The layer of the earth where convection occurs is the mantle. The mantle is located between the crust and the outer core and is made up of solid rock. However, the rock in the mantle is not completely solid and can flow very slowly over long periods of time. This flow is caused by convection, which is the transfer of heat by the movement of a fluid. In the mantle, convection is caused by the heat from the Earth's core, which causes the rock in the mantle to rise and fall. This movement of rock creates currents of hot and cold material that flow through the mantle and cause the Earth's tectonic plates to move.