What are the three main types of rocks?
The three main rock types are igneous, metamorphic, and sedimentary. The three processes that change one rock to another are crystallization, metamorphism, and erosion and sedimentation. Any rock can transform into any other rock by passing through one or more of these processes. For example, igneous rocks can be converted into metamorphic rock if the igneous rock is buried and subject to heat and pressure. Igneous rocks can be converted into sedimentary rocks if the igneous rocks are weathered, eroded, and the resulting sediments deposited and buried.