Metamorphism << `meht` uh MAWR fihz uhm >> is the set of processes by which rocks are changed in composition or texture. During metamorphism, the size, shape, and arrangement of the minerals in rocks are modified. As a result, new minerals may form or existing minerals may change in size.
Metamorphism is caused by heat or pressure or both, and sometimes fluids. Metamorphism does not involve the melting of rock. In contact metamorphism, rocks change as a result of contact with a hot igneous body, such as a lava flow. The change caused by the heat and pressure imposed below Earth’s surface is called regional metamorphism. Regional metamorphism often occurs over a large area. Dynamic metamorphism includes changes that result when a rock is deformed, perhaps by movements within a large fault.
See also Metamorphic rock; Rock (Metamorphic rock) (table).
