Earth’s Surface Morphology and Convection in the Mantle

Abstract

It is now generally agreed that the Earth’s solid mantle is undergoing thermal convection. Much of the evidence for this conclusion is derived from geological and geophysical observations of the Earth’s surface, its relative horizontal motions and its topography. Direct consequences of the mantle flow include plate tectonics, which refers to the relative motions of the continents, spreading of the sea-floor, creation of new crust and mid-ocean ridges at spreading centres, and subduction at ocean trenches, along with associated phenomena such as mountain building and volcanism. The motion of the mantle over geological time scales is driven by gravity acting on density differences, which result from loss of heat from the Earth’s surface and, to a lesser extent, from transfer of heat from the Earth’s core to the mantle. Mantle convection phenomena are reviewed here in the context of geomorphology because they are responsible for producing much of the large-scale topography (horizontally > 10 km) of the Earth’s surface. This topography, in turn, imposes strong influences on the atmosphere and ocean circulation patterns, affects precipitation, and provides the base on which erosion and sedimentation processes act. The surface transport processes can also couple back to mantle flow and topography through redistribution of loading on the mantle.