The Earth’s crust and upper part of the mantle is broken into large pieces of rock. These large pieces of rocks are called tectonic plates. Tectonic plates never stop moving, this process is called continental drift. Tectonic plates move because of convection currents. These convection currents happen in the mantle, underneath the tectonic plates. read more
The main driving force of plate tectonics is gravity. If a plate with oceanic lithosphere meets another plate, the dense oceanic lithosphere dives beneath the other plate and sinks into the mantle: this process is called subduction. read more