material near the core heats up, warming up the bottom layer of the mantle. Density begins to decrease due to particles moving more rapidly. The mantle's material then rises starting a convection current.
Convection currents within Earth's mantle form as material near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise. The rising material begins the convection current.Feb 24, 2012
