What is the driving force of plate tectonics?

The driving force traditionally identified for plate tectonics is mantle convection. Heat escaping from Earth's interior causes slow movement in the mantle, helping transfer energy to the rigid tectonic plates above.

Mantle convection occurs because hot, less-dense material tends to rise while cooler, denser material sinks. However, modern geophysics describes plate motion as the result of several interacting forces rather than one simple conveyor belt. The strongest contribution for many plates is slab pull: old, cold oceanic lithosphere becomes dense and sinks into the mantle at subduction zones, pulling the rest of the plate behind it. Ridge push, caused by the elevated position of newly formed crust at mid-ocean ridges, also contributes.

This is why “mantle convection” is a fair quiz answer but a simplified one. Convection supplies and redistributes internal heat, while sinking slabs and gravitational forces often provide much of the direct mechanical drive. Magnetic fields, solar radiation, and Earth's rotation do not power the global movement of tectonic plates. The process is extremely slow: plates commonly move only a few centimetres per year.