chapter 3: rocks table of contents section 3: metamorphic rocksmetamorphic rocks
TRANSCRIPT
Chapter 3: Rocks
Table of ContentsTable of Contents
Section 3: Metamorphic Rocks
A. Formation of Metamorphic Rocks
1. Metamorphic rocks is rock that has been changed because of changes in temperature and pressure, or the presence of hot watery fluids
2. Changes that occur can be in the form of the rock, the composition of the rock, or both.
Metamorphic RocksMetamorphic Rocks
3. Metamorphic rocks can form from igneous, sedimentary, or even other metamorphic rocks.
B. Heat and Pressure
1. Rocks beneath Earth’s surface are under great pressure from rock layers above them.
2. Temperature also increases with depth in Earth.
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3. In some places, the heat and pressure are just right to cause rocks to melt and magma to form.
4. Different types of metamorphic rock may form from the magma.
B. Heat and Pressure
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5. In other areas where melting doesn’t occur, some mineral grains can change by dissolving and recrystallizing—especially in the presence of fluids.
6. Sometimes, under these conditions, minerals exchange atoms with surrounding minerals and new, bigger minerals form.
B. Heat and Pressure
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7. Depending upon the amount of pressure and temperature applied, one type of rock can change into several different metamorphic rocks.
8. For example, shale, a sedimentary rock, will change into slate, a metamorphic rock.
Shale Slate
Heat & pressure
B. Heat and Pressure
Metamorphic RocksMetamorphic Rocks
9. As increasing pressure and temperature are applied, the slate can change into phyllite, then schist, and eventually gneiss.
Slate
10. Schist also can form when basalt is metamorphosed, or changed, and gneiss can come from granite.
C. Hot Fluids
1. Hot fluids from magma flow through space in and between underground rocks.
2. The hot fluids are mostly water, but they also contain dissolved elements and compounds.
3. These fluids can react with the rock they flow through and change its composition.
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C. Hot Fluids4. Most fluids that
transform rocks during metamorphic processes are hot and mainly are comprised of water and carbon dioxide.
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5. In the presence of hot, water-rich fluids, solid rock can change in mineral composition without having to melt.
D. Classifying Metamorphic Rocks
1. Metamorphic rocks form from igneous, sedimentary, or other metamorphic rocks.
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2. Heat, pressure, and hot fluids cause these rocks to change.
3. Each resulting rock can be classified according to its composition and texture.
E. Foliated Rocks1. When mineral grains line
up in parallel layers, the metamorphic rock contains a foliated texture.
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2. Two examples of foliated rocks are slate and gneiss.
3. Slate forms from the sedimentary rock shale.
Slate
E. Foliated Rocks
4. The minerals in slate are pressed together so tightly that water can’t pass between them easily.
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5. Because it’s watertight, slate is ideal for paving around pools and patios.
6. The naturally flat nature of slate and the fact that it splits easily makes it useful for roofing and tiling many surfaces.
E. Foliated Rocks7. Gneiss (NISE), another foliated rock, forms
when granite and other rocks are changed.
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8. Foliation in gneiss shows up as alternating light and dark bands.
9. Movement of atomshas separated the dark minerals, such as biotite mica, from the light minerals, which are mainly quartz and feldspar.
F. Nonfoliated Rocks
1. In some metamorphic rocks, layering does not occur.
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2. The mineral grains grow and rearrange, but they don’t form layers. This process produces a nonfoliated texture.
F. Nonfoliated Rocks
3. Sandstone is a sedimentary rock that’s often composed mostly of quartz grains.
Metamorphic RocksMetamorphic Rocks
4. When sandstone is heated under a lot of pressure, the grains of quartz grow in size and become interlocking, like the pieces of a jigsaw puzzle.
5. The quartz grains in quartzite are not in layers, so quartzite is a nonfoliated rock.
F. Nonfoliated Rocks
6. Marble is another nonfoliated metamorphic rock.
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7. Marble forms from the sedimentary rock limestone, which is composed of the mineral calcite.
8. Usually, marble contains several other minerals besides calcite.
F. Nonfoliated Rocks
9. Hornblende and serpentine give marble a black or greenish tone, whereas hematite makes it red.
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10. Marble is a popular material for artists to sculpt because it is not as hard as other rocks.
Section CheckSection Check
33Question 1
What type of rocks can form from any type of rock?
A. igneous B. intrusive C. metamorphicD. sedimentary
Section CheckSection Check
33Question 2
Name the metamorphic rock texture in which mineral grains line up in parallel layers.
A. foliated B. nonfoliated C. sedimentary D. volcanic
Section CheckSection Check
33Question 3
Which of these is a nonfoliated metamorphic rock?
A. basalt B. marble C. shale D. slate
Section CheckSection Check
33Q 1. Answer
The answer is C. Heat, pressure and hot fluids trigger changes in various rock types forming metamorphic rocks.
Section CheckSection Check
33Q 2. Answer
The answer is A. Slate is a foliated metamorphic rock formed from shale.
Section CheckSection Check
33Q3. Answer
The answer is B. Marble forms from limestone. Basalt is an igneous rock. Slate is a foliated metamorphic rock that forms from the sedimentary rock, shale.
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