The Theory of Plate Tectonics • Page 97 • Lithosphere is broken Theory of up into tectonic Plate Tectonics plates. • Plates move around on top of the asthenosphere. • Plates are made of Theory of oceanic and Plate Tectonics continental lithosphere. In our model of Pangaea, South America and Africa fit together… Where did the lithosphere come from between South America and Africa? • Used evidence from Theory of “Continental Drift” Plate Tectonics and Sea Floor Spreading.” • Tuzo Wilson What makes the plates move?? Convection Currents • Arthur Holmes (1930’s) • heat transfer inside the earth causes mantle material to move. 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.