Download IGNEOUS ROCK FACTS Igneous rock is formed when melted rock

IGNEOUS ROCK FACTS
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The word "igneous" comes from the Latin word "ignis" which means "of fire."
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Igneous rock is formed when melted rock cools and solidifies. Melted rock is
called magma below the surface of the earth and lava on the surface of the earth.
Magma can be forced into rocks, blown out in volcanic explosions or forced to the
surface as lava.
The atoms and molecules of melted minerals are what make up magma.
These atoms and molecules rearrange themselves into mineral grains as the
magma cools, forming rock as the mineral grains grow together.
Magma cools at a slower rate deep inside the earth than it does just under the
surface, so very large mineral grains are formed. Rock formed from deep magma
is called plutonic igneous rock. A type of intrusive igneous rock, plutonic rock
takes millions of years to cool, and is sometimes discovered after years of erosion
reveals it.
Intrusive igneous rock is formed when magma cools and solidifies below the
surface of the earth. It cools slowly, so there is more time for mineral grains to
form. The mineral grains mineral in intrusive igneous rock are medium in size.
Extrusive igneous rock is formed when lava cools and solidifies on the surface of
the earth. It cools quickly, so there is less time for mineral grains to form. The
mineral grains in extrusive igneous rock are tiny.
Volcanic glass is a type of extrusive igneous rock. It cools so quickly that crystal
grains do not form.
There are over 700 different types of igneous rocks.
The upper section of the Earth's crust is made up of around 95% igneous rock.
Examples of igneous rocks include basalt (extrusive), granite (Intrusive), pumice
(volcanic glass), obsidian (volcanic glass), and tuff.
Basalt is found on the deep sea floor, in volcanic island arcs, and along the edges
of continents, while granitic rocks can be found on the continents.
Granite is a common rock that contains at least 25% quartz and is sometimes used
in construction because of its strength and on countertops because of its beauty.
It comes in a variety of colors.
The colors of granite depend on the minerals it contains.
Pumice is an unusual, lightweight rock formed when molten rock is rapidly blown
out of a volcano, forming bubbles as it quickly loses pressure and cools at the
same time.
Obsidian is a volcanic glass that forms without crystal growth since it cools so
quickly. It can have very sharp edges, making it useful as a cutting tool or
arrowhead.
Tuff is a rock formed from volcanic ash.
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BLIZZARD BAG 2/18/14
IGNEOUS ROCK WORKSHEET
NAME_____________________ PER_____
PART A -Write whether each statement is true or false. If the statement is false, rewrite the entire
statement to make it true.
______________1. The colors of granite depend on the mineral grain size.
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______________2. Lava is magma that has flowed onto the surface of the earth.
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______________3. When lava cools quickly, large mineral grains can form so the crystals are bigger.
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______________4. Pumice is formed when magma under pressure is blown out of an erupting volcano,
creating bubbles as the pressure decreases.
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______________5. Basalt is an intrusive igneous found mostly on the sea floor.
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______________6. Granite is an extrusive igneous rock found mostly on the continents.
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______________7. Obsidian has no mineral grains since it cools so quickly.
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______________8. When magma cools slowly, large mineral grains can form so the crystals are bigger.
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PART B – Write the letter of each concept to complete the Venn Diagram to compare and contrast the
two major groups of igneous rock.
A. granite
B. forms under Earth’s surface
C. smaller crystals
D. forms from molten rock
E. forms from cooled lava
F. obsidian
G. forms on Earth’s surface
H. basalt
J. larger crystals
K. pumice
L. 95% of Earth’s upper crust
M. forms from cooled magma
N. forms from melted minerals
O. cools quickly
P. cools slowly
EXTRUSIVE
INTRUSIVE
BOTH
sive
sive
sive
PART C – Answer each question with complete sentences. Do not rephrase the question.
1. Why do plutonic igneous rocks take longer to cool than other igneous rocks?
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2. If you found an igneous rock with tiny crystals and one with larger crystals, what could you tell about
where they were formed and to which group of igneous rocks they belong?
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