The Earth is divided into three main layers - the crust, mantle, and core. The crust is the solid outermost layer that varies in thickness from 5 to 25 miles thick and has a cool temperature. Underneath the crust is the mantle, the thickest layer at around 1800 miles thick with a hot and solid but plastic texture. The innermost layer is the core which is divided into the solid inner core and liquid outer core with very hot temperatures.