Mantle (geology) Mantle (geology) The mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets (including Earth), a number of asteroids, and some planetary moons have mantles. The Earth's mantle is a layer of silicate rock between the crust and the outer core. Its mass of 4.01 × 10 kg is 67% the mass of the Earth. It has
Sima (geology) magnesia. Comparable is the name 'sial' which is the name for the upper layer of the Earth's continental crust. The sima has a higher density (2800 to 3300 kg/m) than the sial, which is due to increased amounts of iron and magnesium, and decreased amounts of aluminium. When the denser sima comes to the surface it forms mafic rocks, or rocks with mafic minerals. The most dense sima has less silica and forms ultramafic rocks. Sima (geology) In geology, sima is the name for the lower layer of the Earth's crust. This layer is made of rocks rich in magnesium