Earth's lithosphere. Illustration of the Earth's lithosphere, the rigid outermost shell. It consists of the crust and the upper elastic portion of the mantle. The lithosphere varies with location. Continental lithosphere is less dense than oceanic lithosphere, with the thickness of both varying. The thinnest areas are at mid-ocean ridges, and the thickest are where mountains form, as shown here. Layers and rock types within the lithosphere include olivine and peridotite.