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2/13/17 GeologicTime- RelativeAgeDetermination GeologicTime- RelativeAgeDetermination A)PrincipleofUniformitarianism =Fornaturaldisasters, uniformitarianismusedtopredictfutureevents. Examples? Whichrocklayerisoldest(bottom,middleortop)? B)PrincipleofSuperposition =movingupwardthrough sequenceofsedimentaryrocks,agebecomesyounger GeologicTime- RelativeAgeDetermination C)PrincipleofCross-CuttingRelations =Ifigneousintrusion (orfaultorrivervalley)cutsacrossrocklayers,itisyounger thanrocklayers Clickerquestion Whendidthefaultontherightsideofthediagramoccur? A. AfterlayerGwaslaiddownbutbeforelayerJwaslaiddown B. AfterigneousrockMintruded,butbeforelayerKwaslaiddown. C. AfterlayerKwaslaiddown,butbeforelayerFwaslaiddown. GeologicTime- RelativeAgeDetermination D)PrincipleofFossilSuccession =Whenfossilsin sedimentaryrocksarearrangedbyrelativeage,groupsof fossilplants+animalshavechangedform(evolved)over geologictimeindefinite+recognizableorder. 1 2/13/17 GeologicTime- RelativeAgeDetermination GeologicTimeScale D)PrincipleofFossilSuccession =Groupsoffossilsinrock canrepresentintervalofgeologictime. Usingfossils+ radiometricagesof rocksfromallover worldresultedin GeologicTimeScale tableofagesrepresents Earth'sgeologichistory GeologicTimeScale- ImportantEvents AgeofEarth=4.6b.y.(fromageofmeteorites,moonrocks) Age-datedmeteorite Age-datedmoonrock 4,400 GeologicTimeScale- ImportantEvents PreCambrian =Largestblockoftime(88%ofEarthhistory); lifeevolvedat~3- 3.5b.y.a.(bacteria).Onlysoft-bodied organismslived,sofewfossilsarepreserved. GeologicTimeScale- ImportantEvents PreCambrian/Paleozoicboundary =Appearanceofabundant animalswithshells;fossilscommonfromthistimeandlater Extremevolcanism- EarlyPrecambrian 3.5b.y.oldstromatolites (cyanobacteria) IronFormation- MiddlePrecambrian AbundantnewlifeinEarlyPaleozoic 2 2/13/17 GeologicTimeScale- ImportantEvents Paleozoic("Oldlife")Era =Trilobites,crinoids,coralreefs, snails;Appearanceoffish,plants,amphibians,insects AbundantoceanlifeinPaleozoic GeologicTimeScale- ImportantEvents Paleozoic/Mesozoicboundary =Massextinction.Halfofall familiesoforganismssuddenlydisappeared. GeologicTimeScale- ImportantEvents Paleozoic("Oldlife")Era =CarboniferousPeriodinvolved extensiveforests,swamps(laterbecamecoal). CarboniferousForestandSwamp GeologicTimeScale- ImportantEvents Mesozoic ("Middlelife")Era =Dominanceofreptiles (dinosaurs),Firstbirds. DinosaursofMesozoicEra GeologicTimeScale- ImportantEvents Mesozoic/Cenozoicboundary =Massextinctionof1/4ofall familiesoforganisms.Extinctionofalldinosaurs. GeologicTimeScale- ImportantEvents Cenozoic("Recentlife")Era =Dominanceofmammals, Appearanceofhumans,currentlyexperiencingmass extinction. MammalsofCenozoic Mesozoic/CenozoicMassExtinction 3 2/13/17 WebExercise1– Duetwodaysago Exam#1 • • • • MondayFebruary27th 7:15PM 141LoomisHallforA- N 151LoomisHallforO– Z #8PlateTectonics • 2-pointpenaltyforevery24-hourperiodthatassignmentislate. NoWebExercise#1isacceptedafter1pmonFriday • After~5PMFriday,WebExercise#1scoreswillbevisibleinIL CompassGradebook;atthesametime,feedback,includingyour answersandthecorrectanswers,willbeavailableinILCompass Questions?ContacttheTA WebExercise#2- StartsFriday2/10;due2/17 • WebExercise#2(Earthquakes)willbeavailableontheGEOL118 ILCompassWebsiteonFriday • WebExercise#2willincludequestionsbasedoninformationin HazardCity software(MasteringGeology WebSite)andthe Internet. • YoumustbuyaccesstoMasteringGeologyandRegister(see classwebpagesforinstructions) https://www.youtube.com/watch?v=uLah VJNnoZ4 Startat2:00 PlateTectonics PlateTectonicstheory =outerportionofEarthconsistsof numberofthickslabsofrock(tectonicplates)thatslowly movearoundglobe;Inmapview,tectonicplatecanconsist entirelyofoceaniccrustorbothoceanic+continentalcrust. PlateTectonics Incross-section,tectonicplate=lithosphere - ~cool,outer rigidlayerwhererockscanbreak,~100kmthick,includes entirecrust+outerpartofmantle;belowlithosphereis asthenosphere - layerof~hot,weakrockthatflows,from ~100- ~300kmindepth,onlymantlerock. 4 2/13/17 PlateTectonics TheasthenosphereisNOT alayerofliquid PlateTectonicBoundaries Threetypesofplateboundaries:Divergent,Convergent, Transform PlateTectonicBoundaries I)Divergentboundary - whereplatesmoveapart.Defined byoceanicridge - underseavolcanicmountain rangeof non-explosivevolcanoes whereoceaniccrust (basalt)is produced duetorisingmoltenrock (whichgeneratesminor EQ'sonly);cooledrockmoveslaterallyawayfromridge PlateTectonicBoundaries Tectonicplateboundariesaredefinedbyzonesoffrequent earthquakes.Volcanoesandmountainrangesarealso commonatplateboundaries. PlateTectonicBoundaries I)Divergentboundary - whereplatesmoveapart. PlateTectonicBoundaries http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_se afloorspreading.html 5 2/13/17 PlateTectonicBoundaries- Divergent Divergentboundary/oceanicridgewrapsaroundglobe PlateTectonicBoundaries- Divergent Examples= Mid-Atlanticridge, Iceland Betterviewedin GoogleEarth Oceanicridgeshowninred PlateTectonicBoundaries II)Convergentboundary - whereplatescometogether; definedbysubduction zone,whereoldoceanlithosphereis subducted (descendsbackintomantle+melts)+destroyed PlateTectonicBoundaries- Convergent Manyearthquakes (EQs,majorandminor)asrocksgrind pasteachother PlateTectonicBoundaries- Convergent Oceanic trench (deeplineartrough)=wheresubduction begins.Ascrust+mantlemelt(partially),produces explosivevolcaniceruptions +volcanicmountains PlateTectonicBoundaries- Convergent Oceanic trench (deeplineartrough)=wheresubduction begins.Ascrust+mantlemelt(partially),produces explosivevolcaniceruptions +volcanicmountains SeeGoogleEarthtrenches 6 2/13/17 PlateTectonicBoundaries- Convergent Examples=Andesmountains(ocean/continent convergence),Japan(ocean/oceanconvergence) PlateTectonicBoundaries- Convergent Ifalloceanlithosphereissubducted,thereis continent/continentcollision;continentscan'tsubduct (~lowdensity),creatingtremendousmountainrange(and major+minorEQs)butnovolcanoes(e.g.,Himalayas). PlateTectonicBoundaries- Transform Wheretwoplatesgrindpasteachotherwithhorizontal motion;definedbymajorfault (transformfault);not creatingnewcrustordestroyingoldcrust(norockmelts), sonomountainsorvolcanoes;grindingtwoblocksofcrust pasteachother,solotsofEQ's(major+minor). PlateTectonicBoundaries- Convergent MarginofPacificOcean="RingofFire"(lotsofEQs+ volcanoes),thereisconvergentboundaryatmostlocations PlateTectonicBoundaries - Convergent Continent/ContinentCollisionZone Example=Himalayas PlateTectonicBoundaries- Transform Example=SanAndreasFault,CA. 7 2/13/17 Clickerquestion Whichtypeofplateboundaryusuallygenerates explosivevolcanoes? A. Divergentplateboundary B. Convergentplateboundary C. Transformplateboundary D. Alloftheabove E. Noneoftheabove PlateTectonicMotion- Speed Platesmoveatspeedsof2- 10cm/yr (measuredbyageof oceancrustandbyaccuratepositionsoflocationsonEarth fromlaser-satellitedata) PlateTectonicMotion- OverGeologicTime Platesmoveatspeedsof2- 10cm/yr;Overgeologictime, Earth'ssurfaceisconstantlychangingplace Clickerquestion Whichtypeofplateboundarydoesnotoftengenerate large,damagingearthquakes? A. Divergentplateboundary B. Convergentplateboundary C. Transformplateboundary Skippednext4slides PlateTectonicMotion- FutureProjections Continentpositions50m.y.infuture 8 2/13/17 PlateTectonicMotion- FutureProjections Californiawon’tfallintoPacificOcean PlateTectonic MotionFuture Projections California PlateTectonicTheory- Importance PlateTectonicTheory- Importance WhyisPlateTectonicstheoryrelevanttoNaturalDisasters? WhyisPlateTectonicstheoryrelevanttoNatural Disasters? 9