Mantle

Definition

The mantleis the part of the Earth or of other rocky planets which lies between the outermost solid crust and the metallic core. On the icy planets of our Solar system, the mantle is the part that lies between the layered atmosphere and the ice-silicate core. On Jupiter, the mantle is made of two layers: one liquid and one metallic hydrogen. On Earth, it is mainly composed of silicate minerals, whose nature changes depending on the pressure (or depth). In the upper mantle, between the base of the crust and the transition zone at about 660 km, the principal rock type is peridotite composed of olivine, orthopyroxene, clinopyroxene, and an aluminous phase (plagioclase, spinel, or garnet). In the lower mantle, these minerals convert to denser phases such as Mg- or Ca-perovskite and magnesiowüstite. The terrestrial mantle is solid except in shallow zones of partial melting beneath mid-ocean ridges or in hot spots, and perhaps at the core-mantle boundary. The mantle convects at...