The Core–Mantle Boundary Region

Published by the American Geophysical Union as part of the Geodynamics Series, Volume 28.

The core-mantle boundary (CMB) is the largest density interface within the Earth's interior, and the change in material properties is as significant as that between the solid Earth and the hydrosphere. The two giant heat engines responsible for plate tectonics and the geodynamo dynamically interact at this boundary. The CMB is as dynamic as the Earth's outer skin, and seismological observations show that dense mantle dregs, anti-continents, raft around the mantle's base and are underlain by giant molten oceans. The mantle dregs are sheared and have developed strong seismic anisotropy. The CMB dynamically interacts with the planet's surface; old oceanic lithosphere has been imaged down to the mantle's base where it accumulates. Reversal pathways of the geomagnetic field may be controlled by molten oceans at the CMB. The molten oceans the seismological ultra low velocity zone--may be the source of hot-spot volcanism at the Earth's surface. The complex magnetohydrodynamics of the geodynamo within the fluid outer core of the Earth has been simulated on a computer, and the models show a surprising similarity to the observed geomagnetic field, including the observed westward drift and episodes of flux expulsion.