Chapter 6, Section 1
Igneous Rocks
• Igneous Rock
• A rock that forms
from the cooling
and hardening of
molten rock
• Magma
• Lava
• Molten rock found
under the Earth’s
Surface
• Molten Rock found
on the Earth’s
surface
• Felsic magma
• Mafic magma
• Light in color, very
thick; has a high
silica content
• Dark in color and
very thin; low
silica content
• Intrusive igneous
rocks
• Rocks that form
underground from
magma
• Take a long time
to cool because
underground
(holds the heat in)
• Extrusive igneous
rock
• Forms on the
Earth’s surface
from lava
• Cools and hardens
very quickly b/c
on the Earth’s
surface
• Crystal size
• Porphyry
• Intrusive igneous
rocks tend to have
LARGE crystals
• The longer it takes
the rock to cool,
the larger the
crystals will be
• VERY large
crystals
• Granite family
•
•
•
•
•
Felsic magmas
Granite
Rhyolite
Pumice
Obsidian
• Gabbro family
•
•
•
•
•
Mafic magmas
Gabbro
Basalt
Scoria
Diabase
• Diorite family
• Intermediate
magma
• Diorite and
andesite
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Chapter 6, Section 1 Igneous Rocks • Igneous Rock