Earth Science Metamorphic rockS

Origins of Metamorphic Rock Start with a parent rock Can be sedimentary, igneous, or metamorphic Metamorphic rocks Rocks in which the structure, texture, or composition of the rock have changed (metamorphosis) changed by heat, pressure, or a combination of both

Contact metamorphism When magma moves through the crust, the magma heats the surrounding rock and changes it. Some minerals in the surrounding rock are changed into other minerals by this increase in temperature. The greatest change occurs where magma comes into direct contact with the surrounding rock.

Regional metamorphism occurs when pressure builds up in rock that is buried deep below other rock formations or when large pieces of the Earth’s crust collide with each other. The increased pressure and temperature causes rock to become deformed and chemically changed.

Composition of Metamorphic Rock As rocks undergo metamorphism the original minerals in a rock change physically or chemically into new minerals that are more stable within the new pressure and temperature conditions. calcite + + + Heat and Pressure = quartz hematite Garnet

Texture of Metamorphic Rock Two types: Foliated Metamorphic Rock Mineral grains are arranged in ribbons or bands Usually contains aligned grains of flat minerals, such as biotite mica or chlorite GNEISS GRANITE Heat / Pressure

Example of a foliated metamorphic rock

Although the bands are very small – slate, phylite, and schist are foliated. Shale (PARENT ROCK) Slate Phylite Schist

Nonfoliated Metamorphic Rock QUARTZITE SANDSTONE Heat / Pressure Nonfoliated Metamorphic Rock Mineral grains are not arranged in ribbons or bands commonly made of one or only a few minerals.

Exmaples of nonfoliated metamorphic rock undergoes metamorphism limestone Marble undergoes metamorphism Anthracite Coal Bituminous Coal

ROCK LAB Slate Foliated Parent Rock: Shale/mudstone smooth, dull, dark, layers Marble Nonfoliated Parent Rock: limestone fused calcite crystals, light color

Gneiss Quartzite Nonfoliated Foliated Parent Rock: Granite dark/light bands Quartzite Nonfoliated Parent Rock: Sandstone Fused quartz crystals

Schist Foliated Parent Rock: Phyllite flakey mica layers

THINK! Would it be better to build a statue made of gneiss or marble? WHY? (think of the parent rocks)