Mantle Convection A - Newly formed rock at the mid-ocean ridge is warmer and less dense than the older rock. The new rock slides down and away from the ridge, pushing the plate outward.

B - A small-scale conduction current in the mantle wedge, pushes the plate further away from the ridge and back into the mantle.

C - As magma rises, it pushes the plates apart.

D - At subduction zones, the old denser plate sinks below the less dense tectonic plate. This process relies on gravity.