Earth: An Introduction to Physical Geology, 11e (Tarbuck)
Chapter 2 Plate Tectonics: A Scientific Revolution Unfolds
2.1 Multiple-Choice Questions
1) Which scientist developed the idea of Continental Drift?
A) Isaac Newton
B) Charles Darwin
C) Albert Einstein
D) Alfred Wegener
2) Which war was indirectly responsible for the development of the more modern tools that
made the theory of Plate Tectonics possible?
A) World War I
B) World War II
C) Korean War
D) Vietnam War
3) What is the name of the supercontinent proposed by Alfred Wegener?
A) Pangaea
B) Rodinia
C) Amasia
D) Nuna
4) Although the jigsaw-puzzle fit of the southern continents was noted, opponents of Continental
Drift argued that, even if continental displacement had occurred, a good fit between the
continents today would be unlikely. What geological evidence did they cite to support this
claim?
A) Deposition in river deltas had changed the longshore current, resulting in erosion
B) The tensional stress of splitting sheared the continents beyond all repair
C) Wave erosion and coastal deposition have changed the shape of the continents
D) Fissure eruptions along continental margins had created new land
5) Even before the proposal of Continental Drift, paleontologists recognized that some sort of
land connection was needed to account for the identical fossil organisms found on multiple
continents. Which of the following was not one of their hypotheses?
A) Glacial forebulges raising the land surface
B) A chain of island stepping stones
C) Floating debris used as rafts
D) A transoceanic land bridge
6) When the continents were assembled and mountain ranges were matched up, mountains in
Scandinavia and the British Isles matched up perfectly with which North American mountain
range?
A) Rocky Mountains
B) Appalachian Mountains
C) Sierra Nevada Mountains
D) Olympic Mountains
7) When considering evidence of glaciation on the southern continents, why did Wegener reject
the explanation that the entire planet had experienced a period of extreme cooling?
A) Because the glacial debris was localized to a few small mountain valleys
B) Because he knew the “glacial debris” was actually a misinterpreted landslide
C) Because geologic evidence supported the existence of tropical swamps in the Northern
Hemisphere
D) Because the 16O/18O ratios in fossils supported an ice-free period
8) In which decade was the Theory of Plate Tectonics developed?
A) 1940s
B) 1960s
C) 1970s
D) 1990s
9) In the mid-20th century, researchers dredging the seafloor could not find any materials older
than ________.
A) 6,000 years
B) 1.2 million years
C) 180 million years
D) 1.5 billion years
10) Which of the following is not one of the major tectonic plates on the Earth’s surface?
A) Juan de Fuca Plate
B) North American Plate
C) African Plate
D) Pacific Plate
11) The lithosphere is composed of material from the ________ and the rigid part of the
________.
A) Outer Core; Inner Core
B) Mantle; Outer Core
C) Crust; Lower Mantle
D) Crust; Upper Mantle
12) Which plate boundary accounts for the smallest percentage of all plate boundaries on the
surface of the Earth?
A) Convergent Boundaries
B) Divergent Boundaries
C) Transform Boundaries
13) Continental crust is mainly composed of ________ whereas oceanic crust is mainly
composed of ________.
A) Olivine; Basalt
B) Limestone; Gabbro
C) Granite; Basalt
D) Gabbro; Granite
14) Why are the mid-ocean ridges higher in elevation than the surrounding ocean floor?
A) Due to the high volume of magma issuing from the fissure
B) Warmer material near the ridge is less dense, so floats higher on the mantle
C) The collision of the tectonic plates is forcing material higher
D) Thermal springs developing in stress fractures are depositing large volumes of material,
increasing the height
15) A location where continental rifting is occurring today is ________.
A) San Andreas Fault
B) Mid-Continent Rift
C) Juan de Fuca Trench
D) East African Rift Valley
16) At a ________, one colliding plate will be forced beneath another because of differences in
density.
A) Subduction Zone
B) Continental Rift
C) Transform Boundary
D) Twilight Zone
17) How will the age and temperature of the subducting plate affect its angle of descent?
A) Older and cooler plates will have a shallow angle of descent
B) Older and warmer plates will have a steeper angle of descent
C) Younger and warmer plates will have a shallow angle of descent
D) Younger and colder plates will have a steeper angle of descent
18) A ________ is a geographic low marking the location where oceanic lithosphere descends
into the mantle.
A) Fold and Thrust Mountains
B) Deep-Ocean Trench
C) Benioff Zone
D) Mid-Ocean Rift
19) Which type of convergence will result in a continental volcanic arc?
A) Oceanic-Continental
B) Oceanic-Oceanic
C) Continental-Continental
20) Which type of convergence will result in a volcanic island arc?
A) Oceanic-Continental
B) Oceanic-Oceanic
C) Continental-Continental
21) Where are the majority of transform faults located?
A) Southern California
B) On the ocean floor offsetting segments of oceanic ridge
C) Radiating from convergent boundaries as stress fractures
D) Along mountain ranges that have been thrust up due to collision
22) What is a mantle plume?
A) The magma that rises up from the mantle at a divergent plate boundary
B) Material rising up from a subducting plate going through partial melting
C) A form of batholith composed of ferromagnesian materials
D) An upwelling of hot material from the Earth’s interior that is cylindrical in shape
23) ________ is when iron particles in lavas align their magnetic fields with magnetic north,
preserving a record of that pole’s location at that moment in time.
A) Mantle Plume
B) Paleomagnetism
C) Magnetic Reversal
D) Seafloor Spreading
24) A typical rate of seafloor spreading in the Atlantic Ocean is ________.
A) 2 meters per year
B) 0.1 inches per year
C) 20 feet per year
D) 2 centimeters per year
25) All of the following are evidence supporting the theory of plate tectonics except for
________.
A) Changes in the Moon’s orbit due to shifting plates
B) Ocean floor drilling
C) Hot spots
D) Measurements of plate motions
26) Where is the top of the asthenosphere is closest to Earth’s surface?
A) Along a mid-ocean ridge
B) Above a deep mantle hot spot
C) Along a transform fault
D) Along a subduction zone
27) Which of the following statements best describes the tectonic setting for Mount St. Helens
and the other Cascade volcanoes?
A) A chain of young, active volcanoes built on a continental margin above a sinking slab of
oceanic lithosphere
B) A chain of young, active, volcanoes built as western North America moved over a mantle
plume
C) Old, deeply eroded volcanoes built before the Pacific Ocean existed
D) Old, deeply eroded, basaltic volcanoes built when western North America was over the
present-day site of the Hawaiian hot spot
28) How did researchers in the mid-20th century obtain ocean floor samples in order to
determine the age of the seafloor?
A) Satellite imagine
B) Manned submersibles
C) Hydraulic vacuum tubes
D) Drilling ships
29) Samples from the seafloor around the Mid-Atlantic Ridge and the East Pacific Rise show
that both areas have been creating new material in the last five million years. Samples from the
East Pacific Rise show the five million year old seafloor is three times as wide as similarly aged
material from the Mid-Atlantic Ridge. What does this say about the rate of seafloor growth in the
East Pacific?
A) The seafloor at both sites is growing at the same rate
B) The seafloor at the East Pacific Rise is growing more slowly
C) The seafloor at the Mid-Atlantic is growing more quickly
D) The seafloor at the Mid-Atlantic is growing more slowly
30) What two pieces of information would researchers need to have in order to calculate the rate
of plate motion for seafloor spreading?
A) Age of the continent and depth of the water
B) Distance from the rift and age of seafloor sample
C) Age of the seafloor sample and age of the continent
D) Type of rock and distance from the rift
31) How can satellites and GPS receivers be used to monitor plate motion?
A) GPS receivers are placed on landmasses to track their locations
B) Satellites send lasers to measure the distance to continents
C) GPS receivers send signals to each other to see if the units are getting closer together
D) Satellites track seafloor spreading
32) How can the orientation of transform faults provide information about the direction of plate
motion?
A) Transform faults are oriented perpendicular to the direction of plate motion
B) Transform faults radiate out from the rift zone located in the center
C) Transform faults are parallel to the direction of plate motion
D) Transform faults are parallel to convergent boundaries
33) Which is denser: 100 million year-old oceanic lithosphere near a convergent boundary, 15
million year-old oceanic lithosphere near a rift, or the upper part of the asthenosphere?
A) 15 million year-old oceanic lithosphere
B) 100 million year-old oceanic lithosphere
C) Upper Asthenosphere
D) They all have the same density
34) What generates the heat necessary for convection in the Earth?
A) Volcanic Eruption
B) Friction between moving slabs
C) Chemical reactions between geologic materials and hydrothermal fluids
D) Decay of radioactive materials
35) ________ is when cold oceanic lithosphere are more dense than the underlying warm
lithosphere.
A) Slab Pull
B) Slab Push
C) Ridge Push
D) Mantle Drag
36) Along which tectonic boundary is ridge push going to be most important?
A) Convergent Boundary
B) Divergent Boundary
C) Transform Boundary
37) Which factor contributes the most toward plate motion?
A) Ridge Push
B) Mantle Drag
C) Slab Pull
D) Friction
38) In which layer of the Earth does the convection necessary for plate motion occur?
A) Crust
B) Mantle
C) Outer Core
D) Inner Core
39) Which model of convection describes how the interior is divided into several levels of
convection cells?
A) Layer Cake Model
B) Whole-Mantle Convection
C) Plume Model
D) Differentiation Model
40) In the Whole-Mantle Convection model, what feature balances the deeply descending
lithosphere by transporting hot material toward the surface?
A) Kimberlites
B) Decompression Melting
C) Mantle Plumes
D) Rift Zones
2.2 True/False Questions
1) Wegener was the first scientist to notice the jigsaw puzzle fit of the southern continents.
2) One explanation for the wide distribution of Glossopteris seeds is, because they were so small,
they could be globally distributed by the wind.
3) The interpretations and evidence used in Continental Drift were sound and did not need
modification in order to be used for the Theory of Plate Tectonics.
4) Oceanic Lithosphere is thickest along oceanic ridges because this is where the new
lithospheric material is forming.
5) The surface of the earth is broken up into seven plates.
6) The majority of divergent plate boundaries are associated with oceanic ridges.
7) The global ocean ridge system is the longest topographic feature on the Earth’s surface.
8) Oceanic lithosphere will get thicker the farther it gets from the mid-ocean ridge.
9) A convergent plate boundary is a destructive boundary.
10) Subduction zones will only develop between a continental plate and an oceanic plate.
11) An oceanic plate that has been permeated by water before subduction will melt at a lower
temperature than a “dry” oceanic plate.
12) Transform boundaries provide the means by which oceanic crust created at divergent
boundaries can be carried to the sites of destruction at convergent boundaries.
13) The magnetic poles roughly correspond to the locations of the geographic poles.
14) A transform boundary is usually not associated with volcanism.
15) A convergent boundary is usually associated with rift valleys and volcanic arcs.
16) The total size of tectonic plates does not change.
2.3 Short Answer Questions
1) Alfred Wegener provided several pieces of evidence supporting the idea that the planet’s
continents were once joined in a single landmass. List four of them.
2) Which two continents did Wegener cite as having the best evidence of a close fit?
3) The ________ is a hotter, weaker region in the mantle that lies below the lithosphere and
responds to forces by flowing.
4) Which is denser: Oceanic lithosphere or continental lithosphere?
5) Analyze and explain how the respective temperatures of the lithosphere and asthenosphere
affect those layers’ rigidities and responses when force is applied.
6) There is an expression in American society that it would only take one good earthquake and
the state of California would sink into the ocean. Using what you know about Plate Tectonics,
explain why this may or may not be possible.
7) ________ is the name of the process by which new seafloor is generated at mid-ocean ridges.