The Earth's mantle is the layer in the structure of the Earth that lies directly under the Earth's crust and above the Earth's outer core. The term is also applied to the structure of other planets. Earth's mantle lies roughly between 30 and 2,900 km below the surface. The boundary between the crust and the mantle is the Mohorovicic discontinuity named for its discoverer, and is usually called the Moho. The Moho is a boundary at which there is a sudden change in the speed of seismic waves. At one time some thought that the Moho was the structure at which the earth's rigid crust moved relative to the mantle. Current research places this zone of movement within the mantle, from 70 km (43 mi) below the ocean crust to 150 km (93 mi) below the continental crust. The mantle just below the crust is composed of cold and therefore rigid mantle fused to the crust but at the same time separated from it by the Moho. This rigid layer of crust and the upper mantle forms the lithosphere. The mantle differs substantially from the crust in its mechanical characteristics and its chemical composition. It is chiefly the difference of chemistry on which the distinction between crust and mantle is based. Mantle rock consists of olivines, different pyroxenes and other mafic minerals. Typified by peridotite, dunite, and eclogite, mantle rocks also possess a higher portion of iron and magnesium and a smaller portion of silicon and aluminium than the crust. In the mantle, temperatures range between 100°C at the upper boundary to over 3,500°C at the boundary with the core. Although these temperatures far exceed the melting points of the mantle rocks at the surface, particularly in deeper ranges, they are almost exclusively solid. The enormous lithostatic pressure exerted on the mantle prevents them from melting. http://en.wikipedia.org/wiki/Earth's_mantle