Metamorphic Rock Notes

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

Metamorphism Metamorphism 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 Metamorphism Two 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 QuartzHematite 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 Nonfoliated

Metamorphic Rock Flow Chart Metamorphic Rock Minerals Add heat and/or pressure