1. The Theory of Plate Tectonics
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2. Theory of Plate Tectonics
Lithosphere is broken up into tectonic plates.
Plates move around on top of the asthenosphere.

4. Theory of Plate Tectonics
Plates are made of oceanic and continental lithosphere.
In our model of Pangaea, South America and Africa fit together… Where did the lithosphere come from between South America and Africa?

6. What makes the plates move??
Theory of
Plate Tectonics
Used evidence from “Continental Drift” and Sea Floor Spreading.”
Tuzo Wilson
What makes the plates move??

7. Convection Currents Arthur Holmes (1930’s)
heat transfer inside the earth causes mantle material to move.

8. How do Convection Currents work?
Heat rises, cool sinks.
As mantle material heats up, it rises to the surface.
Near the surface, it “cools,” sinking back down, creating a circular movement.