Tectonic plates have several sources of energy. Early meteoric bombardment of Earth created heat, which was absorbed by Earth.
Then, more heat has been, and is still, generated by radioactivity within Earth. And, we can’t forget gravity and the pressure it puts on Earth’s interior. These basic facts of heat and pressure cause the molten rock beneath Earth’s crust to boil and flow.
The crust on top of all this activity reacts with its own, more limited, movement.
Continents move pretty slowly, usually only an inch or two (2 to 4 centimeters) a year.
Earth’s tectonic plates are huge sections of crust that move very slowly. As they move, they carry the continents with them. The edges of the plates are called plate margins. Most earthquakes and volcanoes occur at plate margins.