What is the Crust?

• A. The outermost layer of the Earth, hard and cool
• B. The middle layer of the Earth, hot and pliable
• C. The central metallic sphere
• D. The gaseous envelope around Earth

Answer: (A)

The crust is the outermost layer of the Earth, a solid, rigid shell that is cooler than what lies beneath. It sits on the mantle and forms the surface we live on, with two main types: continental crust (thicker and less dense) and oceanic crust (thinner and more dense). The crust is relatively thin compared with the deeper layers, and its cool, solid nature contrasts with the hot, capable-of-flow mantle beneath and the hot, metallic core at the center. The atmosphere surrounds the planet but is not part of the crust. So describing the crust as the outermost layer of the Earth, hard and cool, is the accurate picture.