The brittle, relatively cool outer layer of Earth, consisting of the oceanic and continental crust and the outermost, rigid layer of mantle.

The brittle, relatively cool outer layer of Earth, consisting of the oceanic and continental crust and the outermost, rigid layer of mantle.

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

Answer: (C)

The outer, brittle shell of Earth that includes both oceanic and continental crust along with the rigid outer part of the mantle is the lithosphere. This layer behaves as a solid, rigid shell, which is why it forms the tectonic plates that move on the weaker, ductile layer beneath. The upper mantle beneath the lithosphere, called the asthenosphere, is hotter and can flow slowly, so it isn’t part of this rigid shell. If you only have the crust, you’d miss the rigid portion of the mantle that closes the shell, and if you named the asthenosphere or the mantle alone, you’d describe a region that isn’t rigid and brittle.

The outer, brittle shell of Earth that includes both oceanic and continental crust along with the rigid outer part of the mantle is the lithosphere. This layer behaves as a solid, rigid shell, which is why it forms the tectonic plates that move on the weaker, ductile layer beneath. The upper mantle beneath the lithosphere, called the asthenosphere, is hotter and can flow slowly, so it isn’t part of this rigid shell. If you only have the crust, you’d miss the rigid portion of the mantle that closes the shell, and if you named the asthenosphere or the mantle alone, you’d describe a region that isn’t rigid and brittle.