plate tectonics lecture
TRANSCRIPT
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Plate TectonicsPlate Tectonics
Ch 17Ch 17
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Mountain View Hypothesis for Ring of Fire
16%
12%
10%
8%6%6%
5%
5%
4%
4%
3%
3%
2%2%
1%1%1%1%1%1%1%1%1%1%0%0%0%0%0%0%0%0%
weather
plate tectonics
ocean depth
shape of the world
Conspiratory Animals (bunnies,sharks, whales, penguins, elephants)Activity of People
population
God
sumo wrestlers
obesity
Destroying the planet
mountains
moon, sun & solar system
Earth Flattulence
ocean temperature
Godzilla and other monsters
movies / rock stars
ice bergs
car accidents
rock slides
teenage romance
gold rush / mining
color of grass
magnetic forces
land is sinking
shuttle launch
animal massuese
color of water
trees
oceans are getting bigger
air plane crash
rivers
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FactsFacts
South America moving away from South America moving away from Africa at 2-3 cm/yearAfrica at 2-3 cm/year
Hawaii is moving NW 8-9 cm/yrHawaii is moving NW 8-9 cm/yr Mount Everest growing 5 cm/yearMount Everest growing 5 cm/year
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Early TheoriesEarly Theories
Late 1500 Abraham Ortelius (map Late 1500 Abraham Ortelius (map maker) noticed the fit of the maker) noticed the fit of the continents in the Atlantic Ocean.continents in the Atlantic Ocean.– Proposed N & S America broke off of Proposed N & S America broke off of
Europe and Africa by earthquakes and Europe and Africa by earthquakes and floodsfloods
Late 1800s Eduard Suess (geologist) Late 1800s Eduard Suess (geologist) proposed that the southern proposed that the southern continents were joined- continents were joined- “Gondwanaland”“Gondwanaland”
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Alfred WegenerAlfred Wegener
German Scientist proposed in 1912 German Scientist proposed in 1912 “Theory of Continental Drift”“Theory of Continental Drift”
Scientific community believed ocean Scientific community believed ocean basins and continents were a permanent basins and continents were a permanent feature of Earth. feature of Earth.
Two flaws with Wegener’s theory caused Two flaws with Wegener’s theory caused them reject his hypothesis.them reject his hypothesis.– Cause of movement?Cause of movement?– How continents were moving through a How continents were moving through a
stationary ocean floor?stationary ocean floor?
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Continental DriftContinental Drift
Proposed all continents were joined Proposed all continents were joined together in a single land masstogether in a single land mass– Pangaea (all – earth)Pangaea (all – earth)
Pangaea broke apart 200 million Pangaea broke apart 200 million years ago (Mesozoic)years ago (Mesozoic)
Began theory with puzzle like fit of Began theory with puzzle like fit of continentscontinents
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EvidenceEvidence
Rock formationsRock formations– When Pangaea breaks apart large When Pangaea breaks apart large
structures (mtn ranges) would be structures (mtn ranges) would be separatedseparated
– Using this Wegener hypothesized there Using this Wegener hypothesized there would be similar rocks on either side of would be similar rocks on either side of the Atlantic Oceanthe Atlantic OceanMatching rocks in Appalachian Mountains, Matching rocks in Appalachian Mountains,
Greenland and Europe (more than 200 Greenland and Europe (more than 200 million years old)million years old)
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EvidenceEvidence
FossilsFossils– Similar fossils of plants and animals that Similar fossils of plants and animals that
lived on land would have been found on lived on land would have been found on separated continentsseparated continents
– Wegener hypothesized that land animals Wegener hypothesized that land animals could not have swum great distances could not have swum great distances across the oceanacross the ocean
– The ages of the fossils confirmed the The ages of the fossils confirmed the break-up time periodbreak-up time period
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EvidenceEvidence
ClimateClimate– By studying sedimentary rocks he found By studying sedimentary rocks he found
evidence of climactic changesevidence of climactic changesCoal beds in Antarctica meant that it was Coal beds in Antarctica meant that it was
once warm and rainyonce warm and rainyGlacial evidence in India, Australia, Africa Glacial evidence in India, Australia, Africa
and South America indicate thick ice capsand South America indicate thick ice caps
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Seafloor SpreadingSeafloor Spreading
Confirmed Wegener’s theories in the Confirmed Wegener’s theories in the 1960’s1960’s
TechnologyTechnology– SONAR - sound waves used to map SONAR - sound waves used to map
ocean floorocean floor– Magnetometer – detects small changes Magnetometer – detects small changes
in magnetic fields of rocksin magnetic fields of rocks
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OceanOcean
Vast underwater Vast underwater mountain ranges mountain ranges called mid-ocean called mid-ocean ridgesridges
Deep-sea trenches Deep-sea trenches are narrow long are narrow long depressions with depressions with very steep sides very steep sides (miles deep)(miles deep)
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Ages of RocksAges of Rocks
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Ages of RocksAges of Rocks
Ocean crust is much younger than Ocean crust is much younger than continental crustcontinental crust
Near ocean ridges crust is newNear ocean ridges crust is new In deep sea trenches crust is oldIn deep sea trenches crust is old Figure 17-7 page 450 (your textbook)Figure 17-7 page 450 (your textbook) Ocean sediments are much thinner Ocean sediments are much thinner
than on continents and increase with than on continents and increase with distance from ridgesdistance from ridges
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MagnetismMagnetism
Paleomagnetism – Study of Earth’s Paleomagnetism – Study of Earth’s magnetic recordmagnetic record
Basalt – Iron rich rock forms ocean crustBasalt – Iron rich rock forms ocean crust– The iron in the rocks is always aligned with the The iron in the rocks is always aligned with the
magnetic poles of the earth (north & south just magnetic poles of the earth (north & south just like a magnet)like a magnet)
– When lava hardens into basalt, iron ions are When lava hardens into basalt, iron ions are permanently aligned, recording the magnetic permanently aligned, recording the magnetic history of the earthhistory of the earth
Magnetic ReversalsMagnetic Reversals
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MagnetismMagnetism
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Earth’s StructureEarth’s Structure
Crust- Rocky outer Crust- Rocky outer layer (5-35 Km) layer (5-35 Km)
Mantle- 82% of Mantle- 82% of Earth’s Volume, Earth’s Volume, made of silica and made of silica and molten rockmolten rock
Core- iron and Core- iron and nickelnickel
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Earth’s Layers (Function)Earth’s Layers (Function)
Lithosphere (Ball of Rock) Crust and Lithosphere (Ball of Rock) Crust and Upper MantleUpper Mantle
Moho DiscontinuityMoho Discontinuity Asthenosphere (weak ball) Mantle, Asthenosphere (weak ball) Mantle,
rocks near melting point, allows rocks near melting point, allows lithosphere to movelithosphere to move
Mesosphere (middle ball) Very hot Mesosphere (middle ball) Very hot rock, capable of flow, more rigid rock, capable of flow, more rigid because of pressurebecause of pressure
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Earth’s Layers (Function)Earth’s Layers (Function)
Outer Core- Liquid Layer, generates Outer Core- Liquid Layer, generates magnetic fieldmagnetic field
Inner Core- Solid because of high Inner Core- Solid because of high pressurepressure
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Plate BoundariesPlate Boundaries
Divergent- (2 Divergent- (2 movements) places movements) places where 2 plates where 2 plates move awaymove away– Oceanic/Oceanic- Oceanic/Oceanic-
Mid-Ocean RidgeMid-Ocean Ridge– Continental/Continental/
Continental- Rift Continental- Rift ValleyValley
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Plate BoundariesPlate Boundaries
Convergent (1 Movement)- Places Convergent (1 Movement)- Places where plates come togetherwhere plates come together
Classified by types of platesClassified by types of plates
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Oceanic-OceanicOceanic-Oceanic
Subduction- Oceanic plate goes under Subduction- Oceanic plate goes under another plate, Recycles the rock, May form another plate, Recycles the rock, May form Island ArcIsland Arc
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Oceanic-ContinentalOceanic-Continental
Oceanic plate goes under Continental Oceanic plate goes under Continental plate.plate.
Causes Costal Mountain Range and Arc of Causes Costal Mountain Range and Arc of VolcanoesVolcanoes
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Continental-ContinentalContinental-Continental
Causes TALL Mountains to formCauses TALL Mountains to form
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TransformTransform
Transform (across)- Transform (across)- deforms crust, long deforms crust, long faults.faults.
Usually Usually underwater, except underwater, except San AndresSan Andres
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Causes of MovementCauses of Movement
Mantle Convection- Movement of warm Mantle Convection- Movement of warm and cool rock in mantle, similar to and cool rock in mantle, similar to conveyor beltconveyor belt
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Causes of MovementCauses of Movement
Ridge Push- Weight of uplifting ridge Ridge Push- Weight of uplifting ridge pushes plate toward trenchespushes plate toward trenches
Slab Pull- Weight of Subducting plate pulls Slab Pull- Weight of Subducting plate pulls the plate into the mantlethe plate into the mantle