What is the correct order of the five physical layers of Earth from outermost to innermost?

• A. Lithosphere, Asthenosphere, Lower Mantle, Outer Core, Inner Core
• B. Lithosphere, Upper Mantle, Lower Mantle, Outer Core, Inner Core
• C. Crust, Upper Mantle, Core, Inner Core, Outer Core
• D. Crust, Mantle, Core, Inner Core, Outer Core

Answer: (B)

Understanding how Earth is built from the outside in helps you picture this stack: the rigid outer shell is the lithosphere, which includes the crust and the very top part of the mantle. Beneath that sits the upper mantle, then the lower mantle, which extends down to the outer core. The outer core is a liquid layer of iron and nickel, and inside it lies the inner core, a solid ball of metal. So the five physical layers from outermost to innermost are lithosphere, upper mantle, lower mantle, outer core, and inner core.

In this framework, the lithosphere is the stiff shell, the mantle thickens and heats with depth (divided into upper and lower mantle), and the core transitions from a liquid outer layer to a solid inner sphere. Other sequences mixing crust with mantle or reversing the core layers don’t match these physical boundaries and the way these layers are arranged by depth.