Convection currents flow in the asthenosphere, immediately below the rocky outer lithosphere. Convection currents are one of three types of heat transfer, which involve the movement of energy from a warmer object to a cooler object.
Convection is the transfer of heat by the movement of a heated fluid. Convection currents start in the Earth's core and mantle. Heat from the mantle rises slowly. When heated material from the mantle reaches the asthenosphere, it pushes cooler materials away as it rises. Cooler material then sinks back into the asthenosphere. This process continues as long as heat is added to the fluid.