The lower mantle lies around the outer core and is the thickest layer of the Earth. It is 1398 miles thick, and is made of a stone called peridotite. It is 4532 degrees fahrenheit, which keeps the stone mostly solid but also slightly plastic.
The Upper Mantle
Also called the Asthenopheric mantle, the upper mantle is the second thinnest layer at 403 miles thick. It is 2372 degrees fahrenheit and, like the lower mantle, it is solid and plastic.
Because it is plastic, the mantle is constantly in motion. This motion causes the plates in the crust above to shift.
