Metamorphic Rocks

Metamorphic Rocks

• Form when an existing rock, or parent rock, undergoes intense pressure or are exposed to high temperature, they become metamorphic rocks. Metamorphic means (“Change Form”) .

Parent Rock

• Look at the Picture on page 133…

– Which image shows the parent rock?

– How does image #2 look different from image #1?

• Look at the picture from page 135 of your textbook. This shows shells being compacted into limestone, which is further compacted into marble.

• On the three pictures (shells, limestone, and marble), which one represents:

1. Sediment?

2. Metamorphic Rock?

3. Sedimentary Rock?

Two Types of Metamorphosis

• Local Metamorphosis- takes place over a small, local area

• Regional Metamorphosis- takes place over a large, regional area

Local Metamorphism

• Can occur in two different ways:

1. Contact- Rock located near molten rock (magma) changes form due to the heat (rock is cooked)

2. Deformational- Rock located near the center of an earthquake (fault line) changes form due to the pressure

Contact Vs. Deformational

• Think about whether the picture shows contact or deformational local metamorphism.

Regional Metamorphism

• Occurs in mountains as two plates of land crash into each other.

Local Vs. Regional Metamorphism• For each of the following areas, make a

guess as about whether they would be considered areas of local or regional metamorphism.

• 1. A Newly Formed Mountain Range (100 square miles)

• 2. A small area located next to a volcano

• 3. All of the rock located under the United States

• 4. Rocks located at the center of a recent Earthquake

Foliation

Foliation occurs whenthe minerals in a rockare compressed duringMetamorphism and gofrom chunky crystals toparallel lines ofminerals.

Foliation Example

• Look at the picture of granite and gneiss below (page 137 of your textbook). Gneiss shows foliation.

• In which direction was the pressure applied?

More Foliation Examples

Metamorphic Rock Descriptions:

Based on:

• Parent Rock ex. sandstone

• Mineral Content ex. shells, limestone

• Texture ex. marble

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0607/es0607page01.cfm?chapter_no=visualization