METAMORPHIC

Rocks

Metamorphic Rock

Metamorphism means to “change form”.

Rock can change when it undergoes heat and pressure.

Rocks can change into new, different rocks after heat and pressure.

The original rock (before the change) is called the parent rock.

Metamorphic Rock: Heat and pressure from where?

Where does the heat and pressure come from?

Heat comes from magma and Earth’s interior.

Pressure comes when tectonic plates converge or squeeze together.

Also from the weight of layers of rock stacked on top of one another.

Metamorphic Rock: Contact Metamorphism

There are 2 major types of metamorphism

Contact Metamorphism

Regional Metamorphism.

• Contact Metamorphism (Heat)

• Magma comes in “Contact” with rock

• The rock does not melt, but its mineral composition does change.

Metamorphic Rock: Regional Metamorphism

Regional Metamorphism (Heat and Pressure)

Tectonic plates converge creating pressure.

Regional means over a large area (km’s)

Occurs often when mountains are forming.

• Rock changes texture and mineral composition during

Regional Metamorphism

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Metamorphic Rock: In what ways do they change?

1. Texture

Mineral grains are rearranged, more coarse, flat, and more dense.

The texture of the rock changes as the minerals line up in stripes.

• Rock before

Regional

Metamorphism

• Rock after

Regional

Metamorphism

Metamorphic Rock: In what ways do they change?

Metamorphic Rock: In what ways do they change?

2. Mineral Composition

Existing minerals recrystallize into new, slightly

different minerals.

• Example: When a rock undergoes metamorphism, minerals like clay turn into larger flaky ones like mica.

Metamorphic Rock: Two major types

There are 2 major types of metamorphic rock

Foliated Metamorphic Rock

Non-Foliated Metamorphic Rock

Metamorphic Rock: Two major types

FOLIATED METAMORPHIC ROCKS

Have visible parallel bands of mineral grains.

Shale turns into Slate

Slate turns into Phyllite

Phyllite turns into Schist

Schist and Granite turns into Gneiss

Low grade

Metamorphism

High grade

Metamorphism

Metamorphic Rock: Two major types

Shale turns into slate

Metamorphic Rock: Two major types

Slate turns into phyllite

Metamorphic Rock: Two major types

Phyllite turns into Schist

Metamorphic Rock: Two major types

Schist or Granite turns into Gneiss

Metamorphic Rock: Two major types

NON-FOLIATED METAMORPHIC ROCKS

DO NOT have visible parallel bands of mineral grains.

Minerals do not take on a parallel alignment.

Sandstone turns into Quartzite

Limestone turns into Marble

Parent Rock Texture Metamorphic Rock

Shale Foliated Slate

Phyllite Foliated Schist

Schist Foliated Gneiss

Granite Foliated Gneiss

Limestone Non-Foliated Marble

Sandstone Non-Foliated Quartzite