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UNDERSTANDING EARTH, SIXTH EDITION
GROTZINGER • JORDAN
GEOLOGY MEDIA SUITE
Chapter 2
Plate Tectonics
The Unifying Theory
© 2010 W.H. Freeman and Company
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
Key Figure 2.6 (pages 26-27)
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Divergent Boundaries
Oceanic Plate Separation
MidAtlantic
Ridge
an
c
i
r
e
m
A
th
r
o
e
N
P la t
E ur
asia
n
Pl a
te
Divergent Boundaries
Oceanic Plate Separation
Volcanoes and earthquakes concentrate.
an
c
i
r
e
m
A
th
r
o
e
N
P la t
MidAtlantic
Ridge
E ur
asia
n
Pl a
te
Divergent Boundaries
Continental Plate Separation
East African
Rift Valley
ate
l
P
an
c
i
r
f
A
Soma
l i S ub
plate
Divergent Boundaries
Continental Plate Separation
Parallel valleys; volcanoes and earthquakes.
East African
Rift Valley
ate
l
P
an
c
i
r
f
A
Soma
l i S ub
plate
Convergent Boundaries
Ocean-Ocean Convergence
Mariana Islands
e
n
i
p
ip
Phil
e
Plat
Marianas Trench
Pacif
ic Pla
te
Convergent Boundaries
Ocean-Ocean Convergence
Deep-sea trench; volcanic island arc.
Mariana Islands
e
n
i
p
ip
Phil
e
Plat
Marianas Trench
Pacif
ic Pla
te
Convergent Boundaries
Ocean-Continent Convergence
Andes
Mountains
Peru-Chile Trench
te
a
l
P
a
c
Naz
South
American
Plate
Convergent Boundaries
Ocean-Continent Convergence
A volcanic belt of
mountains forms.
Andes
Mountains
Peru-Chile Trench
te
a
l
P
a
c
Naz
South
American
Plate
Convergent Boundaries
Continent-Continent Convergence
Himalaya
te
a
l
P
n
a
i
l
a
r
st
Indian-Au
Tibetan
Plateau
Main
thrust
fault
Eurasian
Plate
Convergent Boundaries
Continent-Continent Convergence
Crust crumbles, creating high
mountains and a wide plateau.
Himalaya
te
a
l
P
n
a
i
l
a
r
st
Indian-Au
Tibetan
Plateau
Main
thrust
fault
Eurasian
Plate
Transform-Fault Boundaries
Mid-Ocean Ridge Transform Fault
Euras
ian Pl
ate
late
P
n
a
c
i
er
m
A
h
t
r
No
Transform-Fault Boundaries
Mid-Ocean Ridge Transform Fault
Spreading centers offset.
Euras
ian Pl
ate
late
P
n
a
c
i
er
m
A
h
t
r
No
Transform-Fault Boundaries
Continental Transform Fault
ate
l
P
c
i
f
Paci
North
Ameri
can Pl
ate
Transform-Fault Boundaries
Continental Transform Fault
Offset continental crust.
ate
l
P
c
i
f
Paci
North
Ameri
can Pl
ate
The San Andreas fault
Figure 2.9 (page 30)
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As plates
move past
each other...
As plates
move past
each other...
…creek beds
are offset
As plates
move past
each other...
n
Sa
A
nd
re
…creek beds
are offset
San
Francisco
as
fau
Los Angeles
lt
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
Which of the locations listed below is least associated
with a volcanically active plate boundary?
A. Mid-ocean ridge
B. Deep ocean trench
C. Transform fault
D. Continental Rift
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
Which of the locations listed below is least associated
with a volcanically active plate boundary?
A. Mid-ocean ridge
B. Deep ocean trench
C. Transform fault
D. Continental Rift
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
Which kind of plate boundary is associated with
Earthquake activity?
A. Divergent Boundary
B. Convergent Boundary
C. Transform-fault Boundary
D. All of the above
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
Which kind of plate boundary is associated with
Earthquake activity?
A. Divergent Boundary
B. Convergent Boundary
C. Transform-fault Boundary
D. All of the above
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
At which kind of plate boundary is new oceanic
lithosphere formed?
A. Oceanic transform boundary
B. Oceanic divergent boundary
C. Ocean-ocean convergent boundary
D. Ocean-continent convergent boundary
Interactions at plate boundaries depend
on the direction of relative plate motion
and the type of crust.
At which kind of plate boundary is new oceanic
lithosphere formed?
A. Oceanic transform boundary
B. Oceanic divergent boundary
C. Ocean-ocean convergent boundary
D. Ocean-continent convergent boundary
Continental rifting, drifting, and
collisions assembled and
dispersed Pangaea
Key Figure 2.13 (pages 38–39)
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ASSEMBLY OF PANGAEA
RODINIA Late Proterozoic, 750 Ma
ASSEMBLY OF PANGAEA
RODINIA Late Proterozoic, 750 Ma
Formed about 1.1 billion
years ago; began to break
up about 750 million
years ago.
ASSEMBLY OF PANGAEA
Late Proterozoic, 650 Ma
ASSEMBLY OF PANGAEA
Late Proterozoic, 650 Ma
The pre-Pangean pattern
of continental drift.
ASSEMBLY OF PANGAEA
Middle Ordovician, 458 Ma
The pre-Pangean pattern
of continental drift.
ASSEMBLY OF PANGAEA
Early Devonian, 390 Ma
The pre-Pangean pattern
of continental drift.
ASSEMBLY OF PANGAEA
PANGAEA (a) Early Triassic, 237 Ma
ASSEMBLY OF PANGAEA
PANGAEA (a) Early Triassic, 237 Ma
Assembled by 237 Ma.
BREAKUP OF PANGAEA
(b) Early Jurassic, 195 Ma
BREAKUP OF PANGAEA
(b) Early Jurassic, 195 Ma
Signaled by the opening
of rifts from which lava
poured; relics can be
found today in volcanic
rocks from Nova Scotia
to North Carolina.
BREAKUP OF PANGAEA
(c) Late Jurassic, 152 Ma
BREAKUP OF PANGAEA
(d) Late Cretaceous, Early Tertiary, 66 Ma
THE PRESENT-DAY AND FUTURE WORLD
(e) PRESENT-DAY WORLD
THE PRESENT-DAY AND FUTURE WORLD
(e) PRESENT-DAY WORLD
The modern world has
been produced over the
past 65 million years.
THE PRESENT-DAY AND FUTURE WORLD
(f) 50 million years in the future
Continental rifting, drifting, and
collisions assembled and
dispersed Pangaea
According to the reconstructed history of continental
movements you just saw, about when did the modernday Atlantic Ocean first begin to form?
A. About 750 million years ago
B. About 390 million years ago
C. About 150 million years ago
D. About 50 million years ago
Continental rifting, drifting, and
collisions assembled and
dispersed Pangaea
According to the reconstructed history of continental
movements you just saw, about when did the modernday Atlantic Ocean first begin to form?
A. About 750 million years ago
B. About 390 million years ago
C. About 150 million years ago
D. About 50 million years ago
Two competing hypotheses for the
mantle convection system.
Figure 2.14 (page 40)
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Whole-mantle convection
Mantle
Outer core
Inner core
Upper
mantle
700 km
Lower
mantle
2900 km
Outer core
Whole-mantle convection
Upper
mantle
700 km
Lower
mantle
2900 km
Outer core
Stratified convection
Boundary near
700 km separates
the two convection
systems.
Two competing hypotheses for the
mantle convection system.
Considering either the whole mantle or stratified mantle
convection models, at which kind of plate tectonic
boundary is the upper part of the mantle
(asthenosphere) rising?
A. Divergent boundaries
B. Convergent boundaries
C. Transform boundaries
Two competing hypotheses for the
mantle convection system.
Considering either the whole mantle or stratified mantle
convection models, at which kind of plate tectonic
boundary is the upper part of the mantle
(asthenosphere) rising?
A. Divergent boundaries
B. Convergent boundaries
C. Transform boundaries
Two competing hypotheses for the
mantle convection system.
Although the exact nature of mantle convection is still a
matter of debate, which model for mantle convection is
currently favored by most geoscientists?
A. Whole-mantle convection
B. Stratified-mantle convection
Two competing hypotheses for the
mantle convection system.
Although the exact nature of mantle convection is still a
matter of debate, which model for mantle convection is
currently favored by most geoscientists?
A. Whole-mantle convection
B. Stratified-mantle convection
Two competing hypotheses for the
mantle convection system.
Which is the underlying fundamental driving force for
mantle convection?
A. Magnetism
B. Nuclear fusion
C. Earth’s rotation
D. Gravity
Two competing hypotheses for the
mantle convection system.
Which is the underlying fundamental driving force for
mantle convection?
A. Magnetism
B. Nuclear fusion
C. Earth’s rotation
D. Gravity
Seafloor Spreading
Evidence for magnetic reversals has been primarily
preserved in:
A. metamorphic rocks near convergent plate boundaries
B. limestone and shale accumulating in shallow ocean
basins
C. active dune fields in the arid regions of the world
D. extrusive igneous rocks associated with mid-ocean ridges
Seafloor Spreading
Evidence for magnetic reversals has been primarily
preserved in:
A. metamorphic rocks near convergent plate boundaries
B. limestone and shale accumulating in shallow ocean
basins
C. active dune fields in the arid regions of the world
D. extrusive igneous rocks associated with midocean ridges
Seafloor Spreading
The idea that igneous rocks can record magnetic
anomalies was first observed in:
A. pillow basalts near the mid-Atlantic ridge
B. basaltic lava flows from successive volcanic eruptions
C. welded ash and cinders accumulated after an explosive
volcanic eruption
D. granitic rocks that have been contact metamorphosed
Seafloor Spreading
The idea that igneous rocks can record magnetic
anomalies was first observed in:
A. pillow basalts near the mid-Atlantic ridge
B. basaltic lava flows from successive volcanic
eruptions
C. welded ash and cinders accumulated after an explosive
volcanic eruption
D. granitic rocks that have been contact metamorphosed
Seafloor Spreading
Which of the following magnetic reversals are we
currently experiencing?
A. Gilbert
B. Matuyama
C. Brunhes
D. Gauss
Seafloor Spreading
Which of the following magnetic reversals are we
currently experiencing?
A. Gilbert
B. Matuyama
C. Brunhes
D. Gauss
Seafloor Spreading
Absolute ages obtained from igneous rocks samples
recovered from mid-ocean ridges reveal that:
A. rocks ages get older with greater distance from the axis of
the spreading ridge
B. the pattern of rock ages is mirrored on each side of the
spreading ridge
C. the duration of each magnetic interval is the same across
the axis of the spreading ridge
D. all of these
E. None of these
Seafloor Spreading
Absolute ages obtained from igneous rocks samples
recovered from mid-ocean ridges reveal that:
A. rocks ages get older with greater distance from the axis of
the spreading ridge
B. the pattern of rock ages is mirrored on each side of the
spreading ridge
C. the duration of each magnetic interval is the same across
the axis of the spreading ridge
D. all of these
E. None of these
Seafloor Spreading
Which of the following components within an igneous
rock are most responsive to the direction of the Earth’s
magnetic field?
A. quartz
B. feldspar
C. iron
D. magnesium
Seafloor Spreading
Which of the following components within an igneous
rock are most responsive to the direction of the Earth’s
magnetic field?
A. quartz
B. feldspar
C. iron
D. magnesium
Transform Boundary
Based on the relative motion of the North American and
Pacific Plates, the San Andreas Fault is an example of a
(an):
A. normal fault
B. reverse fault
C. left-lateral strike-slip fault
D. right-lateral strike-slip fault
Transform Boundary
Based on the relative motion of the North American and
Pacific Plates, the San Andreas Fault is an example of a
(an):
A. normal fault
B. reverse fault
C. left-lateral strike-slip fault
D. right-lateral strike-slip fault
Transform Boundary
At the present rate motion along the San Andreas Fault,
the city of Los Angeles will be a suburb of the city of San
Francisco in:
A. 9 years
B. 9 million years
C. 40,000 years
D. 2 million years
Transform Boundary
At the present rate motion along the San Andreas Fault,
the city of Los Angeles will be a suburb of the city of San
Francisco in:
A. 9 years
B. 9 million years
C. 40,000 years
D. 2 million years
Transform Boundary
Transform boundaries form as a result of ________
stresses in the lithosphere.
A. tensional
B. compressional
C. shear
D. random
Transform Boundary
Transform boundaries form as a result of ________
stresses in the lithosphere.
A. tensional
B. compressional
C. shear
D. random
Transform Boundary
The San Andreas Fault System is composed of:
A. a network of parallel transform faults
B. a single fault
C. a network of perpendicular transform faults
D. a zone of both normal and reverse faults
Transform Boundary
The San Andreas Fault System is composed of:
A. a network of parallel transform faults
B. a single fault
C. a network of perpendicular transform faults
D. a zone of both normal and reverse faults
Transform Boundary
Unlike both convergent and divergent plate boundaries,
transform plate boundaries do NOT involve:
A. the relative motion between two fault blocks
B. the buildup of tectonic stresses
C. the creation or destruction of crust
D. the generation of earthquakes in response to the release
of elastic strain
Transform Boundary
Unlike both convergent and divergent plate boundaries,
transform plate boundaries do NOT involve:
A. the relative motion between two fault blocks
B. the buildup of tectonic stresses
C. the creation or destruction of crust
D. the generation of earthquakes in response to the release
of elastic strain
Plate Tectonics: Subduction
Subduction is a tectonic process that happens at which
type of plate boundary?
A. convergent
B. divergent
C. transverse
D. hot spot
Plate Tectonics: Subduction
Subduction is a tectonic process that happens at which
type of plate boundary?
A. convergent
B. divergent
C. transverse
D. hot spot
Plate Tectonics: Subduction
What causes oceanic crust to subduct when it is
confronted by another oncoming plate?
A. temperature
B. strain
C. density
D. elasticity
Plate Tectonics: Subduction
What causes oceanic crust to subduct when it is
confronted by another oncoming plate?
A. temperature
B. strain
C. density
D. elasticity
Plate Tectonics: Subduction
Which of the following statements are TRUE?
A. All convergent plate boundaries are subduction zones.
B. All subduction zones involve the interaction of oceanic and
continental crust.
C. All subduction zones occur at convergent plate
boundaries.
D. All convergent plate boundaries involve the process of
rifting.
Plate Tectonics: Subduction
Which of the following statements are TRUE?
A. All convergent plate boundaries are subduction zones.
B. All subduction zones involve the interaction of oceanic and
continental crust.
C. All subduction zones occur at convergent
plate boundaries.
D. All convergent plate boundaries involve the process of
rifting.
Plate Tectonics: Subduction
What factors cause the downgoing plate to melt during
the process of subduction?
A. pressure and gravity
B. gravity and elasticity
C. seismicity and pressure
D. depth and frictional heating
Plate Tectonics: Subduction
What factors cause the downgoing plate to melt during
the process of subduction?
A. pressure and gravity
B. gravity and elasticity
C. seismicity and pressure
D. depth and frictional heating
Plate Tectonics: Subduction
Where would we go to see the closest convergent plate
boundary in North America?
A. to the island of Hawaii
B. off the coast of Washington State
C. to central New Mexico
D. all of these
E. none of these
Plate Tectonics: Subduction
Where would we go to see the closest convergent plate
boundary in North America?
A. to the island of Hawaii
B. off the coast of Washington State
C. to central New Mexico
D. all of these
E. none of these
Divergent Boundaries
The Red Sea is the surface expression of a Continental
Rift, or divergent boundary between which two plates?
A. Pacific and Indian Plates
B. North American and Pacific Plates
C. African and North American Plates
D. Arabian and African Plates
Divergent Boundaries
The Red Sea is the surface expression of a Continental
Rift, or divergent boundary between which two plates?
A. Pacific and Indian Plates
B. North American and Pacific Plates
C. African and North American Plates
D. Arabian and African Plates
Divergent Boundaries
A divergent plate boundary like the East African Rift is a
result of ________ stresses within the crust.
A. compressional
B. tensional
C. shear
D. none of these
Divergent Boundaries
A divergent plate boundary like the East African Rift is a
result of ________ stresses within the crust.
A. compressional
B. tensional
C. shear
D. none of these
Divergent Boundaries
Which of the following statements are TRUE?
A. All divergent plate boundaries are mid-ocean ridges.
B. All continental rift boundaries will become mid-ocean
ridges (tricky).
C. All mid-ocean ridges boundaries began as continental
rifts.
D. All divergent plate boundaries involve the process of
subduction.
Divergent Boundaries
Which of the following statements are TRUE?
A. All divergent plate boundaries are mid-ocean ridges.
B. All continental rift boundaries will become mid-ocean
ridges (tricky).
C. All mid-ocean ridges boundaries began as
continental rifts.
D. All divergent plate boundaries involve the process of
subduction.
Divergent Boundaries
Why is molten magma rising to the surface at
divergent plate boundaries?
A. because it is more dense than the hotter rock around it
B. because it is affected by anti-gravity
C. because it is less dense than the cooler rock surrounding
it
D. it is pure chance that magma rises at these boundaries
Divergent Boundaries
Why is molten magma rising to the surface at
divergent plate boundaries?
A. because it is more dense than the hotter rock around it
B. because it is affected by anti-gravity
C. because it is less dense than the cooler rock
surrounding it
D. it is pure chance that magma rises at these boundaries
Divergent Boundaries
Where would we go to see the closest divergent plate
boundary in North America?
A. off the coast of Washington State
B. to central New Mexico
C. to the island of Hawaii
D. all of these
E. none of these
Divergent Boundaries
Where would we go to see the closest divergent plate
boundary in North America?
A. off the coast of Washington State
B. to central New Mexico
C. to the island of Hawaii
D. all of these
E. none of these
Assembly and Breakup of Pangaea
Which continental landmass was assembled first?
A. Pangea
B. Australia
C. Gondwana
D. Rodinia
Assembly and Breakup of Pangaea
Which continental landmass was assembled first?
A. Pangea
B. Australia
C. Gondwana
D. Rodinia
Assembly and Breakup of Pangaea
How long did it take to form the modern continental
arrangement since the breakup of Pangaea?
A. 750 Ma
B. 200 Ma
C. 500 Ma
D. 50 Ma
Assembly and Breakup of Pangaea
How long did it take to form the modern continental
arrangement since the breakup of Pangaea?
A. 750 Ma
B. 200 Ma
C. 500 Ma
D. 50 Ma
Assembly and Breakup of Pangaea
Based on the present directions of plate motions, which
of the following should occur over the next 50 million
years?
A. North America will separate from South America.
B. Australia will collide with Antarctica.
C. Africa will collide with Eurasia.
D. The Atlantic Ocean Basin will close.
Assembly and Breakup of Pangaea
Based on the present directions of plate motions, which
of the following should occur over the next 50 million
years?
A. North America will separate from South America.
B. Australia will collide with Antarctica.
C. Africa will collide with Eurasia.
D. The Atlantic Ocean Basin will close.
Assembly and Breakup of Pangaea
The bolide impact that is hypothesized to have led to the
extinction of the dinosaurs impacted the Earth’s surface
__________ about __________ years ago.
A. in the Australian Outback; 200 million
B. in Northern Siberia; 25 million
C. off the Yucatan Peninsula; 65 million
D. near the North Pole; 5 million
Assembly and Breakup of Pangaea
The bolide impact that is hypothesized to have led to the
extinction of the dinosaurs impacted the Earth’s surface
__________ about __________ years ago.
A. in the Australian Outback; 200 million
B. in Northern Siberia; 25 million
C. off the Yucatan Peninsula; 65 million
D. near the North Pole; 5 million
Assembly and Breakup of Pangaea
Which of the following ocean basins are no longer
present due to plate motions over the past 750 Ma?
A. Rheic Ocean
B. Iapetus Ocean
C. Tethys Ocean
D. all of these
E. none of these
Assembly and Breakup of Pangaea
Which of the following ocean basins are no longer
present due to plate motions over the past 750 Ma?
A. Rheic Ocean
B. Iapetus Ocean
C. Tethys Ocean
D. all of these
E. none of these