Metamorphic Rock Notes

FormationMetamorphic rocks form by heat, pressure, or a combination of the two.

MetamorphismMetamorphism is a process that changes the shape of something. – Most metamorphism occurs between 50˚C and

1000 ˚C.• (50˚C=122˚F and 1000˚C=1832˚F).

Metamorphic rocks are those whose structure, texture, or composition has changed.

Types of MetamorphismTwo types of metamorphism are contact and regional.

Contact Metamorphism• Magma moves through the crust– Heats surrounding rock and changes it• Increased temperature causes minerals to

change into other minerals• Magma in direct contact with

surrounding rock = greatest change– Greater distance from magma = lower

temperature = less change• Occurs near igneous intrusions

Regional Metamorphism• Pressure builds up in rock buried deep

below other rock formations…– OR large pieces of Earth’s crust collide

with each other• Increased temperature and pressure

cause rock to become deformed and chemically changed

• Occurs deep within Earth’s crust over thousands of kilometers

Composition• Metamorphic rocks are composed of

minerals that change as temperature and pressure are applied.

Calcite

Quartz Hematite

Garnet

Index Minerals• Index minerals are minerals that only

form at certain temperatures and pressures.

• Some common index minerals are biotite mica, chlorite, garnet, kyanite, muscovite mica, sillimanite, and staurolite.

Classification• Metamorphic rocks are classified by

texture. – Texture: The size, shape, or position of

the grains or minerals in a rock

• The texture of metamorphic rocks is broken down into two groups: foliated and nonfoliated.

Foliated• Foliated: The texture

of metamorphic rock in which the mineral grains are arranged in planes or bands

Nonfoliated• Nonfoliated: The

texture of metamorphic rock in which the mineral grains are not arranged in planes or bands.– Commonly made of

only one or a few minerals

Foliated or Nonfoliated?

Foliated or Nonfoliated?

Foliated FoliatedNonfoliated

Metamorphic Rock Flow Chart

Metamorphic Rock

Minerals

Add heat and/or pressure