(platy minerals and are classified by composition, grain size, and foliation type. Non foliated metamorphic rocks have no evident planar fabric or foliation. These rocks are crystallized under conditions where there was no differential stress, and are comprised of minerals. 1. What is metamorphism? 2. How do temperature and pressure influence the metamorphic grade change from protolithic rock? 3. What are the key distinctions between foliated and non-foliated metamorphic rocks

1. Metamorphism is the change of minerals or geologic texture in pre-existing rocks, without the protolith melting into liquid magma. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids.

2. Metamorphism occurs because some minerals are stable only under certain conditions of pressure and temperature. When pressure and temperature change, chemical reactions occur to cause the minerals in the rock to change to an assemblage that is stable at the new pressure and temperature conditions.

3. Foliated metamorphic rocks exhibit layers or stripes caused by the elongation and alignment of minerals in the rock as it undergoes metamorphism. In contrast, nonfoliated metamorphic rocks do not contain minerals that align during metamorphism and do not appear layered.