Metamorphism is the process by which rocks change in composition, texture, or structure due to extreme heat and pressure. There are six main types of metamorphism: regional metamorphism, contact metamorphism, burial metamorphism, seafloor metamorphism, subduction zone metamorphism, and shock metamorphism. Regional metamorphism occurs when rock layers are compressed, folded, and buried deep underground. Contact metamorphism happens when magma intrudes into the upper crust near rock layers. Burial metamorphism takes place when sediments are buried deeply enough that heat and pressure cause mineral recrystallization and growth.