Metamorphic Rocks

striped rocks in canyon walls
Metamorphic rock creates a zebra striped pattern in the canyon walls of Marble Canyon. Death Valley National Park, California and Nevada. NPS photo by Dan Kish.


Metamorphic rocks form when high temperatures and pressure act on a rock to alter its physical and chemical properties (metamorphism means 'to change form'). These conditions often stretch, twist and fold the rock as it cools. In metamorphic rocks some or all of the minerals in the original rock are replaced, atom by atom, to form new minerals. Types of metamorphic rocks include gneiss, quartzite, marble, schist, soapstone, and phyllite.

Parks with examples of metamorphic rocks include

Key Terms

  • Contact Metamorphism: A type of local, thermal metamorphism caused by the intrusion and extrusion of magmas; takes place in rocks at or near their contact with a body of igneous rock.

  • Parent Rock: Rock from which soil, sediment, or other rock is derived.

  • Regional Metamorphism: A type of metamorphism that affects an extensive region, as opposed to local metamorphism that is effective only in a relatively restricted area.

Foliated gneiss
Foliated metamorphic gneiss.

NPS photo by Tim Connors

Foliated Metamorphic Rocks

As pressure squeezes on a parent rock during recrystallization it causes the platy or elongated minerals within the rock to become aligned, or foliated. Foliated rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied in. Types of foliated metamoprhic rocks include slate, schist, and gneiss. Gneiss records the ancient beginnings of the Appalachian Mountain belt at:

Non-foliated metamorphic soapstone.

Photo courtesy of Tina Kuhn

Non-foliated Metamorphic Rocks

Not all parent rocks have platy or elongated minerals and when these rocks undergo metamorphism the individual mineral grains do not align. Types of non-foliated metamorphic rocks include marble, quartzite and hornfels. Soapstone was used by the American Indians for tools and implements, and is found in:

Extensive quartzite depositsis are well-known from:

Last updated: October 27, 2021


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