板塊漂移學(xué)說(shuō)BrushinguponbasicgeographywillhelpyoulearnPlateTectonicsOnceyouknowyourbasicgeography(continentsandmajormountainranges)andoceanbasinfeatures(MidOceanRidges,OceanicTrenches)youcanLearnthe7majorplatesLearnthetypesofplateboundariesLearnwhythosefeaturesarewheretheyareI.Introduction(cont.)E.ForcesshapingtheEarthatthesurfaceandfromwithin1.SurficialProcessesSolarenergyandgravityshapingthelandscape2.InternalProcessesInternalenergyandforcesthatbuckleandbreakEarth’scrustIfExternalProcessesOnly?Question:If550milliontonsofrockarebrokendownandtransportedtotheseafromtheUnitedStateseachyear,WhyhasourcontinentnotbeenwornflatafterthebillionsofyearsofitsexistenceandWhyhaven’ttheoceansbeenfilledin?MississippiRiverDeltaMississippiRiverDrainageBasinErosion,transport,depositionMississippiRiverDelta1.SurficialProcesses

Resultsofthe“ExternalHeatEngine”WeatheringChemicalandMechanicalBreakdownof

solidrockinto

sedimentsErosionRemovalofrockandsedimentfromsourcebyGravity,wind,water,iceSurficialProcesses(cont.)

Resultsofthe“ExternalHeatEngine”Transportoverlargedistancesbywater,windandice.SurficialProcesses(cont.)

Resultsofthe“ExternalHeatEngine”Depositionoflargeamountsofsedimentinseasandoceans2.InternalEarthProcesses

Resultsofthe“InternalHeatEngine”Evidenceofinternalenergyandforcesworkingonourearth.IntricatelandscapesVolcanoesEarthquakesGeothermalGradients(deeperishotter)AnotherQuestion:Whatisthesourceofallthisenergy?3.FormationofEarthhttp:///projects/planets/planets.htmlBirthoftheSolarSystemNebularTheorynebulacompressesFlatteningofspinningnebulaandcollapseintocentertoformsunCondensationtoformplanets,planetesimal,moonsandasteroidsduringplanetaryaccretionaround4?billionyearsago(Meteoritesareiron-richandrockyfragmentsleftoverfromplanetaryaccretion)/projects/planets/planets.html/~kaufman/ppt/chapter4/sld002.htmOrionNebulaFormationofthePlanetsThemassofthecenterofthesolarsystembegannuclearfusiontoignitethesunTheinnerplanetswerehotterandgaswasdrivenawayleavingtheterrestrialplanetsTheouterplanetswerecoolerandmoremassivesotheycollectedandretainedthegasseshencethe“GasGiants”GasGiantsTerrestrialPlanets/rose/backgrounds.htmlDifferentiationofthePlanetsTherelativelyuniformiron-richprotoplanetsbegantoseparateintozonesofdifferentcomposition:4.6myaHeatfromimpacts,pressureandradioactiveelementscauseiron(andotherheavierelements)tomeltandsinktothecenteroftheterrestrialplanetsThezonesoftheearth’sinteriorFurtherDifferentiationofEarthLighterelementssuchasOxygen,Silicon,andAluminumrosetoformacrustThecrust,whichwasoriginallythinandheavy(ironrichsilicate)Liketoday’sOceaniccrust,Furtherdifferentiatedtoformcontinentalcrustwhichwasthicker,ironpoorandlighterFigure1.7,thezonesoftheearth’sinteriorCompositionofEarthandCrust

Element(Atomic#)

ChemicalSymbol

%ofEarth%ofCrust(byWeight)ChangeinCrustDuetoDifferentiationOxygen(8)O3046.6Increase

Silicon(14)Si1527.7Increase

Aluminum(13)Al<18.1Increase

Iron(26)Fe355.0Decrease

Calcium(20)Ca<13.6Increase

Sodium(11)Na<12.8Increase

Potassium(19)K<12.6Increase

Magnesium(12)Mg102.1Decrease

AllOthers

~81.5

CrustandMantle

LithosphereandAsthenosphereTheuppermostmantleandcrustarerigidsolidrock(Lithosphere)Therestofthemantleissoftbutsolid(Asthenosphere)TheContinentalCrust“floats”ontheuppermostmantleThedenser,thinnerOceanicCrustcomprisestheoceanbasinsFigure1.7,DetailofcrustandMantleTheLithosphereisbrokeninto“plates”(7major,6or7minor,manytiny)Platesthat“ridearound”ontheflowingAsthenosphere

CarryingthecontinentsandcausingcontinentaldriftLitho-

spheric

PlatesPlatesShownbyPhysiographyTypesofPlateBoundaries-Convergent-Divergent-TransformLithosphericPlatesandBoundarytypesThreeTypes

ofPlate

BoundariesDivergent|Convergent|Transforme.g.,PacificNWWhereplatesmoveawayfromeachothertheiron-rich,silica-poormantlepartiallymeltsandDivergent

PlateBoundariesAsthenosphereLithosphereLithosphereSimplifiedBlockDiagramExtrudesontotheoceanfloororcontinentalcrustCoolandsolidifytoformBasalt:Iron-Rich,Silica-Poor,DenseDark,Fine-grained,IgneousRockCharacteristicsof

DivergentPlateBoundariesOceanicCrustMagmaGenerationDivergentPlateBoundaryStress:Tensionalextensionalstrain

Volcanism:non-explosive,fissureeruptions,basaltfloodsEarthquakes:Shallow,weakRocks:BasaltFeatures:Ridge,rift,fissures

LocationsofDivergentPlateBoundaries

Mid-OceanRidgesEastPacificRiseMidAtlanticRidgeMidIndianRidgeMidArcticRidgeFig.1.10(Mid-ArcticRidge)EastPacificRiseMid-AtlanticRidgeIndianRidgeMid-03070150300500DivergentPlateBoundariesRiftingandgenerationofshallowearthquakes(<33km)Depth(km)03370300150500800Fig.19.21Fig.19.22RiftValleyPassivecontinentalshelfandriseRiftValleyE.g.,RedSeaandEastAfricanRiftValleysThinningcrust,basaltfloods,longlakesShallowEarthquakesLinearsea,upliftedandfaultedmarginsOceanicCrustFig.2-15Pg.40Fig.2-16Pg.41Convergent

PlateBoundariesWhereplatesmovetowardeachother,oceaniccrustandtheunderlyinglithosphereissubductedbeneaththeotherplate(witheitheroceaniccrustorcontinentalcrust)Wetcrustispartiallymeltedtoformsilicic(Silica-rich,iron-poor,i.e.,granitic)magmaStress:CompressionEarthquakesVolcanismRocksFeatures

LithosphereSimplifiedBlockDiagramAsthenosphereSubducted

PlateOceanicTrenchPlateMovementMagmaGenerationVolcanicArcShallowandDeepEarthquakesLithosphereFig.2-17Pg.42ConvergentPlateBoundary

e.g.,PacificNorthwestVolcanicActivityExplosive,CompositeVolcanoes(e.g.,Mt.St.Helens)Arc-shapedmountainrangesStrongEarthquakesShallowneartrenchShallowandDeepoversubductionzoneRocksFormedGranite(orSilicic)Iron-poor,Silica-richLessdense,lightcoloredUsuallyintrusive:Cooledslowly,deepdown,toformlargecrystalsandcoursegrainedrockFig.2-18Pg.42CompositeVolcanicArcs(Granitic,Explosive)BasalticVolcanism(Non-Explosive)The“RingofFire”(e.g.,currentvolcanicactivity)

AringofconvergentplateboundariesonthePacificRimNewZealand

Tonga/SamoaPhilippinesJapaneseIsls.AleutianIslandarcandTrenchCascadeRangeSierraMadreAndesMtns.Also:HimalayanstotheAlpsIndonesiaFujiyamaEastPacificRisePinatuboAndesMountainsCascadeRangeAleutianIslandArcSiarraMadreJapaneseIsls.NewZealandPhillipines.DepthofEarthquakes

atconvergentplateboundariesSeismicityofthePacificRim1975-199503370300150500800Shallowquakesattheoceanictrench(<33km)Deepquakesoverthesubductionzone(>70km)Depth(km)EachmajorplatecariesacontinentexceptthePacificPlate.Eachoceanhasamid-oceanridgeincludingtheArcticOcean.DivergentboundsbeneathE.Africa,gulfofCaliforniaThePacificOceanissurroundedbyconvergentboundaries.AlsoHimalayanstotheAplsMajorPlatesandBoundariesIcelandKilimanjaroRedSeaGulfofAdenEtna

Visuvius

EastAfricanRiftMid-AtlanticRidgeMid-IndianRidgeDivergentPlateBoundaries

RiftingandFormationofnewBasilticOceanicCrustOceanicCrust*Thin(<10km)Young(<200my)IronRich(>5%)/SilicaPoor(~50%)Dense(~3g/cm3)Lowlying(5-11kmdeep)FormedatDivergentPlateBoundariesCompositeVolcanicArcs(explosive)BasalticVolcanism(non-explosive)*Makea“ComparisonTable”onaseparatepageConvergentPlateBoundaries

FormationofGraniticContinentalCrustContinentalCrustThick(10-50km)Old(>200m.y.andupto3.5b.y.)IronPoor(<1%)/SilicaRich(>70%)LessDense(~2.5g/cm3)HighRising(mostlyaboveseelevel)FormedatConvergentPlateBoundariesOceanicCrustThin(<10km)Young(<200my)IronRich(~5%)/SilicaPoor(~50%)Dense(s.g.~3xH2O)Lowlying(5-11kmdeep)FormedatDivergentPlateBoundariesIsostaticAdjustmentWhydowesee,attheearthssurface,IntrusiveigneousrocksandMetamorphicrocksFormedmanykmdeep?Thick,lightcontinentalcrustbuoysupevenwhileiterodesEventually,deeprocksareexposedattheearth’ssurfaceMineralsnotinequilibriumweathered(transformed)toclaySedimentsareformedTransform

PlateBoundariesOffsetMid-oceanridgesMaycutcontinentse.g.SanAndreasFaultFig.2-21Pg.44TheHydrologicCycle

Workswith

Plate-TectonicstoShapethelandWeatheringclay,silt,sand…ErosionTransportSedimentationGeologicMaterialsSedimentsSedimentaryRocksThe

3rocktypes

formatconvergentplateboundariesIgneousRocks:When