地質(zhì)中的時(shí)間尺度

UnderstandingEarthChapter8:TheRockRecordandtheGeologicTimeScaleCopyright?2007byW.H.Freeman&CompanyJohnGrotzinger,ThomasH.JordanFrankPressandRaymondSieverFifthEditionConceptsyouwillneedtoknowfortheexamsCHAPTER8GeologicTimeScaleRelativeageAbsoluteagePrincipleoforiginalhorizontalityPrincipleofsuperpositionPrincipleofcross-cuttingrelationahipsUnconformityAngularunconformityDisconformityHalf-lifeGeologicTimeScaleGeologistsdifferfromotherprofessionalscientistsintheirviewoftime.Geologistsdealwithperiodsoftimethatgoasfarbackastheoriginoftheuniverse.Beforewehadtheabilitytoreadthe“atomicclocks”ofnature,geologistsusedtheconceptofrelativeages.Wecanseechangesinthelandscapeovertime.Wecanseeonetypeoforganismreplaceanothertypeoforganismthroughthefossilizedremainsofthesechangesovertime.Withtheadventofatomic/radioactivedecaytechniqueswebegantoobtainabsolutedates.AbsolutedatesorageshavespecificnumbersRelativedatinghasbeendoneinthepastthroughthestudyoflayersofsedimentaryrock(aka“thefieldofstratigraphy”)PrincipleofOriginalHorizontalitysedimentsdepositedinnearlyflatlayers.Cross-beddedlayersarecontainedwithinoverallflatbeds.Iflayersarefaulted(broken)orfoldeditmeansthattheyweredeformedAFTERsedimentsweredeposited.PrincipleofSuperpositionLowestlayersareolderIfthisisnotso,thenthelayershavebeenoverturnedbytectonicactivity:Therearelimitationsforusingstratigraphytokeeptimebecause,(1)sedimentationratesarevariablee.g.Mississippicandeposit1mofsedimentin1000yThedeepoceanmaydeposit1mm/1000yearsWeneedtoestimatetimeinanotherwayandbeabletorecognizewhentherepresentationoftimeviasedimentsisincomplete.Paleontologyisthestudyofancientlifefromfossilizedremains.WilliamSmithinthe19thcenturywasanengineerwhonotedthatsimilarrocksindifferentareashadsimilarfossilsandthatdifferentrocktypeshaddifferentfossils.Hemadeacomposite(ideal,pieced-together)stratigraphicsuccessionasinthefollowingfigureMostofgeologictimegoesunrecordedSometimesNOSEDIMENTisDEPOSITEDoveranintervaloftime(hiatus)Othertimessedimentiserodedaway.Thisishappeninghere:MississippiValleyisfillingwhereasthehighergroundisbeingerodedaway.AnunconformityinwhichthelayersaboveanerosionalsurfaceareparalleltothelayersbelowisknownasaDISCONFORMITYOnewayofproducingadisconformityistochangeglobalsea-levelbyglaciationandglacialmelting.Cross-cuttingrelationshipsinsedimentaryrocksallowistodatetherelativetimingofeventssuchasfaultingandigneousintrusionTheGeologicTimeScale…..isstillunderconstructionLifebeganonly2500MaRadioactiveDatingMethodsMiningUraniumOxideU3O8U-23899.3%,U-2350.7%MillingcrushedsoakedinsulfuricacidYellowCakeU3O8CONVERSION:yellowcakeisheatedtoabout147F,convertedintouraniumhexafluoridegas(UF6).ENRICHMENT:TheUF6gascentrifugedheavierU-238movesoutsideU-235concentratesinwardConverttoUO2powderNuclearReactors:enriched3-5%U-235NuclearWeapons:enriched90%U-235RubidiumexistRb87isunstableRbhasanaverageatomicweightof~85.5Rb87hasanatomicmass~87Rb87has37protonsand50neutronsinitsnucleusSr87isstableSrhasanaverageatomicweightof~87.62Sr87hasanatomicmass~87Sr87has38protonsand49neutronsinitsnucleusSource:wikipedia11-5-2012Rb37p+50nSr38p+49n+electronNeutron-------proton+electronAlllead,except204Pb(1.4%),istheendproductofacomplexradioactivedecay.ThemostcommonisotopeofLeadis:208Pb52.4%(stable)TheEND…..Fornow9、靜夜四無(wú)無(wú)鄰，荒居居舊業(yè)貧。。。12月-2212月-22Friday,December23,202210、雨中黃黃葉樹(shù)，，燈下白白頭人。。。02:42:2502:42:2502:4212/23/20222:42:25AM11、以我獨(dú)獨(dú)沈久，，愧君相相見(jiàn)頻。。。12月-2202:42:2502:42Dec-2223-Dec-2212、故人江江海別，，幾度隔隔山川。。。02:42:2502:42:2502:42Friday,December23,202213、乍見(jiàn)見(jiàn)翻疑疑夢(mèng)，，相悲悲各問(wèn)問(wèn)年。。。12月月-2212月月-2202:42:2502:42:25December23,202214、他他鄉(xiāng)鄉(xiāng)生生白白發(fā)發(fā)，，舊舊國(guó)國(guó)見(jiàn)見(jiàn)青青山山。。。。23十十二二月月20222:42:25上上午午02:42:2512月月-2215、比比不不了了得得就就不不比比，，得得不不到到的的就就不不要要。。。。。。十二二月月222:42上上午午12月月-2202:42December23,202216、行行動(dòng)動(dòng)出出成成果果，，工工作作出出財(cái)財(cái)富富。。。。2022/12/232:42:2502:42:2523December202217、做前，，能夠環(huán)環(huán)視四周周；做時(shí)時(shí)，你只只能或者者最好沿沿著以腳腳為起點(diǎn)點(diǎn)的射線線向前。。。2:42:25上午午2:42上午午02:42:2512月-229、沒(méi)有有失敗敗，只只有暫暫時(shí)停停止成成功！！。12月月-2212月月-22Friday,December23,202210、很多多事情情努力力了未未必有有結(jié)果果，但但是不不努力力卻什什么改改變也也沒(méi)有有。。。02:42:2602:42:2602:4212/23/20222:42:26AM11、成功就是是日復(fù)一日日那一點(diǎn)點(diǎn)點(diǎn)小小努力力的積累。。。12月-2202:42:2602:42Dec-2223-Dec-2212、世間成事事，不求其其絕對(duì)圓滿滿，留一份份不足，可可得無(wú)限完完美。。02:42:2602:42:2602:42Friday,December23,202213、不不知知香香積積寺寺，，數(shù)數(shù)里里入入云云峰峰。。。。12月月-2212月月-2202:42:2602:42:26December23,202214、意志堅(jiān)強(qiáng)強(qiáng)的人能把把世界放在在手中像泥泥塊一樣任任意揉捏。。23十二二月20222:42:26上上午02:42:2612月-2215、楚楚塞塞三三湘湘接接，，荊荊門(mén)門(mén)九九派派通通。。。。。。十二二月月222:42上上午午12月月-2202:42December23,202216、少少年年十十五五二二十十時(shí)時(shí)，，步步行行奪奪得得胡胡馬馬騎騎。。。。2022/12/232:42:2602:42:2623December202217、空空山山新新雨雨后后，，天天氣氣晚晚來(lái)來(lái)秋秋。。。。2:42:26上上午午2:42上上午午02:42:2612月月-229、楊柳散和風(fēng)風(fēng)，青山澹吾吾慮。。12月-2212月-22Friday,December23,202210、閱讀一切好好書(shū)如同和過(guò)過(guò)去最杰出的的人談話。02:42:2602:42:2602:4212/23/20222:42:26AM11、越是沒(méi)有本本領(lǐng)的就越加加自命不凡。。12月-2202:42:2602:42Dec-2223-Dec-2212、越是是無(wú)能能的人人，越越喜歡歡挑剔剔別人人的錯(cuò)錯(cuò)兒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