The Heat Is On
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Metamorphic rocks are formed when sedimentary or igneous rocks change under pressure or heat.
NASA
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Here on Earth we have three basic types of rocks: igneous, sedimentary, and metamorphic rocks. Scientists classify these rocks
by the way they were made. Igneous rocks are formed when lava from a volcano cools and hardens. Igneous rocks are also formed
when magma cools below Earth’s surface. Sedimentary rocks are formed when the elements wear rocks down into tiny particles
of dust, sand, and soil. Wind and water help move these particles around and deposit them into layers. As time passes, these
layers are cemented together and harden into new rocks. Metamorphic rocks form when sedimentary or igneous rocks change after
being exposed to extreme heat or pressure without melting. As conditions on Earth change, rocks may change from one type to
another. Sedimentary rocks can change into metamorphic rocks, or, if they melt, into igneous rocks. Igneous rocks can change
into sedimentary or metamorphic rocks, and metamorphic rocks can change into sedimentary or igneous rocks. Scientists call
these changes “the rock cycle."
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Earth is a huge mass made up of three kinds of rocks, called metamorphic rocks, igneous rocks, and sedimentary rocks. Can
one kind of rock change into another? The answer is yes!
Metamorphic rocks form when heat and pressure produce changes in igneous rocks, sedimentary rocks, or other metamorphic rocks. For example, the metamorphic rock slate
was once a sedimentary rock called shale. Metamorphic rocks generally form deep under ground. This is because the deeper a
rock is buried underground, the more heat and pressure there is on it. Heat and pressure change the properties of existing rocks and turn them into metamorphic rocks.
