DOCUMENT RESUME

ED 425 913 SE 061 906

TITLE Volcanoes! Teaching Guide.INSTITUTION Geological Survey (Dept. of Interior), Reston, VA.PUB DATE 1998-00-00NOTE 70p.; Very large wall poster not included with ERIC copy.PUB TYPE Guides Classroom Teacher (052)EDRS PRICE MF01/PC03 Plus Postage.DESCRIPTORS *Earth Science; Educational Resources; Elementary Secondary

Education; General Science; Interdisciplinary Approach;Language Arts; Lesson Plans; Mathematics; *ScienceActivities; *Science Curriculum; Science Instruction; SocialStudies; *Volcanoes

IDENTIFIERS National Science Education Standards

ABSTRACTThis document is an interdisciplinary set of materials for

grades 4 through 8 that reflects the goals of the National Science EducationStandards developed by the National Research Council (NRC). The activities inthis packet incorporate a number of related subjects including othersciences, social studies, language arts, and mathematics. Contains atwo-sided poster, teaching guide, six lesson plans with timed activities, andan evaluation sheet. Lesson topics include the lithosphere, atmosphere,biosphere, hydrosphere, and cryosphere. (DDR)

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Reproductions supplied by EDRS are the best that can be madefrom the original document.

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U.S. Department of the InteriorU.S. Geological Survey

fig.

The Earth's Systems

e

111

U.S. DEPARTMENT OF EDUCATIONOffice of Educational Research and Improvement

EDUCATIONAL RESOURCES INFORMATIONCENTER (ERIC)

O This document has been reproduced asreceived from the person or organizationoriginating It.

O Minor changes have been made toimprove reproduction quality

Points of view or opinions stated in thisdocument do not necessarily represent

- official OERI position or policy

The Earth is a system comprising interactive components.

Volcanoes is an interdisciplinary set ofmaterials for grades 4-8. Through thestory of the 1980 eruption of Mount St.Helens. students will answer fundamentalquestions about volcanoes: "What is avolcano?" "Where do volcanoes occurand why?" "What are the effects of vol-canoes on the Earth system?" "What arcthe risks and the benefits of living nearvolcanoes?" "Can scientists forecast vol-canic eruptions?"

This teachine packet reflects the goalsof the National Science EducationStandards developed by the NationalResearch Council. These standards rec-

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2

ommend that middle school students beable to understand the Earth as a system.By learninu about volcanoes, studentswill understand that the Earth comprisesinteracting components. or subsystems:the geosphere and the biosphere. In turnthe geosphere comprises the lithosphere,the atmosphere, the hydrosphere. and thecryosphere. (fig. I) These lessons showhow the eruption of Mount St. Helensaffected all of the Earth's subsystems.

Althouuh volcanoes is an earth sci-ence subject, the activities in this packetincorporate a number of related subjects.including other sciences. social studies,

language arts, and mathematics.

Contents of this packetTwo-sided color posterTeaching guide (with glossary andbibliography)Six lesson plans with timed activitiesEvaluation sheet

About the posterThe poster is a key visual aid for manv ofthe activities. Side 1 is a dramatic photo-graph of Mount St. Helens erupting onMay 18, 1980. Side 2 is a series of pho-tographs and illustrations annotated withtext written for student readers. The sec-tion titled "Volcanoes" is a basic intro-duction to volcanoes and volcaniceruptions. The section titled "Mount St.Helens" tells the story of the May 18.1980, eruption of Mount St. Helens andthe effect the eruption had on each of thecomponents of the Earth system.

Each photograph and diauram has anumber. When lessons refer to specificphotographs and illustrations, they arereferenced as "poster fig:' followed by thenumber of the photograph or diagram.

About the lessonsEach lesson includes:

Illustrated background informationTwo step-by-step. timed activitiesReproducible Master Sheets for mak-ing overhead transparencies or plimo-copiesReproducible Activity Sheets for yourstudents

2 BEST COPY AVAiLko.L

There are six lessons. Lesson 1 andLesson 2 should be taught in sequence.Lesson 6 is probably best suited as awrap-up. Many of the activities aredemonstrations that will help students,particularly elementary-level students,visualize the physical, chemical,geologic, and biologic processes beingpresented.

Lesson 1: Windows into the EarthThe lithosphere is the Earth's hard, out-ermost shell that is divided into a mosaicof 16 major slabs, or plates.

The first lesson introduces the natureof volcanoes and volcanic eruptions. Inaddressing how and where volcanoesoccur, students learn that volcanic erup-tions are geologic events that take placewithin the upper part and on the surfaceof the Earth's lithosphere.

Volcanic eruptions, however, canimpact all of the Earth's systems, includ-ing the lithosphere itself: Volcanic erup-tions create volcanic mountains. A keypoint is that understanding how andwhere volcanoes occur helps studentsunderstand the dynamic nature of theEarth's geologic processes.

Lesson 2: Creators and DestroyersThis lesson continues to explain how vol-canoes are related to the Earth's litho-sphere. With a basic understanding ofhow volcanoes erupt, students focus onthe May 18, 1980, eruption of Mount St.Helens. They see how changes to the vol-cano's shape in the month prior to theeruption reflected changes that were tak-ing place inside of the volcano. They alsolearn that volcanic eruptions can destroythe landforms they help create. The May18, 1980, eruption of Mount St. Helens isa dramatic example of both creation and

destruction.

Lesson 3: Up In the AirThe atmosphere is the mixture of gasesthat envelops the Earth.

This lesson explains how volcanoescan affect the atmosphere. Students learnthat volcanic eruptions affect places tento thousands of miles from an eruptionsite because of the ejection of volcanicrock fragments, gases, and aerosols into

the atmosphere. They also discover thatvolcanoes do not have to erupt to have aneffect on the atmosphere. The presence ofvolcanic mountains, such as the CascadeRange in the Pacific Northwest, continu-ally affect atmospheric conditions, andhence the climate, of the region.

Lesson 4: Fire, Water, and IceThe hydrosphere and cryosphere are thesubsystems that contain the Earth'swater The hydrosphere is the water onthe Earth's suiface contained in oceans,lakes, rivers, and streams, as well asground water that circulates within theupper part of the lithosphere. The cryo-sphere is water on the Earth's sulface inits frozen state, such as glaciers; snow;sea, lake, and river ice: and permafrost(permanently frozen ground).

This lesson explains how water fromthe hydrosphere and cryosphere can com-bine with volcanic materials from thelithosphere to produce catastrophicmudflows and floods. Students see therelationship between where mudflowsand floods are likely to occur and a vol-cano's topography. They also discoverwhy snow and ice cap many volcanicmountains and that the potential meltingof ice and snow adds to the volcanic haz-ards on these mountains.

Lesson 5: Death and RecoveryThe biosphere is the realm of all livingthings, including humans.

This lesson addresses the effect vol-canic eruptions can have on the bio-spherethe realm of all living things.Students learn that while the eruption ofMount St. Helens claimed about 60human lives, the toll on wildlife andplants was incalculable. By interpreting aset of tree rings, students discover that avolcanic eruption can have positive aswell as negative effects on plant growth.Finally, students examine the role thateyewitness accounts played in helpingscientists reconstruct the events of theMay 18. 1980. eruption of Mount St.Helens. reinforcing the importance offirst-hand observation as a scientific toolof investigation.

Lesson 6: Living with VolcanoesThe final lesson addresses the fact thatvolcanic eruptions can occur in populatedareas. Students discover that people whohave lived with volcanoes have attemptedto understand the volcano's presence andbehaviorusing legends and folklore formost of human history. Students see how,today, scientists reconstruct the history ofa volcano's eruptions to understand thepotential hazards of future eruptions.Students conclude the lesson by creatingmaterials that they could use to explainvolcanoes and their hazards to a commu-nity living near an active volcano.

A word about map skillsMany of the activities included in theselessons require basic map skills. Studentsshould know how to read simple maps,such as road maps. They also need tounderstand the following concepts:

Basic compass directions (north,south, east, and west)Using a map scale to determine dis-tance between two pointsUsing a map legend, or key, to inter-pret basic map symbolsLocating places on the basis of longi-tude and latitude

The U.S. Geological Survey's teach-ing packet What Do Maps Show? is anexcellent introduction to map reading forupper elementary and junior high schoolstudents. You may want to review itbefore teaching the topographic mapskills used in Lessons 2, 4, and 6.

To obtain copies of this packet andother USGS educational materials andpublications:

Call 1-800-USA-MAPS, or write orvisit a USGS Earth ScienceInformation Center.

Glossary

Active volcano: A volcano that is cur-rently erupting. or has erupted duringrecorded history.

Aerosol: Fine liquid or solid particlessuspended in the atmosphere. Aerosolsresulting from volcanic eruptions aretiny droplets of sulfuric acidsulfurdioxide that has picked up oxygen andwater.

Ash: Fragments less than 2 millimeters(about Vs inch) in diameter of lava orrock blasted into the air by volcanicexplosions.

Atmosphere: The mixture of gases,aerosols, solid particles, and watervapor that envelops the Earth.

Biosphere: The realm of all living things.Crater: The circular depression contain-

ing a volcanic vent.Cinder cone: A steep-sided volcano

formed by the explosive eruption ofcinders that form around a vent.Cinders are lava fragments about 1centimeter (about V2 inch) in diameter.

Crust: The Earth's outermost layer.Contour lines: Parallel lines used on

topographic maps to show the shapeand elevation of the land. They con-nect points of equal elevation.

Cryosphere: The ice and snow on theEarth's surface, such as glaciers; sea,lake, and river ice; snow; and per-mafrost.

Dome: A steep-sided mound that formswhen very viscous lava is extrudedfrom a volcanic vent.

Dormant volcano: An active volcano thatis in repose (quiescence) but is expect-ed to erupt in the future.

Extinct volcano: A volcano that is notexpected to erupt again.

Geosphere: The nonliving parts of theEarth: the lithosphere, the atmosphere,the cryosphere, and the hydrosphere.

Glacier: A thick mass of ice resultingfrom compacted snow that forms whenmore snow accumulates than meltsannually.

Harmonic tremor: Continuous rhythmicearthquakes in the Earth's upper litho-sphere that can be detected by seismo-graphs. Harmonic tremors often pre-cede or accompany volcanic eruptions.

Hot spot: An area in the middle of alithospheric plate where magma rises

from the mantle and erupts at theEarth's surface. Volcanoes sometimesoccur above a hot spot.

Hydrosphere: The water that covers 71percent of the Earth's surface as oceans.lakes, rivers, and streams. The hydro-sphere also includes ground water, waterthat circulates below the Earth's surfacein the upper part of the lithosphere.

Lateral blast: A sideways-directed explo-sion from the side or summit of a vol-cano.

Lava: The term used for magma once ithas erupted onto the Earth's surface.

Leeward: The side of a land mass shel-tered from the windthe opposite ofwindward.

Lithosphere: The Earth's hard, outermostshell. It comprises the crust and theupper part of the mantle and is dividedinto a mosaic of 16 major slabs, orplates.

Lithospheric plates: A series of rigidslabs (16 major ones at present) thatmake up the Earth's outer shell. Theseplates float on top of a softer, moreplastic layer in the Earth's mantle.(Also called tectonic plates.)

Magma: Molten rock containing liquids,crystals, and dissolved gases thatforms within the upper part of theEarth's mantle and crust. When erupt-ed onto the Earth's surface, it is calledlava.

Mantle: A zone in the Earth's interiorbetween the crust and the core that is2,900 kilometers (1,740 miles) thick.(The lithosphere is composed of thetopmost 65-70 kilometers (39-42miles) of the mantle and the crust.)

Mudflow: A flowing mixture of waterand debris (intermediate between avolcanic avalanche and a water flood)that forms on the slopes of a volcano.Sometimes called a debris flow orlahar, a term from Indonesia wherevolcanic mudflows are a major hazard.

Permafrost: Permanently frozen groundat high latitude and high elevation.

Prevailing winds: The direction fromwhich winds most frequently blow at aspecific geographic location.

Seismograph: A scientific instrumentthat detects and records vibrations(seismic waves) produced by earth-quakes.

Shield volcano: A volcano that resem-bles an inverted warrior's shield. It haslong gentle slopes produced by multi-ple eruptions of fluid lava flows.

Snowline: The lowest elevation at whichsnow remains from year to year anddoes not melt during the summer.

Spreading ridges: Places on the oceanfloor where lithospheric plates separateand magma erupts. About 80 percentof the Earth's volcanic activity occurson the ocean floor.

Stratovolcano: A steep-sided volcanobuilt by lava flows and tephra deposits.(Also called composite volcano.)

Subduction zone: The place where twolithospheric plates come together. oneriding over the other. Most volcanoeson land occur parallel to and inlandfrom the boundary between the twoplates.

Tephra: Solid material of all sizes explo-sively ejected from a volcano into theatmosphere.

Topographic map: A map that uses con-tour lines to represent the three-dimen-sional features of a landscape on atwo-dimensional surface.

Tree rings: Concentric rings formedannually as a tree grows.

Vent: The opening at the Earth's surfacethrough which volcanic materials(lava, tephra, and gases) erupt. Ventscan be at a volcano's summit or on itsslopes; they can be circular (craters) orlinear (fissures).

Viscosity: Measure of the fluidity of asubstance. Taffy and molasses are veryviscous; water has low viscosity.

Volcano: A vent (o.pening) in the Earth'ssurface through which magma erupts;it is also the landform that is construct-ed by the eruptive material.

Volcanic avalanche: A large, chaoticmass of soil, rock, and volcanic debrismoving swiftly down the slopes of avolcano. Volcanic avalanches can alsooccur without an eruption as a result ofan earthquake; heavy rainfall; or unsta-ble soil, rock, and volcanic debris.(Also called debris avalanche.)

Windward: The side of a land mass fac-ing the direction from which the windis blowingthe opposite of leeward.

Bibliography

Print Publications*indicates juvenile books

Brantley, S.R. Volcanoes of the UnitedStates. Reston, Va.: U.S. GeologicalSurvey general-interest publication,1994.

Crandell, D.W. and Nichols, D.R.Volcanic Hazards at Mount Shasta,California. Reston, Va.: U.S. GeologicalSurvey, 1987.

Decker. R. and Decker. B. Mountainsof Fire: The Nature of Volcanoes. NewYork: Cambridge University Press, 1991.

Decker, R. and Decker, B. Volcanoes.New York: W. H. Freeman and Co., 1989

Findley, R. "Eruption of Mount St.Helens," National Geographic.Washington D.C.: NationalGeographic Society, January 1981.

Foxworthy, B.L. and Hill, M. VolcanicEruptions of 1980 at Mount St. Helens:The First 100 Days. Reston, Va.: U.S.Geological Survey Professional Paper1249, 1982.

Grove, N. "Volcanoes: Crucibles ofCreation," National Geographic.Washington, D.C.: National GeographicSociety, December 1992.

Hays, W.W. ed. Facing Geologic undHydrologic Hazards: Earth ScienceConsiderations. Reston. Va.: U.S.Geological Survey Professional Paper1240-B, 1981.

Lauber, P. Volcano: The Eruption andHealing of Mount St. Helens. New York:Bradbury Press, 1986. *

Mannes, J. "Volcanoes," KidsDiscover. New York: Kids Discover.June/July 1993.*

Our Violent Earth. Washington, D.C.:National Geographic Society, 1982.*

Simkin, T. and Siebert, L. Volcanoesof the World: A regional directory,gazetteer, and chronology of volcanismduring the last 10.000 _years. 2d edition.Tucson, Ariz.: Geoscience Press, Inc.,1994.

Tillin2, R.I. Eruptions of HawaiianVolcanoes: Past, Present. and Future.Reston, Va.: U.S. Geological Survey gen-eral-interest publication, 1987.

Tilling. R.I. Eruptions of Mount St.Helens: Past. Present, and Future.

Reston, Va: U.S. Geological Surveygeneral-interest publication, 1990.

Tilling, R.I. Monitoring ActiveVolcanoes. Reston, Va.: U.S. GeologicalSurvey general-interest publication,1987.

Tilling, R.I. Volcanoes. Reston, Va.:U.S. Geological Survey general-interestpublication, 1993.

This Dynamic Planet: World Map ofVolcanoes, Earthquakes, Impact Craters,and Plate Tectonics. Reston, Va.: U.S.Geological Survey map poster, 1994.

Volcano: in the series Planet Earth.Alexandria, Va.: Time-Life Books, 1982.

Wright, T.L. and Pierson, T.C. Livingwith Volcanoes: The U.S. GeologicalSurvey's Volcano Hazards Program.Reston, Va.: U.S. Geological SurveyCircular 1073, 1992.

Video TapesBorn of Fire. National Geographic

Society Video, 1983.Nature: The Volcano Watchers.

WNET and BBC-TV (PBS), 1987.Volcano. National Geographic Society

Video, 1989.Volcanoes: Understanding the

Hazards. Earth Science Video Library.The Story of America's Great

Volcanoes. Questar Video, Inc., 1992.

The U.S. Geological SurveyThe U.S. Geological Survey (USGS), US.Department of the Interim; provides theNation with reliable, impartial infbrma-timi to describe and understand theEarth.

This information is used to minimize lossof life and property from natural disas-ters; manage water biological, energy,and mineral resources; enhance and pro-tect the quality of life: and contribute towise economic and physical development

For ittfOrmation on these and other USGSproducts and services, call I-800-USA-MAPS, j'ax 703-648-5548, or e-mail:esicmail@usgs.gov.

Receive information from the EARTH-FAX fax-on-demmid system, which isavailable 24 hours a day at 703-648-4888.

The address for the USGS home page is<URL: littp://www.usgs.gov/>

The address for the USGS educationallearning web home page is<URL: Intp://wwwusgs.govleducationi>

AcknowledgmentsWe greatly appreciate the technical assis-tance provided by the following U.S.Geological Survey reviewers: Richard S.Williams, Jr. Research Geologist, WoodsHole, Mass.: Steven R. Brantley, PublicInformation Scientist, Cascades VolcanoObservatory, Vancouver, Wash.; and JointH. Witnnann, Cartographer Michael P.Ryan. Research Geologist, and MarionM. Fisher Hydrologist, Reston, Va.

U.S. Department of the InteriorU.S. Geological Survey

fig. 1

Inside the Earth

Inner Core(solid)

Outer Core(liquid)

Mantle(solid)

Upper Mantle(soft)

Crust (hard)

Magma is generated in the Earth's lithosphere, which is made up of the crustand upper mantle.

Until the spring of 1980, most peoplethought of Mount St. Helens as a serene,snow-capped mountain and not as alethal volcano. The mountain had givenlittle evidence that it posed a hazard formore than a centurya long time inhuman terms but a blink of an eye interms of the mountain's 40,000-year geo-logic history. A series of earthquakesthat began in mid-March of 1980 sound-ed the alarm that Mount St. Helenswas awakening from its sleep. In otherwords, Mount St. Helens, which had

been dormant, became active and likelyto erupt. Its catastrophic eruption 2months later was a reminder that a fieryworld lies beneath the Earth's surface.

Why Volcanoes OccurThe roots of Mount St. Helens are 110 to330 kilometers (70 to 200 miles) belowthe Earth's surface. Here in the Earth'smantle (fig. /) temperatures are hotenough to melt rock and form a thick,flowing substance called magma. Lighterthan the solid rock that surrounds it,

LESSON 1

magma is buoyant much like a cork inwater; being buoyant, it rises.

As the magma rises, some of it col-lects in large reservoirs, or magma cham-bers (poster fig. 1) that fuel volcanoes. Asthe rising magma nears the Earth's sur-face, pressure decreases, which causesthe gases in the magma to expand. Thisexpansion propels the magma throughopenings in the Earth's surface: a vol-canic eruption occurs. Once magma iserupted, it is called lava.

Where Volcanoes OccurVolcanic eruptions occur only in certainplaces and do not occur randomly. That'sbecause the Earth's outermost shellthe lithosphereis broken into a seriesof slabs known as lithospheric ortectonic plates. These plates are rigid, butthey float on the hotter, softer layer inthe Earth's mantle. (poster fig. 2) As theplates move about, they spread apart,collide, or slide past each other.Volcanoes occur most frequently at plateboundaries.

Some volcanoes, like those that formthe Hawaiian Islands, occur in the interi-or of plates at areas called hot spots.(poster fig. 2) Although most of theactive volcanoes we see on land occurwhere plates collide, the greatest numberof the Earth's volcanoes are hidden fromview, occurring on the ocean floor alongspreading ridges.

Mount St. Helens is typical of morethan 80 percent of the volcanoes thathave formed on land. Known as subduc-tion zone volcanoes, they occur along theedges of continents where one plate

fig. 2

Inside the Earth

Mount St. Helens

GD@@)646@ CD@®ez:a)

North Ameriean Plate

Magma

About 240 kilometers (150 miles) west of the northwest coast of the United States, the Juan de Fuca Plate plunges beneaththe North American Plate. Mount St. Helens is among the volcanoes that have formed as a result.

dives, or subducts, beneath a secondplate. (fig. 2). When the subducting platereaches about 100 kilometers (60 miles)into the Earth's hot mantle, it triggerspartial melting of the overlying plate andforms new magma. Some of the magmarises and erupts as volcanoes.

Why Some Volcanoes EruptSome volcanoes, like Mount St. Helens,tend to be explosive when they erupt,whereas others, like Hawaii's Kilauea,tend to be effusive (loosely flowing) andnonexplosive. How explosive an eruptionis depends on the magma's chemicalcomposition and gas content, which inturn affect the magma's stickiness, or vis-cosity.

All magma contains gases that escapeas the magma travels to the Earth's sur-face. If magma is fluid (as is Kilauea's),gases can escape relatively rapidly. As aresult, lava flows instead of explodingduring an eruption. If magma is viscous

(as is Mount St. Helens), the gases can-not escape easily; pressure builds insidethe magma until the gases sometimesescape violently.

In an explosive eruption, the suddenexpansion of gases blasts magma into air-borne fragments called tephra, which canrange in size from fine particles of ash togiant boulders. After the initial explosivephase of the eruption, however, quieterlava flows can follow. In both explosiveand nonexplosive (effusive) eruptions,volcanic gases, including water vapor, arereleased into the atmosphere.

Three Types of VolcanoesRepeated volcanic eruptions build vol-canic mountains of three basic types, orshapes, depending on the nature of thematerials deposited by the eruption.

Shield volcanoes (poster fig. 5), suchas Kilauea, form by effusive eruptions offluid lava. Lava flow upon lava flowslowly builds a broad, gently sloping vol-

7

canic shape that resembles a warrior'sshield.

Stratovolcanoes (poster fig.3), such asMount St. Helens, build from both explo-sive and effusive eruptions. Layers oftephra alternating with layers of viscouslava flows create steep-sided, often sym-metrical cones that we think of as theclassic volcano shape. In his log of theLewis and Clark Expedition, WilliamClark wrote: "Mount St. Helens is per-haps the greatest pinnacle in America."

The smallest volcanoes, cinder cones(poster fig. 4), such as Sunset Crater inArizona, form primarily from explosiveeruptions of lava. Blown violently intothe air, the erupting lava breaks apartinto fragments called cinders. Thefallen cinders accumulate into a conearound the volcano's central vent. Cindercones can form on the flanks of shieldand stratovolcanoes.

Activity 1 Mins RD CM02

45-minute work session45-minute demonstrationand discussionIn small groups, students build modelsof the three major types of volcanoes andsee how a volcano's shape is related tothe type of material it erupts. As a class,they observe a demonstration that simu-lates the nature of two volcanic materials:lava and tephra. The lesson concludeswith a discussion of how a volcano'sshape is related to the nature of the mate-rial it erupts.

Key teaching points1. A volcano is a circular or linear open-ing in the Earth's surface through whichlava, rock fragments, ash, aerosols, andgases erupt.

2. A volcano is also the landform, often amountain, built from repeated eruptions.

3. Some eruptions are explosive, someare effusive (loosely flowing) and nonex-plosive, and some are both explosive andeffusive.

4. There are three major types, or shapes,of volcanoes: (a) stratovolcano, (b) shieldvolcano; and (b) cinder cone.

MaterialsWork Session

1. Master Sheets 1.1, 1.2, and 1.32. Colored marking pens (optional)3. Three 8 1/2" x 11" transparencies for

overhead projection4. Play-doh® in several colors5. Construction paper or cardboard, one

piece for each group of four students6. Pencils

Demonstration1. Three pie plates2. Three 1-cup measuring cups3. Cat litter4. Chilled molasses

Procedures1. Explain that the photograph on side 1of the poster was taken during the 1980eruption of Mount St. Helens, a volcanolocated in the western United States.

2. Introduce the concept that a volcanois both an opening in the Earth's surfacethrough which magma erupts and a land-form.

3. Discuss the types of materials that canbe erupted: lava, tephra, cinders.

4. Discuss the different styles of erup-tion: explosive and nonexplosive.

5. At this point, do not name the threemajor volcanic shapes.

6. Divide the class into groups of fourstudents each. Distribute to each group:

Master Sheets 1.1, 1.2, and 1.3Three pieces of cardboard or construc-tion paperPlay-doh®

7. Using the Master Sheets as guides,each group of students creates a two-dimensional relief model for each of thethree types of volcanoes. Master Sheet1.1 is a stratovolcano, Master Sheet 1.2is a cinder cone, and Master Sheet 1.3 isa shield volcano.

8. Ask each group of students to list thesimilarities and differences among theshapes and composition of the threetypes. (The shield is broad; the stratovol-cano has steep sides; the cinder cone isthe smallest; and the shield has only lay-ers of lava.)

Discussion1. On a chalkboard, compile a class listof similarities and differences for each ofthe three types.

2. Brainstorm why the volcanoes are dif-ferent. For example, lava is runny likemolasses so it spreads out.

Demonstration1. Do the following demonstration tosimulate the nature of lava and the natureof tephra. In one pie plate, slowly pour 1cup of cat litter (tephra). In a second pieplate, slowly pour 1 cup of chilledmolasses (lava).2. Discuss how the nature of the materi-al influenced the shape of the materialbuilt. Discuss what shape you would

8

expect to get if you alternated a layer ofcat litter with a layer of molasses. In thethird pie plate, layer molasses and catlitter.

3. Compare the results of your demon-stration with the shapes of the three typesof volcanoes (poster fig. 3-5 ). Ask stu-dent to "type" each of their models.

4. Show students side 1 of the poster.What type of volcano is Mount St.Helens? (stratovolcano) What type oferuptions does it have? (explosive) Whattype of material is in the cloud risingabove it ? (tephra)

Activity 2 -ERE ce HT@

30 minutesStudents locate some of the 1,500 activevolcanoes on a world map. Then by com-paring their maps with a map of theworld's tectonic plates, they discover thatvolcanoes occur because of the dynamicnature of the Earth's lithospherethecrust and upper mantle.

Key teaching points1. Volcanoes are windows into how theEarth works. They occur because theEarth's rigid outer shell, the crust andupper mantle, is broken into a mosaic ofplates that are in constant motion.

2. Most volcanoes occur along theboundaries of the Earth's tectonic plates.

3. More than half of the volcanoes thatare exposed on land form a chain alongthe converging plates that encircle thePacific Ocean. This chain is called the"Ring of Fire."

4. Mount St. Helens is located in the"Ring of Fire."

Materials1. A photocopy of Activity Sheets 1.2

and 1.2b for each student2. Master Sheets 1.4 and 1.53. Two 8 1/2" x 11" transparencies for

overhead projection4. Colored pencils

ProceduresPreparation

1. Make transparencies of Master Sheets1.4-1.5.

2. Distribute Activity Sheets 1.2a-1.2band ask each student to read theActivity Sheets.

Discussion1. After the students have completedtheir maps, lead a discussion. Are therevolcanoes on every continent? (yes) Howmany of the volcanoes on their map arelocated within the shaded area, "TheRing of Fire?" (14)

2. Show the class the transparency ofMaster Sheet 1.5, the "Plate TectonicsMap." With a colored marker, trace the

plate outlines. Tell students that the outerlayer of the Earth is broken into a seriesof 16 major plates and that the coloredlines indicate the boundaries betweenthese plates.

3. Next, superimpose the transparency ofMaster Sheet 1.4, "Volcanoes Map," onMaster Sheet 1.5, the "Plate TectonicsMap."

4. Ask students to observe the locationof the volcanoes in relationship to theplates. Where do most of the volcanoesoccur? They should observe that mostoccur near plate boundaries. Is the "Ringof Fire" located near plate boundaries?

5. Use (poster fig. 2) to explain that rigidplates float on top of a softer layer ofrock. As the plates move, they pushtogether, pull apart, or slide past eachother. Along two plate boundaries,magma comes to the surface and volca-noes can occur.

6. Explain that there are some volcanoesthat occur in the interior of plates and notat plate boundaries. They occur over "hotspots" in the plates. Scientists do notknow exactly why hot spots develop, buthot spots are places in the Earth's interiorfrom which magma rises and eruptsthrough the plate as it moves over the hotspot. Ask students which U.S. State iscomposed primarily of shield volcanoes?(Hawaii)

7. Is Mount St. Helens located in the"Ring of Fire"? (Yes)

9

Activity Sheet 2-

I . Yes

2. 66.6%3. 33.3%4. 14 stratovolcanoes: 1 shield:

8 cindercone5. Stratovolcano6. Answers will vary

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MThere are more than 1,500 active volcanoes in the world.An active volcano is one that has erupted at least once inthe past 10,000 years and is likely to erupt again. Becausemost of the Earth's volcanoes are hidden under the oceans,people have not been able to witness their eruptions. Every

Activity Sheet 1.2aThe "Ring of Fire"

year, about 50-60 volcanoes erupt on land where peoplemight be able to see them. Scientists estimate that thereare about 200 volcanic eruptions under the oceans.The shaded area on your map is called the "Ring ofFire." Do the exercise below and you will discover why.

What to do

Locate and label each of the volcanoes listed on the blankmap. Use a different colored marker for stratovolcano,shield, and cinder cone volcanoes.

1. Are most of the volcanoes located in the Ring of Fire?

2. What percentage of the volcanoes are located in theRing of Fire? To find out use the following formula:

# in shaded areaxtotal # 100 = % of volcanoes in the

Ring of Fire

3.What percentage of the volcanoes are located outside ofthe Ring of Fire? To find out use the following formula:

# not in shaded areax 100total # % outside of volcanoes

in the Ring of Fire

4.Types of volcanoes in the Ring of Fire

# of stratovolcanoes

# of shield volcanoes

# of cinder cones

5. What type of volcano is most common in the Ring ofFire?

6. How many of the volcanoes listed have erupted sinceyou were born?

This is a list of some active, or recently active, volcanoes.

Name Type Last Erupted

1 Azul Stratovolcano 19672 Bezymianmy Stratovolcano 19933 Cerro Negro Cinder cone 19714 Cotopaxi Stratovolcano 19425 Erebus Stratovolcano 19806 Katmai Stratovolcano 19127 Kilauea Shield 19958 Krakatau Stratovolcano 18949 Ksudach Shield 190710 La Palma Stratovolcano 195411 Lassen Peak Stratovolcano 191412 Mt. Etna Shield 199313 Mt. Fuji Stratovolcano 170914 Mt. Pelée Stratovolcano 193215 Mt. Rainier Stratovolcano 189416 Mount St. Helens Stratovolcano 198617 Nevada del Ruiz Stratovolcano 199118 OlDoinyo Lengai Stratovolcano 199319 Paricutin Cinder cone 195220 Pinatubo Stratovolcano 199221 Sunset Crater Cinder cone 106522 Surtsey Shield 196723 Tambora Stratovolcano 196724 Vesuvius Stratovolcano 1944

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U.S. Department of the InteriorU.S. Geological Survey

On May 18, 1980, Mount St. Helenserupted violently. At 8:32 a.m. PacificDaylight Time, a magnitude 5.1 earth-quake occurred about a mile beneath thevolcano, triggering a catastrophic seriesof events that transformed Mount St.Helens' picturesque mountain landscapeinto a gray wasteland.

The Catastrophic EruptionThe earthquake shook the walls of thevolcano's summit crater and triggeredmany small rock avalanches. Withinseconds, a huge slab of the volcano'snorth flank began to slide, and smalldark clouds billowed out of the base ofthe slide. Plumes of steam and ash alsorose from the volcano's crater. As theavalanche of rock and ice raced downthe mountain's north flank at more than250 kilometers per hour (155 miles perhour), a massive explosion blasted outof the north side of the volcano. Thislateral blast became a fearsome hurri-cane of ash and rock that outraced theavalanche. Probably no more than 20 to30 seconds had elapsed since the trig-gering earthquake!

The Eruption Was No SurpriseThe eruption of Mount St. Helens wasnot a surprise. For nearly 2 months, sci-entists had been monitoring changes atMount St. Helens. For a volcano toerupt, magma must move to the Earth'ssurface. Increased earthquake activity,eruptions of steam and ash, and changesin the shape of the surface of the vol-cano all signal that magma is on themove toward the surface.

Inside the volcano, the solid rock thatsurrounds the molten rock often cracksfrom the increased pressure and causesearthquakes. Between March 20 andMay 18, more than 10,000 earthquakeswere recorded beneath Mount St.Helens. The largest of these were felt bypeople living near the volcano. In addi-tion to recording the discrete jolts char-acteristic of earthquakes, seismographsalso detected continuous rhythmic vibra-tions called harmonic tremors. Thesenumerous small earthquakes were fur-ther evidence that magma was movingwithin the volcano.

As magma made room for itselfinside the volcano's cone, the surface ofthe volcano swelled, or inflated. Byearly April, Mount St. Helens' northflank began to visibly bulge and crack.The bulge grew 2 to 3 meters (7 to 9feet) a day and it moved outwards about150 meters (450 feet) in 2 months.

When the 5.1 magnitude earthquakeshook Mount St. Helens on May 18,1980, the bulge collapsed. The resultingavalanche was the largest volcanicavalanche recorded in historical times.In turn, the sudden removal of masses ofrock and ice by the avalanches triggeredan explosive eruption of steam trappedin cracks and voids in the volcano andof gases dissolved in the magma.Unleashed by the abrupt release of pres-sure, magma, rock, ash, aerosols, andgases exploded from within the vol-cano's north flank.

LESSON 2

The Mountain is TransformedIn a few minutes, Mount St. Helens'symmetrical cone was transformed. Itwas 400 meters (1,312 feet) shorter anda gaping crater was gouged into its northside. An avalanche of rock, ash, ice,water, and fallen trees flowed as far as 9kilometers (15 miles) down the valley ofthe North Fork Tout le River. Debrisdumped into Spirit Lake raised thelakebed by more than 940 meters (295feet). The lake's cool, crystal-clearwaters became a simmering black stewof rocks, mud, and floating trees. Gonewere 70 percent of the glaciers thathad crowned the volcano, melted by theheat of the eruption or carried awayby the fast-moving avalanche. Toweringforests with trees up to 45 meters (150feet) were flattened and strewn likematch sticks in the wake of the lateralblast and debris-laden avalanche.

Eruptions ContinueBetween May 18, 1980, and October1995, Mount St. Helens has had at least21 eruptions of magma and dozens ofsmaller gas explosions. All of thevolcanic activity has taken place in thebottom of the crater created by the May18, 1980, eruption. There Mount St.Helens is rebuilding itself. During eacheruption, new lava squeezes up andpushes aside old material from thesurface of the dome. The volcanic activ-ity that began in 1980 is not yet over.

Activity 1 cIo offinfan Nun E2

45 minutesBy observing two demonstrations,students will understand (1) why a bulgedeveloped on the north flank of MountSt. Helens and (2) why the avalanchetriggered an explosive eruption.

Key teaching points

1. The bulge that developed on the northflank of Mount St. Helens was evidenceof changes occurring inside the volcano.Magma was moving closer to the surfaceand inflating, or deforming, the side ofthe volcano.

2. Scientists had been closely monitoringthe growth of the bulge for nearly amonth to help them try to forecast aneruption.

3. The 5.1 magnitude earthquake on May18, 1980, shook the volcano, includingthe bulge area. In turn, the shaking of thebulge area caused a sudden collapse ofthe volcano's north flank and triggered alarge avalanche.

4. The removal of this large mass of rockby the avalanche caused a sudden releaseof pressure inside the volcano and a vio-lent eruption occurred.

Materials1. 1,500 ml beaker (Pyrex TM)2. Damp sand3. Several small balloons4. Rubber bands5. Bunsen burner or hot plate6. Straight pin7. A bottle of soda water8. Basin or bowl to catch the "explosion"9.. Master Sheet 2.1

ProceduresPreparation

Before class begins, put about 1/2 inch ofsand in the bottom of the beaker and levelthe surface of the sand. Partially inflate aballoon, secure it with a rubber band, andplace the balloon on top of the sand in thebeaker. Cover the balloon with sand to adepth of about 11/2 inches. Level the surfaceof the sand.

IntroductionIn class begin the lesson by reviewingthe series of events that occurred onMay 18, 1980. Use Master Sheet 2.1 todiscuss the following events: the bulgethat had been growing on the north sideof the volcano for a month, the 5.1 mag-nitude earthquake that triggered anavalanche, and the avalanche that un-leashed an explosive eruption, a lateralblast.

Demonstration 1:Why the bulge grew

1. Partially inflate a balloon. Ask stu-dents what would happen to the balloonif you were to heat the air in the balloon?(The balloon would expand because theair expanded.) Explain that inflationcaused a bulge to develop on the northflank (side) of Mount St. Helens.

2. Tell the students that the inflated bal-loon represents the magma rising withinMount St. Helens and that the sand repre-sents the surface of Mount St. Helens.(fig. I )

3. Show the beaker to the students andtell them you have a partially inflated bal-loon in the beaker. Place the beaker onthe Bunsen burner or the hot plate. Heatthe beaker until the balloon begins toexpand. (The surface of the sand shouldbegin to "bulge".) (fig. 2)

4. Observe the changes in the shape ofthe surface of the sand. What happens tothe "land" as the "magma chamber"expands?

Demonstration 2:Why the avalanche triggeredthe explosive eruption

1. Ask students what would happen ifyou were to stick a pin into the balloon.(It would pop or explode.) Why does itexplode? Burst the balloon. (The balloonbursts because the pressure inside theballoon is suddenly released and thegases can escape rapidly.)

2. Ask students what happens when theyopen a bottle of soda. (It goes "fizz"because the gas, CO2, in the soda

escapes.) Demonstrate this by shaking abottle of soda water and releasing thecap. (The soda water "erupts" out of thebottle.)

3. Return to the the poster (poster fig.1).Compare the soda bottle to a magmachamber. As long as the top is on the bot-tle, there is no eruption. Compare therock and ice that was unloaded by theavalanche to the soda cap. When the"cap" was suddenly removed, the pres-sure inside the volcano was suddenlyreleased, and the volcano erupted.

fig. I

fig. 2

24

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Activit 2 Elapping Mount St. Helens

30-minute demonstration45-minute work sessionStudents use topographic map skills tointerpret the impact of the May 18, 1980,eruption of Mount St. Helens on the vol-cano's topography.

This activity is divided into an intro-duction, a demonstration, and a stu-dent work session.

In the demonstration you (1) intro-duce students to topographic maps andcontour lines and (2) construct a simplethree-dimensional model of Mount St.Helens before the May 18, 1980, eruption.

In the work session, students drawprofile views of Mount St. Helens beforeand after the May 18, 1980, eruption.Students use these profiles to interpret thechanges in the mountain's topographythat were caused by the eruption.

Key teaching points1. Because volcanic eruptions both cre-ate and destroy landforms, they causechanges on the surface of the Earth'slithosphere. The May 18, 1980, eruptionof Mount St. Helens destroyed a signifi-cant portion of the mountain that hadbeen created by previous eruptions.

2. Within a few minutes of the start ofthe eruption, the mountain lost 400meters (1,312 feet) of its height and agaping crater 625 meters (2,050 feet)deep, 1.7 miles (2.7 kilometers) long, and1.3 miles (2 kilometers) wide opened onits once nearly symmetrical cone.

3. The changes to Mount St. Helens'landscape have been recorded on topo-graphic maps. Topographic maps repre-sent the three-dimensional features of alandscape on a two-dimensional surface.

Materials1. Master Sheet 2.22. Play-doh®3. Scissors4. Activity Sheet 2.1 (2 sheets)

ProceduresIntroduction

1. Begin this activity by showing theclass the photograph on the poster ofMount St. Helens taken before the 1980eruptions (poster fig. 10).

2. Remind students that Mount St. Helensbegan erupting about 40,000 years ago, butmost of its height formed over the past2,500 years from repeated eruptions. At thetime of the May 18, 1980 eruption it was2,780 meters (9,677 feet) high. Some erup-tions can destroy part of the mountain thatearlier eruptions have built.

3. Look at the photograph (poster fig. 11)taken after the May 18, 1980 eruption. Askstudents what they think the impact of theMay 18, 1980 eruption was on the shapeand size of Mount St. Helens.

4. Tell students that they will use topo-graphic maps of Mount St. Helens beforeand after the May 18, 1980 eruption to veri-fy or refute their observations.

5. Use a transparency of Master Sheet 2.2to explain that a topographic map showstopography the highs and lows of agiven area.

Topographic maps use special linescalled contour lines to show the shapeand elevation of the land.On this map, each contour line repre-sents 100 meters (330 feet) change inelevation.With your finger trace the "2,000"meters contour line.Tell students that if they were walkingon this imaginary line, they would never

go up or down. To walk up or walkdown, they would have to change linesmuch like walking up or down steps.

Demonstration:A profile model of Mount St. Helensbefore the 1980 eruption.

1. Make a transparency and 4 photo-copies of Master Sheet 2.2 (topographicmap of Mount St. Helens before the 1980eruptions).

2. Use the transparency to show studentsthe topographic map of Mount St. Helensbefore the 1980 eruptions.

3. Tell your students that you will use thistopographic map to " build" Mount St.Helens before the 1980 eruptions. (fig. 3)

4. Cut along the 1,400 meters contourline to make a pattern. Roll out Play-doh® about Ihinch thick and place thecutout on top of the Play-doh®. With asharp point, trace along the contour lineto form your first layer.

5. Cut along the 1,600 meters contourline to make a second pattern. Roll outPlay-Doh® about I/2inch thick, place thepattern on top of it, and trace along thecontour line to make your second layer.Stack layer 2 on top of layer 1, like build-ing a tiered wedding cake.

TOpographic maps use contour lines, which are imaginary lines that connectalrpoints at the same elevation. By reading these lines. you generally cantell: (1) the elevation of the land. (2) the steepness of a slope, and (3) theshape of the land.

Contour lines are always parallel. They never cross.

The closer together the contour lines, the steeper the slope.

Closed depressions, such as a volcanic crater, are marked with short linespointing downslope.

Every fifth contour line is made heavier and the elevation is alwaysmarked. (This makes contours easier to read and count.)

Activity 2 Cclinaal

fig. 3

Ac2ivity Sheet 2--J\3

Map A completed

1. Cone shape: mountain-like2. 2.800

Map B completed

6. Repeat this process for the 1,800,2,000, 2,200, 2,400, 2,600, and 2,800meters contour lines.

7. Give students an opportunity to lookat the model. Have them pay specialattention to the side view, or profile, as apreparation for their work session.

Work session: Drawing profile maps1. Hand out Activity Sheets 2.1. Map A isa topographic map of Mount St. Helensbefore the 1980 eruptions. Map B is a topo-graphic map of Mount St. Helens after theeruptions.

2. Following the directions on theirActivity Sheets, students use topographicmaps to draw a profile (side view) ofMount St. Helens before and after the 1980eruptions.

3. Students compare the completed pro-files to see how the eruption changed thesize and shape of Mount St. Helens.

IL As a class, calculate how many metersin elevation Mount St. Helens lost as aresult of the May 18, 1980, eruption. ( 400meters/1,312 feet) 26

5. Yes. Part is missing. ft is nolonger a cone.

6. About 2.400 meters7. Lower8. Bigger

Master Sheet 2.1

8:27:00 a.m.SUMMIT, JANUARY 1980

/2,950 m 9,677 ft

". CRATER

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AVALANCHEDEBRIS

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27

Master Sheet 2.2

Legend 0 1 km Contour interval 100 meters

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Glaciers ,M11, 11M Crater

BEST COPY AVAILABLE

These are topographic maps of Mount St. Helens.Map A is Mount St. Helens before the 1980 eruptions andMap B is Mount St. Helens after the May 18, 1980, erup-tion. Compare these maps and you will see how the erup-

, tion changed the size and shape of Mount St. Helens.

Activity Sheet 2.1Map AThe Mountain Blows its Top

What do Topographic Maps Show?

Topographic maps show the shape and elevation of theland by using special lines called contour lines. A contourline is an imaginary line that connects points at the sameelevation, or height. Elevation is how high, or low, the landis above sea level. Sea level is "0" meters. On these twomaps, each contour line equals a 100 meters (330 feet)change in elevation. To make the lines easier to read, every500 meters (1,550 feet) is shown in a heavy black line.

Map A: Before the Eruption

The top of this drawing is a topographic map of MountSt. Helens before the 1980 eruption. It shows the volcano'sshape and elevation as if you were looking at the volcanofrom the air. The bottom of this drawing is a profile view.It shows the volcano's shape and elevation from the side.

What to do1. On the bottom illustration, connect the dots.

What shape have you drawn?

2. Find the highest point on the bottom illustration, putan "X" there. To find the approximate elevation, traceyour finger across to the numbers on the left side.That number is about meters.

Glaciers Crater

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M oActivity Sheet 2.1Map BThe Mountain Blows its Top

Map B: After the Eruption

The top of this drawing is a topographic map of Mount St.Helens after the May 18, 1980, eruption. You will drawa profile view at the bottom to see how the shape andelevation of the volcano changed after the eruption.

What to do1 . Find the contour lines on the topographic map. Trace

your finger around the 2,000 meters contour line.

2. Draw a line between the letter "A" and the letter "B." Thisline cuts across the top of the volcano.

3. Starting from "A" trace across the line until you cross acontour line. At that point, draw a line down to the chartbelow until you find the same number. Put a *. Repeatuntil you get all the way across line A B. We havedone the first few for you.

4. Connect all the dots.

5. Has the shape of the volcano changed? How?

6. Find the highest point. How many meters high is thevolcano?

7. Is the volcano higher or lower than before the eruption?

8. Find the crater. Is it bigger or smaller than before theeruption?

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LESSON 3Comparison of Eruptions

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The volume of ash ejected during an eruption is one factor in measuring the size of an eruption. Note that the May 18 volume .

was less than several earlier eruptions of Mount St. Helens and considerably less than eruptions of other volcanoes.

In less than 10 minutes after the onset ofthe cataclysmic eruption of Mount St.Helens, a column of tephra, steam,aerosols, and gases reached an altitude of19 kilometers (12 miles). Although thelargest fragments of tephra fell back tothe ground close to the volcano, thesmallest fragments, ash and dust, werecarried eastward by the prevailing winds.Five days after the eruption, monitoringinstruments in New England detected ashfrom Mount St. Helens. Some of the asheventually circled the globe and thesmallest fragments and aerosols remainedsuspended for years in the stratosphere.

Day Becomes NightMoving at an average speed of 95 kilo-meters per hour (60 miles per hour), the

ash cloud reached Yakima, Wash., by9:45 a.m. Pacific Daylight Time andSpokane, Wash., about 2 hours later. InYakima, a city of 51,000, day becamenight. Automobile and street lightsremained on for the rest of the day as theeruption continued for more than 9 hours.Ash as fine as talcum powder cloggedengine air filters and choked peopleface masks or handkerchiefs were anecessity for those who ventured out ofdoors.

Ash blanketed the ground like snow,but snow that would not melt. Residentsshoveled and bulldozed ash from streets,sidewalks, and roofs; an estimated600,000 tons of ash were removed fromthe city. It took 10 weeks to haul it away!

31

Volcanic Ash's Deadly EffectsAsh fall, however, is more than an incon-venience. It can be lethal to plants,wildlife, and humans. Swirling particlesof ash in the atmosphere generated light-ning, which in turn ignited hundreds offorest fires near the volcano. Autopsiesrevealed that most of the human deaths inthe blast area resulted from asphyxiation,from inhaling hot volcanic ash during thefirst few minutes of the eruption.

As the ash settled to the ground, it alsotook its toll. Eastern Washington becameknown as the "ash belt" where manyfarm crops were destroyed in areas ofthick accumulation. Volcanic ash can alsoaffect aircraft operations. Jet engines aresusceptible to damage: the volcanic ashcoats and melts turbine blades, oftencausing the engines to stall.

fig. 2

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This map shows the distribution of ash fallout from the May 18, 1980, eruption.

Impact on ClimateVolcanic eruptions can also affect climateand weather patterns. Mount St. Helens'1980 eruptions did not have a significanteffect on global climate, but the 1982eruption of El Chichôn in Mexico, forexample, had measurable effects. ElChichOn's magma was much richer insulfur than Mount St. Helens'. As aresult, the Mexican volcano producedsulfuric acid aerosols (a fine mist of par-ticles) that formed a layer of haze in thestratosphere. This haze, which canremain in the atmosphere for years,reflects the sun's radiation and reducessurface temperatures. For example, morethan a year after the April 1815 eruptionof Indonesia's Tambora volcano, itseffects were felt. In the northeastern

United States, 1816 was so cold thatsnow fell in some New England States inJune and July. It was known in NewEngland as the "year without a summer."

How Much Ash Fell?In comparison to other historic eruptions,the volume of ash fall from the 1980eruption of Mount St. Helens was rela-tively small (fig. 1). The eruption ofTambora ejected 150 times more ash thanMount St. Helens in 1980. And ash eject-ed by Mount Mazama (now Crater Lake),located about 125 kilometers (200 miles)south of Mount St. Helens, was evengreater than Tambora. The 1980 eruptionof Mount St. Helens was only an inklingof the destructive potential of a volcaniceruption.

Activity 1linglAng mn Cliatik

15-minute demonstration45-minute work sessionStudents observe a demonstration of a"dust box" to help them understand thatsome volcanic ash (tephra) may be diffi-cult to see. In a work session, they willthen use the equation, D = RxT (distanceis equal to the rate of speed times thetime of travel) to calculate the time ittook volcanic ash erupted into the atmos-phere to travel to different parts of theUnited States following the May 18,1980, eruption of Mount St. Helens.

Key teaching points1. Explosive volcanoes can erupt largequantities of tephra, gases, and aerosolsinto the atmosphere.

2. The smallest of these particles are sus-pended in the atmosphere and are some-times carried by wind great distancesfrom the immediate site of an eruption.Some of these particles are too small tosee.

MaterialsDemonstration

1. Large cardboard box such as a photo-copy paper box

2. Black construction paper, dark clothbed sheet, or black spray paint

3. Glue, tape, or staples4. Scissors5. Pencil or pen6. Flashlight7. Two erasers with chalk dust

Work Session1. Activity Sheets 3.1ab2. Atlas3. Colored pens or pencils4. Calculators (optional)

ProceduresPreparation:Assembling the "dust box" (fig. 3)

1. Remove the flaps from one side of thebox.

2. Line the interior of the box with blackconstruction paper or a dark sheet, orspray paint it black.

fig. 3

"Bust Box"

3. On one side, cut a hole the same sizeas the lamp end of the flashlight.

IntroductionUse side 1 of the poster and point out thecolumn of ash rising above Mount St.Helens. Remind students that in Lesson 1they learned that explosive volcanoes likeMount St. Helens erupt rock and lavafragments, gases, and aerosols into theatmosphere. The rock fragments, whichare called tephra, can range in size fromcar-sized boulders to ash or dust that is sosmall it is invisible to the naked eye.

Demonstration1. With the lights on, beat two eraserstogether inside of the "dust box."

2. Ask students to raise their hands whenthey can no longer see any "dust" in theair. When the last student has raised hisor her hand, turn on the flashlight. Askstudents to put their hands down if theynow see dust.

Work Session

1. Discuss the photographs and captionsin the atmosphere section of the poster(poster figs. 12-14.). Remind students ofthe "dust box" demonstration. Like chalkdust, the smallest volcanic particles staysuspended in the atmosphere. Once in theatmosphere, they can be carried by windgreat distances from the volcano. (fig. 2)

2. Some of these particles are so smallthat they form invisible clouds, which areparticularly dangerous to airplanes thatunknowingly encounter volcanic ashclouds. Volcanic ash sucked into jetengines can cause the engines to stall, asthe following story illustrates:

Following the 1989 eruption of MountRedoubt in Alaska, a Boeing 747 air-craft lost power in all four of itsengines after flying into a volcanic ashcloud. Finally after losing 4,267meters (14,000 feet) in altitude thepilot was able to restart the engines.The airliner landed safely, but thedamage to the aircraft has been esti-mated to exceed $80 million. Becauseof the potential hazard posed by ashclouds to aircraft, air traffic con-trollers need to issue warnings toaircraft flying in the air space theymonitor

3. Tell the students that they are air traf-fic controllers. They have just receivedword that Mount St. Helens has had amajor eruption. They should stand by toreceive critical data so that they can cal-culate when airborne ash will reach theair space they monitor. Discuss with theclass the type of data they will need togather, such as

the time of the eruption,the wind direction,the rate of speed the airborne tephra istraveling, andhow far their city is located from theeruption.

4. Divide the class into teams of air traf-fic controllers for each of the followinglocations:

Great Falls, Mont.Rapid City, S. Dak.Madison, Wis.Minneapolis, Minn.Chicago, Ill.Detroit, Mich.Pittsburgh, Pa.Boston, Mass.

5. On their activity sheet, each team willuse the data to calculate the time the ashis expected to arrive in the air space theymonitor. (The ash cloud is moving at arate of 96 kilometers per hour.)

6. Distribute the Activity Sheets.

33

7. Before students begin, review with theclass the formula (D=RT). Demonstratehow to use the formula to calculate bothrate and time.

8. As a homework assignment, ask eachstudent to calculate the time it took the

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ash cloud to circle the Earth. The Earth is40,000 kilometers (20,500 miles) at theEquator.

AWN!! Shes2,QD-LsweCity KilometersGreat Falls 850Rapid City 1.450Madison 1500Minneapolis 2.100Chicago 2.700Detroit 3.050Pi us burgh 3.400Boston 3,900

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Activity 2

45 minutesBy recording the annual precipitation(rain and snow) for cities on the east andwest sides of the Cascade Mountains,students will discover that volcanicmountains do not have to erupt to affectthe atmosphere.

Key Teaching Points1. The Cascade Range comprises a1,130-kilometers (about 700 miles) longchain of volcanoes lying about 160 to240 kilometers (100 to 150 miles) inlandfrom the coast of the Pacific Ocean. Theirlocation affects the climate of the PacificNorthwest region.2. Because the Cascades act as a geo-graphic barrier to moisture-laden massesof air arriving from the Pacific Ocean,cities on the west side of the mountainreceive more precipitation annually thanthose on the east side. The cities on theeast side are in the "rain shadow" createdby the mountains.

Materials1. Activity Sheets 3.2 ab2. Wall map of the United States3. Glass of ice water

Procedures1. Using a large wall map, locate theCascade Range. Remind students thatMount St. Helens is one of the volcanicmountains that make up the CascadeRange.

2. Tell students that in the PacificNorthwest region, the prevailing windsblow from west to east. That means thatmost of the weather that affects theregion forms over the Pacific Oceanwhere it picks up a great deal of mois-ture. Given this fact, ask students if theythink annual precipitation is greater orlesser on the west or east side of themountains.

3. Distribute Activity Sheets 3.2 ab.

4. After the students have completedtheir activity sheets, discuss with themthe reasons why cities on the west side ofthe Cascade Range have a greater precip-

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a mountain receives a higher annual precipitation than

itation than those on the east side of themountains.

The mountains act as a barrier: Airmust rise to get over the mountains.As the air rises, the temperature of theair falls and moisture in the air con-denses. As the moisture condenses, itfalls as rain or snow. By the time theair reaches the top of the mountain,most of the moisture has been lost asrain or snow.As the air descends on the other sideof the mountain, most of the moisturethat remains is lost through evapora-tion instead of falling as precipitation.That is why cities on the western, orwindward, side of the Cascadesreceive a higher annual precipitationthan those on the eastern, or leeward,side of the Cascades. The mountainshave produced a "rain shadow" on theleeward side (fig. 4 ).

ExtensionHave students prepare reports discussinghow the differences in precipitation in thePacific Northwest affect the naturalresources and economy of the region.

34

Activity Skeet 2

3. Western EasternEugene BurnsOlympia PendletonPortland SpokaneSalem Walla WallaSeattle Yak i maTacoma

4. Western average precipitation:162 centimetersEastern average precipitation:52 centimeters

5. The cities on thc west sidereceive more precipitation

Volcanic ash can be a serious hazard to jet airplanes whenthey are flying. Because pilots may not see volcanic ashclouds, they can fly into them. When ash is sucked into ajet engine, it can cause the engine to stall.

Activity Sheet 3.1aTracking an Ash Cloud

Fortunately, when this has occurred, the pilots were able torestart their engines, but only after losing many thousandsof meters in altitude.

You are air traffic controllers and you have just received awarning that there was a major eruption of Mount St.Helens this morning. The air space you monitor is in thepath of an ash cloud. Your job is to calculate approximatelyhow many hours it will take the ash cloud to move into theair space you monitor. The warning notice states that theash cloud is moving at a rate of 96 kilometers per hour(60 miles per hour).

Knowing how fast the ash cloud is moving, your job is tocalculate approximately how many hours (the time)it will take the ash cloud to reach your air traffic controltower.

What to do

List the following information:

1. On the map, find the location of your tower.Mark it on the map.

2. Find Mount St. Helens. Mark it on the map.

3. Look at the map legend. Calculate the number of kilo-meters (distance) your tower is from Mount St. Helens.My tower is kilometers from Mount St. Helens.

4. Use this formula to find how many hours (time) it willtake the ash cloud to reach your tower.

Distance

Rate (speed) x Time5. The ash cloud will reach your air traffic control tower

in hours.

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MMount St. Helens is one of the volcanic mountains thatmake up the Cascade Range. The Cascade Range isabout 1,130 kilometers (700 miles) long. It is located about160 to 240 kilometers (100 to 150 miles) inland from thecoast of the Pacific Ocean. The location of the mountains

Activity Sheet 3.2aIn the Rain Shadow

affects the climate in the Pacific Northwest. Cities locatedon the western side of the mountains receive differentamounts of precipitation (rain and snow) than cities locatedon the eastern side of the mountains.

What to do

1. On the map, the symbol A marks a volcanic mountain inthe Cascade Range. Find each of the volcanoes listedbelow. Then, on the map draw a line connecting all theA symbols. The line you have drawn will show you theapproximate location of the Cascade Range.

Mt. AdamsMt. BakerGlacier PeakMt. Hood

Mt. JeffersonLassen PeakMt. RainierMt. ShastaMount St. Helens

2. On the map, find the west side of the Cascade Rangeand write the letter "W." Then find the east side of theCascade Range and write the letter "E." (Hint: thePacific Ocean is to the west of the Cascade Range.)

3. On the map, each of the following cities is marked withthe symbol .

NameBurns, Oreg.Eugene, Oreg.Olympia, Wash.Pendelton, Oreg.Portland, Oreg.Salem, Oreg.Seattle, Wash.Spokane, Wash.Tacoma, Wash.Walla Walla, Wash.Yakima, Wash.

Annual Precipitation47 centimeters (12 inches)169 centimeters (43 inches)201 centimeters (51 inches)47 centimeters (12 inches)146 centimeters (37 inches)158 centimeters (40 inches)154 centimeters (39 inches)71 centimeters (18 inches)146 centimeters (37 inches)62 centimeters (16 inches)32 centimeters (8 inches)

Find each city on the map. Is it east or west of theCascade Range? On the chart below, list each city in eitherthe "Eastern Cities" or "Western Cities" column and write inthe annual precipitation for each city.

Western Cities Eastern Cities

4. Find the average amount of precipitation that the"Eastern Cities" get and the "Western Cities" get.

Average precipitation for "Eastern Cities":

Average precipitation for "Western Cities":

5. Do cities on the east or west side of the Cascade Rangereceive more precipitation?

38

Activity Sheet 3.2bIn the Rain Shadow

BEST COPY AVAILABLE

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U.S. Department of the InteriorU.S. Geological Survey

fig. 1

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Mount St. Helens

Mount St. Helens 2 years before its catacylsmic eruption. When the volcano explodedon May 18, 1980, huge volumes of snow and ice quickly melted and contributed todevastating floods and mudflows.

As hot volcanic debris melted snow andglacier ice on the upper slopes of MountSt. Helens, mudflowsfast-moving mix-tures of volcanic debris and waterdeveloped within minutes of thebeginning of the May 18 eruption. By10:10 a.m. Pacific Daylight Time, a mud-flow had traveled 43 kilometers (27miles) downstream in the South ForkToutle River valley. And before the dayended, nearly all the streams that hadtheir sources on Mount St. Helens wereaffected by mudflows.

Fortunately, the major mudflow tookhours to reach populated areas, givingpeople time to evacuate. As a result, onlya few deaths were attributable to mud-flows. Volcanic mudflows are also calledlahars, a term borrowed from Indonesia,where mudflows are a major volcanichazard.

Mudflows' Destructive ForceThe largest and most destructive mudflowcame down the valley of the North Forkof the Toutle River. It originated from thehot debris from the avalanche, lateralblast, and ash falls that had been deposit-ed in the upper part of the river valleyduring the first few minutes of the erup-tion. By afternoon, water from meltingsnow and glacial ice, and from within thedebris itself began to flow.

The mudflow steamed with hot vol-canic materials (pyroclastic debris).Thick, like freshly mixed cement, themudflow enveloped almost anything thatit picked up along its path. Eyewitnessesreported seeing everything from icechunks to a fully loaded logging truck inthe flowing mixture. As debris, mud, andfallen trees choked the Toutle River, theriver overflowed its banks and flooded,cresting at 6.4 meters (21 feet) above itsnormal stage.

4 0

LESSON 4

Snow and ice Compound DangersMudflows are particular hazards at snow-capped volcanoes such as Mount St.Helens. Even small eruptions of hot vol-canic material can very quickly meltlarge volumes of snow and ice. Theresulting surge of water erodes and mixeswith volcanic rock to become mudflows.For example, the 1985 eruption ofNevada del Ruiz in Colombia was a verysmall eruptionejecting only about 3percent as much magma as Mount St.Helensyet it generated high-volumemudflows because of the presence ofsnow and glacial ice on the volcano. Themudflows that swept down from Nevadadel Ruiz buried the town of Armero,killing more than 23,000 people. Nevadadel Ruiz, like Mount St. Helens, hassnow and ice year round at its highestelevations.

The Risk of Mudflows ContinuesEven without a major eruption, mudflowsand floods remain potential hazards ofMount St. Helens. As a result of the May18, 1980, eruption, huge volumes of vol-canic debris dammed preexisting streams.Because these dammed streams are com-posed of loose materials, they are struc-turally weak. If the dams fail, mudflowsand floods can occur. Loose volcanicdebris on steep slopes is also vulnerableto flowing during or after heavy rainfalls.The risk of mudflows and floods is great-est on Mount St. Helens during the win-ter months when precipitation is heaviestand the snowpack is thickest.

Activity 1 TOCE2CHE

30-minute demonstration45-minute work sessionStudents participate in a demonstrationthat will help them visualize the consis-tency of mudflows and how they movedown stream valleys away from avolcano's summit or flanks. In a worksession, students use topographic mapsof Mount St. Helens before the 1980eruptions to forecast the path mudflowsmight take during an eruption.

Key teaching points1. Volcanic avalanches and volcanicmudflows are somewhat similar, but dif-ferent in one important respect. Both cancontain (a) volcanic debris, such astephra of varying sizes ejected during anongoing eruption, and (b) lava and rocksfrom previous eruptions that weredeposited on the volcano's slopes.Mudflows, however, are mixtures of vol-canic debris and water. Volcanicavalanches lack the water of mudflows.

2. Sources of water can include the (a)breakout of a volcanic or glacial lake, (b)melting snow and glacier ice, (c) streamsand rivers that flow down the flanks of avolcano, and (d) intense rainfall.

3. Mudflows behave differently thanavalanches. Because water acts as a lubri-cant, mudflows travel farther thanavalanches. Both avalanches and mud-flows can move very fast.

4. Mudflows move downslope and intostream valleys.

5. Being able to forecast the path ofmudflows is important to scientists whoassess the potential hazards of volcaniceruptions. The chief threat to people isburial. Structures are at risk of beingburied, carried away, or collapsing.

MaterialsDemonstration

1. Newspapers2. Large plastic tarp, 9' x 12'3. Rocks, bricks, or tent stakes to hold

the tarp in place4. Buckets

tftdo PE,11 Gil unul

5. Large spoons or other sturdy stirringinstruments

6. One paper cup for each student7. Sand and gravel8. Water

Work Session1. Activity Sheet 4.1a-b2. Transparencies made from Master

Sheet 4.1 and Activity Sheet 4.1b.3. Overhead projector

Procedures:Simulating an avalanche and mudflow1. Outdoors, construct a mockup of avolcano by crumbling up newspapers andpiling them into the shape of a volcano.

2. Place a tarp over the newspapers.Make sure the tarp is large enough tosimulate a flat area at the volcano's base.Also, create plenty of "hills" and "val-leys." For ideas, refer to the photographson the poster and to the topographic mapon Activity Sheet 4.1b.

3. Place bricks, rocks, or tent stakesaround the base of the tarp to keep itfrom moving.

4. Tell students that they will be creatingan avalanche. Ask them to forecast thepath the avalanche will take.

5. Create an avalanche:Distribute paper cups and fill themwith sand.Pour the contents onto the top of thevolcano to simulate an avalanche.Repeat with gravel and then againwith a mixture of sand and gravel.Have students observe where thematerials slide and which particlesmove fastest.Discuss why. (Gravity pulls the mate-rials downslope. The heaviest particlesmove fastest; the smallest particlesmove the farthest because they requireless energy to move them.)

6. Create a mudflow:In a bucket, mix water with sand andgravel to make a slurry.Distribute paper cups and fill themwith the slurry.

41

Pour the slurry onto the top of the vol-cano.Discuss: Where did the mudflow flow?(It should go into the valleys.) Did itbehave differently than the avalanche?What happens when the avalanche hitsthe flat area at the base of the volcano?(Slows down)

Work Session:Forecasting the path of mudfiowsBased on what they saw in the demon-stration, students use a topographic mapof Mount St. Helens before the 1980eruption to forecast the paths mudflowsmight take as a result of an eruption. Thestudents then compare their maps withthe map that shows the path the flowsactually took following the May 18,1980, eruption. (Master Sheet 4.1)

Distribute Activity Sheets 4.1a-b.Note that the topographic map onActivity Sheet 4.1b is the same as Map Ain Lesson 2 except that it (a) covers amore extensive area, (b) the contourinterval is 150 meters instead of 100meters, and (c) north is oriented towardthe top of the map.

Discussion1. Discuss the students' forecasts. Willmudflows follow stream valleys? Willmudflows occur on all sides of the vol-cano?

2. Show students a transparency ofMaster Sheet 4.1. Compare this mapwith the students' forecast maps.

3. Discuss why the south flank and thearea to the south were relativelyuntouched by mudflows. (The lateralblast blew hot volcanic debris to thenorth.)

4. Using your transparencies, comparethe extent of the glaciers on Mount St.Helens before and after the eruption.What happened to the glaciers? Whathappened to the ice in the glaciers? (Itwas melted by the heat of the eruption orwas "ground up" by the avalanche.)

5. Bring up the point that Mount St.Helens behaved in an unexpected way

that even the scientists did not anticipate.(For example, David A. Johnston, aUSGS volcanologist, was monitoringMount St. Helens on a ridge north of thevolcano, well outside of the anticipateddanger zone, or so he thought. At 8:30a.m. on May 18, 1980, Dr. Johnstonmade his last radio transmission:"Vancouver, Vancouver, this is it!" Notrace of him or his equipment has everbeen found.)

Activity 2 cln SEE072 CD{' Znom mnk

fig. 2

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North Pole 75°N 60°N 45°N 30°N 15°N

This diagram shows how the elevation of the snowline changes with latitude.The approximate elevation of the snowline is indicated on this diagram where thewhite and black areas meet.

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45-minute demonstration45-minute work sessionStudents observe a demonstration ofhow melting snow and ice can contributeto mudflows and then learn in a worksession why some volcanic mountainshave permanent snow and ice.

Key teaching points1. Some volcanic mountains have perma-nent snowpackssnow that does notmelt during the summer months. Thelowest elevation at which snow remainson a mountain during the summer iscalled the snowline. (A mountain that hasno snow in the summer has no snowline.)The snowline moves up and down amountain seasonallylowest in late win-ter and highest in late summer.

2. The snowline is related to air tempera-ture, which in turn is influenced by eleva-tion and distance from the Equator: airtemperature drops as elevation increasesand distance from the Equator increases.Even in areas near the Equator, there aresome mountains that have snow year-round at their highest elevations, whereasin polar regions permanent snow can befound close to sea level during the sum-mer months.

4 2

3. The snowline is highestthat is, lessof the mountain is covered with snow inthe summeron mountains closest to theEquator. The snowline is lowest on landclosest to the poles. The greater thedistance from the Equator, the less eleva-tion is necessary to establish a snowline.(fig. 2)

4. The snowline also is influenced by theamount of yearly snow fall. Thus, thesnowline may not be the same for allmountains at the same latitude.(Generally, mountains closest to an oceanreceive the greatest amounts of precipita-tion.)

5. Melted snow and glacial ice signifi-cantly contributed to creating the mud-flows that followed the May 18, 1980,eruption of Mount St. Helens.

MaterialsDemonstration

1. Potting soil, gravel, and water2. Baking pan3. Freezer4. Bunsen burner

ctivity 2 Conlvol

Work Session1. Magazines2. Large world map and push pins3. Activity Sheet 4.2a-b4. Transparency of "Snow line Diagram"

(fig. 2)

ProceduresDemonstration

1. The day before the demonstration:In a baking pan, mix potting soil, gravel,and water to make a slurry. Place the bak-ing pan in a freezer for at least 8 hours.

2. The next day: Bring the frozen slurryinto class. Set it up at a steep angle. Holda Bunsen burner under the high end ofthe baking pan. (fig. 3) Observe the panat 3-minute intervals. Wait for the slurryto melt.

3. Point out to the students that thisdemonstration is similar to what happenswhen the heat of an eruption melts snowand ice on a volcanic mountain: watermixes with volcanic debris and createsmudflows.

4. Look at poster figures 10 and 11 thatshow Mount St. Helens before and afterthe eruption.

Work Session:1. Make a transparency of the "SnowLine Diagram" (fig. 2).

2. As a homework or library assign-ment, have students collect pictures ofsnow- and ice-covered mountains. Askthem to make a list of the names of themountains and the countries or continentswhere they are located. (Collect your

fig. 3

own group of photographs to make surethat all of the continents are represented.)

3. In class, make a list of continents onthe chalkboard and compile the numberof snow- and ice-covered mountains thatthe class found on each continent. Askstudents if they expected to find snow-covered mountains in every continent.

4. Remind students that when Mount St.Helens erupted on May 18, 1980, it wascapped by snow and numerous glaciers.Ask students if they would expect to seesnow in May.

5. Distribute Activity Sheets 4.2a-b.

6. Students first label a group of volca-noes on a blank map. After they completethis part of the activity, ask them to stop.

7. Using a transparency, explain the"Snowline Diagram." This chart showshow the snowline varies with elevationand latitude. To plot a volcano and findits snowline :

Find the approximate latitude of thevolcano along the bottom of the chartand put a mark.Keep one finger on that spot and thenfind the approximate elevation alongthe right hand side of the chart.Put a mark where the two points cometogether. (For younger students, youmay need to do this exercise as aclass.)

8. Explain the concept of a snowline tothe class.

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Activity Sheet 2

Part A2, Nevada del Ruiz3. 4°N4. Surtsey, 63°N

Part B1. Mount Vesuvius2. Mount Etna3. Kilauea4. Mauna Loa5. Mount Rainier6. Mount Fuji7. Mount Pei&8. Katmai9. Lassen Peak10. Paricutin11. Surtsey12. Sunset Crater13. Mount St. Helens14. Nevada del Ruiz

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Activity Sheet 4.1aForecasting the Path of Mudflows

hour) on a volcano's steepest slopes. In some placesthe mudflows were between 100 to 200 meters (30 and 60feet) deep.

What to do

1. Use the topographic map of Mount St. Helens to fore-cast the paths you think the mudflows took as a result ofthe May 18, 1980, eruption.

2. Color in the paths on your map.

3. Write a brief explanation to support your forecast.

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Activity Sheet 4.2aThe Snowline

The snowline differs on volcanoes depending on how far avolcano is from the Equator and the volcano's elevation.

What to do Part A

1. Label the volcanoes listed below on the blank map.(All the volcanoes are north of the Equator.) Write thevolcano's elevation on the map.

Volcano1. Mount Vesuvius2. Mount Etna3. Kilauea4. Mauna Loa5. Mount Rainier6. Mount Fuji7. Mount Pelée8. Katmai9. Lassen Peak10. Paricutin11. Surtsey12. Sunset Crater13. Mount St. Helens14. Nevada del Ruiz

Location40N 14E37N 15E19N 155W8N 157W46N 121W35N 138E14N 61W58N 154W40N 121W19N 102W63N 20W35N 111W46N 122W4N 75W

2. Which volcano is closest to the Equator?

What is its latitude?Elevation in meters1,281 (Italy)3,350 (Italy) 3. Which volcano is farthest from the Equator?1,222 (USA)4,170 (USA)4,392 (USA) What is its latitude?3,776 (Japan)1,397 (Martinique)2,047 (USA) 4. Would a volcano at 10°N be closer to the Equator than a3,187 (USA) volcano at 45°N?1,780 (Mexico)155 (Iceland) (Latitude shows us distance from the Equator.)2,447 (USA)2,549 (USA)5,321 (Colombia)

What to do Part B

Use the Snowline Diagram to find out which of the volca-noes on your map will have snow on them during the sum-mer.

1. For volcano #1, find its latitude along the bottom of thechart. Put a mark there.

2. For volcano #1, find its elevation in meters along theright hand side. (Round off to the nearest thousand.) Puta mark there.

3. Put a mark where the two points come together. Is themark above the dark area of the diagram? If yes, thatvolcano is likely to have snow on it during the summer.

4. If the volcano is likely to have snow on it during the sum-mer, put a * next to it on the list of volcanoes.

5. Repeat steps 1-4 for all of the volcanoes on the list.

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"This is It!"

David A. Johnston, USGS volcanologist, was monitoring Mount St. Helens on aridge north of the volcano. At 8:30 a.m. on May 18, 1980, he made his last radiotransmission: "Vancouver, Vancouver, this is it!" No trace of him or his equipmenthas ever been found.

The Impact on PlantsThe force of the lateral blast from MountSt. Helens' north flank blew down orsnapped off trees within a radius of 25kilometers (15 miles) north of the erup-tion site. At a distance of 25 kilometers(15 miles) from the blast, the force wasno longer powerful enough to mow downtrees, but it remained hot enough to killthe trees in its path. Ironically, some ofthe trees killed were old-growth Douglasfirs 200 to 500 years old, which had sur-vived previous eruptions.

Devastation in the wake of theavalanche was equally dramatic, althougha few individual plants did survive,sprouting from root fragments that hadbeen swept along on the surface of thedebris. Plant survival in the path of themudflows was likewise sparse. In addi-tion, ashfall, which blanketed the forest

to the northeast, smothered small plantsand retarded the growth of larger ones.

The Impact on AnimalsIn the area affected by the blast, almostall wildlife vanished. Animals livingabove ground in the blast zone had noprotection. Birds were particularly hardhit. Even those birds that survived the ini-tial blast and avalanche died because theinsects and plants they ate had perished.Insects were heavily affected, particularlyby volcanic ash: the insects suffocatedbecause ash clogged their body pores, orthey dehydrated because glass-like ashabraded the cuticle that helps them retainmoisture. Fewer than one-half of thesmall mammal species thought to havebeen living near Mount St. Helens wereknown to have survived. The death toll

52

LESSON 5

was nearly 7,000 large game animals,including deer, elk, and bear. The erup-tion severely damaged 26 lakes, killingan estimated llmillion fish, as well asincalculable numbers of fresh-waterinvertebrates. The loss of human liveswas 57.

Some Organisms SurvivedThe most surprising discovery following

the eruption, however, was that manyorganisms survived in what appeared tobe a lifeless gray landscape. In particular,plants sprouted in areas that had beenprotected under a snow cover and alongstream banks and hillsides where erosionthinned ash deposits. Within a month,fireweed appeared from roots that hadsurvived even though the tops of theplants were sheared off. Animals such asgophers and ants survived in their subter-ranean homes, while lake-dwelling frogsand salamanders escaped the blast undera protective cover of late winter ice.

The RecoveryThree years after the eruption, biologistshad identified the recovery of more than90 percent of the preeruption species ofplants. Many plants owed their lives togophers. These burrowing animals actedlike garden tillers, by bringing the exist-ing soil to the surface and mixing it withnutrient-rich volcanic ash deposited bythe May 18, 1980, eruption. As thegophers dug, they also brought seeds,bulbs, and root fragments up to the sur-face where they could begin to grow. The"tilled" soil was also far more likely totrap seeds blowing across its surface.

1M conic SoilsActive volcanoes are also respon-sible for some of the world's mostfertile soils. Tephra commonlycontains potassium and phospho-rus, two nutrients essential toplant growth. As tephra weath-ers, these nutrients are releasedinto the soil, acting as a time-released fertilizer. The benefits ofvolcanic soils often lure people torisk living in the shadow of activevolcanoes.

In the forests, ash initially retarded thegrowth of surviving trees, but as rainswashed the ash off leaves and needles,growth recovered. The layers of ash thatremained on the ground enhanced growthfor several years. The ash had a mulchingeffect, keeping in check understory plantsthat normally compete with trees forwater and nutrients. Because of its light,reflective color, a coating of ash can helpsoil retain moisture as well.

Although few large mammals survivedin the blast zone, fresh deer tracks wereseen within 10 days. Black-tailed andRoosevelt elk were among the gamespecies that moved in from adjacent areasand took advantage of the survivingplants that were beginning to recover.Spirit Lake was black and putrid, but itwas not deadonly different. Its watershad been taken over by opportunistic bac-teria, feasting on tons of organic matterthat had avalanched into the lake. Tenyears after the eruption, half a milliontree trunks still drifted across the lake'ssurface; but the recovery had beenremarkable. Lake life had almostreturned to normal.

Volcanic eruptions are a fact of life forforests at Mount St. Helens. Like wild-fires, they are among various natural dis-turbances that continuously alter thegrowth of a forest and foster diversity.Without periodic clearing by naturalcauses, forests could not renew them-selves.

Ictivity slnE s

45-minute work sessionStudents learn how to "read" tree rings todetermine the date of a volcanic eruptionand the effects an eruption has on plantgrowth.

nit leaching points1. If you look at the top of a tree stump,you will see a series of concentric ringsin the cross section of its trunk. Becausea single tree ring is usually formed eachyear, tree rings can be used to date thetree.

2. Tree ring boundaries are distinguishedby a change in appearance between thesmall thick-walled cells produced at theend of a growth season and the large thin-walled cells produced at the beginning ofthe next growth season. The woodbetween these boundaries is formed dur-ing one growth season and constitutesone growth ring (fig. 2). Once the ringhas formed, it remains unchanged duringthe life of the tree.

fig. 2

E "figigan

3. Scientists use tree ring data to helpthem establish the date of volcanic erup-tions: the width of each year's growthrecords evidence of natural events, suchas floods, drought, fires, and volcaniceruptions, that increased or decreased thewidth of that year's ring growth (fig. 2).

4. Tree rings record both the negativeand positive effects of volcanic eruptions.After the 1980 eruption of Mount St.Helens, ash that blanketed forests to thenortheast of the eruption retarded growthfor about 2 years. As rain washed awaythe ash, the rate of tree growth recoveredand actually increased. The effect of theash was equivalent to putting mulch ongarden plants the mulch reduced com-petition for water and nutrients by plantsin the understory (in a garden mulchhelps retain moisture and keep weedsfrom competing with other plants.)

Materials1. Activity Sheets 5.1ab2. Log with visible tree rings (optional)

This 120-year old tree records the 1912 eruption o

IC 0

Mount Katmai, Alaska.

Procedures1. Using either a piece of cut log or adiagram drawn on the chalkboard of across section of a tree, explain what treerings are and what evidence they recordabout natural events that occurred duringa tree's life.

2. Discuss the impact of the May 18,1980, eruption of Mount St. Helens onthe animal and plant life in the areaaround the volcano. Use poster figure 19to point out that a massive number oftrees were killed during the eruption bythe lateral blast, by forest fires started bylightning, and by avalanches and mud-flows. Trees that survived, however, werecharred or had their growth affected bythe ash that covered the ground.

3. Distribute Activity Sheets 5.1ab.Explain to students that they will use treering data to determine the date of aneruption of Mount Katmai in Alaska andthe effect that the eruption had on thegrowth of a tree. (The tree's growthdecreased for 3 years following the erup-tion but then increased for 12 years.) As alibrary assignment, they will make a timeline and record on it important events thatoccurred during the life span of theMount Katmai tree.

ExtensionHave students draw tree ring patterns oftheir own and trade with other students tointerpret.

Muhl/ Sheet 1

1. 1 20 years2. 18423. 19124. 35. -126. The ash helped to fertilize

the soil

Activity 2 [ii t2

45- to 60-minute work sessionIn a role-playing exercise, students useeyewitness accounts to gather and evalu-ate information about the events of theMay 18, 1980, eruption of Mount St.Helens.

Key teaching points1. Many people who were in the vicinityof Mount St. Helens during the eruptionwere interviewed to gain informationabout the nature and sequence of eventsof the eruption.

2. Although somewhat subjective, theseobservations were an important compo-nent of the scientific investigation of theeruption.

Materials1. Overhead projector2. Transparency of Master Sheet 5.2a3. Master Sheets 5.2ad4. Activity Sheets 5.2ab (photocopy)

Procedures1. Tell students that on May 18, 1980,people at many locations in the vicinityof Mount St. Helens witnessed the erup-tion of the volcano. They observed awide variety of phenomena associatedwith the eruption, including an earth-quake, a massive avalanche, the lateralblast, mudflows, and the fall of airbornematerials (tephra, including fine-grainedash). As a review of previous lessons, askstudents to name the phenomena theythink the eyewitnesses would have seen,heard, or felt.

2. On an overhead projector, show atransparency of Master Sheet 5.2a thatshows where the eyewitnesses werelocated when the eruption occured.

i 3. Students play the following roles:reporter(s), eyewitnesses, and scientistswho are serving on a committee investi-gating the eruption.

54

4. Distribute one account to each of theeyewitnesses (see Master Sheets 5.2bd).Ask eyewitnesses to read the accounts inpreparation for being interviewed by areporter. Encourage students to use propsto help them relay their accounts. Whenthey are interviewed, the students shouldanswer questions in their own words.

5. Distribute Activity Sheets 5.2ab tothe scientists. Tell the scientists to takenotes while listening to the interviews.After hearing all the interviews, theyshould list the similarities and differencesamong the accounts on their ActivitySheet.

6. Divide the scientists into groups offour to six students and ask each group todiscuss their recollections of the eyewit-ness accounts. Eyewitnesses should cir-culate among the groups of scientists toanswer questions. Each group of scien-tists should prepare a written summarythat attempts to reconcile the eyewitnessaccounts.

NOW Sea Os

Green River

NortFor

Line

South Fork Tout le River

55

Mount St. Helens

Leone 10 kin

Master Sheet 5.2bThese 10 accounts are listed in approxi-mate chronological order correspondingto the sequence of the eruptive events.The number following the site locationcorresponds to the numbers on the map

(Master Sheet 5.2a ) showing the loca-tion of eyewitnesses.

Photocopy both sides. Cut up like notecards.

Eyewitness Account #1:Name: K. and D. Stoffel (geologists)Event witnessed: avalanche and beginning of the eruptionSite location: in a small aircraft directly over Mount St.Helens

"As we approached the summit, flying at an altitude ofabout 11,000 feet, everything was calm...Just as we passedabove the western side of the summit crater, we noticedlandsliding of rock and ice debris... Within a matter of sec-ondsperhaps 15 the whole north side of the summitcrater began to move instantaneously...The entire massbegan to ripple and churn up...then the entire north side ofthe summit began sliding north...We took photographs ofthis slide sequence occurring, but before we could snap offmore than a few pictures, a huge explosion blasted out ofthe avalanche-detachment... We never felt nor heard athing...From our viewpoint, the initial cloud appeared tomushroom laterally [sideways] to the north and plungedown. Within seconds, the cloud had mushroomed enoughto obscure our view."

Eyewitness Account #2:Name: P. and C. Hickson (geologists)Event witnessed: avalanche and beginning of the eruptionSite location: 15 km (9 miles) E/Near road 125, east ofMount St. Helens

"As the avalanche reached the halfway point on the moun-tain, the summit eruption began with a dense black cloudfollowed by lighter gray material. A second eruptionhalfway down the slope occurred moments later." At thistime the avalanche appeared to consist of upper and lowerparts. The flank eruption was between the two. Secondslater the upper slide overrode the flank eruption and mater-ial was hurled far down the slope onto the lower slide.About 45 seconds after the avalanche began, the eruptivecenters merged and the rapidly expanding cloud overtookthe avalanche.

Eyewitness Account #3:Name: J. Downing (climber)Event witnessed: directed blastSite location: 75 kilometers (47 miles) N/climbing onMount Rainier at 3,200 meters (1,050 feet)

Climbers on Mount Rainier observed two distinct "flows,"which began very shortly after the eruption started. These"flows" were described as clouds 300 to 600 meters (1,000to 2,000 feet) thick that appeared to hug the ground. Theheads of the "flows" disappeared into valleys and reap-peared as they "hopped" over ridges. The earlier flow trav-eled to the west, perhaps down the North Fork ToutleRiver, and was followed almost immediately by a "flow"that seemed to travel to the east.

Eyewitness Account #4:Name: C. McNerneyEvent witnessed: directed blastSite location: 13 kilometers (8 miles) NW/driving onsouth side of North Fork Toutle River

Following the collapse of the north side, a foglike ring (cloud)descended very quickly and expanded out from the mountain.At about 2 minutes after the beginning of the eruption, the wit-nesses began driving west at about 110-120 kilometers perhour (70-75 miles per hour). At this speed, they did not seemto get any farther away from the cloud. The wind blowing intothe car was warm enough to give the impression that the carheater was on. They increased their speed to 135 kilometersper hour (85 miles per hour) and began outdistancing thecloud. About four kilometers (2.5 miles) farther west theystopped and could not see the black cloud. After a short timethe cloud reappeared. The base of the black cloud looked "likeavalanches of black chalk dustfirst one part of the blackcloud would shoot out in front, then another, then another, likewaves lapping up on a beach." Pulling back onto the highway,they outran the cloud at about 105 kilometers per hour (65miles per hour).

58

Master Sheet 5.2c

Eyewitness Account #5:Name: W. and L. JohnsonEvent witnessed: directed blastSite location: 17 kilometers (10.5 miles) NE/on ridge topwith good view of Mount St. Helens

Shortly after the vertical eruption began, a large horizontalblast occurred. Just before the top of the mountain becameobscured, the south side of the summit crumbled into thehole formed by the avalanche. As the cloud grew, whatappeared to be a shock wave similar to that associated witha nuclear explosion moved ahead of the cloud. About 1 1/2minutes after the start of the avalanche and perhaps 45 sec-onds after the start of the blast, a noise like a clap of thun-der accompanied some sort of pressure change. The initialnoise was followed by a continuous rumbling, "like afreight train."

Eyewitness Account #6:Name: C. Rosenquist (amateur photographer)Event witnessed: directed blastSite location: 17 kilometers (10.5 miles) NE/ on ridge topwith good view of Mount St. Helens

A rumbling noise began within 7-8 seconds of the start ofthe avalanche. One member of the group sensed a pressuredecrease at about the same time. A "shock wave," whichlooked like heat waves, formed ahead of the blast cloud.

Eyewitness Account #7:Name: M. and L. Moore (campers)Event witnessed: directed blast and ash cloudSite location: 22 kilometers (14 miles) N/on north side ofGreen River

A noise similar to, but which "didn't sound quite right" for,a propeller-driven aircraft occurred for 10-20 secondsbefore a rapid pressure change, which caused ears to popnumerous times over a period of about 10 seconds. Oneperson also felt as if she was being squeezed gently overher entire body. A short time later, an immense ash cloudapproached that seemed to consist of a lower vertical walland upper overhanging part.

Eyewitness Account #8:Name: B. Nelson (logger)Event witnessed: directed blastSite location: 21 kilometers (13 miles) N/on north bank of theGreen River

The witness and two companions were cutting timber withchain saws. Mount St. Helens was hidden by a ridge and thethree men neither heard nor felt anything unusual until theywere alerted to the eruption by a fourth man. About 10 secondslater, "a horrible crashing, crunching, grinding sound" camethrough the trees from the east. Suddenly, it became totallydark: " I could see absolutely nothing." It immediately got veryhot, and almost impossible to breathe. While the men weregasping for air, the inside of their mouths and their throats wereburned. The witness was knocked down, although he does notrecall being hit by rocks or other projectiles. He arose with hisback to searing, painful heat that lasted about 2 minutes. Alltrees had been knocked down, and everything was covered withabout a foot of drab gray ash. None of the men's clothing hadbeen burned, but their bodies had been burned extensively.Three of the men subsequently died. Heavy ash fall resumedafter about 20 minutes.

57

Master Sheet 5.2d

Eyewitness Account #9:Name: V. Dergan and R. ReitmanEvent witnessed: mudflowSite location: 40 kilometers (25 miles) NW/on the SouthFork Tout le River

Sometime after 9:00 a.m. Pacific Daylight Time, the SouthFork Tout le River began rising and quickly rose about ameter (3 feet). The river was slightly muddy and carriednumerous logs. About 2-3 minutes after the first logsmoved downstream, a railroad bridge moving at about 40kilometers per hour (25 miles per hour) appeared. Treeswere being snapped off. As the bridge went by, large logsbehind it rolled up the bank. The mass of thick mud andlogs pushed the witnesses and their car off the bank andinto the river. They were swept along for about 5 minutesat about 40 to 50 kilometers per hour (25 to 30 miles perhour) in very thick, warm mud. The witnesses jumpedfrom log to log toward shore where the flow was movingmore slowly, and waded through warm mud over 5 meters(1.5 feet) deep. The mud continued to rise slowly for ashort time. After perhaps 15-30 minutes the mud and logsstopped moving.

Eyewitness Account #10:Name: B. Nelson and S. RuffEvent witnessed: tephra fallSite location: 21 kilometers (13 miles) N/on north bank ofGreen River

After the blast and a few minutes of clear sky, hot ashbegan to fall. Again, it became totally dark. This ashseemed to fall vertically. It was "like someone pouring abag over your head." The extremely heavy ash fall lastedabout 15 minutes. The ash fall was so intense that the wit-nesses had to use their fingers to dig the ash out of theirmouths. They put their shirts over their heads in an effortto keep the ash out of their mouths and noses. After 15-20minutes "stuff started coming out of the sky." They couldhear this material hitting trees. One witness was hit on thehead by something large enough to raise a lump. Duringthe heavy ash fall, they became cold, sleepy, and nauseous,but did not suffer from headaches. After an hour and a halfvisibility began to return.

58

Have you ever looked at a tree stump and noticed itsrings? Count the rings and you will know how old the treeis. Each ring represents 1 year in the life of the tree.

Activity Sheet 5.1aDating A Volcanic Eruption

If you look closely at tree rings, however, you will see thatthe spaces between rings vary in width. Trees do not growthe same amount each year

What to do What you want to find out:

You can "read" these tree rings and find out what year 1. The tree's age:there was an eruption of Mount Katmai in Alaska.

What you know:1. This tree was growing 48 kilometers (29 miles) northwest

of Katmai Volcano.

2. After the eruption, the forests were blanketed in ash.

3. This tree's growth decreased for some years after theeruption, but then it increased.

4. This tree was cut down in 1962.

Make a time line for the years that this tree was alive.Research and record events that occurred during thetree's life.

BEST COPY AVAILAbLL

(Count the number of rings from the center of the treeto the bark. Each dark band represents 10 years.)

2. The year the tree started to grow:

1962 -the yearthe tree wascut down

the ageof the tree

3. The year of the eruption:

the yearthe tree startedto grow

(Count the number of rings from the center to the firstthin ring.)

4. The number of years the tree's growth decreased:

(Count the number of thin tree rings)

5. The number of years the tree's growth increased:

(Count the number of wide rings.)

6. Why do you think the tree's growth increased?

NA

ctiv

ity S

heet

5.1

bD

atin

g A

Vol

cani

c E

rupt

ion

6061

Activity Sheet 5.2aEyewitness Accounts

What to doFor each eyewitness, write in the spaces provided: thename, approximate location during the eruption, andimportant statements the eyewitness makes about theeruption.

Eyewitness #

Name

Location

Statements

These accounts were excerpted from the "Summary ofEyewitness Accounts of the May 18 Eruption," by J.G.Rosenbaum and Richard B. Waitt, Jr., in The 1980Eruptions of Mount St. Helens, Washington, USGSProfessional Paper, 1250.

Eyewitness #

Name

Location

Statements

62

U0 MActivity Sheet 5.2bEyewitness Accounts

Similarities

Eyewitness #1

Eyewitness #2

Eyewitness #3

Eyewitness #4

Eyewitness #5

Eyewitness #6

Eyewitness #7

Eyewitness #8

Eyewitness #9

Eyewitness #10

63

Differences

U.S. Department of the InteriorU.S. Geological Survey

fig. I

Mount Rainierr

tsr ,G3

a

aett

=a.. a

Snow-capped Mount Rainier rises behind Tacoma, Washington. Although Mount Rainier has not erupted in the past 500 years,scientists consider it one of the most hazardous volcanoes in the Cascade Range.

Relative to other types of natural disas-ters, such as earthquakes, floods, hurri-canes, and tornados, volcanic eruptionsoccur infrequently. Of the 1,500 activevolcanoes on land, approximately 50-60erupt each year. Approximately 1 millionpeople have been killed by volcanic erup-tions during the past 2,000 years.

United States ilas Many Active VolcanoesBecause many of the most hazardous vol-canoes have not erupted during recenthistoric times, people erroneously con-sider them extinct. For Mount St. Helens,

more than a century had elapsed since amajor eruption; most people were notaware of its dangers. Mount St. Helens isone of more than 65 active or potentiallyactive volcanoes in the continentalUnited States, Alaska, and Hawaii. OnlyIndonesia and Japan have more!

Scientists of the U.S. GeologicalSurvey continue to monitor Mount St.Helens and other volcanoes in theCascade Range. They know from its pasteruptive history that many of Mount St.Helens' eruptions have occurred in con-centrated periods of time lasting decades

iL

or even centuries. For example, one erup-tive phase began in 1480 and lasted forabout 300 years. Based on that history,scientists anticipate that Mount St.Helens will continue to erupt episodicallyfor decades to come before it returns to adormant stage.

The eruption of Mount St. Helensserved as a reminder that other dormantvolcanoes can come to life again. MountShasta in Northern California, for exam-ple, probably last erupted in 1786. On ageological time scale, this very recentvolcanic activity suggests that magma is

fig. 2

Cascade Eruptions

Mount BakerGlacier Peak

Mount RainierMount St. Helens

AIIIP""111,*

24"0"Mount AdamsMount Hood

Mount JeffersonThree Sisters

Newberry VolcanoCrater Lake

Mount McLou hlinMedicine Lake VolcanoMount ShastaLassen Peak

4,000years ago

2,000years ago

present

Eruptions in the Cascades have occurred at an average rate of one to two per centu-ry during the last 4,000 years. Four of those eruptions would have caused consider-able damage and loss of life if they had occurred today without warning.

still present beneath the volcano. Onaverage, it has erupted once every 300years over the past 3,500 years. Thechance is 1 in 25 to 30 that it will erupt inany one decade and 1 in 3 or 4 within aperson's lifetime.

Forecasting More EruptionsScientists have improved their ability topredict the time of a volcanic eruption,but estimating the size and style of aneruption remains a difficult challenge.Despite this challenge, scientists try toassess the potential consequences of afuture eruption by reconstructing a vol-cano's history, which includes the pat-tern, magnitude, and frequency of its pasteruptions. The principal means of devel-oping this history is by mapping and dat-ing the different types of volcanicmaterials that have been deposited byprevious eruptions. Assembled into vol-

canic hazards maps, this information isvital for communities in volcanicallyactive areas to use for land use and emer-gency preparedness planning. Knowing avolcano's past is crucial to forecasting itsfuture behavior.

13eneffils Mien Overlooked

Because of the destructive nature of avolcanic eruption, we tend to overlook avolcano's benefits. Magma circulates anddeposits many valuable elements, such asgold, silver, zinc, sulfur, and copper.Magma heats ground water systems thatcan be tapped to produce geothermalpower. This heated ground water can alsoresult in geysers and hot springs.Volcanoes are also responsible for someof the world's most fertile soils. And vol-canoes continuously bring materials frominside the Earth to the surfacerecyclingon a grand scale.

IORMIZCT@EURE E ILoagn

45 minutesStudents create a legend that explains theexistence of Mount St. Helens.

Mu leaching points1. Mount St. Helens has been a fact oflife for people living in its shadow eversince humans began populating thePacific Northwest more than 10,000years ago. There have been dozens oferuptions during the past 4,500 years.

2. Before there were scientific explana-tions for why volcanoes erupted, peopledeveloped stories to explain the presenceand behavior of volcanoes.

3. The Yakima Indians called the vol-cano "Tah-one-lat-clah" (Fire Mountain).The Cowlitz people called it "Lawetlatla"(Person from Whom Smoke Comes). Itsmodern name, Mount St. Helens, wasgiven to the volcano in 1792 by CaptainGeorge Vancouver of the British RoyalNavy.

MaterialsNone required.

MCMINN1. Tell the legend below that was createdby the Yakima people. (Before Europeansettlement in the 19th century, theYakima people had considerable territoryon the Yakima and Columbia Rivers inEastern Washington. Today, descendantsof these people live on the Yakima IndianReservation in south-centralWashington.)

Two tribes lived across the river from oneanother Because they were friendly andpeaceful tribes, the Great Spirit built abridge across the river for them.Eventually, however, the tribes began toquarrel. The Great Spirit became angry.To punish the tribes he took away fire.The tribes prayed to the Great Spirit toreturn fire to them. Finally, the GreatSpirit agreed. To restore fire, the GreatSpirit had to go to an old woman namedLoo-Wit who, because of her goodness,still had fire. Loo-Wit promised the GreatSpirit that she would share her fire withthe two tribes if the Great Spirit would

make her eternally young and beautiful.Fire was restored, and the tribes werepeaceful for a short time. The chiefs ofboth of the tribes, however, fell in lovewith the beautiful Loo-Wit. The chiefsbegan to quarrel and went to war Onceagain, the Great Spirit became angry andin retaliation he turned the two chiefsinto mountains. One became MountHood and one became Mount Adams.Because Loo-Wit was so beautiful, theGreat Spirit made her into Mount St.Helensthat way she could remain beau-tiful forever

2. Students discuss how the legend dif-fers from the way we now explain howvolcanoes form. Are there similaritiesbetween the legend and scientific expla-nations?

3. Ask students to imagine that they livein a time and place where there are noscientific explanations for why there is anactive volcano near their community.Students create and present orally a shortlegend to explain why the volcano existsor erupts.

Extension

Do research from the journals of GeorgeVancouver, John Fremont, and otherexplorers to the Pacific Northwest tolearn their descriptions of Mount St.Helens and other volcanoes in theCascade Range. Using these accounts asa basis, students create their own diaryentries.

Activity 2Mo.392 s cow 11 McZysTfi

45-minute work sessionone followup projectUsing a volcanic hazard map of MountRainier, students reach conclusions aboutthe potential hazards of future eruptions.They then create educational materialsabout these hazards.

Key teaching points1. Mount Rainier is located 35 kilome-ters (21 miles) southeast of the Seattle-Tacoma metropolitan areaan area thathas a population of 2.5 million.

2. Mount Rainier is an active volcanowhose last major eruption was approxi-mately 150 years ago.

3. Mount Rainier has five times as muchsnow and glacier ice as all the otherCascades volcanoes combined. Mudflowsare the most dangerous hazard.

4. Throughout the volcano's history,there have been numerous mudflows.Today, parts of Tacoma, Wash., and manyother smaller communities have beenbuilt on top of these old flowsevidencethat they lie within the reach of futuremudflows that could originate from aneruption of Mount Rainier.

5. An eruption of Mount Rainier couldkill hundreds of thousands of people andcripple the region's economy.

MaterialsActivity Sheet 6.2

ProceduresWork Session

1. Review with students that Mount St.Helens is one of a number of active vol-canoes in the Cascade Range. Some oth-ers include: Mount Baker, Mount Rainier,and Mount Adams in Washington; MountHood, Mount Jefferson, and Crater Lakein Oregon; and Mount Shasta and LassenPeak in California.

2. On a large map, locate MountRainier and locate cities within 80 kilo-meters (50 miles) of it.

66

3. As a class, list the major eruptiveevents (include avalanches, mudflows,and tephra falls) that occurred during the1980 eruption of Mount St. Helens.

4. Using an overhead projector, showstudents the eruptive history map ofMount Rainier (see Activity Sheet 6.2).Explain that scientists study past erup-tions to help them forecast future erup-tions. Looking at this map, what type oferuptive events have occurred in the past.

5. Distribute Activity Sheet 6.2.Tell students they will look at MountRainier's history of volcanic mudflowsand forecast if there are any cities thatwould be at risk during a future eruption.

6. Discuss: What cities, if any, would beat risk if there were a future eruption? Isit possible, or practical, to eliminate allrisks to these cities? What things can bedone to reduce risks to life and property?Conclude that public education is a majoractivity.

Followup ProlectStudents work individually or in teams todevelop a range of educational materialsand programs for the general public,especially school children. These mightinclude posters; displays for schools,public libraries, and community centers;brochures; public service announcementson TV and radio; and information on theInternet.

Activity Sheet 2A swe

Osceola Mudflow2. 70 kilometers3. Enumclaw

Electron Mudflow2. 50 kilometers3. Ortig and Puyallup

Mount Rainier is an active volcano in the Cascade Range.During past eruptions large mudflows resulted. If similar mud-flows occurred in the future, would people be in danger?

Activity Sheet 6.2There's A Volcano in My Backyard!

BEST COPY MAK

What to do

Osceola Mudflow Electron Mudflow(occurred about 4,500 to 5,000 years ago) (occurred about 550 years ago)

1. Find the Osceola Mudflow on the map. Trace the course 1. Find the mudflow on the map. Trace its course fromof the mudflow from where it began on the slopes of the where it began on the slopes of the volcano to where itvolcano to where it ended. ended.

2. How many kilometers did it travel? 2. How many kilometers did it travel?

3. What cities would be in danger if the Osceola Mudflow 3. What cities would be in danger if the Electron Mudflowoccurred today? occurred today?

Tacoma()EnumIaW

Puyalluic

Greer?

.'te SWer

Ortig

ElectronMudflow

Caro

OsceolaMudflow

Seattle-TacomaMetro Area

Legend

Elbe

Packwood

Mount Rainier

0 50 km

67 BEST COPY AVAILABLE N

U.S. Department of the InteriorU.S. Geological Survey

So that we can improve our educationalproducts, we would appreciate yourfilling out this evaluation sheet.

Please return to:Information Services BranchNational Mapping DivisionU.S. Geological Survey509 National CenterReston, VA 20192

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Recommended readingEl easy to find and usefulD hard to find or hard to use

For more information about educationalpublications from the U.S. GeologicalSurvey, call 1-800-USA-MAPS.

We'd like to hear more about what you thought of these activities, how they were used, and how they could be improved. Pleaseuse the space below, and continue on the back, if necessary. Thank you for your comments.

68

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THE EARTH COMES ALIVE WITH

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GeoKids introduce major concepts and

navigate users through the dynamic topics

of GeoMedia.

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Computer generated animations ond

simulations facilitate understanding of

complicated processes.

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Vivid images, text, and narration describe

the components of. each section.

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Over 150 earth science glossary terms are

narrated and defined

jOIN US ON A MULTIMEDIA TOUR OF THE EARTH!

Evoking curiosity about the Earth and how we relate to it

has long been challenging, but now the best teachers are making it

fun and easy. InterNetwork Media, Inc. and its partner, the U.S. Geological

Survey, have created an exceptional CD-ROM title called GeoMedian" to help

students experience the wonder and power of the Earth, water, and the cycles

of change that are part of life on our planet.

In an array of motion pictures, sound, text, and computer animations, GeoKidsTM

present exciting interactive materials on earthquakes, water and carbon cycles,

the greenhouse effect, measuring environmental change, geologic time scales,

and understanding maps. Frank Ireton, Executive Advisor of the National Earth

Science Teachers Association said, "GeoMedia is an excellent supplement to

earth science curricula as found in the National Science Education Standards...

Teachers will be pleased with the ease of use by students."

GeoMedia was developed for grades 4 - 9. Student activities are included.

So come experience the wonders of the Earth with GeoMedia!

I . I

.

BEST COPY AVAILABLE

69

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7

How to Order

Write:Inter Network Media, Inc.411 Seventh Street Del Mar CA

{Please send check or money order, payable to

interNetwork Media Inc. Add $3 per CO for shipping and

handling. California residents add applicable sales tax. )

Phone:(619) 755-0439{order with Visa or MasterCard}

For More Information:E-mail: inm@in-inedia.comWeb: http://www.in-media.comFax: (619) 481-8181

.

InterNetwork

IA411 Seventh StreetDel Mar, California, 92014

Surfology 1011N: ;:!The sport of surfing,including oceinscience and envi-ronmental issiresfor middle schools,high schoois, andcolleges. -

GeoMeilia System Requirements

...oc compatible:486-66MHz processor with VLBWindows 3.1x or Windows 958 MB RAM (5MB free)DOS 5.0 IodatedSuper VGA (minimum 640 x480,256 colors)Double speed CD-ROMWindows compatible 16 bit sound cardWindows compatible mouse and keyboard

Software Requirements (included)Quicklime for Windows version 2.0.3

Tunting the ThieneMarine and coastaliseues,complementneUrref science ,.

Curriculum for ;high idhools andcolleges.

Earth Vitione!:,Earth and naturaltexture stockphotos formultimedia,design, andeducational uses. ,

MAC

,:i.

ROMMadntosh:

68040 or Power PC processorMinimum 33Mhz8 MB RAM (5MB free)

. Color Monitor (minimum 640 x480, 256 colors)Double Speed CD-ROMSystem 7.1 (or later)

. Nlouse and keyboard

Software Requirements (included)Apple QuickTime version 2.0Apple Quicklime PowerPlug (for Power PC only)Apple Sound Manager version 3.1 (Extension)

A new CD-ROM from recipients of the Presidential Design Award for Excellence in Multimedia presented by President Clinton.

0"GeoMedia provides innovative tutorials, high quality imagery, and is anexcellent supplement to earth science curricula as found in theNational Science Education Standards."

Dr. M. Frank Watt IretonExecutive Advisor, National Earth Science Teachers

Association (NESTA);Manager of Pre-College Educational Programs,

American Geophysical Union (AGU)

BEST COPY AVAILAB

"GeoMedia is the kind of disc I would like to take with me on vacation! Itis a beautifully done CD-ROM, with high-quality sound, color, animations,factual material, study guides and activity sheets. It would be a verynice addition to anyone's CD-ROM collection."

Susan KinnellCo-Author of CD-ROMs for Schools

"GeoMedia is wonderful! It will greatly enhance our earth-sciencecurriculum.'

Katie O'SullivanComputer Lab Teacher, Mission Bay Montessori Academy

70

n earthly interactive experienceA N EW CD-ROM FROM INTERNETWORK MEDIA AND THE U.S. GEOLOGICAL SURVEY

(9/92)

U.S. DEPARTMENT OF EDUCATIONOffice of Educational Research and Improvement (OERI)

Educational Resources Information Center (ERIC)

NOTICE

REPRODUCTION BASIS

I ERIC1

This document is covered by a signed "Reproduction Release(Blanket)" form (on file within the ERIC system), encompassing allor classes of documents from its source organization and, therefore,does not require a "Specific Document" Release form.

This document is Federally-funded, or carries its own permission toreproduce, or is otherwise in the public domain and, therefore, maybe reproduced by ERIC without a signed Reproduction Releaseform (either "Specific Document" or "Blanket").