11| plate tectonics abridgedavconline.avc.edu/mpesses/pdfs/geog101/geog101lec11a.pdf · 11| plate...
TRANSCRIPT
GEOG 101 10/10/2013
Instructor: Pesses 1
11| Plate Tectonics Abridged
Part III– Earth’s Changing Landscapes
Geography 101Physical Geography: Earth’s Surface Landscapes
M. Pesses, Antelope Valley College
Japan
Pictures provided by Prof. Lori Dengler, Humboldt State University. Pictures provided by Prof. Lori Dengler, Humboldt State University.
GEOG 101 10/10/2013
Instructor: Pesses 2
Ring of Fire Plate Tectonics
TheEarth’ssurfaceiscoveredbyaseriesofcrustalplates
Theseafloorisconstantlymovingandbeingregenerated
Themovementresultsfromconvection Theconvectionresultsfromradioactivedecay
Alfred Wegener (1912)
OriginoftheContinentsandOceans,1915 ProposedContinentalDrift Manyrejectedit
Pangaea
AsupercontinentintheTriassicPeriod Keepinmindthiswasonlyabout300‐250millionyearsago Newresearchisexploringothersupercontinentsthatexistedbeforethis
GEOG 101 10/10/2013
Instructor: Pesses 3
Continental Drift
Wegenerhadsomestuffwrong,buthadasoundtheoreticalconcept Wrongabouttimelineandwhatmovedthecontinents Thoughtcentrifugalforcemovedcontinents
Evidence
Continentalfit Strata Mountains Glacialevidence Fossils PastClimates
Fit
Itlooksright… Belowcurrentsealevel
Strata Evidence
Mountain Evidence Glacial EvidenceMassiveglacierscoveredsouthernhemisphere
latePaleozoicEraGlacialstriationsonAustralia,S.America,&India
lookslikeglaciersmovedinfromtheseaReconstructGondwana
Theglacialmovementsmakesense
GEOG 101 10/10/2013
Instructor: Pesses 4
Fossil Evidence Past Climates Evidence
Mid‐latitudecoal AreasoncebeingclosertotheEquator,lushvegetation
Breakup of Pangaea
Dismissal
AmericanAssociationofPetroleumGeologistsSymposium,1928 Morepeopledisputedtheideaeventhoughtheevidencewassolid Oneproblemwasthelackofproofforadrivingforce behindthecontinentsmoving.
It’shardtograsptheconcept MajorityofevidenceintheSouthernHemisphere
Resurgence
Researchonseafloorspreading gavemoreproofofcontinentaldrift(1950s‐1960s)
GEOG 101 10/10/2013
Instructor: Pesses 5
Resurgence
HarryHammondHess,WWII Echo‐sounding PublishedHistoryin1962
Resurgence
Stillnotenoughdataforeveryonetobuyit
Magneticreversals
Magnetic Reversals
Whenbasaltisformedinthisprocessitorientswiththemagneticfield Recordsthechangesinmagneticfield
Canhelprelativelydatetheseafloor
Magnetic Polarity
SeafloorrevealsaconstantrecordofthemagneticpolarityoftheEarthforthelast200millionyears
Magnetic Polarity
GEOG 101 10/10/2013
Instructor: Pesses 6
Magnetic Polarity
Continentalrecordsofpastmagneticpolaritydidn’tmatchthesea‐floor EithermeanstheEarthhashadtwosetsofpoles…
Orthecontinentsusedtobeindifferentplaces
Deep-Sea Drilling Project
Internationaleffort 1968‐1983
Gaveprooftosea‐floorspreading&continentaldrift
Sea-Floor Spreading
Thedrivingforcebehindcontinentaldrift Causeofunderseamountainrange
Mid‐oceanridgecausedbymagmaupwelling Cools&createsnewsea‐floor Oldersea‐floorsubducted,returnedtomagma
Thiscycleisknownasathermalconvectioncell
Relative Age of the Oceanic Crust
GEOG 101 10/10/2013
Instructor: Pesses 7
Sea-Floor Spreading, Subduction
The Theory of Plate Tectonics
Incorporates: Upwellingofmagma Seafloorspreading Continentaldrift Earthquakes Volcanoes Orogenesis
Howmountainsgetformed
Plate Boundaries
Spreading(Divergent)boundaries Convergingboundaries Transformboundaries
Spreading Boundaries
Characteristicofsea‐floorspreading Upwellingofmagma Constructionoflithicmaterial Mostareunderwater
GreatRiftValleyofEastAfricaexampleofacontinentalspreadingboundary
Zonesofextension
OceanicSpreadingBoundaryExample:Mid‐AtlanticRidge
GEOG 101 10/10/2013
Instructor: Pesses 8
Motion at Plate Boundaries
Rift Valley
Forming a Divergent Boundary
Middle East & Oil
©StevenDutch
Converging Boundaries
Collisionzones Whereplates(bothcontinentalandoceaniccrust)collide
Compression Crustalloss– destructionoflithicmaterial
GEOG 101 10/10/2013
Instructor: Pesses 9
Motion at Plate Boundaries
Transform Boundaries
Whereplatesslidepasteachother Nodiverging,noconverging Usuallynovolcanicactivity
GEOG 101 10/10/2013
Instructor: Pesses 10
San Andreas Fault Earthquakes & Volcanoes
Hot Spots
Magmaupwellingfromstationarysitesinthemantle
Notnecessarilyatplateboundaries
Canbeusefulintrackingmovementofplates
Volcano
Tracks