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1. Igneous Rocks
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There are many kinds of rock in Earth’s
crust
These rocks are made up of different
minerals
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Rocks can be grouped by the way they
form throughout the rock cycle
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Igneous rocks form from melted, liquid
rock
Vocabulary
Igneous rocks
Rock formed when hard liquid rock
cools and hardens
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This process may take place inside
Earth
or on Earth’s surface
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Inside Earth, magma cools so slowly
that it may take a thousand years for a
rock to form
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One of the most common kinds of
igneous rocks is granite
Granite is made by magma cooling
inside Earth
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Granite is light colored with large
crystals
It is made up mostly of the minerals
quartz and feldspar
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Granite is strong and does not break
easily, even under pressure
It is often used in buildings and bridges
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Basalt is made when lava pours onto
the ground or onto the ocean floor
Because the lava cools quickly, the
crystals in basalt are small
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When lava erupts underwater it makes
pillow-shaped lumps, called
pillow lava
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Sometimes, lava cools so quickly that
crystals never have a chance to form
Pumice and obsidian are igneous rocks
that do not have crystals
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Pumice is full of bubbles and is so light
that it floats
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Obsidian is a glassy, black rock
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Video: How to Make Rock Candy
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