Earth has four layers: the crust, the mantle, the outer core, and the inner core. The crust is made of solid rocks and minerals. From mud and clay to diamonds and coal, Earth’s crust is composed of igneous, metamorphic, and sedimentary rocks. Dynamic geologic forces created Earth’s crust, and the crust continues to be shaped by the planet’s movement and energy. Today, tectonic activity is responsible for the formation (and destruction) of crustal materials.