Plate Tectonics | National Geographic Society

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The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, ... ResourceLibraryENCYCLOPEDICENTRYResourceLibraryENCYCLOPEDICENTRYPlateTectonicsPlateTectonicsThetheoryofplatetectonicsrevolutionizedtheearthsciencesbyexplaininghowthemovementofgeologicplatescausesmountainbuilding,volcanoes,andearthquakes.Grades9-12SubjectsEarthScience,Geography,Geology,Oceanography,PhysicalGeographyImageSanAndreasFaultTectonicplateboundaries,liketheSanAndreasFaultpicturedhere,canbethesitesofmountain-buildingevents,volcanoes,orvalleyorriftcreation.PhotographbyGeorgGersterEncyclopedicEntryVocabularyPlatetectonicsisascientifictheorythatexplainshowmajorlandformsarecreatedasaresultofEarth’ssubterraneanmovements.Thetheory,whichsolidifiedinthe1960s,transformedtheearthsciencesbyexplainingmanyphenomena,includingmountainbuildingevents,volcanoes,andearthquakes.Inplatetectonics,Earth’soutermostlayer,orlithosphere—madeupofthecrustanduppermantle—isbrokenintolargerockyplates.Theseplateslieontopofapartiallymoltenlayerofrockcalledtheasthenosphere.Duetotheconvectionoftheasthenosphereandlithosphere,theplatesmoverelativetoeachotheratdifferentrates,fromtwoto15centimeters(onetosixinches)peryear.ThisinteractionoftectonicplatesisresponsibleformanydifferentgeologicalformationssuchastheHimalayamountainrangeinAsia,theEastAfricanRift,andtheSanAndreasFaultinCalifornia,UnitedStates.Theideathatcontinentsmovedovertimehadbeenproposedbeforethe20th century.However,aGermanscientistnamedAlfredWegenerchangedthescientificdebate.Wegenerpublishedtwoarticlesaboutaconceptcalledcontinentaldriftin1912.Hesuggestedthat200millionyearsago,asupercontinenthecalledPangaeabegantobreakintopieces,itspartsmovingawayfromoneanother.Thecontinentsweseetodayarefragmentsofthatsupercontinent.Tosupporthistheory,WegenerpointedtomatchingrockformationsandsimilarfossilsinBrazilandWestAfrica.Inaddition,SouthAmericaandAfricalookedliketheycouldfittogetherlikepuzzlepieces.Despitebeingdismissedatfirst,thetheorygainedsteaminthe1950sand1960sasnewdatabegantosupporttheideaofcontinentaldrift.MapsoftheoceanfloorshowedamassiveunderseamountainrangethatalmostcircledtheentireEarth.AnAmericangeologistnamedHarryHessproposedthattheseridgesweretheresultofmoltenrockrisingfromtheasthenosphere.Asitcametothesurface,therockcooled,makingnewcrustandspreadingtheseafloorawayfromtheridgeinaconveyer-beltmotion.Millionsofyearslater,thecrustwoulddisappearintooceantrenchesatplacescalledsubductionzonesandcyclebackintoEarth.MagneticdatafromtheoceanfloorandtherelativelyyoungageofoceaniccrustsupportedHess’shypothesisofseafloorspreading.Therewasonenaggingquestionwiththeplatetectonicstheory:Mostvolcanoesarefoundabovesubductionzones,butsomeformfarawayfromtheseplateboundaries.Howcouldthisbeexplained?Thisquestionwasfinallyansweredin1963byaCanadiangeologist,JohnTuzoWilson.Heproposedthatvolcanicislandchains,liketheHawaiianIslands,arecreatedbyfixed“hotspots”inthemantle.Atthoseplaces,magmaforcesitswayupwardthroughthemovingplateoftheseafloor.Astheplatemovesoverthehotspot,onevolcanicislandafteranotherisformed.Wilson’sexplanationgavefurthersupporttoplatetectonics.Today,thetheoryisalmostuniversallyaccepted.CreditsMediaCreditsTheaudio,illustrations,photos,andvideosarecreditedbeneaththemediaasset,exceptforpromotionalimages,whichgenerallylinktoanotherpagethatcontainsthemediacredit.TheRightsHolderformediaisthepersonorgroupcredited.DirectorTysonBrown,NationalGeographicSocietyAuthorNationalGeographicSocietyProductionManagersGinaBorgia,NationalGeographicSocietyJeannaSullivan,NationalGeographicSocietyProgramSpecialistsSarahAppleton,NationalGeographicSociety,NationalGeographicSocietyMargotWillis,NationalGeographicSocietyProducerClintParksotherLastUpdatedAugust17,2022UserPermissionsForinformationonuserpermissions,pleasereadourTermsofService.Ifyouhavequestionsaboutlicensingcontentonthispage,pleasecontactngimagecollection@natgeo.comformoreinformationandtoobtainalicense.Ifyouhavequestionsabouthowtociteanythingonourwebsiteinyourprojectorclassroompresentation,pleasecontactyourteacher.Sheorhewillbestknowthepreferredformat.Whenyoureachouttohimorher,youwillneedthepagetitle,URL,andthedateyouaccessedtheresource.MediaIfamediaassetisdownloadable,adownloadbuttonappearsinthecornerofthemediaviewer.Ifnobuttonappears,youcannotdownloadorsavethemedia.TextTextonthispageisprintableandcanbeusedaccordingtoourTermsofService.InteractivesAnyinteractivesonthispagecanonlybeplayedwhileyouarevisitingourwebsite.Youcannotdownloadinteractives.RelatedResources

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