Continental Drift Chapter 10. Wegener’s Hypothesis Once a single supercontinent Started breaking...
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Transcript of Continental Drift Chapter 10. Wegener’s Hypothesis Once a single supercontinent Started breaking...
![Page 1: Continental Drift Chapter 10. Wegener’s Hypothesis Once a single supercontinent Started breaking up about 200 mya Continents drifted to current.](https://reader035.fdocuments.in/reader035/viewer/2022081501/5697bf751a28abf838c80403/html5/thumbnails/1.jpg)
Continental DriftContinental Drift
Chapter 10Chapter 10
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Wegener’s HypothesisWegener’s Hypothesis
Once a single supercontinentOnce a single supercontinent Started breaking up about 200 myaStarted breaking up about 200 mya Continents drifted to current locationContinents drifted to current location Evidence, but no mechanismEvidence, but no mechanism
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PangaeaPangaea
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PangaeaPangaea
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Wegener’s EvidenceWegener’s Evidence
1.1. FossilsFossils– Similar ones found in areas thought to have been Similar ones found in areas thought to have been
connectedconnected
2.2. Rock formationsRock formations– Rock ages same on African & S. American coastRock ages same on African & S. American coast– Continuation of mountain ranges across continentsContinuation of mountain ranges across continents
3.3. Climatic evidenceClimatic evidence– Glaciers in Africa and S. AmericaGlaciers in Africa and S. America– Tropical fossils in colder climatesTropical fossils in colder climates
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Rock EvidenceRock Evidence
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Fossil EvidenceFossil Evidence
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Climate evidenceClimate evidence
Glacial evidence in south Africa, Australia, South America, and India. Occurred at same time.
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Pangaea BreakupPangaea Breakup
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Breakup of Pangaea (cont)Breakup of Pangaea (cont)
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Breakup of Pangaea (cont)Breakup of Pangaea (cont)
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Breakup of Pangaea (cont)Breakup of Pangaea (cont)
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Mid – Ocean RidgesMid – Ocean Ridges
Under sea mountain rangesUnder sea mountain ranges Sediment thicker farther away from ridgesSediment thicker farther away from ridges Sediment closer to ridges is youngerSediment closer to ridges is younger Ocean floor is young compared to EarthOcean floor is young compared to Earth
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Mid - ocean RidgesMid - ocean Ridges
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Mid – Ocean RidgesMid – Ocean Ridges
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Sea Floor SpreadingSea Floor Spreading
Suggested by Harry HessSuggested by Harry Hess Ocean ridge is a crack (Rift) in Earth’s crustOcean ridge is a crack (Rift) in Earth’s crust Magma fills the crackMagma fills the crack As ocean floor spreads, continents also As ocean floor spreads, continents also
movemove
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Sea Floor SpreadingSea Floor Spreading
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Sea Floor SpreadingSea Floor Spreading
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PaleomagnetismPaleomagnetism
Study of magnetic properties of rocksStudy of magnetic properties of rocks Iron rich minerals in magma align with Iron rich minerals in magma align with
Earth’s magnetic fieldEarth’s magnetic field As magma solidifies, magnetic orientation As magma solidifies, magnetic orientation
becomes permanentbecomes permanent Residual magnetism is paleomagnetismResidual magnetism is paleomagnetism
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Earth as a MagnetEarth as a Magnet
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Polar WanderingPolar Wandering
Makes more sense for the continents to move than for the North Pole to move
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Magnetic Properties from PangaeaMagnetic Properties from Pangaea
Paths coincide if continents started as Pangaea
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Magnetic ReversalsMagnetic Reversals
Earth’s magnetic field does not always point Earth’s magnetic field does not always point northnorth
Magnetic reversals – orientation is opposite Magnetic reversals – orientation is opposite of normalof normal
““Normal” rocks and “Reversal” rocks line up Normal” rocks and “Reversal” rocks line up by time periodby time period
Alternating normal and reversed polarity Alternating normal and reversed polarity over timeover time
Geomagnetic time scaleGeomagnetic time scale
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Magnetic ReversalsMagnetic Reversals
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Magnetic ReversalsMagnetic Reversals
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Plate TectonicsPlate Tectonics
Theory that explains how large pieces of Theory that explains how large pieces of lithosphere, called plates, move and change lithosphere, called plates, move and change shapeshape
Study of formation of features in Earth’s Study of formation of features in Earth’s crustcrust
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LithosphereLithosphere
Solid outer layer of EarthSolid outer layer of Earth Consists of the crust and rigid upper part of Consists of the crust and rigid upper part of
the mantlethe mantle Broken into blocks called platesBroken into blocks called plates Plates float on the asthenospherePlates float on the asthenosphere
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AsthenosphereAsthenosphere
Solid plastic layer of mantle below the Solid plastic layer of mantle below the lithospherelithosphere
Made of mantle rock that flows very slowlyMade of mantle rock that flows very slowly Allows tectonic plates to moveAllows tectonic plates to move
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Lithosphere & AsthenosphereLithosphere & Asthenosphere
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Crust typesCrust types
1.1.Oceanic crustOceanic crust– DenseDense– Rich in magnesium and ironRich in magnesium and iron
2.2.Continental crustContinental crust– Low densityLow density
– Rich in silica (SiORich in silica (SiO22))
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Continental & Oceanic CrustContinental & Oceanic Crust
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Tectonic platesTectonic plates
Can be either or both oceanic and Can be either or both oceanic and continental crustscontinental crusts
15 major plates15 major plates Earthquakes – sudden shifts along plate Earthquakes – sudden shifts along plate
boundariesboundaries Volcanoes – plate motions generate magma Volcanoes – plate motions generate magma
that eruptsthat erupts
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Tectonic PlatesTectonic Plates
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Types of Plate BoundariesTypes of Plate Boundaries
1.1. Divergent boundariesDivergent boundaries– Plates move away from each otherPlates move away from each other– Most on the ocean floorMost on the ocean floor– Form ocean ridges (rifts)Form ocean ridges (rifts)– Plates separate at rift valleyPlates separate at rift valley
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Divergent BoundaryDivergent Boundary
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Divergent Boundary (on land)Divergent Boundary (on land)
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Types of Plate BoundariesTypes of Plate Boundaries
2.2. Convergent boundariesConvergent boundaries– Plates move toward each otherPlates move toward each other– Plates eventually collidePlates eventually collide– 3 types of collisions3 types of collisions
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Convergent BoundaryConvergent Boundary
Continental – Oceanic Crust CollisionsContinental – Oceanic Crust Collisions– Subduction zone – oceanic sinks under Subduction zone – oceanic sinks under
continentalcontinental– Magma rises to surface and forms volcanic Magma rises to surface and forms volcanic
mountainsmountains
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Continental – Oceanic Continental – Oceanic CollisionCollision
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Convergent BoundaryConvergent Boundary
Oceanic – Oceanic Crust CollisionOceanic – Oceanic Crust Collision– Forms ocean trench (subduction)Forms ocean trench (subduction)– Magma forms island arc (Example: Japan)Magma forms island arc (Example: Japan)
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Convergent BoundaryConvergent Boundary
Continental – Continental CollisionContinental – Continental Collision– Forms mountainsForms mountains– Edges crumple and thickenEdges crumple and thicken– Creates upliftCreates uplift
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Continent CollisionsContinent Collisions
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The HimalayasThe Himalayas
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Types of BoundariesTypes of Boundaries
3.3. Transform boundariesTransform boundaries– Plates slide past each otherPlates slide past each other– Sudden motion produces EarthquakesSudden motion produces Earthquakes– No magma involvedNo magma involved
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Transform boundaryTransform boundary
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San Andreas San Andreas FaultFault
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Earthquakes – 1 YearEarthquakes – 1 Year
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North America – EarthquakesNorth America – Earthquakes10 Year Period10 Year Period
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Causes of Plate MotionCauses of Plate Motion
1.1. Mantle convectionMantle convection– Convection currents drag platesConvection currents drag plates
2.2. Ridge PushRidge Push– Newly formed rock slides downhill at mid Newly formed rock slides downhill at mid
ocean ridgeocean ridge
3.3. Slab pullSlab pull– Subducting plate pulls more crust with itSubducting plate pulls more crust with it
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Plate MotionPlate Motion
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RiftingRifting Breaking apart of Earth’s crustBreaking apart of Earth’s crust
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TerraneTerrane
Piece of Piece of lithosphere lithosphere with a unique with a unique geologic geologic history history incorporated incorporated into another into another piece of piece of lithospherelithosphere
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Western U.S. TerraneWestern U.S. Terrane
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Alaska AccretionsAlaska Accretions
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Continental GrowthContinental Growth
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Effects of Continental ChangeEffects of Continental Change
Climate changesClimate changes LifeLife
– As populations As populations separate, new species separate, new species developdevelop