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 when
the minerals
in a rock
are
compressed
during
Metamorphism
and go
from chunky
crystals to
parallel lines of
minerals.
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/visualization
s/es0607/es0607page01.cfm?chapter_no=visualization