Metamorphic Rocks

Coarse grained kinked gneiss - a metamorphic rock

Metamorphic rocks are rocks that have changed.
The word comes from the Greek “meta” and “morph” which means to change form.  Metamorphic rocks were originally igneous or sedimentary, but due to movement of the earth’s crust, were changed.

If you squeeze your hands together very hard, you will feel heat and pressure.
When the earth’s crust moves, it causes rocks to get squeezed so hard that the heat causes the rock to change.
Marble is an example of a sedimentary rock that has been changed into a metamorphic rock.

  • Metamorphic rocks are the least common of the 3 kinds of rocks.
    Metamorphic rocks are igneous or sedimentary rocks that have been transformed by great heat or pressure.
  • Foliated (leaf-like) metamorphic rocks have layers, or banding.
    • Slate is transformed shale. It splits into smooth slabs and roof tiles are made from it.
    • Schist is the most common metamorphic rock. Mica is the most common mineral.
    • Gneiss has a streaky look because of alternating layers of minerals.

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