How can gravity's role in tectonic plate motion be described?

A. Earth's magnetic field reverses

B. ridge push and slab pull

C. circulating material in the mantle

D. Earth's internal heating

BTW: not for college level!

Answer: (B) Ridge push and slab pull

Explanation: In ridge push, the mantle wells upward because of the convection and elevates the edges of spreading oceanic plates. Because these plates are higher at the spreading center, they are forced downhill due to gravity and eventually flatten out to the ocean floor.