Final answer:
Plate-mantle convection is the process of heat escaping from the Earth's interior and drives the movement of tectonic plates. Ridge push and slab pull are two primary forces of plate motion.
Step-by-step explanation:
Plate-mantle convection is the process by which heat escapes from the Earth's interior through the upward flow of warmer material and the slow sinking of cooler material in the mantle. This convection drives the movement of tectonic plates, leading to phenomena such as continental drift and the formation of mountains. Two primary driving forces of plate motion are ridge push and slab pull.
Ridge push occurs at divergent plate boundaries where new crust is formed. As molten rock rises from the mantle to create new crust at mid-ocean ridges, it pushes existing plates away from the ridge. Slab pull, on the other hand, occurs at convergent plate boundaries where two plates collide. The denser oceanic plate sinks beneath the less dense continental plate, creating a force that pulls the rest of the plate along with it.