Why do tectonic plates move?
Tectonic plates are composed of the crust and upper mantle rock which is lighter than the more dense mantle. Rising and falling convection currents in the mantle cause imperceptibly slow movements in the plates (on the rate of fingernail growth). The source of the heat driving the convection currents comes from residual heat from the Earth’s formative processes, pressure from gravity, and from radioactive decay of elements.
