Elevated Landforms
Castle Rock,
CO
Shiprock NM
Mt. Cotopaxi
Ecuador
Pikes Peak
CO
Igneous Rocks
If you can’t take the heat, stay out
of the kitchen.
H. S Truman
Igneous Rocks
• Formed from cooled magma (melted rock)
Inner core
Outer core Mantle and
outer core
Mantle are melted
Crust
Igneous Rocks
• Parts of the crust can be melted
Igneous Rocks
• (Notice the ocean floor?)
The most common
type of igneous
rock—basalt!
Igneous Rocks
• Magma on the surface is called lava
Igneous Rocks
• We will study the motion of these
lithospheric plates in the next unit
Igneous Rocks
• (Notice the difference in the crust?)
Igneous Rocks
• The slower it cools, the larger the crystals
grow
• Intrusive— cools inside the crust
• Extrusive— cools outside the crust
Igneous Rocks
• The slower it cools, the larger the crystals
grow
• Intrusive— cools inside the crust
--cools slowly
• Extrusive— cools outside the crust
--cools fast
Igneous Rocks
• The slower it cools, the larger the crystals
grow
• Intrusive— cools inside the crust
--cools slowly —large crystals
• Extrusive— cools outside the crust
--cools fast —small crystals
Igneous Rocks
• The slower it cools, the larger the crystals
grow
• Intrusive— cools inside the crust
--cools slowly —large crystals--rough
• Extrusive— cools outside the crust
--cools fast —small crystals--smoother
Igneous Rocks
• Q: What about a rock that cools slowly for a
while, then gets exposed so it cools quickly
at the end?
Igneous Rocks
• Q: What about a rock that cools slowly for a
while, then gets exposed so it cools quickly
at the end?
• A: You get large
crystals in a fine
gray background
Igneous Rocks
• Vary in color due to the differences in the
mineral content of the magma
Light Minerals Dark Minerals
Quartz Amphibole
Potassium Feldspar Biotite mica
Muscovite mica Pyroxene
Olivine
Igneous Rocks
• Magma varies depending on where it’s found
Ocean Floor Continental
darker color lighter color
denser lighter (less dense)
thinner fluid thicker fluid
less gas bubbles more gas bubbles
Igneous Rocks
• Magma varies depending on where it’s found
Ocean Floor Continental
darker color lighter color
denser lighter (less dense)
thinner fluid thicker fluid
less gas bubbles more gas bubbles
More gas bubbles makes a more
violent volcanic eruption!
Igneous Rocks
• Classified by color and texture
• See Table on pU20
Igneous Rocks
• Classified by color and texture
• See Table on pU20
Continental Igneous Rocks
• Types: (By color and texture)
Light and Coarse—pegmatite (and
granite)
Light and Medium—Granite
Light and Fine—rhyolite
Intermediate Igneous Rocks
• Types: (By color and texture)
Medium and Coarse—pegmatite (and
diorite)
Medium and Medium—Diorite
Medium and Fine—Andesite (and
basalt)
Oceanic Igneous Rocks
• Types: (By color and texture)
Dark and Coarse—pegmatite (and
gabbro)
Dark and Medium—Gabbro
Dark and Fine—Basalt
Igneous Rocks
• Types:
• Special: Glassy—obsidian
Light and Frothy—Pumice
Dark and Frothy—Scoria
Very Dark—peridotite
Continental—tossed into the air
to cool by Rocks
Igneousexpanding gasses
• Types:
• Special: Glassy—obsidian
Continental Light and Frothy—Pumice
—gas is Dark and Frothy—Scoria
trapped in Very Dark—peridotite
the rock
Oceanic