types of rock— igneous, metamorphic, and sedimentary—and the processes that form them. • Weathering and Erosion – Weathering is the natural break down of rocks into smaller and smaller pieces. Erosion is the movement of broken rock from higher to lower elevations (down mountains and along streams). • Melting – Solid rock changing into magma due to very high heat • Heat and Pressure – Under many layers of earth’s crust, rock is exposed to a lot of heat and pressure