Final answer:
The lithosphere, which includes the crust and uppermost mantle, lies directly above the asthenosphere, a semi-molten region that allows the lithosphere to move.
Step-by-step explanation:
The lithosphere lies directly above the asthenosphere. The lithosphere includes the crust as well as the uppermost part of the mantle. It is characterized by its brittle and rigid nature, and it is approximately 100 kilometers thick. Below this rigid layer is the asthenosphere, which is part of the upper mantle that behaves plastically and can flow.
In contrast to the brittle lithosphere, the asthenosphere is partially molten and can act like a soft solid under great pressures and temperatures within the earth. This layer allows for the movement of the lithospheric plates above it. These divisions of Earth's interior are determined by the mechanical properties of the layers — the lithosphere is rigid and brittle, while the asthenosphere is more ductile and capable of flow.