What is Lithosphere and Asthenosphere?

The rigid part of the earth’s crust that extends from a depth of about 65km (40 miles) below the surface is known as Lithosphere. It consists Sial, the Sima, and the upper Mantle.

Underneath it is ‘the softer, this layer known as the Asthenosphere. The Lithosphere-Asthenosphere boundary is usually referred to as LAB.