Answer:
The slab-pull and ridge-push.
Step-by-step explanation:
Reading some scientist about this subject are concluded that the sinking of cold ocean lithosphere directly drives the motions of mantle convection trough slab-pull and ridge-push. a basic definition about slab pull is the forces that drive the motions of tectonic plate at the surface and ridge-push is known as the pressure exerted by the excess height of the mid-ocean ridge.