igneous, sedimentary, metamorphic
You learned about the three rock types: igneous, sedimentary, and metamorphic. You also learned that all of these rocks can change. In fact, any rock can change to become any other type of rock. These changes usually happen very slowly. Some changes happen below Earths surface. Some changes happen above ground. These changes are all part of the rock cycle. The rock cycle describes each of the main types of rocks, how they form, and how they change.