,illustration3 ,the eruption of ,cerro ,negro ,volcano1 near ,leon1 ,nicaragua1 during ,november #aifh4 ,u4 ,s4 ,department of the ,interior _/ ,u4 ,s4 ,geological ,survey ,volcanoes by ,robert ,i4 ,tilling ,illustration3 ,cover and ,title ,page3 ,lava fountains and flows1 ,mauna ,loa1 ,hawaii1 ,july #f1 #aige4 ,volcanoes destroy and volcanoes create4 ,the catastrophic eruption of ,mount ,st4 ,helens on ,may #ah1 #aihj1 made clear the awesome destructive power of a volcano4 ,yet1 over a time span longer than human memory and record1 volcanoes have played a key role in forming and modifying the planet upon which we live4 ,more than #hj percent of the ,earth's surface--above and below sea level--is of volcanic origin4 ,gaseous emissions from volcanic vents over hundreds of millions of years formed the ,earth's earliest oceans and atmosphere1 which supplied the ingredients vital to evolve and sustain life4 ,over geologic eons1 countless volcanic eruptions have produced mountains1 plateaus1 and plains1 which subsequent erosion and weathering have sculpted into majestic landscapes and formed fertile soils4 ,ironically1 these volcanic soils and inviting terranes have attracted1 and continue to attract1 people to live on the flanks of volcanoes4 ,thus1 as population density increases in regions of active or potentially active volcanoes1 mankind must become increasingly aware of the hazards and learn not to 8crowd0 the volcanoes4 ,people living in the shadow of volcanoes must live in harmony with them and expect1 and should plan for1 periodic violent unleashings of their pent-up energy4 ,this booklet presents a generalized summary of the nature1 workings1 products1 and hazards of the common types of volcanoes around the world1 along with a brief introduction to the techniques of volcano monitoring and research4 ,illustration3 ,on ,august #bd1 ,a4,d4 #gi1 ,vesuvius ,volcano suddenly exploded and destroyed the ,roman cities of ,pompeii and ,herculaneum4 ,although ,vesuvius had shown stirrings of life when a succession of earthquakes in ,a4,d4 #fc caused some damage1 it had been literally quiet for hundreds of years and was considered 8extinct40 ,its surface and crater were green and covered with vegetation1 so the eruption was totally unexpected4 ,yet in a few hours1 hot volcanic ash and dust buried the two cities so thoroughly that their ruins were not uncovered for nearly #a1gjj years1 when the discovery of an outer wall in #agdh started a period of modern archeology4 ,vesuvius has continued its activity intermittently ever since ,a4,d4 #gi with numerous minor eruptions and several major eruptions occurring in #afca1 #agid1 #ahgb1 #aijf and in #aidd in the midst of the ,italian campaign of ,world ,war ,,ii4 ,illustration3 ,in the ,united ,states on ,march #bg1 #aihj1 ,mount ,st4 ,helens ,volcano in the ,cascade ,range1 southwestern ,washington1 reawakened after more than a century of dormancy and provided a dramatic and tragic reminder that there are active volcanoes in the 8lower #dh0 ,states as well as in ,hawaii and ,alaska4 ,the catastrophic eruption of ,mount ,st4 ,helens on ,may #ah1 #aihj1 and related mudflows and flooding caused significant loss of life 7#eg dead or missing7 and property damage 7over #a4b billion74 ,mount ,st4 ,helens is expected to remain intermittently active for months or years1 possibly even decades4 ,the word 8volcano0 comes from the little island of ,vulcano in the ,mediterranean ,sea off ,sicily4 ,centuries ago1 the people living in this area believed that ,vulcano was the chimney of the forge of ,vulcan--the blacksmith of the ,roman gods4 ,they thought that the hot lava fragments and clouds of dust erupting from ,vulcano came from ,vulcan's forge as he beat out thunderbolts for ,jupiter1 king of the gods1 and weapons for ,mars1 the god of war4 ,in ,polynesia the people attributed eruptive activity to the beautiful but wrathful ,pele1 ,goddess of ,volcanoes1 whenever she was angry or spiteful4 ,today we know that volcanic eruptions are not supernatural but can be studied and interpreted by scientists4 ,the ,nature of ,volcanoes ,volcanoes are mountains1 but they are very different from other mountains2 they are not formed by folding and crumpling or by uplift and erosion4 ,instead1 volcanoes are built by the accumulation of their own eruptive products--lava1 bombs 7crusted over lava blobs71 ashflows1 and tephra 7airborne ash and dust74 ,a volcano is most commonly a conical hill or mountain built around a vent that connects with reservoirs of molten rock below the surface of the ,earth4 ,the term volcano also refers to the opening or vent through which the molten rock and associated gases are expelled4 ,illustration3 ,fountaining lava and volcanic debris during the #aiei ,kilauea ,iki eruption of ,kilauea ,volcano1 ,hawaii4 ,driven by buoyancy and gas pressure the molten rock1 which is lighter than the surrounding solid rock1 forces its way upward and may ultimately break through zones of weaknesses in the ,earth's crust4 ,if so1 an eruption begins1 and the molten rock may pour from the vent as non-explosive lava flows1 or it may shoot violently into the air as dense clouds of lava fragments4 ,larger fragments fall back around the vent1 and accumulations of fall-back fragments may move downslope as ash flows under the force of gravity4 ,some of the finer ejected materials may be carried by the wind only to fall to the ground many miles away4 ,the finest ash particles may be injected miles into the atmosphere and carried many times around the world by stratospheric winds before settling out4 ,molten rock below the surface of the ,earth that rises in volcanic vents is known as magma1 but after it erupts from a volcano it is called lava4 ,originating many tens of miles beneath the ground1 the ascending magma commonly contains some crystals1 fragments of surrounding 7unmelted7 rocks1 and dissolved gases1 but it is primarily a liquid composed principally of oxygen1 silicon1 aluminum1 iron1 magnesium1 calcium1 sodium1 potassium1 titanium1 and manganese4 ,magmas also contain many other chemical elements in trace quantities4 ,upon cooling1 the liquid magma may precipitate crystals of various minerals until solidification is complete to form an igneous or magmatic rock4 ,illustration3 ,an idealized diagram of a volcano in an oceanic environment 7left7 and in a continental environment 7right74 ,the diagram below shows that heat concentrated in the ,earth's upper mantle raises temperatures sufficiently to melt the rock locally by fusing the materials with the lowest melting temperatures1 resulting in small1 isolated blobs of magma4 ,these blobs then collect1 rise through conduits and fractures1 and some ultimately may re-collect in larger pockets or reservoirs 78holding tanks07 a few miles beneath the ,earth's surface4 ,mounting pressure within the reservoir may drive the magma further upward through structurally weak zones to erupt as lava at the surface4 ,in a continental environment1 magmas are generated in the ,earth's crust as well as at varying depths in the upper mantle4 ,the variety of molten rocks in the crust1 plus the possibility of mixing with molten materials from the underlying mantle1 leads to the production of magmas with widely different chemical compositions4 ,if magmas cool rapidly1 as might be expected near or on the ,earth's surface1 they solidify to form igneous rocks that are finely crystalline or glassy with few crystals4 ,accordingly1 lavas1 which of course are very rapidly cooled1 form volcanic rocks typically characterized by a small percentage of crystals or fragments set in a matrix of glass 7quenched or super-cooled magma7 or finer grained crystalline materials4 ,if magmas never breach the surface to erupt and remain deep underground1 they cool much more slowly and thus allow ample time to sustain crystal precipitation and growth1 resulting in the formation of coarser grained1 nearly completely crystalline1 igneous rocks4 ,subsequent to final crystallization and solidification1 such rocks can be exhumed by erosion many thousands or millions of years later and be exposed as large bodies of so-called granitic rocks1 as1 for example1 those spectacularly displayed in ,yosemite ,national ,park and other parts of the majestic ,sierra ,nevada mountains of ,california4 ,lava is red hot when it pours or blasts out of a vent but soon changes to dark red1 gray1 black1 or some other color as it cools and solidifies4 ,very hot1 gas-rich lava containing abundant iron and magnesium is fluid and flows like hot tar1 whereas cooler1 gas-poor lava high in silicon1 sodium1 and potassium flows sluggishly1 like thick honey in some cases or in others like pasty1 blocky masses4 ,illustration3 ,two ,polynesian terms are used to identify the surface character of ,hawaiian lava flows4 ,aa1 a basalt with a rough1 blocky appearance1 much like furnace slag1 is shown at the top4 ,pahoehoe1 a more fluid variety with a smooth1 satiny and sometimes glassy appearance1 is shown at the bottom4 ,all magmas contain dissolved gases1 and as they rise to the surface to erupt1 the confining pressures are reduced and the dissolved gases are liberated either quietly or explosively4 ,if the lava is a thin fluid 7not viscous71 the gases may escape easily4 ,but if the lava is thick and pasty 7highly viscous71 the gases will not move freely but will build up tremendous pressure1 and ultimately escape with explosive violence4 ,gases in lava may be compared with the gas in a bottle of a carbonated soft drink4 ,if you put your thumb over the top of the bottle and shake it vigorously1 the gas separates from the drink and forms bubbles4 ,when you remove your thumb abruptly1 there is a miniature explosion of gas and liquid4 ,the gases in lava behave in somewhat the same way4 ,their sudden expansion causes the terrible explosions that throw out great masses of solid rock as well as lava1 dust1 and ashes4 ,the violent separation of gas from lava may produce rock froth called pumice4 ,some of this froth is so light--because of the many gas bubbles--that it floats on water4 ,in many eruptions1 the froth is shattered explosively into small fragments that are hurled high into the air in the form of volcanic cinders 7red or black71 volcanic ash 7commonly tan or gray71 and volcanic dust4 ,illustration3 ,during the #aiei eruption of ,kilauea ,iki1 fountaining lava and volcanic debris completely blocked several of the roads in the ,hawaii ,volcanoes ,national ,park4 ,principal ,types of ,volcanoes ,geologists generally group volcanoes into four main kinds--cinder cones1 composite volcanoes1 shield volcanoes1 and lava domes4 ,cinder cones ,cinder cones are the simplest type of volcano4 ,they are built from particles and blobs of congealed lava ejected from a single vent4 ,as the gas-charged lava is blown violently into the air1 it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone4 ,most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings4 ,cinder cones are numerous in western ,north ,america as well as throughout other volcanic terrains of the world4 ,illustration3 ,schematic representation of the internal structure of a typical cinder cone4 ,in #aidc a cinder cone started growing on a farm near the village of ,parcutin in ,mexico4 ,explosive eruptions caused by gas rapidly expanding and escaping from molten lava formed cinders that fell back around the vent1 building up the cone to a height of #a1bjj feet4 ,the last explosive eruption left a funnel-shaped crater at the top of the cone4 ,after the excess gases had largely dissipated1 the molten rock quietly poured out on the surrounding surface of the cone and moved downslope as lava flows4 ,this order of events--eruption1 formation of cone and crater1 lava flow--is a common sequence in the formation of cinder cones4 ,illustration3 ,parcutin ,volcano1 ,mexico1 is a cinder cone rising approximately #a1bjj feet above the surrounding plain4 ,during #i years of activity1 ,parcutin built a prominent cone1 covered about #ajj square miles with ashes1 and destroyed the town of ,san ,juan4 ,geologists from many parts of the world studied ,parcutin during its lifetime and learned a great deal about volcanism1 its products1 and the modification of a volcanic landform by erosion4 ,composite volcanoes ,some of the ,earth's grandest mountains are composite volcanoes--sometimes called stratovolcanoes4 ,they are typically steep-sided1 symmetrical cones of large dimension built of alternating layers of lava flows1 volcanic ash1 cinders1 blocks1 and bombs and may rise as much as #h1jjj feet above their bases4 ,some of the most conspicuous and beautiful mountains in the world are composite volcanoes1 including ,mount ,fuji in ,japan1 ,mount ,cotopaxi in ,ecuador1 ,mount ,shasta in ,california1 ,mount ,hood in ,oregon1 and ,mount ,st4 ,helens and ,mount ,rainier in ,washington4 ,most composite volcanoes have a crater at the summit which contains a central vent or a clustered group of vents4 ,lavas either flow through breaks in the crater wall or issue from fissures on the flanks of the cone4 ,lava1 solidified within the fissures1 forms dikes that act as ribs which greatly strengthen the cone4 ,illustration3 ,schematic representation of the internal structure of a typical composite volcano4 ,the essential feature of a composite volcano is a conduit system through which magma from a reservoir deep in the ,earth's crust rises to the surface4 ,the volcano is built up by the accumulation of material erupted through the conduit and increases in size as lava1 cinders1 ash1 etc41 are added to its slopes4 ,when a composite volcano becomes dormant1 erosion begins to destroy the cone4 ,as the cone is stripped away1 the hardened magma filling the conduit 7the volcanic plug7 and fissures 7the dikes7 becomes exposed1 and it too is slowly reduced by erosion4 ,finally1 all that remains is the plug and dike complex projecting above the land surface--a telltale remnant of the vanished volcano4 ,illustration3 ,shishaldin ,volcano1 an imposing composite cone1 towers #i1cgb feet above sea level in the ,aleutian ,islands1 ,alaska4 ,an interesting variation of a composite volcano can be seen at ,crater ,lake in ,oregon4 ,from what geologists can interpret of its past1 a high volcano--called ,mount ,mazama--probably similar in appearance to present-day ,mount ,rainier was once located at this spot4 ,following a series of tremendous explosions about #f1hjj years ago1 the volcano lost its top4 ,enormous volumes of volcanic ash and dust were expelled and swept down the slopes as ash flows and avalanches4 ,these large-volume explosions rapidly drained the lava beneath the mountain and weakened the upper part4 ,the top then collapsed to form a large depression1 which later filled with water and is now completely occupied by beautiful ,crater ,lake4 ,a last gasp of eruptions produced a small cinder cone1 which rises above the water surface as ,wizard ,island near the rim of the lake4 ,depressions such as ,crater ,lake1 formed by collapse of volcanoes1 are known as calderas4 ,they are usually large1 steep-walled1 basin-shaped depressions formed by the collapse of a large area over1 and around1 a volcanic vent or vents4 ,calderas range in form and size from roughly circular depressions #a to #ae miles in diameter to huge elongated depressions as much as #fj miles long4 ,illustration3 ,crater ,lake1 ,oregon2 ,wizard ,island1 a cinder cone1 rises above the lake surface4 ,the ,evolution of a ,composite ,volcano3 ,illustration3 a4 ,magma1 rising upward through a conduit1 erupts at the ,earth's surface to form a volcanic cone4 ,lava flows spread over the surrounding area4 ,illustration3 b4 ,as volcanic activity continues1 perhaps over spans of hundreds of years1 the cone is built to a great height and lava flows form an extensive plateau around its base4 ,during this period1 streams enlarge and deepen their valleys4 ,illustration3 c4 ,when volcanic activity ceases1 erosion starts to destroy the cone4 ,after thousands of years1 the great cone is stripped away to expose the hardened 8volcanic plug0 in the conduit4 ,during this period of inactivity1 streams broaden their valleys and dissect the lava plateau to form isolated lava-capped mesas4 ,illustration3 d4 ,continued erosion removes all traces of the cone and the land is worn down to a surface of low relief4 ,all that remains is a projecting plug or 8volcanic neck10 a small lava-capped mesa1 and vestiges of the once lofty volcano and its surrounding lava plateau4 ,shield volcanoes ,shield volcanoes1 the third type of volcano1 are built almost entirely of fluid lava flows4 ,flow after flow pours out in all directions from a central summit vent1 or group of vents1 building a broad1 gently sloping cone of flat1 domical shape1 with a profile much like that of a warrior's shield4 ,they are built up slowly by the accretion of thousands of highly fluid lava flows called basalt lava that spread widely over great distances1 and then cool as thin1 gently dipping sheets4 ,lavas also commonly erupt from vents along fractures 7rift zones7 that develop on the flanks of the cone4 ,some of the largest volcanoes in the world are shield volcanoes4 ,in northern ,california and ,oregon1 many shield volcanoes have diameters of #c or #d miles and heights of #a1ejj to #b1jjj feet4 ,the ,hawaiian ,islands are composed of linear chains of these volcanoes including ,kilauea and ,mauna ,loa on the island of ,hawaii--two of the world's most active volcanoes4 ,the floor of the ocean is more than #ae1jjj feet deep at the bases of the islands4 ,as ,mauna ,loa1 the largest of the shield volcanoes 7and also the world's largest active volcano71 projects #ac1fgg feet above sea level1 its top is over #bh1jjj feet above the deep ocean floor4 ,in some eruptions1 basaltic lava pours out quietly from long fissures instead of central vents and floods the surrounding countryside with lava flow upon lava flow1 forming broad plateaus4 ,lava plateaus of this type can be seen in ,iceland1 southeastern ,washington1 eastern ,oregon1 and southern ,idaho4 ,along the ,snake ,river in ,idaho1 and the ,columbia ,river in ,washington and ,oregon1 these lava flows are beautifully exposed and measure more than a mile in total thickness4 ,illustration3 ,mauna ,loa ,volcano1 ,hawaii1 a giant among the active volcanoes of the world2 snow-capped ,mauna ,kea ,volcano in the distance4 ,illustration3 ,the internal structure of a typical shield volcano4 ,lava domes ,illustration3 ,a sketch of the havoc wrought in ,st4 ,pierre ,harbor on ,martinique during the eruption of ,mont ,pele in #aijb4 ,volcanic or lava domes are formed by relatively small1 bulbous masses of lava too viscous to flow any great distance2 consequently1 on extrusion1 the lava piles over and around its vent4 ,a dome grows largely by expansion from within4 ,as it grows its outer surface cools and hardens1 then shatters1 spilling loose fragments down its sides4 ,some domes form craggy knobs or spines over the volcanic vent1 whereas others form short1 steep-sided lava flows known as 8coulees40 ,volcanic domes commonly occur within the craters or on the flanks of large composite volcanoes4 ,the nearly circular ,novarupta ,dome that formed during the #aiab eruption of ,katmai ,volcano1 ,alaska1 measures #hjj feet across and #bjj feet high4 ,the internal structure of this dome--defined by layering of lava fanning upward and outward from the center--indicates that it grew largely by expansion from within4 ,mont ,pele in ,martinique1 ,lesser ,antilles1 and ,lassen ,peak and ,mono domes in ,california are examples of lava domes4 ,an extremely destructive eruption accompanied the growth of a dome at ,mont ,pele in #aijb4 ,the coastal town of ,st4 ,pierre1 about #d miles downslope to the south1 was demolished and nearly #cj1jjj inhabitants were killed by an incandescent1 high-velocity ash flow and associated hot gases and volcanic dust4 ,only two men survived2 one because he was in a poorly ventilated1 dungeon-like jail cell and the other who somehow made his way safely through the burning city4 ,illustration3 ,the ,novarupta ,dome formed during the #aiab eruption of ,katmai ,volcano1 ,alaska4 ,illustration3 ,schematic representation of the internal structure of a typical volcanic dome4 ,other ,volcanic ,structures ,plugs 7necks7 ,congealed magma1 along with fragmental volcanic and wallrock materials1 can be preserved in the feeding conduits of a volcano upon cessation of activity4 ,these preserved rocks form crudely cylindrical masses1 from which project radiating dikes2 they may be visualized as the fossil remains of the innards of a volcano 7the so-called 8volcanic plumbing system07 and are referred to as volcanic plugs or necks4 ,the igneous material in a plug may have a range of composition similar to that of associated lavas or ash1 but may also include fragments and blocks of denser1 coarser grained rocks--higher in iron and magnesium1 lower in silicon--thought to be samples of the ,earth's deep crust or upper mantle plucked and transported by the ascending magma4 ,many plugs and necks are largely or wholly composed of fragmental volcanic material and of fragments of wallrock1 which can be of any type4 ,plugs that bear a particularly strong imprint of explosive eruption of highly gas-charged magma are called diatremes or tuff-breccia4 ,volcanic plugs are believed to overlie a body of magma which could be either still largely liquid or completely solid depending on the state of activity of the volcano4 ,plugs are known1 or postulated1 to be commonly funnel shaped and to taper downward into bodies increasingly elliptical in plan or elongated to dike-like forms4 ,typically1 volcanic plugs and necks tend to be more resistant to erosion than their enclosing rock formations4 ,thus1 after the volcano becomes inactive and deeply eroded1 the exhumed plug may stand up in bold relief as an irregular1 columnar structure4 ,one of the best known and most spectacular diatremes in the ,united ,states is ,ship ,rock in ,new ,mexico1 which towers some #a1gjj feet above the more deeply eroded surrounding plain4 ,volcanic plugs1 including diatremes1 are found elsewhere in the western ,united ,states and also in ,germany1 ,south ,africa1 ,tanzania1 and ,siberia4 ,illustration3 ,ship ,rock1 ,san ,juan ,county1 ,new ,mexico4 ,maars ,also called 8tuff cones10 maars are shallow1 flat-floored craters that scientists interpret have formed above diatremes as a result of a violent expansion of magmatic gas or steam2 deep erosion of a maar presumably would expose a diatreme4 ,maars range in size from #bjj to #f1ejj feet across and from #cj to #fej feet deep1 and most are commonly filled with water to form natural lakes4 ,most maars have low rims composed of a mixture of loose fragments of volcanic rock and rocks torn from the walls of the diatreme4 ,maars occur in the western ,united ,states1 in the ,eifel region of ,germany1 and in other geologically young volcanic regions of the world4 ,an excellent example of a maar is ,zuni ,salt ,lake in ,new ,mexico1 a shallow saline lake that occupies a flat-floored crater about #f1ejj feet across and #djj feet deep4 ,its low rim is composed of loose pieces of basaltic lava and wallrocks 7sandstone1 shale1 limestone7 of the underlying diatreme1 as well as random chunks of ancient crystalline rocks blasted upward from great depths4 ,illustration3 ,zuni ,salt ,lake ,maar1 ,catron ,county1 ,new ,mexico4 ,nonvolcanic craters ,some well-exposed1 nearly circular areas of intensely deformed sedimentary rocks1 in which a central vent-like feature is surrounded by a ring-shaped depression1 resemble volcanic structures in gross form4 ,as no clear evidence of volcanic origin could be found in or near these structures1 scientists initially described them as 8cryptovolcanic10 a term now rarely used4 ,recent studies have shown that not all craters are of volcanic origin4 ,impact craters1 formed by collisions with the ,earth of large meteorites1 asteroids1 or comets1 share with volcanoes the imprints of violent origin1 as evidenced by severe disruption1 and even local melting1 of rock4 ,fragments of meteorites or chemically detectable traces of extraterrestrial materials and indications of strong forces acting from above1 rather than from below1 distinguish impact from volcanic features4 ,other possible explanations for these nonvolcanic craters include subsurface salt-dome intrusion 7and subsequent dissolution and collapse72 collapse caused by subsurface limestone dissolution and_/or ground-water withdrawal2 and collapse related to melting of glacial ice4 ,an impressive example of an impact structure is ,meteor ,crater1 ,ariz41 which is visited by thousands of tourists each year4 ,this impact crater1 #d1jjj feet in diameter and #fjj feet deep1 was formed in the geologic past 7probably #cj1jjj-ej1jjj years before present7 by a meteorite striking the ,earth at a speed of many thousands of miles per hour4 ,in addition to ,meteor ,crater1 very fresh1 morphologically distinct1 impact craters are found at three sites near ,odessa1 ,tex41 as well as #aj or #ab other locations in the world4 ,of the more deeply eroded1 less obvious1 postulated impact structures1 there are about ten well-established sites in the ,united ,states and perhaps #hj or #ij elsewhere in the world4 ,illustration3 ,meteor ,crater1 ,arizona4 ,illustration3 ,mount ,st4 ,helens1 about noon1 ,may #ah1 #aihj4 ,types of ,volcanic ,eruptions ,during an episode of activity1 a volcano commonly displays a distinctive pattern of behavior4 ,some mild eruptions merely discharge steam and other gases1 whereas other eruptions quietly extrude quantities of lava4 ,the most spectacular eruptions consist of violent explosions that blast great clouds of gas-laden debris into the atmosphere4 ,the type of volcanic eruption is often labeled with the name of a well-known volcano where characteristic behavior is similar--hence the use of such terms as 8,strombolian10 8,vulcanian10 8,vesuvian10 8,pelan10 8,hawaiian10 and others4 ,some volcanoes may exhibit only one characteristic type of eruption during an interval of activity--others may display an entire sequence of types4 ,in a ,strombolian-type eruption observed during the #aife activity of ,iraz ,volcano in ,costa ,rica1 huge clots of molten lava burst from the summit crater to form luminous arcs through the sky4 ,collecting on the flanks of the cone1 lava clots combined to stream down the slopes in fiery rivulets4 ,illustration3 ,iraz ,volcano1 ,costa ,rica1 #aife4 ,in contrast1 the eruptive activity of ,parcutin ,volcano in #aidg demonstrated a 8,vulcanian0-type eruption1 in which a dense cloud of ash-laden gas explodes from the crater and rises high above the peak4 ,steaming ash forms a whitish cloud near the upper level of the cone4 ,in a 8,vesuvian0 eruption1 as typified by the eruption of ,mount ,vesuvius in ,italy in ,a4,d4 #gi1 great quantities of ash-laden gas are violently discharged to form a cauliflower-shaped cloud high above the volcano4 ,illustration3 ,parcutin ,volcano1 ,mexico1 #aidg4 ,illustration3 ,mount ,vesuvius ,volcano1 ,italy1 #aidd4 ,in a 8,pelan0 or 8,nue ,ardente0 7glowing cloud7 eruption1 such as occurred on the ,mayon ,volcano in the ,philippines in #aifh1 a large quantity of gas1 dust1 ash1 and incandescent lava fragments are blown out of a central crater1 fall back1 and form tongue-like1 glowing avalanches that move downslope at velocities as great as #ajj miles per hour4 ,such eruptive activity can cause great destruction and loss of life if it occurs in populated areas1 as demonstrated by the devastation of ,st4 ,pierre during the #aijb eruption of ,mont ,pele on ,martinique1 ,lesser ,antilles4 8,hawaiian0 eruptions may occur along fissures or fractures that serve as linear vents1 such as during the eruption of ,mauna ,loa ,volcano in ,hawaii in #aiej2 or they may occur at a central vent such as during the #aiei eruption in ,kilauea ,iki ,crater of ,kilauea ,volcano1 ,hawaii4 ,in fissure-type eruptions1 molten1 incandescent lava spurts from a fissure on the volcano's rift zone and feeds lava streams that flow downslope4 ,in central-vent eruptions1 a fountain of fiery lava spurts to a height of several hundred feet or more4 ,such lava may collect in old pit craters to form lava lakes1 or form cones1 or feed radiating flows4 ,illustration3 ,mauna ,loa ,volcano1 ,hawaii1 #aiej4 8,phreatic0 7or steam-blast7 eruptions are driven by explosive expanding steam resulting from cold ground or surface water coming into contact with hot rock or magma4 ,the distinguishing feature of phreatic explosions is that they only blast out fragments of preexisting solid rock from the volcanic conduit2 no new magma is erupted4 ,phreatic activity is generally weak1 but can be quite violent in some cases1 such as the #aife eruption of ,taal ,volcano1 ,philippines1 and the #aige-gf activity at ,la ,soufrire1 ,guadeloupe 7,lesser ,antilles74 ,the most powerful eruptions are called 8plinian0 and involve the explosive ejection of relatively viscous lava4 ,large plinian eruptions--such as during #ah ,may #aihj at ,mount ,st4 ,helens or1 more recently1 during #ae ,june #aiia at ,pinatubo in the ,philippines--can send ash and volcanic gas tens of miles into the air4 ,the resulting ash fallout can affect large areas hundreds of miles downwind4 ,fast-moving deadly pyroclastic flows 78nues ardentes07 are also commonly associated with plinian eruptions4 ,illustration3 ,kilauea ,volcano1 ,hawaii1 #aiei4 ,illustration3 ,taal ,volcano1 ,philippines1 #aife4 ,submarine ,volcanoes ,submarine volcanoes and volcanic vents are common features on certain zones of the ocean floor4 ,some are active at the present time and1 in shallow water1 disclose their presence by blasting steam and rock-debris high above the surface of the sea4 ,many others lie at such great depths that the tremendous weight of the water above them results in high1 confining pressure and prevents the formation and explosive release of steam and gases4 ,even very large1 deep-water eruptions may not disturb the ocean surface4 ,illustration3 ,schematic representation of a typical submarine eruption in the open ocean4 ,the unlimited supply of water surrounding submarine volcanoes can cause them to behave differently from volcanoes on land4 ,violent1 steam-blast eruptions take place when sea water pours into active shallow submarine vents4 ,lava1 erupting onto a shallow sea floor or flowing into the sea from land1 may cool so rapidly that it shatters into sand and rubble4 ,the result is the production of huge amounts of fragmental volcanic debris4 ,the famous 8black sand0 beaches of ,hawaii were created virtually instantaneously by the violent interaction between hot lava and sea water4 ,on the other hand1 recent observations made from deep-diving submersibles have shown that some submarine eruptions produce flows and other volcanic structures remarkably similar to those formed on land4 ,recent studies have revealed the presence of spectacular1 high-temperature hydrothermal plumes and vents 7called 8smokers07 along some parts of the mid-oceanic volcanic rift systems4 ,however1 to date1 no direct observation has been made of a deep submarine eruption in progress4 ,during an explosive submarine eruption in the shallow open ocean1 enormous piles of debris are built up around the active volcanic vent4 ,ocean currents rework the debris in shallow water1 while other debris slumps from the upper part of the cone and flows into deep water along the sea floor4 ,fine debris and ash in the eruptive plume are scattered over a wide area in airborne clouds4 ,coarse debris in the same eruptive plume rains into the sea and settles on the flanks of the cone4 ,pumice from the eruption floats on the water and drifts with the ocean currents over a large area4 ,illustration3 ,submarine eruption of ,myojin-sho ,volcano1 ,izu ,islands1 ,japan on ,september #bc1 #aieb4 ,geysers1 ,fumaroles1 and ,hot ,springs ,geysers1 fumaroles 7also called solfataras71 and hot springs are generally found in regions of young volcanic activity4 ,surface water percolates downward through the rocks below the ,earth's surface to high-temperature regions surrounding a magma reservoir1 either active or recently solidified but still hot4 ,there the water is heated1 becomes less dense1 and rises back to the surface along fissures and cracks4 ,sometimes these features are called 8dying volcanoes0 because they seem to represent the last stage of volcanic activity as the magma1 at depth1 cools and hardens4 ,erupting geysers provide spectacular displays of underground energy suddenly unleashed1 but their mechanisms are not completely understood4 ,large amounts of hot water are presumed to fill underground cavities4 ,the water1 upon further heating1 is violently ejected when a portion of it suddenly flashes into steam4 ,this cycle can be repeated with remarkable regularity1 as for example1 at ,old ,faithful ,geyser in ,yellowstone ,national ,park1 which erupts on an average of about once every #fe minutes4 ,illustration3 ,old ,faithful ,geyser1 ,yellowstone ,national ,park1 ,wyoming4 ,fumaroles1 which emit mixtures of steam and other gases1 are fed by conduits that pass through the water table before reaching the surface of the ground4 ,hydrogen sulfide 7,h,s71 one of the typical gases issuing from fumaroles1 readily oxidizes to sulfuric acid and native sulfur4 ,this accounts for the intense chemical activity and brightly colored rocks in many thermal areas4 ,hot springs occur in many thermal areas where the surface of the ,earth intersects the water table4 ,the temperature and rate of discharge of hot springs depend on factors such as the rate at which water circulates through the system of underground channelways1 the amount of heat supplied at depth1 and the extent of dilution of the heated water by cool ground water near the surface4 ,illustration3 ,black ,growler steam vents 7fumaroles71 ,norris ,basin1 ,yellowstone ,national ,park1 ,wyoming4 ,illustration3 ,mammoth ,hot ,springs1 ,yellowstone ,national ,park1 ,wyoming4 ,volcano ,environments ,there are more than #ejj active volcanoes 7those that have erupted at least once within recorded history7 in the world--#ej of which are in the ,united ,states 7,hawaii1 ,alaska1 ,washington1 ,oregon1 and ,california7--although many more are hidden under the seas4 ,most active volcanoes are strung like beads along1 or near1 the margins of the continents1 and more than half encircle the ,pacific ,ocean as a 8,ring of ,fire40 ,illustration3 ,the distribution of some of the ,earth's #ejj active volcanoes4 ,many volcanoes are in and around the ,mediterranean ,sea4 ,mount ,etna in ,sicily is the largest and highest of these mountains4 ,italy's ,vesuvius is the only active volcano on the ,european mainland4 ,near the island of ,vulcano1 the volcano ,stromboli has been in a state of nearly continuous1 mild eruption since early ,roman times4 ,at night1 sailors in the ,mediterranean can see the glow from the fiery molten material that is hurled into the air4 ,very appropriately1 ,stromboli has been called 8the lighthouse of the ,mediterranean40 ,some volcanoes crown island areas lying near the continents1 and others form chains of islands in the deep ocean basins4 ,volcanoes tend to cluster along narrow mountainous belts where folding and fracturing of the rocks provide channelways to the surface for the escape of magma4 ,significantly1 major earthquakes also occur along these belts1 indicating that volcanism and seismic activity are often closely related1 responding to the same dynamic ,earth forces4 ,in a typical 8island-arc0 environment1 volcanoes lie along the crest of an arcuate1 crustal ridge bounded on its convex side by a deep oceanic trench4 ,the granite or granitelike layer of the continental crust extends beneath the ridge to the vicinity of the trench4 ,basaltic magmas1 generated in the mantle beneath the ridge1 rise along fractures through the granitic layer4 ,these magmas commonly will be modified or changed in composition during passage through the granitic layer and erupt on the surface to form volcanoes built largely of non-basaltic rocks4 ,illustration3 ,mount ,sinabung1 ,sumatra 7,by ,j4 ,baylor ,roberts 7c7 ,national ,geographic ,society74 ,illustration3 ,island-arc environment ,in a typical 8oceanic0 environment1 volcanoes are aligned along the crest of a broad ridge that marks an active fracture system in the oceanic crust4 ,basaltic magmas1 generated in the upper mantle beneath the ridge1 rise along fractures through the basaltic layer4 ,because the granitic crustal layer is absent1 the magmas are not appreciably modified or changed in composition and they erupt on the surface to form basaltic volcanoes4 ,illustration3 ,mauna ,kea ,volcano1 ,hawaii4 ,illustration3 ,oceanic environment ,in the typical 8continental0 environment1 volcanoes are located in unstable1 mountainous belts that have thick roots of granite or granitelike rock4 ,magmas1 generated near the base of the mountain root1 rise slowly or intermittently along fractures in the crust4 ,during passage through the granitic layer1 magmas are commonly modified or changed in composition and erupt on the surface to form volcanoes constructed of nonbasaltic rocks4 ,illustration3 ,mount ,adams1 ,washington4 ,illustration3 ,continental environment ,plate-,tectonics ,theory ,illustration3 ,in the ,pacific ,northwest1 the ,juan de ,fuca ,plate plunges beneath the ,north ,american ,plate1 locally melting at depth2 the magma rises to feed and form the ,cascade volcanoes4 ,according to the now generally accepted 8plate-tectonics0 theory1 scientists believe that the ,earth's surface is broken into a number of shifting slabs or plates1 which average about #ej miles in thickness4 ,these plates move relative to one another above a hotter1 deeper1 more mobile zone at average rates as great as a few inches per year4 ,most of the world's active volcanoes are located along or near the boundaries between shifting plates and are called 8plate-boundary0 volcanoes4 ,however1 some active volcanoes are not associated with plate boundaries1 and many of these so-called 8intra-plate0 volcanoes form roughly linear chains in the interior of some oceanic plates4 ,the ,hawaiian ,islands provide perhaps the best example of an 8intra-plate0 volcanic chain1 developed by the northwest-moving ,pacific plate passing over an inferred 8hot spot0 that initiates the magma-generation and volcano-formation process4 ,the peripheral areas of the ,pacific ,ocean ,basin1 containing the boundaries of several plates1 are dotted by many active volcanoes that form the so-called 8,ring of ,fire40 ,the 8,ring0 provides excellent examples of 8plate-boundary0 volcanoes1 including ,mount ,st4 ,helens4 ,the accompanying figure shows the boundaries of lithosphere plates that are presently active4 ,the double lines indicate zones of spreading from which plates are moving apart4 ,the lines with barbs show zones of underthrusting 7subduction71 where one plate is sliding beneath another4 ,the barbs on the lines indicate the overriding plate4 ,the single line defines a strike-slip fault along which plates are sliding horizontally past one another4 ,the stippled areas indicate a part of a continent1 exclusive of that along a plate boundary1 which is undergoing active extensional1 compressional1 or strike-slip faulting4 ,illustration3 ,major tectonic plates of the ,earth4 ,extraterrestrial ,volcanism ,illustration3 ,mariner #i imagery of ,olympus ,mons ,volcano on ,mars compared to the eight principal ,hawaiian ,islands at the same scale 7,mariner #i ,image ,mosaic1 ,,nasa_/,,jpl74 ,volcanoes and volcanism are not restricted to the planet ,earth4 ,manned and unmanned planetary explorations1 beginning in the late #aifj's1 have furnished graphic evidence of past volcanism and its products on the ,moon1 ,mars1 ,venus and other planetary bodies4 ,many pounds of volcanic rocks were collected by astronauts during the various ,apollo lunar landing missions4 ,only a small fraction of these samples have been subjected to exhaustive study by scientists4 ,the bulk of the material is stored under controlled-environment conditions at ,,nasa's ,lunar ,receiving ,laboratory in ,houston1 ,tex41 for future study by scientists4 ,from the #aigf-aigi ,viking mission1 scientists have been able to study the volcanoes on ,mars1 and their studies are very revealing when compared with those of volcanoes on ,earth4 ,for example1 ,martian and ,hawaiian volcanoes closely resemble each other in form4 ,both are shield volcanoes1 have gently sloping flanks1 large multiple collapse pits at their centers1 and appear to be built of fluid lavas that have left numerous flow features on their flanks4 ,the most obvious difference between the two is size4 ,the ,martian shields are enormous4 ,they can grow to over #ag miles in height and more than #cej miles across1 in contrast to a maximum height of about #f miles and width of #gd miles for the ,hawaiian shields4 ,voyager-#b spacecraft images taken of ,io1 a moon of ,jupiter1 captured volcanoes in the actual process of eruption4 ,the volcanic plumes shown on the image rise some #fj to #ajj miles above the surface of the moon4 ,thus1 active volcanism is taking place1 at present1 on at least one planetary body in addition to our ,earth4 ,illustration3 ,spacecraft image1 made in ,july #aigi1 shows volcanic plume rising some #fj to #ajj miles above the surface of ,io1 a moon of ,jupiter 7,voyager #b photo1 ,,nasa74 ,volcano ,monitoring and ,research ,it has been said that the science of 8volcanology0 originated with the accurate descriptions of the eruption of ,vesuvius in ,a4,d4 #gi contained in two letters from ,pliny the ,younger to the ,roman historian ,tacitus4 ,pliny's letters also described the death of his uncle1 ,pliny the ,elder1 who was killed in the eruption4 ,actually1 however1 it was not until the #aith century that serious scientific inquiry into volcanic phenomena flourished as part of the general revolution in the physical and life sciences1 including the new science of 8geology40 ,in #ahdg1 an observatory was established on the flanks of ,vesuvius1 upslope from the site of ,herculaneum1 for the more or less continuous recording of the activity of the volcano that destroyed the city in ,a4,d4 #gi4 ,still1 through the first decade of the #bjth century1 the study of volcanoes by and large continued to be of an expeditionary nature1 generally undertaken after the eruption had begun or the activity had ceased4 ,illustration3 ,the ,u4,s4 ,geological ,survey's ,hawaiian ,volcano ,observatory1 on the crater rim of ,kilauea ,volcano4 ,perhaps 8modern0 volcanology began in #aiab1 when ,thomas ,a4 ,jaggar1 ,head of the ,geology ,department of the ,massachusetts ,institute of ,technology1 founded the ,hawaiian ,volcano ,observatory 7,,hvo71 located on the rim of ,kilauea's caldera4 ,initially supported by an association of ,honolulu businessmen1 ,,hvo began to conduct systematic and continuous monitoring of seismic activity preceding1 accompanying1 and following eruptions1 as well as a wide variety of other geological1 geophysical1 and geochemical observations and investigations4 ,between #aiai and #aidh1 ,,hvo was administered by various ,federal agencies 7,national ,weather ,service1 ,u4,s4 ,geological ,survey1 and ,national ,park ,service71 and since #aidh it has been operated continuously by the ,geological ,survey as part of its ,volcano ,hazards ,program4 ,the more than #ge years of comprehensive investigations by ,,hvo and other scientists in ,hawaii have added substantially to our understanding of the eruptive mechanisms of ,kilauea and ,mauna ,loa1 two of the world's most active volcanoes4 ,moreover1 the ,hawaiian ,volcano ,observatory pioneered and refined most of the commonly used volcano-monitoring techniques presently employed by other observatories monitoring active volcanoes elsewhere1 principally in ,indonesia1 ,italy1 ,japan1 ,latin ,america1 ,new ,zealand1 ,lesser ,antilles 7,caribbean71 ,philippines1 and ,kamchatka 7,u4,s4,s4,r474 ,what does 8volcano monitoring0 actually involve8 ,basically1 it is the keeping of a detailed 8diary0 of the changes--visible and invisible--in a volcano and its surroundings4 ,between eruptions1 visible changes of importance to the scientists would include marked increase or decrease of steaming from known vents2 emergence of new steaming areas2 development of new ground cracks or widening of old ones2 unusual or inexplicable withering of plant life2 changes in the color of mineral deposits encrusting fumaroles2 and any other directly observable1 and often measurable1 feature that might reflect a change in the state of the volcano4 ,of course1 the 8diary0 keeping during eruptive activity presents additional tasks4 ,wherever and whenever they can do so safely1 scientists document1 in words and on film1 the course of the eruption in detail2 make temperature measurements of lava and gas2 collect the eruptive products and gases for subsequent laboratory analysis2 measure the heights of lava fountains or ash plumes2 gage the flow rate of ash ejection or lava flows2 and carry out other necessary observations and measurements to fully document and characterize the eruption4 ,for each eruption1 such documentation and data collection and analysis provide another building block in constructing a model of the characteristic behavior of a given volcano or type of eruption4 ,volcano monitoring also involves the recording and analysis of volcanic phenomena not visible to the human eye1 but measurable by precise and sophisticated instruments4 ,these phenomena include ground movements1 earthquakes 7particularly those too small to be felt by people71 variations in gas compositions1 and deviations in local electrical and magnetic fields that respond to pressure and stresses caused by the subterranean magma movements4 ,some common methods used to study invisible1 volcano-related phenomena are based on3 #a4 ,measurement of changes in the shape of the volcano--volcanoes gradually swell or 8inflate0 in building up to an eruption because of the influx of magma into the volcano's reservoir or 8plumbing system02 with the onset of eruption1 pressure is immediately relieved and the volcano rapidly shrinks or 8deflates40 ,a wide variety of instruments1 including precise spirit-levels1 electronic 8tiltmeters10 and electronic-laser beam instruments1 can measure changes in the slope or 8tilt0 of the volcano or in vertical and horizontal distances with a precision of only a few parts in a million4 #b4 ,precise determination of the location and magnitude of earthquakes by a well-designed seismic network--as the volcano inflates by the rise of magma1 the enclosing rocks are deformed to the breaking point to accommodate magma movement4 ,when the rock ultimately fails to permit continued magma ascent1 earthquakes result4 ,by carefully mapping out the variations with time in the locations and depths of earthquake foci1 scientists in effect can track the subsurface movement of magma1 horizontally and vertically4 ,illustration3 ,scientist1 wearing asbestos gloves and gas mask1 samples volcanic gases from active vent4 #c4 ,measurement of changes in volcanic-gas composition and in magnetic field--the rise of magma high into the volcanic edifice may allow some of the associated gases to escape along fractures1 thereby causing the composition of the gases 7measured at the surface7 to differ from that usually measured when the volcano is quiescent and the magma is too deep to allow gas to escape4 ,changes in the ,earth's magnetic field have been noted preceding and accompanying some eruptions1 and such changes are believed to reflect temperature effects and_/or the content of magnetic minerals in the magma4 ,recording historic eruptions and modern volcano-monitoring in themselves are insufficient to fully determine the characteristic behavior of a volcano1 because a time record of such information1 though perhaps long in human terms1 is much too short in geologic terms to permit reliable predictions of possible future behavior4 ,a comprehensive investigation of any volcano must also include the careful1 systematic mapping of the nature1 volume1 and distribution of the products of prehistoric eruptions1 as well as the determination of their ages by modern isotopic and other dating methods4 ,research on the volcano's geologic past extends the data base for refined estimates of the recurrence intervals of active versus dormant periods in the history of the volcano4 ,with such information in hand1 scientists can construct so-called 8volcanic hazards0 maps that delineate the zones of greatest risk around the volcano and that designate which zones are particularly susceptible to certain types of volcanic hazards 7lava flows1 ash fall1 toxic gases1 mudflows and associated flooding1 etc474 ,a strikingly successful example of volcano research and volcanic-hazard assessment was the #aigh publication 7,bulletin #achc-;,c7 by two ,geological ,survey scientists1 ,dwight ,crandell and ,donal ,mullineaux1 who concluded that ,mount ,st4 ,helens was the ,cascade volcano most frequently active in the past #d1ejj years and the one most likely to reawaken to erupt1 8444 perhaps before the end of this century40 ,their prediction came true when ,mount ,st4 ,helens rumbled back to life in ,march of #aihj4 ,intermittent explosions of ash and steam and periodic formation of short-lived lava domes continued throughout the decade4 ,analysis of the volcano's past behavior indicates that this kind of eruptive activity may continue for years or decades1 but another catastrophic eruption like that of ,may #ah1 #aihj1 is unlikely to occur soon4 ,on #ah ,may #aihb1 the ,u4,s4 ,geological ,survey 7,,usgs7 formally dedicated the ,david ,a4 ,johnston ,cascades ,volcano ,observatory 7,,cvo7 in ,vancouver1 ,washington1 in memory of the ,survey volcanologist killed two years earlier4 ,this facility--a sister observatory to the ,hawaiian ,volcano ,observatory--facilitates the increased monitoring and research on not only ,mount ,st4 ,helens but also the other volcanoes of the ,cascade ,range of the ,pacific ,northwest4 ,more recently1 in cooperation with the ,state of ,alaska1 the ,,usgs established the ,alaska ,volcano ,observatory in ,march #aihh4 ,the work being done at these volcano observatories provides important comparisons and contrasts between the behavior of the generally non-explosive ,hawaiian shield volcanoes and that of the generally explosive composite volcanoes of the ,cascade and ,alaskan ,peninsula-,aleutian chains4 ,volcanoes and ,people ,volcanoes both harass and help mankind4 ,as dramatically demonstrated by the catastrophic eruption of ,mount ,st4 ,helens on ,may #aihj and of ,pinatubo in ,june #aiia1 volcanoes can wreak havoc and devastation in the short term4 ,the types of volcanic and associated hazards are not described in this booklet but treated in several of the publications listed in ,suggested ,reading4 ,however1 it should be emphasized that the short-term hazards posed by volcanoes are balanced by benefits of volcanism and related processes over geologic time4 ,volcanic materials ultimately break down to form some of the most fertile soils on ,earth1 cultivation of which fostered and sustained civilizations4 ,people use volcanic products as construction materials1 as abrasive and cleaning agents1 and as raw materials for many chemical and industrial uses4 ,the internal heat associated with some young volcanic systems has been harnessed to produce geothermal energy4 ,for example1 the electrical energy generated from ,the ,geysers geothermal field in northern ,california can meet the present power consumption of the city of ,san ,francisco4 ,the challenge to scientists involved with volcano research is to mitigate the short-term adverse impacts of eruptions1 so that society may continue to enjoy the long-term benefits of volcanism4 ,they must continue to improve the capability for predicting eruptions and to provide decision makers and the general public with the best possible information on high-risk volcanoes for sound decisions on land-use planning and public safety4 ,geo-scientists still do not fully understand how volcanoes really work1 but considerable advances have been made in recent decades4 ,an improved understanding of volcanic phenomena provides important clues to the ,earth's past1 present1 and possibly its future4 ,suggested ,reading ,decker1 ,robert1 and ,decker1 ,barbara1 #aihi1 ,volcanoes3 ,w4,h4 ,freeman and ,company1 ,new ,york1 #bhe p4 7,revised edition74 ,editors1 #aihb1 ,volcano3 in the series ,planet ,earth1 ,alexandria1 ,virginia1 ,time-,life ,books1 #agf p4 ,harris1 ,s4,l41 #aihh1 ,fire mountains of the ,west3 ,the ,cascade and ,mono ,lake ,volcanoes3 ,missoula1 ,montana1 ,mountain ,press ,publishing ,company1 #cgi p4 ,heliker1 ,christina1 #aiij1 ,volcanic and seismic hazards on the ,island of ,hawaii3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey1 #dh p4 ,macdonald1 ,g4,a41 #aigb1 ,volcanoes3 ,englewood ,cliffs1 ,new ,jersey1 ,prentice-,hall1 ,inc41 #eaj p4 ,simkin1 ,tom1 ,tilling1 ,r4,i41 ,taggart1 ,j4,n41 ,jones1 ,w4,j41 and ,spall1 ,henry1 compilers1 #aihi1 ,this dynamic planet3 ,world ,map of volcanoes1 earthquakes1 and plate tectonics3 ,u4,s4 ,geological ,survey1 ,reston1 ,virginia1 prepared in cooperation with the ,smithsonian ,institution1 ,washington1 ,d4,c4 7scale #a3cj1jjj1jjj at equator74 ,tilling1 ,r4,i41 ,heliker1 ,christina1 and ,wright1 ,t4,l41 #aihi1 ,eruptions of ,hawaiian volcanoes3 ,past1 present1 and future3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey1 #ed p4 ,tilling1 ,r4,i41 ,topinka1 ,lyn1 and ,swanson1 ,d4,a41 #aiij1 ,eruptions of ,mount ,st4 ,helens3 ,past1 present1 and future3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey1 #ef p4 7,revised edition74 ,tilling1 ,r4,i41 #aiia1 ,monitoring active volcanoes3 ,reston1 ,virginia1 ,u4,s4 ,geological ,survey1 #ac p4 7,revised edition74 ,wood1 ,c4,a41 and ,kienle1 ,jurgen1 #aiij1 ,volcanoes of ,north ,america3 ,united ,states and ,canada3 ,new ,york1 ,cambridge ,university ,press1 #ced p4 ,illustration3 ,the port city of ,st4 ,pierre on the island of ,martinique2 ,mont ,pele is in the background4 ,in #aijb1 this city was entirely destroyed by pyroclastic flows2 about #cj1jjj people died4 ,illustration3 ,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 administration ,u4,s4 ,geological ,survey ,information ,services ,p4,o4 ,box #bebhf ,denver1 ,,co #hjbbe ,for sale by the ,u4,s4 ,government ,printing ,office ,superintendent of ,documents1 ,mail ,stop3 ,,ssop1 ,washington1 ,,dc #bjdjb-icbh ,u4,s4 ,,government ,,printing ,,office3 #aiif #dba-bha ,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