Alecia M. Spooner

“Three dominant hypotheses explain what drives plate tectonic motion. Each one relies on the convention of the mantle — the movement of heated rock materials beneath earth’s crust — but each one focuses on a different piece of the cycle: Mantle convection hypothesis: This hypothesis proposes that heated materials inside the earth move up and down in a circular motion (like the wax in a lava lamp) and the continental plates resting on this mat-erial are moved in the direction of the circular motion. Ridge-push hypothesis: This hypothesis states that the creation of new rock materials along mid-ocean ridges continually pushes oceanic crustal plates upward and outward, so that the far edges are forced into collisions with other plates. Slab-pull hypothesis: This hypothesis is the opposite of the ridge-push model. It proposes that the heavy, dense outer edges of crustal plates sink into the mantle at plate boundaries and pull the rest of the plate along with them.”
― Alecia M. Spooner, Geology For Dummies