Metamorphic Rocks
• How do metamorphic rocks form?
• How do types of metamorphic rock
differ?
Metamorphic Rocks
• metamorphism
• nonfoliated rock
• plastic
deformation
• contact
metamorphism
• foliated rock
• regional
metamorphism
Metamorphic Rock Formation
• Metamorphism is any process that
affects the structure or composition of
a rock in a solid state as a result of
changes in temperature, pressure, or
the addition of chemical fluids.
• Most metamorphic rocks form deep
within Earth’s crust.
• Like igneous rock, metamorphic rocks
form under high temperature and
pressure conditions.
Metamorphic Rock Formation (cont.)
• Plastic deformation is the permanent
change in the shape of rock by bending
and folding.
• Plastic deformation occurs during uplift
events when tectonic plates collide and
form mountains.
Metamorphic Rock Formation (cont.)
• The rock that changes during
metamorphism is called the parent
rock.
• The temperatures required to
metamorphose rock depend
on the parent rock’s composition.
Both temperature and pressure increase
with depth in Earth’s crust and mantle.
Metamorphic Rock Formation (cont.)
Under what conditions do
metamorphic rocks form?
Metamorphic rocks
are classified into
two groups based
on texture:
foliated rocks and
nonfoliated rocks.
Metamorphic Rock Identification
• Foliated rocks contain parallel layers
of flat and elongated minerals.
• Metamorphic rocks that have mineral
grains with a random, interlocking
texture are nonfoliated rocks.
Metamorphic Rock Identification (cont.)
foliate
from Latin foliatus, means
“consisting of thin, leaf-like layers”
Metamorphic Rock Identification (cont.)
• During contact metamorphism,
magma comes in contact with existing
rock, and its thermal energy and gases
interact with the surrounding rock and
forms nonfoliated metamorphic rock.
• Regional metamorphism is the
formation of metamorphic rock bodies
that are hundreds of square kilometers
in size.
Metamorphic Rock Identification (cont.)
Compare and contrast
contact metamorphism and
regional metamorphism.
• Foliated metamorphic rocks have
distinct layers of flat and elongated
minerals.
• A nonfoliated metamorphic rock has
minerals arranged in a random,
interlocking texture.
• Contact metamorphism occurs when
rocks come in contact with magma
without melting.
When rocks bend or fold without
melting, the permanent change in
the rock’s shape is called what?
A. metamorphism
B. foliation
C. plastic deformation
D. rock deformation
What kind of rocks contain
parallel layers of flat and
elongated minerals?
A. foliated rocks
B. metamorphic rocks
C. crystallized rocks
D. nonfoliated rocks
Which type of metamorphism
occurs when magma comes in
contact with existing rock, and its
thermal energy and gases interact
with the surrounding rock?
A. regional
C. plastic
B. crystal
D. contact
Do you agree or disagree?
7. With the right pressure and temperature
conditions, minerals in a rock can
change shape without breaking or
melting.
8. Metamorphic rocks have layers that
form as minerals melt and then
recrystallize.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
• Igneous rocks form from
molten rock that cools and
crystallizes.
• Sedimentary rocks form
from compaction and
cementation of sediments
or evaporation and
crystallization of minerals
dissolved in water.
• Metamorphic rocks form
from exposure of existing
rocks to high pressures,
temperatures, or the
addition of chemical fluids.
Lesson 1: Rocks and the Rock Cycle
• There are three major rock types—igneous,
sedimentary, and metamorphic. Geologists study
rock texture and mineral composition to identify
rocks of each type.
Nancy Simmerman/Getty Images
• Rocks can melt or recrystallize. Rocks exposed on
Earth’s surface can
break down due to
forces such as water,
ice, wind, and gravity.
New rocks form under
changing temperature
and pressure conditions
or the addition of
chemical fluids.
Lesson 2: Igneous Rocks
• Igneous rocks form when volcanic material cools
and crystallizes.
• Crystal size is dependent on how quickly the
magma or lava cools.
• Igneous rocks range in color from light to dark,
depending on their mineral composition.
Lesson 3: Sedimentary Rocks
• Weathering, erosion, transportation, deposition,
compaction, cementation, and crystallization are the
important processes in the formation of sedimentary
rocks.
• A sedimentary rock’s texture and mineral
composition depends on
where it formed
and the forces
that created it.
National Geographic/Getty Images
Lesson 4: Metamorphic Rocks
• Metamorphic rocks form from a parent rock that has
been exposed to increases in temperature,
pressure, or the addition of chemical fluids.
• Some metamorphic rocks have foliated textures and
are deformed. Others are composed of coarse and
blocky crystals that are uniform in color.
Which term refers to the series of
processes that change one type
of rock into another type of rock?
A. metamorphoses
B. sediment deposit
C. rock cycle
D. rock deposit
Geologists can determine if an
igneous rock is extrusive or
intrusive by studying its
composition and which of these?
A. size
C. weight
B. color
D. texture
Which type of rock is sedimentary
rock that was formed by
organisms or contains the
remains of organisms?
A. chemical
C. carbonate
B. biochemical
D. clastic
Which process occurs when minerals
dissolved in water crystallize
between sediment grains?
A. cementation
B. compaction
C. crystallization
D. erosion
Which type of rocks contain
parallel layers of flat and
elongated minerals?
A. igneous
B. foliated
C. nonfoliated
D. sedimentary
Which term refers to magma that
erupts on Earth’s surface?
A. sediment
B. metamorphic rock
C. lava
D. crystals
When magma or lava cools and
crystallizes, it creates which type
of rock?
A. igneous
B. sedimentary
C. metamorphic
D. mineral
An igneous rock is classified as
extrusive if which part is difficult
or impossible to see without a
magnifying glass?
A. minerals
B. crystals
C. holes
D. grains
Which term refers to any process
that affects the structure or
composition of solid rock?
A. chemical reaction
B. plastic deformation
C. foliation
D. metamorphism
Which process refers to the
formation of metamorphic rock
bodies that are hundreds of square
kilometers in size?
A. cementation
B. regional metamorphism
C. contact metamorphism
D. plastic deformation
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4-4 Metamorphic Rocks Summary