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1、Listening----DATINGMETHODS1.Listentothetapeandfillthelayersinthe“wastepaperbasket”diagrambelow.yogurtpotsorangeskinwastepaperusedenvelopesThewastepaperbasketAnswerkeyforExercise2MethodHowitworks1.LayersinthegroundEachlayerlooksdifferentastheyareuncovered,soyoucantellwhereon
2、elayerstartsandanotherfinishes.Inthewastepaperbasket,themostrecentlayeris_________,anolderlayerisbelowthatandtheoldestlayeris____________.atthetopatthebottomMethodHowitworks2.Radio-carbondatingAlllivingthingshave______intheirbodies.Whentheydie,thecarbon________________ata__
3、__rate.Themethodmeasures__________ofcarboninbonesorplantsusingradioactivityandcan________howoldtheremainsare.startstodisappearfixedtheamountworkoutcarbonNote:Theageofthebuildingdependsonthenumberoflayersitisrestingon.Themorelayers,themorerecentthebuilding.AnswerkeyforExerci
4、se3:TheoldestbuildingisBbecauseithasnolayersunderneathit.ThesecondoldestbuildingisCbecauseithasonelayerunderneathit.ThemostrecentbuildingisbuildingA.Ithastwolayersunderneath.ZH:Howcanyoutellhowoldthebonesarewhenyoufindthem?LISTENINGTEXT(P42)DATINGMETHODSZhouHepinghascometoa
5、skthearchaeologist,RichardLeakey,howhedatestheboneshefinds.RL:Therearetwomainways:thefirstuseslayersinthegroundandthesecondusestheradiocarbondating.ZH:Howdoesthelayermethodwork?RL:Well,manylayersofsoilwereproducedatdifferenttimes.Eachtimepeoplebuildhousesandlivesomewhere,th
6、eymakeanoccupationlayer.Eachhasadifferentcolorandtexture.ZH:Howdoesthathelp?RL:Lookatthediagraminyourbook.Thinkofyourwastepaperbasket.Whenyoucameintoworkyouthrewtheorangeskinintoit.Latersomeonethrewtheiremptyyogurtpotsintoit.Thensomewastepaperwasadded.Finallysomeonethrewawa
7、ysomeusedenvelopes.Howmanylayersarethere?ZH:Therearefourlayers.RL:Good.Nowwhichlayeristhelatest?ZH:Now,letmethink!Yes,it'llbetheoneonthetop,whichistheusedenvelopes.RL:Andwhere'stheoldestlayer?ZH:Atthebottom.RL:Welldone.Whenwefindbonesinlayersofsoil,weknowtheyarethesameageas
8、thesoil.ZH:Isee.RL:Nowlet'sthinkaboutthesecondmethod.ZH:Iremember.It'scalledtherad
