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< Back Next > Preview Main The Rock Cycle Chapter 4 Key Points Notes What is a rock? Composition Texture
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The Rock Cycle Chapter 4
Key Points Notes
What is a rock?
Composition
Texture
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A rock is a naturally occurring solid mixture of
one or more minerals or organic matter.
The Rock Cycle
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Composition is the chemical makeup of a rock.
Composition can describe either the minerals or
other materials in the rock.
The Rock Cycle
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Texture is based on the sizes, shapes, and
positions of the rock’s grains (___________).
MINERALS
The Rock Cycle
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Igneous Rock Formation
Key Points Notes
How are igneous
rocks formed?
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Igneous Rock Formation
Igneous rock forms when hot, liquid rock, or magma, cools
and solidifies. There are three ways magma can form:
1. When rock is heated
2. When pressure is released
3. When rock changes composition
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Igneous Rock Formation
Key Points Notes
Where do igneous
rocks form?
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Igneous Rock Formation
• Igneous rock that forms from magma that erupts, or
extrudes, on the Earth’s surface is called extrusive
igneous rock.
• Extrusive igneous rock, commonly found around
volcanoes, cools quickly on the surface and contains very
small crystals or no crystals.
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Igneous Rock Formation
• When magma intrudes, or pushes, into surrounding rock
below the Earth’s surface and cools, the rock that forms is
called intrusive igneous rock.
• Intrusive igneous rock has a coarse-grained texture
because it is well insulated by surrounding rocks and
cools very slowly.
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Igneous Rock Formation
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Igneous Rock Formation
•Sometimes, an igneous rock can be both fine and
coarse-grained. These rocks are called porphyritic.
How do you suppose
porphyritic rocks are
formed?
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Igneous Rock Formation
Key Points Notes
Special identifying
characteristics of
igneous rocks
•Found near a volcano
•Visible coarse-grained minerals
•Found in a lava flow
•Very shiny (teeny-tiny fine-
grained minerals)
•Glassy
•Vesicles (air pocket holes)
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Igneous Rock Formation
Key Points Notes
2 colors of
igneous rocks
• Light-colored FELSIC rocks are
rich in elements such as aluminum,
potassium, silicon, and sodium.
• Dark-colored MAFIC rocks are rich
in calcium, iron, and magnesium.
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Let’s Practice! Igneous Rock Formation
What type of igneous rock is pictured? (Composition, location)
Mafic, Fine-grained, Extrusive
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Let’s Practice! Igneous Rock Formation
What type of igneous rock is pictured? (Composition, location)
Felsic, Coarse-grained, Intrusive
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Let’s Practice! Igneous Rock Formation
What type of igneous rock is pictured? (Composition, location)
Felsic, Fine-grained, Extrusive
