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PLATE TECTONICS
Tectonic Plates
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TECTONIC PLATES REVIEW
• Tectonic Plates: a block of lithosphere that consists of the crust and the rigid,
outermost part of the mantle
• What type of crust…
• Continental Crust
• Oceanic Crust
• Both
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MAJOR TECTONIC PLATES REVIEW
1. Pacific plate
2. North American plate
3. Cocos plate
4. Nazca plate
5. South American plate
6. African plate
7. Eurasian plate
8. Indian plate
9. Australian plate
10. Antarctic plate
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TECTONIC PLATE CLOSE-UP
REVIEW
• Consist of upper part of mantle
• Oceanic Crust (thinnest)
• Continental crust (thickest)
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THE THEORY OF PLATE TECTONICS
• Plate tectonics: theory that the Earth’s lithosphere is divided into tectonic
plates that move around on top of the asthenosphere.
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TECTONIC PLATE BOUNDARIES
• Boundary: a place where tectonic plates touch
• Convergent
• Divergent
• Transform
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CONVERGENT BOUNDARIES
• Convergent boundary: the boundary formed by the collision of two
lithospheric plates
• Continental-Continental
• Continental-Oceanic
• Oceanic-Oceanic
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DIVERGENT BOUNDARIES
• Divergent boundary: the boundary between two tectonic plates that are
moving away from each other
• Forms mid ocean rigids
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TRANSFORM BOUNDARIES
• Transform boundary: the boundary between tectonic plates that are sliding
past each other horizontally
• Faults
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POSSIBLE CAUSES OF MOTION
• Remember that the asthenosphere flows very slowly…
• Changes in density within the asthenosphere
• Caused by the outward flow of thermal energy from deep within the Earth
• When rock is heated, it expands, becomes less dense, and tends to rise to the
surface.
• When rock gets near the surface, the rock cools, becomes more dense, and
tends to sink
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THREE POSSIBLE DRIVING FORCES
OF PLATE TECTONICS
• Ridge Push: at mid-ocean ridges, the oceanic lithosphere is higher than it is
where it sinks into the asthenosphere. Because of ridge push, the oceanic
lithosphere slides downhill under the force of gravity.
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THREE POSSIBLE DRIVING FORCES
OF PLATE TECTONICS
• Convection: hot rock from
deep within the Earth rises,
but cooler rock near the
surface sinks. Convection
causes the oceanic
lithosphere to move
sideways and away from
the mid ocean ridge.
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THREE POSSIBLE DRIVING FORCES
OF PLATE TECTONICS
• Slab Pull: because oceanic lithosphere is denser than the asthenosphere, the
edge of the tectonic plate that contains oceanic lithosphere sinks and pulls
the rest of the tectonic plate with it in a process call slab pull.