Download Rocks: Lesson 2: Thinking Map Completed

Chapter 2: Rocks: Section 2: Igneous Rock
Origins of Igneous Rock
 Igneous- Latin word for
“fire.” Magma cools
into various types of
igneous rocks
depending two things
1) the composition of the
magma
2) the amount of time it
takes the magma to
cool and solidify
Three ways magma is formed
1) rock is heated
2) pressure is released
3) when rock changes
composition
Name ____________________________________ #_______ date _____________
Extrusive Igneous Rock
Composition and Texture of Igneous
Rock
Igneous Rock Formations
Igneous rocks are divided into two
groups based what the rock is mad
of and how fast they cooled.
When magma cools beneath
the Earth’s surface this is called
intrusive rock.
When magma cools on the
Earth’s surface this is called
extrusive rock.
Felsic: Light-colored rocks and less
dense.
Intrusive rock-
Extrusive rock-
 Rich in elements such as
silicon, aluminum, sodium,
and potassium.
Mafic: Dark-colored rocks and are
denser.
 Rich in elements such as iron,
magnesium, and calcium
**The longer it takes for magma or
lava to cool, the more time mineral
crystals have to grow. The more
time they have to grow the coarser
the texture of the igneous rock that
is formed.
 Usually has a coarsegrained texture. When
the magma cools it is
surrounded by rock and
cools slowly.
 They are named for their
size and the way they
intrude to push into the
surrounding rock.
 Plutons
 Dike
 Volcanic neck
 Sill
 Batholith
 Laccolith
 Most volcanic rock is
extrusive.
 Extrusive rock cools
quickly on the surface
and contains very small
crystals or none at all.
 When lava erupts from a
volcano a formation
called lava flow is made.
 Sometimes lava comes
from long cracks in the
Earth called fissures.
These can cover a vast
area making a lava
plateau.