The cycle through which Earth's "rocks" change from one type into another over time due to various Earth processes; creates changes in mineral compositions and physical structures. This process is known as the rock cycle. The three main types of rocks are igneous, sedimentary, and metamorphic, and they can all transform into one another through various geological processes such as weathering, erosion, melting, cooling, and pressure and heat. The rock cycle plays a critical role in shaping the Earth's surface and geology over long periods of time.