Final answer:
The lithosphere is a solid layer of the Earth's interior that includes the crust and upper mantle. It behaves as a brittle, rigid solid and is responsible for earthquakes.
Step-by-step explanation:
The lithosphere is a solid layer of the Earth's interior. It is composed of both the crust and the upper part of the mantle, which behave as a brittle, rigid solid. The lithosphere is about 100 kilometers thick and is responsible for the formation of earthquakes when it breaks under stress.