What is the earths crust purpose?

Earth's crust. The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust.

The earth's crust protects the flora and fauna that inhabit the surface from the molten interior.