Metamorphic Rock Process II
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Metamorphic rocks are formed when rocks are changed under heat and intense pressure.
Of the rocks that form the continental land mass, most are metamorphic rocks. There are three different ways rocks can be changed by heat and pressure. The process of changing is called metamorphism.
The first kind of metamorphism happens when rocks simply get buried by new rocks formed on top of them. The weight on top of rocks forces them deeper into the earth. The deeper the rocks are pushed into the ground the more they become exposed to heat. The heat and pressure cause the rock to change into a new rock. This type of metamorphism is called regional metamorphism and is the most common form of metamorphism. However, if the heat melts the rock and then the rock cools down it is an igneous rock, not a metamorphic rock.
Devil's Tower in Wyoming was formed by an igneous intrusion.
|Another way metamorphic rocks form is called contact metamorphism. Sometimes magma pushes its way up through the crust along cracks in a rock formation. As the magma cools it forms igneous rock. This kind of geologic feature is called an igneous intrusion. Although the rock in the intrusion is igneous rock, the rock the magma contacts can be changed by the heat of the magma and the pressure of the surrounding rock.