Lesson Outline
LESSON 2
Igneous Rocks
A. Igneous Rock Formation
1. Igneous rock forms from molten rock in the form of
or
.
above Earth’s surface.
a. Lava cools
below Earth’s surface.
b. Magma cools more
2. When volcanic material erupts and cools and crystallizes on Earth’s surface, it forms
a type of igneous rock called
.
a. Some extrusive rock cools so quickly that
do not
have time to grow.
b.
is rock that forms when lava cools too quickly to
grow crystals.
c. Sometimes
trapped in the lava escape, leaving holes
in the extrusive rock.
3. Igneous rocks that form as magma cools underground are called
. They contain large
because
the magma cools slowly.
B. Igneous Rock Identification
1. As with all types of rocks, the two characteristics that can help to identify igneous
rocks are
and
.
2. If the crystals are small or impossible to see without a magnifying lens, the rock
is
. If all the crystals are large enough to see and have
an interlocking texture, the rock is
.
3. Igneous rocks are classified, in part, due to their
content.
-colored minerals contain more silica.
4. Magma composition, the location where the lava or magma cools and
crystallizes, and the
that forms.
determine the type of igneous rock
Lesson Outline
LESSON 4
Metamorphic Rocks
A. Metamorphic Rock Formation
1. Metamorphic rocks form when rocks are exposed to high
and pressure.
a. Most metamorphic rocks form deep in Earth’s crust
and
.
b. Metamorphic rocks
and form layers during their
formation.
2. Rocks under high temperature and pressure can behave like
a(n)
.
a. Plastic materials bend and
without melting.
b. As they form, metamorphic rocks might permanently change shape by bending
and folding during
.
c. Bending and folding of rocks is common during the formation
of
.
3. The temperature needed to change a rock to a metamorphic rock depends on the
composition of the
rock.
a. Temperature must reach at least
for metamorphic
rock to form.
with increased depth in Earth’s
b. Pressure becomes
crust and mantle.
B. Metamorphic Rock Identification
1. Metamorphic rocks are classified based on texture and
composition.
2. Metamorphic rocks that contain distinct layers with parallel, flat, or elongated
minerals are called
.
64
Rocks
Name
Date
Class
Lesson Outline continued
3.
are metamorphic rocks that have mineral grains with
a random, interlocking texture.
a. One way that nonfoliated rocks form is by
b. At these contacts, heat and gases from
.
interact with
surrounding rock, forming metamorphic rocks.
4.
is the formation of extremely large metamorphic rocks.
This process can create an entire
Rocks
of metamorphic rock.