Which layer is the rigid outer shell of the Earth, consisting of the crust and the upper mantle?

Which layer is the rigid outer shell of the Earth, consisting of the crust and the upper mantle?

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

Answer: (D)

The rigid outer shell of the Earth is the lithosphere, which combines the crust with the rigid upper part of the mantle. This layer is cool and brittle, forming the tectonic plates that move slowly on top of the more plastic layer beneath. The deeper mantle and the core are not part of this rigid shell: the mantle below the lithosphere becomes more ductile and can flow, and the core lies at the planet’s center. So the description fits lithosphere exactly because it is the crust together with the upper mantle that behave as a single, rigid shell.

The rigid outer shell of the Earth is the lithosphere, which combines the crust with the rigid upper part of the mantle. This layer is cool and brittle, forming the tectonic plates that move slowly on top of the more plastic layer beneath. The deeper mantle and the core are not part of this rigid shell: the mantle below the lithosphere becomes more ductile and can flow, and the core lies at the planet’s center. So the description fits lithosphere exactly because it is the crust together with the upper mantle that behave as a single, rigid shell.