Ch 3 4 metamorphic rocks

Warm Up 10/8

What type of sedimentary rock is formed from weathered particles
of rocks and minerals?
a. intrusive sedimentary rock
c. clastic sedimentary rock
b. chemical sedimentary rock
d. biochemical sedimentary rock
2. What type of rocks are formed by processes powered by the sun?
a. No rocks are formed by energy from the sun.
b. sedimentary rocks
c. igneous rocks
d. metamorphic rocks
3. What type of composition does an igneous rock have that contains
mostly plagioclase feldspar and about 30 percent dark silicate
minerals?
a. ultramafic
c. basaltic
b. andesitic
d. granitic
Answers: 1) c. 2) b. 3) b.
1.


Metamorphic Rocks
Chapter 3, Section 4


Formation of Metamorphic Rocks







Most metamorphic changes occur at elevated
temperatures and pressures. These conditions are
found a few kilometers below Earth’s surface and
extend into the upper mantle.
Contact Metamorphism – hot magma moves into
rocks and changes the rock around it
Regional Metamorphism – occurs during mountain
building as large areas of rock are subjected to
temperature and pressure changes
Regional metamorphism results in large-scale
deformation and high-grade metamorphism


Formation of Metamorphic Rocks

Contact Metamorphism
Regional Metamorphism


Concept Check




Compare and contrast contact and regional

metamorphism.
Both processes change existing rocks into
metamorphic rocks. Contact metamorphism is
caused by magma and often produces slight
changes in rocks. Regional metamorphism is
large-scale deformation that can result in drastic
changes to the rocks involved.


Agents of Metamorphism







The agents of metamorphism are heat, pressure,
temperature, and hydrothermal solutions
The most important agent of metamorphism is heat
and comes from two sources, magma and change of
temperature with depth
Minerals become unstable and recrystallize to form new
minerals
With increased heat and pressure deep in the crust,
rocks will flow instead of fracture
Hot fluids will dissolve old minerals and deposit new
ones, changing the composition of the rock

Agents of Metamorphism


Stress as a
Metamorphic
Agent


Classification of Metamorphic Rocks






The texture of metamorphic rocks can be
foliated or nonfoliated
Foliated Metamorphic Rocks – The
realignment of the minerals, at right angles to
the direction of force, produces a banded
appearance
Nonfoliated Metamorphic Rocks –
metamorphic rocks that does not have a banded
texture and contains only one mineral


Classification of Metamorphic Rocks

Foliated – Gneiss

Nonfoliated – Marble


Concept Check




Contrast foliated and nonfoliated metamorphic
rocks.
Foliated metamorphic rocks have a layered or
banded appearance. Nonfoliated metamorphic
rocks do not have a banded texture.



Assignment




Read Chapter 3, Section 4 (pg. 80-84)
Do Section 3.4 Assessment #1-8 (pg. 84)
Study for Chapter 3 Quiz!