Section 4-3 What are metamorphic rocks? How are metamorphic rocks formed? How can metamorphic rocks be classified?

Metamorphic rocks are rocks that have changed due to temperature and pressure increases or that undergo changes in composition.

Metamorphic rocks are formed from changes in igneous, sedimentary, or other metamorphic rocks. Rocks beneath the Earth’s surface are under a lot of pressure from the rocks above them. If rocks are under heat and pressure, but not enough to melt the rock, they can become metamorphic rocks.

Classification of Metamorphic Rocks Foliated – metamorphic rocks that are created when mineral grains flatten and line up in parallel bands; examples are slate and gneiss

Nonfoliated – metamorphic rocks that are created when mineral grains change, grow, and rearrange, but do not form bands; examples are quartzite and marble