn[n sub/ances4 ,color1 light /eel-gray1 ) metallic lu/]4 ,v malleable & ductile4 ,a r>e metal f\nd comm]cially mo/ly 9 gravel or plac] deposits mo/ly 9 ! ,ural ,m\nta9s1 also z gra9s 9 c]ta9 d>k igne\s rocks4 ,us$ = _m sci5tific in/rum5ts1 9 ! electrical indu/ry1 z jewelry1 etc4 ,pyrite4 ,commonly call$ iron pyrites4 ,sometimes call$ fool's gold4 7,see ,figure #gdm47 ,a sulphide ( iron :i* commonly cry/allizes 9 ! isometric sy/em mo/ly z cubes1 twelve-fac$ pyritoh$rons1 octah$rons1 or comb9ations ( ^!4 ,color1 light brass-yell[1 ) metallic lu/]4 ,cleavage1 practically abs5t4 ,h>dness1 great] ?an t ( /eel 7ov] #f 9 ! scale72 specific gravity1 ab\t #e4 ,leaves gre5i% black /reak :5 rubb$ on r\gh porcela94 ,diff]s f *alcopyrite by pal] color & mu* great] h>dness4 ,x is a common & v widely dissem9at$ m9]al 9 rocks ( all k9ds & ages1 b especially 9 metamorphic rocks z ve9s1 & b&$ or l5slike deposits4 ,mo/ igne\s rocks conta9 small scatt]+ gra9s ( pyrite4 ,_m deposits ( comm]cial value are kn[n4 ,great quantities are burn$ = ! manufacture ( sulphuric acid 7oil ( vitriol7 :i* is "o ( ! mo/ important ( all *emicals4 ,pyrox5e ,gr\p4 ,along ) qu>tz & feldsp>s1 ! pyrox5es rank among ! mo/ common ( all m9]als4 7,see ,figure #gdk47 ,composition1 v simil> to amphibole 7see above74 ,pyrox5es cry/alliz+ 9 ! monocl9ic sy/em are ! mo/ important4 ,^! cry/als are prismatic 9 habit1 ) prism faces mak+ angles ( ne>ly #de or #ij degrees in/ead ( ab\t #abd degrees z 9 ! monocl9ic amphiboles :i* ! monocl9ic pyrox5es greatly resemble4 ,two fairly good prismatic cleavages cross at an angle ( ne>ly #ij degrees1 in/ead ( at ab\t #abd degrees z 9 ! monocl9ic amphiboles4 ,h>dness1 #e to #f2 specific gravity1 #c4b to #c4f4 ,color1 v>iable accord+ to species4 ,! mo/ common v>iety ( pyrox5e is augite1 a d>k-gre5 to black silicate ( alum9um1 iron1 lime1 & magnesia4 ,c]ta9 pyrox5es also cry/allize 9 ! or?orhombic sy/em4 ,pyrox5e is mo/ abundantly repres5t$ z cry/als 9 _m k9ds ( igne\s & metamorphic rocks4 ,x is practically useless except z "o k9d ( jade4 ,qu>tz4 ,next to ! feldsp>s1 qu>tz is probably ! mo/ common ( all m9]als1 especially at & ne> ! e>?'s surface4 7,see ,figures #gd;e1 #gd;f1 & #gd;g47 ,composition1 oxide ( silicon4 ,(t5 cry/allizes 9 ! trigonal sy/em almo/ always z six-sid$ prisms capp$ by six-sid$ pyramids1 :i* are really comb9$ ?ree-sid$ =ms1 (t5 ) alt]nate corn]s modifi$ by small faces4 ,^! small modify+ faces1 et*+ figures1 & microscopic te/s %[ t qu>tz is really trigonal 9 spite ( ! common occurr5ce ( simple six-sid$ outw>d =ms4 ,! pyramidal faces make diff]5t angles ?an ^? ( ei!r apatite or b]yl1 bo? ( :i* are some:at l qu>tz 9 cry/al =m4 ,h>dness1 #g 7di/9ctly high1 _c be scrat*$ by ! knife72 specific gravity1 #b4f 7ab\t av]age = all m9]als74 ,cleavage1 practically abs5t1 & breaks l glass4 ,colorless :5 pure1 b v>ieties exhibit _m colors4 ,a few only ( ! _m v>ieties w be briefly describ$4 ,among ! di/9ctly cry/all9e v>ieties are3 rock cry/al1 pure colorless2 ame?y/1 purple2 rose qu>tz1 p9k2 milky qu>tz1 :ite2 & smoky qu>tz1 d>k--due to t9y inclusions ( c>bon4 ,among ! f9e-gra9$1 compact m or less indi/9ctly cry/all9e or noncry/all9e v>ieties1 usually transluc5t ) a waxy lu/]1 are3 *alc$ony1 blui% gray1 waxy look+1 usually 9 small r\nd$ masses2 c>nelian1 r$2 prase1 gre52 agate1 ) p>allel b&s1 usually v>i\sly color$2 fl9t & jasp]1 opaque to transluc5t1 d>k to r$4 ,qu>tz is exce$+ly abundant 9 all ! great gr\ps ( rocks4 ,x con/itutes ! ma9 bulk ( s&/ones1 is common 9 %ales1 & occurs 9 c]ta9 o!r /rata4 ,9 _m igne\s rocks1 l granite1 x is a v prom95t con/itu5t4 ,mo/ ( ! metamorphic rocks conta9 its cry/all9e =ms 9 great] or less am\nts4 ,qu>tz is ! mo/ common ( all ve9 m9]als1 9 _m cases associat$ ) valuable ores4 ,v>i\s v>ieties are widely us$ = ornam5tal purposes4 ,us$ 9 mak+ s&pap]1 glass1 porcela91 mort>1 concrete1 & 9 c]ta9 ore-smelt+ processes4 ,s&/one is widely us$ z a build+ /one4 ,s]p5t9e4 ,a hydr\s silicate ( magnesia nev] 9 di/9ct cry/als z su*1 b %[n to be monocl9ic "u ! microscope4 ,h>dness v>iable1 #b4e to #e2 specific gravity1 ab\t #b4f4 ,mo/ly ( v>iegat$ gre5 or yell[i% gre5 color ) waxy lu/]1 except a fibr\s v>iety 7asbe/os7 :i* is light gre5 to :ite4 ,! fibr\s v>iety ( s]p5t9e is ! pr9cipal s\rce ( asbe/os1 an amphibole asbe/os be+ less common4 ,ord9>y s]p5t9e 7sometimes miscall$ gre5 m>ble7 is widely us$ z a build+ & decorative /one4 ,s]p5t9e is common & widespread1 especially 9 igne\s & metamorphic rocks1 b nev] z a really orig9al m9]al4 ,x always results f alt]ation ( c]ta9 o!r magnesia-be>+ silicate m9]als1 su* z pyrox5e1 amphibole1 oliv9e1 etc4 ,silv]4 ,native silv] is n a v r>e m9]al & x is m9$ 9 c]ta9 p>ts ( ! _w1 b mo/ ( ! metal is obta9$ f c]ta9 silv]-be>+ m9]als1 especially sulphides & a *loride4 ,silv] cry/allizes r r>ely 9 ! isometric sy/em4 ,m commonly x occurs z irregul> masses1 plates1 & wirelike =ms4 ,*>act]iz$ by its color1 metallic lu/]1 s(tness 7less ?an #c 9 ! scale71 & exceptional weight 7specific gravity1 #aj4e74 ,usually occurs 9 ve9 deposits1 commonly associat$ ) o!r metals or metal-be>+ m9]als1 especially copp]4 ,sphal]ite4 ,a sulphide ( z9c commonly 9 cry/all9e =m belong+ 9 ! isometric sy/em1 especially 9 tetrah$ral comb9ation =ms 7see ,figure #ge;b74 ,color1 usually br[n1 yell[ or ne>ly black ) res9\s lu/]4 ,h>dness1 ne>ly #d2 specific gravity1 #d4 ,sev]al good cleavages1 yield+ fragm5ts ^: faces meet at #ij & #abj degrees4 ,sphal]ite is a fairly common & widespread m9]al1 occurr+ ne>ly always 9 ve9s 9 mo/ k9ds ( rocks4 ,x is v (t5 associat$ ) o!r ores1 p>ticul>ly ! great ore ( lead 7gal5a74 ,sphal]ite is by f> ! greate/ ore ( z9c4 ,sulphur4 ,native sulphur4 ,cry/allization1 or?orhombic1 usually 9 comb9ation pyramidal =ms4 7,see ,figure #ge;h47 ,*>act]iz$ by yell[ color1 res9\s lu/]1 s(tness 7ab\t #b 9 ! scale71 l[ specific gravity 7ab\t #b71 & v poor cleavages4 ,x has mo/ commonly result$ f alt]ation ( c]ta9 sulphur-be>+ m9]als1 especially gypsum1 ! decomposition ( :i* has yield$ va/ deposits4 ,"s also ( volcanic orig94 ,great quantities are us$ 9 mak+ sulphuric acid1 mat*es1 gunp[d]1 fireworks1 & = vulcaniz+ & blea*+ rubb] goods4 ,talc4 ,(t5 call$ /eatite4 ,monocl9ic cry/als r>e4 ,"o p]fect cleavage1 yield+ v ?91 flexible leaves4 ,v s(t 7h>dness1 #a74 ,feels greasy1 & looks waxy to pe>ly4 ,color1 :ite1 gray1 to light gre54 ,specific gravity1 #b4h4 ,composition1 a hydr\s silicate ( magnesia1 mu* l t ( s]p5t9e4 ,talc is always ( second>y orig91 g5]ally d]iv$ by *emical alt]ation ( v>i\s common m9]als ri* 9 silicate ( magnesia4 ,soap/one is a common v>iety result+ f alt]ation ( :ole rock masses4 ,soap/one has _m practical uses z = wa%tubs1 table tops1 electrical swit*bo>ds1 he>?/ones1 /ove & furnace l9+s1 blackbo>ds1 gas tips1 etc4 ,talc prop] is us$ z a lubricant1 to weight pap]1 9 soap1 z du/less crayon1 talcum p[d]1 etc4 ,topaz4 ,a silicate ( alum9um & fluor9e4 ,or?orhombic cry/als common1 usually prisms capp$ at "o end by pyramid$ faces & abruptly t]m9at$ at ! o!r4 ,colorless :5 pure1 b (t5 v>i\sly color$ due to impurities4 ,v exceptionally h>d 7#h 9 ! scale72 specific gravity1 #c4e4 ,"o good cleavage across ! prism zone2 usually f\nd z cry/als 91 & 9 cavities 91 igne\s rocks4 ,appe>s always to h =m$ f highly heat$ vapors or liquids giv5 (f by cool+ molt5 rock masses4 ,topaz is "o ( ! m highly priz$ ( ! gem /ones4 ,t\rmal9e4 ,composition1 v complex1 b *iefly a silicate ( boron & sev]al metals & semimetals4 ,commonly z cry/als 9 ! trigonal sy/em 9 bo? long & %ort prismatic =ms1 z %[n by ,figure #gem1 ) opposite ends n unlike4 ,extra h>d 7#g 9 ! scale72 specific gravity1 ab\t #c4 ,color1 widely v>i\s1 b br[n & black are mo/ common4 ,practically no cleavage4 ,t\rmal9e probably always orig9at$ z a high temp]ature m9]al1 especially z cry/als 9 granites & relat$ rocks & 9 c]ta9 metamorphic rocks :i* h be5 subject$ to high temp]ature & pressure4 ,c]ta9 transp>5t color$ v>ieties ( t\rmal9e rank high among ! semipreci\s /ones4 ,turquoise4 ,a hydr\s phosphate ( alum9um4 ,massive noncry/all9e1 blue to gre51 waxy lu/]1 mo/ly opaque1 h>dness ( #f1 & specific gravity ( ab\t #b4g4 ,turquoise is a high temp]ature m9]al f\nd 9 ve9s & cavities 9 c]ta9 igne\s rocks4 ,x is a r>e m9]al us$ z a gem /one4 ,zircon4 ,a silicate ( zirconium usually cry/alliz$ 9 ! tetragonal sy/em z simple f\r-sid$ prisms capp$ by f\r-sid$ pyramids4 7,see ,figure #gel47 ,v poor cleavages4 ,color usually br[n4 ,h>dness1 #g4e 7extra high72 specific gravity1 ne>ly #d4g4 ,brilliant lu/]4 ,zircon is v commonly pres5t z scatt]+ cry/als ( v>y+ size 9 mo/ igne\s rocks4 ,also common z cry/als 9 v>i\s metamorphos$ /ratifi$ rocks1 & less common 9 "s s& & gravel deposits4 ,c]ta9 transp>5t v>ieties1 especially ! br[n & p9k ones call$ hyac9?1 are us$ z gem /ones4 ,zircon is also ! s\rce ( oxide ( zirconium us$ 9 mak+ mantles = c]ta9 inc&esc5t lights4 ,,*apt] ,,xxi ,,economic ,,geology ,9 ?is *apt] x is our purpose to briefly consid] geology 9 its direct relations to ! arts & indu/ries4 ,:5 we realize t ! value ( /rictly geologic products tak5 f ! e>? ea* ye> 9 ! ,unit$ ,/ates alone am\nts to billions ( doll>s1 we c bett] appreciate ! practical application ( geological sci5ce4 ,su* products include coal1 petroleum1 natural gas1 _m valuable metal-be>+ m9]als1 & _m nonmetallif]\s m9]als & rocks4 ,9 mo/ cases ^! valuable products ( nature h be5 sl[ly accumulat$ or conc5trat$ at _m times & "u widely v>y+ conditions ?r\gh\t ! millions ( ye>s ( kn[n geological "t4 ,to trace ! ext5t (1 & mo/ advantage\sly remove1 su* deposits = ! use ( man is always inv>iably impossible unless geological k is br\ght to be>4 ,9 _m cases ! problems involv$ are intricate1 & only ! tra9$ geologi/ is able to at all successfully cope ) !m4 ,9 su* cases x is necess>y n only to h a ?or\gh k ( m9]als & rocks z su*1 b also ( _! orig9 & /ructure4 ,mu* ( ! practical application ( geology is c>ri$ out by ! m9+ eng9e] :o %\ld h1 above all1 a ?or\gh k ( ! great pr9ciples ( geology4 ,our plan ( discussion is to consid]1 fir/1 coal1 petroleum1 & natural gas2 !n ! mo/ important metallif]\s deposits ( ores2 & f9ally nonmetallif]\s m9]als & rocks ( exceptional comm]cial importance4 ,und]gr\nd wat]s h already be5 discuss$ f ! practical /&po9t 9 ! *apt] on ,wat]s ,)9 ! ,e>?4 ,c]ta9 m9]als h already be5 suffici5tly consid]$ f ! economic /&po9t 9 ! *apt] on ,m9]alogy4 ,,coal1 ,,petroleum1 ,,& ,,natural ,,gas ,coal4 ,mo/ valuable ( all geological products is coal4 ,al?\gh x is n1 /rictly speak+1 a m9]al1 bo? because ( its organic orig9 & lack ( def9ite *emical composition1 coal is g5]ally class$ among our m9]al res\rces4 ,"s idea ( ! national importance ( coal 9 ! ,unit$ ,/ates may be ga9$ :5 we realize t ! en]gy d]iv$ f a s+le ye>'s output is equival5t to t ( hundr$s ( millions ( m5 work+ full "t ?r\gh ! ye>4 ,! uses ( coal are too well kn[n to ne$ m5tion "h4 ,coal is1 beyond "q1 ( organic 7plant7 orig9 z %[n by its v composition2 p]fect gradations betwe5 plant deposits l peat & true coal2 & ! pres5ce ( microscopic plant rema9s & spores 9 ! coal4 ,an excell5t summ>y ( j :at happ5s dur+ ! transition ( ord9>y vegetable matt] into coal has be5 giv5 by ,d4 ,:ite z foll[s3 ,all coal 0 laid d[n 9 b$s analog\s to ! peat b$s ( to-day4 ,all k9ds ( plants1 especially su* species z 7 adapt$ to ! p>ticul> region :]e ! deposit 0 locat$1 9 :ole or 9 "p w5t into ! deposit4 ,plants are compos$ *iefly ( cellulose & prote9s4 ,! =m]1 compris+ by f> ! l>g] bulk1 con/itute ! framework1 :]eas ! latt] are conc]n$ 9 ! vital functions4 ,) ^! are associat$ _m o!r sub/ances1 among :i* are *iefly />*1 sug>s1 & fats & oils1 con/itut+ res]ve food/uffs2 waxes1 res9 waxes1 res9s1 & high] fats1 p]=m+ ma9ly protective functions4444 ,^! compon5ts diff] widely 9 _! resi/ance to v>i\s ag5cies4 ,^? sub/ances involv$ 9 ! life function & ! support ( ! plant are relatively v /able "u ! conditions impos$ ^u !m4 ,at ! dea? ( ! plants1 gov]n$ by conditions impos$ 9 ! bog1 a p>tial decomposition1 mac]ation1 elim9ation1 & *emical r$uction beg9s1 br\ght ab\t by v>i\s ag5cies1 *iefly organic1 ma9ly fungi at fir/ & bact]ia lat]4 ,! mo/ labile are remov$ fir/1 ! m resi/ant next1 & s on1 z ! conditions require1 leav+ ! mo/ resi/ant beh9d 9 a residue call$ peat4 ,! process ( decomposition1 elim9ation1 & *emical r$uction begun 9 peat1 *iefly by bio*emical means1 is tak5 up & cont9u$ by dynamo*emical means into & ?r\gh ! v>i\s successive lat] /ages1 & results 9 ! v>i\s grades ( coal1 z lignite1 sub-bitum9\s1 & cannel coal1 & an?racite4 ,! pr9cipal *emical elem5ts involv$ 9 ! *anges :i* take place are c>bon1 oxyg51 & hydrog51 z %[n by ! foll[+ analyses ( ab\t av]age samples ( ea* memb] ( ! s-call$ coal s]ies4 ,! coal s]ies ,c>bon ,oxyg5 ,hydrog5 ,nitrog5 ---------------------------------------- -------------------- ,wood 7cellulose7 #ej #dc #f #a ,peat #ei #cc #f #b ,lignite #fi #be #e4e #j4h ,bitum9\s coal #hb #ac #e #j4h ,an?racite coal #ie #b4e #b4e trace ,graphite #ajj 44 44 44 ---------------------------------------- -------------------- ,f ?is table x is se5 t ! oxyg5 relatively dim9i%es :ile ! c>bon relatively increases1 ?\gh1 ( c\rse1 all ?ree elem5ts actually decrease dur+ ! *emical *ange f cellulose to coal4 ,^! ?ree elem5ts disappe> ma9ly 9 ! =m ( gases1 su* z wat] vapor1 m>% gas1 & c>bonic acid gas4 ,! f9al or graphite /age is almo/ rea*$ by ! graphitic an?racite ( ,rhode ,isl&1 :i* is s ne>ly pure c>bon z to be really useless z coal4 ,! conditions "u :i* successive lay]s ( vegetable matt] 7lat] turn$ into coal7 become emb$d$ 9 ! e>?'s cru/ h be5 outl9$ 9 ! *apt] on ! ,evolution ( ,plants4 ,! mo/ p]fect conditions = prolific plant gr[?1 & accumulation z great b$s 9 ! e>?'s cru/1 7 dur+ ! ,p5nsylvanian p]iod ( ! late ,paleozoic era 9 _m p>ts ( ! _w1 b especially 9 ! ,unit$ ,/ates1 ,*9a1 ,great ,brita91 & ,g]many4 ,mo/ ( ! _w's great supply ( coal comes f rocks ( ,p5nsylvanian ,age1 :ile next 9 importance are ,cretace\s rocks1 & "s comes f /rata ( o!r ages lat] ?an ! ,p5nsylvanian1 ev5 z late z ! ,t]ti>y4 ,! ,unit$ ,/ates n only has ! greate/ kn[n coal fields1 b x also produces f> m coal ?an any o!r c\ntry4 ,9 #aiah ! production 0 #fgh1jjj1jjj tons1 ! greate/ 9 our hi/ory1 or en\gh1 if load$ into c>s ( =ty tons capacity1 to fill a tra9 :i* w\ld rea* ar\nd ! e>? at ! equator ab\t six times6 ,equally amaz+ is ! fact t ?is coal 0 ne>ly all consum$ by ?is "o nation6 ,9 #aiai ! production fell to #edd1jjj1jjj tons4 ,is !re real dang] t our supply ( coal w soon run out8 ,h>dly s :5 we consid]1 fir/1 ! fact t probably n m ?an #a p] c5t ( ! readily available coal has ?us f> be5 remov$1 &1 second1 ! high probability t rate ( increase 9 coal production = ! la/ tw5ty ye>s w n cont9ue4 ,9 fact1 dur+ ! la/ two or ?ree ye>s ! production has fall5 (f consid]ably4 ,b ev5 s1 coal1 :i* is our greate/ natural res\rce1 & :i* c nev] be replac$1 %\ld be sci5tifically cons]v$4 ,9 ! case ( ! v re/rict$ an?racite coal fields :at might be call$ a crisis has already be5 rea*$1 because a v consid]able "p ( ! available supply has be5 tak5 out4 ,some?+ l #cej1jjj squ>e miles ( ! ,unit$ ,/ates are und]la9 ) "o or m b$s ( workable coal 7n includ+ lignite7--9 "s areas five to tw5ty or m b$s "o above ! o!r4 ,!re are also ab\t #aej1jjj squ>e miles ( c\ntry und]la9 ) ! m or less imp]fect coal call$ lignite4 ,x has be5 e/imat$ t !re are m ?an a trillion tons ( easily accessible coal1 & ano!r trillion tons accessible ) "s difficulty 9 ! pr9cipal coal fields ( ! ,unit$ ,/ates4 ,! greate/ production ( coal by f> is f ! ,appala*ian ,m\nta9 & ,allegh5y ,plateau di/ricts1 f ! we/]n half ( ,p5nsylvania to ,alabama1 :]e all ! coal is bitum9\s ( ,p5nsylvanian ,age4 ,"h z well z else:]e ! coal b$s are int]/ratifi$ ) v>i\s k9ds ( s$im5t>y rocks1 mo/ commonly ) %ales & s&/ones4 ,9 ! ,appala*ian field ! /rata includ+ coal b$s are m or less fold$ t[>d ! ea/1 :ile !y are ne>ly horizontal t[>d ! we/4 ,! fam\s ,pittsburgh coal b$ is probably ! mo/ ext5sive important s+le coal b$ kn[n4 ,x cov]s an area ( ov] #ab1jjj squ>e miles & is workable1 ) a ?ickness ( five to fifte5 feet1 ov] an area ( #f1jjj squ>e miles ( p>ts ( we/]n ,p5nsylvania1 ,ohio1 & ,we/ ,virg9ia4 ,illu/ration3 ,fig4 #gf4--,map ( ! ,unit$ ,/ates1 %[+ ! pr9cipal coal fields4 ,cross-l9$ areas repres5t lignitic coals4 7,aft] ,u4 ,s4 ,geological ,survey47 ,! greate/ production ( an?racite coal by f> is f c5tral-ea/]n ,p5nsylvania1 :]e /rata ( ,p5nsylvania ,age1 includ+ a numb] ( an?racite b$s1 are mo/ly highly fold$4 ,mo/ rem>kable ( all 9 ?is di/rict is ! s-call$ mammo? b$ ( an?racite1 ne>ly ev]y:]e pres5t1 ) a ?ickness up to z mu* z fifty or sixty feet4 ,less ?an #ejj squ>e miles are !re und]la9 by workable an?racite coal4 ,next to ! greate/ production ( coal 9 ! ,unit$ ,/ates is f ! two l>ge areas 9 ! middle ( ! ,mississippi ,valley4 ,x is all bitum9\s coal1 associat$ ) ne>ly horizontal /rata ( ,p5nsylvanian ,age4 ,! scatt]+ areas ?r\gh ! ,rocky ,m\nta9s yield all types ( coal--an?racite1 bitum9\s1 & lignite4 ,9 "s ( ^! areas ! coal b$s h be5 b little di/urb$ f _! orig9al horizontal position1 b usually !y are m or less fold$ along ) ! inclos+ /rata1 ! cru/al di/urbances affect+ ! coal b$s hav+ tak5 place late 9 ! ,mesozoic era & e>ly 9 ! ,c5ozoic era4 ,practically all ( ^! coals are ( ,cretace\s & ,t]ti>y ,ages1 ! be/ be+ ,cretace\s4 ,v little ( ! ,rocky ,m\nta9 coal is an?racite4 ,on ! ,pacific ,coa/ coal production is relatively v small4 ,! coals are !re bitum9\s to lignitic ( ,t]ti>y ,age1 usually fold$ 9 ) ! /rata4 ,9 ,alaska !re are widely di/ribut$1 relatively small coal fields1 b !y h be5 little develop$4 ,alaskan coals range 9 age f ,p5nsylvanian to ,t]ti>y1 & 9 k9d f an?racite to lignite4 ,petroleum4 ,crude oil or petroleum is an organic sub/ance consi/+ ( a mixture ( hydroc>bons1 t is1 x is made up v l>gely ( ! two *emical elem5ts c>bon & hydrog51 9 r complex & v>iable comb9ations4 ,x is practically c]ta9 t petroleum has be5 d]iv$ by a sort ( sl[ process ( di/illation f organic matt]--animal or vegetable or bo?--9 /ratifi$ rocks )9 ! e>?4 ,_m /rata1 z = example c>bonace\s %ales1 are m or less *>g$ ) d>k-color$ decompos+ organic matt]4 ,! *emical composition itself1 ! k9ds ( rocks ) :i* x is associat$1 & c]ta9 optical 7microscopic7 te/s all po9t to ! organic orig9 ( petroleum4 ,9 s\!rn ,cali=nia at lea/1 c]ta9 ( ! oils h q c]ta9ly be5 d]iv$ f ! v t9y oily plants call$ diatoms :i* fill _m ( ! /rata4 ,illu/ration3 ,fig4 #gg4--,pr(ile & /ructure section %[+ fold+ ( /rata1 ) includ$ coal b$s1 across "o ( ! an?racite coal fields ( ea/]n ,p5nsylvania4 ,l5g? ( section1 a little ov] #b miles4 7,aft] ,u4 ,s4 ,geological ,survey47 ,dur+ ! la/ tw5ty ye>s petroleum has come to be "o ( ! mo/ important & useful natural products4 ,among ! _m sub/ances artificially d]iv$ f petroleum are k]os5e1 gasol9e1 naph?a1 b5z9e1 vasel9e1 & p>aff9e4 ,! ,unit$ ,/ates leads 9 ! production ( petroleum1 :ile s\!rn ,russia & ,mexico are v important produc]s4 ,9 ! ,unit$ ,/ates ! pr9cipal areas und]la9 ) petroleum-be>+ /rata are ! nor!rn ,appala*ian field 7?r\gh we/]n ,p5nsylvania to c5tral ,we/ ,virg9ia72 ! ,ohio-,indiana field 7c5tral ,indiana to nor?we/]n ,ohio72 ! mid-cont95tal field 7s\!a/]n ,kansas & nor!a/]n ,oklahoma72 ! s\!a/]n ,texas-,l\isiana field2 & ! s\?we/]n ,cali=nia field4 ,! total areas und]la9 ) oil total ab\t #aj1jjj squ>e miles4 ,9 ! ,appala*ian1 ,ohio-,indiana1 & mid-cont95tal fields ! /rata c>ry+ oil range 9 age f ,ordovician to ,p5nsylvanian1 & !y are mo/ly b little di/urb$ f _! orig9al horizontal position4 ,! ,texas-,l\isiana oils come ma9ly f ,cretace\s & ,t]ti>y /rata :i* g5tly d[ntilt "u ! ,coa/al ,pla9 t[>d ! ,gulf4 ,9 ,cali=nia ! oil-be>+ /rata are ( ,t]ti>y ,age & g5]ally consid]ably di/urb$ & fold$4 ,"u prop] conditions bel[ ! e>?'s surface ! d]iv$ oil accumulates 9 por\s or fractur$ rocks4 ,!re mu/1 ( c\rse1 be a s\rce f :i* ! petroleum is d]iv$ or di/ill$2 a por\s or fractur$ rock =mation to take x up2 a cap rock or imp]vi\s lay] to hold x 92 & a prop] geologic /ructure to favor accumulation4 ,! mo/ common por\s 7conta9+7 rock is s&/one1 & ! mo/ common cap rock is %ale4 ,oil is r>ely f\nd )\t gas1 & sal9e wat] is likewise (t5 pres5t4 ,if ! conta9+ /rata are horizontal1 ! oil & gas are usually irregul>ly scatt]$1 b if tilt$ or fold$1 & ! b$s por\s ?r\gh\t1 !y appe> to collect at ! highe/ po9t possible4 ,x 0 ! result ( obs]vations along ?is l9e t l$ ,i4 ,c4 ,:ite to develop :at is kn[n z ! anticl9al !ory4 ,accord+ to ?is !ory1 9 fold$ areas ! gas collects at ! summit ( ! fold 7anticl9e71 ) ! oil imm$iately bel[1 on ei!r side1 foll[$ by ! wat]4 ,x is1 ( c\rse1 necess>y t ! oil-be>+ /ratum %all be capp$ by a practically imp]vi\s "o4 ,illu/ration3 ,fig4 #gh4--,map %[+ ! pr9cipal petroleum & natural gas fields ( ! ,unit$ ,/ates4 7,aft] ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,fig4 #gi4--;,a v]tical 7/ructure7 section %[+ a v common type ( oil-be>+ /ructure4 ,9 ?is anticl9e1 wat]1 oil1 & gas arrang$ 9 ord] ( _! specific gravities4 ,removal ( ! gas w\ld all[ ! oil & wat] to rise high] t[>d ! apex ( ! por\s lay]4 7,aft] ,indiana ,geological ,survey47 ,illu/ration3 ,plate #ai4--;,g5]al ,view 9 ! ,appala*ian ,m\nta9s ,along ,new ,riv]1 ,virg9ia4 ,?is is a typical portion ( ! great area :i*1 dur+ ,mesozoic "t1 0 r$uc$ by erosion to ! condition ( a l[-ly+ pla9 7p5epla974 ,s9ce e>ly ,c5ozoic "t ! p5epla9 has be5 uprais$ & ,new ,riv] has c>v$ out its ,v-%ap$ valley to its pres5t dep?1 :ile tribut>y /reams h c>v$ out a s]ies ( valleys along belts ( weak rocks ne>ly at "r angles to ! ma9 valley4 ,! rem>kably ev5 sky l9e m>ks approximately ! old p5epla9 surface4 7,photo by ,hill]s1 ,u4 ,s4 ,geological ,survey47 ,illu/ration3 ,plate #bj4--7;a7 ,a ,big ,glacial ,b[ld] ( ,plutonic ,igne\s ,rock ,c>ri$ ,miles f ,its ,p>5t ,l$ge by ! ,ice ,%eet ,:i* ,pass$ ,ov] ! ,adirondack ,m\nta9s ,dur+ ! ,ice ,age4 7,photo by ! au?or47 ,illu/ration3 ,plate #bj4--7;b7 ,a ,long1 ,w9d+ ,ridge ( ,s& & ,gravel 7,call$ an ,esk]7 ,deposit$ by a ,/ream 9 a ,*annel 9 ! ,ice ,ne> ! ,m>g9 ( ! ,great ,glaci] ,dur+ ,its ,retreat f ! ,adirondack ,m\nta9s4 7,photo by ! au?or47 ,if ! rocks are dry1 !n ! *ief po9ts ( accumulation ( ! oil w be at or ne> ! bottom ( ! syncl9e 7d[nfold71 or l[e/ portion ( ! por\s b$4 ,if ! rocks are p>tially saturat$ ) wat]1 !n ! oil accumulates at ! upp] level ( saturation4 ,9 a tilt$ b$1 :i* is locally por\s1 & n s ?r\gh\t1 ! oil1 gas1 & wat] may arrange !mselves accord+ to _! gravity 9 ?is por\s "p4 7,ries47 ,al?\gh ! t]m oil pool is commonly us$1 !re is really no actual pool or und]gr\nd lake ( oil1 b r por\s rock saturat$ ) oil4 ,x has be5 e/imat$ t 9 an oil field ( av]age productiv5ess a cubic foot ( ! por\s rock conta9s f six to twelve p9ts ( oil4 ,! life ( a well drill$ into an oil pool v>ies f a few mon?s to tw5ty or ?irty ye>s1 or sometimes ev5 m1 b a heavy produc] 7especially a gu%]7 almo/ inv>iably falls (f v notably 9 production 9 a few mon?s1 or at mo/ a few ye>s4 ,! typical ,p5nsylvanian oil well is said to la/ ab\t sev5 ye>s4 ,! fact t ! ,unit$ ,/ates is /ill able to increase oil output is because new fields are f\nd & develop$1 ! mo/ rec5t be+ 9 ! int]ior & nor!rn p>ts ( ,texas4 ,x is practically c]ta91 h[ev]1 t ! climax ( oil production 9 ! ,unit$ ,/ates w be rea*$ be=e _m ye>s--long be=e t ( bitum9\s coal4 ,x is a well-kn[n fact t oil1 z well z natural gas1 is usually "u m or less pressure )9 ! e>?4 ,! pressure is s great 9 "s cases t :]e1 9 ! c\rse ( drill+1 oil or gas accumulat$ "u prop] conditions1 z = example ^? %[n by ,figure #gi1 are enc\nt]$ ! pressure may be hundr$s ( p\nds p] squ>e in*1 or en\gh to bl[ to pieces mu* ( ! drill+ outfit4 ,x is "u su* conditions t great gu%]s are /ruck4 ,a wond]ful case 9 po9t 0 ! fam\s ,lakeview gu%]1 /ruck 9 ,cali=nia 9 #aiaj4 ,)9 a few days ! well 0 f> beyond control4 ,x cont9u$ to fl[ 7= a "t %oot+ high into ! air7 = eighte5 mon?s1 f9ally /opp+ aft] x _h produc$ ov] #h1jjj1jjj b>rels ( oil1 ab\t #f1jjj1jjj ( :i* _h be5 sav$4 ,! daily production ( ! well v>i$ greatly1 rea*+ a maximum ( #fe1jjj b>rels4 7,pack47 ,"o v common cause ( oil pressure is ! expansive =ce ( ! associat$ imprison$ gas :i* /eadily increases z ! gas is g5]at$4 ,ano!r cause :i* is seem+ly applicable 9 _m cases is hydro/atic pressure1 :]e "u c]ta9 /ructural conditions ! pressure ( wat] 9 a long-tilt$ lay] is ex]t$ aga9/ oil accumulat$ t[>d ! top ( an anticl9e 7or upb5d7 9 ! /rata4 ,! _w's output ( petroleum = #aiag 0 ne>ly #eei1jjj1jjj b>rels1 ( :i* ! ,unit$ ,/ates produc$ ne>ly #cch1jjj1jjj b>rels1 ,mexico #hg1jjj1jjj b>rels1 & ,russia #cd1jjj1jjj b>rels ( #db gallons4 ,natural ,gas4 ,! mo/ p]fect fuel ) :i* nature has provid$ u is natural gas4 ,n only is x easily transport$ ev5 long di/ances ?r\gh pipes1 b also z a fuel x is easily regulat$1 leaves no refuse1 & is less damag+ to boil]s ?an coal4 ,x is a colorless1 odorless1 free-burn+ gas1 consi/+ v l>gely ( ! simple hydroc>bon call$ m>% gas or fire damp4 ,petroleum ne>ly always has m or less natural gas associat$ ) x1 b 9 "s cases consid]able quantities ( gas may exi/ alone4 ,natural gas1 l petroleum1 is ( organic orig9--a product ( sl[ natural di/illation ( vegetable or animal matt]1 or bo?1 )9 ! e>?'s cru/4 ,"o ( ! mo/ common modes ( occurr5ce ( gas is at ! top ( an anticl9e 7upfold7 9 por\s rock 7l s&/one7 betwe5 imp]vi\s lay]s 7l %ale74 ,figure #gi well illu/rates ! pr9ciple1 ! gas ly+ above ! oil1 & ! oil above ! wat]2 t is1 ! ?ree sub/ances are arrang$ accord+ to specific gravity4 ,gas may also exi/ 9 consid]able quantities 9 irregul> bodies ( por\s or fractur$ rocks4 ,natural gas is ne>ly always "u pressure )9 ! e>?1 hundr$s ( p\nds p] squ>e in* be+ common1 :ile m exceptionally1 z 9 c]ta9 ,we/ ,virg9ia wells1 pressures ( ov] #a1jjj p\nds h be5 regi/]$4 ,! ,unit$ ,/ates is by f> ! greate/ _w produc] ( natural gas1 ! output = #aiah hav+ be5 #gbj1jjj1jjj1jjj cubic feet4 ,we/ ,virg9ia easily head$ ! li/1 ) ,oklahoma & ,p5nsylvania next 9 ord]4 ,areas und]la9 ) natural gas are1 9 ! ma91 ! same z = petroleum1 & !y total m ?an #aj1jjj squ>e miles4 ,dur+ ! la/ =ty ye>s ! wa/e ( natural gas 9 ! ,unit$ ,/ates has be5 appall+4 ,9 _m cases wells 9 que/ ( oil h enc\nt]$ gas & (t5 su* ab&on$ wells h be5 all[$ to play millions ( cubic feet ( gas daily into ! air = ye>s4 ,a /rik+ example 0 ! ,murraysville well ( we/]n ,p5nsylvania1 :i* %ot #bj1jjj1jjj cubic feet ( gas p] day into ! air = six ye>s6 ,,metal-,,be>+ 7,,ore7 ,,deposits ,iron4 ,)\t "q ! mo/ useful ( all metals is iron4 ,z su* x is r>e 9 nature1 b 9 *emical comb9ation ) o!r sub/ances x is extremely widespread & v common4 ,iron makes up ab\t #e p] c5t ( ! weight ( ! e>?'s cru/1 b 9 ! =m ( ore 7i4e41 a metal-be>+ m9]al or rock ( suffici5t value to be m9$7 x is notably re/rict$ 9 occurr5ce4 ,! ?ree great ores ( iron are ! m9]als hematite1 magnetite1 & limonite1 ^: composition & *>act]i/ic prop]ties ! read] w f9d /at$ 9 ! prec$+ *apt] on ,m9]alogy4 ,"o ( ! wor/ impurities 9 iron ore is phosphorus1 :i* makes iron cold %ort1 i4e41 brittle :5 cold4 ,ore = ! manufacture ( ,bessem] /eel mu/ conta9 v little phosphorus 7less ?an #a_/ajjj ( ! metallic iron cont5t ( ! ore74 ,sulphur z an impurity 9 ! ore t5ds to make ! iron hot %ort4 ,silica 7qu>tz7 is bad because x necessitates ! use ( m lime = flux 9 ! furnace4 ,iron ores occur 9 rocks ( mo/ ( ! great geologic ages1 b 9 ! ,unit$ ,/ates pr9cipally 9 ! pre-,paleozoic & ,paleozoic4 ,! ,unit$ ,/ates is by f> ! greate/ produc] ( iron ore 9 ! _w1 ! output = #aiag hav+ be5 ab\t #ge1bhh1jjj tons1 ! greate/ 9 ! hi/ory ( ?is or any o!r c\ntry4 ,?is "o ye>'s output load$ into c>s ( #dj tons capacity w\ld h made a tra9 ab\t #ae1jjj miles long6 ,all b ab\t #e1jjj1jjj tons ( ?is trem5d\s production 0 hematite ore4 ,9 #aiai ! output ( iron ore dropp$ to ab\t #fj1jjj1jjj tons4 ,illu/ration3 ,fig4 #hj4--;,draw+ %[+ details ( "p ( an ore-be>+ ve9 at ,p9os ,altos1 ,new ,mexico4 ,! *alcopyrite & sphal]ite are ! ores4 ,some:at r$uc$ 9 size4 7,aft] ,paige1 ,u4 ,s4 ,geological ,survey47 ,we %all n[ v briefly consid] sev]al ( ! greate/ iron-m9+ di/ricts ( ! ,unit$ ,/ates1 giv+ "s idea ( ! modes ( occurr5ce & orig9 ( ! ores4 ,greate/ ( all is ! ,lake ,sup]ior region1 n f> we/ & s\? ( ! lake 9 ,m9nesota1 ,mi*igan1 & ,wiscons94 ,consid]ably m ?an "o-half ! iron ore m9$ 9 ! ,unit$ ,/ates comes f ! s+le ,/ate ( ,m9nesota1 & ab\t "o-f\r? ( x f ,mi*igan4 ,mo/ ( ! ,m9nesota ore by f> is obta9$ f ! s-call$ ,mesaba ,range1 :i* 9 #aiag produc$ #da1jjj1jjj tons ( hematite ore4 ,! ore deposits are !re ( irregul> %ape1 ly+ at or ne> ! surface 7usually cov]$ only by glacial deposits74 ,none ( !m ext5d d[nw>d m ?an a few hundr$ feet4 ,! s(t1 high-grade ore is remov$ by /eam %ovels 9 great op5 pits4 ,9 ! sev]al di/ricts ( nor!rn ,mi*igan & ,wiscons9 ! ores 7ne>ly all hematite7 are associat$ ) m or less highly fold$ rocks at consid]able dep?s4 ,! ,lake ,sup]ior iron ores all occur 9 rocks ( ,ar*eozoic & ,prot]ozoic ,ages4 ,accord+ to ! be/ explanation ( _! orig9 ! iron ( ! ores 0 once "p ( a s$im5t>y s]ies ( rocks 9 ! =m ( iron c>bonate & silicate1 int]/ratifi$ ) lay]s ( a fl9tlike rock associat$ ) slate1 qu>tzite1 etc4 ,aft] ^! rocks 7 rais$ into l& & subject$ to wea!r+ ! old iron comp\nds 7 alt]$ to oxides1 ma9ly hematite1 & some:at conc5trat$4 ,fur!r conc5tration ( ! ore 0 caus$ by dissolv+ out ! fl9tlike lay]s ( ! old rocks4 ,! ,birm+ham1 ,ala41 region is ! second mo/ important iron ore produc] 9 ! ,unit$ ,/ates1 ) an output ( ne>ly #f1jjj1jjj tons 9 #aiah4 ,! ore is hematite1 =m+ "p ( ! fam\s ,cl9ton iron ore deposits ( ,silurian ,age4 ,?is deposit1 nam$ f ,cl9ton1 ,n4 ,y41 ext5ds ?r\gh c5tral ,new ,york & 9 m or less int]rupt$ p>allel b&s ?r\gh ! ,appala*ian ,m\nta9s to ne> ,birm+ham :]e ! ri*e/ deposits occur4 ,?is ore appe>s to be an orig9al b$ 7or locally sev]al b$s7 ( fairly ri* iron ore deposit$ on ! %all[ ,silurian sea bottom & !n cov]$ by o!r /rata4 ,at ! "t ( ! ,appala*ian ,m\nta9 revolution ! iron ore 0 m or less highly fold$ 9 ) o!r /rata ?r\gh\t ! ,appala*ians4 ,a rem>kable fact reg>d+ ! ,birm+ham di/rict is t 9 ! ne> vic9ity ( ! ore !re are bo? coal = fuel & lime/one flux = smelt+ ! ores4 ,! next mo/ important m9+ region ( ! ,unit$ ,/ates is ! ,adirondack ,m\nta9 region ( nor!rn ,new ,york1 :]e ab\t #a1jjj1jjj tons ( ore are obta9$ ye>ly4 ,magnetite is ! ore1 & x occurs 9 m or less irregul> l5ses & b&s 9 granite & closely associat$ rocks ( pre-,paleozoic ,age4 ,"o view reg>d+ ! orig9 ( ?is ore is t x segregat$ dur+ ! process ( cool+ ( ! molt5 granite1 & ano!r view 7rec5tly advocat$ by ! au?or7 is t x 0 d]iv$ f an old] iron-ri* igne\s =mation by ei!r ! molt5 granite or v hot solutions f x & conc5trat$ into ! ores4 ,ab\t #b1ejj1jjj tons ( magnetite 7 m9$ 9 ! ,unit$ ,/ates 9 #aiaf1 ne>ly "o-half ( x 9 ! ,adirondacks4 ,! ?ird important iron ore is limonite1 ne>ly #b1jjj1jjj tons ( :i* 7 produc$ 9 ! ,unit$ ,/ates 9 #aiaf4 ,mo/ ( x came f ! ,appala*ian ,m\nta9s4 ,all ( ?is limonite is ( second>y orig92 t is1 x has be5 d]iv$ f c]ta9 e>ly ,paleozoic iron-be>+ lime/ones ei!r by wea!r+ or solution1 & conc5trat$ into ore deposits4 ,copp]4 ,?is is "o ( ! mo/ useful ( all metals4 ,sev]al ( its v important uses are z a conductor ( electricity 9 ! =m ( wire2 9 mak+ alloys su* z brass & bronze2 9 copp]plate engrav+2 & 9 ro(+ & plumb+4 ,v>i\s m9]als conta9+ copp] are f\nd 9 _m p>ts ( ! _w1 b only ab\t six ( !m are really important z ores4 ,^! are native copp]1 *alcopyrite1 *alcocite1 azurite1 mala*ite1 & cuprite1 mo/ ( :i* are describ$ 9 ! *apt] on ,m9]alogy4 ,! numb] ( places :]e !y may be pr(itably m9$ z ore is di/9ctly limit$4 ,fifte5 or tw5ty c\ntries produce m or less copp]1 b ! ,unit$ ,/ates is by f> ! greate/ produc]1 ) an output ( ne>ly #b1jjj1jjj1jjj p\nds ( copp] 9 #aiaf1 ! output hav+ fall5 (f "s 9 #aiah4 ,?is 0 two-?irds ( ! _w's output & t5 times z mu* z ! ne>e/ competitor4 ,! o!r lead+ c\ntries are ,japan1 ,*ile1 ,mexico1 ,spa91 & ,canada4 ,9 #aiah ! f\r lead+ ,/ates 9 ord] 7 ,arizona1 ,montana1 ,mi*igan1 & ,utah1 ) production rang+ f ne>ly #gfe1jjj1jjj p\nds to ab\t #bcj1jjj1jjj p\nds4 ,9 ,arizona sev]al great copp]-m9+ di/ricts lie 9 ! s\!a/]n "o-f\r? ( ! ,/ate4 ,almo/ inv>iably ! ores are directly associat$ ) lime/one & an igne\s rock 7granite71 bo? ( late ,paleozoic ,age4 ,! ores are almo/ always ne> ! bord] betwe5 ! two rocks1 mo/ly z great irregul> deposits )9 ! lime/one1 & less commonly z ve9s )9 ! granite4 ,! orig9al ores 7 c>ri$ 9 solution & deposit$ by hot liquids 7or vapors7 f ! cool+ granite4 ,at l[] levels ! ores are ma9ly sulphides ( copp] 7e4g41 *alcopyrite & *alcocite71 :ile at high] levels !y are mo/ly c>bonates 7mala*ite & azurite7 & oxides 7e4g4 cuprite74 ,! diff]5ce is due to ! fact t ! ores ne>] ! surface h be5 subject$ to wea!r+ & alt]$ f _! orig9al condition4 ,! region ar\nd ,butte1 ,mont41 is next to ! greate/ copp] produc]4 ,ne>ly all ! ores are sulphides ( copp] 7ma9ly *alcocite7 :i* occur ) qu>tz 9 a great sy/em ( ne>ly p>allel ve9s 9 granite ( ,t]ti>y ,age4 ,x is suppos$ t 9 ! copp] ve9s ! hot ore-be>+ solutions asc5d$ ! fractures 9 ! granite1 replac+ ! rock by ore1 & result+ 9 an int5se alt]ation ( ! walls4 7,ries47 ,?ird 9 rank among ! copp]-produc+ ,/ates is ,mi*igan1 ! m9es be+ locat$ on ,kewe5aw ,p59sula1 :i* ext5ds into ,lake ,sup]ior4 ,= fully fifty ye>s ?is di/rict has be5 "o ( ! mo/ fam\s & important copp] produc]s 9 ! _w4 ,a unique feature is t ! ore is native copp]1 associat$ ) "s native silv]4 ,! rocks conta9+ ! ore are /eeply tilt$ lava %eets & conglom]ate 7cem5t$ gravel7 /rata ( ,prot]ozoic ,age4 ,op5+s 9 por\s lava & spaces betwe5 ! conglom]ate pebbles h be5 fill$ by metallic copp]1 :i* 0 c>ri$ (f 9 hot solutions f ! cool+ lavas4 ,c]ta9 ( ! m9+ %afts h be5 sunk m ?an #e1jjj feet bel[ ! surface1 ^! be+ next to ! deepe/ 9 ! _w4 ,utah ranks f\r? among ! copp] produc]s1 ! greate/ m9+ di/rict be+ at ,b+ham ,canyon1 s\?we/ ( ,salt ,lake ,city4 ,! rocks are late ,paleozoic /rata1 pi]c$ by a l>ge body ( igne\s rock4 ,"s ( ! sulphide ores 7ma9ly *alcopyrite7 occur 9 ve9s 9 ! igne\s rock & "s 9 l>ge tabul> masses 9 ! adjac5t lime/one4 ,hot solutions f l[] portions ( ! uncool$ igne\s rock c>ri$ ! ore 9 solution into ! lime/one & into cracks 9 ! upp] cool$ igne\s rock4 ,lead4 ,lead mu/ surely be c\nt$ among ! five or six mo/ useful metals4 ,z 9 ! case ( ne>ly all ! o!r mo/ important natural res\rces1 ! ,unit$ ,/ates is ! _w's greate/ produc] ( lead1 ! output ( metallic lead hav+ be5 #eeb1jjj tons 9 #aiaf & some:at less 9 #aiah4 ,mo/ ( ?is came f ,miss\ri1 ,idaho1 ,utah1 & ,colorado4 ,! lead+ o!r c\ntries are 9 ord]--,spa91 ,g]many1 ,mexico1 & ,au/ralia4 ,ne>ly all ! lead comes f ! m9]al gal5a 7a sulphide ( lead71 :i* is describ$ 9 ! *apt] on ,m9]alogy4 ,among ! _m uses ( lead are ! foll[+3 manufacture ( c]ta9 high-grade pa9ts f lead comp\nds2 mak+ alloys su* z pewt]1 type metal1 sold]1 babbit metal2 9 plumb+2 9 glass mak+2 & 9 ! manufacture ( %ot4 ,! greate/ lead-m9+ di/rict is 9 ! vic9ity ( ,jopl91 ,mo41 :]e ! ore 7gal5a71 associat$ ) mu* z9c ore1 occurs z ve9s & great irregul> deposits 9 lime/one ( e>ly ,paleozoic ,age4 ,x is g5]ally agre$ t und]gr\nd wat]s dissolv$ ! ores out ( ! lime/one 9 :i* !y 7 dissem9at$ z t9y p>ticles & deposit$ !m 9 conc5trat$ =m at l[] levels4 ,9 ! fam\s ,coeur d',al5e di/rict ( nor!rn ,idaho ! great output ( lead is really obta9$ f a lead-silv] ore2 t is1 gal5a ri* 9 silv]4 ,?is ore is 9 composition a lead-silv] sulphide4 ,x occurs 9 great fissure ve9s1 mo/ly foll[+ fault fractures 9 highly fold$ /rata ( ,prot]ozoic ,age4 ,igne\s rocks cut ?r\gh ! /rata1 & x is believ$ t hot ore-be>+ solutions giv5 (f f ! highly heat$ igne\s rocks rose 9 ! fissures & deposit$ ! ores4 ,! ,p>k ,city & ,t9tic di/ricts ( ,utah are great produc]s ( lead4 ,! lead ore 7gal5a7 is usually ri* 9 silv]4 ,x occurs ma9ly 9 ve9s & irregul> deposits 9 lime/one ( ,paleozoic ,age closely associat$ ) c]ta9 igne\s rocks4 ,"o ( ! mo/ fam\s m9+ di/ricts 9 ! _w is t ar\nd ,leadville1 ,col41 :]e ores ( f\r metals--gold1 silv]1 lead1 & z9c--h be5 ext5sively m9$4 ,! sali5t po9ts 9 ! r complex geology are ! foll[+3 ,paleozoic /rata1 includ+ mu* lime/one1 re/ ^u a f\ndation ( pre-,paleozoic granite4 ,%eets ( igne\s rock are int]b$d$ ) ! /rata & _m dikes ( igne\s rocks cut ?r\gh ! :ole comb9ation4 ,aft] ! la/ igne\s activity all ! rocks 7 some:at fold$ & notably fault$ 9 _m places4 ,! ores 7 dissolv$ out ( ! igne\s rock & deposit$ 9 l>ge masses mo/ly 9 ! lime/one & 9 fissure ve9s1 especially along & ne> ! fault zones4 ,z9c4 ,ano!r ( ! few mo/ useful metals is z9c4 ,x nev] occurs 9 metallic =m 9 nature1 b mo/ ( x by f> is obta9$ f ! ore m9]al sphal]ite 7sulphide ( z9c7 describ$ 9 ! *apt] on ,m9]alogy4 ,a r$ oxide ( z9c ore1 call$ z9cite1 assumes great economic importance 9 ,new ,j]sey4 ,9 #aiag ! ,unit$ ,/ates produc$ #fhf1jjj tons ( metallic z9c & 0 easily ! _w's lead]4 ,s9ce #aiag ! production has fall5 notably4 ,! f\r greate/ produc+ ,/ates are ,miss\ri1 ,montana1 ,new ,j]sey1 & ,colorado4 ,g]many & ,belgium are ! greate/ =eign produc]s4 ,mo/ important ( all 9 ! ,unit$ ,/ates is ! di/rict ar\nd ,jopl91 ,mo41 :]e ! ore is closely associat$ ) lead ore4 ,! mode ( occurr5ce & orig9 ( ^! ores are above ref]r$ to 9 ! discussion ( lead4 ,9 ,montana "s ( ! great ea/-we/ fissure ve9s 9 granite are ri* 9 silv] ores 9 ! upp] levels1 & 9 z9c ores 7ma9ly sphal]ite7 at dep?s ( f "s hundr$s ( feet to ne>ly #b1jjj feet1 t is z f> d[n z !y h be5 m9$4 ,!y1 l ! great copp] ve9s ( ! same g5]al di/rict1 7 c>ri$ by hot solutions :i* rose f ! l[] /ill v hot granite & deposit$ ! ores 9 fissures ( ! same cool] rock high] up4 ,two great ore bodies 9 ! g5]al vic9ity ( ,frankl91 ,n4 ,j41 are ( unique int]e/1 because !y are mo/ly ! r$ oxide ( z9c call$ z9cite4 ,! ore deposits occur 9 :ite lime/one along or close to its contact ) metamorphos$ 7alt]$7 /rata & granite ( e>ly ,paleozoic ,age4 ,x is n def9itely kn[n h[ ! ore orig9at$1 b x 0 probably d]iv$ 9 solution f ! hot granite & deposit$ 9 ! lime/one by replacem5t ( ! latt]4 ,9 ,colorado ! pr9cipal z9c m9es are ar\nd ,leadville1 :]e lead ore is ne>ly always directly associat$ ) ! z9c ore4 ,?is di/rict is above describ$ 9 ! discussion ( lead4 ,among _m uses ( z9c are = galvaniz+2 = mak+ c]ta9 high-grade pa9ts2 brass & :ite metal2 & = ro(+ & plumb+4 ,gold4 ,?is preci\s metal has be5 us$ & highly priz$ by man = ?\s&s ( ye>s4 ,! discov]y ( gold 9 ,cali=nia 9 #ahdh 0 "o ( ! mo/ important ev5ts 9 ! hi/ory ( ! m9+ _w4 ,z e>ly z #aheb t ,/ate rea*$ its climax ( production ) an output ( at lea/ #ha1jjj1jjj wor? ( ! metal4 ,! ,transvaal region ( ,s\? ,africa has = two decades be5 ! _w's greate/ gold produc]4 ,?\gh long kn[n1 ! metal has !re be5 work$ only s9ce #ahhf4 ,9 #aiae ! peak ( gold production 9 ! _w 7#dfh1gjj1jjj7 0 rea*$ & ne>ly ma9ta9$ 9 #aiaf1 b s9ce t "t !re has be5 a great fall+ (f4 ,9 #aiaf ,s\? ,africa produc$ gold to ! value ( ab\t #bjj1jjj1jjj2 ! ,unit$ ,/ates ov] #ij1jjj1jjj2 ,au/ralia ov] #dj1jjj1jjj2 ,russia ov] #bf1jjj1jjj2 & ,canada ov] #ai1jjj1jjj4 ,9 t9y am\nts gold is really v widespread4 ,x occurs 9 _m /ream gravels :]e s-call$ color may be obta9$ by wa%+ gravel1 & x is ev5 dissolv$ 9 sea wat]4 ,gold-m9+ localities are also num]\s 9 _m p>ts ( ! _w1 b relatively few ( !m only h ev] paid4 ,! total am\nt ( money sp5t 9 actual gold-m9+ op]ations2 9 hopeless b hone/ op]ations2 & = /ock 9 fake gold m9es has no d\bt exce$$ ! actual value ( gold produc$4 ,9 _m a case acceptance ( a report bas$ ^u a v brief exam9ation ( ! gr\nd by a compet5t geologi/ w\ld h sav$ ! co/ ( hopeless exp5diture ( money4 ,"s "o 9 ne>ly e community has a s-call$ gold m9e4 ,mo/ ( ! comm]cially valuable gold occurs 9 nature z native gold1 ei!r mix$ ) gravel & s& 7i4e41 plac] deposits7 along exi/+ or anci5t /ream b$s1 or 9 ve9s me*anically held 9 ! m9]al pyrite 7describ$ 9 ! prec$+ *apt]7 9 submicroscopic =m1 or visibly mix$ ) qu>tz 9 ve9 deposits4 ,ano!r k9d ( ore :i* assumes consid]able importance1 z 9 p>ts ( ,colorado1 is 9 ! =m ( telluride ( gold always f\nd 9 ve9s4 ,9 deep ve9 deposits x is q ! rule to f9d free or native gold me*anically & visibly mix$ ) qu>tz 9 ! upp] levels1 :ile deep] d[n ! gold is me*anically1 b invisibly1 held 9 comb9ation usually 9 pyrite1 :i* latt] is associat$ ) qu>tz4 ,?is diff]5ce is due to ! fact t ! l[] level ores are n[ j z !y 7 =m$1 :ile 9 ! upp] levels ! ores h be5 wea!r$1 & ! gold set free & (t5 m or less fur!r conc5trat$ by solutions4 ,ve9 deposits1 includ+ also telluride ores1 are f\nd 9 _m k9ds ( rocks--igne\s1 s$im5t>y1 & metamorphic--( ne>ly all ages g5]ally directly associat$ ) igne\s rocks4 ,9 ne>ly all cases ! be/ evid5ce indicates t ! ve9 fill+s 7 =m$ by hot ore-be>+ solutions f ! igne\s rock1 :i* solutions deposit$ ! ore plus qu>tz 9 fissures 9 ei!r ! igne\s or adjac5t rocks4 ,among ! _m localities :]e fissure ve9s ( ! k9d j describ$ are ( great economic importance are ! ,"m ,lode belt ( ! ,si]ra ,nevada ,m\nta9s ( ,cali=nia2 ,cripple ,creek 7telluride ore71 ,georget[n & ! ,san ,juan region ( ,colorado2 ,goldfield1 ,tonopah1 & ,com/ock ,lode ( ,nevada2 & ne> ,juneau1 ,alaska4 ,plac] deposits1 t is1 free gold mix$ ) gravel & s&1 also yield mu* gold4 ,!y are mo/ prom95tly develop$ 9 ,cali=nia & ,alaska4 ,^! gold-be>+ gravels repres5t ! m resi/ant products ( wea!r+1 su* z qu>tz & native gold1 :i* h be5 wa%$ d[n f ! hills on ^: slopes ! gold-be>+ qu>tz ve9s outcrop1 & 7 too heavy to be c>ri$ any di/ance1 unless ! grade 0 /eep4 ,!y h consequ5tly settl$ d[n 9 ! /ream *annels1 ! gold1 on acc\nt ( its high] specific gravity1 collect+ usually 9 ! l[] "p ( ! gravel 7plac]7 deposit4 7,ries47 ,su* gold occurs z gra9s1 flakes1 or nuggets4 ,:5 a *unk ( gold-be>+ ve9 qu>tz1 ) crevices fill$ by ?9 plates ( ! metal1 is c>ri$ d[n/ream pieces are gradually brok5 away1 & ! t\gh1 v malleable gold b5ds or welds toge!r into a s+le mass call$ a nugget4 ,nuggets v>y+ 9 weight up to ov] #b1jjj ounces h be5 f\nd4 ,_m plac] deposits are along exi/+ dra9age *annels1 :ile o!rs occur 9 ab&on$ & ev5 buri$ =m] *annels4 ,mo/ ( ! gold ( ,s\? ,africa comes f ,witwat]sr& di/rict :]e ! native metal occurs 9 a unique mann] 9 b$s or lay]s ( conglom]ate associat$ ) o!r /rata1 all ! rocks be+ consid]ably fold$ & some:at fault$4 ,"s ( ! m9es are m ?an a mile deep 7v]tically71 ! deepe/ 9 ! _w4 ,! gold ei!r accumulat$ 9 plac] =m ) gravel :i* lat] consolidat$ into conglom]ate1 or x 0 introduc$ into spaces betwe5 ! pebbles subsequ5tly by ore-be>+ solutions4 ,silv]4 ,= _m ye>s ! ,unit$ ,/ates & ,mexico h be5 ! _w's greate/ silv] produc]s1 sometimes "o & sometimes ! o!r lead+1 ) ,canada ?ird1 & ,au/ralasia f\r?4 ,9 #aiah ! ,unit$ ,/ates produc$ ne>ly #fh1jjj1jjj ounces ( silv] & ,mexico ov] #fb1jjj1jjj ounces4 ,9 ! ,unit$ ,/ates 9 #aiah ! f\r lead+ ,/ates 7 ,montana1 ,utah1 ,idaho & ,nevada ) outputs rang+ f ov] #aj1jjj1jjj to ov] #ae1jjj1jjj ounces ea*4 ,9 ,montana mo/ ( ! silv] is 9 ! native =m1 m especially 9 ! upp] portions ( ! great ve9s ri* 9 copp] & z9c ores ne> ,butte4 ,^! ores & _! orig9 are describ$ above "u ! captions ,copp] & ,z9c4 ,! two greate/ silv] di/ricts ( ,nevada are ,tonopah & ,com/ock ,lode :]e silv] & gold m9]als are associat$ z ores 9 ,t]ti>y igne\s rocks1 ! ores hav+ be5 deposit$ 9 ve9s by hot ore-be>+ solutions f ! igne\s rocks4 ,9 ,idaho ! ,coeur d',al5e di/rict produces mo/ ( ! silv]1 ! ore !re be+ a silv]-be>+ lead ore 7gal5a74 ,! nature & orig9 ( ^! deposits are describ$ above "u ! caption ,lead4 ,9 ,utah ! silv] is also obta9$ f silv]-be>+ gal5a especially 9 ! ,t9tic1 ,cottonwood ,canyon1 & ,b+ham ,canyon di/ricts :]e ! ores occur ma9ly z irregul> deposits & 9 fissure ve9s 9 ,paleozoic /rata 7*iefly lime/one7 directly associat$ ) igne\s rocks1 hot ore-be>+ solutions f ! igne\s rocks hav+ furni%$ ! ores4 ,t94 ,production ( t9 9 ! ,unit$ ,/ates has nev] am\nt$ to mu*1 a little m9+ hav+ be5 c>ri$ on f "t to "t 9 ,s\? ,c>ol9a1 ,black ,hills ( ,s\? ,dakota1 & s\!rn ,cali=nia4 ,ab\t "o-half ( ! _w's supply ( t9 7#aba1jjj long tons #aiah7 comes f ! ,malay ,p59sula & two small isl&s ne> by4 ,! only o!r great produc] is ,bolivia1 ?\gh a numb] ( o!r c\ntries produce f #a1jjj to #i1jjj tons ea*4 ,! only important ore ( t9 is ! m9]al cassit]ite 7oxide ( t97 describ$ above 9 ! *apt] on ,m9]alogy4 ,9 ! ,malay region ! ore all occurs 9 plac] deposits & is1 !re=e1 ( second>y orig91 ! s\rce ( ! ore n be+ kn[n4 ,9 ,bolivia ! t9 ore occurs 9 ve9s 9 & close to granite1 ! ore hav+ be5 c>ri$ by v hot vapors or liquids :i* 7 d]iv$ f ! /ill highly heat$ granite4 ,t9 is us$ *iefly 9 ! mak+ ( t9 plate1 bronze1 pewt]1 gun metal1 & bell metal4 ,alum9um4 ,! m9]al call$ bauxite 7a hydr\s oxide ( alum9um7 is ! great ore f :i* alum9um is obta9$ by an electrical process4 ,bauxite is noncry/all9e1 relatively light 9 weight1 :ite to yell[i% 9 color1 & 9 ! =m ( r\nd$ gra9s1 or e>?y or claylike masses4 ,! ,unit$ ,/ates & ,france are ! only two great produc]s ( bauxite1 mo/ ( :i* is treat$ = metallic alum9um4 ,9 #aiah ! ,unit$ ,/ates produc$ m ?an #ajj1jjj tons ( alum9um4 ,9 ! ,unit$ ,/ates ! pr9cipal deposits are 9 ,georgia1 ,alabama1 & ,arkansas4 ,bauxite is probably always a second>y m9]al =m$ by decomposition ( igne\s rocks ri* 9 c]ta9 alum9um silicate m9]als4 ,9 "s cases1 z 9 ! ,georgia-,alabama region1 ! bauxite appe>s to h be5 =m$ & conc5trat$ 9 deposits by hot solutions f uncool$ igne\s rocks4 ,alum9um is mo/ us$ 9 ! manufacture ( wire = electric curr5t transmission4 ,x is also mix$ ) c]ta9 o!r metals l copp]1 z9c1 magnesium1 & tung/5 to =m special types ( alloys1 "s ( :i* possess rem>kable t5sile /r5g? up to ne>ly #ej1jjj p\nds p] squ>e in*4 ,alum9um is us$ 9 p[d]$ =m to g5]ate v high temp]atures 9 c]ta9 weld+ processes4 ,x is also made into _m k9ds ( ut5sils & in/rum5ts4 ,m]cury4 ,?is metal1 commonly kn[n z quicksilv]1 is ( special int]e/ because x is ! only "o :i* exi/s 9 liquid =m at ord9>y temp]atures4 ,! metal occurs 9 only small quantities 9 nature1 mo/ ( x by f> be+ obta9$ f ! r$ m9]al c9nab> describ$ 9 ! *apt] on ,m9]alogy4 ,9 ord] ( importance ! greate/ quicksilv] produc+ c\ntries 9 #aiaf 7 ,italy1 ,unit$ ,/ates1 ,au/ria1 & ,spa94 ,9 ! ,unit$ ,/ates1 ,cali=nia is by f> ! lead+ ,/ate1 :ile ,texas & ,nevada are ! only o!r important produc]s4 ,9 ,cali=nia mo/ ( ! ore occurs 9 ve9s & irregul> deposits 9 metamorphos$ /rata ( ,mesozoic & ,c5ozoic ages usually closely associat$ ) igne\s rocks4 ,!re1 z well z 9 o!r p>ts ( ! _w1 hot vapors f igne\s rocks c>ri$ ! volatile ore upw>d & deposit$ x 9 fissures4 ,among ! _m uses ( m]cury are 9 mak+ fulm9ate = explosives2 mak+ c]ta9 drugs & *emicals1 pigm5ts1 electrical & physical app>atus2 silv]+ mirrors2 & 9 ! amalgamation process ( extract+ gold & silv]4 ,,o!r ,,economic ,,products ,build+ ,/ones4 ,"s ( ! pr9cipal features :i* %\ld be consid]$ 9 build+ /ones are p[] to resi/ wea!r+1 p[] to )/& heat1 color1 h>dness1 & d5sity1 & cru%+ /r5g?4 ,build+ /ones repres5t+ rocks ( ne>ly all important geologic ages are widely di/ribut$ ?r\gh\t ! _w4 ,granite1 includ+ c]ta9 o!r closely relat$ rocks1 is "o ( ! olde/ & mo/ useful build+ /ones4 ,! ,new ,engl& ,/ates are ! greate/ produc]s1 :ile ! ,pi$mont ,plateau di/rict 7ea/ ( ! ,appala*ians7 f ,philadelphia to ,alabama also conta9s important granite qu>ries4 ,9 ! ,adirondack ,m\nta9s1 9 ,wiscons9 & ,m9nesota1 ?r\gh ! ,rocky ,m\nta9s1 & ! ,si]ra ,nevada ,m\nta9s !re are ext5sive areas ( granite :i* are relatively little qu>ri$4 ,! granite occurs only 9 regions ( highly di/urb$ rocks1 usually 9 m\nta9s or hills1 :]e great volumes ( ! molt5 rock 7 =c$ into ! e>?'s cru/1 cool$1 & lat] laid b>e by erosion4 ,m>ble1 accord+ to geological def9ition1 is a metamorphos$ lime/one1 t is a lime/one :i* has be5 cry/alliz$ "u conditions ( heat1 pressure1 & moi/ure )9 ! e>?4 ,m loosely 9 trade any lime/one :i* takes a poli% may be call$ m>ble4 ,! greate/ m>ble-produc+ di/ricts ( ! ,unit$ ,/ates are we/]n ,new ,engl& 7especially ,v]mont7 & ! ,pi$mont ,plateau & ,appala*ian ,m\nta9s 9 rocks ( ,paleozoic age4 ,9 nor!rn ,new ,york & ! m\nta9s ( ! we/ !re are relatively few m>ble qu>ries4 ,ord9>y lime/ones are widely di/ribut$ 9 _m ,/ates :]e !y range 9 age f e>ly ,paleozoic to ,t]ti>y4 ,mo/ ( ! qu>ries supply /one = ne>-by m>kets4 ,! s-call$ ,b$=d lime/one ( ,indiana has1 = _m ye>s1 be5 p]haps ! mo/ widely us$ lime/one = build+ purposes 9 ! ,unit$ ,/ates4 ,s&/ones1 :i* are /ratifi$ rocks consi/+ ma9ly ( r\nd$ qu>tz gra9s cem5t$ toge!r1 are widely us$ 9 build+ op]ations4 ,l lime/ones1 !y are v widespread 9 =mations ( all ages except ! v old4 ,!re are _m s&/one qu>ries supply+ m or less local m>kets ?r\gh\t ! c\ntry4 ,two ( ! be/ kn[n & mo/ widely us$ s&/ones are ! s-call$ br[n-/one ( ,triassic ,age ext5d+ int]rupt$ly f ! ,connecticut ,valley ( ,massa*usetts to ,nor? ,c>ol9a1 & ! ,b]ea1 ,ohio1 s&/one ( light gray color & uni=m texture4 ,slate is mo/ly a metamorphos$ %ale1 t is a %ale :i* has be5 subject$ to great pressure )9 ! e>? s t ! /ratification has be5 oblit]at$ & a well def9$ cleavage has be5 develop$ at "r angles to ! direction ( application ( ! pressure4 ,good slate is f9e-gra9$1 d5se1 & splits readily into wide ?9 plates4 ,x occurs only :]e m\nta9 mak+ pressure & metamorphism h be5 br\ght to be> ^u ! /rata4 ,mo/ ( our great slate qu>ries are locat$ 9 e>ly ,paleozoic rocks f ,new ,engl& ?r\gh ! ,pi$mont ,plateau4 ,"s qu>ries are also locat$ 9 ,arkansas1 ,m9nesota1 & we/w>d to ,cali=nia4 ,clay4 ,clay1 :i* is "o ( ! mo/ widely di/ribut$ mat]ials & "o ( ! mo/ valuable1 comm]cially1 may be def9$ z a f9e-gra9$ mixture ( ! m9]al kaol9ite ) fragm5ts ( o!r m9]als1 su* z silicates1 oxides1 & hydrates1 & also (t5 organic comp\nds1 ! mass possess+ pla/icity :5 wet & becom+ rock-h>d :5 burn$ to at lea/ a temp]ature ( r$ness4 7,ries47 ,mo/ clays orig9ate by ! wea!r+ ( rocks1 p>ticul>ly igne\s & metamorphic rocks ri* 9 ! m9]al feldsp>4 ,z a result ( ! decomposition ( ! feldsp>1 mu* clay is =m$1 ! ma9 sub/ance ( :i* is kaol94 ,bo? feldsp> & kaol9 are describ$ 9 ! prec$+ *apt]4 ,:5 ! result+ clay re/s ^u ! rock f :i* x has be5 d]iv$ x is call$ residual clay4 ,mu* ( ! clay is1 h[ev]1 c>ri$ away1 ma9ly by /reams1 & deposit$ 9 lakes or ! sea1 or on riv] flood pla9s4 ,"s clay deposits are ( w9d-bl[n orig91 & /ill o!rs are =m$ by ! gr9d+ action ( glaci]s4 ,clays are v widespread1 & !y are directly associat$ ) rocks ( all geologic ages4 ,among ! _m important uses ( clay are ! foll[+3 manufacture ( common brick1 fire brick1 pott]y1 *9aw>e1 porcela9 w>e1 tiles1 t]ra cotta1 & ,portl& cem5t4 ,lime & ,cem5t4 ,lime/one1 :i* is "o ( ! mo/ common & widespread ( all /ratifi$ rocks1 =ms ! basis = ! manufacture ( ! important sub/ances lime 7or quicklime7 & ,portl& cem5t4 ,lime results :5 pure lime/one 7c>bonate ( lime7 is burn$ or heat$ to a temp]ature high en\gh to drive (f ! c>bonic acid gas4 ,! greate/ use ( lime is = mix+ ) wat] & s& to make mort>4 ,a few ( its o!r num]\s uses are 9 pla/]+2 :itewa%+2 purify+ c]ta9 /eel2 9 mak+ gas1 pap]1 & soap2 & z a f]tiliz]4 ,c]ta9 lime/ones conta9+ clay ( ! "r k9d & proportion are call$ natural cem5t rocks because1 aft] be+ burn$1 !y develop ! prop]ty ( sett+1 l cem5t :5 mix$ ) wat]4 ,! sett+ ( a cem5t is due to ! fact t c]ta9 *emical comp\nds =m$ dur+ ! heat+ cry/allize :5 mix$ ) wat]1 & ! h>d1 t9y int]lock+ cry/als ( ! newly =m$ silicate m9]als give rigidity to ! mass4 ,( rec5t ye>s ,portl& cem5t has l>gely sup]s$$ ! natural rock cem5ts4 ,portl& cem5t is ! product obta9$ by burn+ a f9ely gr\nd artificial mixture consi/+ ess5tially ( lime1 silica1 alum9a1 & "s iron oxide1 ^! sub/ances be+ pres5t 9 c]ta9 def9ite proportions4 7,ries47 ,! necess>y +r$i5ts are g5]ally obta9$ by gr9d+ & burn+ c>efully select$ mixtures ( lime/one 9 "s =m1 & clay or %ale4 ,! great & gr[+ uses ( cem5t ne$ n be detail$ "h4 ,salt4 ,mo/ ( ! common salt 7! m9]al halite7 ( comm]cial value occurs 9 nature 9 sea or salt lake wat]2 or 9 b$s or /rata ( rock salt associat$ ) o!r /rata2 or z natural br9e 9 op5+s or pores 9 c]ta9 rocks4 ,consid]able salt is obta9$ by evaporation ( tidewat]1 z ar\nd ,san ,francisco ,bay1 & ( salt lake wat]1 z at ,great ,salt ,lake1 ,utah4 ,x has be5 e/imat$ t ! ,great ,salt ,lake1 ^: area is ab\t #b1jjj squ>e miles & greate/ dep? #ej feet1 conta9s sev]al hundr$ million tons ( common salt4 ,?is salt has be5 wa%$ out ( ! rocks ( ! surr\nd+ c\ntry & gradually accumulat$ 9 ! lake because x has no outlet4 ,mo/ important ( all s\rces ( salt is ! rock salt :i* occurs 9 ! =m ( /rata )9 ! e>?'s cru/4 ,su* /rata are f\nd 9 rocks ( ne>ly all ages f ! e>ly ,paleozoic to ! pres5t4 ,!y result$ f ! evaporation ( salt lakes or salty m or less cut-(f arms ( ! sea1 aft] :i* o!r /rata accumulat$ on top ( !m4 ,?us 9 ! ,silurian sy/em ( /rata und]ly+ all ( s\?we/]n ,new ,york ,/ate !re occur almo/ univ]sally f "o to sev5 b$s ( salt4 ,! /rata includ+ ! salt dip g5tly s\?w>d s t at ,i?aca1 ,new ,york1 sev5 salt b$s 7 /ruck 9 a well at a dep? ( ab\t #b1bjj feet4 ,nor?w>d ! salt comes ne>] & ne>] ! surface4 ,"o well p5etrat$ a lay] ( solid salt #cbe feet ?ick4 ,"s ( ?is salt is be+ m9$ mu* l coal1 b mo/ ( x is obta9$ by runn+ wat] into deep wells to dissolve ! salt1 ! result+ br9e be+ pump$ out & evaporat$4 ,"u portions ( s\!rn ,mi*igan !re are bo? salt b$s & natural br9es *>g+ c]ta9 por\s rock lay]s4 ,bo? ! salt b$s 7( ,silurian ,age7 & ! br9es 7( ,mississippian ,age7 supply great quantities ( salt f br9es pump$ out & evaporat$4 ,9 #aiah ! ,unit$ ,/ates produc$ #ea1jjj1jjj b>rels 7#bhj lbs4 ea*7 ( salt4 ,mi*igan 7#ag1jjj1jjj b>rels7 & ,new ,york 7 ! lead+ ,/ates1 foll[$ by ,kansas1 ,ohio1 ,we/ ,virg9ia1 & ,cali=nia4 ,"s ( ! uses ( common salt are giv5 9 ! description ( halite 9 ! prec$+ *apt]4 ,gypsum4 ,! composition & prop]ties ( ?is common & useful m9]al are giv5 9 ! *apt] on ,m9]alogy4 ,rock gypsum is ! v>iety ( great comm]cial importance4 ,x is widespread1 be+ qu>ri$ 9 _m ,/ates1 & occurs int]/ratifi$ ) rocks ( _m ages :]e x has orig9at$ by evaporation or p>tial evaporation ( salt wat] lakes or m or less cut-(f arms ( ! sea4 ,salt b$s are (t5 associat$ ) gypsum4 ,= ab\t t5 ye>s ! av]age ye>ly production ( gypsum 9 ! ,unit$ ,/ates has be5 approximately #b1ejj1jjj tons1 or ab\t t5 times t ( ! ne>e/ =eign competitor 7,canada74 ,new ,york1 ,i[a1 ,mi*igan1 & ,ohio are ! *ief produc]s4 ,9 ,new ,york ! rock gypsum 7usually f\r to t5 feet ?ick7 lies betwe5 %ale & lime/one /rata ( ,silurian age1 & x is qu>ri$ f ! c5tral to ! we/]n "p ( ! ,/ate4 ,9 ,mi*igan ! rock gypsum b$s1 commonly five to tw5ty feet ?ick1 lie 9 ,mississippian /rata 9 ! s\!rn portion ( ! ,/ate4 ,a great b$ ( exceptionally pure rock gypsum und]lies ab\t tw5ty-five squ>e miles ( ,web/] ,c\nty1 ,i[a1 9 rocks ( late ,paleozoic ,age4 ,! ,kansas gypsum deposits ext5d across ! c5tral "p ( ! ,/ate 9 rocks ( ,p]mian ,age4 ,rock gypsum is ma9ly us$ 9 mak+ pla/] ( ,p>is1 z a ret>d] 9 cem5t1 & z a f]tiliz] 7s-call$ l& pla/]74 ,,gloss>y ,,( ,,common ,,geological ,,t]ms ,names ( subk+doms & important classes ( fossil plants & animals1 & m9]al species1 are n includ$2 ^! be+ briefly & sy/ematically discuss$ 9 *apt]s #ag1 #ah1 #ai1 & #bj1 respectively4 ,by us+ ! index ! read] c quickly locate ! page :]e any "o ( ^! names is discuss$4 ,"s def9itions 9 ?is gloss>y are tak5 f ,u4 ,s4 ,survey ,bullet9 ,no4 #fac4 ,anticl9e4--,a k9d ( fold$ /ructure 9 :i* /rata h be5 b5t upw>d or ar*$4 ,ar*eozoic4--,! e>lie/ kn[n era ( geologic "t4 ,basalt4--,a common lava ( d>k color & ( great fluidity :5 molt54 ,basalt is less silice\s ?an granite & rhyolite1 & conta9s mu* m iron1 calcium1 & magnesium4 ,base-level4--,! l[e/ level to :i* a /ream c cut 7erode7 its *annel4 ,a :ole region may be base-level$ by erosion4 ,cambrian4--,! fir/ or e>lie/ p]iod ( ! ,paleozoic era ( geologic "t4 ,c5ozoic4--,! pres5t era ( geologic "t4 ,x began at lea/ sev]al million ye>s ago4 ,*alk4--,a s(t1 f9e-gra9$1 :ite lime/one consi/+ ma9ly ( t9y %ells4 ,conglom]ate4--,a s$im5t>y rock consi/+ ( consolidat$ or cem5t$ gravel4 ,(t5 s&y4 ,cretace\s4--,! la/ p]iod ( ! ,mesozoic era ( geologic "t4 ,cry/al4--,a regul> polyh$ral =m1 possess+ a def9ite int]nal molecul> /ructure1 :i* is assum$ by a sub/ance 9 pass+ f ! /ate ( a liquid or gas to t ( a solid4 ,ne>ly e m9]al1 "u prop] conditions1 w cry/allize4 ,cry/all9e ,rock4--,a rock compos$ ( closely fitt+ m9]al cry/als t h =m$ 9 ! rock sub/ance1 z contra/$ ) "o made up ( cem5t$ gra9s ( s& or o!r mat]ials1 or ) a volcanic glass4 ,cry/allography4--,! /udy ( cry/als4 ,devonian4--,! middle "o ( ! sev5 p]iods ( ! ,paleozoic era ( geologic "t4 ,dike4--,a mass ( igne\s rock t has solidifi$ 9 a fissure or crack 9 ! e>?'s cru/4 ,drift4--,commonly call$ glacial drift4 ,! rock fragm5ts--soil1 gravel1 & silt--c>ri$ by a glaci]4 ,drift includes ! unassort$ mat]ial kn[n z till 7gr\nd mora9e7 & deposits made by /reams fl[+ f a glaci]4 ,dr[n$ ,riv] ,valley4--,:5 a l& surface s9ks en\gh to p]mit tidewat] to ent] ! l[] ends ( its valleys to =m e/u>ies1 a good example be+ ! l[] ,hudson ,valley4 ,era4--,a "n appli$ to "o ( ! broade/ subdivisions ( geologic "t 7e4g4 ,paleozoic era74 ,erosion4--,! we>+ away & transportation ( mat]ials at & ne> ! e>?'s surface by wea!r+ & solution1 & ! me*anical action ( runn+ wat]1 waves1 mov+ ice1 or w9ds :i* use rock fragm5ts z tools or abrasives4 ,exfoliation4--,! splitt+ (f ( %eets ( rock ( v>i\s sizes & %apes due to *anges ( temp]ature4 ,x is a process ( wea!r+4 ,fault4--,a fracture 9 ! e>?'s cru/ accompani$ by movem5t ( ! rock on "o side ( ! break pa/ t on ! o!r4 ,if ! fracture is incl9$ & ! rock on "o side appe>s to h slid d[n ! slope ( ! fracture ! fault is t]m$ a normal fault4 ,if1 on ! o!r h&1 ! rock on "o side appe>s to h be5 %ov$ up ! incl9$ plane ( ! break1 ! fault is t]m$ a rev]se or ?ru/ fault4 ,fault-block4--,a "p ( ! e>?'s cru/ b\nd$ :olly or 9 "p by faults4 ,fault-sc>p4--,! cliff =m$ by a fault4 ,mo/ fault sc>ps h be5 modifi$ by erosion s9ce ! fault+4 ,fissure4--,a crack1 break1 or fracture 9 ! e>?'s cru/ or 9 a mass ( rock4 ,flood-pla94--,! ne>ly level l& t bord]s a /ream & is subject to occasional ov]fl[4 ,flood-pla9s are built up by s$im5t left by su* ov]fl[s4 ,fold4--,a b5d 9 rock lay]s or b$s4 ,anticl9es & syncl9es are ! common types ( folds4 ,=mation4--,a rock lay]1 or a s]ies ( cont9u\sly deposit$ lay]s gr\p$ toge!r1 reg>d$ by ! geologi/ z a unit = purposes ( description & mapp+4 ,a =mation is usually nam$ f "s place :]e x is expos$ 9 its typical "*4 ,fossil4--,! :ole or any "p ( an animal or plant t has be5 pres]v$ 9 ! rocks or ! impression left on rock by a plant or animal4 ,pres]vation is inv>iably accompani$ by "s *ange 9 sub/ance1 & f "s fossils ! orig9al sub/ance has all be5 remov$4 ,geography4--,! /udy ( ! di/ribution ( ! e>?'s physical features1 9 _! relation to ea* o!r to ! life ( sea & l&1 & human life & culture4 ,geology4--,! sci5ce :i* deals ) ! hi/ory ( ! e>? & its inhabitants z reveal$ 9 ! rocks4 ,glaci]4--,a body ( ice :i* sl[ly spreads or moves ov] ! l& f its place ( accumulation4 ,gneiss 7pron\nc$ nice74--,a metamorphic1 cry/all9e rock ) m9]al gra9s arrang$ ) long axes m or less p>allel1 giv+ ! rock a b&$ appe>ance4 ,d]iv$ f ei!r igne\s or /ratifi$ rocks well )9 ! e>? "u conditions ( pressure1 & usually also heat & moi/ure4 ,igne\s ,rocks4--,rocks =m$ by ! cool+ & solidification ( a hot liquid mat]ial1 kn[n z magma1 t has orig9at$ at unkn[n dep?s )9 ! e>?4 ,^? t h solidifi$ b5ea? ! surface are kn[n z intrusive rocks1 or if ! cool+ has tak5 place sl[ly at great dep?1 z plutonic rocks1 e4g4 granite4 ,^? t h fl[$ out ov] ! surface are kn[n z effusive rocks1 extrusive rocks1 or lavas1 e4g41 basalt4 ,volcanic rocks include n only lavas1 b bombs1 pumice1 tuff1 volcanic a%1 & o!r fragm5tal mat]ials or ejecta ?r[n out f volcanoes4 ,jo9ts4--,ne>ly all rocks1 except v loose surface mat]ials1 are sep>at$ into blocks ( v>y+ size & %ape by a sy/em ( cracks call$ jo9ts4 ,!y may be caus$ by e>?-cru/ movem5ts1 contraction dur+ solidification ( molt5 rocks1 or contraction dur+ dry+ out ( s$im5ts4 ,jurassic4--,! middle "o ( ! ?ree p]iods ( ! ,mesozoic era ( geologic "t4 ,lava4--,an igne\s rock :i* 9 molt5 condition has p\r$ out ^u or close to ! e>?'s surface1 e4g4 basalt4 ,lime/one4--,a s$im5t>y rock consi/+ ess5tially ( c>bonate ( lime :i* g5]ally repres5ts accumulation ( %ells ( organisms1 b 9 "s cases precipitates f solution4 ,(t5 impure4 ,loess 7pron\nc$ lurse ) ! r obscure74--,a f9e homog5e\s silt or loam %[+ usually no division into lay]s & =m+ ?ick & ext5sive deposits 9 ! ,mississippi ,valley & 9 ,*9a4 ,x is g5]ally reg>d$ z 9 "p at lea/ a deposit ( w9d-bl[n du/4 ,m>ble4--,a cry/all9e lime/one1 usually a metamorphic rock1 ! lime/one hav+ be5 alt]$ by heat1 pressure1 & moi/ure )9 ! e>?4 ,me&]4--,to fl[ 9 s]p5t9e curves4 ,a loop 9 a /ream4 ,mo/ /reams 9 fl[+ across pla9s develop me&]s4 ,mesa4--,a flat-topp$ hill or m\nta9 left isolat$ dur+ ! g5]al erosion or cutt+ d[n ( a region4 ,mesozoic4--,next to ! pres5t era ( geologic "t4 ,metamorphic ,rock4--,any igne\s or s$im5t>y rock :i* has und]gone metamorphism1 t is notable alt]ation f its orig9al condition4 7,see ,metamorphism47 ,metamorphism4--,any *ange 9 rocks effect$ 9 ! e>? by heat1 pressure1 solutions1 or gases4 ,a common cause ( ! metamorphism ( rocks is ! intrusion into !m ( igne\s rocks4 ,rocks t h be5 s *ang$ are t]m$ metamorphic4 ,m>ble1 = example1 is metamorphos$ lime/one4 ,m9]al4--,an inorganic sub/ance ( def9ite *emical composition f\nd ready made 9 nature1 e4g4 calcite1 qu>tz4 ,mississippian4--,a p]iod ( ! ,paleozoic era ( geologic "t--9 ord] ( age1 ! ?ird f ! la/ ( ! era4 ,mora9e4--,glacial drift c>ri$ on1 )91 or "u a glaci] & deposit$ at ! end1 along ! sides1 or "u ! glaci]4 ,oil-pool4--,an accumulation or body ( oil 9 s$im5t>y rock t yields petroleum on drill+4 ,! oil occurs 9 ! pores ( ! rock & is n a pool or pond 9 ! ord9>y s5se ( ^! words4 ,ordovician4--,next to ! e>lie/ p]iod ( ! ,paleozoic era ( geologic "t4 ,ore4--,a metal-be>+ m9]al or rock ( suffici5t value to be m9$4 ,outcrop4--,t "p ( a rock =mation :i* appe>s at ! surface4 ,! appe>ance ( a rock at ! surface or its projection above ! soil4 ,(t5 call$ an exposure4 ,paleontology4--,! /udy ( ! _w's 7geologically7 anci5t life1 ei!r plant or animal1 by means ( fossils4 ,paleozoic4--,an old era ( geologic "t--?ird back f ! pres5t4 ,p5epla94--,a region r$uc$ almo/ to a pla9 by ! long-cont9u$ normal erosion ( a l& surface4 ,x %\ld be di/+ui%$ f a pla9 produc$ by ! attack ( waves along a coa/ or ! built-up flood pla9 ( a riv]4 ,p5nsylvanian4--,next to ! la/ p]iod ( ! ,paleozoic era ( geologic "t4 ,p]iod4--,a "n appli$ to "o ( ! subdivisions ( an era ( geologic "t1 e4g4 ,cambrian p]iod4 ,p]mian4--,! la/ p]iod ( ! ,paleozoic era ( geologic "t4 ,petrology4--,! /udy ( rocks1 includ+ igne\s1 s$im5t>y1 & metamorphic rocks4 ,physiography4--,! /udy ( ! relief features ( ! e>? & h[ !y 7 produc$4 ,plac] ,deposit4--,a mass ( gravel1 s&1 or simil> mat]ial result+ f ! crumbl+ & erosion ( solid rocks & conta9+ p>ticles or nuggets ( gold1 plat9um1 t91 or o!r valuable m9]als1 :i* h be5 d]iv$ f rocks or ve9s4 ,plutonic ,rock4--,an igne\s rock solidifi$ f a molt5 condition well )9 ! e>?4 7,see ,igne\s ,rocks47 ,prot]ozoic4--,next to ! e>lie/ kn[n era ( geologic "t4 ,qu>tzite4--,a metamorphic rock compos$ ( s& gra9s cem5t$ by silica into an extremely h>d mass4 ,quat]n>y4--,! lat] ( ! two p]iods ( ! ,c5ozoic era ( geologic "t4 ,rejuv5at$4--,any region :i* has be5 subject$ to erosion = a great] or less l5g? ( "t & !n reelevat$ s t ! /reams are r5ew$ 9 activity4 ,rock4--,any ext5sive con/itu5t ( ! cru/ ( ! e>?1 usually consi/+ ( a me*anical mixture ( two or m m9]als1 e4g4 granite1 %ale4 ,less commonly a rock consi/s ( a s+le m9]al 7e4g4 pure m>ble71 or ( organic matt] 7e4g4 coal74 ,s&/one4--,a s$im5t>y rock consi/+ ( consolidat$ or cem5t$ s&4 ,(t5 %aly or limy4 ,s*i/4--,a rock t by subjection to heat & pressure & usually moi/ure )9 ! e>? has und]gone a *ange 9 ! "* ( ! p>ticles or m9]als t compose x & has ^! m9]als arrang$ 9 su* a way t ! rock splits m easily 9 c]ta9 directions ?an 9 o!rs4 ,x is a metamorphic rock d]iv$ f ei!r s$im5t>y or igne\s rock1 m commonly ! =m]4 ,s$im5t>y ,rocks4--,rocks =m$ by ! accumulation ( s$im5t 9 wat] 7aque\s deposits7 or f air 7eolian deposits74 ,! s$im5t may consi/ ( rock fragm5ts or p>ticles ( v>i\s sizes 7conglom]ate1 s&/one1 %ale72 ( ! rema9s or products ( animals or plants 7c]ta9 lime/ones & coal72 ( ! product ( *emical action or ( evaporation 7salt1 gypsum1 etc472 or ( mixtures ( ^! mat]ials4 ,"s s$im5t>y deposits 7tuffs7 are compos$ ( fragm5ts bl[n f volcanoes & deposit$ on l& or 9 wat]4 ,a *>act]i/ic feature ( s$im5t>y deposits is a lay]$ /ructure kn[n z b$d+ or /ratification4 ,ea* lay] is a b$ or /ratum4 ,s$im5t>y b$s z deposit$ lie flat or ne>ly flat1 b subsequ5tly !y h (t5 be5 de=m$ by fold+ & fault+4 ,%ale4--,a s$im5t>y rock consi/+ ( h>d5$ ?9 lay]s ( f9e mud4 ,silurian4--,a p]iod ( ! ,paleozoic era ( geologic "t--9 ord] ( age1 ! ?ird f ! beg9n+ ( ! era4 ,slate4--,a rock t by subjection to pressure )9 ! e>? has acquir$ ! prop]ty ( splitt+ smoo?ly into ?9 plates4 ,! cleavage is smoo!r & m regul> ?an ! splitt+ ( s*i/ along its gra94 ,x is a metamorphic rock ne>ly always d]iv$ f %ale4 ,soil4--,! mantle ( loose mat]ial re/+ ^u b$rock1 ei!r 9 its place ( orig9 or transport$ by wat]1 w9d1 or ice4 ,/rata 7or /ratifi$ rocks74--,s$im5t>y rocks :i*1 by ! sort+ p[] ( wat] 7less (t5 by w9d71 are arrang$ 9 m or less def9ite lay]s or b$s sep>at$ by /ratification surfaces4 ,/ratification4--,! sep>ation ( s$im5t>y rocks into m or less p>allel lay]s or b$s4 ,/ratigraphy4--,! bran* ( geologic sci5ce t deals ) ! ord] & relations ( ! /rata ( ! e>?'s cru/4 ,/ructure4--,9 geology1 ! =ms assum$ by s$im5t>y b$s & igne\s rocks t h be5 mov$ f _! orig9al position by =ces )9 ! e>?1 or ! =ms tak5 by intrusive masses ( igne\s rock 9 connection ) effects produc$ me*anically on neighbor+ rocks by ! intrusion4 ,folds 7anticl9es & syncl9es7 & faults are ! pr9cipal me*anical effects consid]$ "u /ructure4 ,s*i/osity & cleavage are also /ructural features4 ,syncl9e4--,a k9d ( fold$ /ructure 9 :i* /rata h be5 b5t d[nw>d4 ,x is an inv]t$ ar*--! opposite ( an anticl9e4 ,talus 7pron\nc$ tay'lus74--,! mass ( loose rock fragm5ts t accumulates at ! base ( a cliff or /eep slope4 ,t]race4--,a /eplike b5* on a hillside4 ,mo/ t]races along riv]s are remnants ( valley bottoms =m$ :5 ! /ream fl[$ at high] levels4 ,o!r t]races h be5 =m$ by waves4 ,"s t]races h be5 cut 9 solid rock1 o!rs h be5 built up ( s& & gravel1 & /ill o!rs h be5 p>tly cut & p>tly built up4 ,t]ti>y4--,! e>li] ( ! two p]iods ( ! ,c5ozoic era ( geologic "t4 ,triassic4--,! e>lie/ p]iod ( ! ,mesozoic ,era ( geologic "t4 ,uncon=mity4--,a break 9 ! regul> succession ( s$im5t>y rocks1 indicat$ by ! fact t "o b$ re/s on ! erod$ surface ( "o or m b$s :i* may h a di/9ctly diff]5t dip f ! b$ above4 ,an uncon=mity may indicate t ! b$s bel[ x h at "s "t be5 rais$ above ! sea & h be5 erod$4 ,9 "s places b$s ?\s&s ( feet ?ick h be5 wa%$ away be=e ! l& aga9 became subm]g$ & ! fir/ b$ above ! surface ( uncon=mity 0 deposit$4 ,if b$s ( rock may be reg>d$ z leaves 9 ! volume ( geologic hi/ory1 an uncon=mity m>ks a gap 9 ! record4 ,ve94--,a mass ( m9]al mat]ial t has be5 deposit$ 9 or along a fissure 9 ! rocks4 ,a ve9 diff]s f a dike 9 t ! ve9 mat]ial 0 introduc$ gradually by deposition f solution1 :]eas a dike 0 intrud$ 9 a molt5 condition4 ,qu>tz & calcite are v common ve9 m9]als4 ,volcanic ,rocks4--,igne\s rocks erupt$ at or ne> ! e>?'s surface1 includ+ lavas1 tuffs1 volcanic a%es1 & l mat]ial4 ,wea!r+4--,! gr\p ( processes1 su* z ! *emical action ( air & ra9 wat]1 & ( plants & bact]ia1 & ! me*anical action ( *anges ( temp]ature1 :]eby rocks on exposure to ! wea!r *ange 9 "*1 decay1 & f9ally crumble into soil4 ,transcrib] ,note ,all illu/rations splitt+ p>agraphs 7 mov$ be=e or aft] ! p>agraph4 ,all simple typos 7 correct$ 7i4e41 ,reudemann to ,ru$emann1 pryox5e to pyrox5e74