BeforeWatching

ProgramovervieW

NOVApresentsthestoryofthegreatestfloodeverfoundinthegeologicrecordandthegeologistwhowentagainstprevaiingtheoriestoexplainthatthefloodhadoccurred.

Theprogram: •reviewsgeologistJHarlenBretz’sradicaltheory—firstproposed

in1923—thatamassivefloodformedsomeofthePacific Northwest’sunusualgeologicfeatures.

•presentstheevidencecollectedbyBretzduringhisresearch, includingtheexistenceoftheChanneledScablandandthedry waterfalls,potholes,anderraticswithinthescablands.

•explainsthat,atthetime,mostscientistsbelievedtheNorthwest’s geologicalfeatureswerecreatedthroughgradualerosiveprocesses; thescientistsfollowedthetheoryofuniformitarianism,whichruled outsuddencatastrophiccreationsoflandscapes.

•recountsthedifficultyfacedbyBretzasheworkedtoconvincethe scientificcommunityofhistheory.

•reportsthekeyroleofJosephThomasPardee,thegeologistwho foundevidenceforanenormousbodyofglacialmeltwaterthat couldhaveprovidedtheflood’ssourceofwater.

•describeshowPardeetheorizedthatalobeoftheCordilleranice sheetdammedtheClarkForkRiver,forminganicebarrierthat eventuallywalledoffalakedescribedinsizeas“aninlandsea.”

•recreateswhatmighthavehappenedwhenthelake’swater eventuallybreachedtheicedam,allowingGlacialLakeMissoulato floodwestward.

•revealsevidenceindicatingthatthefloodBretztheorizedmayhave beenonlyoneofmanythatrepeatedlysweptthroughtheregion.

1 HavestudentslocateWashington,Oregon,Idaho,andMontanaonaU.S.mapthatdisplayslandforms.Whatdotheynoticeaboutthegeologicalfeaturesofthefourstates?Havestudentsfollowthevalleysystemsknownasdrainages.Dotheylinktogether?Dotheyleadinaparticulardirection?ThenhavestudentslocateMissoulaandthewestflankoftheRockyMountainsandtracethedrainagesofthisarea.

2Glaciersareoftenreferredtoas“riversofice.”Askstudentswhattheyknowaboutglaciers.Havestudentseverseenaglacier?Inwhichregionsoftheworlddostudentsthinktheywouldbelocated?WhereintheUnitedStates?Howaretheyformed?Defineglaciersforstudentsandreviewsomefactsaboutthem(see Background on page 2 for more information).

1 JHarlenBretz’stheorieswereatfirstdismissedbyhispeers.Askstudentstociteotherscientistswhoseideaswereinitiallyrejected.Whatweretheobstaclesthatthosescientistsfaced?Howdotheycom-paretotheobstaclesBretzfaced?

2TohelpstudentsunderstandmoreaboutEarth’siceages,havethemcreateatimelinethatincludestheiceagesthatoccurredduring1)thelateProterozoic(betweenabout800and600millionyearsago),2)thePennsylvanianandPermian(betweenabout350and250millionyearsago),and3)thelateTertiaryandQuaternaryperiodsoftheCenozoicera(thepast4millionyears).Togivethemadditionalcontext,havestudentsincludetheageofdinosaursandtheascentofhumansontheirtimelines.

afterWatching

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MysteryoftheMegaflood

novateacher’sguidewww.pbs.org/nova/megaflood

tapingrights:Canbeuseduptooneyearaftertheprogramistapedofftheair.

originalbroadcast:september20,2005

cLassroomactivitY

mYsterYofthemegafLood

activitysummaryStudentswilluseeverydayitemsandspeedstodescribethedimensionsofamassivefloodthatoccurredinthePacificNorthwestneartheendofthelasticeage.

materialsforteacher•meterstick•yardstick

materialsforeachteam•copyofthe“HowBigIsThat?”studenthandout•copyof“TheSpokaneFlood”studenthandout•copyofthe“ComparisonItemsList”studenthandout•calculator•accesstoprintandInternetresources

BackgroundAglacierisalargemassofperennialicethatisformedwhensnowflakespackdownandrecrystallizeassolidice.Althoughiceappearsasahardsolid,glaciersflowslowlydownslopeundertheirownweight.Likeariver,aglacierpicksupandcarriesrockparticlesofallsizes.Astheglaciermoves,theparticlesaredepositedandaccumulatedinmoundscalledmoraines.Inaddition,glacierscanshrinkandgrowinresponsetoclimatechanges.Thesechangesoccurovertens,hundreds,andeventhousandsofyears.

Glaciersexistonallsevencontinents.About10percentoftheworld’slandiscoveredwithglaciers,mostofwhicharefoundnearthepoles.Onetypeofglacierisfoundonlyinpolarregionsoftheworldorathighaltitudes.Calledpolarglaciers,thesetypesofglaciersmostoftencreateicebergs,whichareformedwhenapieceofglacierbreaksofftofloatinthesea.MostU.S.glaciersarefoundinAlaska.TheBeringGlacierinAlaskaqualifiesasNorthAmerica’slongestglacier,measuring204kilometerslong.

Studentswillbeableto:

• demonstratehowwell-knownitems canserveastoolsfornonstandard measurement.

• calculatelength,width,height,and speedofdifferentfeaturesrelated totheSpokaneFlood.

LearningoBjectives

Video is required for this activity.

� novateacher’sguidewww.pbs.org/nova/megaflood

The“HowBigIsThat?”activityalignswiththefollowingPrinciplesandStandardsforSchoolMathematics(seestandards.nctm.org/document/index.htm).

GRADES3–5mathematicsstandardMeasurement

GRADES6–8mathematicsstandardMeasurement

standardsconnection

classroomactivityauthor

DevelopedbyJamesSammonsandWGBHEducationalOutreachstaff.Sammonshastaughtmiddleandhighschoolsciencefor30years.HisteachingpracticeshavebeenrecognizedbytheNationalScienceTeachersAssociation,theSoilConservationService,andtheNationalAssociationofGeoscienceTeachers.

mYsterYofthemegafLood �

ProcedureParti1 Largedimensionscanbedifficulttograsp.Oftenlargedimensions

aremorecomprehensiblewhenlikenedtowell-knownobjects.Studentsinthisactivitywilldevelopwaystorepresentthedimensionsassociatedwithamassivefloodeventthattookplacesometimebetween16,000and12,000yearsagoinwhatisnowWashingtonState.

2 Themeasurementsinthisactivityarerepresentedinmeters.TohelpstudentsunderstandthedifferencebetweenstandardandInternationalSystemofUnits(SI)measurements,holdupthemeterstickandyardsticktogether.Howdotheydifferinlength?Howmanymeterstickswouldreachtheceiling?Howmanyyardsticks?(Teacherswhowouldliketodotheactivityinstandardunitscanhavestudentsconvertthemeasurementstostandardpriortodoingtheactivity.)

3 Next,askstudentswhichdistancesareeasiertoimagine: •275metersoralmostthreefootballfields? •4,725kilometersorthedistancebetweenNewYorkand

SanFrancisco? Moststudentswouldchoosethesecondmeasurementinboth

examplesbecausethosedimensionsaremoreeasilyvisualizedthanthelargenumericalmeasurement.

4 Organizetheclassintoteamsandprovideeachteamwithcopiesofthestudenthandouts.Reviewwithstudentstheactivityinstructionslistedonthe“HowBigIsThat?”handout.Discusswithstudentswhyitcanbehelpfultousenonstandardformsofmeasurementtodescribesomething.(It may be easier to communicate the meaning of a standard measurement through comparison with commonly known objects.)Whenshouldnonstandardformsofmeasurementbeused?(Nonstandard forms of measurement can be useful when communicating large measurements to a non-scientific audience.)Whenarenonstandardformsofmeasurementlessuseful?(Nonstandard forms of measurement are generally estimates and do not provide the mathematical accuracy that science often requires.)

5 FirsthavestudentscategorizetheComparisonItemsListintothefollowingfivecategories:length,height/depth,area,volume,andspeed.Thenhavestudentsread“TheSpokaneFlood”descriptionandhighlighteachofthemeasurementswithinit.Divideupthemeasurementsinthereadingamongteams(see Activity Answer on page 5 for a list of measurements that appear in the story). Makesurethatthesamesetofmeasurementsisassignedtomorethanoneteam.

novateacher’sguidewww.pbs.org/nova/megaflood

cLassroomactivitY(cont.)

mYsterYofthemegafLood

6 HaveeachteamchooseitemsfromtheComparisonItemsListtorepresenttheteam’sassignedmeasurements.HaveteamsperformthecalculationsnecessarytocreatenewrepresentationsofthemeasurementinthereadingintoitemstheyhavechosenfromtheComparisonItemsList.

7 Helpstudentswithcalculationsasnecessary.Convertinglength, height/depth,andspeedaresimpleproportions—somanyoftheseequalsomanyofthose.Studentsmayneedassistanceconvertingareaandvolume,however.Forexample,althoughthereare3feetinayard,thereare9cubicfeetinacubicyard(3feet•3feet•3feet=9feet3).Studentsmaybenefitfromabriefrefresheraboutfindingareaandvolume: a=l•w v=l•w•h

8 AftereachteamusestheitemsfromtheComparisonItemsListtocreateanewrepresentationofitsassignedmeasurements,haveteamsthathavedonethesamemeasurementsfromthereadingpairofftochecktheirresultsanddiscusstheirchoices.

9 Askallteamstoreporttheirequivalentmeasurements.Discussandworkoutanydiscrepanciesindifferingresults.

Partii

1 Holdaclassdiscussionaboutothercomparisonitemsthatmightbegoodtousetobringmeaningtothelargefloodmeasurements.Recordtheseontheboard.Assignteamsitemsfromthenewlycreatedclasscomparisonitemslist.

2 HaveteamsuseprintandInternetresourcestofindthemeasurementsforthenewcomparisonitemstheyhavebeenassigned.Thenhavestudentsconverttheiroriginalassignedmeasurementsfromthereadingtothenewcomparisonitemstheyhaveresearched.

3 Whenallteamshavefinished,haveeachteamreportitsrepresentationsusingthenewcomparisonitemslistcreatedbytheclass.Recordunusualorcontroversialrepresentationsontheboard.Onceallteamshavereported,haveaclassdiscussionabouttheresults.Whichonesaremostcomprehensible?Why?Whataresomecommonfeaturesofgoodanalogies?

4 Asanextension,havestudentsresearchthemeasurementsofthesevenwondersoftheancientworldanddevelopwaystorepresenttheminmorecomprehensibleterms.

novateacher’sguidewww.pbs.org/nova/megaflood

cLassroomactivitY(cont.)

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activitYansWer

mYsterYofthemegafLood

flooddimension newrepresentation comparisonitem

glacier

height:762m twiceashighas theEmpireStateBuilding(381m)

Lakemissoula

depth:610m almosttwiceasdeepas theEiffelTower(321m) theheightof

area:7,770sqkm slightlylargerthantheareaof Delaware(6,447sqkm)

volume:2,084cukm morethanfourtimeslargerthan LakeErie(483cukm)

flood

length traveled: morethantwice NewYorkCitytoWashingtonD.C.842km thedistancefrom (386km)

area covered: almosthalftheareaof Maine(91,700sqkm)41,440sqkm

height at tallest: almostoneandahalftimes theWashingtonMonument244m(170m) theheightof

maximum flow rate: morethan350timesthe the1993MississippiRiverflood,40cukm/hr flowrateof peakflowrate(0.11cukm/hr)

grandcouleecanyon

length:80km almosttwicethedistanceof astandardmarathonrace(42.2km)

width:10km almostfourtimesthelengthof SanFrancisco’sGoldenGateBridge (2.7km)

height:274m morethanoneandahalf theWashingtonMonument(170m) timesashighas

dryfalls

height:107m astackofabout11 two-storyhouses(each10m)

width:4.8km aboutsixtimeswiderthan NiagaraFalls(HorseshoeFallsonly)(792m)

camasPrairiehills

height:11m ashighas acommonutilitypole(11m)

width between hills: widerthansixlengthwise tenniscourts(23.8m)upto152m

area:16sqkm abouthalfthesizeof Chicago’sO’HareAirport(28.3sqkm)

flood velocity : almosttwoandahalftimes aworld-classsprinter(36.9km/hr)through85km/hr fasterthan

Wallulagap

daily amount almost65timesmorethanthe 1993MississippiFlood,peakflowratethrough:167cukm (0.11cukm/hr)

LinksNOVA—MysteryoftheMegafloodwww.pbs.org/nova/megaflood

Read what one geologist has to say about megafloods, discover what Glacial Lake Missoula was like before it burst, use an interactive map to explore the scablands, and test your hunches about the earthly forces that made eight super structures.

ABriefIntroductiontotheIceAgeFloodswww.iceagefloodsinstitute.org/

floods.html

Provides information on how the Pacific Northwest ice floods occurred and how scientists came to understand what happened, as well as links to additional resources.

BooksthechanneledscablandsofeasternWashingtonbyPaulL.WeisandWilliamL.Newman.EasternWashingtonPress,1989.Looks at J Harlen Bretz’s theory that the scablands were formed by a giant flood, and Bretz’s eventual vindication after years of disbelief by fellow geologists.

glacialLakemissoulaanditshumongousfloodsbyDavidD.Alt.MountainPress,2001.Describes Glacial Lake Missoula and traces the periodic floods’ routes across northern Idaho, the Columbia Plateau, and down the Columbia River to the Pacific Ocean.

LinksandBooks

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Analogiescanbeusefultogivemeaningtolargequantities.HowMuchIsaMillion?,byDavidM.Schwartz,isachildren’sbookthatexploresthistechnique.“AbillionkidswouldmakeatowerthatwouldstanduppasttheMoon,”isoneexamplefromthebook.HerearehowsomeoftheitemsfromtheComparisonItemsListrelatetothedimensionsinthefloodstory.

novateacher’sguidewww.pbs.org/nova/megaflood©2005WGBHEducationalFoundation

MajorfundingforNOVAisprovidedbyGoogleandBP.AdditionalfundingisprovidedbytheHowardHughesMedicalInstitute,theCorporationforPublicBroadcasting,andpublictelevisionviewers.

MysteryoftheMegafloodStudentHandout

HowBigIsThat?

Sometimebetween16,000and12,000yearsago,amassivefloodinthePacificNorthwestcarvedoutmajorlandformsacrossmuchofWashingtonStateandpartofnorthernOregon.Thefloodcoveredalmost42,000squarekilometersandatitscreststood244metershigh.Buthowfarandhighisthat?Inthisactivityyouwilllookatdifferentwaystounderstandthesemeasurements.

Procedure

Parti1 Prepareafive-columntablebywritingthefollowing

measurementcategoriesatthetopofeachcolumn: •length(meters/kilometers) •height/depth(meters/kilometers) •area(squaremeters/kilometers) •volume(cubicmeters/kilometers) •speed(kilometersperhour)2 Carefullyreviewtheitemsonyour“Comparison

ItemsList”handout.Completethetablebywritingeachitemonitsownrowunderthecolumnheadingtowhichitbestbelongs.

3 ReadthedescriptionabouttheIceAgefloodprovidedonyourhandoutcalled“TheSpokaneFlood.”Highlightanydimensionsthatfitanyofthemeasurementcategorieslistedinyourtable.

4 Afteryouhavehighlightedallthedimensionsinthereading,yourteacherwillassignsomeofthesemeasurementstoyourteamtocomparetothesizeofotheritems.

5 Convertthemeasurementsassignedtoyourteamsothattheyaremoremeaningful.Selectanitemfromthecomparisonitemtableyoupreparedinstep1.

Performthecalculationsnecessarytomakeyournewmeasurementrepresentativeofthemeasurementinthedescriptionabouttheflood.

6 Foreachassignedmeasurement,recordthecomparisonitemyouchoseanddescribewhyyouthinkthenewmeasurementismoremeaningfulthantheoriginal.

7 Whenyouaredonewithyourcalculations,compareyourresultswithanotherteamthatwasworkingwiththesamemeasurementsetasyours.Workwithotherteammemberstoprepareanexplanationofbothteams’thinkingaboutitemsforwhichyouchosedifferentnewmeasurements.Reportyourresultstotheclass.

Partii

1 Yourteacherwillhelpyourclassdevelopalistofnewcomparisonitemsthatyoucanusetorepresentthemeasurementsfoundintheflooddescriptionreading.

2 UseprintandInternetresourcestoresearchthemeasurementsoftheclasscomparisonitemssothatyoucancalculatenewrepresentationsofthemeasurementswithinthefloodreading.Shareyourresultswithclassmembers.

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Duringoneofthemostrecenticeagesabout17,000yearsago,icesheetsthousandsoffeetthickcoveredwhatisnowsouthernBritishColumbia.AlobefromtheCordilleranicesheetcreptintotheIdahopanhandleandblockedtheClarkForkRiverwithanicedammorethan762metershigh.Watermeltingfromtheglacierfurthertothenorthbackedupbehindtheicedam,formingGlacialLakeMissoula.Attheicedam,thelakereachedadepthof610metersandcoverednearly7,770squarekilometersofwesternMontana.Itcontained2,084cubickilometersofwater.

Theclimatewarmed.Theweakeningicedambasereachedapointwhereitcouldnolongerresisttheincreasingwaterpressurebehindit.Catastrophically,theicedamrupturedandthegreatestfloodinrecordedgeologicalhistorybegan.Waterrushedfromtheicedamwestwardat40cubickilometersperhour.UponreachingaplateauineasternWashington,thewaterspread,carvingouttheChanneledScabland.Oneofthefeaturesitcreatedthereisthepresent-dayGrandCouleecanyon,an80-kilometerlongtrenchupto10kilometerswidewithsteepwallsofbasaltupto274metershigh.

Rushingwateralsocreatedpresent-dayDryFalls,5.6kilometerswidewithadropofmorethan122meters.Atitsheight,thefloodwas244metershigh.ItformedtheCamasPrairie’srollinghills,eachupto11metershighandspaced152metersapart,coveringanareaof16squarekilometers.ThewatertoreacrosstheCamasPrairieattherateof85kilometersperhour.

BythetimeittraveledthroughthenarrowWallulaGap,itwasflowingat167cubickilometersperday.BythetimethetorrentreachedthePacificOcean,ithadtraveled966kilometersandleftitsmarkacross41,440squarekilometersofland.Asincredibleasthisseems,thescientistwhofirsttheorizedthisflood,JHarlenBretz,believeditoccurredmanytimesastheglaciermoveddownandreformedtheicedamaftereachbreakthroughbylakewaters.

TheSpokaneFloodMysteryoftheMegafloodStudentHandout

SourcescataclysmsofthecolumbiabyJohnEliotAllenandMarjorieBurns.TimberPress,1986.

thechanneledscablandsofeasternWashingtonbyPaulL.WeisandWilliamL.Newman.EasternWashingtonPress,1989.

WASHINGTON

CordilleranIceSheet

ClarkForkRiver

MONTANA

OREGON IDAHO

WallulaGap

ChanneledScabland

GlacialLakeMissoula

CamasPrairieHills

DryFalls

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1980mountst.helensinitialdebrissurge=500kilometers/hour

1993mississippiriverflood,peakflowrate=.11cukilometers/hour

chicago’so’hareairport=28.3squarekilometers

delaware=6,447squarekilometers

eiffeltower=321meters

empirestatebuilding=381meters

footballfield(notincludingendzones)=4,504squaremeters

goodyearblimp=5,740cubicmeters

highestpostedinterstatelimit(texas,2005)=129kilometers/hour

hmsTitanic=232,000cubicmeters(tankerequivalent)

Lakeerie=483cubickilometers

Lakesuperior=12,230cubickilometers

maine=91,700squarekilometers

marathonrace,standard=42.2kilometers

minimumhurricane=121kilometers/hour

mississippiriverdailyoutput=1.4cubickilometers

mississippiriver,northernminnesotatoneworleans=3,705kilometers

mounteverest=8,850metershigh

newYorkcitytoWashington,d.c.=386kilometers

niagarafalls(horseshoefallsonly)=792meterswide

niagarafalls(horseshoefallsonly)=51metershigh

ohio=116,500squarekilometers

Peakofatwo-storyhouse=10metershigh

rhodeisland=2,707squarekilometers

sanfrancisco’sgoldengateBridge,shoretoshore=2.7kilometers

semi-trucktrailer(15meters)=102cubicmeters

spaceshuttleshortlyafterenteringatmosphere =28,200kilometers/hour

tenniscourt,betweenbaselines=23.8meters

texas=713,300squarekilometers

World-classsprinter,hundredmeterdash (asafalPowell,2005)=36.9kilometers/hour

utilitypole,common=11metershigh

Washingtonmonument=170metershigh

MysteryoftheMegafloodStudentHandout

ComparisonItemsList

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