History of Earth Chapter 9: HISTORY OF EARTHw3.salemstate.edu/~bhubeny/GLS100/Ch9_Tour.pdfin Earth...
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Chapter 9: HISTORY OF EARTH The Essential Earth,2 nd Edition Thomas H. Jordan & John Grotzinger © 2012 by W. H. Freeman and Company History of Earth • Earth is 4.56 Billion Years Old • Earth has experienced a rich and diverse history that we will explore in this chapter Formation of the Solar System • Nebular Hypothesis • Matter within a given orbit accretes together to eventually form planets • Leads to formation of planets that rotate within orbits around the sun The Solar System • Inner rocky planets formed from the accretion of dense materials • Outer gaseous planets formed from the accretion of less dense materials • Note: Pluto is no longer a planet as of 2006 Early Earth • Earth was very hot at its origin • Violent impacts from planetesimals and other bodies were common • Elements within Earth differentiated to form layered internal structure Early Earth: A Giant Impact!
Transcript of History of Earth Chapter 9: HISTORY OF EARTHw3.salemstate.edu/~bhubeny/GLS100/Ch9_Tour.pdfin Earth...
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
