,volcanoes of the ,united ,states by ,steven ,r4 ,brantley ,for sale by the ,,us4 ,government ,printing ,office ,superintendent of ,documents1 ,mail ,stop3 ,,ssop1 ,washington1 ,,dc #bjdjb-icbh ,,isbn #j-af-jdejed-c ,illustration3 ,mount ,shasta1 ,california1 has erupted at least #aj times in the past #c1djj years and at least #c times in the past #gej years4 7,photograph by ,lyn ,topinka47 ,introduction ,few natural forces are as spectacular and threatening1 or have played such a dominant role in shaping the face of the ,earth1 as erupting volcanoes4 ,volcanism has built some of the world's greatest mountain ranges1 covered vast regions with lava 7molten rock at the ,earth's surface71 and triggered explosive eruptions whose size and power are nearly impossible for us to imagine today4 ,fortunately1 such calamitous eruptions occur infrequently4 ,of the #ej or so volcanoes that erupt every year1 however1 a few severely disrupt human activities4 ,between #aihj and #aiij1 volcanic activity killed at least #bf1jjj people and forced nearly #dej1jjj to flee from their homes4 ,though few people in the ,united ,states may actually experience an erupting volcano1 the evidence for earlier volcanism is preserved in many rocks of ,north ,america4 ,features seen in volcanic rocks only hours old are also present in ancient volcanic rocks1 both at the surface and buried beneath younger deposits4 ,a thick ash deposit sandwiched between layers of sandstone in ,nebraska1 the massive granite peaks of the ,sierra ,nevada mountain range1 and a variety of volcanic layers found in eastern ,maine are but a few of the striking clues of past volcanism4 ,with this perspective1 an erupting volcano is not only an exciting and awesome spectacle in its own right but a window into a natural process that has happened over and over again throughout ,earth's history4 ,the ,earth's crust1 on which we live and depend1 is in large part the product of millions of once-active volcanoes and tremendous volumes of magma 7molten rock below ground7 that did not erupt but instead cooled below the surface4 ,such persistent and widespread volcanism has resulted in many valuable natural resources throughout the world4 ,for example1 volcanic ash blown over thousands of square kilometers of land increases soil fertility for forests and agriculture by adding nutrients and acting as a mulch4 ,groundwater heated by large1 still-hot magma bodies can be tapped for geothermal energy4 ,and over many thousands of years1 heated groundwater has concentrated valuable minerals1 including copper1 tin1 gold1 and silver1 into deposits that are mined throughout the world4 ,the ,united ,states ranks third1 behind ,indonesia and ,japan1 in the number of historically active volcanoes 7that is1 those for which we have written accounts of eruptions74 ,in addition1 about #aj percent of the more than #a1ejj volcanoes that have erupted in the past #aj1jjj years are located in the ,united ,states4 ,most of these volcanoes are found in the ,aleutian ,islands1 the ,alaska ,peninsula1 the ,hawaiian ,islands1 and the ,cascade ,range of the ,pacific ,northwest2 the remainder are widely distributed in the western part of the ,nation4 ,a few ,u4,s4 volcanoes have produced some of the largest and most dangerous types of eruptions in this century1 while several others have threatened to erupt4 ,illustration3 ,map of ,united ,states showing areas where active volcanoes are located and shown later in more detail4 ,,alaska ,see page #bd ,,united ,,states ,see page #af ,,hawaiian ,,islands ,see page #aj ,scientists at the ,u4,s4 ,geological ,survey 7,,usgs7 engage in a variety of research activities in order to reduce the loss of life and property that can result from volcanic eruptions and to minimize the social and economic turmoil that can result when volcanoes threaten to erupt4 ,these activities include studies of the physical processes before1 during1 and after a volcanic eruption1 assessments of volcano hazards1 and public outreach to translate scientific information about volcanoes into terms that are meaningful to the public and public officials4 ,monitoring volcanoes for signs of activity1 another vital component1 is carried out by ,,usgs earth scientists at three volcano observatories1 which were established to study active volcanoes in ,hawaii 7#aiab71 the ,cascades 7#aihj71 and ,alaska 7#aihh74 ,these researchers record earthquakes1 survey the surfaces of volcanoes1 map volcanic rock deposits1 and analyze the chemistry of volcanic gas and fresh lava to detect warning signs of impending activity and determine the most likely type of activity that will affect areas around a volcano4 ,during the past #aj years1 several warnings of eruptions were issued by the ,,usgs and monitoring of recently active volcanoes in the ,united ,states was expanded4 ,predicting the time and size of volcanic eruptions1 however1 remains a difficult challenge for scientists4 ,illustration3 ,scientist collects lava sample from lava flow entering the sea on ,kilauea ,volcano4 7,photograph by ,j4,d4 ,griggs47 ,illustration3 ,scientists conducting field studies on active volcanoes in the ,united ,states4 ,illustration3 ,field studies4 ,illustration3 ,field studies4 ,illustration3 ,field studies4 ,volcanoes and the ,theory of ,plate ,tectonics ,illustration3 ,major tectonic plates of the ,earth4 ,only a few of the ,earth's active volcanoes are shown4 7,sketch by ,ellen ,lougae47 ,,plates ,,eurasian ,,north ,,american ,,juan ,,de ,,fuca ,,philippine ,,caribbean ,,pacific ,,cocos ,,nazca ,,australian ,,eurasian ,,arabian ,,indian ,,african ,,south ,,american ,,scotia ,,antarctic ,,explanation ,plate boundary ,active volcanoes ,volcanoes are not randomly distributed over the ,earth's surface4 ,most are concentrated on the edges of continents1 along island chains1 or beneath the sea forming long mountain ranges4 ,more than half of the world's active volcanoes above sea level encircle the ,pacific ,ocean to form the circum-,pacific 8,ring of ,fire40 ,in the past #be years1 scientists have developed a theory--called plate tectonics--that explains the locations of volcanoes and their relationship to other large-scale geologic features4 ,according to this theory1 the ,earth's surface is made up of a patchwork of about a dozen large plates that move relative to one another at speeds from less than one centimeter to about ten centimeters per year 7about the speed at which fingernails grow74 ,these rigid plates1 whose average thickness is about #hj kilometers1 are spreading apart1 sliding past each other1 or colliding with each other in slow motion on top of the ,earth's hot1 pliable interior4 ,volcanoes tend to form where plates collide or spread apart1 but they can also grow in the middle of a plate1 as for example the ,hawaiian volcanoes4 ,illustration3 ,the boundary between the ,pacific and ,juan de ,fuca ,plates is marked by a broad submarine mountain chain about #ejj km long1 known as the ,juan de ,fuca ,ridge4 ,young volcanoes1 lava flows1 and hot springs were discovered in a broad valley less than #h km wide along the crest of the ridge in the #aigj's4 ,the ocean floor is spreading apart and forming new ocean crust along this valley or 8rift0 as hot magma from the ,earth's interior is injected into the ridge and erupted at its top4 ,in the ,pacific ,northwest1 the ,juan de ,fuca ,plate plunges beneath the ,north ,american ,plate4 ,as the denser plate of oceanic crust is forced deep into the ,earth's interior beneath the continental plate1 a process known as subduction1 it encounters high temperatures and pressures that partially melt solid rock4 ,some of this newly formed magma rises toward the ,earth's surface to erupt1 forming a chain of volcanoes above the subduction zone4 ,,pacific ,,plate ,juan de ,fuca ,ridge ,,juan ,,de ,,fuca ,,plate ,,north ,,american ,,plate ,mt4 ,baker ,glacier ,peak ,mt4 ,rainier ,,magma ,magma ,conduit ,illustration3 ,located in the middle of the ,pacific ,plate1 the volcanoes of the ,hawaiian ,island chain are among the largest on ,earth4 ,the volcanoes stretch #b1ejj km across the north ,pacific ,ocean and become progressively older to the northwest4 ,formed initially above a relatively stationary 8hot spot0 in the ,earth's interior1 each volcano was rafted away from the hot spot as the ,pacific ,plate moves northwestward at about #i cm per year4 ,the island of ,hawaii consists of the youngest volcanoes in the chain and is currently located over the hot spot4 ,,hawaii ,,niihau ,,kauai ,,oahu ,,molokai ,,lanai ,,maui ,,kahoolawe ,,pacific ,,plate ,oceanic ,crust ,fixed 8,hot ,spot0 ,zone of magma formation extends to ,kilauea ,mauna ,loa ,direction of place movement ,recent ,eruptions ,from ,u4,s4 ,volcanoes ,hawaiian volcanoes ,few places on ,earth allow closer or more dramatic views of volcanic activity than ,mauna ,loa and ,kilauea volcanoes on the island of ,hawaii4 ,their frequent but usually non-explosive eruptions make them ideal for scientific study4 ,kilauea's eruptions are so intensely monitored that scientists have assembled a detailed picture of the volcano's magma reservoir 8plumbing0 system and how it behaves before and during eruptions4 ,studies of these volcanoes and the surrounding ocean floor continue to improve our understanding of the geologic history of the ,hawaiian ,island chain and the ability of scientists to determine volcanic hazards that threaten island residents4 ,illustration3 ,hawaiian ,volcanoes ,,explanation ,volcano active during past #b1jjj years ,potentially active volcano ,population centers #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 of ,hawaiian volcanoes are typically non-explosive because of the composition of the magma4 ,almost all of the magma erupted from ,hawaii's volcanoes forms dark gray to black volcanic rock 7called basalt71 generally in the form of lava flows and1 less commonly1 as fragmented lava such as volcanic bombs1 cinders1 pumice1 and ash4 ,basalt magma is more fluid than the other types of magma 7andesite1 dacite1 and rhyolite74 ,consequently1 expanding volcanic gases can escape from basalt relatively easily and can propel lava high into the air1 forming brilliant fountains sometimes called 8curtains of fire40 ,lava1 whether erupted in high fountains or quietly pouring out1 collects to form flows that spread across the ground in thin broad sheets or in narrow streams4 ,the fluid nature of basalt magma allows it to travel great distances from the vent 7the place where lava breaks ground7 and tends to build volcanoes in the shape of an inverted warrior shield1 with slopes less than about #aj degrees4 ,volcanoes with this kind of profile are called shield volcanoes4 ,hawaiian volcanoes erupt at their summit calderas and from their flanks along linear rift zones that extend from the calderas4 ,calderas are large steep-walled depressions that form when a volcano's summit region collapses1 usually after a large eruption empties or partly empties a reservoir of magma beneath the volcano4 ,rift zones are areas of weakness within a volcano that extend from the surface to depths of several kilometers4 ,magma that erupts from the flank of a volcano must first flow underground through one of the volcano's rift zones1 sometimes traveling more than #cj kilometers from the summit magma reservoir before breaking the surface4 ,mauna ,loa4 ,rising more than #i1jjj meters from the seafloor1 ,mauna ,loa is one of the world's largest active volcanoes2 from its base below sea level to its summit1 ,mauna ,loa is taller than ,mount ,everest4 ,it has erupted #ae times since #aijj1 with eruptions lasting from less than #a day to as many as #ade days4 ,the most recent eruption began before dawn on ,march #be1 #aihd4 ,brilliant lava fountains lit the night-time sky as fissures opened across the floor of the caldera4 ,within hours1 the summit activity stopped and lava began erupting from a series of vents along the northeast rift zone4 ,when the eruption stopped #c weeks later1 lava flows were only #f4e kilometers from buildings in the city of ,hilo4 ,mauna ,loa erupts less frequently than ,kilauea1 but it produces a much greater volume of lava over a shorter period of time4 ,illustration3 ,lava fountains erupt from along ,mauna ,loa's rift zone4 ,fountains are about #be meters high4 7,photograph by ,j4,d4 ,griggs47 ,kilauea ,volcano4 ,kilauea's longest rift-zone eruption in historical time began on ,january #c1 #aihc4 ,a row of lava fountains broke out from its east rift zone about #ag kilometers from the summit caldera2 within a few months1 the activity settled down to a single vent4 ,powerful fountaining episodes hurled molten rock #dej meters into the air and built a cone of lava fragments that quickly became the tallest landmark on the rift zone4 ,the eruption changed style abruptly in ,july #aihf when lava broke out through a new vent4 ,instead of regular episodes of high lava fountaining1 lava spilled continuously onto ,kilauea's surface4 ,the steady outpouring of lava formed a lake of molten rock that became perched atop a small shield volcano4 ,by ,june #aiia1 the shield was about #fj meters tall and #a1fjj meters in diameter1 and lava from the eruption had covered #ge square kilometers of forest and grassland1 added #abj hectares of new land to the island1 and destroyed #agi homes4 ,illustration3 ,aerial view of ,hawaii's two most active volcanoes1 ,kilauea and ,mauna ,loa4 7,photograph by ,j4,d4 ,griggs47 ,mauna ,loa ,halemaumau ,crater ,kilauea caldera ,although most of ,kilauea's historical rift eruptions were much briefer1 prolonged eruptive activity in the east rift zone from #aifi to #aigd formed a similar shield1 ,mauna ,ulu 7,hawaiian for 8,growing ,mountain071 and an extensive lava field on the volcano's south flank4 ,the geologic record shows that such large-volume eruptions from the rift zones and the summit area1 covering large parts of ,kilauea's surface1 have occurred many times in the recent past4 ,in fact1 about #ij percent of ,kilauea's surface is covered with lava flows that are less than #a1ajj years old4 ,illustration3 ,the volcanic cone of ,pu'u ,o'o1 named after an extinct ,hawaiian bird1 towers above an active lava lake 7background74 7,photograph by ,j4,d4 ,griggs47 ,most eruptions at ,kilauea can be viewed at close range1 but a few historical eruptions were dangerously explosive4 ,fast-moving mixtures of ash and gas1 called pyroclastic surges1 raced across the summit area and into the southwest rift zone during an eruption in #agij4 ,footprints preserved in a layer of ash #cj kilometers southwest of the summit probably include those of a party of ,hawaiian warriors and their families who were crossing the volcano when the eruption struck4 ,an estimated #hj of the #bej people were killed by suffocating clouds associated with the pyroclastic surges4 ,a smaller explosive eruption in #aibd from ,halemaumau ,crater in ,kilauea summit caldera1 which killed a photographer who was too close1 hurled rocks weighing as much as #h tons as far as #a kilometer4 ,illustration3 ,lava fountain erupting from ,pu'u ,o'o cone4 ,forty-four episodes of such fountaining between #aihc and #aihf built the cone #bee meters tall4 7,photograph by ,j4,d4 ,griggs47 ,cascade volcanoes ,volcanoes of the ,cascade ,range erupt far less frequently than ,kilauea and ,mauna ,loa1 but they are more dangerous because of their violently explosive behavior and their proximity to populated and cultivated areas in ,washington1 ,oregon1 and ,california4 ,the #aihj eruption of ,mount ,st4 ,helens in southwest ,washington dramatically illustrated the type of volcanic activity and destruction these volcanoes can produce4 ,scientific studies of the eruption of ,mount ,st4 ,helens and the eruptive histories of other ,cascade volcanoes continue to improve public awareness and understanding of these potentially dangerous peaks4 ,in contrast to ,kilauea1 ,cascade volcanoes erupt a variety of magma types that generate a wide range of eruptive behavior and build steep-sided cones known as composite volcanoes4 ,in addition to basalt1 andesite and dacite magmas are common4 ,illustration3 ,cascade ,volcanoes4 ,,explanation ,volcano active during past #b1jjj years ,potentially active volcano ,area of potential volcanic activity ,population centers #dj1jjj to #ajj1jjj #ajj1jjj to #cej1jjj #cej1jjj to #a1jjj1jjj ,greater than #a1jjj1jjj ,,pacific ,,ocean ,,washington ,mount ,baker ,glacier ,park ,seattle ,spokane ,mount ,rainier ,mount ,st4 ,helens ,mount ,adams ,,montana ,great ,falls ,billings ,,idaho ,boise ,craters of the ,moon ,,oregon ,portland ,mount ,hood ,mount ,jefferson ,three ,sisters ,eugene ,newberry ,crater ,crater ,lake ,,wyoming ,yellowstone ,casper ,cheyenne ,,california ,medicine ,lake ,mount ,shasta ,lassen ,peak ,clear ,lake ,sacramento ,san ,francisco ,long ,valley ,caldera ,coso ,los ,angeles ,san ,diego ,,nevada ,reno ,las ,vegas ,,utah ,salt ,lake ,city ,,colorado ,denver ,,arizona ,san ,francisco ,field ,phoenix ,tucson ,,new ,,mexico ,albuquerque ,bandera ,field ,these magmas are so highly viscous1 or sticky1 that expanding volcanic gases cannot easily escape from them4 ,this causes a tremendous build-up in pressure1 often leading to extremely explosive eruptions4 ,during such eruptions1 magma is shattered into tiny fragments 7chiefly ash and pumice7 and ejected thousands of meters into the atmosphere or even the stratosphere4 ,under the force of gravity1 sometimes these fragments sweep down a volcano's flanks at speeds of more than #ajj kilometers per hour1 mixing with air and volcanic gases to form pyroclastic flows4 ,rock fragments can also mix with water in river valleys to form lahars 7volcanic debris flows and mudflows7 that destroy everything in their paths4 ,andesite and dacite magmas also erupt to form lava flows4 ,because these lavas are more viscous 78stickier07 than basalt1 they tend to form thicker flows that travel shorter distances from the vent2 consequently1 andesite and dacite lavas typically build tall cones with steep slopes of more than #bj degrees4 ,illustration3 ,mt4 ,hood1 ,oregon4 ,eruptions from the volcano about #a1hjj and #bjj years ago from the ,crater ,rock lava dome formed a broad apron of rock debris on the volcano's south side4 7,photograph by ,lyn ,topinka47 ,mount ,baker1 ,washington4 ,eyewitness reports of small ashy plumes and active steam vents on ,mount ,baker dating as far back as the mid-#ahjj's were clear evidence that the ice-covered volcano had one of the most active geothermal systems among ,cascade volcanoes4 ,when new fumaroles and unusually dark vapor plumes appeared abruptly in ,march #aige1 however1 people in the ,northwest became concerned about an impending eruption and possible avalanches and lahars from ,sherman ,crater1 a vent just south of ,mount ,baker's summit4 ,despite a tenfold increase in the release of heat by the volcano during the next #ab months1 which resulted in extensive changes to the ice cover in ,sherman ,crater and produced minor releases of ash1 no eruption occurred4 ,the thermal activity was not accompanied by earthquakes1 which generally precede most eruptions1 and since #aigf1 the volcano has not showed additional signs of activity4 ,illustration3 ,mount ,baker viewed to the west4 ,increased fumarolic activity occurred in ,sherman ,crater 7left of summit7 during the mid-#aigj's4 ,the increased thermal activity between #aige and #aigf prompted public officials and ,puget ,power to temporarily close public access to the popular ,baker ,lake recreation area and to lower the reservoir's water level by #aj meters4 ,significant avalanches of debris from the ,sherman ,crater area could have swept directly into the reservoir1 triggering a disastrous wave that would have caused loss of life and damage to the reservoir4 ,illustration3 ,mount ,rainier towers #c1jjj meters above the surrounding valleys1 all of which have been swept by lahars during the past #aj1jjj years4 ,future eruptions will probably trigger similar lahars4 7,photograph by ,david ,wieprecht47 ,mount ,rainier1 ,washington4 ,mount ,rainier has not produced a significant eruption in the past #ejj years1 but scientists consider it to be one of the most hazardous volcanoes in the ,cascades4 ,mount ,rainier has #bf glaciers containing more than five times as much snow and ice as all the other ,cascade volcanoes combined4 ,if only a small part of this ice were melted by volcanic activity1 it would yield enough water to trigger enormous lahars4 ,mount ,rainier's potential for generating destructive mudflows is enhanced by its great height above surrounding valleys and its 8soft0 interior4 ,the volcano stands about #c1jjj meters above river valleys leading from its base4 ,volcanic heat and ground water have turned some of the volcano's originally hard lava into soft clay minerals1 thereby weakening its internal structure4 ,these conditions make ,mount ,rainier extremely susceptible to large landslides4 ,several have occurred in the past few thousand years1 one as recently as about #fjj years ago4 ,these landslides1 apparently containing great volumes of water1 quickly turned into lahars as they rushed down river valleys4 ,mount ,st4 ,helens1 ,washington4 ,the catastrophic eruption on ,may #ah1 #aihj1 was preceded by #b months of intense activity that included more than #aj1jjj earthquakes1 hundreds of small phreatic 7steam-blast7 explosions1 and the outward growth of the volcano's entire north flank by more than #hj meters4 ,a magnitude #e4a earthquake struck beneath the volcano at #jh3cb on ,may #ah1 setting in motion the devastating eruption4 ,illustration3 ,mount ,st4 ,helens crater and lava dome viewed from the north1 #aiij4 ,inset3 ,close view of lava dome with new lava extrusion on top 7snow-free part7 from the south1 #aihf4 7,photographs by ,lyn ,topinka47 ,within seconds of the earthquake1 the volcano's bulging north flank slid away in the largest landslide in recorded history1 triggering a destructive1 lethal lateral blast of hot gas1 steam1 and rock debris that swept across the landscape as fast as #a1ajj kilometers per hour4 ,temperatures within the blast reached as high as #cjj degrees ,celsius4 ,snow and ice on the volcano melted1 forming torrents of water and rock debris that swept down river valleys leading from the volcano4 ,within minutes1 a massive plume of ash thrust #ai kilometers into the sky1 where the prevailing wind carried about #ebj million tons of ash across #eg1jjj square kilometers of the ,western ,united ,states4 ,illustration3 ,stand of timber in the process of being harvested was instead knocked over by the lateral blast4 ,an estimated #d million board feet of timber was destroyed4 7,photograph by ,h4,h4 ,kieffer47 ,illustration3 ,small eruption of gas and ash from the lava dome caused by violent release of volcanic gas or the geyser-like flashing of superhot ground water to steam4 7,photograph by ,dan ,dzurisin47 ,illustration3 ,mount ,st4 ,helens towers above the chaotic landslide deposit that fills a former valley to a depth of as much as #aie meters4 ,note many small hills atop the landslide1 called 8hummocks0 by geologists4 7,photograph by ,lyn ,topinka47 ,the well-documented landslide at ,mount ,st4 ,helens has helped geologists to recognize more than #bjj similar deposits at other volcanoes in the world1 including several other ,cascade peaks4 ,geologists now realize that large landslides from volcanoes are far more common than previously thought--seventeen such volcanic landslides have occurred worldwide in the past #djj years4 ,consequently1 when scientists evaluate the types of volcanic activity that may endanger people1 giant landslides are now included1 in addition to other types of volcanic activity such as lava flows1 pyroclastic flows1 lahars1 and falling ash4 ,following the #aihj explosive eruption1 more than a dozen extrusions of thick1 pasty lava built a mound-shaped lava dome in the new crater4 ,the dome is about #a1ajj meters in diameter and #bej meters tall4 ,illustration3 ,giant mushroom-shaped ash cloud of ,may #bb1 #aiae1 viewed from #hj kilometers west of ,lassen ,peak4 7,photograph provided by ,national ,park ,service47 ,lassen ,peak1 ,california4 ,long before the recent activity of ,mount ,st4 ,helens1 a series of spectacular eruptions from ,lassen ,peak between #aiad and #aiag demonstrated the explosive potential of ,cascade volcanoes4 ,small phreatic explosions began on ,may #cj1 #aiad1 and were followed during the next #ab months by more than #aej explosions that sent clouds of ash as high as #c kilometers above the peak4 ,the activity changed character in ,may #aiae1 when a lava flow was observed in the summit crater4 ,a deep red glow from the hot lava was visible at night #cd kilometers away4 ,on ,may #ai1 an avalanche of hot rocks from the lava spilled onto snow and triggered a lahar that extended more than #ae kilometers from the volcano4 ,the most destructive explosion occurred on ,may #ba1 when a pyroclastic flow devastated forests as far as #f4e kilometers northeast of the summit and lahars swept down several valleys radiating from the volcano4 ,an enormous ash plume rose more than #i kilometers above the peak1 and the prevailing winds scattered the ash across ,nevada as far as #ejj kilometers to the east4 ,lassen ,peak continued to produce smaller eruptions until about the middle of #aiag4 ,alaskan volcanoes ,the ,alaska ,peninsula and the ,aleutian ,islands have about #hj major volcanic centers that consist of one or more volcanoes4 ,recent violent eruptions have demonstrated that volcanic hazards do exist in some areas of ,alaska1 even though it is sparsely populated4 ,alaskan volcanoes have produced one or two eruptions per year since #aijj4 ,at least #bj catastrophic caldera-forming eruptions have occurred in the past #aj1jjj years2 the awesome eruption of #aiab at ,novarupta in the ,katmai ,national ,monument is the most recent4 ,scientists are particularly concerned about the volcanoes whose eruptions can affect the ,cook ,inlet region1 where #fj percent of ,alaska's population lives4 ,illustration3 ,alaskan volcanoes4 ,,explanation ,volcano active during past #b1jjj years ,population center #ajj1jjj to #cej1jjj ,,alaska ,wrangell ,hayes ,anchorage ,spurr ,redoubt ,iliamna ,akutan ,novarupta ,augustine ,cook ,inlet ,trident ,bogoslof ,ukinrek ,martin ,mageik ,kagamil ,chiginagak ,ugashik-,peulik ,carlisle ,emmons ,lake ,yantami ,kiska ,cerberus ,fisher ,dutton ,aniakchak ,veniaminof ,little ,sitkin ,kasatochi ,amukta ,pyre ,pavlof ,isanotski ,westdahl ,shishaldin ,makushin ,gareloi ,vsevidof ,okmok ,tanaga ,korovin ,cleveland ,kanaga ,great ,sitkin ,yunaska ,illustration3 ,redoubt ,volcano1 ,alaska1 erupting on ,december #af1 #aihi4 7,photograph by ,national ,park ,service47 ,redoubt ,volcano4 ,redoubt ,volcano erupted for the fourth time this century on ,december #ad1 #aihi4 ,following several days of strong explosive activity1 a series of lava domes grew in ,redoubt's summit crater during the next four months4 ,most of the domes were destroyed by explosions or collapsed down the volcano's north flank4 ,some of these events triggered small pyroclastic flows that melted snow and ice on the volcano to form lahars in ,drift ,river ,valley1 which empties into ,cook ,inlet #ce kilometers away4 ,ash produced by the eruptions severely affected air traffic enroute to ,anchorage1 ,alaska's largest city and a major hub of domestic and international commercial air traffic4 ,many domestic carriers suspended service to ,alaska following major explosive events1 and several international carriers temporarily rerouted flights around ,alaska4 ,on ,december #ae1 a jetliner enroute to ,japan encountered an ash cloud while descending into ,anchorage4 ,the plane quickly lost power in all four engines and lost #d1jjj meters in altitude before the pilots were able to restart the engines4 ,the aircraft landed safely in ,anchorage1 but it sustained more than #hj million in damage4 ,illustration3 ,lava dome in the summit crater of ,redoubt ,volcano1 which grew between ,april #ba and ,june #aiij4 7,photograph by ,david ,wieprecht47 ,lahars generated during the eruption threatened an oil-storage facility located on the banks of ,drift ,river4 ,oil is pumped from more than a dozen wells in ,cook ,inlet to the facility and then loaded onto tankers1 which dock just offshore4 ,a lahar on ,january #b flooded part of the facility with nearly a meter of water1 forcing its shutdown until workers could restore power4 ,this and subsequent lahars prompted the ,cook ,inlet ,pipeline ,company to temporarily halt oil production from some oil wells and reduce the amount of oil stored at the facility between tanker loadings4 ,illustration3 ,rock from the lava dome of ,redoubt ,volcano deposited in a river valley by a lahar during an eruption on ,january #h1 #aiij4 ,when found #f days later1 the temperature of the rock was still #ade;,c4 7,photograph by ,c4 ,dan ,miller47 ,illustration3 ,steam plume rises from lava dome atop ,augustine ,volcano on ,april #cj1 #aihf4 7,photograph by ,m4,e4 ,yount47 ,augustine ,volcano4 ,one of the most active volcanoes in ,cook ,inlet is ,augustine1 whose symmetrical cone rises #a1bed meters above the sea4 ,since ,captain ,james ,cook discovered and named it in #aggh1 ,augustine has erupted in #ahab1 #ahhc1 #aice1 #aifc-fd1 #aigf1 and #aihf4 ,curiously1 the quiet intervals between these eruptions apparently have shortened from #gj to #aj years4 ,augustine's #aihf eruption was similar to the pattern of events observed in #aigf4 ,after eight months of earthquake activity beneath the volcano1 a violent explosion began on ,march #bf4 ,billowing ash plumes rose more than #aj kilometers above the vent1 pyroclastic flows sped down the volcano's flanks into the sea1 and ash spread throughout ,cook ,inlet4 ,a second stage began ,april #bc1 when lava began erupting near the volcano's summit and added about #be meters to the top of the existing lava dome4 ,small pyroclastic flows accompanied growth of the dome4 ,scientists were worried that this eruption might trigger a giant landslide from ,augustine's steep upper cone1 which could enter the sea to create a tsunami 7powerful seismic sea wave74 ,at least #ab landslides are known to have occurred at ,augustine4 ,the most recent slide took place at the onset of the #ahhc eruption when a part of the volcano's summit collapsed into the sea4 ,within one hour1 a tsunami as high as #i meters crashed ashore on the coast of the ,kenai ,peninsula #hj kilometers away4 ,no one was killed and property damage was only minor because the tsunami hit at low tide4 ,subsequent eruptions have rebuilt a steep cone of overlapping lava domes similar to the cone that existed just before the #ahhc landslide4 ,illustration3 ,pyroclastic flow descending the upper flanks of ,augustine ,volcano4 7,photograph by ,m4,e4 ,yount47 ,novarupta1 ,katmai ,national ,monument4 ,the largest eruption in the world this century occurred in #aiab at ,novarupta on the ,alaska ,peninsula4 ,an estimated #ae cubic kilometers of magma was explosively erupted during #fj hours beginning on ,june #f--;about #cj times the volume erupted by ,mount ,st4 ,helens in #aihj6 ,the expulsion of such a large volume of magma excavated a funnel-shaped vent #b kilometers wide and triggered the collapse of ,mount ,katmai volcano #aj kilometers away to form a summit caldera #fjj meters deep and about #c kilometers across4 ,extrusion of the lava dome1 called ,novarupta1 near the center of the #aiab vent marked the end of the eruption4 ,little was known about the spectacular effects of this great eruption until #aiaf1 when a scientific expedition sponsored by the ,national ,geographic ,society visited the area4 ,to their amazement1 they found a broad valley northwest of ,novarupta marked by a flat plain of loose1 8sandy0 ash material from which thousands of jets of steam were hissing4 ,the eruption had produced pyroclastic flows that swept about #ba kilometers down the upper ,ukak ,river valley4 ,the thickness of the resulting pumice and ash deposits in the upper valley is not known but may be as great as #bjj meters4 ,in #aiaf1 the deposits were still hot enough to boil water and form countless steaming fumaroles2 hence the expedition named this part of the ,ukak ,river the 8,valley of ,ten ,thousand ,smokes40 ,trident ,volcano4 ,eruptions of andesitic lava flows between #aiec and #aifj built a new cone on ,trident's southwest flank1 adding yet another to the volcano's older complex of three overlapping cones 7hence the name ,trident74 ,a huge cloud of rising ash was seen on ,february #ae1 #aiec1 in the direction of ,katmai ,national ,monument2 #c days later clear weather permitted ,u4,s4 ,navy pilots to spot a blocky lava flow emerging from ,trident's southwest flank4 ,slow extrusion of lava during the next #d months built an irregularly shaped lava dome about #a4e kilometers long and #fjj meters tall4 ,trident continued to erupt intermittently through #aifj1 generating three lava flows as long as #d4e kilometers from the same vent and numerous ash-producing explosive eruptions4 ,illustration3 ,novarupta lava dome1 ,mt4 ,katmai1 and ,trident ,volcano1 ,alaska4 ,the dome is #chj meters in diameter and occupies a small part of the vent from which about #ae cubic kilometers of magma was erupted in #aiab 7dashed line marks approximate outline of vent74 7,copyrighted photograph reprinted with permission1 ,aero ,map ,,us ,inc41 ,august #ba1 #aihg47 ,illustration3 ,small steam plume rises from a cinder cone within the summit caldera of ,mount ,veniaminof1 ,alaska4 ,the large pit in the ice formed when lava 7dark area7 flowed beneath the ice and melted it4 7,photograph by ,m4,e4 ,yount47 ,mount ,veniaminof4 ,mount ,veniaminof is a massive composite volcano with a summit caldera about #h kilometers in diameter4 ,since its formation about #c1gjj years ago1 the caldera has filled with ice to a depth of at least #fj meters4 ,between ,june #aihc and ,january #aihd1 a series of small explosions1 lava fountains1 and lava flows erupted from a small cinder cone within the caldera4 ,the explosions hurled molten lava from the cinder cone1 and lava flows melted a pit about #a4e kilometers in diameter in the ice near the base of the volcano4 ,water from the melting ice formed a temporary lake4 ,mount ,spurr4 ,the summit cone of ,mount ,spurr consists of a large lava dome built in the center of a horseshoe-shaped crater formed earlier by a large landslide4 ,at the southern edge of this ancient crater is a younger1 more active cone known as ,crater ,peak4 ,scientists have determined that ,crater ,peak is the source for at least #ce ash layers found in the ,cook ,inlet area1 all of which were erupted in the past #f1jjj years4 ,until recently1 a warm turquoise-colored lake partially filled its crater4 ,a series of explosive eruptions from ,crater ,peak on ,june #bg1 #aiib1 generated ash plumes as high as about #ad kilometers1 small pyroclastic flows that swept down the south and east sides of the cone1 and small lahars4 ,the reawakening of ,crater ,peak followed nearly a year of increased earthquake activity1 which escalated further on ,june #bf1 less than #a day before its first eruption4 ,not all of the explosive episodes were preceded by a change in seismicity beneath the volcano1 a condition that required scientists to maintain a #bd-;hour watch for extended periods of time in order to issue sudden reports and warnings of eruptive activity4 ,the west side of ,cook ,inlet received a light to moderate ashfall during the largest explosive episode on ,august #ah2 ,anchorage was blanketed with about #c millimeters of ash1 causing the ,anchorage ,international ,airport to close for a few hours4 ,during an eruption at night on ,september #ag1 a spectacular display of lightning and incandescent ballistics and pyroclastic flows were witnessed by hunters who camped about #ah kilometers to the southeast2 a faint glow above ,crater ,peak was also visible from as far away as ,anchorage4 ,illustration3 ,steaming ,crater ,peak1 a satellite vent on the south side of ,mount ,spurr volcano1 produced three explosive eruptions in #aiib4 7,photograph by ,cynthia ,gardner47 ,illustration3 ,aerial view of the ,mono-,inyo ,craters ,volcanic ,chain1 ,california4 ,several eruptions occurred along both chains as recently as about #eej to #fjj years ago4 7,photograph by ,c4 ,dan ,miller47 ,mono ,craters ,wilson ,butte ,northern part of ,inyo ,volcanic ,chain ,obsidian ,dome ,glass ,creek ,dome ,restless calderas ,the largest and most explosive volcanic eruptions eject tens to hundreds of cubic kilometers of magma onto the ,earth's surface4 ,when such a large volume of magma is removed from beneath a volcano1 the ground subsides or collapses into the emptied space1 to form a huge depression called a caldera4 ,some calderas are more than #be kilometers in diameter and several kilometers deep4 ,calderas are among the most spectacular and active volcanic features on ,earth4 ,earthquakes1 ground cracks1 uplift or subsidence of the ground1 and thermal activity such as hot springs1 geysers1 and boiling mud pots are common at many calderas4 ,such activity is caused by complex interactions among magma stored beneath a caldera1 ground water1 and the regional build-up of stress in the large plates of the ,earth's crust4 ,significant changes in the level of activity at some calderas are common2 these new activity levels can be intermittent1 lasting for months to years1 or persistent over decades to centuries4 ,although most caldera unrest does not lead to an eruption1 the possibility of violent explosive eruptions warrants detailed scientific study and monitoring of some active calderas4 ,recently1 scientists have recognized volcanic unrest at two calderas in the ,united ,states1 ,long ,valley ,caldera in eastern ,california and ,yellowstone ,caldera in ,yellowstone ,national ,park1 ,wyoming4 ,whether unrest at these calderas simply punctuates long periods of quiet or is the early warning sign of future eruptions is an important but still unanswered question4 ,illustration3 ,yellowstone ,river plummets through the famous ,grand ,canyon of ,yellowstone4 ,carved by the river1 the 8yellow0 rocks of the canyon are rhyolite lava flows that have been altered by hot water4 ,the lava flows were erupted after the most recent caldera-forming eruption about #fjj1jjj years ago4 ,long ,valley ,caldera1 ,california4 ,long ,valley ,caldera lies on the eastern front of the ,sierra ,nevada1 about #cjj kilometers east of ,san ,francisco4 ,a huge explosive eruption about #gjj1jjj years ago formed the caldera and produced pyroclastic flows that traveled #fe kilometers from the vent and covered an area of about #a1ejj square kilometers4 ,ash from the caldera-forming eruption fell as far east as ,nebraska4 ,within the past #dj1jjj years1 eruptions have been restricted to a linear zone of vents1 including the ,mono-,inyo ,craters ,volcanic ,chain1 that extends about #ej kilometers north from the northwest part of the caldera4 ,this volcanic chain consists of many vents that have erupted in the past several thousand years4 ,eruptions from vents as recently as #eej years ago produced lava flows1 pyroclastic flows1 and ash1 all of rhyolitic composition4 ,geologic mapping shows that some eruptions were preceded by ground cracking1 suggesting that the ground was pulled apart or stretched as magma neared the surface4 ,illustration3 ,sketch of ,long ,valley ,caldera and the ,mono-,inyo ,craters ,volcanic ,chain in central ,california1 viewed from the southeast4 7,sketch by ,tau ,rho ,alpha47 ,sierra ,nevada ,mono craters ,inyo craters ,mammoth ,lakes ,resurgent dome ,long ,valley ,caldera ,three moderate earthquakes south of the caldera and one beneath the caldera on ,may #be-bf1 #aihj1 marked the beginning of unrest that continues into the #aiij's4 ,swarms of earthquakes beneath the caldera1 changes in several hot springs1 and the formation of new springs have occurred since #aihj4 ,precise surveys have also shown that the central part of the caldera has risen by more than #ej centimeters since #aige4 ,this unrest is probably related to the stretching 7east-west extension7 of the ,earth's crust that is known to be occurring in the region around the caldera1 and it probably also involves the rise of magma beneath the caldera4 ,scientists do not know if this unrest will lead to volcanic activity1 but the geologically recent eruptions along the ,mono-,inyo ,craters ,volcanic ,chain suggest that future eruptions are possible4 ,illustration3 ,south ,inyo ,crater1 ,long ,valley ,caldera1 ,california4 ,explosive eruptions formed the crater about #ejj years ago4 7,photograph by ,steven ,r4 ,brantley47 ,yellowstone ,caldera1 ,yellowstone ,national ,park1 ,wyoming4 ,yellowstone ,caldera is one of the largest and most active calderas in the world4 ,the spectacular geysers1 boiling hot springs1 and mud pots that have made ,yellowstone famous--and even the strikingly beautiful ,grand ,canyon of ,yellowstone through which the ,yellowstone ,river plunges--owe their existence to the tremendous volcanic forces that have affected the region during the past #b million years4 ,cataclysmic eruptions #b4j1 #a4c1 and #j4f million years ago ejected huge volumes of rhyolite magma2 each eruption formed a caldera and extensive layers of thick pyroclastic-flow deposits4 ,the youngest caldera is an elliptical depression1 nearly #hj kilometers long and #ej kilometers wide1 that occupies much of ,yellowstone ,national ,park4 ,the caldera is buried by several extensive rhyolite lava flows erupted between #ge1jjj and #aej1jjj years ago4 ,illustration3 ,map of most recent ,yellowstone ,caldera and its main thermal features4 ,after the caldera formed1 many vents erupted thick rhyolite lava flows1 and the central part of the caldera was pushed upward to form resurgent domes4 ,the star marks the magnitude #g4e ,hebger ,lake earthquake4 ,,idaho ,hebgen ,lake ,west ,yellowstone ,,montana ,silver ,gate ,gardiner ,,wyoming ,yellowstone ,national ,park ,mammoth ,m #g4e ,aug4 #ah #aiei ,norris ,geyser ,basin ,mud ,pots ,old ,faithful ,west ,thumb ,geyser ,basin ,yellowstone ,lake ,,caldera ,,rim ,,colorado ,resurgent dome ,the ,earth's crust beneath ,yellowstone ,national ,park is still restless4 ,precise surveys have detected an area in the center of the caldera that rose by as much as #hf centimeters between #aibc and #aihd and then subsided slightly between #aihe and #aihi4 ,scientists do not know the cause of these ups and downs but hypothesize that they are related to the addition or withdrawal of magma beneath the caldera1 or to the changing pressure of the hot ground water system above ,yellowstone's large magma reservoir4 ,also1 ,yellowstone ,national ,park and the area immediately west of the ,park are historically among the most seismically active areas in the ,rocky ,mountains4 ,small-magnitude earthquakes are common beneath the entire caldera1 but most are located along the ,hebgen ,lake fault zone that extends into the northwest part of the caldera4 ,a magnitude #g4e earthquake occurred along this zone in #aiei4 ,illustration3 ,castle ,geyser erupting a column of hot water1 ,yellowstone ,national ,park4 7,photograph by ,steven ,r4 ,brantley47 ,active ,volcanoes3 ,windows ,into the ,past ,molten rock has erupted onto the surface of the ,earth throughout its #d4e-;billion-year history4 ,although many of these ancient rocks were removed by erosion1 volcanic deposits can be found beneath younger rocks in many parts of the ,united ,states4 ,to a geologist1 such long-lasting volcanic rocks look like those formed by today's active volcanoes4 ,many ancient volcanic rocks1 however1 change somewhat with time1 as they become firmly consolidated1 buried by younger deposits1 and sometimes folded and faulted by the continuous shifting of the ,earth's crust4 ,even minerals of volcanic rocks may change1 if after burial they encounter high pressures and temperatures4 ,illustration3 ,columnar jointing in an ancient lava flow in the ,blue ,ridge ,mountains1 ,shenandoah ,national ,park1 ,virginia4 ,the flow that contains the columns is one of an extensive series of lava flows1 each averaging about #bjj feet thick1 that poured over the land more than #egj million years ago4 ,columns form as cooling or shrinkage joints when a hot lava flow cools quickly2 the columns form perpendicular to the cooling surface4 ,these columns are about 4#e meter in diameter4 7,photograph by ,j4,c4 ,reed1 ,jr47 ,most active volcanoes are built on older volcanic deposits erupted from ancient volcanoes1 and visitors to the present-day volcanoes walk or drive across these products of past volcanism4 ,for example1 anyone driving across the ,cascade ,range1 sunbathing at ,waikiki1 or fishing on the ,alaska ,peninsula is there because old volcanic rocks form the landscape4 ,one step further back in time from today's active volcanoes are people who picnic in the ,white ,mountains of ,new ,hampshire1 enjoy the autumn colors in the ,blue ,ridge of ,shenandoah ,national ,park1 and hike in the rugged ,big ,bend ,national ,park of ,texas4 ,many of the rocks in these areas were formed by eruptions or by intrusion of magma into the ,earth's crust many millions of years ago4 ,because volcanic activity has been so important in shaping the ,earth1 watching active volcanoes today provides a window through which we can glimpse and reconstruct the early volcanic history of our planet4 ,as we increase our knowledge about volcanic processes1 by studying volcanoes erupting today as well as those that have lain dormant for hundreds to thousands of years1 we increase our ability to predict when and how volcanoes will erupt4 ,accurate predictions1 presented in terms that are meaningful to public officials1 will minimize the number of lives lost and the social and economic upheaval that an eruption can cause4 ,illustration3 ,thick layers of volcanic rocks form the ,superstition ,mountains1 located about #fj kilometers east of ,phoenix1 ,arizona4 ,the consolidated deposits of pyroclastic flows1 lava flows and domes1 and lahars in the ,superstition ,mountains and adjacent areas testify to a period of intense volcanism about #ag to #be million years ago in central ,arizona4 7,photograph by ,d4,w4 ,peterson47 ,glossary ,andesite ,a volcanic rock containing #ec-fc silica with a moderate viscosity when in a molten state4 ,ash ,fragments less than #b millimeters in diameter of lava or rock blasted into the air by volcanic explosions4 ,basalt ,a volcanic rock consisting of less than #ec silica with a low viscosity when in a molten state4 ,caldera ,a large volcanic depression1 commonly circular or elliptical when seen from above4 ,composite ,a steep-sided volcano composed of many layers of volcano volcanic rocks1 usually of high-viscosity lava and fragmented debris such as lahar and pyroclastic deposits4 ,dacite ,a volcanic rock containing #fc-fh silica with a high viscosity when in a molten state4 ,dome ,a steep-sided mound that forms when viscous lava piles up near a volcanic vent4 ,domes are formed by andesite1 dacite1 and rhyolite lavas4 ,fumarole ,a vent that releases volcanic gases1 including water vapor 7steam74 ,lahar ,a flowing mixture of water and rock debris that forms on the slopes of a volcano1 sometimes referred to as debris flow or mudflow4 ,the term comes from ,indonesia4 ,lava ,molten rock that erupts from a vent or fissure2 see magma4 ,magma ,molten rock that contains dissolved gas and crystals1 formed deep within the ,earth4 ,when magma reaches the surface1 it is called lava4 ,phreatic ,a type of volcanic explosion that occurs when eruption water comes in contact with hot rocks or ash near a volcanic vent1 causing steam explosions4 ,pumice ,a light-colored volcanic rock containing abundant trapped gas bubbles formed by the explosive eruption of magma4 ,because of its numerous gas bubbles1 pumice commonly floats on water4 ,pyroclastic flow ,a hot1 fast-moving and high-density mixture of ash1 pumice1 rock fragments1 and gas formed during explosive eruptions4 ,pyroclastic ,same process as pyroclastic flow but of much surge lower density4 ,rhyolite ,a volcanic rock containing more than #fh silica with a very high viscosity when in a molten state4 ,shield volcano ,a volcano shaped like an inverted warrior's shield with long gentle slopes produced by eruptions of low-viscosity basaltic lava4 ,silica ,the molecule formed of silicon and oxygen 7,si,o7 that is the basic building block of volcanic rocks and the most important factor controlling the fluidity of magma4 ,the higher a magma's silica content1 the greater its viscosity or 8stickiness40 ,vent ,the opening at the ,earth's surface through which volcanic materials 7magma and gas7 escape4 ,volcano ,a vent in the surface of the ,earth through which magma erupts and also the landform that is constructed by the erupted material4 ,volcanic ,the downslope movement of soil1 rock debris1 and landslide sometimes glacial ice1 with or without water1 from the flank of a volcano4 ,illustration3 ,scientist surveying lava dome at ,redoubt ,volcano4 7,photograph by ,g4 ,mc,gimsey47 ,the metric units used in this publication can be converted to ,english units by using the approximate conversions given below3 ,length #a kilometer #j4f of a mile #a meter #ci4cg inches #a centimeter #j4d inch #a millimeter #j4jd inch ,area #a sq4 kilometer #j4d sq4 mile #a sq4 meter #a4b sq4 yards #a sq4 centimeter #j4aee sq4 inch ,temperature ,to convert ,celsius to ,fahrenheit1 multiply ,c by #a4h and add #cb4 ,to convert ,fahrenheit to ,celsius1 subtract #cb from ,f and divide the result by #a4h4 ,further ,reading ,decker1 ,robert1 and ,decker1 ,barbara1 #aihi1 ,volcanoes3 ,san ,francisco1 ,freeman1 #bhe p4 7,an information-packed introduction to the study of volcanoes written in an easy-to-read style47 ,editors1 #aihb1 ,volcano3 in the series ,planet ,earth1 ,alexandria1 ,virginia1 ,time-,life ,books1 #agf p4 7,a well illustrated and readable general survey of volcanoes and their activity47 ,mc,clelland1 ,lindsay1 ,simkin1 ,tom1 ,summers1 ,marjorie1 ,nielsen1 ,elizabeth1 and ,stein1 ,t4,c41 editors1 #aihi1 ,global ,volcanism #aige-aihe3 ,englewood ,cliffs1 ,new ,jersey1 ,prentice-,hall1 #fef p4 7,a full account of volcanism on ,earth based on eyewitness accounts from geologists and other scientists1 reporters1 travelers1 and other keen observers47 ,simkin1 ,tom1 and ,seibert1 ,lee1 #aiid1 ,volcanoes of the ,world 7,second edition73 ,stroudsburg1 ,pa41 ,hutchinson ,ross1 #bcc p4 7,a comprehensive regional directory of worldwide volcanic activity during the past #aj1jjj years2 activity presented in table format47 ,tilling1 ,r4 ,i41 #aihb1 ,volcanoes3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey general-interest publication1 #df p4 7,a general introduction for the nonspecialist to the study of volcanoes1 with focus on the nature1 types1 workings1 products1 and hazards of volcanoes47 ,tilling1 ,r4 ,i41 #aihd1 ,eruptions of ,mount ,st4 ,helens3 ,past1 present1 and future3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey general-interest publication1 #df p4 7,a nontechnical summary1 illustrated by many color photographs and diagrams1 of the abundant scientific data available for the volcano1 with emphasis on the catastrophic eruption on ,may #ah1 #aihj1 which caused the worst volcanic disaster in ,u4,s4 history47 ,tilling1 ,r4 ,i41 #aihg1 ,eruptions of ,hawaiian volcanoes3 ,past1 present1 and future3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey general-interest publication1 #ed p4 7,a nontechnical summary1 illustrated by color photographs and drawings1 of the eruption history1 style1 and products of two of ,hawaii's active volcanoes1 ,kilauea and ,mauna ,loa47 ,wood1 ,c4 ,a41 and ,kienle1 ,jurgen1 editors1 #aiij1 ,volcanoes of ,north ,america--,united ,states and ,canada3 ,cambridge ,university ,press1 #ced p4 7,a rich compilation of volcanoes and volcanic fields in ,north ,america that were formed in the past #e million years2 includes more than #bej entries prepared by leading experts in volcanology47 ,u4,s4 ,geological ,survey ,information ,services ,p4,o4 ,box #bebhf ,denver1 ,,co #hjbbe ,u4,s4 ,,government ,,printing ,,office3 #aiif #dba-eee ,illustration3 ,front and back cover 7clockwise from top photograph on front7 ,augustine ,volcano1 ,alaska1 #aihf4 ,illustration3 ,mount ,st4 ,helens1 ,washington1 #aihj4 ,illustration3 ,kilauea ,volcano1 ,hawaii1 #aihc4 ,illustration3 ,mount ,spurr1 ,alaska1 #aiib4 ,illustration3 ,mono-,inyo ,craters ,volcanic ,chain inside ,long ,valley ,caldera1 ,california4 ,illustration3 ,u4 ,s4 ,,department ,,of ,,the ,,interior ,,march #c1 #ahdi ,as the ,nation's principal conservation agency1 the ,department of the ,interior has responsibility for most of our nationally owned public lands and natural and cultural resources4 ,this includes fostering sound use of our land and water resources2 protecting our fish1 wildlife1 and biological diversity2 preserving the environmental and cultural values of our national parks and historical places2 and providing for the enjoyment of life through outdoor recreation ,the ,department assesses our energy and mineral resources and works to ensure that their development is in the best interests of all our people by encouraging stewardship and citizen participation in their care4 ,the ,department also has a major responsibility for ,american ,indian reservation communities and for people who live in island territories under ,u ,s administration4 ,transcriber's ,notes --,retained publication information from the printed edition3 this e,book is public-domain in the country of publication4 --,in the text versions only1 text in italics is delimited by underscores4 --,in the ,,ascii version only1 subscripted numbers are preceded by underscore and delimited by brackets4