1. n. [Geology]

The density- and heat-driven cycling, transfer or circulation of energy through which material initially warms up and becomes relatively less dense, then rises, cools and becomes relatively more dense, and finally sinks. As a consequence of convection, material can turn over repeatedly in a convection cell. Within the Earth, radiogenic heating results in convection appearing in the mantle and might drive plate tectonic motions. Convection also occurs in the ocean waters and in the Earth's atmosphere.

See: mantle,  plate tectonics