Download PLATE TECHTONICS

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THEORY OF PLATE TECTONICS
 Study of the moving, irregularly shaped slabs that make up the Earth’s lithosphere (crust).
 Links together ideas of Pangaea (whole Earth), Continental Drift, and the ocean/sea
floor spreading
 Explains how Earth has evolved over 4.5 billion years
 Helps to explain the formation, movements, collision, and destruction of Earth’s
crust
ALFRED WEGENER
 Developed the theory of Pangaea and the Continental Drift
 Came up with three important pieces of evidence
RIFT VALLEY
 A deep crack that runs through the center of larger underwater mountains
EVIDENCE OF PANGAEA AND CONTINENTAL DRIFT
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Fossils
Coal deposits
Glacial evidence
Matching rocks and mountain ranges across Atlantic
HARRY HESS
 Discovered that convection currents in mantle is the driving force behind why
the continents have drifted
CONVECTION CURRENTS
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Due to changes in temperature and density
These changes move crustal plates over the molten mantle
Currents act like wheels under a conveyor belt
Plates move like the belts move toward the cashier at a store at check-out
MID-ATLANTIC OCEAN RIDGE
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The underwater mountains are known as the Mid-Atlantic Ridge
A lot of volcanic action occurs at the ridge
Volcanic action occurs when the ocean floor moves away on either side of it
Lava wells up and hardens
OCEAN/SEA FLOOR SPREADING
 The lava which wells up and hardens at the Mid-Atlantic Ridge creates this new
ocean floor which is being called the ocean/sea floor spreading
 This helps explain the Continental Drift
 As a piece of the ocean floor moves, a continent goes with it