VOLCANOES Outleistaxorazw4t-* -0 Oposons Stated in Dos Docu Men' Do Nacestaulv Cearesent Ofkol Nig Peeeter4ofpeke

Maars Ivars occur in the western Also, called,"tuff cones," maars If ited States, in the Eifel region of are shallow, fiat-floored craters ermany, and in other_geologically that scientists interpret have young volcanic regioneof the formed above dlatremei a a res world. An excellent example of a of 'a violet)) expansion ofag tic mass; Is Zuni Silt Lake in New Mexico, a shallow saline lake that .gas or stee.ni, deep erosi f a 1 maar, presumably would expose a occupies a flat-flowed crater diatreme. Maars range in,size about 6,500 feet across and 400 from 200 to 6,500 feet across and feet deep. itslow rim,is composed from 30 to 650 feet deep, and most of tabu) pieces of basaltic _lava are commonly filled with water_ to. and wallrocks (sandstone, shale, form natural lakes. Most maws limestone) of the underlying dbk have low rims composed of a treme. as well as.random chunks mixture of loose fragments of of ancient cryst..`line rocks blasted volcanic. rocks and rocks torn - upward from griat depths. --v from the wails of the diatreme.-

, --- t 4.,14...... W. 44. A , -- g- 7-4tW' 4 4. Js:*R. '. .A...)-'--7 124;'It..stoert`'..- ,...--41 .1- 7" 1...,.41..Z.- 34';.145b, glit,r; .1". .t :XI& garaf Efi &MIA=''en :.-t Zuni Salt Lake Maar, Catron County,New Mexico-

20 23 ti b. otrAPUIREttl OP illUGAIrni .- - t"sr. - NATIONAL INSTITUTEOFEDUCATION EDIJC-ArrOSiA4. RESOURGESINFORMATION CENTER 'CRCs Tr thx.vmeht ha,been ,eprockhad as ,,- - mooed ICATI Ihe mum u uojafteubon U.Sj Department cif the IntetiorkGeotegiCal Smiley mu. Noge. nave roc. foams10 yam ut - fOraolluCtalkquOMY e--04,;:- podita OF VOLCANOES outleistaxorazw4t-* -0 oposons stated in dos docu men' do nacestaulv ceAresent ofkol Nig peeeter4ofpeke,

"PERMISSION TO REPRODUCE ThiS . - MATERIAL/1AS BEEN GRANTED BY 4 .4°5: betiOley

TO THE EDUCATIONAL RESOURCES. INFORMATION CENTER {ERICL

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The eruption of Cerro Negro Volcano, near Leda, Nicarague,OuringNoverribor 1968. 1 1 Volcanoes by Robe1. Tilling

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Covet and Title Page. Lava fountains and flows. Mauna Loa. Hawau, July 6. 1976. Volcanoes destroy and volcanolA create. The catastrophic eruption of Mount St. Helens on May 18, 1980, made clear the awesome destructive power of a volcano. Yet, over a time span longer than human memory And record, volcanoes have played a key role in forming and modifying the planet upon which we live. More than 80 percent of the Earth's surfaceabove and below sea levelis of volcanic origin. Gaseous emissions from volcanic-vents over hundreds of Illations of years formed the Earth's earliest oceans and atmosphere, which supplied the ingredients vital to evolve and sustain life. Over geologic eons, countless volcanic eruptions have produced mountains, plateaus, and plains, which subSequent erosion and weathering have sculpted into majestic landscapes and formed fertile soils. Ironically, these volcanic soils and inviting butanes have attracted, and continuet attract, people to live on the flanks of volcanoes. Thus, as population ansity increases inregioni of active or potentially active volcanoes, mankind must become increasingly aware of the hazards and learn mot to "crowd" the volcanoes. People living in the shadow,of volcanoes must live in harmony with them and expect, and shot4d plan for, periodic violent unleashings of their pent-up energy. This booklet presents a generalized summary of the -nature, work- ings, products, and hazards of the common types of volcanoes around the world, along with a brief introduction to tile-tectiliques of volcano monitoring and research. \

Op August 24, A.D. 79, Vesuvius Volcano suddenly ex- ploded and destroyed the Roman cities of Pompeii arid Herculbneum. Although Vesuvius had shown stirringi of he when a succession .. of earthquakes in A.D. 63 caused some dainage, it had been literally quiet for hundreds of years and was considered "extinct." Its . sarface and crater were__green l= and- covered with vegetation, so i the eruption was totally [ unexpected. Yet in a few hours, hot volcanic ash and dust burled the two cities so thoroughly that thpir ruins were not uncovered for nearly .1,700 years, when the discovery of an outer wall in 1748 started a period of modern archeology. Vesuvius has continued its activity intermittently intermittently active for months % ever since A.D. 79 with numerous or years, possibly even decades. minor eruptions and several The word "volcano" comes major eruptions occurring in from the little Island of Vulcano 1631, 1794,1872, 1906 and in 1944 in the Mediterranean Sea off . in the midstof the Italian campaignSicily. Centuries ago, the people of World War II. living in this area believed that In the United States On March Vulcano was the chimney of the 27, 1980, Mount St. Helens Volcano forge of Vulcanthe blacksmith in the Cascade Range, south- of the Roman gods. Tkey thought western Washington, reawakened that the hot lava fragments and after more than a century of clouds of dust erupting from dormancy and provided a dramaticVulcano came from Vulcan's forge . and tragic reminder that there as he beet out thunderbolts for are active volcanoes in the Jupiter, king of the gods, and 'lower 48" States as well as ir. weapons for Mars, the god of war. Hawaii and Alaska. The catastropheIn Polynesia the people attributed is motion of Mount St. Helens eruptive activity to the beautiful but on May 18, 1980, and related wrathful Pele, Goddess of Vol- mudflows and flooding caused canoes, whenever she was angry significant loss of life (62 dead or spiteful. Today we know that or missing) and property damage volcanic eruptions 'ire nor super- (over $1.2 billion). Mount St. natural but can be studied and Helens Is expected to remain interpreted by scientists.

3 ..0 e The Nature of Volcanoes

Volcanoes are mountains, but or vent through which the molten they are very different from otherrock and associates gases are mountains; -they- are not formed expelled. by folding and crumpling or by Driven by buoyancy and gas uplift and erosion. Instead, pressure the mol'sn rock, which volcanoes are built. by the accumu-is lighter than the surrounding lation of their own eruptive solid rock, forces its way upward prodUctslava, bombs (crusted and may ultimately break through over lava blobs),ashflows, and zones of weaknesses In the tephra, (airborne ash and dust). Earth's crust. if so, an eruption A volcano is most commonly abegins, and the molten rodk may conical hill or mountain built pour from the vent as nonexplosive around a vent that connects withlava flow's, orit may shoot reservoirs of miten rock belowviolently into the air as dense the surface of the Earth, The termclouds of lava fragment;. Larger volcano also refers to the openingfragments fall back around the

. .. Fountalning lava and volcanic debris during the 1959 Kilauea lkieruption of Kilauea Volcano, Hawaii. 7 4 I

vent, and accumulations of fall- aluminum, iron, magnesium, back fragments may move calcium, sodium, potassium, downslope as ash flows under titanium. and manganese. Magmas the Wive of gravity. Some of the also contain many other .chemical finer ejected materials may be elements in trace quantitiO. carried by the wind only to fall Upon cooling, the liquid magma to the ground many allies away. may precipitate crystals of various The finest ash particles may be minerals until solidification is injected miles into the atmospherecomplete to form an igneous or and carried many times around magmatic rock. the world by stratospheric winds The accompanying diagram of be;ore settling out, a volcano in an oceanic.environ- Molten rock below the surface ment shows that heat concentrated of the Earth that rises in volcanic inthe `Earth'supper mantle raises vents is known as magma, but temperatures sufficiently to melt after it erupts from a volcano it the rock locally by fusing the is called lava. Originating many materials with the loweStmeitiag t..ns of miles beneath the ground. temperatures, resulting intsmall, the ascending magma commonly isolated blobs of magma. These contains some crystals, fragmentsblobs thin collect, rise through of surrounding (unmelted) rocks, conduits,and fractures, and some and dissolved gases, but it is ultimately may recollect in larger primarily a liquid composed prin. pockets or reservoirs ("holding L.ipally of oxygen, silicon, tanks") a few miles beneath the

_eTsmim I411°14111111._

An Idealized diagia of a_voicand 4n an oceanic environment {felt) and on a continental - ernoireninent (right). g Earth's surfa9e. Moun ting presiureother parts of the majestic Sierra within the. retervoir may drive the Nevada mountains of California. magma further upward through Lava is red-hot when It pours structurally weak zones to erupt asor blasts out of a vent but soon lava at the surface. irlticontinentalchanges to dark red, gray, black, environment magmas are gener- or some other color as it cools ated in the Earth's crust as well and _solidifies. Very hot, gas -rich as at varying depths in the upper lava containing abundant iron and . mantle. Ilia variety of molten magnesium is fluid and flows like rocks the crust, plui the hot tar, whereas coolerivas-poor possibility of mixing with molten lava high in silicon, sodium, and materials from the underlying potassium flows sluggishly, like mantle, leads to the production of thick honey in some cases or triagmas with widely different in others like pasty, blocky chemical compositions, masses. If magmas cool rapidly, as might be expected near or on the Earth's.surlace, they solidify to form igneous rocks that are finely crystallirke or glassy with few cryMals. Accordingly, lavas, which of course are very rapidly cooled, form volcanic rocks typically characterized by a small percent- age of crystals or fragments set in a matrix of glass (quenched or super-cooled magma) or finer grained crystalline materials, Ifmagmas never breach the surface to erupt and remain deep underground, they cool much zre__ more slowly and thus allow ample time to sustain crystal precipita- tion and growth, resulting in the formation of coarser grained, nearly completely crystalline, igneous rocks. Subsequent to final crystallization and solidification, such rocks can be exhumed by erosion many thousands or millions Two Polynesian terms are used to Identify of years later and be exposed as me sumacs character of Hawaiian lava large bodies of so-called granitic flows. As, a basalt with &tough. blocky focks, as. for example, those appearance, much like furnace slag, is spectacularly displayed in shown at the top. Pahoerme. a mote fluid variety with a mooth,-satiny and some- -Y6samite National 'Park and limes glassy appearance. is shown at the bottom

8. 9 .

. , . All magmas contain dissolved your thumb abruptly, there is gases, and as they rise to the a miniature explosion of gas and surface to erupt,'the Onfining' liquid. The gases in lava behave pressures are reduced 'and the in somewhat the same way... dissolved gases are liberated Their sudden expansion causes 1 either quietly or explosively. the terrible explosiorg that throw If the lava ;s a thin, fluid (not. out great masses of solid rock viscous), the gases may escape as well as lava, dust, and ashes. _-hilasilkBut if the lava is thickand The violent separation of gas pasty (highly viscous), the gases from lava may produce rock froth will not move-freely but will build called_pumice. Some of this froth up tremendous pressure, and is so lightbecause of the many ultimately escape with 'explosive gas bubbles --that it floats on

violence:. , Gases in lava may bk water. In many eruptions, the compared with the gas in a bottle froth is shattered explosively into of a catbOnated soft drink. if yog.. small fragments that are hulled put your thtimb over the top of the high into the air in fhe form of bottle and shake it vigorously, the volcanic .cinders (red or black), gas separates' from the drink and volcanic ash (commonly tan or forms bubbles. When you remove gray), and volcanic dust. .

During the 1959 eruption of Kilauea tkl, tounlaining lava and volcanic debris completely blocked several or the roads in jba Hawaii Volcanoes National Park, / / 7/ Principal Types of Volcanoes

/ around the vent to form a qiccular Geologist, generally group't volcanoes)nto. four main lunar- or oval cone. Most cinder cones cinder cones, composite volcanoes.have a bowl-shaped crater at shield- volcanoes, and lava the summit and rarely rise more ddmes. thane, thousand feetor so alaci9e their surroundings. Cinder cones Cinder cones are numerous in western North Cinder cones are the siMpleit America as well as throughout type of volcano. They are built. other volcanic tetrains of the. from .particles and blobs of world. congealed lava ejected from In:1943 a cinder cone started single vent. As the gas-charged growing on a farm neer.thevillage lava is blown violently into the of Paricutin in Mexico. Explosive air, it breaks into small fragments eruptionkcaused by gas rapidly that solidify and fall as cinders expanding and escaping from

Es.

Schematic rapipsentatiort of the. internal structure sit a .tygneal.cinny- cone., molten lava formed cinders that a common sequence in the fell back around the vent, building formation of cinder cones. 'up the cone to a height of During 9 years of activity 11200 feet. The lastexplosive Paricutin built a prominent cone, eruption left a funnel-shaped coveretraboat 100 s4uare Man- depression called a crater at the with ashes, and destroyed the top of the cone. After the excess town of San ,Juan. Geologists gases had ,largely dissipated, the from many parts of the world molte'n roc,k quietly poured out studied Paricutin during its lifetime on the surrounding surface of and learned a great deal about the cone and Moved downslope volcanism, its products, and.,the. as lava flows. This cird,er_of modification of a volcanic land- events -- eruption,formation form by erosion. cane and crater, lava flowis :l

Parfoutiri yolcaoo,exlcp, M a .cinder cone rising approximately 1,200 Met above the surrounding pi 11. 0 1i

Composites volcanoes Mount Shasta in California, ... Mount Hood in Oregon, and Some 0 the Earth's grandest Mount St. Helens and Mount mountains are composite --Rainier in Washington. volcanoessometimes called Most composite volcanoes have stratovolcanoes.,They are a crater at the summit which typically steep - sided, symmetrical contains a central vent or a cones of large dimension built clustered group of vents. Lavas of alteinating layers of lava flows. either flow through breaksin volcanic ash, cinders, blOcks, the crater wall or issue from and ,bombs and may rise as fissures on the flanks of the much as 8,000 feet above their cone. Lava, solidified within the bases, Some of the most conspicu- fissures, forms dikes that act as ous and beautiful mountains in ribs which ,greatly strengthen the world are composite volcanoes, the cone. including Mount Fuji in Japan, The essential feature of a Mount Cotopaxi in Ecuador, composite volcano is a conduit

- - , - Schematic representalion at themettle(etre-toreor a Apkcal composite volcano

_ 10 .. -----10 system through which magma (the dikes) becomes exposed, from a reservoir deep in the and it too is slowly reduced by Earth's crust rises to the surface. erosion. Finally, all that remains The volcano is built up by the is the plug and dike complex accumulation of material projecting above the land surface erupted through the conduit and a telltale remnant of the vane increases in size as lava, ished volcano. cinders, ash, etc., are added An interesting variation of a to its slopes. composite volcano can be seep...., When a composite yolcano at Crater Lake in Oregon. From becomes dormant, grown begins what geologists can interpret of to destroy As the cone its past, a high volcanocalled is stripped a ay, the hardened Mount Mazamaprobably magma filljng the conduit(the similar in appearance to present- volcanic 'Plug) and fissures day Mount Rainier was once

As.

Shisbaidin volcano an imposing composite cone. towers 9.372feet above sea level in the Aleutian Islands. Alaska. 14 or- .-r . I. .,,y. __---- Crater LaicCOregon. Wizard Island. _a Cinder cone. rises above the lake surface. located at this spot. Following surfac?3Wizard Island in, and a series of tremendous explosions near tilt>rim, of the lake. about 6,600 years ago, the volcanoDepressions such as Crater Lake, lost its top. Enormous volumes formed by collapse of volcanoes, of voicanIQ ash and dust were are known as calderas. They are expelled and swept down the usually .{arge, steep-walled, slopes as ash flows and ava- basin - shaped depressions formed lanches. These large-volume by the collapse of a large area explosions rapidly drained the over, and around, a volcanic lava benSath the mountain and vent or vents. Calderas range weakened the upper part. The in form and size from roughly top then collapsed to form a large circular depressions 1to 15 depression, which later filled withmiles in diameter to huge water and is now completely oc- elongated depressions as much cupied by beautiful Crater Lake. as 60 miles long. A last gasp of eruptions produced a small cinder cone which rises above the water The Evolution a. Magma, rising upward of a Composite Volcano: through a conduit, erupts at the Earth's surface to form a volcanic con. Lava flows spread overihe surrounding area. C.

b. As volcanic activity con- z tinues, perhaps over spans of hundreds of years, the cone is built to a great height and lava flows form an extensivo plateau around its base. During this period, streams enlarge and deepen their valleys.

c. When volcanic activity canes, erosion starts to destroy the cone. After thou- - of years, the great cone strppeii away to expose the hardened "volcanic 1..ug" in 2eg,Lr. the conduit. During this period of inactivity, streams broaden their valleys and dissect lite lava plateau to font, Isolated lava-capped mesas. 0

d. Continued erosion removes all traces of the cone and the land is worn down to a surface of low relief. All that remains is a protecting plug or volcanic neck," a small lava- capped mesa, and vestiges of .he once lofty volcano and its star- rounding lava plateau.

13 -- 16 Shield volcanoes Shield volcanoes, the third type of volcano, are built almost en- tirely of fluid lava flows. Flow after flow pours out in all directions from a central summit vent, or ..^'"ZIMtt°11111113"111"...... t,_ group of vents, building a broad, gently sloping cone of fiat. domical shape. with -a profile much like that of a warrior's shield. They are built up slowly by the accretion of thousands of flows of highly fluid basaltic (from basalt, a hard, dense dark voNanic rock) lava that spread widely over great distances, and then cool as thin, gently dip- ping sheets. Lavas also commonly erupt from vents along fractures (rift zones) that develop on the flanks of the cone. Some of the largest volcanoes in th (odd are shield votsanoos. In northern Cali- fornia and Oregon, many shield volcanoes have diameters of 3 or 4 miles and heights of 1.500 to 2.000 feet. 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 Mauna Loa Volcano. Hawaii. a.giant among volcanoes. The floor of the ocean the active volcanoes of the. world. Snow. is more than 1,.000 feet deep at capped Mauna Kea Volcano in the distance the bases of the islands. As Mauna Loa. the largest of the shield volcanoes {and also the world s largest flow upon lava flow, forming broad active volcano). piojects 13,677 plateau:. Lava plateaus of this type feet aDOve sea level, its top is overcan be seen,:n Iceland. southeast- 28.000 feet above the deep ocean ern Washington. eastern Oregon. floor. and southern Idaho. Along the In some shield-volcano erup- Snake River in Idaho. and the tions. basaltic lava pours out Columbia River in Washington and quietly from long fissures instead ofOregon. these lava flows are central vents and Hoods the sur. beautifully exposed and measure rounding countryside with lava more than a mile in total thickness.

14 :* 17/ / a A!. .. ) -' .. -- i ..0% 74,,,..- -.. .-b..A... 'r: . tr' ;,t,,-1-. ; , - - .. ---.1:-;. -i.,. . ' 16,..1..."....*. _e.....-A....4...... _ _...._ ,t3.-,--_;,...44:,_.. -",-,...... , 4. '' - ..6".?' 'r4. . 1,...... ,,....,., 4. -. -'4.-..1*,..... ,' 4 :4-ef.: N.-?..";:sT,'":./.... -kWr --....-2,.. -

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Internal structure of a lypfcal shield volcano-

16 Lava Domes 415:610P11101"Iredr . Volcanic or lava domes are _ joi, formed by relatively small bulbous masses of laya too viscous toflow' consequently, any great br: on extrusion, he lava piles over and around its vent. A dome grows largely by exp nsion from within, As it grows itsuter surface cools and hardens, then shatters,spilling _ loosefragment down its sides, Some domes form craggy knobs or spines over the volcanic vent, whereas others form short, steep- sided lava flows known as coulees." Volcanic domes co's-11- mo* occur within the craters or on the flanks of large composite volcanoes. The nearly circular defined by layering 'of lava fanning Novarupta came that formed upward and outward from the during the 1912 eruption of Katmaicenterindicates that it grew Volcano, Alaska,: measures 800 largely by expansion from within, feet across and 200 feet high. The Mount Pelee in Martinique, West internal structure of this dome- Indies, and Lassen Peak and Mono - grow_ 4 I 4 _0"

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A sketch of the havoc wrought in 51 Pierre Harbor on Martinique during the eruption of Mount Pelee in 1902-

1 t3 _, 1,,

The Novarupta Dome famed during the 1912 eruptionof Katmai Volcano. Alaska

domes in California are examplei killed by an incandescent, high- of lava domes. An extremely de- yelocity ash flow and associated structive eruptionaccompanied hot gases and volcanic dust. Only the growth of a dome at Mount two men sui :ved; one becausehe Pelee in,1902. The poastal town ofwas in a poorly ventilated, St. Pierre,-about 4 miles downsjopedungeon-like jail cell and the other to the south,was demolished and who somehow made his way safely nearly 30,000 inhabitants were through the burning city,

Schematic reprasentaftn of the Internal Onrctureof a typical volcanic do 0. -/ it Other Volcanic Structurescreasingly elliptical in plan or elongated to dike-like forms. Plugs (necks) Typically, volcanic plugs and necks

to be more resistant to ), tend ' erosionthan their enclosing nick Congealed magma, along with formations, Thus, after the volcano fragmental volcanic and walirock becomes inactive and deeply materials, can be preserved in the eroded, the exhumed plug may feeding conduits of a volcano upon cessation .)f activity. These preserved rocks form crudely cylin- drical masses, from which project radiating dikes; they may be visualized as the fossil remains of the marls of a 4oicano !the so-cauedvolcanic plumb4rig system ) and are referred to as volcanic plugs or necks. The igneous material in a plug may have a range of composition -similar to that of associated lavas or ash, but may also include fragments and blocks of denser, coarser grained rockshigher in iron and magnesium, lower in siliconthought Co be samples of the Earth's deep crustror upper Fyi_antie plucked and transported by the ascending magma. 'Many plugs and-'necks are largely nr wholly composed of fragmental volcanic material and of fragments of walirock, which can be of any type. Plugs that bear a particularly ,strong imprint of explosive erup- bon of highly gas-charged magma are called diatremes or tuff- breccix-,. 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 volcano, Plugs are known, or postulated, to be commonly funnel phaped and to taper downward into bodies in- stand up in bold relief as an Including diatremes, are found irregular, columnar structure. Oneelsewhere in the western United of the best krioWn and most spec- States and also in Germany. tacular diatremes in the United South Africa. Tanzania. and States is Ship Rock in New MexiCo,Siberia. which towers some 1,700 feet above the more deeply eroded surrounding plain. Volcanicplugs, Shirt Rock, San Juan County, New Mexico.

t- . -

, . 46!

-- :740,- -*" Maars lars occur In the western Aleo.called,"tuff cones," meats ited States, in the Eifel region of are shallow, flat- floorea craters ermany, and 19 other.geologically that scientiqs interpret have young volcanic regiOns of the formed abbve dlatremeia a res world. An excellent example of a of a violet); expansion ofagt is meat is Zuni Silt Lake in New .gas or steam, deeperosiona Mexico, a shallow saline lake that maar, presumably would expose a occliples a flatr.flocred_ crater diatreme. Mears range in.size about 6,500 feet across and 400 from 200 to 6,500 feet across end feet deep. Its-low anis composed from 30 to 650 feet deep, and most of lobse pieces of basaltic lava are commonly filled with water. to and wallrocks (sandstone, shale form natural lakes. Most maws limestone) of the underlying dia, have low rims composed of a treme. as well as. random chunki mixture of loose fragmants of o( ancient cryst...'llne rocks blasted volcanic rocks and rocks torn upward from great depths. from the walls of the dlatreme.

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."! Z 4.- .L -4- :- 4.- 1. .. k""- :**.X., t if- k L,44. . -av :C driWar 4%-% - . fir;: -511,,,V11- Zuni Salt Lake Maar, Catron County.New Mexico.

20 Cryptovoicanic structures to be nonvoicanic in origin, such , Some well-exposed, nearly -as: impact of extraterrestrial circular areas of intensely de-, bodies; subsurface salt-dome forme,: sedimentary rocks, in intrusion (and subsequent dissolu-' which a central vent-14%e feature is tion and collapse), collapse .aused surrounded, by a ring-shaped by subsurface limestone dissolu- depression, resemble volcanic tion and, or ground-water with- structures_in.gross form. As no drawal; and collapse related to clear evidence ol vo:canic origin melting of glacial ice. An impres- could be found in or near these sive example of an impact structure structures, scientists initially is Meteor Crater, Ariz., which is, desCribed them as -cryptovol- visited by thousands of tourists canic," a term now not often used.each year. This impact crater, Recent studies have shown that not4,000 feet in diameter and 600 all craters are of volcanic origin. feet deep, was formed in the geo- Impact craters, formed by colli- logic past (probably 30,000-50,000 sions with the Earth of large mete- years before present) by a meteor- orites, asteroids, or comets, share ite striking the Earth at a speed of with volcanoes the imprints of many thousands of miles per.hour. violent origin, as eyidenced by In addition to Meteor Crater, severe disruption, _and even local very fresh, morphologically distinct, melting, of rock. Fragments of me-, impact craters are found at three teorltes or chemically detectable sites near Odessa, Tex., as well traces of extraterrestrial materials as 10 or 12 other locations in the and indications .of strong forces world. Of the more deeply eroded. acting from above, rather than fromless obvious, postulated impact below, distinguishimpact from structures, there are about ten well- volcanic features, established sites in the United Scientists now generally con- States .and perhaps80 or 90 else- sides% cryptovolcanic structures where in the world.

.004.4".

MeteorCrater.Arizona.

1 t Types of Volcanic Eruptions

During an episode of activity, a in a Strornboliantype erup- volcano commonly displays a tion observed during the 1965 distinctive pattern of behavior. activity of Irazu Volcano in Cotta . Some mild eruptions merely die- Rica, huge clots of molten lava charge steam and other gases, burst from the summit crater to. whereas other eruptions quietly form luminous arcs through the extrude quantities of lava. The sky. Collecting on the flanks of most spectacular eruptions consist the cone, laya clots combined to of violent explosions that blast stream down .he slopes in fiery great clouds of gas-laden debris rivulets. into the atmosphere. in contrast, the eruptive activity The type of volcanic aruption is of Paricutin Volcano in 1.'247 often labeled with theAme of a demonstrated a `Nulcanian"-type well-known volcano where. char- eruption, in which a dense cloud acteristic behavior is similar of ash-laden gas explodes from the hence the.use of such terms as crater and rises high above the "Strombollan," "Vulcanjan," peak. Steaming ash forms a "Vesuvian, "Pe lean," "Hawaiian," whitish cloud near the upper level "Phreatic" and others. Some vol- of the cane. .. canoes may exhibit only one .har- In a "Vesuvian" eruption, as acteiistic type of eruption du. ng an.typified by the eruption of Mount interval of activityothers may Vesuvius in Italy in A.D. 79, great display an entire sequence of quantities of ash-laden gas are types. violently discharged to form a

.E'er ke ,jfer /f*wom... IA.-

trazO Volcano, Costa Rica, 1965. a

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Pariautin.VOicsnO,,Mexico, 1947 '1"-allillwz"-King77: -*!41. Mount Vesuvius Vol- acano, Italy, 1944.

it/ -1 ItN 0.;.f.-4V. ill: 4 -a P4 i 14.--

25 cauliflower-shaped cloud high Kilauea Iki Crater of Kilauea Vol. above the volcano. cano, Hawaii. In fissure-type In a "Pe lean" or "Nuee Ardeote"eruptions, molten, incandescent (glowing cloud) eruption, such as lava spurts from a fissure on the occurred on the Mayon Volcano involcano's nft zone and feeds lava the Philippines in 1968, a large streams that flow downslope. In quantity of gas, dust, asilLand. central-vent eruptions, a_ fountain . incandescent livifrajments are of fiery lava spurts to a height of blown out of a central crater, fall several hundred feet or more. back, and form tongue-like, glow- Such lava may collect in old pit ing avalanches that move down- craters to form lava lakes, or fo m slope at velocities as great as 100 cones, or feed radiating flows. 'Mlles per hour. Such eruptive The eruption of Taal Volcano in activity can cause great destruc- the Philippine Islands in 1965 tion and loss of life if it occurs in typifies "Phreatic" (or steam-blast) populated areas, as demonstrated behavior, Here, a great column of by the devastation c3t, Pierre steam, dust, ash, and cinders is during the 1902 eruption of blasted to a height of several Pelee on Martinique. West Indies. thousand feet. This type of violent "Hawaiian" eruptions may occur eruption is believed to occur when along fissures or fractures that a large quantity of ground or sur- serve as linear_vents, such as face water comes in contact with during the eruption of Mauna Loa hot rock or magma in a volcanic Volcano in Hawaii in 1950, or they vent and is instantly and explosive- may occur at a central vent such ly flashed to steam. as during the 1959 eruption in

Mauna Too Volcano, Hawaii. 'fag).

Submarine Volcanoes

Submarine volcanoes and vol- Theunlimitedsupply of water sur- canic vents are commonfeatures rounding submarine volcanoes can on certain zones of the oceanfloor.cause them to behave differently from Some are active at the present volcanoes on land. Violent, steam- time and, in shallow water,discloseblast eruptions take place when their presence byblasting steam sea water pours into activeshallow and rock-debris highabove the submarine vents. Lava, erupting surface of the sea. Many others onto a shallow sea floor or flowing lie at such great depthsthat the into the sea from land, may cool tremendous weight of the water so rapidly that It shatters into sand above them results in high, con- and rubble. The result is the pro- fining pressure and prevents the duction of huge amounts of frag- formation and explosive release mental volcanic debris. The famous of steam and gases. Even very "black sand" beaches of Hawaii large, deepwater eruptions may were created virtually Instantane- not disturb the ocean surface. ously by the violent Interaction

WIN-nano representation Oa typical aubmarine eruPlion in the open ocean, between hot lava and sea water. in shallow water, while other debris On the other hand, recent obser- slumps from the upper part of vat: 's made from deep-diving the cone and flows into deep water submersibles have shown that along the sea floor. Fine debris some submarine eruptions produce and ash to the eruptive plume are flows and oth er volcanic structures scattered over a wide area in remarkably similar to those airborne clouds. Coarse debris in formed on land. the same eruptive plume rains into During an explosive submarine the sea and settles on the flanks eruption in the shallow open ocean,of the cone, Pumice from the enormous piles of debris are built eruption floats on the water and up around the active volcanic vent. drifts with the ocean currents Ocean currents rework the debris over a large area. t7iztt-,- -fr-..re =

_ _

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Submanne etupbon of Mybon-abo %Pocono. Izu islands, Japan on September 23. 1952 a

Geysers, Fumaroles, andHot Springs

Geyse6, furnaroles (also called Erupting geysers provide spec sollataras), and hot springs are tacvlar displays of underground generally found in regions o: young energy suddenly unleashed, but volcanic activity. Surface water their mechanisms are not com- percolates downward through the pletely understoud. Large amounts rocks below the Earth's surface to of hot water are presumed to fill high-temperature regions sur- underground cavities. The water, rounding a magma resell/cif, eitherupon further heating, is violently active or recently solidified but ejected when a portion of it sud- still hot, There the water is heated, denly flashes into steam. This becomes less dense, and rises cycle can be repeated with re- back to the surface along fissures markable regularity, as for and cracks. Sometimes these example, at Old Faithful Geyser in features are called "dying vol- Yellowstone National Park, which f-anoes" because they seem to has erupted an an average of represent the last stage of volcanic about once every 65 minutes. activity as the magma, in depth, Fumaroles, which emit mixtures cools and hardens. of steam and other gases, are fed

- . . - ...-<- ..---. - -. ... .- 4= - - . .. wk. . , _- ..- ..a.-11.4,4,04tsiftm-44. , , N... :- """";--f_ AV...". 11--ollhe' `f...!. ...au.-r-- ia.._."---X71.--4.14':e. . .. ,,K. ..._-. .."74, -/4.':.90"- .. .tr '' r"'.2'ewifv07qr .4,4 so.7". 'N .""' 4 ; ",,::::..4....7.-*4%.-4...)"*. 4'4. ... '."IV . "1.- ..7.-- Old Faithful Geyser, Yellowstone National Park Wyoming. by conduits that pass through the of the Earth intersects the pater water table before reaching the table. The temperature and rate of surface of the ground. Hydrogen discharge of hot springs depend sulfide (H2S), one of ttie\typical on (actors such as the rate at gases issuing from fumares, which water circulates through the readily oxidizes to sulphuric acid system of underground channei- and native sulfur. This accounts ways. the amount of heat supplied for the intense chemical activity at depth, and the extent of dilution and brightly colored rocks in many of tne heated water by cool ground thermal_areas. water near the surface. Hot springs occur in many thermal areas where the surface

Black Growler steam vents tlumaroles). Norris Basin. Yellow stone National Park. Wyoming.

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. . Mammoth tiot Springs. Yellowstone National-Park. Wyoming 34 31 Volcano Environments There are more than 500 active Alaska, Washington, Oregon. and volcanoeskthosethat have erupted California)although many mord at east once within recorded his- may be hidden under the seas. tory) in the world-50 of which are Most active volcanoes are strung in the United States (Hawaii, like beads along, or near, the

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lit, voicaria-=:------='_---..---5------1,==--_-____,..-_4.-.-- .:4-- C. --i--_---=------. 44_ Mt. F Up _.:4--___7_74.--.. _,-r. -..--_ 1. - bo---..,,.,:--;-,-1.----..E.--4_,....,----= --e.----_,..,::4Z--vr-y- .w ,-- -7 MY611n- she -,:-7:,-- ,.--,-..., - Are. ..,, --.- --.'---- Namr-:-_-- .L-,-'-='"- :_.--p: ,-;,.:., a

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margins of the continents, and Italy's Vesuvius is the only active more than half encirclethePacific volcano on the European mainland. Oceanasa "Ring of Fire." Near the island of Vulcan°, the Many-volcanoes are in and volcano Stromboli has been in a around the Mediterranean Sea. Mount Etna in Sicily is the largest The distribution of some of:the Earth's and highest of these Mountains.. volcanoes.

60°

Mt. Katmai

Slashelairt Mt- Kiln% _ Mt. St. Helens Mt. Sheitif 40°

40° state of nearly continuous, mild the oceanic crust. Basaltic mag- eruption since early Roman times. mas, generated in theuppir At night, sailors in ithe Mediterra- mantle beneath the ridge, rise nean- -can see.the glow from the along fractures through the basaltic_ fiery. molten_ material that is hurledlayer. Because the granitic crustal into the air. Very appropriately, layer is absent, the magmas are Stromboilhas been called "the not appreciably modified or lighthouse of the Mediterranean." changed in composition and they --Some volcanoes crown island areaslying 'near the continents, -and Oth.ers_form chains of Islands in the.deep ocean basins. Vol- canoes tend to cluster -tong narrow mountainous belts where folding -and fracturing of the rocks provide channeiways to !he surface.. for the escape of megrim. Sig- nificantly, major earthquakes also occur along these belts, indicating that volcanism and seismic activity are often closely related, respond- . _ irig to the 'same dynamic Earth MountSinabung, Sumatra_ ply_ J. .13gykr forces, Roberts (C) Notterta6GepgriphiA_Sege.kk in a- typical "Island-ere envi7 ronment, volcanoes lie along the crest of an arcuate, crustal ridge bounded on its convex side by a deep oceanic trench. The granite .or granitelike layer of the continental crust .extends beneath the ridge to the vicinity of the trench. Basaltic magmas, generated in the mantle beneath the ridge, rise along fractures through the granitic layer, These magmas commonly will be moclifieck,or changed in composition during passage through the granitic layer and erupt on the surface to form volcanoes built largely of nonbasaltic rocks. In a typical "oceanic" environment, volcanoes are alined along the crest of a broad ridge that marks an active fracture system in IslancberO environment... erupt on the surface to form the mountain root, rise slowly or basaltic volcanoes. intermittently along fractures In In the typical "continental" the crust During passage through environment, volcanoes are to- the granitic layer, magmas are gated in unstable, mountainous commonly modified or changed In belts that have thick roots cif composition and erupt on The sur- granite._or.granitelike rock. Mag- face to form volcanoes constructed mks, generated near the base of of nonbasaltiP mdse.-

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57 Plate-Tectonics Theory According to the new, gefierally not associated with plate accepted "plate-tectonics" theoq, boundaries, and many of these scientists believtthat the Earth's so-called "intra-plate" volcanoes ' surface is broken into a number of form roughly Linear chains in the. shifting _slabs_ or plates, which interior of somefoceagio_plates. average about_ 50 miles in.thick- Thd flawaijan Islands provideper- -ness. These Plates move relative haps the,best example of an "Intra. to one another above a hotter, plate,voicanio chain, develpped Ileeper,_ more mobile zone at by the northwest-movirig,Paciflo ----aver4g-e-tWei as great as a few Plate -passing over,an inferred _ __inehes per Year. Most of the world's "hot spot" that initiates the _ activé viiicanoes are located along magma-generation a_n_d -volcano-- or near the boundaries between formation process. The peripheral shifting plates and are called. areas of the Pacific Ocera_p-Basin, e"plate-boundary" volcanoes. Flow- coritaining_the, boundaries-of. $ev- ever, some active volcanoes are era) plates, are dotted bymany

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ANT 201 . active volcanoes that form the so- sliding beneath another. The barbs called "Ring of Fire," The "Ring" on the lines indicate the overriding

providee excellent examples of_ plate, The Single line defines a "plate-boundary" volcanoes, in- strike-slip fault along which plates cluding Mount St, Helens. are sliding horizontally past one The accompanying. figure showsanother. The stippled areas indicate the boundaries of lithosphere a part of a continent, exclusive of ..plateathat,ere presently active.. that along .a. piste .bouncjaty,.which ,,The double lines indicate zones of is undergoing active ex_tensional, "spreading from Whl-ah plates are .compressional, or strike-slip -_moving- part. The tines with barbs _faulting. ioniCof_AinderthruSting (subduction), .where one plate_ is

Lithosphere plates of the Eart .

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-' 7- In the Pacific Northyrest. the Juan de :- . Fuca Plate plunges beneath the North GTIC PLATE American Plate, locally melting at depth: the'rnagma rises to feed and form the Cascade volcanoes. 2cf Extraterrestrial Volcanism Volcanoes and volcanism are products on the Moon, Mars. Venus not restricted to the planet Earth. and other planetary bodies.Many -Manned and unmanned. planetary. pounds of volcanic rocks were explorations, beginning in the late collected by astronauts during the 1960's, have furnished graphic various Apollo lunar landing misr4 evidence of past volcanism and i sions. Only a small fractionof

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Manner 9 imagery of OlympusMons Volcano on Mars compared to the eight principal Hawaiian Islands at the same scale(Mariner 9 image Mosaic, NASA/JPL).

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OAHU KAHOOLAWE HAWAII

4 these samples have been sub- of fluid lavas that have left numer- jected to exhaustive study by ous floOt features on their flanks scientists, The bulk of the material The most obvious difference be- Is stored under controlled- tween the two is size. The Martian environment conditions at NASA's shields are enormous. They can Lunar Receiving Laboratory in grow to over 17 miles in height Houston, Tex., for future study by and more than 350 miles across, in scientists. contrast to a maximum height of From the 1976-1979 Viking about 6 miles and width of 74 mission. scientists have been able miles for the Hawaiian shields,) to study the volcanoes on Mars Voyager-2 spacecraft image arid their studies are very reveal- taken of lo, a moon of Jupiter, ing when compared with those of captured volcanoes in the actual volcanoes on Earth. For example. process of eruption, The volcanic Martian and *Ha-waiirn volcanoes plumes shown on the image rise closely resemble each other in some 60 to lOo milesabove the form. Both are shield volcanoes. surface of the moon. Thus, active have gently sloping 41aha, large volcanisrii is taking place, at multiple collapse pits at their present, on at mast one planetary, centers,._and appear to be .built body in addition to our Earth,

_; - 1 - -

41-

Spacecraft ichige, made ".n-Jull 1979. shows volcanic plume risingSome 90 to 100 miles above the surface of lo a moon of Jupiter (loyoger 2 phOlo. NASA). Volcano Monitoring andResearch

It has been said that the science the city in A.D. 79. Still, through of "volcanology" originated with the first decade of the 20th cen- the accurate descriptions of the tury, the study of volcanoes oy eruption of Vestiviusin A.D. 79 aild large curitinued to be of an contained in two letters from Pliny expeditionary nature, generally the Younger to the Roman his- undertaken after the eruption had torian Tacitus. Pliny's letters also begun or the activity .had ceased. described the death of his uncle, Perhaps. "modeo-N" volcanology Pliny the Elder, who was killed in began in 1912, whb '''"omas A. the eruption. Actually. however, itftlaggar, Head of the Geology De- was not until the 19thcentury that partment of the Massachusetts serious scientific inquiry into vol- institute of Tectlaology, founded canic phenomena flourished as the Hawaiian Volcano Observatory part of the general revolution in (HVO), located on the rim of the physical and life sciences, in- Kilauea's caldera. Initially sup- cluding the new science of "geol-ported by an association of Hono ogy." In 1847, an observatorywas. lulu businessmen, HVO began to established on the flanks of conduct systematic and continuous Vesuvius r upslbpe from the site of_monitoring of seismic activity Hercula4eum, for the/Pore or less preceding, accompanying, and continuous recording of the activityfollowing eruptions, as wellas a of the volcano that destroyed the wide variety of other geological,

A,--1;4.4.A

.T.-1111 The U.S. Geolegical Survey'sHawaiian Volcano Observatory. op the'crater Alp of Kilauea Volcano. . . _ 40 4 geophysical, and geochemi of the volcano. Of cooe, he observations and investigati ns. "diary" keeping dun eruptive Between 1919 and 1948. HV was activity presents adtional tasks. administered by various Fe eras Wherever and whenever they can agencies (National Weather erv- do so safely, scipntists document, ice, U.S. Geological Survey and in words and orf film, the course of National Park Service), and ince the eruptiorin detail, make 1948 it has been operated c n- temperature measurements of lava tinuously by the Geologica Survey and gas,,collect the eruptive as part of its Volcano H ands product and gases for subsequent Program. The more the 60 years laboratory analysis, measure the of comprehensive invtigations by _heights of lava fountains or ash HVO and other sole Ws in Hawaii ply/nes, gage the flow rate of ash have added substa daily to our election or lava flows. and k,arry understanding of e eruptive out other necessary observations mechanisms of Kilauea and Mauna. and measuren ants to fully docu- Loa, two of theiivorld's most active ment and characterize the erup- volcanoes. Morlsover, the Hawaiian tion. For each eruption, such Volcano Observatory pioneesd documentation and data coliectron and refined most of the commonly and analysis provide another build- used volcano-monitoring tech- ing block ins constructing a model niques presently employed by other of the characteristic behavior Of a observatories monitoring active given volcano or type of eruption. volcanoes elsewhere, principally in Volcano monitoring also involves Italy. Japan, New Zealand, Lesser the recording and analysis of vol- Antilles (Caribbean), Philippines. canic phenomena not visible to the and Kamchatka (U.S.S.R.). human eye, but measurable by What does "volcano monitoring" precise and sophisticated instru- actually involve? Basically, it is ments. These phenomena tnciude the keeping of a detailed "diary' ground movements, earthquakes ;- of the changesvisible end in- (particularly those too small to be visiblein a volcano and its felt by people), variations itrgas surroundings. Betweeneruptions. compositions, and deviations in visible changes of importance to local electrical and magnetic the scientists would include. markedfields that respond to pressure and increase or decrease of steaming stresses caused by the subter- from known vents, emergence of ranean magma movements. new steaming areas, development Some common methods used to of new ground cracks or widening study invisible, volcano-related of pld ones, unusual or inexplicable phenomena are based tsins withering of plant life, changes in 1, Measurement of changes in the color of mineral' deposits the 'shape of the volcano --vol- encrusting fumaroles, and any canoes gradually swan or "inflate other directly obseritable, and in building up to an "eruption often measurable, feature that because of the influx of magma might reflect a change in the state into the volcano's reservoir or

41 1

plumbing system", with the onset By carefully mapping out the vari- ,of eruption, pressure is immedi- ations with time in the locations ately relieved arid the volcano and depths of earthquake foci, rapidly shrinks or "deflates.- A scientists in effect can track the wide variety of instruments, includ- subsurface movement of magma, ing precise spirit-levels, electronic horizontally and vertically. liltrneters," and electronic-laser 3. Measurement of changes in beam instruments, can measure volcanic-gas composition and in changes in the slope ortilt" of the magnetic fieldthe rise of magma volcano or in vertical and hori- high into the volcanic edifice may zontal distances with a precision allow some of the associated gases of only a few parts in a million. to 9scape along fractures, thereby 2 Precise determinptiort of the causing the, comppsltion of the location and magnitude of earth- gases (measured at the surface) , quakesby a well-designed seismic to differ from that usually measured networkas the volcano inflates when the volcano is quiescent and by the rise of magma, the enclosing and the magma is too deep to allow rocks are deformed to the breaking. gas escape. Changes in the point to accommodate magma earth's magnetic field have been movement. When the rock ulti- noted preceding and accompany- mately fails to permit continued ing some eruptions, and such magma ascent, earthquakes result. changes are believed to reflect

USGS volcanologiat uses a Correlation spectrometer (COSPEC) to measure the sulfur dioxide content of gases elected during the Mount St. Helens eruption. .1

fn.

I i

42. temperature effects and or the the past 4.500 years and the one content of- magnetic minerals in most like.v to reawaken to erupt, the magma. "... perhaps before the end of this tecording historic eruptions andcentury." Their prediction came modern v.,icano-monitoring in true when Mount St. Helens themselves are insufficient to fully rumbled back to life in March of determine the characteristic be- 1980. As of this writing (June havior of a volcano, because a time1981), the Mount St. Helens erup- record of such information, though tive activity continues and is perhaps tong in human terms, is characterized by periodic explo-, much too short in geologic terms sive ejection of ash and steam to permit the making of reliable and/or the formation of lava predictions of possible future be- domes within the crater. Each ex- havior. An integral part of a corn- plosive event may partly or wholly prehenskve investigation of any destroy the previously formed volcano musts also include the dome. i ft careful, systematic mapping of the By analogy to its past history, nature, volumes, and distribution Mount St. Helens can be expected of the products of prehistoric to remain intermittently active for eruptions, as well as the deter- Years. possibly even decades, In mination of their ages by modern 1980 the Geological Survey estab- isotopic and other dating method§.lished a facility in Vancouver, --,tResearch on the volcano's geo; Wash., to facilitate the increased logic past extends the data base monitoring and research on not for refined estimates of the recur- only Mount St. Helens, bUt also the rence intervals of active versus other volcanoes of the ,Cascade dormant periods in the history of Range, In many ways, the Van - the volcano. With such informationever facility can be considered in hand, scientists can construct -$ a sister observatory to the so-called -volcanic hazards.' maps Hawaiian Volcano Observatory. that delineaie the zones of greatest,The research being undertaken at risk around the volcano and that both observatories can' be ex- designate vLithich zones are particu- pected to provide important com- larly susceptible to certain types parisons and contrasts between the of volcanio hazards (lava flows, behavior of the generally non- ash fall, toxic gases, mudflows and explosive Hawaiian shield volca- associated flooding, etc.). noes, Kilauea and Mauna, Loa, and A strikingly successful example that of the generally explosive of volcano research and volcanic- composite Cascade volcanoes, hazard assessment was the 1978 such as Mount St. Helens, Antici- publication (Bulletin 1383-C) by pated comparative data on which two Geological Survey scientists, monitoring techniques might prove Dwight Crandell and Donal Mulli- to be most reliable and diagriostic neaux, who concluded that on which type of volcano should Mount 1St. Helens was the. Cascade materially enhance our capability volcano most frequently active in to forecast volcanic eruptions. I, Volcanoes and People

Volcanoes both harass and help The role of the scientists in- mankind. As dramatically and volved with volcano research is tragically demonstrated by the clear. They must continue to im- catastrophic eruption of Mount St. prove the capability for predicting Helens on it ay 18, 1980, volcanoeseruptions on a longer term as well can wreak lavoc and devastation as on an immediate-term basis. in the shor term. However, over They must provide the policy- the tong tt-krn and geologic time, makers and the general public with volcanic eruptions and related the best possible maps of volcanic processes have directly and in- hazards ant# assessment important . air-,:tly benefited mankind; Vol- for sound decisions on land-use canic materials ultimately break planning. down and weather to form some Scientists still do not fully under- of the most fertile soils on Earth. stand many of the processes at cultivation of which hae produced work inside the Earth and how Abundant food and fostered , these P:ocesses relate to volcan- civilizations. People use volcanic ism. What is the ultimate driving products as building or road - force for platetectonic move- ..building materials, as abrasive and meat? How and why does magma cleaning agents, an'd'as raw originate? How do the magma .materials for many chemical and blobs combine to be transpoped industrial uses. The internal heat to the surface? What are the associated with yOung volcanic specific mechanisms for the for- systems has been harnessed to mation of the different composi- produce geothermal energy. For tions of magmas, which in turn example, the electrical energy form different lypes of volcanoes? generated from The Geysers geo- Geologists and other geoscienbsts thermal field in northern California are striving to better answer these can meet the present power con- and other basic questions, because sumption of the city of San they know that volcanoes and Francisco. volcanic phenomena provide clues to the Earth's past, present, and possibly to its future. References

Although reference works on the Tilling. R. I.. 1977. Monitoring active topic of volcanoes abound, this highly volcanoes. tri U.S. Geological Survey abbreviated and generalized adcount Yearbook. Fiscal Year 1977, p. 35- drawi principally from the following 40. publications: U.S. Geological Survey. 1972. Th'e Macdonald, G A. 1972. Volcanoes. atlas of voicaniciphenomena to set Prentice Hall. tnc . Englewood Cliffs. of 20 information sheets illustrating. New Jersey. 310 p. various volcanic phenomena). 47 44) * GewstunazwrpeehTheorn 2401 - 361418 133/13s -amilese

Tho P" _ city of SL Pierre on the island of Martinique:Mount Pete° Is in the In(ground.

45 45 --,f-es-,- -4 ...... t.- . .... 4 Zeer'''71471 -°.r.A -.,.--:_r-l '- -..-:__*:-- .-4.- -v----,- - E .- ' -...r -,,-, -'- ..- ....;t..-' -. '. r---,------t -- - ' -. - ,- ',.^T., -,i'...-- -Oas: , ..-.. _ --.-... --w - f - - ',.....,:ie ..-- `----'- ' , li.' '-.- ' A: _4- -'-'-.. . ' .." ' -,'r-- ; i --_.";-.:-,,L?_ :'t' r "; . . .

_ Asthe Nation's principal Conservation agency, the Department of the = Anterior has responsibility for most or our nationally ownetpublio lands and naturat resdurces. This reclides fostarriiiithryirseatlie Or our land and water resources, protecting our fish. and Wildlife,- preserving the environmental and cultural values of our national parks and histortcal placea-and providing for the enjoyment el lite through outdoor recreation. The Department assesses our energy an mineral resources and works to assure that their development is in the best interests csf, all our people. The Department also has a major responsibility for American Indian reservation communities and for people who live in Island Territories under U.S. administration.

. _

This publication is one of a series of general interest publications prepared by the U S Geological Survey to provide information about the earth sciences, natural resources, and the envirOnment. To obtain a catalog af additional titles in the series "Popular Publications of 1, the U.S.Geotogical Survey," write: Branch of Distribution or Branch of Distribution

1- US Geological Survey U.S. Geological Survey 604 South Pickett Street Box 26286, Federal Center Alexandria, VA 22304 Denver, CO 80225