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Igneous Rocks Notes
• Molten material (aka magma or lava) cools.
• Lava above the Earth’s surface
• Magma below the Earth’s surface
Where - Intrusive Igneous Rock
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•
•
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INtrusive – INSIDE the Earth
Forms underground from magma
Heat = slow cooling = LARGE crystal grains.
Intrusive Mineral Crystals
Where - Extrusive Igneous Rock
• Extrusive = Exit!
• Lava cools on or near earth’s surface.
• small grains due to cooling very quickly
• Extrusive Mineral Crystals
Composition - Basaltic
• Basaltic
• Dense, Dark Colored, Heavy
• HIGH IRON – low silica
BASALT
Melted
Cooled
Composition - Granitic
• Granitic
• Light Colored, less dense
• High in Silicon and Oxygen
Granite
Ways to classify Igneous Rocks
1. Texture tells us WHERE
intrusive/magma or extrusive/lava
2. Composition tells us WHAT
(basaltic or granitic)
Extrusive Rock
Intrusive Rock
Intrusive Rocks
Forms underground
from magma
Generally LARGE
grains are formed
INtrusive – think
INSIDE the Earth
Extrusive Rocks
Formed when Lava
cools on or near earth’s
surface.
Generally small
grains due to cooling
very quickly
Where igneous rocks form.
Basaltic
Andesitic
Granitic
Dense,
Heavy, Dark
Colored
Made up of
iron and
magnesium
Igneous Rocks
that show
characteristics
of both basaltic
and granitic
Light
Colored, less
dense’
Made up of
silicon and
oxygen
Examples of Types of Molten Materials.
Intrusive Rocks
Extrusive Rocks
Gabbro
Pegmatite
Granite
Diorite
Andesite
Basalt
Tuff
Scoria
Rhyolite
Pumice
Obsidian
Examples of Igneous Rocks