The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere. The layer below the rigid lithosphere is a zone of asphalt-like consistancy called the Asthenosphere. The asthenosphere is the part of the mantle that flows and moves the plates of the Earth. The Mantle. The mantle is the layer located directly under the sima. It is the largest layer of the Earth, 1800 miles thick.