Which sequence correctly lists the major layers of the Earth from exterior to interior?

• A. Mantle, Crust, Outer Core, Inner Core
• B. Crust, Mantle, Outer Core, Inner Core
• C. Crust, Outer Core, Mantle, Inner Core
• D. Crust, Mantle, Inner Core, Outer Core

Answer: (B)

The main idea here is understanding Earth’s structure from the outside in. The outermost layer is the crust, which is a thin, rigid shell. Right beneath it lies the mantle, a much thicker region that makes up most of Earth’s volume. Below the mantle is the outer core, a liquid layer of iron–nickel. At the center sits the solid inner core. So the correct sequence from exterior to interior is crust, mantle, outer core, inner core.

If you tried to put the outer core before the mantle, or the inner core before the outer core, you’d be reversing the actual arrangement established by seismic data and our physical models of Earth. Skipping the mantle or misplacing its position also clashes with how earthquakes travel through the planet.