Oceanography

The Mantle

Mantle is the intermediate layer between the earth’s core and crust. It accounts for 84 percent of the earth’s volume and 67 percent of its weight. The mantle is complex in structure. It is about 2,900 kilometers thick and is subdivided into 10 or more layers. The mantle is composed of minerals rich in silica, magnesium and iron. The amount of magnesium increases toward the surface, and the amount of iron increases toward the core. The upper mantle is hotter than the lower mantle, because it has an extensive distribution of radioactive minerals such as uranium, thorium and potassium.