What is the lithosphere primarily composed of?

The lithosphere is primarily composed of the Earth's crust and the solid upper mantle. This layer is characterized by its rigidity and is the outermost shell of the Earth. The crust consists of various types of rocks, including continental and oceanic crust, and is relatively thin compared to the deeper layers of the Earth. The upper mantle, which lies just beneath the crust, contributes to the lithosphere's composition, as it contains solid rock that behaves in a brittle manner under stress.

Understanding the lithosphere's composition is crucial, as it plays a significant role in tectonic processes, such as plate movements and continental drift. The interaction between the lithosphere and the underlying, more ductile asthenosphere influences various geological phenomena, including earthquakes and volcanic activity.