In order to complete a convection current, the rising material must eventually earth.

sink back into Earth

When temperature differences exist, hot liquids rise and cold liquids sink. This creates convection currents. Convection currents transfer heat through the fluidity of water, air, or even hot magma. Convection currents develop when heated fluids expand. These fluids become less dense. The decrease in density causes the fluid to rise away from the original heat source. As the fluid rises, colder fluid is pulled toward the heat source and replaces the warm fluid. This fluid is then heated. It rises, and the process begins again. Convection currents establish a circular current that only ceases once the heat is evenly transferred throughout the fluid.