1. n. [Geology]

The intermediate layer of the Earth beneath the crust that is about 2,900 km [1,820 mi] thick and overlies the core of the Earth. The mantle consists of dense igneous rocks like pyroxenite and dunite, composed of the minerals pyroxene and olivine. The crust, mantle, and core of the Earth are distinguished from the lithosphere and asthenosphere on the basis of their composition and not their mechanical behavior. The Mohorovicic discontinuity abruptly separates the crust from the mantle, where the velocity of compressional waves is significantly higher.

See related terms: asthenosphere,  convection,  core,  crust,  igneous,  lithosphere,  midoceanic ridge,  Mohorovicic discontinuity,  plate tectonics,  subduction,  Wadati-Benioff zone