1. Crust - The solid crust is the external and weakest layer of our planet.
2. Mantle - It is comprised of silicate minerals that are similar to ones located in the crust, which is made up of more magnesium and iron and lighter silicon and aluminum.
3. Outer core - The outer core is formed mostly of iron and nickel, and these metals are obtained in liquid form.
4. Inner core - This hard layer is smaller than our Moon at 750 miles (1,200 km) deep and is formed chiefly of iron.
