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1、Listening DATINGMETHODS 1 Listentothetapeandfillthelayersinthe wastepaperbasket diagrambelow yogurtpots orangeskin wastepaper usedenvelopes AnswerkeyforExercise2 Eachlayerlooksdifferentastheyareuncovered soyoucantellwhereonelayerstartsandanotherfinishes Inthewastepaperbasket themostrecentlayeris ano
2、lderlayerisbelowthatandtheoldestlayeris atthetop atthebottom Alllivingthingshave intheirbodies Whentheydie thecarbon ata rate Themethodmeasures ofcarboninbonesorplantsusingradioactivityandcan howoldtheremainsare startstodisappear fixed theamount workout carbon Note Theageofthebuildingdependsonthenum
3、beroflayersitisrestingon Themorelayers themorerecentthebuilding AnswerkeyforExercise3 TheoldestbuildingisBbecauseithasnolayersunderneathit ThesecondoldestbuildingisCbecauseithasonelayerunderneathit ThemostrecentbuildingisbuildingA Ithastwolayersunderneath ZH Howcanyoutellhowoldthebonesarewhenyoufind
4、them LISTENINGTEXT P42 DATINGMETHODS ZhouHepinghascometoaskthearchaeologist RichardLeakey howhedatestheboneshefinds RL Therearetwomainways thefirstuseslayersinthegroundandthesecondusestheradiocarbondating ZH Howdoesthelayermethodwork RL Well manylayersofsoilwereproducedatdifferenttimes Eachtimepeopl
5、ebuildhousesandlive somewhere theymakeanoccupationlayer Eachhasadifferentcolorandtexture ZH Howdoesthathelp RL Lookatthediagraminyourbook Thinkofyourwastepaperbasket Whenyoucameintoworkyouthrewtheorangeskinintoit Later someonethrewtheiremptyyogurtpotsintoit Thensomewastepaperwasadded Finallysomeonet
6、hrewawaysomeusedenvelopes Howmanylayersarethere ZH Therearefourlayers RL Good Nowwhichlayeristhelatest ZH Now letmethink Yes it llbetheoneonthetop whichistheusedenvelopes RL Andwhere stheoldestlayer ZH Atthebottom RL Welldone Whenwefindbonesinlayersofsoil weknowtheyarethesameageasthesoil ZH Isee RL
7、Nowlet sthinkaboutthesecondmethod ZH Iremember It scalledtheradiocarbondatingmethod That sastrangename RL Yes Itusestheradioactivitytomeasuretheamountofcarboninlivingthings Thecarboninadead bodydisappearsatafixedrate Weknowhowlongthistakes sowecanmeasuretheamountofcarbonandworkouthowoldaboneorplanti
8、s ZH That sveryclever Isitveryaccuratetoo RL Therearesomeproblems soyou arealwaysgivenadateplusorminussomeyears Forexample yourbonemaybedatedto10 000yearsagoplusorminus100years Thismeanstheboneisbetween9 900yearsand10 100yearsold ZH Howclever HowoldarethebonesfromtheZhoukoudianCaves RL Theyarebetween250 000and40 000yearsold ZH Perhapswecangoandvisitthesitetogethersometime RL Ofcourse Wheneveryoulike
