,volcanoes ( ! ,unit$ ,/ates by ,/ev5 ,r4 ,brantley ,= sale by ! ,,u4 ,gov]nm5t ,pr9t+ ,(fice ,sup]9t5d5t ( ,docum5ts1 ,mail ,/op3 ,,ssop1 ,wa%+ton1 ,,dc #bjdjb-icbh ,,isbn #j-af-jdejed-c ,illu/ration3 ,m\nt ,%a/a1 ,cali=nia1 has erupt$ at lea/ #aj times 9 ! pa/ #c1djj ye>s & at lea/ #c times 9 ! pa/ #gej ye>s4 7,photograph by ,lyn ,top9ka47 ,introduction ,few natural =ces are z spectacul> & ?reat5+1 or h play$ su* a dom9ant role 9 %ap+ ! face ( ! ,e>?1 z erupt+ volcanoes4 ,volcanism has built "s ( ! _w's greate/ m\nta9 ranges1 cov]$ va/ regions ) lava 7molt5 rock at ! ,e>?'s surface71 & trigg]$ explosive eruptions ^: size & p[] are ne>ly impossible = u to imag9e today4 ,=tunately1 su* calamit\s eruptions occur infrequ5tly4 ,( ! #ej or s volcanoes t erupt e ye>1 h[ev]1 a few sev]ely disrupt human activities4 ,betwe5 #aihj & #aiij1 volcanic activity kill$ at lea/ #bf1jjj p & =c$ ne>ly #dej1jjj to flee f _! homes4 ,?\gh few p 9 ! ,unit$ ,/ates may actually exp]i5ce an erupt+ volcano1 ! evid5ce = e>li] volcanism is pres]v$ 9 _m rocks ( ,nor? ,am]ica4 ,features se5 9 volcanic rocks only h\rs old are also pres5t 9 anci5t volcanic rocks1 bo? at ! surface & buri$ b5ea? y\ng] deposits4 ,a ?ick a% deposit s&wi*$ betwe5 lay]s ( s&/one 9 ,nebraska1 ! massive granite peaks ( ! ,si]ra ,nevada m\nta9 range1 & a v>iety ( volcanic lay]s f\nd 9 ea/]n ,ma9e are b a few ( ! /rik+ clues ( pa/ volcanism4 ,) ?is p]spective1 an erupt+ volcano is n only an excit+ & awesome spectacle 9 its own "r b a w9d[ into a natural process t has happ5$ ov] & ov] aga9 ?r\gh\t ,e>?'s hi/ory4 ,! ,e>?'s cru/1 on :i* we live & dep5d1 is 9 l>ge "p ! product ( millions ( once-active volcanoes & trem5d\s volumes ( magma 7molt5 rock bel[ gr\nd7 t did n erupt b in/ead cool$ bel[ ! surface4 ,su* p]si/5t & widespread volcanism has result$ 9 _m valuable natural res\rces ?r\gh\t ! _w4 ,= example1 volcanic a% bl[n ov] ?\s&s ( squ>e kilomet]s ( l& increases soil f]tility = =e/s & agriculture by add+ nutri5ts & act+ z a mul*4 ,gr\ndwat] heat$ by l>ge1 /ill-hot magma bodies c be tapp$ = geo!rmal en]gy4 ,& ov] _m ?\s&s ( ye>s1 heat$ gr\ndwat] has conc5trat$ valuable m9]als1 includ+ copp]1 t91 gold1 & silv]1 into deposits t are m9$ ?r\gh\t ! _w4 ,! ,unit$ ,/ates ranks ?ird1 beh9d ,indonesia & ,japan1 9 ! numb] ( hi/orically active volcanoes 7t is1 ^? = :i* we h writt5 acc\nts ( eruptions74 ,9 addition1 ab\t #aj p]c5t ( ! m ?an #a1ejj volcanoes t h erupt$ 9 ! pa/ #aj1jjj ye>s are locat$ 9 ! ,unit$ ,/ates4 ,mo/ ( ^! volcanoes are f\nd 9 ! ,aleutian ,isl&s1 ! ,alaska ,p59sula1 ! ,hawaiian ,isl&s1 & ! ,cascade ,range ( ! ,pacific ,nor?we/2 ! rema9d] are widely di/ribut$ 9 ! we/]n "p ( ! ,nation4 ,a few ,u4,s4 volcanoes h produc$ "s ( ! l>ge/ & mo/ dang]\s types ( eruptions 9 ?is c5tury1 :ile sev]al o!rs h ?reat5$ to erupt4 ,illu/ration3 ,map ( ,unit$ ,/ates %[+ areas :]e active volcanoes are locat$ & %[n lat] 9 m detail4 ,,alaska ,see page #bd ,,unit$ ,,/ates ,see page #af ,,hawaiian ,,isl&s ,see page #aj ,sci5ti/s at ! ,u4,s4 ,geological ,survey 7,,usgs7 engage 9 a v>iety ( rese>* activities 9 ord] to r$uce ! loss ( life & prop]ty t c result f volcanic eruptions & to m9imize ! social & economic turmoil t c result :5 volcanoes ?reat5 to erupt4 ,^! activities include /udies ( ! physical processes be=e1 dur+1 & aft] a volcanic eruption1 assessm5ts ( volcano haz>ds1 & public outrea* to translate sci5tific in=mation ab\t volcanoes into t]ms t are mean+ful to ! public & public (ficials4 ,monitor+ volcanoes = signs ( activity1 ano!r vital compon5t1 is c>ri$ out by ,,usgs e>? sci5ti/s at ?ree volcano obs]vatories1 :i* 7 e/abli%$ to /udy active volcanoes 9 ,hawaii 7#aiab71 ! ,cascades 7#aihj71 & ,alaska 7#aihh74 ,^! rese>*]s record e>?quakes1 survey ! surfaces ( volcanoes1 map volcanic rock deposits1 & analyze ! *emi/ry ( volcanic gas & fre% lava to detect w>n+ signs ( imp5d+ activity & det]m9e ! mo/ likely type ( activity t w affect areas ar\nd a volcano4 ,dur+ ! pa/ #aj ye>s1 sev]al w>n+s ( eruptions 7 issu$ by ! ,,usgs & monitor+ ( rec5tly active volcanoes 9 ! ,unit$ ,/ates 0 exp&$4 ,pr$ict+ ! "t & size ( volcanic eruptions1 h[ev]1 rema9s a difficult *all5ge = sci5ti/s4 ,illu/ration3 ,sci5ti/ collects lava sample f lava fl[ ent]+ ! sea on ,kilauea ,volcano4 7,photograph by ,j4,d4 ,griggs47 ,illu/ration3 ,sci5ti/s conduct+ field /udies on active volcanoes 9 ! ,unit$ ,/ates4 ,illu/ration3 ,field /udies4 ,illu/ration3 ,field /udies4 ,illu/ration3 ,field /udies4 ,volcanoes & ! ,!ory ( ,plate ,tectonics ,illu/ration3 ,major tectonic plates ( ! ,e>?4 ,only a few ( ! ,e>?'s active volcanoes are %[n4 7,sket* by ,ell5 ,l\gae47 ,,plates ,,eurasian ,,nor? ,,am]ican ,,juan ,,de ,,fuca ,,philipp9e ,,c>ibbean ,,pacific ,,cocos ,,nazca ,,au/ralian ,,eurasian ,,arabian ,,indian ,,african ,,s\? ,,am]ican ,,scotia ,,ant>ctic ,,explanation ,plate b\nd>y ,active volcanoes ,volcanoes are n r&omly di/ribut$ ov] ! ,e>?'s surface4 ,mo/ are conc5trat$ on ! edges ( cont95ts1 along isl& *a9s1 or b5ea? ! sea =m+ long m\nta9 ranges4 ,m ?an half ( ! _w's active volcanoes above sea level encircle ! ,pacific ,ocean to =m ! circum-,pacific 8,r+ ( ,fire40 ,9 ! pa/ #be ye>s1 sci5ti/s h develop$ a !ory--call$ plate tectonics--t expla9s ! locations ( volcanoes & _! relation%ip to o!r l>ge-scale geologic features4 ,accord+ to ?is !ory1 ! ,e>?'s surface is made up ( a pat*work ( ab\t a doz5 l>ge plates t move relative to "o ano!r at spe$s f less ?an "o c5timet] to ab\t t5 c5timet]s p] ye> 7ab\t ! spe$ at :i* f+]nails gr[74 ,^! rigid plates1 ^: av]age ?ickness is ab\t #hj kilomet]s1 are spread+ ap>t1 slid+ pa/ ea* o!r1 or collid+ ) ea* o!r 9 sl[ motion on top ( ! ,e>?'s hot1 pliable int]ior4 ,volcanoes t5d to =m :]e plates collide or spread ap>t1 b !y c also gr[ 9 ! middle ( a plate1 z = example ! ,hawaiian volcanoes4 ,illu/ration3 ,! b\nd>y betwe5 ! ,pacific & ,juan de ,fuca ,plates is m>k$ by a broad subm>9e m\nta9 *a9 ab\t #ejj km long1 kn[n z ! ,juan de ,fuca ,ridge4 ,"y volcanoes1 lava fl[s1 & hot spr+s 7 discov]$ 9 a broad valley less ?an #h km wide along ! cre/ ( ! ridge 9 ! #aigj's4 ,! ocean floor is spread+ ap>t & =m+ new ocean cru/ along ?is valley or 8rift0 z hot magma f ! ,e>?'s int]ior is inject$ into ! ridge & erupt$ at its top4 ,9 ! ,pacific ,nor?we/1 ! ,juan de ,fuca ,plate plunges b5ea? ! ,nor? ,am]ican ,plate4 ,z ! d5s] plate ( oceanic cru/ is =c$ deep into ! ,e>?'s int]ior b5ea? ! cont95tal plate1 a process kn[n z subduction1 x enc\nt]s high temp]atures & pressures t p>tially melt solid rock4 ,"s ( ?is newly =m$ magma rises t[>d ! ,e>?'s surface to erupt1 =m+ a *a9 ( volcanoes above ! subduction zone4 ,,pacific ,,plate ,juan de ,fuca ,ridge ,,juan ,,de ,,fuca ,,plate ,,nor? ,,am]ican ,,plate ,mt4 ,bak] ,glaci] ,peak ,mt4 ,ra9i] ,,magma ,magma ,conduit ,illu/ration3 ,locat$ 9 ! middle ( ! ,pacific ,plate1 ! volcanoes ( ! ,hawaiian ,isl& *a9 are among ! l>ge/ on ,e>?4 ,! volcanoes /ret* #b1ejj km across ! nor? ,pacific ,ocean & become progressively old] to ! nor?we/4 ,=m$ initially above a relatively /ation>y 8hot spot0 9 ! ,e>?'s int]ior1 ea* volcano 0 raft$ away f ! hot spot z ! ,pacific ,plate moves nor?we/w>d at ab\t #i cm p] ye>4 ,! isl& ( ,hawaii consi/s ( ! y\nge/ volcanoes 9 ! *a9 & is curr5tly locat$ ov] ! hot spot4 ,,hawaii ,,niihau ,,kauai ,,oahu ,,molokai ,,lanai ,,maui ,,kahoolawe ,,pacific ,,plate ,oceanic ,cru/ ,fix$ 8,hot ,spot0 ,zone ( magma =mation ext5ds to ,kilauea ,mauna ,loa ,direction ( place movem5t ,rec5t ,eruptions ,f ,u4,s4 ,volcanoes ,hawaiian volcanoes ,few places on ,e>? all[ clos] or m dramatic views ( volcanic activity ?an ,mauna ,loa & ,kilauea volcanoes on ! isl& ( ,hawaii4 ,_! frequ5t b usually non-explosive eruptions make !m ideal = sci5tific /udy4 ,kilauea's eruptions are s int5sely monitor$ t sci5ti/s h assembl$ a detail$ picture ( ! volcano's magma res]voir 8plumb+0 sy/em & h[ x behaves be=e & dur+ eruptions4 ,/udies ( ^! volcanoes & ! surr\nd+ ocean floor cont9ue to improve our und]/&+ ( ! geologic hi/ory ( ! ,hawaiian ,isl& *a9 & ! ability ( sci5ti/s to det]m9e volcanic haz>ds t ?reat5 isl& resid5ts4 ,illu/ration3 ,hawaiian ,volcanoes ,,explanation ,volcano active dur+ pa/ #b1jjj ye>s ,pot5tially active volcano ,population c5t]s #ej1jjj to #ajj1jjj #cej1jjj to #a1jjj1jjj ,,pacific ,,ocean ,,niihau ,,kauai ,,oahu ,honolulu ,,molokai ,,maui ,haleakala ,,lanai ,,kahoolawe ,,hawaii ,kohala ,mauna ,kea ,hilo ,hualalai ,mauna ,loa ,kilauea ,lohi ,eruptions ( ,hawaiian volcanoes are typically non-explosive because ( ! composition ( ! magma4 ,almo/ all ( ! magma erupt$ f ,hawaii's volcanoes =ms d>k gray to black volcanic rock 7call$ basalt71 g5]ally 9 ! =m ( lava fl[s &1 less commonly1 z fragm5t$ lava su* z volcanic bombs1 c9d]s1 pumice1 & a%4 ,basalt magma is m fluid ?an ! o!r types ( magma 7&esite1 dacite1 & rhyolite74 ,consequ5tly1 exp&+ volcanic gases c escape f basalt relatively easily & c propel lava high into ! air1 =m+ brilliant f\nta9s sometimes call$ 8curta9s ( fire40 ,lava1 :e!r erupt$ 9 high f\nta9s or quietly p\r+ out1 collects to =m fl[s t spread across ! gr\nd 9 ?9 broad %eets or 9 n>r[ /reams4 ,! fluid nature ( basalt magma all[s x to travel great di/ances f ! v5t 7! place :]e lava breaks gr\nd7 & t5ds to build volcanoes 9 ! %ape ( an inv]t$ w>rior %ield1 ) slopes less ?an ab\t #aj degrees4 ,volcanoes ) ?is k9d ( pr(ile are call$ %ield volcanoes4 ,hawaiian volcanoes erupt at _! summit cald]as & f _! flanks along l9e> rift zones t ext5d f ! cald]as4 ,cald]as are l>ge /eep-wall$ depressions t =m :5 a volcano's summit region collapses1 usually aft] a l>ge eruption empties or p>tly empties a res]voir ( magma b5ea? ! volcano4 ,rift zones are areas ( weakness )9 a volcano t ext5d f ! surface to dep?s ( sev]al kilomet]s4 ,magma t erupts f ! flank ( a volcano mu/ fir/ fl[ und]gr\nd ?r\gh "o ( ! volcano's rift zones1 sometimes travel+ m ?an #cj kilomet]s f ! summit magma res]voir be=e break+ ! surface4 ,mauna ,loa4 ,ris+ m ?an #i1jjj met]s f ! seafloor1 ,mauna ,loa is "o ( ! _w's l>ge/ active volcanoes2 f its base bel[ sea level to its summit1 ,mauna ,loa is tall] ?an ,m\nt ,ev]e/4 ,x has erupt$ #ae times s9ce #aijj1 ) eruptions la/+ f less ?an #a day to z _m z #ade days4 ,! mo/ rec5t eruption began be=e dawn on ,m>* #be1 #aihd4 ,brilliant lava f\nta9s lit ! night-"t sky z fissures op5$ across ! floor ( ! cald]a4 ,)9 h\rs1 ! summit activity /opp$ & lava began erupt+ f a s]ies ( v5ts along ! nor!a/ rift zone4 ,:5 ! eruption /opp$ #c weeks lat]1 lava fl[s 7 only #f4e kilomet]s f build+s 9 ! city ( ,hilo4 ,mauna ,loa erupts less frequ5tly ?an ,kilauea1 b x produces a mu* great] volume ( lava ov] a %ort] p]iod ( "t4 ,illu/ration3 ,lava f\nta9s erupt f along ,mauna ,loa's rift zone4 ,f\nta9s are ab\t #be met]s high4 7,photograph by ,j4,d4 ,griggs47 ,kilauea ,volcano4 ,kilauea's longe/ rift-zone eruption 9 hi/orical "t began on ,janu>y #c1 #aihc4 ,a r[ ( lava f\nta9s broke out f its ea/ rift zone ab\t #ag kilomet]s f ! summit cald]a2 )9 a few mon?s1 ! activity settl$ d[n to a s+le v5t4 ,p[]ful f\nta9+ episodes hurl$ molt5 rock #dej met]s into ! air & built a cone ( lava fragm5ts t quickly became ! talle/ l&m>k on ! rift zone4 ,! eruption *ang$ /yle abruptly 9 ,july #aihf :5 lava broke out ?r\gh a new v5t4 ,in/ead ( regul> episodes ( high lava f\nta9+1 lava spill$ cont9u\sly onto ,kilauea's surface4 ,! /eady outp\r+ ( lava =m$ a lake ( molt5 rock t became p]*$ atop a small %ield volcano4 ,by ,june #aiia1 ! %ield 0 ab\t #fj met]s tall & #a1fjj met]s 9 diamet]1 & lava f ! eruption _h cov]$ #ge squ>e kilomet]s ( =e/ & grassl&1 add$ #abj hect>es ( new l& to ! isl&1 & de/roy$ #agi homes4 ,illu/ration3 ,a]ial view ( ,hawaii's two mo/ active volcanoes1 ,kilauea & ,mauna ,loa4 7,photograph by ,j4,d4 ,griggs47 ,mauna ,loa ,halemaumau ,crat] ,kilauea cald]a ,al?\gh mo/ ( ,kilauea's hi/orical rift eruptions 7 mu* brief]1 prolong$ eruptive activity 9 ! ea/ rift zone f #aifi to #aigd =m$ a simil> %ield1 ,mauna ,ulu 7,hawaiian = 8,gr[+ ,m\nta9071 & an ext5sive lava field on ! volcano's s\? flank4 ,! geologic record %[s t su* l>ge-volume eruptions f ! rift zones & ! summit area1 cov]+ l>ge p>ts ( ,kilauea's surface1 h occurr$ _m times 9 ! rec5t pa/4 ,9 fact1 ab\t #ij p]c5t ( ,kilauea's surface is cov]$ ) lava fl[s t are less ?an #a1ajj ye>s old4 ,illu/ration3 ,! volcanic cone ( ,pu'u ,o'o1 nam$ aft] an ext9ct ,hawaiian bird1 t[]s above an active lava lake 7backgr\nd74 7,photograph by ,j4,d4 ,griggs47 ,mo/ eruptions at ,kilauea c be view$ at close range1 b a few hi/orical eruptions 7 dang]\sly explosive4 ,fa/-mov+ mixtures ( a% & gas1 call$ pyrocla/ic surges1 rac$ across ! summit area & into ! s\?we/ rift zone dur+ an eruption 9 #agij4 ,footpr9ts pres]v$ 9 a lay] ( a% #cj kilomet]s s\?we/ ( ! summit probably include ^? ( a p>ty ( ,hawaiian w>riors & _! families :o 7 cross+ ! volcano :5 ! eruption /ruck4 ,an e/imat$ #hj ( ! #bej p 7 kill$ by suffocat+ cl\ds associat$ ) ! pyrocla/ic surges4 ,a small] explosive eruption 9 #aibd f ,halemaumau ,crat] 9 ,kilauea summit cald]a1 :i* kill$ a photograph] :o 0 too close1 hurl$ rocks weigh+ z mu* z #h tons z f> z #a kilomet]4 ,illu/ration3 ,lava f\nta9 erupt+ f ,pu'u ,o'o cone4 ,=ty-f\r episodes ( su* f\nta9+ betwe5 #aihc & #aihf built ! cone #bee met]s tall4 7,photograph by ,j4,d4 ,griggs47 ,cascade volcanoes ,volcanoes ( ! ,cascade ,range erupt f> less frequ5tly ?an ,kilauea & ,mauna ,loa1 b !y are m dang]\s because ( _! viol5tly explosive behavior & _! proximity to populat$ & cultivat$ areas 9 ,wa%+ton1 ,oregon1 & ,cali=nia4 ,! #aihj eruption ( ,m\nt ,/4 ,hel5s 9 s\?we/ ,wa%+ton dramatically illu/rat$ ! type ( volcanic activity & de/ruction ^! volcanoes c produce4 ,sci5tific /udies ( ! eruption ( ,m\nt ,/4 ,hel5s & ! eruptive hi/ories ( o!r ,cascade volcanoes cont9ue to improve public aw>5ess & und]/&+ ( ^! pot5tially dang]\s peaks4 ,9 contra/ to ,kilauea1 ,cascade volcanoes erupt a v>iety ( magma types t g5]ate a wide range ( eruptive behavior & build /eep-sid$ cones kn[n z composite volcanoes4 ,9 addition to basalt1 &esite & dacite magmas are common4 ,illu/ration3 ,cascade ,volcanoes4 ,,explanation ,volcano active dur+ pa/ #b1jjj ye>s ,pot5tially active volcano ,area ( pot5tial volcanic activity ,population c5t]s #dj1jjj to #ajj1jjj #ajj1jjj to #cej1jjj #cej1jjj to #a1jjj1jjj ,great] ?an #a1jjj1jjj ,,pacific ,,ocean ,,wa%+ton ,m\nt ,bak] ,glaci] ,p>k ,seattle ,spokane ,m\nt ,ra9i] ,m\nt ,/4 ,hel5s ,m\nt ,adams ,,montana ,great ,falls ,bill+s ,,idaho ,boise ,crat]s ( ! ,moon ,,oregon ,portl& ,m\nt ,hood ,m\nt ,jeff]son ,?ree ,si/]s ,eug5e ,newb]ry ,crat] ,crat] ,lake ,,wyom+ ,yell[/one ,casp] ,*ey5ne ,,cali=nia ,m$ic9e ,lake ,m\nt ,%a/a ,lass5 ,peak ,cle> ,lake ,sacram5to ,san ,francisco ,long ,valley ,cald]a ,coso ,los ,angeles ,san ,diego ,,nevada ,r5o ,las ,vegas ,,utah ,salt ,lake ,city ,,colorado ,d5v] ,,arizona ,san ,francisco ,field ,pho5ix ,tucson ,,new ,,mexico ,albuqu]que ,b&]a ,field ,^! magmas are s highly visc\s1 or /icky1 t exp&+ volcanic gases _c easily escape f !m4 ,?is causes a trem5d\s build-up 9 pressure1 (t5 lead+ to extremely explosive eruptions4 ,dur+ su* eruptions1 magma is %att]$ into t9y fragm5ts 7*iefly a% & pumice7 & eject$ ?\s&s ( met]s into ! atmosph]e or ev5 ! /ratosph]e4 ,"u ! =ce ( gravity1 sometimes ^! fragm5ts sweep d[n a volcano's flanks at spe$s ( m ?an #ajj kilomet]s p] h\r1 mix+ ) air & volcanic gases to =m pyrocla/ic fl[s4 ,rock fragm5ts c also mix ) wat] 9 riv] valleys to =m lah>s 7volcanic debris fl[s & mudfl[s7 t de/roy ev]y?+ 9 _! pa?s4 ,&esite & dacite magmas also erupt to =m lava fl[s4 ,because ^! lavas are m visc\s 78/icki]07 ?an basalt1 !y t5d to =m ?ick] fl[s t travel %ort] di/ances f ! v5t2 consequ5tly1 &esite & dacite lavas typically build tall cones ) /eep slopes ( m ?an #bj degrees4 ,illu/ration3 ,mt4 ,hood1 ,oregon4 ,eruptions f ! volcano ab\t #a1hjj & #bjj ye>s ago f ! ,crat] ,rock lava dome =m$ a broad apron ( rock debris on ! volcano's s\? side4 7,photograph by ,lyn ,top9ka47 ,m\nt ,bak]1 ,wa%+ton4 ,eyewitness reports ( small a%y plumes & active /eam v5ts on ,m\nt ,bak] dat+ z f> back z ! mid-#ahjj's 7 cle> evid5ce t ! ice-cov]$ volcano _h "o ( ! mo/ active geo!rmal sy/ems among ,cascade volcanoes4 ,:5 new fum>oles & unusually d>k vapor plumes appe>$ abruptly 9 ,m>* #aige1 h[ev]1 p 9 ! ,nor?we/ became conc]n$ ab\t an imp5d+ eruption & possible avalan*es & lah>s f ,%]man ,crat]1 a v5t j s\? ( ,m\nt ,bak]'s summit4 ,despite a t5fold increase 9 ! release ( heat by ! volcano dur+ ! next #ab mon?s1 :i* result$ 9 ext5sive *anges to ! ice cov] 9 ,%]man ,crat] & produc$ m9or releases ( a%1 no eruption occurr$4 ,! !rmal activity 0 n accompani$ by e>?quakes1 :i* g5]ally prec$e mo/ eruptions1 & s9ce #aigf1 ! volcano has n %[$ additional signs ( activity4 ,illu/ration3 ,m\nt ,bak] view$ to ! we/4 ,increas$ fum>olic activity occurr$ 9 ,%]man ,crat] 7left ( summit7 dur+ ! mid-#aigj's4 ,! increas$ !rmal activity betwe5 #aige & #aigf prompt$ public (ficials & ,puget ,p[] to tempor>ily close public access to ! popul> ,bak] ,lake recreation area & to l[] ! res]voir's wat] level by #aj met]s4 ,significant avalan*es ( debris f ! ,%]man ,crat] area c\ld h swept directly into ! res]voir1 trigg]+ a disa/r\s wave t w\ld h caus$ loss ( life & damage to ! res]voir4 ,illu/ration3 ,m\nt ,ra9i] t[]s #c1jjj met]s above ! surr\nd+ valleys1 all ( :i* h be5 swept by lah>s dur+ ! pa/ #aj1jjj ye>s4 ,future eruptions w probably trigg] simil> lah>s4 7,photograph by ,david ,wiepre*t47 ,m\nt ,ra9i]1 ,wa%+ton4 ,m\nt ,ra9i] has n produc$ a significant eruption 9 ! pa/ #ejj ye>s1 b sci5ti/s consid] x to be "o ( ! mo/ haz>d\s volcanoes 9 ! ,cascades4 ,m\nt ,ra9i] has #bf glaci]s conta9+ m ?an five times z mu* sn[ & ice z all ! o!r ,cascade volcanoes comb9$4 ,if only a small "p ( ?is ice 7 melt$ by volcanic activity1 x w\ld yield en\gh wat] to trigg] enorm\s lah>s4 ,m\nt ,ra9i]'s pot5tial = g5]at+ de/ructive mudfl[s is enhanc$ by its great height above surr\nd+ valleys & its 8s(t0 int]ior4 ,! volcano /&s ab\t #c1jjj met]s above riv] valleys lead+ f its base4 ,volcanic heat & gr\nd wat] h turn$ "s ( ! volcano's orig9ally h>d lava into s(t clay m9]als1 !reby weak5+ its int]nal /ructure4 ,^! conditions make ,m\nt ,ra9i] extremely susceptible to l>ge l&slides4 ,sev]al h occurr$ 9 ! pa/ few ?\s& ye>s1 "o z rec5tly z ab\t #fjj ye>s ago4 ,^! l&slides1 app>5tly conta9+ great volumes ( wat]1 quickly turn$ into lah>s z !y ru%$ d[n riv] valleys4 ,m\nt ,/4 ,hel5s1 ,wa%+ton4 ,! cata/rophic eruption on ,may #ah1 #aihj1 0 prec$$ by #b mon?s ( int5se activity t includ$ m ?an #aj1jjj e>?quakes1 hundr$s ( small phreatic 7/eam-bla/7 explosions1 & ! outw>d gr[? ( ! volcano's entire nor? flank by m ?an #hj met]s4 ,a magnitude #e4a e>?quake /ruck b5ea? ! volcano at #jh3cb on ,may #ah1 sett+ 9 motion ! deva/at+ eruption4 ,illu/ration3 ,m\nt ,/4 ,hel5s crat] & lava dome view$ f ! nor?1 #aiij4 ,inset3 ,close view ( lava dome ) new lava extrusion on top 7sn[-free "p7 f ! s\?1 #aihf4 7,photographs by ,lyn ,top9ka47 ,)9 seconds ( ! e>?quake1 ! volcano's bulg+ nor? flank slid away 9 ! l>ge/ l&slide 9 record$ hi/ory1 trigg]+ a de/ructive1 le?al lat]al bla/ ( hot gas1 /eam1 & rock debris t swept across ! l&scape z fa/ z #a1ajj kilomet]s p] h\r4 ,temp]atures )9 ! bla/ rea*$ z high z #cjj degrees ,celsius4 ,sn[ & ice on ! volcano melt$1 =m+ torr5ts ( wat] & rock debris t swept d[n riv] valleys lead+ f ! volcano4 ,)9 m9utes1 a massive plume ( a% ?ru/ #ai kilomet]s into ! sky1 :]e ! prevail+ w9d c>ri$ ab\t #ebj million tons ( a% across #eg1jjj squ>e kilomet]s ( ! ,we/]n ,unit$ ,/ates4 ,illu/ration3 ,/& ( timb] 9 ! process ( be+ h>ve/$ 0 in/ead knock$ ov] by ! lat]al bla/4 ,an e/imat$ #d million bo>d feet ( timb] 0 de/roy$4 7,photograph by ,h4,h4 ,kieff]47 ,illu/ration3 ,small eruption ( gas & a% f ! lava dome caus$ by viol5t release ( volcanic gas or ! geys]-l fla%+ ( sup]hot gr\nd wat] to /eam4 7,photograph by ,dan ,dzuris947 ,illu/ration3 ,m\nt ,/4 ,hel5s t[]s above ! *aotic l&slide deposit t fills a =m] valley to a dep? ( z mu* z #aie met]s4 ,note _m small hills atop ! l&slide1 call$ 8hummocks0 by geologi/s4 7,photograph by ,lyn ,top9ka47 ,! well-docum5t$ l&slide at ,m\nt ,/4 ,hel5s has help$ geologi/s to recognize m ?an #bjj simil> deposits at o!r volcanoes 9 ! _w1 includ+ sev]al o!r ,cascade peaks4 ,geologi/s n[ realize t l>ge l&slides f volcanoes are f> m common ?an previ\sly ?\ght--sev5te5 su* volcanic l&slides h occurr$ worldwide 9 ! pa/ #djj ye>s4 ,consequ5tly1 :5 sci5ti/s evaluate ! types ( volcanic activity t may endang] p1 giant l&slides are n[ includ$1 9 addition to o!r types ( volcanic activity su* z lava fl[s1 pyrocla/ic fl[s1 lah>s1 & fall+ a%4 ,foll[+ ! #aihj explosive eruption1 m ?an a doz5 extrusions ( ?ick1 pa/y lava built a m\nd-%ap$ lava dome 9 ! new crat]4 ,! dome is ab\t #a1ajj met]s 9 diamet] & #bej met]s tall4 ,illu/ration3 ,giant mu%room-%ap$ a% cl\d ( ,may #bb1 #aiae1 view$ f #hj kilomet]s we/ ( ,lass5 ,peak4 7,photograph provid$ by ,national ,p>k ,s]vice47 ,lass5 ,peak1 ,cali=nia4 ,long be=e ! rec5t activity ( ,m\nt ,/4 ,hel5s1 a s]ies ( spectacul> eruptions f ,lass5 ,peak betwe5 #aiad & #aiag demon/rat$ ! explosive pot5tial ( ,cascade volcanoes4 ,small phreatic explosions began on ,may #cj1 #aiad1 & 7 foll[$ dur+ ! next #ab mon?s by m ?an #aej explosions t s5t cl\ds ( a% z high z #c kilomet]s above ! peak4 ,! activity *ang$ "* 9 ,may #aiae1 :5 a lava fl[ 0 obs]v$ 9 ! summit crat]4 ,a deep r$ gl[ f ! hot lava 0 visible at night #cd kilomet]s away4 ,on ,may #ai1 an avalan*e ( hot rocks f ! lava spill$ onto sn[ & trigg]$ a lah> t ext5d$ m ?an #ae kilomet]s f ! volcano4 ,! mo/ de/ructive explosion occurr$ on ,may #ba1 :5 a pyrocla/ic fl[ deva/at$ =e/s z f> z #f4e kilomet]s nor!a/ ( ! summit & lah>s swept d[n sev]al valleys radiat+ f ! volcano4 ,an enorm\s a% plume rose m ?an #i kilomet]s above ! peak1 & ! prevail+ w9ds scatt]$ ! a% across ,nevada z f> z #ejj kilomet]s to ! ea/4 ,lass5 ,peak cont9u$ to produce small] eruptions until ab\t ! middle ( #aiag4 ,alaskan volcanoes ,! ,alaska ,p59sula & ! ,aleutian ,isl&s h ab\t #hj major volcanic c5t]s t consi/ ( "o or m volcanoes4 ,rec5t viol5t eruptions h demon/rat$ t volcanic haz>ds d exi/ 9 "s areas ( ,alaska1 ev5 ?\gh x is sp>sely populat$4 ,alaskan volcanoes h produc$ "o or two eruptions p] ye> s9ce #aijj4 ,at lea/ #bj cata/rophic cald]a-=m+ eruptions h occurr$ 9 ! pa/ #aj1jjj ye>s2 ! awesome eruption ( #aiab at ,nov>upta 9 ! ,katmai ,national ,monum5t is ! mo/ rec5t4 ,sci5ti/s are p>ticul>ly conc]n$ ab\t ! volcanoes ^: eruptions c affect ! ,cook ,inlet region1 :]e #fj p]c5t ( ,alaska's population lives4 ,illu/ration3 ,alaskan volcanoes4 ,,explanation ,volcano active dur+ pa/ #b1jjj ye>s ,population c5t] #ajj1jjj to #cej1jjj ,,alaska ,wrangell ,hayes ,an*orage ,spurr ,r$\bt ,iliamna ,akutan ,nov>upta ,augu/9e ,cook ,inlet ,trid5t ,bogosl( ,uk9rek ,m>t9 ,mageik ,kagamil ,*ig9agak ,uga%ik-,peulik ,c>lisle ,emmons ,lake ,yantami ,kiska ,c]b]us ,fi%] ,dutton ,aniak*ak ,v5iam9( ,little ,sitk9 ,kasato*i ,amukta ,pyre ,pavl( ,isanotski ,we/dahl ,%i%ald9 ,maku%9 ,g>eloi ,vsevid( ,okmok ,tanaga ,korov9 ,clevel& ,kanaga ,great ,sitk9 ,yunaska ,illu/ration3 ,r$\bt ,volcano1 ,alaska1 erupt+ on ,decemb] #af1 #aihi4 7,photograph by ,national ,p>k ,s]vice47 ,r$\bt ,volcano4 ,r$\bt ,volcano erupt$ = ! f\r? "t ?is c5tury on ,decemb] #ad1 #aihi4 ,foll[+ sev]al days ( /rong explosive activity1 a s]ies ( lava domes grew 9 ,r$\bt's summit crat] dur+ ! next f\r mon?s4 ,mo/ ( ! domes 7 de/roy$ by explosions or collaps$ d[n ! volcano's nor? flank4 ,"s ( ^! ev5ts trigg]$ small pyrocla/ic fl[s t melt$ sn[ & ice on ! volcano to =m lah>s 9 ,drift ,riv] ,valley1 :i* empties into ,cook ,inlet #ce kilomet]s away4 ,a% produc$ by ! eruptions sev]ely affect$ air traffic enr\te to ,an*orage1 ,alaska's l>ge/ city & a major hub ( dome/ic & int]national comm]cial air traffic4 ,_m dome/ic c>ri]s susp5d$ s]vice to ,alaska foll[+ major explosive ev5ts1 & sev]al int]national c>ri]s tempor>ily r]\t$ flights ar\nd ,alaska4 ,on ,decemb] #ae1 a jetl9] enr\te to ,japan enc\nt]$ an a% cl\d :ile desc5d+ into ,an*orage4 ,! plane quickly lo/ p[] 9 all f\r eng9es & lo/ #d1jjj met]s 9 altitude be=e ! pilots 7 able to re/>t ! eng9es4 ,! aircraft l&$ safely 9 ,an*orage1 b x su/a9$ m ?an #hj million 9 damage4 ,illu/ration3 ,lava dome 9 ! summit crat] ( ,r$\bt ,volcano1 :i* grew betwe5 ,april #ba & ,june #aiij4 7,photograph by ,david ,wiepre*t47 ,lah>s g5]at$ dur+ ! eruption ?reat5$ an oil-/orage facility locat$ on ! banks ( ,drift ,riv]4 ,oil is pump$ f m ?an a doz5 wells 9 ,cook ,inlet to ! facility & !n load$ onto tank]s1 :i* dock j (f%ore4 ,a lah> on ,janu>y #b flood$ "p ( ! facility ) ne>ly a met] ( wat]1 =c+ its %utd[n until work]s c\ld re/ore p[]4 ,?is & subsequ5t lah>s prompt$ ! ,cook ,inlet ,pipel9e ,company to tempor>ily halt oil production f "s oil wells & r$uce ! am\nt ( oil /or$ at ! facility betwe5 tank] load+s4 ,illu/ration3 ,rock f ! lava dome ( ,r$\bt ,volcano deposit$ 9 a riv] valley by a lah> dur+ an eruption on ,janu>y #h1 #aiij4 ,:5 f\nd #f days lat]1 ! temp]ature ( ! rock 0 /ill #ade;,c4 7,photograph by ,c4 ,dan ,mill]47 ,illu/ration3 ,/eam plume rises f lava dome atop ,augu/9e ,volcano on ,april #cj1 #aihf4 7,photograph by ,m4,e4 ,y\nt47 ,augu/9e ,volcano4 ,"o ( ! mo/ active volcanoes 9 ,cook ,inlet is ,augu/9e1 ^: symmetrical cone rises #a1bed met]s above ! sea4 ,s9ce ,capta9 ,james ,cook discov]$ & nam$ x 9 #aggh1 ,augu/9e has erupt$ 9 #ahab1 #ahhc1 #aice1 #aifc-fd1 #aigf1 & #aihf4 ,curi\sly1 ! quiet int]vals betwe5 ^! eruptions app>5tly h %ort5$ f #gj to #aj ye>s4 ,augu/9e's #aihf eruption 0 simil> to ! patt]n ( ev5ts obs]v$ 9 #aigf4 ,aft] eight mon?s ( e>?quake activity b5ea? ! volcano1 a viol5t explosion began on ,m>* #bf4 ,bill[+ a% plumes rose m ?an #aj kilomet]s above ! v5t1 pyrocla/ic fl[s sp$ d[n ! volcano's flanks into ! sea1 & a% spread ?r\gh\t ,cook ,inlet4 ,a second /age began ,april #bc1 :5 lava began erupt+ ne> ! volcano's summit & add$ ab\t #be met]s to ! top ( ! exi/+ lava dome4 ,small pyrocla/ic fl[s accompani$ gr[? ( ! dome4 ,sci5ti/s 7 worri$ t ?is eruption might trigg] a giant l&slide f ,augu/9e's /eep upp] cone1 :i* c\ld ent] ! sea to create a tsunami 7p[]ful seismic sea wave74 ,at lea/ #ab l&slides are kn[n to h occurr$ at ,augu/9e4 ,! mo/ rec5t slide took place at ! onset ( ! #ahhc eruption :5 a "p ( ! volcano's summit collaps$ into ! sea4 ,)9 "o h\r1 a tsunami z high z #i met]s cra%$ a%ore on ! coa/ ( ! ,k5ai ,p59sula #hj kilomet]s away4 ,no "o 0 kill$ & prop]ty damage 0 only m9or because ! tsunami hit at l[ tide4 ,subsequ5t eruptions h rebuilt a /eep cone ( ov]lapp+ lava domes simil> to ! cone t exi/$ j be=e ! #ahhc l&slide4 ,illu/ration3 ,pyrocla/ic fl[ desc5d+ ! upp] flanks ( ,augu/9e ,volcano4 7,photograph by ,m4,e4 ,y\nt47 ,nov>upta1 ,katmai ,national ,monum5t4 ,! l>ge/ eruption 9 ! _w ?is c5tury occurr$ 9 #aiab at ,nov>upta on ! ,alaska ,p59sula4 ,an e/imat$ #ae cubic kilomet]s ( magma 0 explosively erupt$ dur+ #fj h\rs beg9n+ on ,june #f--;ab\t #cj times ! volume erupt$ by ,m\nt ,/4 ,hel5s 9 #aihj6 ,! expulsion ( su* a l>ge volume ( magma excavat$ a funnel-%ap$ v5t #b kilomet]s wide & trigg]$ ! collapse ( ,m\nt ,katmai volcano #aj kilomet]s away to =m a summit cald]a #fjj met]s deep & ab\t #c kilomet]s across4 ,extrusion ( ! lava dome1 call$ ,nov>upta1 ne> ! c5t] ( ! #aiab v5t m>k$ ! end ( ! eruption4 ,little 0 kn[n ab\t ! spectacul> effects ( ?is great eruption until #aiaf1 :5 a sci5tific exp$ition sponsor$ by ! ,national ,geographic ,society visit$ ! area4 ,to _! amazem5t1 !y f\nd a broad valley nor?we/ ( ,nov>upta m>k$ by a flat pla9 ( loose1 8s&y0 a% mat]ial f :i* ?\s&s ( jets ( /eam 7 hiss+4 ,! eruption _h produc$ pyrocla/ic fl[s t swept ab\t #ba kilomet]s d[n ! upp] ,ukak ,riv] valley4 ,! ?ickness ( ! result+ pumice & a% deposits 9 ! upp] valley is n kn[n b may be z great z #bjj met]s4 ,9 #aiaf1 ! deposits 7 /ill hot en\gh to boil wat] & =m c\ntless /eam+ fum>oles2 h5ce ! exp$ition nam$ ?is "p ( ! ,ukak ,riv] ! 8,valley ( ,t5 ,?\s& ,smokes40 ,trid5t ,volcano4 ,eruptions ( &esitic lava fl[s betwe5 #aiec & #aifj built a new cone on ,trid5t's s\?we/ flank1 add+ yet ano!r to ! volcano's old] complex ( ?ree ov]lapp+ cones 7h5ce ! "n ,trid5t74 ,a huge cl\d ( ris+ a% 0 se5 on ,febru>y #ae1 #aiec1 9 ! direction ( ,katmai ,national ,monum5t2 #c days lat] cle> wea!r p]mitt$ ,u4,s4 ,navy pilots to spot a blocky lava fl[ em]g+ f ,trid5t's s\?we/ flank4 ,sl[ extrusion ( lava dur+ ! next #d mon?s built an irregul>ly %ap$ lava dome ab\t #a4e kilomet]s long & #fjj met]s tall4 ,trid5t cont9u$ to erupt int]mitt5tly ?r\gh #aifj1 g5]at+ ?ree lava fl[s z long z #d4e kilomet]s f ! same v5t & num]\s a%-produc+ explosive eruptions4 ,illu/ration3 ,nov>upta lava dome1 ,mt4 ,katmai1 & ,trid5t ,volcano1 ,alaska4 ,! dome is #chj met]s 9 diamet] & occupies a small "p ( ! v5t f :i* ab\t #ae cubic kilomet]s ( magma 0 erupt$ 9 #aiab 7da%$ l9e m>ks approximate outl9e ( v5t74 7,copyright$ photograph repr9t$ ) p]mission1 ,a]o ,map ,,u ,inc41 ,augu/ #ba1 #aihg47 ,illu/ration3 ,small /eam plume rises f a c9d] cone )9 ! summit cald]a ( ,m\nt ,v5iam9(1 ,alaska4 ,! l>ge pit 9 ! ice =m$ :5 lava 7d>k area7 fl[$ b5ea? ! ice & melt$ x4 7,photograph by ,m4,e4 ,y\nt47 ,m\nt ,v5iam9(4 ,m\nt ,v5iam9( is a massive composite volcano ) a summit cald]a ab\t #h kilomet]s 9 diamet]4 ,s9ce its =mation ab\t #c1gjj ye>s ago1 ! cald]a has fill$ ) ice to a dep? ( at lea/ #fj met]s4 ,betwe5 ,june #aihc & ,janu>y #aihd1 a s]ies ( small explosions1 lava f\nta9s1 & lava fl[s erupt$ f a small c9d] cone )9 ! cald]a4 ,! explosions hurl$ molt5 lava f ! c9d] cone1 & lava fl[s melt$ a pit ab\t #a4e kilomet]s 9 diamet] 9 ! ice ne> ! base ( ! volcano4 ,wat] f ! melt+ ice =m$ a tempor>y lake4 ,m\nt ,spurr4 ,! summit cone ( ,m\nt ,spurr consi/s ( a l>ge lava dome built 9 ! c5t] ( a horse%oe-%ap$ crat] =m$ e>li] by a l>ge l&slide4 ,at ! s\!rn edge ( ?is anci5t crat] is a y\ng]1 m active cone kn[n z ,crat] ,peak4 ,sci5ti/s h det]m9$ t ,crat] ,peak is ! s\rce = at lea/ #ce a% lay]s f\nd 9 ! ,cook ,inlet area1 all ( :i* 7 erupt$ 9 ! pa/ #f1jjj ye>s4 ,until rec5tly1 a w>m turquoise-color$ lake p>tially fill$ its crat]4 ,a s]ies ( explosive eruptions f ,crat] ,peak on ,june #bg1 #aiib1 g5]at$ a% plumes z high z ab\t #ad kilomet]s1 small pyrocla/ic fl[s t swept d[n ! s\? & ea/ sides ( ! cone1 & small lah>s4 ,! reawak5+ ( ,crat] ,peak foll[$ ne>ly a ye> ( increas$ e>?quake activity1 :i* escalat$ fur!r on ,june #bf1 less ?an #a day be=e its fir/ eruption4 ,n all ( ! explosive episodes 7 prec$$ by a *ange 9 seismicity b5ea? ! volcano1 a condition t requir$ sci5ti/s to ma9ta9 a #bd-;h\r wat* = ext5d$ p]iods ( "t 9 ord] to issue sudd5 reports & w>n+s ( eruptive activity4 ,! we/ side ( ,cook ,inlet receiv$ a light to mod]ate a%fall dur+ ! l>ge/ explosive episode on ,augu/ #ah2 ,an*orage 0 blanket$ ) ab\t #c millimet]s ( a%1 caus+ ! ,an*orage ,int]national ,airport to close = a few h\rs4 ,dur+ an eruption at night on ,septemb] #ag1 a spectacul> display ( lightn+ & inc&esc5t balli/ics & pyrocla/ic fl[s 7 witness$ by hunt]s :o camp$ ab\t #ah kilomet]s to ! s\!a/2 a fa9t gl[ above ,crat] ,peak 0 also visible f z f> away z ,an*orage4 ,illu/ration3 ,/eam+ ,crat] ,peak1 a satellite v5t on ! s\? side ( ,m\nt ,spurr volcano1 produc$ ?ree explosive eruptions 9 #aiib4 7,photograph by ,cyn?ia ,g>dn]47 ,illu/ration3 ,a]ial view ( ! ,mono-,inyo ,crat]s ,volcanic ,*a91 ,cali=nia4 ,sev]al eruptions occurr$ along bo? *a9s z rec5tly z ab\t #eej to #fjj ye>s ago4 7,photograph by ,c4 ,dan ,mill]47 ,mono ,crat]s ,wilson ,butte ,nor!rn "p ( ,inyo ,volcanic ,*a9 ,obsidian ,dome ,glass ,creek ,dome ,re/less cald]as ,! l>ge/ & mo/ explosive volcanic eruptions eject t5s to hundr$s ( cubic kilomet]s ( magma onto ! ,e>?'s surface4 ,:5 su* a l>ge volume ( magma is remov$ f b5ea? a volcano1 ! gr\nd subsides or collapses into ! empti$ space1 to =m a huge depression call$ a cald]a4 ,"s cald]as are m ?an #be kilomet]s 9 diamet] & sev]al kilomet]s deep4 ,cald]as are among ! mo/ spectacul> & active volcanic features on ,e>?4 ,e>?quakes1 gr\nd cracks1 uplift or subsid5ce ( ! gr\nd1 & !rmal activity su* z hot spr+s1 geys]s1 & boil+ mud pots are common at _m cald]as4 ,su* activity is caus$ by complex int]actions among magma /or$ b5ea? a cald]a1 gr\nd wat]1 & ! regional build-up ( /ress 9 ! l>ge plates ( ! ,e>?'s cru/4 ,significant *anges 9 ! level ( activity at "s cald]as are common2 ^! new activity levels c be int]mitt5t1 la/+ = mon?s to ye>s1 or p]si/5t ov] decades to c5turies4 ,al?\gh mo/ cald]a unre/ does n lead to an eruption1 ! possibility ( viol5t explosive eruptions w>rants detail$ sci5tific /udy & monitor+ ( "s active cald]as4 ,rec5tly1 sci5ti/s h recogniz$ volcanic unre/ at two cald]as 9 ! ,unit$ ,/ates1 ,long ,valley ,cald]a 9 ea/]n ,cali=nia & ,yell[/one ,cald]a 9 ,yell[/one ,national ,p>k1 ,wyom+4 ,:e!r unre/ at ^! cald]as simply punctuates long p]iods ( quiet or is ! e>ly w>n+ sign ( future eruptions is an important b /ill unansw]$ "q4 ,illu/ration3 ,yell[/one ,riv] plummets ?r\gh ! fam\s ,gr& ,canyon ( ,yell[/one4 ,c>v$ by ! riv]1 ! 8yell[0 rocks ( ! canyon are rhyolite lava fl[s t h be5 alt]$ by hot wat]4 ,! lava fl[s 7 erupt$ aft] ! mo/ rec5t cald]a-=m+ eruption ab\t #fjj1jjj ye>s ago4 ,long ,valley ,cald]a1 ,cali=nia4 ,long ,valley ,cald]a lies on ! ea/]n front ( ! ,si]ra ,nevada1 ab\t #cjj kilomet]s ea/ ( ,san ,francisco4 ,a huge explosive eruption ab\t #gjj1jjj ye>s ago =m$ ! cald]a & produc$ pyrocla/ic fl[s t travel$ #fe kilomet]s f ! v5t & cov]$ an area ( ab\t #a1ejj squ>e kilomet]s4 ,a% f ! cald]a-=m+ eruption fell z f> ea/ z ,nebraska4 ,)9 ! pa/ #dj1jjj ye>s1 eruptions h be5 re/rict$ to a l9e> zone ( v5ts1 includ+ ! ,mono-,inyo ,crat]s ,volcanic ,*a91 t ext5ds ab\t #ej kilomet]s nor? f ! nor?we/ "p ( ! cald]a4 ,?is volcanic *a9 consi/s ( _m v5ts t h erupt$ 9 ! pa/ sev]al ?\s& ye>s4 ,eruptions f v5ts z rec5tly z #eej ye>s ago produc$ lava fl[s1 pyrocla/ic fl[s1 & a%1 all ( rhyolitic composition4 ,geologic mapp+ %[s t "s eruptions 7 prec$$ by gr\nd crack+1 sugge/+ t ! gr\nd 0 pull$ ap>t or /ret*$ z magma ne>$ ! surface4 ,illu/ration3 ,sket* ( ,long ,valley ,cald]a & ! ,mono-,inyo ,crat]s ,volcanic ,*a9 9 c5tral ,cali=nia1 view$ f ! s\!a/4 7,sket* by ,tau ,rho ,alpha47 ,si]ra ,nevada ,mono crat]s ,inyo crat]s ,mammo? ,lakes ,resurg5t dome ,long ,valley ,cald]a ,?ree mod]ate e>?quakes s\? ( ! cald]a & "o b5ea? ! cald]a on ,may #be-bf1 #aihj1 m>k$ ! beg9n+ ( unre/ t cont9ues into ! #aiij's4 ,sw>ms ( e>?quakes b5ea? ! cald]a1 *anges 9 sev]al hot spr+s1 & ! =mation ( new spr+s h occurr$ s9ce #aihj4 ,precise surveys h also %[n t ! c5tral "p ( ! cald]a has ris5 by m ?an #ej c5timet]s s9ce #aige4 ,?is unre/ is probably relat$ to ! /ret*+ 7ea/-we/ ext5sion7 ( ! ,e>?'s cru/ t is kn[n to be occurr+ 9 ! region ar\nd ! cald]a1 & x probably also involves ! rise ( magma b5ea? ! cald]a4 ,sci5ti/s d n "k if ?is unre/ w lead to volcanic activity1 b ! geologically rec5t eruptions along ! ,mono-,inyo ,crat]s ,volcanic ,*a9 sugge/ t future eruptions are possible4 ,illu/ration3 ,s\? ,inyo ,crat]1 ,long ,valley ,cald]a1 ,cali=nia4 ,explosive eruptions =m$ ! crat] ab\t #ejj ye>s ago4 7,photograph by ,/ev5 ,r4 ,brantley47 ,yell[/one ,cald]a1 ,yell[/one ,national ,p>k1 ,wyom+4 ,yell[/one ,cald]a is "o ( ! l>ge/ & mo/ active cald]as 9 ! _w4 ,! spectacul> geys]s1 boil+ hot spr+s1 & mud pots t h made ,yell[/one fam\s--& ev5 ! /rik+ly beautiful ,gr& ,canyon ( ,yell[/one ?r\gh :i* ! ,yell[/one ,riv] plunges--owe _! exi/5ce to ! trem5d\s volcanic =ces t h affect$ ! region dur+ ! pa/ #b million ye>s4 ,cataclysmic eruptions #b4j1 #a4c1 & #j4f million ye>s ago eject$ huge volumes ( rhyolite magma2 ea* eruption =m$ a cald]a & ext5sive lay]s ( ?ick pyrocla/ic-fl[ deposits4 ,! y\nge/ cald]a is an elliptical depression1 ne>ly #hj kilomet]s long & #ej kilomet]s wide1 t occupies mu* ( ,yell[/one ,national ,p>k4 ,! cald]a is buri$ by sev]al ext5sive rhyolite lava fl[s erupt$ betwe5 #ge1jjj & #aej1jjj ye>s ago4 ,illu/ration3 ,map ( mo/ rec5t ,yell[/one ,cald]a & its ma9 !rmal features4 ,aft] ! cald]a =m$1 _m v5ts erupt$ ?ick rhyolite lava fl[s1 & ! c5tral "p ( ! cald]a 0 pu%$ upw>d to =m resurg5t domes4 ,! /> m>ks ! magnitude #g4e ,hebg] ,lake e>?quake4 ,,idaho ,hebg5 ,lake ,we/ ,yell[/one ,,montana ,silv] ,gate ,g>d9] ,,wyom+ ,yell[/one ,national ,p>k ,mammo? ,m #g4e ,aug4 #ah #aiei ,norris ,geys] ,bas9 ,mud ,pots ,old ,fai?ful ,we/ ,?umb ,geys] ,bas9 ,yell[/one ,lake ,,cald]a ,,rim ,,colorado ,resurg5t dome ,! ,e>?'s cru/ b5ea? ,yell[/one ,national ,p>k is /ill re/less4 ,precise surveys h detect$ an area 9 ! c5t] ( ! cald]a t rose by z mu* z #hf c5timet]s betwe5 #aibc & #aihd & !n subsid$ slightly betwe5 #aihe & #aihi4 ,sci5ti/s d n "k ! cause ( ^! ups & d[ns b hypo!size t !y are relat$ to ! addition or )drawal ( magma b5ea? ! cald]a1 or to ! *ang+ pressure ( ! hot gr\nd wat] sy/em above ,yell[/one's l>ge magma res]voir4 ,also1 ,yell[/one ,national ,p>k & ! area imm$iately we/ ( ! ,p>k are hi/orically among ! mo/ seismically active areas 9 ! ,rocky ,m\nta9s4 ,small-magnitude e>?quakes are common b5ea? ! entire cald]a1 b mo/ are locat$ along ! ,hebg5 ,lake fault zone t ext5ds into ! nor?we/ "p ( ! cald]a4 ,a magnitude #g4e e>?quake occurr$ along ?is zone 9 #aiei4 ,illu/ration3 ,ca/le ,geys] erupt+ a column ( hot wat]1 ,yell[/one ,national ,p>k4 7,photograph by ,/ev5 ,r4 ,brantley47 ,active ,volcanoes3 ,w9d[s ,into ! ,pa/ ,molt5 rock has erupt$ onto ! surface ( ! ,e>? ?r\gh\t its #d4e-;billion-ye> hi/ory4 ,al?\gh _m ( ^! anci5t rocks 7 remov$ by erosion1 volcanic deposits c be f\nd b5ea? y\ng] rocks 9 _m p>ts ( ! ,unit$ ,/ates4 ,to a geologi/1 su* long-la/+ volcanic rocks look l ^? =m$ by today's active volcanoes4 ,_m anci5t volcanic rocks1 h[ev]1 *ange some:at ) "t1 z !y become firmly consolidat$1 buri$ by y\ng] deposits1 & sometimes fold$ & fault$ by ! cont9u\s %ift+ ( ! ,e>?'s cru/4 ,ev5 m9]als ( volcanic rocks may *ange1 if aft] burial !y enc\nt] high pressures & temp]atures4 ,illu/ration3 ,column> jo9t+ 9 an anci5t lava fl[ 9 ! ,blue ,ridge ,m\nta9s1 ,%5&oah ,national ,p>k1 ,virg9ia4 ,! fl[ t conta9s ! columns is "o ( an ext5sive s]ies ( lava fl[s1 ea* av]ag+ ab\t #bjj feet ?ick1 t p\r$ ov] ! l& m ?an #egj million ye>s ago4 ,columns =m z cool+ or %r9kage jo9ts :5 a hot lava fl[ cools quickly2 ! columns =m p]p5dicul> to ! cool+ surface4 ,^! columns are ab\t 4#e met] 9 diamet]4 7,photograph by ,j4,c4 ,re$1 ,jr47 ,mo/ active volcanoes are built on old] volcanic deposits erupt$ f anci5t volcanoes1 & visitors to ! pres5t-day volcanoes walk or drive across ^! products ( pa/ volcanism4 ,= example1 anyone driv+ across ! ,cascade ,range1 sunba?+ at ,waikiki1 or fi%+ on ! ,alaska ,p59sula is !re because old volcanic rocks =m ! l&scape4 ,"o /ep fur!r back 9 "t f today's active volcanoes are p :o picnic 9 ! ,:ite ,m\nta9s ( ,new ,hamp%ire1 enjoy ! autumn colors 9 ! ,blue ,ridge ( ,%5&oah ,national ,p>k1 & hike 9 ! rugg$ ,big ,b5d ,national ,p>k ( ,texas4 ,_m ( ! rocks 9 ^! areas 7 =m$ by eruptions or by intrusion ( magma into ! ,e>?'s cru/ _m millions ( ye>s ago4 ,because volcanic activity has be5 s important 9 %ap+ ! ,e>?1 wat*+ active volcanoes today provides a w9d[ ?r\gh :i* we c glimpse & recon/ruct ! e>ly volcanic hi/ory ( our planet4 ,z we increase our k ab\t volcanic processes1 by /udy+ volcanoes erupt+ today z well z ^? t h la9 dormant = hundr$s to ?\s&s ( ye>s1 we increase our ability to pr$ict :5 & h[ volcanoes w erupt4 ,accurate pr$ictions1 pres5t$ 9 t]ms t are mean+ful to public (ficials1 w m9imize ! numb] ( lives lo/ & ! social & economic upheaval t an eruption c cause4 ,illu/ration3 ,?ick lay]s ( volcanic rocks =m ! ,sup]/ition ,m\nta9s1 locat$ ab\t #fj kilomet]s ea/ ( ,pho5ix1 ,arizona4 ,! consolidat$ deposits ( pyrocla/ic fl[s1 lava fl[s & domes1 & lah>s 9 ! ,sup]/ition ,m\nta9s & adjac5t areas te/ify to a p]iod ( int5se volcanism ab\t #ag to #be million ye>s ago 9 c5tral ,arizona4 7,photograph by ,d4,w4 ,pet]son47 ,gloss>y ,&esite ,a volcanic rock conta9+ #ec-fc silica ) a mod]ate viscosity :5 9 a molt5 /ate4 ,a% ,fragm5ts less ?an #b millimet]s 9 diamet] ( lava or rock bla/$ into ! air by volcanic explosions4 ,basalt ,a volcanic rock consi/+ ( less ?an #ec silica ) a l[ viscosity :5 9 a molt5 /ate4 ,cald]a ,a l>ge volcanic depression1 commonly circul> or elliptical :5 se5 f above4 ,composite ,a /eep-sid$ volcano compos$ ( _m lay]s ( volcano volcanic rocks1 usually ( high-viscosity lava & fragm5t$ debris su* z lah> & pyrocla/ic deposits4 ,dacite ,a volcanic rock conta9+ #fc-fh silica ) a high viscosity :5 9 a molt5 /ate4 ,dome ,a /eep-sid$ m\nd t =ms :5 visc\s lava piles up ne> a volcanic v5t4 ,domes are =m$ by &esite1 dacite1 & rhyolite lavas4 ,fum>ole ,a v5t t releases volcanic gases1 includ+ wat] vapor 7/eam74 ,lah> ,a fl[+ mixture ( wat] & rock debris t =ms on ! slopes ( a volcano1 sometimes ref]r$ to z debris fl[ or mudfl[4 ,! t]m comes f ,indonesia4 ,lava ,molt5 rock t erupts f a v5t or fissure2 see magma4 ,magma ,molt5 rock t conta9s dissolv$ gas & cry/als1 =m$ deep )9 ! ,e>?4 ,:5 magma rea*es ! surface1 x is call$ lava4 ,phreatic ,a type ( volcanic explosion t occurs :5 eruption wat] comes 9 contact ) hot rocks or a% ne> a volcanic v5t1 caus+ /eam explosions4 ,pumice ,a light-color$ volcanic rock conta9+ abundant trapp$ gas bubbles =m$ by ! explosive eruption ( magma4 ,because ( its num]\s gas bubbles1 pumice commonly floats on wat]4 ,pyrocla/ic fl[ ,a hot1 fa/-mov+ & high-d5sity mixture ( a%1 pumice1 rock fragm5ts1 & gas =m$ dur+ explosive eruptions4 ,pyrocla/ic ,same process z pyrocla/ic fl[ b ( mu* surge l[] d5sity4 ,rhyolite ,a volcanic rock conta9+ m ?an #fh silica ) a v high viscosity :5 9 a molt5 /ate4 ,%ield volcano ,a volcano %ap$ l an inv]t$ w>rior's %ield ) long g5tle slopes produc$ by eruptions ( l[-viscosity basaltic lava4 ,silica ,! molecule =m$ ( silicon & oxyg5 7,si,o7 t is ! basic build+ block ( volcanic rocks & ! mo/ important factor controll+ ! fluidity ( magma4 ,! high] a magma's silica cont5t1 ! great] its viscosity or 8/ick9ess40 ,v5t ,! op5+ at ! ,e>?'s surface ?r\gh :i* volcanic mat]ials 7magma & gas7 escape4 ,volcano ,a v5t 9 ! surface ( ! ,e>? ?r\gh :i* magma erupts & also ! l&=m t is con/ruct$ by ! erupt$ mat]ial4 ,volcanic ,! d[nslope movem5t ( soil1 rock debris1 & l&slide sometimes glacial ice1 ) or )\t wat]1 f ! flank ( a volcano4 ,illu/ration3 ,sci5ti/ survey+ lava dome at ,r$\bt ,volcano4 7,photograph by ,g4 ,mc,gimsey47 ,! metric units us$ 9 ?is publication c be conv]t$ to ,engli% units by us+ ! approximate conv]sions giv5 bel[3 ,l5g? #a kilomet] #j4f ( a mile #a met] #ci4cg in*es #a c5timet] #j4d in* #a millimet] #j4jd in* ,area #a sq4 kilomet] #j4d sq4 mile #a sq4 met] #a4b sq4 y>ds #a sq4 c5timet] #j4aee sq4 in* ,temp]ature ,to conv]t ,celsius to ,fahr5heit1 multiply ,c by #a4h & add #cb4 ,to conv]t ,fahr5heit to ,celsius1 subtract #cb f ,f & divide ! result by #a4h4 ,fur!r ,read+ ,deck]1 ,rob]t1 & ,deck]1 ,b>b>a1 #aihi1 ,volcanoes3 ,san ,francisco1 ,freeman1 #bhe p4 7,an in=mation-pack$ introduction to ! /udy ( volcanoes writt5 9 an easy-to-read /yle47 ,editors1 #aihb1 ,volcano3 9 ! s]ies ,planet ,e>?1 ,alex&ria1 ,virg9ia1 ,"t-,life ,books1 #agf p4 7,a well illu/rat$ & readable g5]al survey ( volcanoes & _! activity47 ,mc,clelland1 ,l9dsay1 ,simk91 ,tom1 ,summ]s1 ,m>jorie1 ,niels51 ,elizabe?1 & ,/e91 ,t4,c41 editors1 #aihi1 ,global ,volcanism #aige-aihe3 ,englewood ,cliffs1 ,new ,j]sey1 ,pr5tice-,hall1 #fef p4 7,a full acc\nt ( volcanism on ,e>? bas$ on eyewitness acc\nts f geologi/s & o!r sci5ti/s1 report]s1 travel]s1 & o!r ke5 obs]v]s47 ,simk91 ,tom1 & ,seib]t1 ,lee1 #aiid1 ,volcanoes ( ! ,_w 7,second edition73 ,/r\dsburg1 ,pa41 ,hut*9son ,ross1 #bcc p4 7,a compreh5sive regional directory ( worldwide volcanic activity dur+ ! pa/ #aj1jjj ye>s2 activity pres5t$ 9 table =mat47 ,till+1 ,r4 ,i41 #aihb1 ,volcanoes3 ,re/on1 ,virg9ia1 ,u4,s4 ,geological ,survey g5]al-int]e/ publication1 #df p4 7,a g5]al introduction = ! nonspeciali/ to ! /udy ( volcanoes1 ) focus on ! nature1 types1 work+s1 products1 & haz>ds ( volcanoes47 ,till+1 ,r4 ,i41 #aihd1 ,eruptions ( ,m\nt ,/4 ,hel5s3 ,pa/1 pres5t1 & future3 ,re/on1 ,virg9ia1 ,u4,s4 ,geological ,survey g5]al-int]e/ publication1 #df p4 7,a nonte*nical summ>y1 illu/rat$ by _m color photographs & diagrams1 ( ! abundant sci5tific data available = ! volcano1 ) emphasis on ! cata/rophic eruption on ,may #ah1 #aihj1 :i* caus$ ! wor/ volcanic disa/] 9 ,u4,s4 hi/ory47 ,till+1 ,r4 ,i41 #aihg1 ,eruptions ( ,hawaiian volcanoes3 ,pa/1 pres5t1 & future3 ,re/on1 ,virg9ia1 ,u4,s4 ,geological ,survey g5]al-int]e/ publication1 #ed p4 7,a nonte*nical summ>y1 illu/rat$ by color photographs & draw+s1 ( ! eruption hi/ory1 /yle1 & products ( two ( ,hawaii's active volcanoes1 ,kilauea & ,mauna ,loa47 ,wood1 ,c4 ,a41 & ,ki5le1 ,jurg51 editors1 #aiij1 ,volcanoes ( ,nor? ,am]ica--,unit$ ,/ates & ,canada3 ,cambridge ,univ]sity ,press1 #ced p4 7,a ri* compilation ( volcanoes & volcanic fields 9 ,nor? ,am]ica t 7 =m$ 9 ! pa/ #e million ye>s2 includes m ?an #bej entries prep>$ by lead+ exp]ts 9 volcanology47 ,u4,s4 ,geological ,survey ,in=mation ,s]vices ,p4,o4 ,box #bebhf ,d5v]1 ,,co #hjbbe ,u4,s4 ,,gov]nm5t ,,pr9t+ ,,(fice3 #aiif #dba-eee ,illu/ration3 ,front & back cov] 7clockwise f top photograph on front7 ,augu/9e ,volcano1 ,alaska1 #aihf4 ,illu/ration3 ,m\nt ,/4 ,hel5s1 ,wa%+ton1 #aihj4 ,illu/ration3 ,kilauea ,volcano1 ,hawaii1 #aihc4 ,illu/ration3 ,m\nt ,spurr1 ,alaska1 #aiib4 ,illu/ration3 ,mono-,inyo ,crat]s ,volcanic ,*a9 inside ,long ,valley ,cald]a1 ,cali=nia4 ,illu/ration3 ,u4 ,s4 ,,dep>tm5t ,,( ,,! ,,int]ior ,,m>* #c1 #ahdi ,z ! ,nation's pr9cipal cons]vation ag5cy1 ! ,dep>tm5t ( ! ,int]ior has responsibility = mo/ ( our nationally own$ public l&s & natural & cultural res\rces4 ,?is includes fo/]+ s\nd use ( our l& & wat] res\rces2 protect+ our fi%1 wildlife1 & biological div]sity2 pres]v+ ! environm5tal & cultural values ( our national p>ks & hi/orical places2 & provid+ = ! enjoym5t ( life ?r\gh outdoor recreation ,! ,dep>tm5t assesses our en]gy & m9]al res\rces & works to ensure t _! developm5t is 9 ! be/ int]e/s ( all our p by enc\rag+ /ew>d%ip & citiz5 p>ticipation 9 _! c>e4 ,! ,dep>tm5t also has a major responsibility = ,am]ican ,indian res]vation communities & = p :o live 9 isl& t]ritories "u ,u ,s adm9i/ration4 ,transcrib]'s ,notes --,reta9$ publication in=mation f ! pr9t$ edition3 ?is e,book is public-doma9 9 ! c\ntry ( publication4 --,9 ! text v]sions only1 text 9 italics is delimit$ by und]scores4 --,9 ! ,,ascii v]sion only1 subscript$ numb]s are prec$$ by und]score & delimit$ by brackets4