metamorphic rocks - ms 181denlearn.weebly.com/.../1420755/metamorphic_rocks.pdf · what are...

METAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORPHIC ROCKSMETAMORPHIC ROCKS

What are Metamorphic Rocks?

• Rock formed from existing rocks by HEAT and PRESSURE

• HEAT does not mean the rock MELTS !!!!

• Usually formed from igneous or sedimentary rock

What happens to rocks undergoing Metamorphism?

• Pressure squeezes their grains closer together

• Heat may rearrange the atoms forming new minerals

Where are types of Metamorphism?1) Regional Metamorphism

when large areas of rock are transformed by heat and pressure deep within the Earth, usually by mountain building from movements of tectonic plates.

2. Contact Metamorphism

• When magma intrudes into overlying rocks

• This magma “bakes” the surrounding rock which it makes “contact” with

.

The Metamorphic series

How do we identify Metamorphic rocks?

TEXTURE1) FOLIATED

a) Mineral Alignment: alignment ofmineral crystals.

Igneous Metamorphic

b) Banding

rocks show alternating bands of

light and dark color

Gneiss

Metamorphic Scheme ESRT pg.7

2) NON-FOLIATED: when rocks show a crystal- like appearance

Quartzite Marble

Metamorphic Scheme ESRT pg.7