2 第二讲 Plate Tectonics 1

第二讲PlateTectonicsprefaceThesignificance板块构造的科学意义Theplatetectonicsnotionhasprofoundlychangedthewayweviewtheearth.Intheearly1960s,theemergence（出现）ofthetheoryofplatetectonicsstartedarevolutionintheearthsciences.Theplatetectonicstheoryistheresultoftheprogressofscience.Thekeyofcourse课程要点1.HeregivesabriefintroductiontotheconceptofplatetectonicsandcomplementsthevisualandwritteninformationinThisDynamicPlanet2.Herehighlights（强调）someofthepeopleanddiscoveriesthatadvancedthedevelopmentofthetheoryandtracesitsprogresssinceitsproposal.3.Themanyaspectsstillcontinuetoconfound（混淆）andchallengescientists.Theearth-sciencerevolutionlaunchedbythetheoryofplatetectonicsisnotfinished.4.Platetectonicsisarelativelynewscientificconcept,introducedmorethan30yearsago.5.ThetheoryhasunifiedthestudyoftheEarthbydrawingtogethermanybranchesoftheearthsciencespaleontology(thestudyoffossils)seismology(thestudyofearthquakes)Petrologyandgeochemistry6.Ithasprovidedexplanationstoquestionsthatscientistshadspeculateduponforcenturies–whyearthquakesandvolcaniceruptionsoccurinveryspecificareasaroundtheworld,andhowandwhygreatmountainrangesliketheAlpsandHimalayasformed成矿动力学过程的解释1.Historicalperspective（回顾）1.1platetectonicsandcontinentaldriftcontinentaldrift-theforerunnertothetheoryofplatetectonicsThetheoryofplatetectonicsstatesthattheEarth'soutermostlayerisfragmentedintoadozenormorelargeandsmallplatesthataremovingrelativetooneanotherastheyrideatop(在…顶上)hotter,moremobilematerial（mantle）.InternalstructureofEarthironcoremantleSolidmesospherecrustrigidlithospherephysicalpropertieschemicalpropertiesplasticasthenospheremesospherecrustmantlelithosphereasthenosphereliquidoutercoresolidinnercore8-75km100-200km350-500km软流圈下地幔supercontinentPangaeaBeforetheadvent（出现）ofplatetectonics,however,somepeoplealreadybelievedthatthepresent-daycontinentswerethefragmentedpiecesofpreexistinglargerlandmasses(supercontinents).Thediagramsbelowshowthebreak-upofthesupercontinentPangaea（联合古陆）(meaningalllandsinGreek),whichfiguredprominentlyinthetheoryofcontinentaldrift--theforerunnertothetheoryofplatetectonics.Accordingtothecontinentaldrifttheory,thesupercontinentPangaeabegantobreakupabout225-200millionyearsago,eventuallyfragmentingintothecontinentsasweknowthemtoday.全球岩石圈共分为六大板块——太平洋板块、亚欧板块、南极洲板块、非洲板块、美洲板块、印度洋板块VolcanismVolcanismEarthquake板块构造的动力学机制1.2ContinentalDrift-proposed1596—Ortelius:Activenotionofcontinents—surfacedThebeliefthatcontinentshavenotalwaysbeenfixedintheirpresentpositionswassuspectedlongbeforethe20thcentury;thisnotionwasfirstsuggestedasearlyas1596bytheDutchmapmakerAbrahamOrteliusinhisworkThesaurusGeographicus.OrteliussuggestedthattheAmericasweretornawayfromEuropeandAfrica...byearthquakesandfloodsandwentontosay:Thevestiges（痕迹）oftherupture（裂开）revealthemselves,ifsomeonebringsforwardamapoftheworldandconsiderscarefullythecoastsofthethree[continents].TheShapeoftheEarth:Mountains•CompressionalSettings:Alps,Himalayas,Andes,andCordilleramountainranges•ExtensionalSettings:EastAfricaValley,RedSea,GulfofAden•Strike-slipSettings:SanAndreasFault,AnatolianFaults1912--LotharWegener--ContinentalDriftOrtelius'ideasurfacedagaininthe19thcentury.However,itwasnotuntil1912thattheideaofmovingcontinentswasseriouslyconsideredasafull-blown(成熟的)scientifictheory--calledContinentalDrift--introducedintwoarticlespublishedbya32-year-oldGermanmeteorologistnamedAlfredLotharWegener.Hecontendedthat,around200millionyearsago,thesupercontinentPangaeabegantosplitapart.In1858,geographerAntonioSnider-PellegrinimadethesetwomapsshowinghisversionofhowtheAmericanandAfricancontinentsmayoncehavefittogether,thenlaterseparated.Left:Theformerlyjoinedcontinentsbefore(avant)theirseparation.Right:Thecontinentsafter(aprés)theseparation.(ReproductionsoftheoriginalmapscourtesyofUniversityofCalifornia,Berkeley.)1.3AlexanderDuToit-Laurasia;GondwanalandAlexanderDuToit,ProfessorofGeologyatJohannesburgUniversityandoneofWegener'sstaunchest(坚定的)supporters,proposedthatPangaeafirstbrokeintotwolargecontinentallandmasses,LaurasiainthenorthernhemisphereandGondwanalandinthesouthernhemisphere.LaurasiaandGondwanalandthencontinuedtobreakapartintothevarioussmallercontinentsthatexisttoday.Accordingtothecontinentaldrifttheory,thesupercontinentPangaeabegantobreakupabout225-200millionyearsago,eventuallyfragmentingintothecontinentsasweknowthemtoday.1.4Wegener'stheorybasement1、ThenotionofAbrahamOrteliusthreecenturiesearlierWegener'stheorywasbasedinpartonwhatappearedtohimtobetheremarkablefitoftheSouthAmericanandAfricancontinents,firstnotedbyAbrahamOrteliusthreecenturiesearlier.2、IdenticalgeologicstructuresandofplantandanimalfossilsalongthecoastalpartsofAfricaandSouthAmericaWegenerwasalsointrigued（兴趣）bytheoccurrencesofunusualgeologicstructuresandofplantandanimalfossilsfoundonthematchingcoastlinesofSouthAmericaandAfrica,whicharenowwidelyseparatedbytheAtlanticOcean.PatternMatchingofGeologicalRecordacrosstheAtlanticTheageofrockunitsgenerallymatchwhenthecontinentsarerotatedbackinposition.Mountainbeltsofsimilaragealsomatchwhe