Download Plate Tectonics

PLATE TECTONICS
4.3 Theory of Plate Tectonics
Earth’s Plates
• Lithospheric plates are large brittle pieces
of Earth’s outer shell.
• The theory of plate
tectonics explains
the movement of
lithospheric plates.
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4.3 Theory of Plate Tectonics
Boundaries of Lithospheric Plates
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Plate interactions
• As plates move around, they interact with
each other.
• 3 types of plate boundaries
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Types of Plate Boundaries
• Divergent
– Plates move apart
– Ex: Mid-Ocean ridge, African Rift Valley
• Convergent
– Plates move together
– Can be ocean crashing into ocean, ocean
crashing into land, or land crashing into land
– Ex: subduction zones, Himalayan Mountains
• Transform
– Plates slide past each other
– Ex: San Andreas Fault CA (p.215)
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What controls
plate movement?
4.3 Theory of Plate Tectonics
Movement from convection
• Some scientists believe that convection
controls the movement of plates.
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4.3 Theory of Plate Tectonics
Movement from slab pull
• Slab pull: the force of gravity pulls the
oceanic plate into the mantle while
dragging the rest of the plate along with it.
– This is now considered the driving force of Plate
Tectonics (p. 188)
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