Mantle Convection

Mantle convection is the theory that the slow, solid-state flow of hot rock within Earth's mantle, driven by heat escaping from the planet's interior, is the underlying driving mechanism for plate tectonics, carrying tectonic plates on the mantle's flowing surface. British geologist Arthur Holmes first proposed mantle convection as a plausible driving mechanism for continental drift in the 1930s, well before plate tectonics itself was established, suggesting that convection currents in a plastic, slowly deforming mantle could account for the horizontal movement of continents that Alfred Wegener had proposed on other grounds but could not explain mechanically. In the theory, hot material rises beneath mid-ocean ridges, spreads laterally as it approaches the surface and cools, and eventually sinks back into the deep mantle at subduction zones, forming large-scale convective circulation cells operating over tens to hundreds of millions of years. Mantle convection is now understood to be driven by a combination of forces, including ridge push from buoyant rock at spreading ridges and slab pull from the negative buoyancy of cold, dense subducting plates, with the relative contribution of each still an active subject of geophysical research.