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1. Metamorphic rock is a rock that has changed its form.
Heat and pressure are needed to form a metamorphic
rock.
1. MANTLE
PRESSURE
MINERALS
2. Any type of rock can form a metamorphic rock
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1. Geologists classify metamorphic rocks based on the
arrangement of the grains that make up the rock.
1. Foliated the minerals are aligned in layers or bands
Nonfoliated – minerals arrange randomly
6. Quartzite forms from metamorphism of sandstone. Particles
in sandstone re-crystallize to form quartzite
7. Marble: nonfoliated
Slate: foliated
Gneiss: foliated
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A. How are metamorphic
rocks formed?
-Recrystallization: pre-existing
rock alters its form to make a
metamorphic rock
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B. For Metamorphic Rocks:
MELTING DOES NOT OCCUR!
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Types of Metamorphism
1. Regional Metamorphism
2. Contact Metamorphism
3. Burial Metamorphism
Under conditions of high temperature and
pressure, many metamorphic rocks form by the
process of recrystallization.
C. Where do metamorphic rocks form?
•Form over large areas by
extreme heat and pressure deep
inside Earth
Examples:
where mountains
form and where
tectonic plates
collide
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Types of Metamorphism
1.
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Regional Metamorphism
 associated with convergent plate margins
 folding and faulting increase thickness of the
crust
• occurs over a range of temperatures
and pressures
• low grade to high grade
metamorphism
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Regional
_____________
Metamorphism
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Example of
Regional
Metamorphism
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C. Where do metamorphic rocks form?
•Caused by just heat
Example:
Boundary
between hot
magma and
existing rock
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Types of Metamorphism
2.
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Contact Metamorphism
 occurs in rocks around a magma body
 high temperature (heat from magma)
 low pressure (occurs at shallow depths in the
crust)
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2. Contact Metamorphism
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3. Burial Metamorphism
Metamorphism
occurs due to
the pressure
& weight of the
Overlying rock
layers- no heat
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Types of Metamorphism
3.
Burial Metamorphism
 most common type, occurs where crust is
greater than 5 km thick
Relatively low temperature and pressure
(low grade metamorphism)
Maximum stress vertical, foliation
parallel to ground surface
=
REVIEW
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Contact Metamorphism
►Caused by contact (magma
or lava) with extreme heat
Regional Metamorphism
►Caused
by extreme pressure
and heat.
►Causes the rock to be more
dense.
►Occurs over wide regions
D. Key Identifying Features of Metamorphic
Rocks
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SLATE
Phyllite
Schist
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Foliation resulting from directed
stress
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D. Key Identifying Features of Metamorphic
Rocks
Figure 8.2
Distorted Structure
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►Metamorphic
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rocks will often have foliation or
a distorted structure.
Distorted Structure
D. Key Identifying Features of Metamorphic Rocks
Dark Red
Color
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Shiny,
flaky
D. Key Identifying Features of Metamorphic Rocks
Known as the zebra rock.
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E. What happens to a rock as you increase the grade of
metamorphism?
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1. Increased density
Low Grade
2. non porous
3. foliation
4. distorted structure
5. banding
High Grade
Shale
+
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+
=
slate
Slate
+
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+
=
Phyllite
Phyllite
+
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+
=
Schist
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What is this?
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I asked “what is this?
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Schist +
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+
=
Gneiss
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Original rock
Add heat &
pressure
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Metamorphic
rock
Shale
Slate
Slate
Phyllite
Phyllite
Schist
Limestone
Marble
Quartz &
Sandstone
Granite
Bituminous
Coal
Quartzite
Gneiss
Anthracite Coal
SLATE
Phyllite
Schist
Gneiss
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1. FOLIATED & NON FOLIATED
2. BANDING IS HIGH GRADE FOLIATION
3. NA
4. SHALE
5. LIMESTONE OR DOLOSTONE
6. METACONGLOMERATE
7. HORNFELS
8. MINERAL ALIGNMENT & HOW IT WAS
FORMED
9. PHYLLITE
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10. MARBLE COMPOSED OF CALCITE
11. HIGH GRADE METAMORPHISM
12. PYROXENE
13. MICA
14. QUARTZ SANDSTONE
15. GNEISS
1. c
2. c
3. a
4. c
5. d
6. c
7. c
8. c
9. b
10. c
11. b
12. c
13. b
14. a
15. d
16. GNEISS
17. QUARTZITE
18. MARBLE
19. SHALE
Pages 26 & 27
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A. SEDIMENTARY- I CAN SEE THE CLASTS
B. METAMORPHIC- I CAN SEE DISTORTED
STRUCTURE & BANDING/FOLIATION
C. SEDIMENTARY- I CAN SEE FOSSILS
D. IGNEOUS- I CAN SEE A GLASSY TEXTURE
E. SEDIMENTARY- I CAN SEE LAYERS
F. IGNEOUS- I CAN SEE INTERGROWN
MINERAL CRYSTALS
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1. 1
2. 2
3. 1 OR 4
4. 1
5. 4