What types of metamorphism exist?
Regional Metamorphism: Many metamorphic rocks form by regional metamorphism, named for the large areas of the crust that are affected. Regional metamorphism usually results from mountain building processes, which are caused by the collision of tectonic plates. These collisions compress and thicken the crust and cause considerable rock deformation. High Pressure Metamorphism: Some metamorphic rock forms at high pressures but at temperatures that are relatively low. This type of metamorphism occurs at subduction zones. Here, high pressures result when one plate is submerged under the mantle. Temperatures remain relatively low because the crust that forms the upper part of the subducting plate is cool, having been close to the Earth’s surface. As the plate subducts, it actually cools the mantle. The subducting plate reaches high pressures faster than it heats to high temperatures, and this pressure is enough to cause metamorphism. High Temperature Metamorphism: Some metamorphic rock forms
