Rocks and Minerals Metamorphic rocks Metamorphic Rocks form

Rocks and Minerals Metamorphic rocks

Metamorphic Rocks: • • form as a result of heat, pressure and chemical activity are divided into two groups based on whether they formed from regional or contact metamorphism.

Regional Metamorphic Rocks • formed by forces acting over large areas • formed at extreme temperature and pressure • form at great depths within the earth’s crust • form during mountain building due to plate tectonics

Contact Metamorphic Rocks • Form at the interface of hot magma and existing rock • Forms only locally where the minerals are changed by the extreme heat without actually melting

Characteristics of metamorphic rocks • Distortion - a change in the structure of a rock without changing the composition of the rock • Banding or zoning - when minerals become concentrated into bands of different colored minerals (pennies in clay)

• Increased density - metamorphic rocks are often denser than the rocks they formed from because they are exposed to such high pressure.

• Marble - metamorphosed limestone, fizzes with acid • Slate - formed from shale, very smooth • Quartzite - formed from sandstone, harder than glass • Gneiss - usually forms from granite, often banded • Schist - exhibits schistosity, often contains mica or garnet.

Marble

Slate

Quartzite

Gneiss

Schist

Mica Schist

Garnet Schist

A Big Pile of Schist

Metaconglomerate