Metamorphic Rocks

Metamorphic rocks are one of the main groups of rock that are the result of transformation or alteration of a rock type that has been there before, protolith, by a process called metamorfisme, which means "changing forms". Protolith subjected to heat (greater than 150 ° Celsius) and extreme pressure will experience physical changes and / or chemistry major. Protolith can form sedimentary rocks, igneous, or metamorphic rocks, others are older. Some examples are gneis metamorphic rock, slate, marble, and skist.
Metamorphic rocks make most of Earth's crust and are classified on the basis of texture and chemical composition and mineral (metamorphic facies) They formed far below the surface of the earth by the great stress from the rocks above and high pressures and temperatures. They are also formed by the intrusion of molten rock, called magma, into solid rock and is formed mainly at the contact between magma and high-temperature rocks.
Research metamorphic rocks (now exposed at the earth's surface caused by erosion and uplift) provides us valuable information about temperatures and pressures that occur deep within the earth's surface.