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IGNEOUS ROCK
• Volcanoes eject molten rock
• Molten rock=magma
• Flows when hot and becomes a solid when it
cools
• Hardened, cooled magma is called igneous
rock.
Magma
• Temperatures of magmas range from about
650° to 1,200°C, depending on their chemical
compositions and pressures exerted on them.
• Earth’s heat to melt rocks comes from interior
• Radioactive decay of elements is main source
of heat.
• Magma is less dense than surrounding rock,
which forces it upwards
• When magma reaches Earth’s surface and
flows from volcanoes, it is called lava.
Instrusive Rocks
• Atoms and compounds in the liquid
rearrange into new crystals called mineral
grains, when magma cools
• Rocks form when mineral grains grow
together.
• Rocks from magma below the surface are
called intrusive igneous rocks.
Extrusive Igneous Rock
• Extrusive Rock forms
when magma cools
on Earth’s surface
• Magma exposed to
air and water, thus
cools quickly.
Volcanic Glass
• Pumice, obsidian, and scoria are examples of
volcanic glass.
• Rocks cooled so quickly few or no mineral
grains formed.
• Pumice and scoria, gases become trapped in
the gooey molten material as it cools.
Basaltic Rock
• Basaltic igneous rocks are dense, darkcolored rocks.
• Rich in iron and magnesium and poor in
silica.
• FE and MG gives them dark color
• Basaltic Lava is fluid and free flowing.
• http://www.youtube.com/watch?v=r3HyGTr
gt7k
Granitic and Andesitic Rock
• Granitic igneous rocks are light-colored
rocks of lower density than basaltic rocks.
• Thick and stiff magma, high in silica, and low
in Mg and FE.
• Andesitic igneous rocks have mineral
compositions between those of basaltic and
granitic rocks
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Igneous rock is formed by __________.
A. cooling of hot magma
B. change in pressure
C. compression of loose materials
D. pressure from watery fluids
• What is the difference between intrusive
and extrusive igneous rock?
Intrusive igneous rocks form from magma
below Earth’s surface. Extrusive igneous
rocks form from lava flowing at Earth’s
surface.
• Which of the following is a volcanic rock
that contained trapped gases during its
formation?
• A. marble
• B. pumice
• C. sandstone
• D. slate
Igneous Rock Venn Diagram (22)
• Create a Venn Diagram comparing and
contrasting Basaltic, Andesitic, and Granitic
Rock.
• Draw a picture to illustrate the difference
between the different igenous rocks.
• Write a level 1 or 2 question and its answer for
EACH of the following ideas:
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Igneous Rock
Lava
Instrusive rock
Extrusive rock
Volcanic glass