history of earth chapter 9: history of earthw3.salemstate.edu/~bhubeny/gls100/ch9_tour.pdfin earth...
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Chapter9:HISTORYOFEARTH
TheEssentialEarth,2ndEdition
ThomasH.Jordan&JohnGrotzinger
©2012byW.H.FreemanandCompany
HistoryofEarth• Earthis4.56BillionYearsOld
• Earthhasexperiencedarichanddiversehistorythatwewillexploreinthischapter
FormationoftheSolarSystem
• NebularHypothesis• Matterwithinagivenorbit
accretestogethertoeventuallyformplanets
• Leadstoformationofplanetsthatrotatewithinorbitsaroundthesun
TheSolarSystem
• Innerrockyplanetsformedfromtheaccretionofdensematerials
• Outergaseousplanetsformedfromtheaccretionoflessdensematerials
• Note:Plutoisnolongeraplanetasof2006
EarlyEarth
• Earthwasveryhotatitsorigin
• Violentimpactsfromplanetesimalsandotherbodieswerecommon
• ElementswithinEarthdifferentiatedtoformlayeredinternalstructure
EarlyEarth:AGiantImpact!
EarlyEarth:Differentiation EarlyEarth:Atmosphere&Oceans
• LightelementsthatmakeupouratmosphereandoceanswereaggregatedtoEarthfromplanetesimals
• Volcanicdegassingfedthemoleculestoearlyatmosphereandoceans
EarlyHistoryofInnerPlanets
• Earthhadlargelydifferentiatedby4.4Billionyearsago
• Otherinnerplanetsexperiencedsimilardifferentiationduringthistime
• Significantdifferencesareevidentintherelativesizesoftheseplanets’cores
• Earth’smoonpreservesahistoryofearlysolarsystemeventssinceitscrusthasnotbeenconstantlyrecycledthroughplatetectonicprocesses
EarlyHistoryofInnerPlanets
• Moon’ssurfaceprovidesarecordofimpactbombardmenthistory
Earth:EvolutionoftheContinents
• ContinentalcrustcontainstheoldestcrustalmaterialonEarth
• Continentsaredividedintotectonicprovinces,whicharelarge‐scaleregionsformedbyaparticularsetoftectonicprocesses.
• NorthAmericaprovidesawell‐knownexampleoftectonicprovinces
NorthAmericanProvinces
CanadianShield• OldestpartoftheNorthAmericancrust
• Precambriangraniticandmetamorphicrocks
InteriorPlatform• Precambrianbasalrocks(sameasonShield)areoverlainbyPaleozoicsedimentaryrocks
• Basinanddomestructures• Basinsaccumulaterelativelythicksedimentarypackages
AppalachianFoldBeltDeformationfrommultiplePaleozoicorogenies
RecordsthehistoryoftheassemblyofPangaea
N.AmericanCordilleraDeformationfromMesozoicandCenozoictectonicactivity
RecordsthehistoryoftheFarallonPlatebeneathNorthAmericancontinent
GlobalTectonicProvinces• Othercontinentshavesimilartectonicprovinces• Continentsarebuiltbyorogenicactivityaroundstablecontinental
nucleicalledcratons• CratonsconsistofPrecambrianshieldandplatformrocks
ContinentalGrowth• Magmaticaddition:Insubductionzones,differentiationofsilica‐richrockproducesnewcontinentalcrustalmaterial– VerticalProcess
• Accretion:Fragmentofbuoyant,continentalcrustbecomesattachedtotheedgeofacratonthroughtectonicprocesses– HorizontalProcess
• Accretedterrainscanbeidentifiedalongcontinentalmargins
ContinentalModificationOrogeniesmodifycontinentsthrough•Metamorphism•Thickeningofcontinentalcrust•Uplift•Productionofstructuralfeaturessuchasthrustfaultsandfold•Meltingoflowercrust
India‐Eurasiacollisionprovidesamodernexampleoforogenicactivity
ContinentalModificationExample:
AssemblyofPangaea
MultipleorogeniesassociatedwiththeassemblyofPangaeamodifiedtheNorthAmericancontinent
TheWilsonCycle:EvolutionofContinents GeologicRecordofWilsonCycle&Supercontinents
BiologicalEventsinEarthHistory
• Theevolutionoflifeisrecordedintherockrecordbyfossils• Lifeinallthreedomainshasoriginatedfromacommon,
universalancestor• Earlyevidenceoflifecomesfrommicrofossilsandchemical
tracesoflife
BiologicalEventsinEarthHistory
MicrobesDominatedinthePrecambrianStromatolitesaresedimentaryfeaturesthatprovideevidenceofabundantmicrobialcommunitiesformuchofEarth’shistory
OxygenationofPrecambrianAtmosphere
• GeologicfeaturesprovideevidenceofthebuildupoffreeoxygeninthePrecambrianoceansandatmosphereasaresultofphotosyntheticactivity
• AsecondstepinoxygenationisobservedattheendofthePrecambrian(600Millionyearsago)
RedBedsBandedIronFormations Grypaniafossils
CambrianExplosion• IntheCambrianperiod,amajorradiationoflifeoccurred
• Allmajorgroupsofanimalsalivetodayoriginatedduringthisradiation
CambrianExplosion
Examplesoffossilsfrombefore(Namacalathus)andafter(HallucigeniaandTrilobites)theCambrianExplosion
HistoryofAnimalDiversityMarkedbyRadiations&Extinctions