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文档分类:高等教育

earthlearningidea - http - http.pdf


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earthlearningidea - http - http.pdf
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Thebackup: Title:Grindingandgouging Subtitle:Howmovingicecangrindawayrocks Topic:Thisactivitycanbeincludedinteachingthe rockcycle;wearingawayofrocks,erosionbyice Agerangeofpupils:10-14years pleteactivity:10minutes es:Pupilscan: ?explainthaticealonewillnotscratchrock; ?demonstratethaticecarryingsedimentwillscratch rock; ?realisethaticewillscrapeanysoilandweathered, loosematerialfromthesurfaceoftheunderlying rock; ?workoutthepossibledirectionoficemovement; ?showthatotherevidenceisneededtodetermine theactualdirectionoficemovement; ?explainhowavalleyglaciercoulderodeadeep,U- shapedvalley,givenenoughtime. Earthlearningidea-/ 1 Grindingandgouging Howmovingicecangrindawayrocks ……………………………………………………………………………………………………………………………………. Demonstratehowice,averysoftsubstance,can grindrocksawaybyrubbingicecubesoverpainted wood. Askthepupils: ?whatwillhappenwhentheyrubacleanicecube onthepieceofpaintedwood? ?whatwillhappenwhentheyrubasand-coveredice cubeonthepieceofpaintedwood? Carryouttheactivitybyaskingthepupilstoruba cleanicecubeoverthewood,pressingdownashard aspossible.Next,askthemtopressanicecubeon tosomeloosesandinadishforabout15seconds andthenrubthisoverthewood.Aretheresultsas predicted? Askthepupils: ?whyaretherescratchmarksontherockinthe phototakeninGlacierNationalPark? ?howcanthedirectionofthescratchmarksbe explained? ?The?oodedU-shapedvalleyinthephotoof GeirangerFjordwascarvedbyice.Howcouldthis possiblyhavehappened? ViewofGeirangerFjord,Norway Photo:ChrisKing Glacialstriations,GlacierNationalPark,Montana,USA CourtesyUSGeologicalSurvey Photo:E.Devon Context: ?Whathappenswhenacleanicecubeisrubbedon apieceofpaintedwood?Icealonewillnotscratch thepaint. ?Whathappenswhenasandyicecubeisrubbedon apieceofpaintedwood?Thepaintwillbe scratchedofffairlyeasily. ?Whyaretherescratchmarksontherockinthe photo?Movingice(aglacier)erodesmaterialofall shapesandsizesfromthevalley?oorasitmoves downhill.Themovingglacieractsratherlikea bulldozer,strippingawayanythingthatisloose abovetheunderlyingrock.Someoftheeroded esembeddedinthebottomofthe glacierandsoscrapesalongthenewly-exposed rockbeneaththeiceandleavesbehindline- shapedscratchmarks,oftencalledglacial striations. ?Howcanthedirectionofthescratchmarksbe explained?Thedirectionofthescratchmarks givesanindicationofthetrendofflowofthe glacier(itcouldhaveflowedineitherdirection,in thisphoto,eitherupordownthepicture).Ifyou wantedtoknowwhichofthetwodirectionsit flowedin,youwouldneedtolookforother evidence,suchasthegeneralslopedirectionof thevalleyorthedirectioninwhicherraticboulders havebeenmovedfromtheirsource. ?HowwastheU-shapedvalleyinthephotocarved byice?Avalleyglacierarmouredwithboulders andsand,carvedthisvalleyasitgrounditsway overtherockbeneath.Sincevalleyglacierserode boththesidesandbaseofthevalleystheyflow through,glacier-carvedvalleyshavetypicalU- shapes,liketheoneinthephoto.Thisonewas eafjord.In contrast,river-erodedvalleyshaveV-shapes (sincemostoftheerosion 内容来自淘豆网www.taodocs.com转载请标明出处.