Transcript How Are Igneous Rocks Classified?

Igneous Rocks
Igneous Rocks
* When magma or lava cools and freezes, it
becomes a mineral.
* A combination of minerals is a Rock.
* Igneous rocks are formed from the
crystallization of magma or lava.
-“Ignis,” the Greek word for “fire,” is like “Ignite,”
the English word for “to light”
How Are Igneous Rocks Classified?
How Are Igneous Rocks Classified?
1) By Texture
a) Extrusive -cooled above ground (lava)
• cooled quickly (a small amount of time)
• small crystals (they cooled too quickly for
large crystals to grow)
• may have a glassy texture (no crystals)
• Fine Grained
How Are Igneous Rocks Classified?
1) By Texture
b) Intrusive
• cooled inside the Earth (magma)
• cooled off slowly (a big amount of time)
• large crystals (they had time for big crystals to
grow)
• Coarse grained
How Are Igneous Rocks Classified?
1) By texture
c) Porphyritic
• has big and small crystals
• slow cooling magma erupted and finished
cooling off quickly
How Are Igneous Rocks Classified?
2) By Mineral Composition
a) Felsic
• Light color
• Lightweight
• High amount of silica
• Examples: granite, rhyolite
How Are Igneous Rocks Classified?
2) By Mineral Composition
b) Intermediate
• Medium color
• Medium weight
• Less silica
• Examples: andesite, diorite
How Are Igneous Rocks Classified?
2) By Mineral Composition
c) Mafic
• Dark color
• Heavy
• Low silica content
• Rich in iron and magnesium
• Examples: basalt, gabbro
How Are Igneous Rocks Classified?
2) By Mineral Composition
d) Ultramafic
• Very dark color
• Very heavy
• Little silica
• Rich in iron and magnesium
• Form deep underground
• Example: peridotite, kimberlite
Which of the igneous rocks pictured below
contains the greatest amount of iron and
magnesium?
or
Basalt
Granite
LIGHT
DARK
State the relative crystal size (fine, med., or
coarse grained) for igneous rocks that cooled
and solidified at locations A, B, and C.
B.
C.
A.
Where might a porphyritic texture form?
B.
Fine Grained
Medium Grained
C.
A.
Coarse Grained
State the name of the igneous rock that has
a coarse grained texture and the following
mineral composition:
Mineral
Percentage
Plagioclase
Feldspar
58 %
Amphibole
31%
Biotite
11%
Scrap
Paper
Scrap
Paper
58%
Scrap
Paper
58%
Igneous Rocks
Magma Classifications
1) Rhyolitic 70% Silica (SiO2)
2) Andesitic 60% SiO2
3) Basalitic 50% SiO2
Basalt is what makes up the ocean crust.
If only 50% is silica, there is room for
heavier elements in basaltic magma.