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Metamorphism is the process by which rocks undergo physical, chemical, or mineralogical changes due to changes in temperature, pressure, or chemical environment. These changes occur in the Earth's crust, typically in the presence of water, and cause the rocks to change their texture, composition, or structure. The rocks that are subjected to the metamorphic process are known as the parent rocks, while the transformed rocks are called metamorphic rocks.

There are three main types of metamorphism: regional, contact, and dynamic (or cataclastic). 1. Regional metamorphism: This is the most common type of metamorphism and occurs over a large area, usually deep within the Earth's crust. It is caused by high pressure and temperature brought about by tectonic processes, such as continental collision or subduction. This process results in the formation of rocks like schist and gneiss. 2. Contact metamorphism: This occurs when rocks come into contact with a heat source, such as an intrusive igneous body (e.g., a magma chamber). As a result, the temperature in the surrounding rocks rises, prompting chemical and physical changes to occur in a relatively small area. An example of a rock produced by contact metamorphism is marble, which forms from the heating of limestone. 3. Dynamic (cataclastic) metamorphism: This type occurs when rocks are subjected to intense physical stress, such as in fault zones. These rocks are deformed and fractured mechanically, and minerals within the rocks recrystallize due to the pressure and friction. Mylonite is an example of a rock formed by dynamic metamorphism.

There are three primary factors that contribute to the process of metamorphism: 1. Temperature: Increased temperature can cause mineral reordering, recrystallization, and the growth of new crystals. It can also promote chemical reactions that result in the formation of new minerals. 2. Pressure: High pressure can cause the reorganization of minerals into more compact forms. It can also prompt the formation of new, denser minerals. The pressure experienced by rocks imparts directional stress, which can cause the minerals within to realign and form foliated rocks, such as schist and gneiss. 3. Fluids: Fluids, particularly water, serve as a catalyst for metamorphic reactions. They can promote the dissolution of existing minerals and the transport of ions, which enables the formation of new minerals.

Time is an essential factor in the metamorphic process, as the changes that occur within rocks can take millions of years to become significant. Short-lived metamorphic events may not produce noticeable changes in the rocks, while longer-lasting events can lead to extensive recrystallization and the development of entirely new rock types.