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Metamorphic Rocks

Under intense pressures and temperatures deep within the earth, the minerals in a rock can be changed, without melting, into new minerals. Kind of like computer morphing without the computer! Combinations of these new minerals form metamorphic, or "changed" rocks. Many metamorphic rocks are banded because of the rearrangement of new minerals. In gneiss, for example, the banded texture is caused by the segregation of dark and light minerals. These dark and light layers can often be irregular, particularly when the rock has been folded under pressure. In metamorphic rocks, such as schist, minerals are often plate-like and parallel, creating a texture called foliated.

Metamorphic rocks form a small percentage of Alberta's outcrops and can be found only in certain areas around Alberta. The Canadian Shield is the best area to find high-grade metamorphic rocks, such as gneiss, which is particularly visible at Pelican Rapids and Mountain Rapids. High-grade metamorphic rocks are those that have been subjected to extremely high pressures and temperatures during their formation. Quartzite is another common metamorphic rock in Alberta and is one of the major rocks in the Main Ranges of the Rocky Mountains. Between Waterton and Crowsnest Pass, and in the mountains near Jasper, there are numerous outcrops of low-grade metamorphic rocks. Low-grade metamorphic rocks are those that have been subjected to relatively low pressures and temperatures during their formation.

Like igneous rocks, metamorphic rocks were also scattered about the province by glaciers during the last Ice Age, and are also commonly found in gravel pits, river gravel bars, and rock piles in farmer's fields.

To learn about other types of rocks found in Alberta click here.

Metamorphic Rocks

Metamorphic Rocks