CHAPTER 6, SECTION 2
Standards
3c. Students know how to explain the properties of
rocks based on the physical and chemical
conditions in which they are formed, including
plate tectonic properties.
Objective 1
Summarize 3 factors that affect whether
rock melts.
Objective 2
Describe how the cooling rate of magma
and lava affects the texture of igneous
rocks.
Classify igneous rocks according to their
composition and texture.
Objective 3
Objective 4
Describe intrusive and extrusive igneous
rock structures.
Assessment
Posters, Chapter Test
KEY TERMS
Create a flash card for the following
key terms (p. 129 in textbook):
Igneous Rock
Intrusive Igneous Rock
Extrusive Igneous Rock
Felsic
Mafic
If you finish early, study your flash cards!
IGNEOUS ROCK
Most
Igneous Rock (formed from
cooled magma) is crystalline
(made of crystals).
Magma forms when rocks melt.
3 Factors determine when rock
melts: temperature, pressure,
and pressure of fluids in the
rock.
IGNEOUS ROCK VIDEO CLIP
TYPES OF IGNEOUS ROCK
•Magma that
Intrusive cools deep
inside the crust
•Lava that cools
Extrusive at the Earth’s
surface
INTERACTIVE!
Create and Acrostic Poem using the word
IGNEOUS.
I
G
N
E
O
U
S

TEXTURES OF IGNEOUS ROCKS
Coarse-Grained
Fine-Grained
Other
• Intrusive
• Large, well-developed
mineral crystals
• Ex.: Granite
• Extrusive
• Small Mineral Grains
• Grains cannot be seen
with human eye
• Ex: Basalt
• Mixture of large and
small crystals
• Forms as a result of
slow cooling at first
then rapid cooling.
• Highly viscous
magma that cools
quickly results in
very few crystals
• If this magma has
little gas=GLASSY
• If this magma has
lots of
gases=VESICULAR
(holes)
TEXTURES VIDEO CLIP
QUICK CHECK!!
1.
2.
Name the 2 types of Igneous Rock:
____________________________________________
Give an example of a Course-Grained Igneous
Rock: ______________________________________
COMPOSITION OF
IGNEOUS ROCKS
 Mineral
Composition of igneous
rocks is determined by the chemical
composition of the magma from
which the rock formed.
 Three families of igneous rock:
 Felsic
 Mafic
 Intermediate
• Forms from
Magma that
has low
amounts of
silica and
lots of iron
and
magnesium
• Dark in
color
Intermediate Rock
• Forms from
Magma that
has large
amount of
Silica.
• Light
coloring
• Contains
feldspar
Mafic Rock
Felsic Rock
COMPOSITION FAMILIES
• Contains
less silica
than Felsic
but more
than Mafic
ASSESSMENT
In groups create posters for one of the following:
 Intrusive
 Extrusive
 Course-Grained
 Fine-Grained
DAILY QUIZ