Metamorphic rocks form when preexisting rocks are subjected to intense heat and pressure without melting. This process can occur due to a variety of factors such as tectonic activity, burial and subduction, or contact with hot magma.
During metamorphism, the minerals in the original rock undergo changes in texture, composition, and/or structure, leading to the formation of new rocks with different properties. The specific changes that occur depend on the temperature, pressure, and chemical environment of the metamorphic process.
There are three main types of metamorphism:
Contact metamorphism: This occurs when rocks are altered by contact with hot magma or lava. The heat from the magma causes the minerals in the original rock to recrystallize, leading to the formation of new minerals and textures.
Regional metamorphism: This occurs when rocks are subjected to intense pressure and heat over a large area, typically due to tectonic activity. The pressure causes the minerals in the original rock to become aligned in parallel planes, leading to the development of foliation or banding.
Dynamic metamorphism: This occurs when rocks are subjected to intense pressure and shear stress along fault zones. The pressure and shear cause the minerals in the original rock to deform and recrystallize, leading to the formation of new minerals and textures.
Examples of common metamorphic rocks include marble, which forms from limestone subjected to high heat and pressure, and slate, which forms from shale subjected to regional metamorphism.
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