SMITHSONIAN" WARNING: THIS SET CONTAINS BAKING SODA(SODIUM BICARBONATE) THAT MAY BE HARMFUL IF MISUSED. READ CAUTIONS CAREFULLY. NOTTO BE USEDBY CHILDREN EXCEPT UNDER ADULT SUPERVISION. WARNING! ONLY FOR USE BY CHILDREN OVER 8 YEARS OLD. CONTAINS CHEMICALS. READ THE INSTRUCTIONSBEFOREUSE, FOLLOWTHEM AND KEEP THEM FOR REFERENCE. DO NOT ALLOW CHEMICALS TO COMEINTO CONTACTWITH ANY PART OF THE BODY, PARTICULARLYTHE MOUTHAND EYES. KEEP SMALL CHILREN AND ANIMALS AWAY FROM EXPERIMENTS. STORE THE SET OUT OF REACH OF SMALL CHILDREN. EYE PROTECTIONFOR THE SUPERVISINGADULT IS NOT PROVIDED. PLEASEKEEPA NOTEOF OURNAME ANDADDRESS DETAILS FORFUTURE REFERENCE. IN EUROPE CONTACT: NSI SIMMGAmbH C~ D76162KARLSRUHE GERMANY 49-o721-9584-116 PLEASEBE SURETO READTHE ADVISE FOR SUPERVISINGADULTS AND THE SAFETY RULES CONTAINED IN THIS BOOKLET. ~2002SMITHSONIAN" INSTITUTION NATURAL SCIENCE INDUSTRIES. LTD. 910ORLANDO AVE. WEST HEMPSTEAD. N.Y. 11552 PRINTEDIN USA ITEMNC,. 3269-08 YOURSET CONTAINS THEFOLLOWING ITEMS: 3 VOLCANIC ROCKS ~ # Measuring cup Note: 1ram, equals lcc. VOLCANO SUBSTRUCTURE SODIUM HYDROGEN CARBONATE(BAKINGSODA) BAG SAND MIX ERUPTIONBOTTLE FORVINEGAR SAFETY GOGGLES ~STIC TUBING CAUTION: THE VOLCANICROCKOBSIDIAN MAYHAVE SHARPEDGES. USE CAUTIONWHENHANDLING. GENERAL FIRST AID INFORMATION: IN CASE OF EYE CONTACT:WASHOUT WITH PLENTYOF WATER,HOLDINGEYE OPENIF NECESSARY. SEEK IMMEDIATE MEDICAL ADVICE. IF SWALLOWED: WASHOUT MOUTHWITH PLENTY OF WATER,DRINK SOMEFRESHWATER.DO NOTINDUCE VOMITING. SEEK IMMEDIATEMEDICALADVICE. IN CASEOF INHALATION: REMOVE PERSONTO FRESHAIR. IN CASEOF CONTACT AND BURNS: WASHAFFECTEDAREA WITH PLENTY OF WATERFOR 5 MINUTES. IN CASE OF INJURY OR IF IN DOUBT,SEEK MEDICALADVICE WITHOUTDELAY. TAKE THE CHEMICALWITH THE CONTAINERWITH YOU. ADVICEFOR SUPERVISINGADULTS: ¯ READAND FOLLOWTHESESAFETYINSTRUCTIONS,THE SAFETYRULESAND THE FIRST AID INFORMATIONAND KEEP THEM FOR REFERENCE.¯ THE INCORRECTUSE OF CHEMICALSCAN CAUSEINJURY AND DAMAGETO HEALTH. ONLY CARRYOUT THOSEEXPERIMENTSWHICH ARE LISTED IN THE INSTRUCTIONS.THIS SET IS FOR USE BY CHILDRENOVER8 YEARSOF AGE. ¯ BECAUSECHILDREN’S ABILITIES VARY SO MUCH, EVEN WITHIN AGE GROUPS,SUPERVISING ADULTSSHOULDEXERCISEDISCRETIONAS TO WHICHEXPERIMENTSARE SUITABLE AND SAFE FOR THEM. THE INSTRUCTIONSSHOULDENABLE SUPERVISORSTO ASSESSANY EXPERIMENT TO ESTABLISHITS SUITABILITY FOR A PARTICULARCHILD. THE SUPERVISINGADULTSHOULD DISCUSS THE WARNINGSAND SAFETY INFORMATIONWITH THE CHILD OR CHILDRENBEFORE COMMENCING THE EXPERIMENTS. PARTICULAR ATTENTION SHOULDBE PAID TO THE SAFE HANDLINGOF ACIDS. ¯ THE AREA SURROUNDING THE ACTIVITY SHOULDBE KEPT CLEAR OF ANY OBSTRUCTIONS AND AWAYFROMSTORAGEOF FOOD. IT SHOULDBE WELL LIT AND VENTILATED ANDCLOSETO A WATERSUPPLY. SAFETYRULES: ¯ DO READ THESE INSTRUCTIONSBEFOREUSE, FOLLOWTHEM AND KEEP THEM FOR REFERENCE. ¯ DO KEEP YOUNGCHILDRENAND ANIMALS AWAYFROMTHE EXPERIMENTALAREA. ¯ DO STORECHEMICALSETS OUT OF REACHOF YOUNGCHILDREN. ¯ DO CLEANALL EQUIPMENTAND WASHHANDSAFTER CARRYINGOUT THE EXPERIMENTS. ¯ DO NOTEAT, DRINKOR SMOKE IN THE ACTIVITY AREA. ¯ DO NOT USE EQUIPMENTWHICH HAS NOT BEEN SUPPLIED OR RECOMMENDED IN THE SET. ¯ DO NOT ALLOWCHEMICALSTO COMEINTO CONTACTWITH THE EYES OR MOUTH. ¯ DO NOT REPLACEVINEGAROR BAKINGSODAIN ORIGINAL CONTAINER.DISPOSEOF IMMEDIATELY. ¯ DO ALWAYSWEAREYE PROTECTION. GIANT VOLCANO¯ Item #3269 PART ONE: INTRODUCTION Volcanoesandtheir eruptions are amongthe most inspiring andawesome expres: ions of the natural world. Volcanicactivity has shapedthe history of the earth andmanyother planets andmoonsin our Solar System.Whydo volcanic eruptions oocur on so manydifferent worlds? They~11 happenfor the samereason.Theseworldsare trying to cool off. Theyare hot inside andlosing that ,nner heat to cold outer space. Volcanic eruptions, whichspewhot lava on the surface or blast hot pure ce, ash, andgas into the air, are very goodwaysto lose someof that inner heat. In this manualyou will learn importantfacts aboutEarth’s active andancientvolcanoes,andthe people whostudy them(volcanologists). It also contains suggestionson locating other information on volcanoes. such as maps,videos, booksthat you can borrow from the library, computerf:rograms you can download for free from the Intemet, andvolcanosites on the WorldWideWeb,whichwill give you informationon the latest activity at Earth’svolcanoes. Editorial Note: Importantnewwordsare underlinedthe first time they are introduced. Definitions of newwordsare in the Glossaryor in the text. SECTION ONE Building and Erupting Your Volcano What you are about to do -- build a model-- is a glorious undertaking,andoneof the main ways that scientists and engineers learn about howthings work. Modelsare not the same as the things they represent,andit is importantto understand the differences. In the caseof the volcano modelrememberthat: (1) Compared to real volcanoes,the modelis too small, steep, andcold. Usea protractor to measurethe slopeangleof yourvolcanoafter it is built. Youwill probably find that it is slightly steeperthan the slope angles of real volcanoesmentionedin this booklet. (2) Real volcanoes grow over time: eruption eruption, layer by layer. Theycan take a few years to a few million years to develop.Youwill assemble your modelin about ten minutes. The process ot adding the sand mixture to the plastic frameworkis a formof artistic sculpture,but nothinglike the growthof a real volcano. After you havebuilt your volcano, it will take abouttwentyminutesto dry. (3) Real volcanoes have undergroundpipes that bdng_magma (hot moltenrock) to the surface. erupt your modelVolcanoyou will first place baking sodainto the center crater andthen adda mixture of vinegarandfood coloring. All of thesematerials arecold. (4) After real volcaniceruptions,newlava or a_.s.hh has addeda newsolid layer on the surface of the volcano. In your model,the magma is a mixture of vinegar, food coloring, and bakingsoda. It never becomes solid, and doesnot addto the volumeof the volcano. Youcan dnse your volcanooff in the sink andmakeanother eruption. NOTE: Building anderupting yc ur volcanocan be a messyendeavorif you are not careful. To be on the safe side, prepare anderupt your volcano in the kitchen or a part of the he.usethat doesnot havecarpeting and/or fine furniture. Don’t wear goodclothes. Wearan aprono" smockif you have one. Always wear your protective goggles when erupting your volcano. BUILDING YOURVOLCANO DIRECTIONS (1) Connectthe tube to the w)lcanosubstructure. Dothis by turning the plastic substructureon its side andinserting the 2-foot-long tube fromunderneath into the center hole to ,~ depth of about 13 millimeters(1/2’). Snakethe Jest of the tubing out through the side of the subst’ucture. Fasten the tube into the notchedtrack on the din, as shownin figure B. figure A (2) To prepare the volcano-making compound, you will needa large clean disposablebucket. Cut the bagof sandmix at one of the corners.Pourthe mix into the bucket. Next, add9 ouncesor 266CC of warmtap waterto the bucket,asshownin figure C. After you add the water, mix the sandandwater for about 5 minutes or until all of the sand has mixedwell with the water, as shownin figure D. (3) Scoopout the compound with your handsand apply it to the volcanosubstructure, as shownin figure B. Apply all of the compound to completely cover the entire volcano substructure (except for the moatthat surroundsthe baseof the volcano.) As you apply the compound,makea mental note aboutthe position of the notchesin the plastic substructure’s rim. The compound mayseema little wateryat first, but within 5 minutesit will beginto harden,makingit easier to mold.It is importantto form a center crater for use later in the eruption stage. To formthe top part of the volcano,use your finger to apply the compound into the upper rim. Packthe compound downin the center forming a wall aroundthe center. After the rim is formed, maketwo notchesin the rim to correspondwith the notches on the plastic substructure. Be sure to affix the tube backin place if it wasdisturbedwhen forming the upper rim. Thecompound will take approximately20 minutesto hardenif it is mixedcorrectly. (4) After your volcano hardens, you maywant paint it using non-water-basedpaints. Consider using white to representsnowandice near the top (see figures #6c and #6d). Greenpaint on the lower s’,opes can representtrees. After the paint dries, you can erupt your volcano as manytimes as you wish. figure C figure D ERUPTING YOUR VOLCANO DIRECTIONS (1) Place newspapergenerously into the bottom of the box from your volcanokit. Placethe volcano with the hardenedcompound on top of the newspaperin the box, as shownin figure E. Snakethe tubing out over the side of the box. (2) Put your safety goggles on. Preparethe vinegar bottle’s pointy capby snippingat the line with scissors, as shownin figure F. Besure to point the bottle downand awayfrom eyes whensnipping. NOTCHES figure figure E (3) Fill the bottle with household vinegar (either red or white will work)as shown in figure G. First, measureout 90 ml (3 ounces)of vinegar and pour into the bottle. Securethe pointy cap on the bottle. Adda few dropsof liquid soapinto the cavity with the vinegarandgently stir the two. This will thicken the vinegar and provide for a thick and foamy eruption. If you want to give the "lava" color, add several drops of food coloring to the vinegar. ,~ mixture of three dropsof red andthree dropsof yellowcomes closestin color to real glowing lava, but have fun and try someother color mixtures. Next, add one tablespoon of baking sodato the center crater of the volcanoas shown in figure H. Your eruption time dependso~1 how often you squeezethe bottle. Onceall o the vinegar has mixed with the baking soda, you can empty the "lava’ in the sink andrepeatthe ~ ruption againand again (always remember to wea" your safety goggles). I .,.,...~_~, ’ figure fJgure H figure F (4) Fasten the free end of the tube onto the pointy cap of the bottle. Thetube shouldsit firmly over the endof the pointy cap. (5) Beforeerupting, checkboth endsof the tube. Oneend should be exposedin the crater of the volcano, and the other endshould be fastened to the pointy capof the vinegarbottle. (6) Your volcano is now ready to erupt! Gently squeezethe vinegar bottle to force the vinegar up throughthe tube whereit will mix with the baking sodain the crater. Oncethis occurs, the mixture will flow out of the crater of the volcano,spilling through the notchesandout over the sides. figure G -- SECTION TWO What is a Volcano and Whereon Earth are They? Volcanoesand Plate Tectonics Earth’s volcanoes are places where molten rock, or magma,erupts on the surface. At most volcanoesthe erupted lava, pumice,or ash, piles up to build a hill or mountain.Manyyoung,active volcanoeshave the smoothand even majestic profiles that wehavecometo associatewith this word (see Figure #1). Older volcanoes maybe both erodedand coveredwith vegetation, hiding their true nature. Becausethey are not easily recognized as volcanoes,these can be especially dangerous whenthey awakenand erupt. Whenmagma reaches Earth’s surface it can erupt in two basic ways:explosively or non-explosively. Magma that is rich in gasesblasts apart to form fragmentsof different sizes, such as pumice and ash. Magma that is poor in gaseserupts nonexplosively to flow along the groundas lava. If magma cools rapidly, the liquid portion transforms to naturalg!a,~s. Most of the volcanoes discussed here abovesea level, on continents, or islands. These volcanoes, though, only account for about onefourth of the magma that reachesthe surface of the earth. Theremainingthree-fourths erupts on the sea floor, mostly along a world-wide systemof mountain ranges called spreadingridge.s. (see Figure #2). Here, Earth’s tectonic plates are formed. We knowrelatively little about theseeruptions, which typically occur about 11/2 kilometers (.93 mi~es) belowsealevel. At Iceland, a spreadingridge rises abovesealevel, allowing volcanologi~ststo observe these eruptions moreclosely. The world map(see Figure# 3~ showsEarth’s 1,500 volcanoesthat are knownto haveerupted in the last 10,000 years. Thesedata are from the Global Volcanism Program of the Smithsonian Institution, wherescientists keeptrack of Earth’s active volcanoes.Notice that the active volcanoes mostly lie in belts that border the Pacific Ocean. Thesevolcanoesoverlie subductiqq, zones, places whereone of Earth’s tectonic plates dives beneath another and descends into the hot mantle (see Figure#2). As the plate descends,it heatsup. This drives off sea water that wasaddedto the oceanic crust shortly after it formedat a spreadingridge. This hot watery fluid rises into the solid rock of earth’s mantleabovethe subductingplate. Thereit causesthe mantlerock to begin melting. EXPLANATION BOX The process that generates magmasin subduction zones is very similar to what happens whensalt is sprinkled on an icy sidewalk in the winter. Thewater that rises into the hot mantlerock, andthe salt added to the sidewalk ice, both lower the melting temperatures of these materials below the actual temperature, causing them to melt. A third importantenvironment for active volcanoes is aboveEarth’s hot spots (see Figure #2). These are columns of unusually hot rock that extend for manyhundredsof kilometers into the earth’s mantle, perhapsevet~ to the boundarywith the core at a depth of 2,885 kilometers (1.79 miles). Thesehot columnsof rock moveonly very slowly in relation to oneanother.Overtime, as the tectonic plates moveacross Earth’s surface at muchfaster rates, the hot spots repeatedly send batches of _m_agma upward to build volcanoes. Oneafter another, volcanoesgrow andare carried awayfrom the hot spot by the movingplate. In this way, a linear chain of volcanoesforms, with the volcanoagesincreasing steadily in the direction the plate is moving. Mayon Strato Volcanoin the Philippines is famous for its beautifully symmetricalconeshape.Although this is the classical conception of a volcano, in this bookletyouwill seethat volcanoes actually comein a widevariety of shapesandsizes. Photo by Kurt Fredriksson (Smithsonian Institution). Figure #1 EXPLANATIONBOX Mag.mais the namefor molten rock underground.Magma consists of two or three parts: (1) the liquid portion in whichgasesare dissolved,(2) suspended crystals of variousminerals, andin somecases(3) suspended gas bubbles. 4 Schematic moss-section illustrating plate-tectonic processes. Threetypesof plate bouncaries are shown:1 ) divergent (movingapart) boundariesat oceanicspreadingridges, wherethree-fourths of Earth’s magma erupts virtually unnoticedby humans; 2) convergent(movingtowardoneanother)boundariesat subduction zones.Thetrench marksthe place whereoneplate beginsto descend beneathanother..’~’trato volcanoes are common abovesubductionzones;3) transform(movingpast oneanother)boundariesthat join spreading-ridge segments: only minorvolcanic eruptionsoccurin this environment. Alsoshownis anoceanichot spot with its overlyingchain of shield volcanoes,anda youngcontinentalrift zone,perhapsevolvingto become an oceanic spreading ridge. Thelithosphereincludesthe crust (oceanicor continental)andthe rigid part of the under° lying mantle.Belowthe lithosphereis the asthenosphere, a region wherethe solid rock of the mantleflows. Thisflowageallowsmotionof the overlyingplatesto takeplace. Figure #2 The HawaiianIslands have tile best-known examplesof hot-spot volcanoes.Theactive volcanoes MaunaLoaand Kilauea lie at the southeastern tip of a 6,000 kilometer (3726mile) long chain of island and submarinevolcanoesthat has grown abovea stationary hot spot for morethan 70 million years. The newestHawaiianvolcano, called Loihi, is already growingup from the sea floor. Of course, it is southeastof Kilauea and Mauna Loa. Its top is nowabout one kilometer belowsea level. EXPLANATION BOX Units: In this section weuse metric units of length. Equivalent English units are given below. Metric System 1 millimeter (mm) 1 centimeter (cm) 1 kilometer (km) English System 0.039 inches 0.394 inches 0.621 miles Worldmapshowinglocations for 1,500volcanoesthat haveeruptedduring the last 10,000years. Datafrom the Smithson~an’s Global VolcanismProgram. Figure #3 SECTION THREE Who Studies Volcanoes and Why? The scientists whostudy volcanoesare called volcanologists. Theusual road to becominga volcanologist is to study geologyat a college or univeraity, and then to attend graduate school to receive additional training andto beginconducting researchworkfor a Master’s or Ph.D. degree. Volcanologistsare principally employed at colleges or universities, and by governmentorganizations, including official volcano observatories pl~cadnear important active volcanoesin various parts of the world. The U.S. Geological Survey runs three volcano observatories located in Hawaii, the Cascades, and Alaska. If you enjoy nature, hiking, and camping,and are goodat math and science, you, too, mayoneday becomea volcanologist. In addition to this geologicalroad to becoming a volcanologist, each passing year sees moreand moreimportantcontributions to the study of volcanoes being madeby scientists trained in other fields. Major advancesin monitoring volcanic activity have been madeby 9eot)hysi~ists who study earthquakes and precise changesin the shape of the land surface that can precede and accompanyeruptions, Chemists and physicists have developedinstruments for analyzing volcanic rocks and minerals and for re-creating miniature magma bodies in laboratory furnaces at high temperaturesand pressures. Chemistsand physicists also design instrumentsthat are placedon satellites in orbit around the earth andcan track cloudsof volcanic ash and gas as winds carry them around the planet (see Figure #4). Whystudy volcanoes? On a personal level, manyvolcanologists wouldanswerthat the work is fun, fascinating, andallows themto hike aroundin beautiful settings doingthe workthey love, as well as getting paid for it! Ona morepractical level, societies needto understandthe past behavior of potentially active volcanoesas the best meansof anticipatingthe effects of future eruptions.LM.onitor~ of these active volcanoes using a variety of instrumentsis also essential for providing timely warningfor evacuationsof peoplefrom threatened areas. Andyou don’t have to live near an active volcano to be threatened by it! Manyvolcanic eruptions send denseclouds of gas and ash particles into the air, wherethey drift with the windfor hundredsand even thousandsof kilometers. Whenairplanes fly into these clouds they can be damaged in a vedety of ways,most seriously when their enginesingest ash andfail. Sinoe1980mote than eighty commercial aircraft haveflown into volcanic ashclouds. Fortunately, all wereable to land safely. Still, they hadextensive damage,ranging from scratched windowsto ruined engines. Repair bills have exceededtwo hundredmillion dollars. Onthe positive side, volcanoesprove;deheat that can be tapped to produce elec:ricity (~ energy). Volcanoesalso help b) form mineral Satellite imageof the spreadingeruption cloud fromthe Philippine volcanoMountPinatuboas it looked4 hoursand45minutesfollowingthe start of the majorexplosiveeruptionon June15, 1991. Thevolcanois labeled andb/ack lines showthe coast of Luzonandother islands. Theimagewas take~by a weathersatellite operatedby the National OceanicandAtmosphericAdministration (NOAA).Courtesyof GeorgeStephens(NOAA). posits that modernsocieties need. For these and other reasons,the world noed:~voloanoiogists to pay careful attention to active vol~.oes. Figure #4 SECTION FOUR Different Kinds of VolcanoesControlled by the Three V’s of Magma:Volume,Volatiles, and Viscosity Volcanoescan be found in a wide range of shapesand sizes. Whatcontrols the type of vofcenothat develops?In large part the volcanotype is controlled by three things: the volumeof magma erupted, the amountof volatiles or gasesit contains, andits viscosi~. Thelargest explosiveeruptio,~ in recordedhistory, at the IndonesianvolcanoTambora in 1815, ejected =J:K)Ut 150 km3 (35.8 miles3) of pumiceand ash. Somehugeexplosive eruptions preservedin the geological record, including ones from Yellowstone Park, ejected morethan a thousand VOLUME: In the kitchen we measurevolumes in units of teaspoons,tablespoons,andcups. At the gasstation weuse units of liters or gallons. In a similar way, volcanologists measureerupted volumeswith an appropriate(andreally big) unit, the cubic kilometer (km3) or (.239 cubic miles). Imagine an enormouscubethat is onekilometer (.621 miles) long on eachof its edges:that is a cubic kilometer (1 km3) (.239 cubic miles). Volcanic eruptions range widely in size (see Figure cubic kilometers (239 miles 3) of pumiceandash. Thevolumeof magma invo/ved in an eruption, the eruption style, and the frequencyof eruptions are !mportantcontrols on volcanotype. #5). Small ones eject lava or oumiceand ash with a volumethat is just a smallpart of a cubic kilometer. Thelargest lava eruption in recordedhistory, at the Icelandic volcanoLaki in 1783, produced15 km3 (3.58 miles3) of lava. VOLATILES:The amount of volatiles or gases present in the magma controls howexplosive the eruption will be. Common gases in magmasare water, carbondioxide, suffur dioxide, andhydrogen sulfide. Whenthe magma ~s deep in Earth’s mantie or crust, the tremendous pressureof the over. lying rocks allows these gases to be dissofved within the liquid portion cf the magma.As the magma nears Earth’s surface beneath a volcano, the pressureis dramatically loweredand the gases canno longerbe held by t’~e liquid. YELLOWSTONEISLAND PARK /1~,~,~,,~ / 20Ma EXPLANATION BOX Eachtime you hold a sodabottle in your hands you hold a wonderfulmodelof an explosive volcano that can teach you about the role of volatiles in magmas.All carbonated drinks contain carbon-dioxide(CO2)gas. This gas injected into the soda under high pressure at the bottling plant andgivesthe sodaits fizz. To simulate an explosive eruption: ~ ~ First ~ ~ VOLUMES OF ERUPTIVEMATERIAL Rectangularcubesare scaledto showthe volumes of pumiceandash ejectedin progressivelylarger eruptions.. The three largest events showntook )lace at Yellowstone NationalParkduringthe last two million years. [(From: The Yellowstone Hotspot(1994) by Robert B. Smith andLawrence W.Braile, Journal of VolcanologyandGeothermal Research)] Reprinted frmmthe Journal of Volcanology and Geotherrna/Research, v. 61byRohert B. Smith andLawrence W B~le, The Yellowstone Hotspot, p. 121-187, (1994), withkindpermission ofElsevier Science-NL, Sara Burgerhartstraat 25,1055 KV Amsterdam, TheNetherlands. Shakethe bottle. This helps gas bubbles to form. Second Remove the cap. The carbon dioxide can no longer be held in the soda under the new low pressure. In response, the soda foams and shoots out of the bottle. Thesamething happens when gas-rich magma"feels" the low pressure of Earth’s atmosphere and foams beneath a volcano. It ultimately erupts as an explosive mixture of pumice, ash, and hot expanding gases. starts as seawaterthat is carried into Earth’s mantle by the subducted plate. After the plate descendsmorethan fifty kilometers (31.05 miles) into the earth, the seawaterrises fromit to invade the overlying mantle. This invasion of water causes the mantleto begin melting, andthe watergets caught up in the magmas formedby this melting. In contrast, the magmas erupted along spreading ridges and at hot-spot volcanoes are generally muchpoorer in gases, and these erupt muc.hless explosively. Their eruptions typically form lava instead of pumiceand ash. Figure #5 instead they form countlesstiny bubblesthat grow larger and larger as the magmabecomesa moltenfoam. As it erupts, this foambreaksapart into pumiceand ash particles andthe rapidly expandinggasesthat explosively drive themout of the volcanic crater. This is the sameprocessthat you will modeleachtime you erupt your volcano. Themagmas formedin different tectonic settings differ in their gas contents and eruptive styles. Magmas erupted in subduction zonesare the most gas-rich, and subduction-zone volcanoes have beenthe sites of Earth’s mostexplosive and deadlyeruptionsduring historical times (see Table 1 on the following page). The main gas in subduction-zone magmas is water, or more properly steam. This water VISCOSITY:Magmasrange widely in chemical composition,temperature,amountof crystals, and percentageof gas bubbles. All of these factors affect how easily the magma can flow. Volcanologistsuse the term viscosity to describe howrigid a magma is. Silicon dioxide (SiO2), silica, is the most abundantchemical component in magmas. It also hasthe strongestinfluence on viscosity. Magmas that are dch in silica are the mostviscous: they are very rigid and do not flow easily. Crystals andgas bubblesalso increasethe viscosity. Temperaturehas the opposite effect. As it increases,viscosity decreases. 8 TABLE1 Largest Explosive Eruptions of the 19th and 20th Centuries Year Volcano Location 1991 1991 1982 1980 1956 1932 1912 1907 1902 1886 1883 1875 1854 1835 1822 1815 Cerro Hudson Pinatubo El Cnich(Sn MountSt. Helens Bezymianny Cerro Azul/Quizapu Novarupta/Katmai Ksudach Santa Maria Tarawera Krakatau Askja Sheveluch Coseguina Galunggung Tambora Chile Phdippines Mexico Washington, U.S. Kamchatka, Russia Chile Alaska, U.S. Kamchatka, Russia Guatemala New Zealand Indonesia Iceland Kamchatka, Russia Nicaragua Indonesia Indonesia First Historical Eruption? Deaths no yes yes no yes no yes yes yes yes no yes yes yes yes yes 0 800 2,000 57 0 0 2 0 >5,000 > 150 36,417 0 0 5-10 4,011 92,000 All thesevolcanoes,exceptAskja, are locatedabovesubductionzones.All theseeruptior.s produced pyroclastic deposits withvolumes of at least 1 cubickilometer(.239cubicmiles).All but four w~.,rethe first historical eruptionknown fromthe volcano,andthe highdeathtolls (in heavilypopulated regions)reflect this fact. Reprintedfrom Volcanoes of the Wodd (SimkinandSiebert, 1994.) Lavas of unusual silica-poor composition [40%by weight SiO2)erupted from the Afdcanvolcano Nyiragongocan have extremely low viscosities. Theycan flow downslopeas fast as highway traffic 100 kilometers/hour (62 miles/hour) and drain awayfrom the landscapelike flood watersto leave deposits just tens of centimeters(3.9’s of inches) thick. Hawaiianlavas have higher silica contents (50 percent SiO2) and so they are more v;scous.Still, they can flow rapidly awayfrom the ~ent at velocities of up to 50 kilometers/hour(31 miles/hour) and leave deposits several meters thtck. Manylavas erupted from subduction-zone volcanoes have 60-70 percent SiO2, and can be very viscous. Theselavas flow very slowly at rates Of meters, or tens of meters per hour. Viscous ~avasp~le up aroundthe vent forming lava domes or stubby lava flows that are 50-100meters(54109yards) thick. EXPLANATION BOX Wehaveall experiencedthe influence of viscosity in our daily lives. Considerthe difference betweencatsup and cooking oil. Pour both on a plate. The catsup is moreviscous andpiles up in a thick mourd, just like silicarich subduction-zone lavas. Thecookingoil is ~essviscousandflows rapicly awayto form a thin layer, just like Hawaiiar~lavas. Consider the difference between ;old cooking oil pouredona plate andhot cookingoil in a frying pan. Thehotter oil, like a hotter magma, is less viscous, flows moreeasily, andforms a thinnerlayer. SECTION FIVE Six Volcano Types In this section wecontrast six majortypes of volcanoes: lavadomes, ci__nder c__one.__s_, st__rato volc__a_noes,.~j_el~_v(;;)lC,~_no~, calderas,andflood basalt plateaus. Eachvolcanotype is discussed 9 with regardto the three V’s ()f magma, anda specific examplevolcano is given. Photographsof those six examples are ,¢hown in Figures 6a through6f. LAVA DOME Theseform whenviscous, gas-poorlava piles up arounda vent like toothpaste squeezedfrom a tube. Most lava domesare the result of a single eruption or a few closely spacederuptions, but in some cases dome growth can continue for decades. Lava domes commonlyemerge on the flanks of strato volcanoes,or within their summit craters or calderas - as in the photo of the lava domein MountSt. Helens’crater (see Figure #6a). The ThreeV’s: Volume:low Volatiles: low Viscosity: medium to high Example: Mount St. Helens, Washington, 19801986 Lava Dome Height: 270 meters(295 yards) Diameter: 1000meters (1093 yards) Volume:0.07 km3 3) (0.016 miles °Slope: 30 - 37 Active lifespan: six years CINDER Theseare built by cinders falling from an eruption cloud. Expansionof gases, formerly dissolved in the magma, drive the eruption. Red-hot clots of magma are blasted into the air, wherethey cool andhardeninto spongycinders. Windcarries awaythe fine ash, while a hailstorm of coarsecinders falls to constructthe steep-sidedcone,with a slope angle of 30-34 degrees. Lava flows can simultaneously erupt from vents near the cone base (see Figure #6b). Cinder conescan formsingly or in clusters in a volcanic field. Theycan also form at summitor flank vents on strato volcanoesor shield volcanoes,as just oneeventin the growthof theselarger cones. The ThreeV’s: Volume:low Volatiles: medium Viscosity: medium Example:Par/cutin, Mexico(1943 - 1952) Height: 424 meters(463 yards) Diameter: 900 meters (984 yards) Volumeof cone: 0.08 km3 3) (.023 miles °Slope: 30 - 34 Active lifespan: nine years Following the powerful explosive eruption of Mount St. Helens on May 18, 1980, in Washington state, a lava domegrewinside the volcano’snewcrater. Herea helicopter hovers over the steamingdomein 1984. Photoby Lee Siebert(Smithsonian Institution). Figure #6a CONE Paricutin Volcanois a famouscinde~conethat wasbornin a Mexicancornfield on February20, 1943,as the farmerandhis family watched.It wascarefully studiedall throughout its nine-year lifespan. This photowastakenfrom2 1/2 kilometers(1.55 miles) to the north in March,1944. The landscapeis buried in ash. Ruggedlava flows, eruptedfromvents at the northeastbase of the new cone, are advancing northward. Photo by Arno Brehme. Figure# 6b 10 STRATO VOLCANO Thesesteep-sided structures grow from the repeated eruption of viscous magma.Gas-rich viscous magma can erupt explosively. This blasts the magmaapart and blankets the volcano’s slopes with the fragments - ash, cinder, and pumice. Theseexplosive eruptions are commonly followed by eruptions of gas-poor magma,which producethick flows of slowly movingblock lava (see Figure #13). Thealternation of ash and lava layers, or strata, gives rise to the name strato volcano (see Figure TheThreeV’s: Volume: medium Volatiles: medium to high Viscosity: medium to high Profile of MountRainier Strat.~ Volcanotaken fromthe east. Theirregular su’nmit wascarved by glaciersthat still coverthe upperslopes.This active volcanotowersover th~ nearbycities of Seattle and Tacoma. Past eruotions havemelted snowand ice at the summitand produced dangerous mudflowsthat rsced downthe flanks and far out into the lands beyond.Photo by RichardS. Fiske(Smithsonian Institution). Example:MountRainier, Washington Height abovesurroundings:2.3 km(1.4 miles) Diameter:8 kilometers(4.96 miles) Volumeof cone: 86 km3 3) (20.5 miles °Slope: 20 - 35 Active lifespan: abouthalf a million years Figure #6c SHIELD VOLCANO Thesebroad, gently sloped volcanoes (see F’~gure#6d), named for their resemblance to a warriods shield, are formedby repeatederuptions of ~ tluid lava (see Figure #12). Eruptions are usually non-explosive, and issue from the summit or from fissures that mayradiate from the summit or partly encircleit. Volume: mediumto high Vo~atiles:low VLscosity: Example: MaunaLoa, Hawaii Heightabovesea floor: 9 km(5.58 miles) Length.at sea level: 130km(80.73 miles) 3 Volume:65,000 - 80,000 km 3 (15,535-19,120 ) miles °Slopeon land: 3 - 10 Active lifespan: about600,O00"years Profile of snow-capped Mau~la LoaShieldVolcano, Hawaii,takenfromthe ..=ast. Mauna Loais oneof Earth’s mostactive volcanoes.Its last eruptionwasin 1984.Phot(,by RichardS. Fiske (Smithsonian Institution). Figure# 6d 11 CALDERA Theseare circular to oval-shaped collapse depressions (see Figure#6e- also Figures#18, #19 and#20). Theyformwhena large amountof magma is rapidly eruptedfrom a hugechamber underground.Theeruption removessupport for theoverlyingportionof the volcano,whichcollapses into the void, producingthe caldera.Theyare common on strato volcanoesand shield volcanoes,but giant calderaswith diametersof 30-100 kilometers(18.6-62.1miles)cancut acrossa landscapebuitt by saveralearlier volcanoes. Exceptfor Aerial viewof CraterLake,Oregon, lookingtocalderasonshield volcanoes,mostother calderaward the east-southeast. Despite its name, this formingeruptions are extremelyviolent. They is a largevolcaniccaldera,formed about5,700 involve viscous, gas-rich magmas and produce B.C.in oneof thelargestexplosive eruptions on toweringashcolumns anddevastatingpyroclastic Earthin thelast 10,000 years.CraterLakeis the flows, ground-hugging avalanches of hot ashand deepest bodyof freshwaterin theUnitedStates. gas, Thelargest knownexplosiveeruptionstypiWizard Islar~l is a younger conethat grewwithcally produce large calderas. in the caldera.Photocourtesyof RoyBailey (U.S.Geological Survey). TheThreeV’s: Volume:medium to high Figure #6e Volatiles:lowto high Viscosity:lowto high Initial caideradepth:1,220meters (4002ft.) Presentlake depth:590meters(1935feet) Example:Crater Lake, Oregon 3 Volumeof pumice’andasherupted: 100km Caldera width:8 x 9 km( 4.5 x 5.5 miles) 3) (23.9miles Activelifespanof volcanicsystem:about 400,000years FLOOD BASALT PLATEAU Thesevoluminousfluid lavas erupt from swarmsof fissures and cover vast areas. They includesome of the largestsingle eru_otiveunits known.Repeatederuptions over geologically short periodso| timebuild upthick lava plateaus with verygentleslopes(seeFigure#6f). Certainflood basalt provinceshaveagesthat coincidewith Earth’smajorbiological extinction events, andmanyscierltists believe that flood basalteruptions playeda.critical role in theevolution of life ontheplanet. TheThreeV’s: Volume:high Volatiles:low Viscosity:low Example: ColumbiaPlateau, Washingtonand Oregon Thickness: upto 4.2 km(2,6 miles) 2 2) Areacovered:164,000km (63,140miles Volume:175,000km3 3) (41,825miles °Slope:lessthan2 Activelifespan:2 - 3 million years 12 Lavasof the Columbia flood basaltplateaublanket about one-quarter of Washingtonand Oregon states. Herea sequence of the lavas about150meters thick is exposed in thewallsof Washington’s PalouseRiver Canyon. Photoby DonaldA. Swanson (U.S.Geological Survey). Figure #6f SECTION SIX Different Kinds of Eruptions and Volcanic Rocks Volcanic eruptions can have manydifferent styles of activity andcan producemanydifferent deposits. In this section, volcanic eruptions are discussedin two broadcategories: explosiveeruptions that produce .mr_roclastic (Greekfor "fire-broken’) deposits of ash, cinder, and pumice; and non-explosiveeruptions that producelava flows. A common pyroclastic eruption style is for the mixture of hot gases and magr~ato be blasted straight up fromthe volcanic crater into the air at speeds that can reach 500 r~eters/second or 1,800 kilometers/hour (5905 feet or 1117 miles/hour) (see Figure #7). In ~helargest explosive eruptions, the cloudscan ri.;e to about50 kilometers(31 miles) aboveEarth’s surface. Thelargest anddensestpa’ticles are the first EXPLOSIVE ERUPTIONS AND PYROCLASTIC DEPOSITS to fall from the eruption cloud. "~’heseaccumulate Explosive eruptions are poweredby rapidly closest to the vent, helping to ~uild the volcanic expandinggases. Usually those gaseswere once cone.Thesmallerandless denseash particles fall at greater distances. Such ceposits generally dissolvedin the liquid portion of the magma itsel! and bubbledout of the liquid as the magma rose blanket the landscapeandare ~-alled pyroclasticbeneath the volcano and pressure on the magma fall deposits. Because the eruption cloudsare carwasreduced. In other cases, hot magma comesin ried by the wind, the deposits c~:)mmonly havethe shapeof an oval, elongatedir the direction the contact with water in a lake, as snowor ice, or underground,with similarly explosive results. In wind is moving.Thetotal thickr~ess andthe avereither case, the expandinggasesblast the magma age particle size generally decreasewith distance into fragmentsthat rangefrom car-size blocks to from the volcano.Oneof the fi’st tasks for volcafine dust, Thesefragments,regardlessof size, are nologists following explosivevolcanic eruptionsis called .oy_roclasts, andtheir deposits are called mapping the distribution of the deposits. oyroclastic. Pyroclastic-fall depositof whib~pumiceandoccasional gray fragmentsof lava. Notethat a rather narrowrangeof pumicesizes is present. This is typical of pyroclastic-falldepo,,;its. Fineashparticles werecarried awayby the windto fall at much greater distances. This depos’l waseruptedabout 15,000years agofrom SanJLanVolcano,Mexico. A hammer gives the scale. Ph:)to by James F. Luhr (Smithsonian Institution). Cerro NegroVolcano,Nicaragua,viewedfrom the east, duringan eruptionin 1968.Gas,cinders, and ash are being blastedinto the air. Photoby Tom Bretz. Figure #7 13 Figure #8 At a large numberof field stations they describe the appearance of the deposit, and makemeasurementsof deposit thickness, grain size, color, andother properties. Theyalso collect samplesfor laboratory analysis. Because particles of different sizes anddensitiesfollow different paths to the ground,a single exposureof a pyroclastic-fall deposittypically hasa very limited rangeof particle sizes (seeFigure #8). Another important mechanismof explosive eruption producesground-huggingclouds of hot gas, pumice, and ash celled pyroclastic flows. Theseare commonlygenerated along the margins of explosive eruption columns,wherethe air acts to slow the upwardrise. Manytimes the air wins the fight, andthe densecloud of gas andash collapses back around the vent and flows downthe flanks of the volcano. Thesehot, churning clouds moverapidly downhill at velocities up to 100kilometers/hour(62.1 miles/hour), generally following stream valleys (see Figure #9). Becausethey moveso rapidly, andengulf anythingin their paths, pyroolastic flows are the mostdeadlystyle of volcanic eruption. Becausethey are formedfrom the entire eruption cloud, Dyroclastic-flow deposits contain a wide rangeof particle sizes (see Figure #10). In this way, they can be distinguished from pyroclastic-fall deposits, which havea muchnarrower rangeof particle sizes (see Figure #8). Pyroclastic-flow deposit of gray pumicessurroundedby light-colored ash. Notethat a large rangeof pumiceandash sizes is present. This is the CampanianIgnimbrite, erupted about 34,000 years ago from a vent just west of Naples,Italy. "lgnimbrite"is a termfor a particularly densetype of pyroclastic-flowdeposit. The headof a geologist’s hammer provides scale. Photo by James F. Luhr (Smithsonian Institution). Figure #10 On the sea floor, low-viscosity magmas commonly erupt to form pillow lavas. The hot magma oozes out like toothpastefrom a tube andquickly freezes against cold sea water. This produceselongated and bulbous pillow shapes (see Figure #11). Pillow lavas also form wheniava erupted on land reaches a body of water. Low-viscosity magmas erupted from volcanoes on land, such as Kilauea and MaunaLoa in Hawaii, commonlytake on two forms. Pahoehoelava has a braided, ropey form, whereasaa has a spiny texture (see Figure 12). Both pahoehoeand aa types can also be found amongsea-floor lavas andat subduction-zonevolcanoes. In the latter environment,however,viscous lava moreoften movesas very sluggish jumbles of large andsmall blocks. This is called block lava (see Figure #13). A pyrodasticflow racesdowna streamvalley on the southflankof ArenalVolcano,CostaRica, on July 13, 1987.Thesehot churningcloudsof gas, pumice,andashmoveat speedsup to 100kilometers/hour (62.1 miles/hour). Theyare the most deadly type of volcanic phenomenon, destroying everythingin their path. Photoby WilliamG. Melson(Smil~sonian Institution). Figure #9 NON-EXPLOSIVE ERUPTIONS AND LAVA TYPES Gas-poor magmas erupt to form lava flows. Lava occurs in four maintypes: Dillow, Dahoehoe, aa, andblock. 14 Pillow lavas photographed froma researchsubmarinenearthe summitof Loihi Volcanoon July 20, 1988. Thesepillows lie about 1 kilometer (.621 miles) belowsea level atop the youngest active volcano in the Hawaiianchain. Photo courtesy of HawaiiUnderseaResearchLaboratory. Figure #11 These1972lavas on Mesouth flank of Kilauea Volcano, Hawaii, showsa lava in the backgroundand pahoehoe lava in the foreground. Thewidth of the photo is 4 meters(13 feet). Photoby RichardS. Fiske(SmithsortianInstitution). This19911ok)cklava flow fro’n ColimaVolcano, Mexicois a jumbleof fresh igray andangular) andoxidized (red androughMocksof various sizes. Thehammer is 30 ce ~timeters(11 inches) long. Photoby ,JamesF. Luhr(Smithsonian Institution). Figure #12 Figure #1 ~ SECTION SEVEN Eruption Forecasting and Prediction: Successat MountPinatubo (Philippines) in 1991 I1 youlive near a volcano, you wouldprobably wantto know:When will it erupt? Will lave or ash comeour way?. Howoften will it happen?Will we have to leave our home?Whencan we go back? Scientists monitoringvolcanoescannotforetell the future, but with intensive efforts they can provide long-term forecasts andshort-term predictions of likely future eruptive behavior.Howdo they do it? By monitoring the volcano with various instruments, through basic geological studies in the field, andby analysisof the historical eruptivepatterns, forecasts can be done. This is the sameapproachyour medical doctor takes in monitoring your health. Your doctor uses insVumentsto take your temperature,listen to your heartbeat, and take your blood pressure. Yourdoctor also asksabout the history of diseases in your family, all in anattemptto keeptrack of your health prior to diagnosisandtreatment. The 1991 eruption of MountPinatubo in the Philippines (see Figure #14) providesan excellent casestudy of successfulvolcanotogicalprediction. Based mainly on scientists’ warnings, some 250,000peoplesafely evacuatedbefore the maior June15 eruption. This section tells you the story of monitoringefforts at MountPinatubo. For as long as the oldest villagers could remember,MountPinatubo had been quiet. Then, on April 2, 1991, peoplewere startled to see an explosionof steamand ash from a vent on the volcano’s northeast flank (see Figure #15). Within 15 ~(;’~ ~ ~ ~ [XPLANATION ~apsho~ngcenUalluzon~lan~in ~e Philippines,andthem~ation of MountPina~bo and ot~rvo~anoes ~athaveerupled in thelast million years(Pli~ene toQuaterna~). The~anilatre~hma~t~ l~ati~~erethe Eurasian Platebeginsto su~ucte~ardbenea~luzon and ~e Philippine SeaPlat~.~is suUd~tion zoneg~erat= ~e magmas~hateruptin luzon. Cou~esy of Christopher G. Ne~all(U.S.Geological Su~ey). Figure #14 days, scientists from the Prilippine Institute of Volcanologyand Seismologyinstalled a portable seismoq_raDh just west of Pinatubo. Morethan 200 volcanic earthquakeswere recorded in its first twenty-four hours of operation Basedon their field andlaboratory studies, scientists prepared a volcanic-hazards mapthat showedthe course of ancient pyroclastic flows (see Figure #16). Somehad reached Clark Air Force Baseand nearby densely populated areas. HAZARD ZONES ~ ~’~ I~ Pyroclastlc-flow - ~’~[~t~~ ,,,~= ¯ I~JPyroclastlc-flow buller ~’- ". Volcanic-hazardsmapdistributed on May23, 1991by the Philippine Institute of Volcanology andSeismology andthe U.S. GeologicalSurvey. Patterns showzonesexpectedto be affected by pyroclastic flows and mudflows.Dashedlines showactual distribution of pyroclastic-flowdeposits following the June15, 1991,eruption, whichmatches well with the pre-eruptionhazard zones.Courtesyof ChristopherG. Newhall(U.S. GeologicalSurvey). Alignedcraters on the northeastflank of Mount Pinatubo.Theseformedon April 2, 1991,as one of the first warningsigns of the majoreruption that took place21/2 months later onJune15-16, 1991.Thevents in the foregroundare inactive, but thosein the background are still steaming¯ Photo by Christopher G. Newhall (U.S. GeologicalSurvey). Figure #16 Figure #15 Earthquakedetection is an essential part of volcanomonitoring. Before an eruption, rocks can crack as they are pushed apart by’ ascending magma.Seismometers detect this cracking as earthquakes. At manyvolcanoes the numberof earthquakesincreasesbefore a large eruption. Alerted by the earthquakes,scientists recommended evacuation of everyonewithin a 10 kilometer(6.21 mile) radius of the summit. A teamof scientists from the Philippine Institute and the U.S. Geological Surveyset up seven seismic stations. Theserecorded 50-90 earthquakes each day through May 10. Data were processedat Clark Air Force Base, a major U.S. facility at the easternfoot of the volcano. Volcanologistsquickly beganfield studies at MountPinatubo. They sought to establish its record of past eruptions. This is an essential step in monitoring active volcanoes. The scientists were shockedto find huge deposits from earlier explosive eruptions, the youngestjust 500 years old. 16 Scientists also developeda warning scheme withfive levelsof alert andsentit to publicofficials. Usinga telescope-like optical instrumentsensitive to sulfur dioxide (SO2)gas, volcanoiogists detected a ten-fold increase in SO 2 emissions from summitsteamvents during May13-28, a sign that magma wasrising towardthe surface. In early Junethe focal point of mostearthquakes shifted 4-8 kilometers (2.4-4.9 miles) northeast, to the region beneaththe steamvents. ~ - a continuous, rhythmic vibration associated with movementof magma was detected, along with a drop in SO 2 flux. Scientists also installed twoelectronic tiltmeter~ near the active steamvents. Theseinstrumentsmeasurechangesin the groundsurface that can be caused either by the movementof magma below or by pressure from released gases. The tiltmeters recorded a bulging of the upper east flank. This wasfollowed by eruption of a lava dome Below,a typhoonraged, a’~d heavyrains trigjust north of the most vigorous steamvent. Begeredmudflowsthat swept thr(=ugh several towns tween June 7 and 11, the lava domedoubled in anddestroyedmanybridges. After June 16, activsize. Eruption of this lava domeconfirmed the ity decreased in intensity, but a.,,h eruptionscontinexistence of an active magmaticsystem- a storued until September2. The June 15-16 eruptions age area and channels through which magma formeda caldera near the top ~f MountPinatubo, could movethrough the upper crust to reach the about 21/2 kilometers(1.55 mil~s) in diameterand surface. more than 650 meters (213;! feet) deep (see In the daysof early June,scientists raisedthe Figure #18). The floor of the new caldera was alert level to a 3 and then to a 4. When the lava abo~t 800meters abovesea I,~vel, roughly 1,000 domeappeared,they issued a red alert - level 5. meters (3280 feet) below the summitof the volOnJune 10, Clark Air Force Basewas evacuated canobefore the eruption. andaircraft valuedat onebillion dollars wereflown The eruptions and later mudflows, spawned tosafety. as the new loose ash and pumicedeposits were On June12,duringPhilippine Independence stripped away by rains, buried some100,000 Daycelebrations, thefirst ofa series ofpowerful homes andaffectedthe liveliho x~of over a million eruptions blasted an ashcolumn to 19 kilemeters persons. Muollows continued to be a problem abovesealevel(seeFigure #17).Moreeruptions, manyyears after the 1991eruption. pyroclastic flowsandearthquakes followed, and still, theworst wasyettocome. Viewof the new2-kilometero (1.2 mile-) wide caldera of MountPinatubo,looking from above toward the south on August1, 1991. A small explosionhasjust occurred.Photoby Thomas J. Casadevall (U.S. GeologicalSLrvey). MountPinatuboeruption cloud of June12, 1991 rises into the atmosphere.Photo taken from Clark Air ForceBase,20 kilometers(12 mi!es) east of MountPinatubo. Photoby DavidHadow (U.S. GeologicalSurvey). Figure #18 Figure #17 OnJune14 an infrared video cameraat Clark Air ForceBaserecordeda sudden,zipper-like passage of brightness (heat) across the upper east flank of Pinatubo,whichvolcanologistsbelievedto be a fissure vent opening. The maineruption, the secondlargest of the century, beganthe following day. Pyroclastic flows swept nearly all areas covered by prehistoric deposits of a similar type, blanketing about 100 km2 (38 miles2) (the dashedline on Figure 16). The eruption columnmushroomed to heights of 40 kilometers (24.8 miles), well into the trt~. 17 Abouteight-hundredpeopledied in the eruption, mostly from pyroclastic flows, mudflows,and post-eruption disease. However,tens of thousandsof lives were savedby the monitoring and warningefforts of scientists andgovernment officials. Comparethe volcanic-hazards maddevelopedfor MountPinatuboprior t¢ the June15 eruption with the actual results of :he 1991eruption (see Figure #16). Theclose similarity is a graphic demonstrationof the successof volcanologists’ efforts at Pinatubo.Unfortunatgly, volcanologists rarely havethe benefit of ext,=nsive and costly monitoringandfieldwork neededfor reliable forecasts andpredictions. SECTION EIGHT SomeCommonQuestions about Volcanoes (1) Whatis an active volcano and how manyare there? A volcano should be consideredactive if it has the potential to erupt again. But howcan you tell whena volcano has finally becomeextinct? There is no easy way. Oneapproachis to assume that a volcanois not likely to eruptagainif it hasn’t had an eruption in the last 10,000 years. SmithsonianVolcanologistslist about 1500volcanoesthat eruptedon land or in shallowwater during that time, shownin Figure #3. About 540 of these volcanoes have had historically reported eruptions. Eachyear, 50-70 volcanoeserupt. As you read these words, about 15 of Earth’s volcanoesare probablyerupting. (2) Whatwasthe largest volcanic eruption of the last 100,000years? The eruption that producedIndonesia’s gigantic Tobacaldera (see Figure #19) about 74,000 years ago is the largest nowknown. It ejected about 3,000 km3 (717 miles3) of pumiceand ash, roughly 3,000 times as muchas MountSt. Helens ejectedin 1980. (3) Are fewer people dying from volcanic disasters nowthan in the past? "Natural calamitystrikes at aboutthe time whenoneforgets its terror." - Japaneseproverb Eventhough scientists have an ever-deeper understandingof volcanic processes, this knowledgehasnot yet led to a decline in eruption-related deaths. From1900 to 1986, the average numberof humandeaths from volcanoes per year was880; Landsatsatellite photo of the Tobacaldera, Sumatra,Indonesia.Fourseparatelarge explosive eruptionshavetakenplace herein the last 1.2 million years. Thepresentcaiderais 100kilometers (62.1 miles) tong and30 kilometers wide.It formedduringthe youngest of the eruptions, 74,000yearsago. LakeToba(black) covers morethan half of the caldera.Dataacquired in May,1987. Figure #19 morethan from 1600to 1899, whenan averageof 620 people per year died in volcanic disasters. Although the numberof deaths caused by posteruptionstarvation hasdeclinedin this century,the numberassociated with pyroclastic flows and mudflowshas increased. A major reason is that global population has increaseddramatically in recent centuries - many morepeopleare living near dangerousvolcanoes. Manynations lack the money,scientific resources, or political will to monitortheir volcanoes. TABLE 2 The ten most deadly eruptions in history. Volcano Tambora Krakatau Pelde Nevadodel Ruiz Unzen Kelut Laki Kelut Santa Maria Galunggung Year 1815 1883 1902 1985 1792 1586 1783 1919 1902 1822 Country Indonesia Indonesia Martinique Colombia Japan Indonesia Iceland Indonesia Guatemala Indonesia Deaths 92,000 36,417 29,500 23,080 14,524 10,000 (?) 9,350 5,110 4,500 (?) 4,011 All volcanoes except Laki are located above subduction zones. Data from Volcanoes of the World (Simkin and Siebert, 1994). 18 In addition, peopleliving near long-dormant volcanoesmaybe unawareof the threat in their backyards. Field and laboratory studies of past eruptions, instrumental monitoring, improvedcommunications, and public education are neededto savelives. (4) Whatare the ten mostdeadlyeruptions in his- tory?. Of the ten mostdeadly eruptions in history, listed in Table2, all but the IcelandicLaki eventin 1783 occurred in a subduction zone. Theseare sites where descent of an oceanic plate into Earth’s mantle carries seawaterinto the zone of melting. As a result, subduction-zonemagmas are rich in water, andexpansionof that wateras steam near the surface drives the explosive eruptions that makesubduction-zonevolcanoes so dangerous. Volcanoespose a variety of hazards. Many humandeaths are caused directly by erupted materials, most commonlywhenpeople are engulfed by fast-movingpyroclastic flows. Duringor even long after an eruption loose ash and other debris can be sweptup by currents of flood waters to create destructive mudflows. Wheneruptions occur in the sea, they can generatetidal waves,or tsunami, which can devastate coastal areas far from the eruption site. Of her deathsare causedby earthquakes, lightning, disease, and starvation associatedwith eruptions. (5) Whatwas the largest explosive eruption historical time? Thelargest historical explosive eruption took place in 1815at TamboraVolcano, on Indonesia’s Sumbawa Island. The Tamboraeruption ejected about 50 km3 (31 miles) of magma,which translates to about 150 km3 (93 miles) of pumiceand ash. An estimated 10,000 people were killed directly, and another 82,000died as a result of starvation anddisease.Theeruption left a circular area of collapse, called a caldera, about6 kilometers in diameter at Tambora’ssummit(see Figure #20). Theash and volcanic gasesinjected into the upper atmosphereby the Tamboraeruption formed a globe-encirclingcloud that filtered the sunlight andaffected Earth’s weather. Theyear 1816, following the Tamboraeruption, has beendescribed as the "Year Without a Summer." In North Amedca, records of the Hudson’s Bay Company show that the summerof 1816 was amongthe coldest ever recorded. Unseasonably strong winds from the north and northwest brought three major episodesof frost in early June, early July, and mid-August. 19 NASA spaceshuttle photograph of Tambora Volcano, Indonesia, and the 6.5-kilometer (4.03 mile) widecalderamarking its ;ummit,left by the 1815eruption. This wasthe largest explosive eruptionin historicaltime. Figure #20 Thesefrosts reachedas fa- south as Philadelphia, PA, and Trenton, NJ, causingpoor harvests and food shortages. In Europe, the summerof 1816was exceedingly wet an( cool. This dismal summeris credited with having inspired Mary Shelley to write Frankenstein~mdLord Byron his somber poemDarkness, whi,’h was written in June, 1816, on the shores of Lake Geneva,Switzerlan~A short portion is reprinted here: Darkness I hada dream,whichwasnot ~ II a dream. The bright sun wasextinguish’d, andthe stars Did wanderdarkling in the eternal space, Ray/ess,andpathless, and the icy earth Swung blind andblackeningin ’he moonlessair; Morn cameand went - and came, and brought no day,... Lo,’d Byron (6) Howdo volcanoes benefit mankind? Although most discussions of volcanoes focus on their destructive qualities, volcanoesalso play manypositive roles in our lives. Theair we breatheandthe water wedrink originally wascarried to Earth’s surface in volcanic eruptions. Volcanicrocks are usedall over the world as construction materials and building stones. Magmas ponding beneath volcanoes h~,lp to concentrate copper, silver, gold, andmanyother metals that our society dependsupon. Volcanic heat is tapped to generate electricity in manygeothermalareas around the world. For example, Reykjavik, the capital city of Iceland, has near y 100,000people andgets 70 percentof its heat ;.nd hot waterfrom wells drilled into hot volcanicro(k. The Geysersgeothermalarea in northern California generatesenoughelectricity to meetthe needs of two million people. Volcanoesalso benefit agriculture becausesoils developed on volcanic rocks are extremely fertile. Volcanic ash falling fromthe air canact as a naturalfertilizer. SECTION NINE The Three Volcanic RocksIncluded in this Kit This set contains three small volcanic rocks for your rock collection: pumice, obsidian, and basalt. Usea magnifying glass to observe them closely. Find a placewith bright sunlight. DIRECTIONS PUMICE: Thewhite to gray rock is pumice, which consists of about 95 percent natural glass and 5 percentcrystals of quartz (silicon dioxide: SiO2). Quartzhas a grey color and you should be able to see a crystal or two with your magnifier. Youmay also see a few dark spots. Theseare rare crystals of magnetite (iron oxide: Fe304). The glass pumiceforms a sponge-like network, signifying that it contains a lot of emptyholes nowfilled by air. Some of the larger holes are obvious on the surface of the pumice, but manyothers are too small to see. Becauseof all these holes, pumice feels light. Morecorrectly, it is less densethan other rocks. Dropyour pumicein a glass of water. It floats! All that trapped air makespumiceless densethan water. If you leave the pumicesoaking in water long enough,the water will eventually seepin to replacethe air andthe pumicewill sink. Youcan alwaysdry it out in the sunor an ovenand dothe trick again. crystals. In this case, though,the glass doesnot have a sponge-like texture, and the crystals are mainly plagioclase, a silicate mineral containing sodium, calcium, and aluminum. Obsidian forms from viscous, silica-rich magmas that havelow gas contents. Becausethese magmas are so viscous, atomscannot easily migrate to growing crystal faces, andtherefore few crystals develop,instead the liquid solidifies as glass. Obsidian is well knownfor the wayit breaksalongcurvedfractures. Early humanstook advantageof this feature and learned to form razor-sharp blades and arrowheadsfrom obsidian. BASALT: Thedark gray rock with the dull finish is basalt. This lava contains abundantsmall crystals of olivine, andpyroxene,two silicate mineralsthat are rich in iron and magnesium. Thesewill appear as small reflecting spots under the magnifier. Basalt forms from magma that is poor in silica and has low viscosity. Basalt is the mostcommon volcanic rock on Earth. Under the sediment on the oceanfloor is a layer of basalt lava about2 kilometers(1.24 miles) thick. Hawaii and other volcanic islands are giant mountainsof basalt that rise up fromthe seafloor. OBSIDIAN: The shiny black rock is obsidian. Like the pumice,this obsidian also consists of about95 percent glass and 5 percent PART TWO: BOOKS AND EDUCATIONAL REFERENCES Volcano & Earthquake, by Susanna Van Rose, 1992. A Dorling-Kindersleyb~)okpublished in the U.S. by Alfred A. KnopfInc., NewYork anddistributed by RandomHouseInc., NewYork, 1992. (A richly illustrated book written for teenagersto adults.) Volcanoesof the World, by TomSimkin and Lee Siebert. Geoscience Press, Phoenix, 1994. (Smithsonian compilationandinterpretation of data about Earth’s volcanoes; rich in maps, photos, drawings, andespecially data; written for a wide audienceas well.) 20 ABOUT VOLCANOES Volcanoes, by SeymourSimon. Morrow Junior Books,NewYork, 1988. (A short, illustrated book wdttenfor children ages8-12.) Mountainsof Fire: The Nature of Volcanoes, by Robert W. Decker and Barbara B. Decker. Cambridge University Press, Cambridge,U.K., 1991. (A well-researchedgeneral treatmentof volcanoes with abundantdrawingsand photographs;written for a wide audienceranging from high school studentsto professionalvolcanologists.) LOW-PRICED, EDUCATIONAL VOLCANOMATERIALS This DynamicPlanet A full-color wall map,1 meterby 11/2 meter (3.3 feet by 4.9 feet) (revised in 1994)that should be on the bedroom wall of everychild interested in our planet, its volcanoes,earthquakes,meteorites, andplate-tectonic activity. This eye-pleasingwodd mapusescolors to designateelevation. Superimposedon it are: ¯ Locations of over 1500volcanoesactive dudng the last 10,000years, plotted in four agecategories. ¯ Locations of over 24,000 earthquakes,largely from1960- 1990,plotted in three magnitudecategories andtwo depth ranges. ¯ Locationsof 139meteoriteimpactcraters. Also includedare: ¯ A three-dimensionalcross section of the earth illustrating its majorzonesof volcanoes andearthquakes(a color versionof Figure2 in this section). ¯ A text treatmentthat givesa primeron plate tectonics, volcanoes,and earthquakes.This wonderful mapcosts only $7.50 ($4.00 per mapplus $3.50 per order for postage and handling). Orders shouldbe sent to: USGS Information Services Federal Center, Box 25286 Denver, CO80225 Specify "DynamicPlanet’ and makecheck or moneyorder in USdollars payable to "Interior Department- USGS’.Within the United States, mapsmayalso be ordered using a credit card by calling toll free 1-800-USA-MAPS. Irmide Hawaiian Volcanoes This 25-minute color video was producedin 1989by the late Maudce Kra’ft, in collaboration with the Smithsonian Institution and the U.S. Geological Survey. It is narrated by RogerMudd. This video goes beyondthe t,eauty of Hawaii’s surface eruptions and takes you deep underground where you will learn about the underground magma plumbing systP, ms. It contains spectacularviewsof lava founta,nsandflows, scientists at work, as well as rare ~ady20th century footageof early eruptionsandscientists. Awarded 5 Stars by the Journal of Geological Education "If you buy only one video about Hawaiianvolcanism,this should be the one.’ A teachers’guide (22 pages)is ~tlso available. contains questions and answer.,; relating to the video, as well as three laboratoryexercises. The video costs $20. Please. specify VHSor VHS-PAL format. The teachers’ guide costs an additional $5. Makecheck or moneyorder in US dollars payableto SmithsonianI,~stitution. Only pre-paid orders are accepted. Purchaseorders cannot be accepted. Pleasesendorders via postal mail to: RichardS. Fiske Museum of Natural History MRC119 Smithsonian Institution Washington, DC20560, USA ELECTRONIC ACCESS TO VOLCANO RESOURCES Programsto Downloadand Run on your Computer SEISMIC/ERUPTION This programoffers a woddmapand a variety of regional and local mapsthat showearthquakes and/or volcanic eruptions in time sequencesince 1960. Earthquakesare shownby circles and volcanic eruptionsby triangles. Thesizes of the symbols indicate the size of the earthquakeor erup, lion. Colors indicate the depth of the earthquake or the type of eruption (lava, ash or both). When an eruption occurs, the nameof the volcano is shownnext to it. This is an extremely engaging program,that dramaticallyindicates that our planet is alive. 21 Segments of this programare used throughoutthe Smithsonian’s new Geology, Gems.and Minerals exhibit in the National Museum of Natural History. The programwasdevelopedby Ala’~ Jonesof the State University of NewYork, Bing’~amton,using earthquakedata from the U.S. Geo.ogical Survey anderuption data from the Smithsonian.It is well worthyour effort to retdevethis program. Note that this programonly works on IBMtype computers,Current(9/96) reqL irements are: Windows 3.1, Windows 95, or IBM0-3/2. To download this programfollow thesesteps: DIRECTIONS Point your webbrowserto: http://www.geol.binghamton, edu/facu~ty~ones To load the Windows 3.1 version: (1) Openthe WindowsFile Managerand select File/Create Directory. In the windowthat pops up type: "c:/volc" andclick "OK". This is a temporary directory that can be erasedwheninstallation of the Seismic/Eruptionprogramis complete. (2) In the browser, scroll down to the seisvole.readme link for information regardingthis program. (3) Click on the seisvole.zip link to downloadthe Seismic/Eruption program. A "Save As" dialogue box should appearin the "directories" box. Goto c:/volc andclick "OK". (4) A "Saving Location" box will appearshowing status of the download.It maytake awhile to save because the file is 4.4 Mbin size. (5) Files with the .zip suffix are files compressed with the PKZIPprogramand needdecompression. At the time of publishing (9/96) PKZIPwasfreewareandcould be obtainedover the Internet at the following address: http://www.yosemite,net/help/win31_pkzip.html If this addressis no longer valid, performa web search using PKZIPas the key word and go to a site that has the program. (6) Follow the instruction for downloadingPKZIP anddecompress the seisvole.zip file. Makesure to use the -d option. For example,at the DOSprompt type: pkunzip-d seisvole.zip (7) From the WindowsProgram Manager select file/run/browse, go to c:/volc/setup.exe,click "OK" and follow the dialog on screen to completethe installation of the Seismic/Eruption program. ERUPT This programallows you to design a volcanic landscapeas it builds up in cross section on the screen. The user choosesthe eruption types, the location of the vent, and other parameters suchas wind speed. The programcan be steppedat any time and a neweruption type selected. In this wayone gains an understandingof howa volcanic terrain growsthrough the accumulationof deposits from various eruptions. The program was created by Kenneth Wohletz of the Los Alamos National Laboratory. Note that this programonly works on IBM-type computers. To begin, point your webbrowserto: http://geontl .lanl .gov/page1/directory/wohletTJeru pt.htm There you will find options for downloading different versions of ERUPT. Detailed instructions are given below for loading the Windows 3.1 version. (1) Openthe WindowsFile Managerand select File/Create Directory. In the windowthat popsup type "c:/erupt" andclick "OK". (2) In the browserselect the version for Windows 3.1 currently version 2.0 - named"er20-16". A "SaveAs" dialog box should appearin the directories box. Goto c:/erupt andclick "OK". (3) A "Saving Location" box will appear showing status of the download.It maytake a while to save because it is 2.6 Mbin size. (4) In File Manager go to c:/erupt anddoubleclick onthe file there. Thiswill start the installation. (5) Click "Setup"to unzip the files andget to the "Erupt 2.0 Setup" screen. (6) Followinstructions andinstall to the "Erupt 20" directory. (7) In File Manager, select c:/erupt, then File/Delete to removedirectory. Click "OK" then "Yes". (8) In ProgramManager,openthe group in which you wantthe Erupt icon to reside. (9) Do File/New. Click "ProgramItem" button and then "OK". (10) A "Properties Dialog" box will appear.Fill as below: Description: Eruption Command line: c:/erupt20/erupt.exe Click "OK" (11) To start ERUPT, double click on the volcano icon that appearsin the window. SITES ABOUT VOLCANOESON THE WORLD WIDE WEB Bulletin, a monthlyreport of all volcanicactivity on the planet. This is the sameinformation read by professional volcanologists aroundthe world to find out newsof recent eruptions. A list of Earth’s 1500 vo}canoesknownto have erupted during the last 10,000years is also given along with basic informationfor each. This site contains an extensive set of links to other sites aroundthe world, organized by region. Welist only four sites, but eachcontainslinks to manyother volcanosites aroundthe world. Smithsonian’s Global Volcanism Program http://www, volcano.si.edulgvp/ This program is devoted to the study of Earth’s active volcanoes.Hereyou will find the latest issues of the Global VolcanismNetwork 22 Volcano World http://volcano.u nd.nodak.edu/ Thisis a site devotedto educatingschoolchildren and visitors to U.S. National Parks and Monuments about volcanoes. It is run out of the University of North Dakotaand funded by NASA. VolcanoWorldincludesmodernand near real-time volcanoinformation, with extensiveuse of remotesensing imagery. Under their section Learning About Volcanoesare the topics: Ask a Volcanologist, andVolcanoFacts. Michigan Technological University HomePage http://www, geo.mtu.edu/volcanoes/ This site containslots of volcanoinformation and imagesabout recent and on-going eruptive activity. Particular emphasisis placed on volcanohazardsmitigation, remote-sensingof volcanoes and eruption clouds, and histor cal eruptions of Guatemalanvolcanoes. It also includes a geographiclist of individual volcano~ageswith eruption reports. U.S. Geological Survey: CascadesVolcano Observatot’y http://vulcan.wr.usgs.gov/home.html The CascadesVolcano Observatory is focusedon the eruptive history ant hazardsof active volcanoesin the CascadeRang~,which runs from northern California, through Oregon and Washington,and into British Columbia(Canada). This site provides a wealth of information about thesevolcanoesas well as excellent generalinformation about volcanic features and phenomena, volcanic hazards, and volcanc monitoring techniques. GLOSSARY sa lava: (ah-ah) a form of lava, common on Hawaii, with a rough surface and spiny protrusions (see Figure #12). ash: the smallest solid particles producedby an explosiveeruption, definedas less than 2.5 millimeters(3/32 inches) across. Ashparticles include glass and crystals from newly erupted magma as well as ejected fragmentsof older rocks. block lava: a type of lava, commonly erupted in subductionzones, that movesas a jumble of separate blocks rangingfrompebblesup to the size of small houses(see Figure #13). caldera: a cimutar to oval-shaped depression, generally more than 1 kilometer (.621 miles) across, formedby collapseof a pre-existing volcano or volcanic terrain (see Figures #6e, #18, #19 and #20). Rapid eruption of magmaempties an undergroundcavity, into which the land surface collapses. cinder: an inflated volcanic fragment with a sponge-like texture. Innumerableholes are surroundedby thin films of glass andembedded crystals. Theterm cinder is usually usedfor dark-gray to black (silica-poor) fragmentsthat cannotbe broken by hand. Pumiceis used for lighter-colored (silica-rich) fragmentswith similar sponge-liketextures, that can be brokenby hand. cinder cone: these small volcanoes are conical piles of cinder that accumulatearounda vent as particles fall from an eruption cloud (see Figure #6b). 23 cote: the central portion of the earth, madeof metallic iron. It beginsbeneatl"the silicate mantle at a depthof 2,885kilometers~ 1,791miles) below the surface. Theouter core is liquid andextendsto 5,145 kilometers (3,195 miles). There the solid iron inner core beginsandreachesto the center of the earth at 6,370kilometers. crater: a circular to ovaloshal:eddepressionat a volcano, generally less than 1 kilometer (.621 miles) across. Craters form aroundan eruptive vent by accumulationof material or by explosive removalof material. crust:the outermostlayer of the earth, lying above the mantle. Continental crust can reach 70 kilometers (43.4 miles)thick. Oceanic crust is upto 10kilometers(6.2 miles) thick. R~x:ksof the crust are less densethan those of the mantle, andthus the crust "floats" onthe solid mantle. density: a physicalpropertyof a matedalthat indicates its massper unit volume.Imaginea cube, 1 centimeter(25/64inches)or~ a side. If filled with water, it wouldweigh 1 grambecausewater has a density of 1 gram(.036 ounces)per cubic centimeter (25/64 inches). If you saweda rock into a cube the samesize it wouldweighabout 2.7 grams(.09 ounces), becausemost common rocks have densities of about 2.7 grams(.09 ounces)per cubic centimeter. dormant:sleeping; a dormantvolcanois one that is not presentlyeruptingbut is considered likely to doso in the future. eruptiveunit: the deposits left by a single eruption. Geologistsmapthesein the field anddistinguish oneunit from another. flood basalt plateau: gigantic flows of fluid, nonviscous lava erupt from swarmsof fissures and spread over vast areas. Repeatederuptions over geologically short periods of time build up thick lave plateauswith very gentle slopes (see Figure ~3f). forecast: an eruption forecast is a statement aboutfuture eruptiveactivity that is less specific than an eruption prediction. Typically forecastsare basedon recordsof past eruptive activity andconcern events that are months to decadesin the future. As volcanologists continue their reseamh efforts, eruption forecasts maybecome increasingly specific andevolveinto predictions. geophysicist: a scientist whoapplies principles of physics to geological problems. Geophysicists measureearthquake waves, gravity, magnetics, andelectrical currents, among other parameters. geothermal: refers to earth’s inner heat. Geothermal areas are usually located in regions of young volcanoes, where heat from cooling magmas can easily reachthe surface. glass:natural volcanicglassis the liquid part of a magma(molten rock) that has been quickly "frozen" (cooled and solidified). If magmas cool more slowly, they have time to grow crystals insteadof formingglass. harmonic tremor: a continuous, rhythmic type of earthquake wave caused by magmamovement underground. Harmonictremor can be an important warningsign of an eruption in the nearfuture. hotspot: a relatively stationary plumeof hot solid rock that rises fromdeepin the earth. Partial melting abovehot spots builds volcanoes, which are carried awayby the movingtectonic plates at earth’s surface. This conveyor-beltprocessforms linear volcanic chains called "hot-spot chains" (see Figure #2). lava: magma that erupts non-explosivelyand flows as a liquid. Rocksformedwhenthe flowing liquid solidifies are also called lave. Consultthis glossaryfor definitions of different lavetypes:aa, block, pillow, and pahoehoe. lava dome:a thick moundof viscous, gas-poor lave that piles up arounda vent like toothpaste squeezedfrom a tube (see Figure #6a). magma: molten rock below ground. It consists of crystals and gas bubbles suspendedin a liquid portion. mantle:the silicate portion of the earth that lies betweenthe crust and the core. 24 monitoring: to observe and measuresomething that changesover time. mudflow:a densemixture of water and rock fragments that flows rapidly downstream channels with the consistency of wet concrete. The enormousenergy of mudflowscan carry themtens of kilometersacrossflat landsat the foot of a volcano before they cometo rest. Theseare very destructive phenomena that can crush bridges and bury towns. pahoehoe lava: (pa-HOY-hoy) a type of fluid, nonviscous lava with a smoothto twisted, ropey surface. As the fluid lava oozesdownhill, its skin cools, solidifies, andwrinkles,while its molteninterior continuesmoving;(see Figure#12). pillow lava: a type o lava that resemblesa stack of pillows. Thesepillows develop whenhot magma erupts into cold wat~=r and oozes forward as a series of bulbous masseswhosecrusts immediately freeze to glass ~seeFigure #11). plagioclase:a silicat.,= materialcontainingsodium, calcium, and aluminum. plate tectonics: see tectonic plate andFigure #2. prediction: an eruption prediction is a detailed statementabouteruptiveactivity in the nearfuture, just hours to a few weeksaway. A prediction shouldspecifythe tirre of the eruption,the location of the eruptive vent 3n the volcano, the eruption style (explosive or rlon-explosive), andits size. Less precise statements about future eruptive activity are called for~,asts. pumice:an inflate(I volcanic fragment with sponge-like texture. Innumerableholes are surroiJndedby thin films of glass andembedded crystals. The term pumiceis usually used for whitegray fragments(silica-rich) that can be broken hand.Cinder is usedfor darker, moresturdy fragments(silica-poor) with similar sponge-liketextures. pyroclast: greek for "fire broken." Describesa fragmentof any size producedby an explosive volcanic eruption, including ash, andpumiceas well as larger blocks and bombs. pyroclastic fall: exp!osivevolcanic eruptionsgenerate clouds of hot gas, ash, and pumice. This term describesthe p-ocessof thesesolid particles. falling to the ground,wherethey form"pyroclasticfall deposits" of put, ice or ash with a restricted rangeof particle siz~.s (see Figure#8). pyroclastic flow: in someexplosive eruptions, hot clouds of gas, ash, and pumiceflow along the groundat high veloc ties like an avalanche.These are amongthe most destructive volcanic phenomena. Whenthese c ouds cometo rest they produce"pyroclastic-flow deposits", chaotic mixtures of ash, pumice, and rock with a wide rangeof particle sizes (see Figure #10). seismograph:an instrument that records earthquakewaves.Motionof the groundis detected by a seismometer,either attached to the seismograph or far away. The earthquakewavesare recorded as a set of wiggly lines on paperor on a computer screen. seismometer: an instrument that detects ground motions caused by earthquakes. Modern seismometers detect motionsin three separatedirections, onevertical andtwohorizontal. shield volcano: broad, gently sloped volcanoesnamed for their resemblance to a warrior’s shield are formedby repeated eruptions of very fluid, non-viscouslava, whichcan flow far from the vent (see Figure #6d). silica: the chemical componentsilicon dioxide (SiO2) is the major componentof most volcanic rocks on earth, ranging from less than 40 percent by weight to morethan 75 pementby weight. The amountof silica in a volcanic rock is one of the parametersused in assigning it a name,such as basalt or andesite. spreading ridge: mountain ranges on the sea fk:xx whereearth’s tectonic plates are spreading apart and growingby symmetricaladditions of new igneousrocks on both sides. It is estimatedthat 75 percent of the magma that reachesearth’s surface erupts at spreadingridges (see Figure #2). stratosphere: the secondlowest portion of earth’s atmosphere.At the baseof the atmosphere is the troposphere, whereall weathertakes place. The tropospherevaries in thicknesswith latitude, from - 9 kilometersnearthe po~esto 16 kilometers(9.9 miles) at the equator.Aboveit is the stratosphere, a regionof dry, thin, cold, clear air that is 32 kilometers (19.8 miles) thick. The stratosphere includes earth’s ozonelayer, at 19-48kilometers (11.8-29.8 miles). The ozone layer blocks the sun’s ultraviolet rays, whichwouldotherwisemake life on our planet impossible. strato volcano: steep-sided conical volcanoes that grow from the repeated eruption of viscous. magma.Explosive eruptions of gas-rich magmas produce layers of pumiceand ash. Eruptions of gas-poor magmas send out short, thick flows of block lava. Oneafter another these two processes build the cone(see Figure #6c). 25 subductionzone: an arcuat~ zone on Earth’s surface whereone tectonic plat,~ descendsbeneath anotherandis resorbedinto tte mantle. Theseare sites of abundantlarge earth ~uakesandbelts of explosive volcanoes(see Figu-e #2). tectonic plate: oneof the apl: roximately20 independentlymovingsegments of earth’s outer shell. Theyinclude the crust andthe upperrigid portion of the mantle. Thesetwo lay~,rs form the lithosphere, or "rocky sphere" (see F gure #2) and have a thickness of 100-200kiiomet~,rs (62-124miles). Tectonic plates are formedat ~~ceanicspreading ridges and consumed at subdu(,tion zones. They moveatop a flowing layer of .,;olid mantlerock belowcelled the asthenosphere see Figure #2). tiltmeter: an instrument that can detect tiny changesin the slope of the ground. With a networkof tiltmeters installed arounc’a volcano,geophysicistscanmonitorinflation an,~deflation of the cone. Such motions can be ass,)ciated with the movementof magmaundergrounc. vent: a crater or fissure at the earth’s surface through which magma,steam, and old rock fragmentscan erupt. viscosity: a physical property of licuids that measureshowrigid they are. Waterha:~low viscosity, whereashot tar is very viscous. Ma~mas similarly showa rangeof viscosities that affect the waythey erupt. volatiles: gaseouschemical components,such as steam,carbondioxide, hydrogensul=ide, and sulfur dioxide. Thesecan dissolve in rr olten silicate liquids underhigh pressure, but at low pressure they convert to gas. Rapid expansionof this gas drives explosiveeruptions. volcanic-hazards map: a map that indicates areasthat are likely to be affectedby variousvolcanic events (lava flows, pyroclastic llows, pyroclastic falls, mudflows,etc.) during f~iture eruptions. volcanologist: a scientist whostudies ,’olcanoes, volcanic rocks, or volcanic processes. volume:Here this term refers to the quantity of magma erupted, measuredin units of cubic kilometers(kin 3) (.239 miles3): a gigantic c:Jl:~ easuring 1 kilometer (.621 miles) on a si~e. THE SMITHSONIAN INSTITUTION The SmithsonianInstitution is hometo morethan 141 million objects, ranging in size from insects and diamondsto locomotivesand spacecraft. It is the world’s largest museumcomplex, comprising 15 museumsand galleries and the National Zooin WashingtonDC, and two additional museumsin NewYork City. Millions of visitors each year visit the nation’s capital to view such treasures as the Hope Diamond,the Star SpangledBanner,and the WrightFlyer. A broad range of exhibits ensures a fun and educational experience for Youngand old alike. Oneof the world’sleadingscientific researchcenters, the Institution has facilities in eight .states and the Republicof Panama.Researchprojects in the arts, history and science are carried out by the Smithsonian all over the world. Someof the Smithsonian’sresearch centers include the Srnithsonian Astrophysical ObserVatory in Cambridge,Massachusetts, the Smithsotlian MarineStation at Link Port, in Florida, and the SmithsonianTropical ResearchInstitute, in Panama. For membership informationof pre-visit planningmaterial, write or call the Visitor Informationand Associates ReceptionCenter, SmithsonianInstitution, Washington, D. C., 20560, (202) 357-2700(voice), (202) 357-1729(TTY). Youmayalso the Smithsonianthrough our website, www.si.edu. HISTORY JamesSmithson(I765 -1829), a British scientist, drewup his will in 1826nam)~g his nephew, Henry JamesHungefford, as bene~ciary. Smithsonstipulated that, should the ~ephewdie without heirs (as he did in 1835), the estate wouldgo to the United States to found "at Washington, under the name of the Sr~ithsonian Institution, an establishmentfor the increase and diffusion of knowledge...’, OnJuly 1, 1836, Congressaccepted the legacy bequeathed to the nation by James Smithson,and pledgedthe faith of the UnitedStates to the charitable trust. In 1838, fOllowingapprovalof the bequest by the British courts, the UnitedStates received Smithson’s estate--bags of goMsovereigns--then the equivalent of $515,169. Eight years later, on August10, 1846, an Act of Congresssigned by President James K. Polk, established the SmithsonianInstitution in its present formand Providedfor the administration of the trust, independentof the governmentitselE by a Board Regentsnnd Secretary of the Smithsoni~n.
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