世界地理——地球的结构与板块构造英文版

TheStructureoftheEarthandPlateTectonicsStructureoftheEarth•TheEarthismadeupof3mainlayers:–Core–Mantle–CrustInnercoreOutercoreMantleCrustTheCrust•Thisiswherewelive!•TheEarth’scrustismadeof:ContinentalCrust-thick(10-70km)-buoyant(lessdensethanoceaniccrust)-mostlyoldOceanicCrust-thin(~7km)-dense(sinksundercontinentalcrust)-youngHowdoweknowwhattheEarthismadeof?•Geophysicalsurveys:seismic,gravity,magnetics,electrical,geodesy–Acquisition:land,air,seaandsatellite–Geologicalsurveys:fieldwork,boreholes,minesWhatisPlateTectonics?•Ifyoulookatamapoftheworld,youmaynoticethatsomeofthecontinentscouldfittogetherlikepiecesofapuzzle.PlateTectonics•TheEarth’scrustisdividedinto12majorplateswhicharemovedinvariousdirections.•Thisplatemotioncausesthemtocollide,pullapart,orscrapeagainsteachother.•EachtypeofinteractioncausesacharacteristicsetofEarthstructuresor“tectonic”features.•Theword,tectonic,referstothedeformationofthecrustasaconsequenceofplateinteraction.WorldPlatesWhataretectonicplatesmadeof?•Platesaremadeofrigidlithosphere.Thelithosphereismadeupofthecrustandtheupperpartofthemantle.Whatliesbeneaththetectonicplates?•Belowthelithosphere(whichmakesupthetectonicplates)istheasthenosphere.PlateMovement•“Plates”oflithospherearemovedaroundbytheunderlyinghotmantleconvectioncellsPracticalExercise1Supercontinents!Whathappensattectonicplateboundaries?•Divergent•Convergent•TransformThreetypesofplateboundary•Spreadingridges–AsplatesmoveapartnewmaterialiseruptedtofillthegapDivergentBoundariesAgeofOceanicCrustCourtesyof•IcelandhasadivergentplateboundaryrunningthroughitsmiddleIceland:Anexampleofcontinentalrifting•Therearethreestylesofconvergentplateboundaries–Continent-continentcollision–Continent-oceaniccrustcollision–Ocean-oceancollisionConvergentBoundaries•Formsmountains,e.g.EuropeanAlps,HimalayasContinent-ContinentCollisionHimalayas•CalledSUBDUCTIONContinent-OceanicCrustCollision•Oceaniclithospheresubductsunderneaththecontinentallithosphere•Oceaniclithosphereheatsanddehydratesasitsubsides•Themeltrisesformingvolcanism•E.g.TheAndesSubduction•Whentwooceanicplatescollide,onerunsovertheotherwhichcausesittosinkintothemantleformingasubductionzone.•Thesubductingplateisbentdownwardtoformaverydeepdepressionintheoceanfloorcalledatrench.•Theworldsdeepestpartsoftheoceanarefoundalongtrenches.–E.g.TheMarianaTrenchis11kmdeep!Ocean-OceanPlateCollision•WhereplatesslidepasteachotherTransformBoundariesAbove:ViewoftheSanAndreastransformfaultPracticalExercise2WherewilltheUKbein:1,000years?1,000,000years?1,000,000,000years?…what’stheconnection?VolcanoesandPlateTectonics…VolcanismismostlyfocusedatplatemarginsPacificRingofFire-Subduction-Rifting-HotspotsVolcanoesareformedby:PacificRingofFireHotspotvolcanoes•HotmantleplumesbreachingthesurfaceinthemiddleofatectonicplateWhatareHotspotVolcanoes?Photo:TomPfeiffer/…what’stheconnection?EarthquakesandPlateTectonics…•Aswithvolcanoes,earthquakesarenotrandomlydistributedovertheglobe•Attheboundariesbetweenplates,frictioncausesthemtosticktogether.Whenbuiltupenergycausesthemtobreak,earthquakesoccur.FigureshowingthedistributionofearthquakesaroundtheglobeWheredoearthquakesform?FigureshowingthetectonicsettingofearthquakesPlateTectonicsSummary•TheEarthismadeupof3mainlayers(core,mantle,crust)•OnthesurfaceoftheEartharetectonicplatesthatslowlymovearoundtheglobe•Platesaremadeofcrustanduppermantle(lithosphere)•Thereare2typesofplate•Thereare3typesofplateboundaries•VolcanoesandEarthquakesarecloselylinkedtothemarginsofthetectonicplates