The lithosphere is the outer solid shell of the Earth. As the cooling surface layer of the Earth’s convective system, the lithosphere thickens over time. It is fragmented into relatively strong pieces or plates, which move independently relative to one another. These lithospheric movements are described as plate tectonics. The lithosphere includes the crust and, below, the uppermost layer of the mantle; it floats on the weaker asthenosphere. There are two types of lithosphere:

• Oceanic lithosphere, which is associated with Oceanic crust
• Continental lithosphere, which is associated with Continental crust

Oceanic lithosphere is typically about 50-100 km thick (but beneath the mid-ocean ridges is no thicker than the crust), while continental lithosphere is about 150 km thick, consisting 50 km of crust and 100km or more of uppermost mantle. Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle and is denser than continental lithosphere, for which the mantle is associated with crust made of felsic rocks. The crust is distinguished from the upper mantle by the change in chemical composition that takes place at the Moho discontinuity.

The lithosphere is another sphere of the earth’s climate systems.

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