Metamorphism is the process by which existing rocks, known as parent rocks or protoliths, undergo changes in mineralogy, texture, and chemical composition due to alterations in temperature, pressure, and chemically active fluids over time. This process can result in the formation of metamorphic rocks, such as schist, gneiss, or marble, which exhibit distinct characteristics compared to their parent materials. Metamorphism occurs typically deep within the Earth's crust and can be caused by tectonic forces, volcanic activity, or contact with hot magma.