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UnderstandingEarthChapter8:TheRockRecordandtheGeologicTimeScaleCopyright©2007byW.H.Freeman&CompanyJohnGrotzinger,ThomasH.JordanFrankPressandRaymondSieverFifthEditionUnderstandingEarthChapter8:CConceptsyouwillneedtoknowfortheexamsCHAPTER8GeologicTimeScaleRelativeageAbsoluteagePrincipleoforiginalhorizontalityPrincipleofsuperpositionPrincipleofcross-cuttingrelationahipsUnconformityAngularunconformityDisconformityHalf-lifeGeologicTimeScaleConceptsyouwillneedtoknowGeologistsdifferfromotherprofessionalscientistsintheirviewoftime.Geologistsdealwithperiodsoftimethatgoasfarbackastheoriginoftheuniverse.GeologistsdifferfromotherpBeforewehadtheabilitytoreadthe“atomicclocks”ofnature,geologistsusedtheconceptofrelativeages.Wecanseechangesinthelandscapeovertime.Wecanseeonetypeoforganismreplaceanothertypeoforganismthroughthefossilizedremainsofthesechangesovertime.Beforewehadtheabilitytor地质中的时间尺度课件地质中的时间尺度课件Withtheadventofatomic/radioactivedecaytechniqueswebegantoobtainabsolutedates.AbsolutedatesorageshavespecificnumbersWiththeadventofatomic/radiRelativedatinghasbeendoneinthepastthroughthestudyoflayersofsedimentaryrock(aka“thefieldofstratigraphy”)RelativedatinghasbeendonePrincipleofOriginalHorizontalitysedimentsdepositedinnearlyflatlayers.Cross-beddedlayersarecontainedwithinoverallflatbeds.Iflayersarefaulted(broken)orfoldeditmeansthattheyweredeformedAFTERsedimentsweredeposited.PrincipleofOriginalHorizont地质中的时间尺度课件PrincipleofSuperpositionLowestlayersareolderIfthisisnotso,thenthelayershavebeenoverturnedbytectonicactivity:PrincipleofSuperposition地质中的时间尺度课件Therearelimitationsforusingstratigraphytokeeptimebecause,(1)sedimentationratesarevariablee.g.Mississippicandeposit1mofsedimentin1000yThedeepoceanmaydeposit1mm/1000yearsWeneedtoestimatetimeinanotherwayandbeabletorecognizewhentherepresentationoftimeviasedimentsisincomplete.Paleontologyisthestudyofancientlifefromfossilizedremains.Therearelimitationsforusin地质中的时间尺度课件地质中的时间尺度课件WilliamSmithinthe19thcenturywasanengineerwhonotedthatsimilarrocksindifferentareashadsimilarfossilsandthatdifferentrocktypeshaddifferentfossils.Hemadeacomposite(ideal,pieced-together)stratigraphicsuccessionasinthefollowingfigureWilliamSmithinthe19thcent地质中的时间尺度课件MostofgeologictimegoesunrecordedSometimesNOSEDIMENTisDEPOSITEDoveranintervaloftime(hiatus)Othertimessedimentiserodedaway.Thisishappeninghere:MississippiValleyisfillingwhereasthehighergroundisbeingerodedaway.Mostofgeologictimegoesunr地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件AnunconformityinwhichthelayersaboveanerosionalsurfaceareparalleltothelayersbelowisknownasaDISCONFORMITYAnunconformityinwhichthel地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件Onewayofproducingadisconformityistochangeglobalsea-levelbyglaciationandglacialmelting.Onewayofproducingadisconf地质中的时间尺度课件Cross-cuttingrelationshipsinsedimentaryrocksallowistodatetherelativetimingofeventssuchasfaultingandigneousintrusionCross-cuttingrelationshipsin地质中的时间尺度课件地质中的时间尺度课件TheGeologicTimeScale…..isstillunderconstructionLifebeganonly2500MaTheGeologicTimeScale地质中的时间尺度课件RadioactiveDatingMethodsRadioactiveDatingMethodsMiningUraniumOxideU3O8U-23899.3%,U-2350.7%MillingcrushedsoakedinsulfuricacidYellowCakeU3O8CONVERSION:yellowcakeisheatedtoabout147F,convertedintouraniumhexafluoridegas(UF6).ENRICHMENT:

TheUF6gascentrifugedheavierU-238movesoutsideU-235concentratesinwardConverttoUO2powderNuclearReactors:enriched3-5%U-235NuclearWeapons:enriched90%U-235MiningNuclearReactors:enric地质中的时间尺度课件RubidiumexistRb87isunstableRbhasanaverageatomicweightof~85.5Rb87hasanatomicmass~87Rb87has37protonsand50neutronsinitsnucleusSr87isstableSrhasanaverageatomicweightof~87.62Sr87hasanatomicmass~87Sr87has38protonsand49neutronsinitsnucleusSource:wikipedia11-5-2012RubidiumexistRb87isunstabRb37p+50nSr38p+49n+electronNeutron-------proton+electronRb37p+50nSr38p+49n+electronNe地质中的时间尺度课件地质中的时间尺度课件Alllead,except204Pb(1.4%),istheendproductofacomplexradioactivedecay.ThemostcommonisotopeofLeadis:208Pb52.4%(stable)Alllead,except204Pb(1.4%),TheEND…..FornowTheEND…..FornowUnderstandingEarthChapter8:TheRockRecordandtheGeologicTimeScaleCopyright©2007byW.H.Freeman&CompanyJohnGrotzinger,ThomasH.JordanFrankPressandRaymondSieverFifthEditionUnderstandingEarthChapter8:CConceptsyouwillneedtoknowfortheexamsCHAPTER8GeologicTimeScaleRelativeageAbsoluteagePrincipleoforiginalhorizontalityPrincipleofsuperpositionPrincipleofcross-cuttingrelationahipsUnconformityAngularunconformityDisconformityHalf-lifeGeologicTimeScaleConceptsyouwillneedtoknowGeologistsdifferfromotherprofessionalscientistsintheirviewoftime.Geologistsdealwithperiodsoftimethatgoasfarbackastheoriginoftheuniverse.GeologistsdifferfromotherpBeforewehadtheabilitytoreadthe“atomicclocks”ofnature,geologistsusedtheconceptofrelativeages.Wecanseechangesinthelandscapeovertime.Wecanseeonetypeoforganismreplaceanothertypeoforganismthroughthefossilizedremainsofthesechangesovertime.Beforewehadtheabilitytor地质中的时间尺度课件地质中的时间尺度课件Withtheadventofatomic/radioactivedecaytechniqueswebegantoobtainabsolutedates.AbsolutedatesorageshavespecificnumbersWiththeadventofatomic/radiRelativedatinghasbeendoneinthepastthroughthestudyoflayersofsedimentaryrock(aka“thefieldofstratigraphy”)RelativedatinghasbeendonePrincipleofOriginalHorizontalitysedimentsdepositedinnearlyflatlayers.Cross-beddedlayersarecontainedwithinoverallflatbeds.Iflayersarefaulted(broken)orfoldeditmeansthattheyweredeformedAFTERsedimentsweredeposited.PrincipleofOriginalHorizont地质中的时间尺度课件PrincipleofSuperpositionLowestlayersareolderIfthisisnotso,thenthelayershavebeenoverturnedbytectonicactivity:PrincipleofSuperposition地质中的时间尺度课件Therearelimitationsforusingstratigraphytokeeptimebecause,(1)sedimentationratesarevariablee.g.Mississippicandeposit1mofsedimentin1000yThedeepoceanmaydeposit1mm/1000yearsWeneedtoestimatetimeinanotherwayandbeabletorecognizewhentherepresentationoftimeviasedimentsisincomplete.Paleontologyisthestudyofancientlifefromfossilizedremains.Therearelimitationsforusin地质中的时间尺度课件地质中的时间尺度课件WilliamSmithinthe19thcenturywasanengineerwhonotedthatsimilarrocksindifferentareashadsimilarfossilsandthatdifferentrocktypeshaddifferentfossils.Hemadeacomposite(ideal,pieced-together)stratigraphicsuccessionasinthefollowingfigureWilliamSmithinthe19thcent地质中的时间尺度课件MostofgeologictimegoesunrecordedSometimesNOSEDIMENTisDEPOSITEDoveranintervaloftime(hiatus)Othertimessedimentiserodedaway.Thisishappeninghere:MississippiValleyisfillingwhereasthehighergroundisbeingerodedaway.Mostofgeologictimegoesunr地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件AnunconformityinwhichthelayersaboveanerosionalsurfaceareparalleltothelayersbelowisknownasaDISCONFORMITYAnunconformityinwhichthel地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件地质中的时间尺度课件Onewayofproducingadisconformityistochangeglobalsea-levelbyglaciationandglacialmelting.Onewayofproducingadisconf地质中的时间尺度课件Cross-cuttingrelationshipsinsedimentaryrocksallowistodatetherelativetimingofeventssuchasfaultingandigneousintrusionCross-cuttingrelationshipsin地质中的时间尺度课件地质中的时间尺度课件TheGeologicTimeScale…..isstillunderconstructionLifebeganonly2500MaTheGeologicTimeScale地质中的时间尺度课件RadioactiveDatingMethodsRadioactiveDatingMethodsMiningUraniumOxideU3O8U-23899.3%,U-2350.7%MillingcrushedsoakedinsulfuricacidYellowCakeU3O8CONVERSION:yellowcakeisheatedtoabout147F,convertedintouran

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