Although metamorphic rocks typically form deep in the planet's crust, they are often exposed on the surface of the Earth. This happens due to geologic uplift and the erosion of the rock and soil above them. At the surface, metamorphic rocks will be exposed to weathering processes and may break down into sediment.
Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors. Conditions like these are found deep within the Earth or where tectonic plates meet.
