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UNDERSTANDING EARTH, SIXTH EDITION
GROTZINGER • JORDAN
GEOLOGY MEDIA SUITE
Chapter 7
Deformation
Modification of Rocks by Folding and Fracturing
© 2010 W.H. Freeman and Company
Rock folding
Key Figure 7.10 (page 159)
Go to next slide to begin
Youngest
rock
Oldest
rock
Horizontal fold
Fold axis
b
m
Li
b
m
i
L
l
a
i
Ax ne
p la
Plunging fold
al
t
n
l
o
a
z
i
r i Ax e
o
n
H
a
l
° p
45
b
m
Li
b
m
Li
A
pl xia
an l
e
Symmetrical folds
Asymmetrical folds
Ax
ial
pla
ne
Limb
b
m
Li
b
m
Li
Overturned folds
b
e
m
n
Li pl a
l
a
i
x
A
Rock folding
Which statement regarding synclines is true?
A. Limbs dip toward the axial plane where the oldest strata
are exposed.
B. Limbs dip toward the axial plane where the youngest
strata are exposed.
C. Limbs dip away from the axial plane where the oldest
strata are exposed.
D. Limbs dip away from the axial plane where the youngest
strata are exposed.
Rock folding
Which statement regarding synclines is true?
A. Limbs dip toward the axial plane where the oldest strata
are exposed.
B. Limbs dip toward the axial plane where the
youngest strata are exposed.
C. Limbs dip away from the axial plane where the oldest
strata are exposed.
D. Limbs dip away from the axial plane where the youngest
strata are exposed.
Rock folding
True or False: In an overturned fold, both limbs dip in the
same direction.
A. True
B. False
Rock folding
True or False: In an overturned fold, both limbs dip in the
same direction.
A. True
B. False
Rock folding
What characterizes a fold as being a plunging fold?
A. The limbs dip at different angles from one another.
B. The limbs both dip in the same direction.
C. The axial plane is not vertical.
D. The fold axis is not horizontal.
Rock folding
What characterizes a fold as being a plunging fold?
A. The limbs dip at different angles from one another.
B. The limbs both dip in the same direction.
C. The axial plane is not vertical.
D. The fold axis is not horizontal.
Continental deformation and the
development of a geologic province
Key Figure 7.15 (page 162)
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Tensional tectonics
Ductile lower crust
Compressive tectonics
Shearing tectonics
A left bend in the fault
results in local compression.
A right bend in the fault
results in local extension.
Continental Deformation
Figure 7.16 (page 163)
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MEDITERRANEAN SEA
Sinai
Saudi Arabia
Egypt
RED SEA
Sinai
Egypt
RED SEA
Continental
crust
Oceanic
crust
Asthenosphere
Saudi Arabia
Rift valley
Downfaulted
blocks
The African Plate and the Arabian
Plate are drifting apart.
Sinai
Egypt
RED SEA
Continental
crust
Oceanic
crust
Asthenosphere
Saudi Arabia
Rift valley
Downfaulted
blocks
The African Plate and the Arabian
Plate are drifting apart.
Sinai
Egypt
RED SEA
Continental
crust
Oceanic
crust
Saudi Arabia
Rift valley
Downfaulted
blocks
Asthenosphere
Tensional forces have created a rift valley.
Continental Deformation
Figure 7.17 (page 164)
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C D
B
A
C D
B
A
1 Compressive forces
create a fault.
C D
B
A
1 Compressive forces
create a fault.
D
B
C
D
B
C
C D
B
A
5 0 km
C D
B
A
1 Compressive forces
create a fault.
2 Old layers now
overlie younger layers.
D
B
C
D
B
C
C D
B
A
5 0 km
C D
B
A
1 Compressive forces
create a fault.
2 Old layers now
overlie younger layers.
D
B
C
B
C
C D
B
A
5 0 km
D
C
B
A
D
B
C D
B
C D
B
A
1 Compressive forces
create a fault.
2 Old layers now
overlie younger layers.
D
B
C
B
C
C D
B
A
3 Erosion reveals the
view we see today.
5 0 km
D
C
B
A
D
B
C D
B
Continental Deformation
Predict the kind of geologic structure most prevalent in a
region of continental rifting.
A. Reverse faults
B. Thrust faults
C. Normal faults
D. Folds
Continental Deformation
Predict the kind of geologic structure most prevalent in a
region of continental rifting.
A. Reverse faults
B. Thrust faults
C. Normal faults
D. Folds
Continental Deformation
Geologic structures unlikely to be formed along the
global mid-ocean ridge system include which of the
following?
A. Normal Faults
B. Thrust Faults
C. Strike-slip faults
D. Answers 2 and 3
E. Answers 1, 2, and 3
Continental Deformation
Geologic structures unlikely to be formed along the
global mid-ocean ridge system include which of the
following?
A. Normal Faults
B. Thrust Faults
C. Strike-slip faults
D. Answers 2 and 3
E. Answers 1, 2, and 3
Continental Deformation
Which is a correct difference between a thrust fault and a
reverse fault?
A. Thrusts form from compression whereas reverse faults form
from tension.
B. Thrusts have a lower-angle fault plane than do reverse faults.
C. Reverse faults are strike-slip faults whereas thrusts are dipslip faults.
D. Reverse faults lead to inverted stratigraphy whereas thrust
faults do not.
Continental Deformation
Which is a correct difference between a thrust fault and a
reverse fault?
A. Thrusts form from compression whereas reverse faults form
from tension.
B. Thrusts have a lower-angle fault plane than
do reverse faults.
C. Reverse faults are strike-slip faults whereas thrusts are dipslip faults.
D. Reverse faults lead to inverted stratigraphy whereas thrust
faults do not.
Continental Deformation
Select the statement(s) below that are true regarding
thrust faults.
A. Thrust faults place older rocks on top of younger rocks.
B. Thrust faults results in terrain shortening in the direction of
primary stress.
C. Thrust faults commonly form at convergent plate
boundaries.
D. All of the above statements are true.
Continental Deformation
Select the statement(s) below that are true regarding
thrust faults.
A. Thrust faults place older rocks on top of younger rocks.
B. Thrust faults results in terrain shortening in the direction of
primary stress.
C. Thrust faults commonly form at convergent plate
boundaries.
D. All of the above statements are true.
Tectonic Forces Determine the
Style of Faulting
Purely tensional stresses associated with a _________
plate boundary will generate a _______ fault.
A. convergent; strike-slip
B. convergent; normal
C. divergent; reverse
D. divergent; normal
Tectonic Forces Determine the
Style of Faulting
Purely tensional stresses associated with a _________
plate boundary will generate a _______ fault.
A. convergent; strike-slip
B. convergent; normal
C. divergent; reverse
D. divergent; normal
Tectonic Forces Determine the
Style of Faulting
What kind of fault is produced by purely compressional
stress?
A. left-lateral strike-slip fault
B. thrust fault
C. normal fault
D. right-lateral strike-slip fault
Tectonic Forces Determine the
Style of Faulting
What kind of fault is produced by purely compressional
stress?
A. left-lateral strike-slip fault
B. thrust fault
C. normal fault
D. right-lateral strike-slip fault
Tectonic Forces Determine the
Style of Faulting
Shear stress combined with compressional stress will
result in:
A. purely vertical motion
B. purely horizontal motion
C. oblique motion
D. all of these
E. none of these
Tectonic Forces Determine the
Style of Faulting
Shear stress combined with compressional stress will
result in:
A. purely vertical motion
B. purely horizontal motion
C. oblique motion
D. all of these
E. none of these
Tectonic Forces Determine the
Style of Faulting
When considering the effects of faulting on the
lithosphere, it is clear that normal faults serve to
effectively:
A. shorten and thicken the crust
B. thin and shorten the crust
C. thin and extend the crust
D. shorten and thin the crust
Tectonic Forces Determine the
Style of Faulting
When considering the effects of faulting on the
lithosphere, it is clear that normal faults serve to
effectively:
A. shorten and thicken the crust
B. thin and shorten the crust
C. thin and extend the crust
D. shorten and thin the crust
Tectonic Forces Determine the
Style of Faulting
Most faults in nature have an oblique component
because:
A. tectonic stresses are typically purely vertical
B. tectonic stresses are typically purely horizontal
C. horizontal motion is more easily accommodated than
vertical motion
D. differential tectonic stresses have both vertical and
horizontal components
Tectonic Forces Determine the
Style of Faulting
Most faults in nature have an oblique component
because:
A. tectonic stresses are typically purely vertical
B. tectonic stresses are typically purely horizontal
C. horizontal motion is more easily accommodated than
vertical motion
D. differential tectonic stresses have both
vertical and horizontal components