IGNEOUS
ROCKS
Video Quiz
True or False?
1
Igneous rocks are still forming in fiery places
today.
2
Weathering makes rocks harder.
3
Sediments harden into rock through lithification.
4
During metamorphism, limestone might change
into marble
5
In the rock cycle, igneous, sedimentary and
metamorphic rock can change into one another.
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5
Igneous Rocks
Section 5.1: What are igneous rocks?
Section 5.2: Classification of Igneous Rocks
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Section 5.1
What are igneous rocks?
Objectives
Summarize igneous rock formation.
Describe the composition of magma.
Igneous rocks are the rocks that form when molten
material cools and crystallizes.
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What are igneous rocks?
Igneous Rock Formation
Lava is magma that flows out onto Earth’s
surface.
Igneous rocks form when lava or magma cools
and minerals crystallize.
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What are igneous rocks?
Igneous Rock Formation
Magma formation
Magma can be formed either by melting of
Earth’s crust or by melting within the mantle.
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• Draw and Label a volcano, lava, and magma.
(in your workbook)
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What are igneous rocks?
Igneous Rock Formation
Magma formation
The four main factors involved in the
formation of magma are temperature,
pressure, water content, and mineral
content.
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What are igneous rocks?
Magma formation
Temperature generally
increases with depth in
Earth’s crust. This
temperature increase is
known as the geothermal
gradient.
How deep in Earth do you
have to go to reach 1000°C?
How hot is it at 3000km?
FLASH CARDS
1. What is
lava?
2. What is
magma?
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Classification of Igneous Rocks
Objectives
Classify different types and textures of
igneous rocks.
Recognize the effects of cooling rates on the
grain sizes in igneous rocks.
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Section 5.2
Classification of Igneous Rocks
Classification of igneous rocks is based on
mineral composition, crystal size, and texture.
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Classification of Igneous Rocks
Where Igneous
Rocks Form
When magma cools and
crystallizes below Earth’s
surface, intrusive rocks
form.
Magma that cools and
crystallizes on Earth’s
surface forms extrusive
rocks.
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Classification of Igneous Rocks
Texture
Texture refers to the size, shape, and
distribution of the crystals or grains that
make up a rock.
We use texture to tell us if a rock was
intrusive or extrusive.
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Section 5.2
Classification of Igneous Rocks
Texture
Crystal size and
cooling rates
Extrusive Rocks:
•When lava flows on Earth’s
surface, it cools QUICKLY.
•Crystals are MICROSCOPIC
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Classification of Igneous Rocks
Texture
Crystal size and cooling rates
Intrusive Rocks:
•When magma cools
slowly below Earth’s
surface
•Large crystals to
form.
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Classification of Igneous Rocks
Texture
Porphyritic texture
•large, well-formed
crystals
•surrounded by finergrained crystals of the
same mineral or
different minerals.
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Classification of Igneous Rocks
Texture
Vesicular texture
•spongy appearance
•results of gas bubbles
trapped in lava
FLASH CARDSGive 2 examples
What is the
of
intrusive
grain size of an
igneous rocks.
intrusive rock?
What is the
grain size of an
extrusive rock?
Give 2 examples
of extrusive
igneous rocks.
How are intrusive
igneous rocks
formed?
How are
extrusive igneous
rocks formed?