Rocks and The Rock Cycle

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Rocks and The Rock Cycle
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Igneous Rocks

• Volcanic Rocks
• Form when magma/lava cools
• Intrusive rocks - form below Earth's surface
• Extrusive rocks - form at Earth's surface
• Compose 95 of Earth's crust

All rocks originally come from igneous rock.
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Igneous Rocks
? Igneous rocks can be classified based on their
composition and texture.
1. Texture
Coarse-grained texture is caused by slow
cooling resulting in larger crystals.
Fine-grained texture is caused by rapid
cooling resulting in smaller, interconnected
mineral grains.
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Course-Grained Igneous Texture
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Fine-Grained Igneous Texture
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Obsidian Exhibits a Glassy Texture.
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Basalt
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Igneous Rocks
The term "igneous" comes from the Latin word
meaning "fire."
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Igneous Rocks

• Continental Crust Mostly Granite and Andesite
• Oceanic Crust Mostly Basalt
• Pillow Basalt - common in ocean
• Composition depends on rate of cooling

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Igneous Rocks
Minerals of Granite
Granite is an intrusive igneous rock
GRANITE
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Igneous Rocks
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Igneous Rocks

• Plutons - large intrusive rock bodies
• Dike - intrusion of magma up through existing
  rock (page 547)
• Sill - intrusion of magma parallel to horizontal
  rock layers
• Laccolith - mushroom shape (page 547)
• Batholith - very large, many mountain range cores

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Igneous Rocks
Batholith
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Igneous Rocks

• Extrusive Rocks - form at Earths surface
• Examples
• Obsidian
• Pumice
• Scoria

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Igneous Rocks
Extrusive Rock
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Igneous Rocks
Granite at Yosemite
How are they formed?
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Igneous Rocks
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3.3 Sedimentary Rocks
? Weathering, Erosion, and Deposition
Erosion involves the weathering and the
removal of rock.
Deposition occurs when an agent of
erosionwater, wind, ice, or gravityloses energy
and drops sediments.
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3.3 Sedimentary Rocks
? Compaction and Cementation
Compaction is a process that squeezes, or
compacts, sediments.
Cementation takes place when dissolved
minerals are deposited in the tiny spaces among
the sediments.
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3.3 Sedimentary Rocks
? Two Main Groups
1. Clastic sedimentary rocks are composed of
weathered bits of rocks and minerals.
Classified by particle size
Common rocks include
- Shale (most abundant)
- Sandstone
- Conglomerate
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Shale with Plant Fossils
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3.3 Sedimentary Rocks
? Two Main Groups
2. Chemical sedimentary rocks form when dissolved
substances precipitate, or separate, from water.

• Common rocks include

- limestonemost abundant chemical rock
- microcrystalline quartz known as chert, flint,
jasper, or agate
- evaporites such as rock salt or gypsum
- coal
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Fossiliferous Limestone
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Sedimentary Rocks

• Remains of pre-existing rocks
• Usually forms layers
• Results from weathering and erosion
• May be mechanical or chemical

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Sedimentary Rocks
EXAMPLES
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Sedimentary Rocks

• Sediment may be clastic or chemical
• Clastic sediment consists of particles - may be
  compacted or cemented together
• Examples sandstone, shale, conglomerate
• Chemical sediments form when minerals precipitate
  from water
• Examples limestone, halite, dolomite

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Sedimentary Rocks
Conglomerate
Breccia
SANDSTONE
shale
Classification based on particle size
Clastic - particles cemented or compacted together
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Sedimentary Rocks
Limestone Formation
Forms from the buildup of Calcium Carbonate
Shells of once living sea organisms.
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Sedimentary Rocks
The Mississippi Delta is a large area of
sedimentary debris which has been carried from
North America.
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Sedimentary Rocks
Cave stalactites and stalagmites form when
minerals in water make deposits.
How are they formed?
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Part II
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3.4 Metamorphic Rocks
? Heat

• Provides the energy needed to drive chemical
  reactions

? Pressure

• Causes a more compact rock with greater density

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Origin of Pressure in Metamorphism
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Metamorphic Rocks

• Rocks which have undergone change
• Result when sedimentary or igneous rocks
  experience heat/pressure
• Change - recrystallization or deformation

Marble
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Metamporhic Rocks
Expose the following to heat and
pressure potters clay limestone shale
And the following new rocks will
form ceramic marble slate
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3.4 Metamorphic Rocks
? Two main categories
1. Foliated Metamorphic Rock

• Has a banded or layered appearance

2. Nonfoliated Metamorphic Rock

• Does not have a banded texture

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Metamorphic Rocks
Layered texture - results from pressure on both
sides of rock - pressing components into layers
Foliated
Marble, Quartzite pressure insufficient to
foliate
Non-foliated
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Metamorphic Rocks
Foliated
slate
gneiss
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Metamorphic Rocks
Quartzite
Marble
Nonfoliated
How are they formed?
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Gneiss Typically Displays a Banded Appearance
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MarbleA Nonfoliated Metamorphic Rock
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The Rock Cycle
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Rock Cycle
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The Rock Cycle
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Rock Cycle