How Are Metamorphic Rocks Formed and What Do they Look Like?

Metamorphic rocks are formed from the alteration of pre-existing rock types (igneous, sedimentary or already formed metamorphic rocks) through metamorphism. The pre-existing rock, also known as protolith, is subjected to both heat and pressure, which causes chemical or physical changes.  These types of rocks form a huge part of the Earth’s crust and make up 12 […]

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