What term describes the rigid outer shell of the Earth that includes the crust and uppermost mantle?

• A. Crust
• B. Lithosphere
• C. Mantle
• D. Core

Answer: (B)

The lithosphere is the rigid outer shell of the Earth that includes the crust and the uppermost part of the mantle. This layer behaves as a single, brittle unit that forms the tectonic plates. The crust by itself is only a part of this shell, and the mantle by itself does not include the crust, so neither alone describes the entire rigid outer shell. The core sits deep at the planet’s center, well below this outer layer. Because the lithosphere combines both the crust and the upper mantle into one rigid shell that participates in plate tectonics, it is the best term for describing the structure in question.