Chapter 2
Distinctive rock sequences such as Archean crust and Proterozoic mountain belts in South America terminate at the Atlantic Ocean but reappear on the continent of a. Africa. b. Europe. c. North America. d. Australia.
a. Africa.
Which of the following is true of continental lithosphere compared to oceanic lithosphere? a. Continental lithosphere is thicker than oceanic lithosphere. b. Continental lithosphere contains more mafic rocks than oceanic lithosphere. c. Continental lithosphere is denser than oceanic lithosphere. d. Continental lithosphere and oceanic lithosphere have similar compositions, densities, and thicknesses.
a. Continental lithosphere is thicker than oceanic lithosphere.
The lithosphere is the rigid part of the mantle, while the asthenosphere is the relatively more fluid portion. The following figure shows the spatial relationship between the Earth's crust, lithosphere, and asthenosphere. Which of the following statements regarding the figure is FALSE? a. Continental lithosphere is thinner than oceanic lithosphere. b. The asthenosphere is denser than the lithosphere. c. Oceanic crust is thinner than continental crust. d. Continental lithosphere sinks deeper into the asthenosphere than oceanic lithosphere.
a. Continental lithosphere is thinner than oceanic lithosphere. FEEDBACK: Continental lithosphere is much thicker than oceanic lithosphere. As a result of the extra mass, the continental lithosphere settles deeper into the relatively softer asthenosphere, much like a heavily loaded boat will settle deeper into the sea.
Paleoenvironmental reconstructions of Pangea indicate that regional climates during the Paleozoic were significantly different than they are today. Looking at the following figure, which statement about climate and associated rock deposits from the Paleozoic is FALSE? a. Desert sands were deposited in South America. b. Coal swamps were present along the east coast of the United States. c. India was partially glaciated. d. Coral reefs were found in North America, Europe, and Asia.
a. Desert sands were deposited in South America.
In the following figure, the magnetic anomaly pattern is mirrored on either side of the central ridge. What is responsible for this pattern? a. Seafloor spreading builds new crust equally on both sides of the ridge. b. The magnetic anomalies follow a repetitious pattern in mantle convection. c. The anomalies follow El Niño /La Niña cycles d. The anomalies follow Milenkovich cycles based on orbital dynamics.
a. Seafloor spreading builds new crust equally on both sides of the ridge. FEEDBACK: This image is of a mid-ocean ridge. These are divergent-plate boundaries, meaning that new material is created at the ridge. As the material spreads away from the central ridge, any changes in the Earth's magnetic field will be mirrored almost exactly.
Much of the ocean floor in all major oceans consists of broad, flat regions called a. abyssal plains. b. continental rises. c. fracture zones. d. seamounts.
a. abyssal plains.
The angle on the globe or on a map between the direction a compass needle points and a line of longitude is called a. declination. d. inclination. c. subduction. d. striation.
a. declination.
At the subduction zone where the Pacific Plate is subducting under the islands of Japan, the Wadati-Benioff zone of deep earthquakes a. extends from the trench westward underneath Japan. b. extends from the trench eastward underneath the Pacific Plate. c. is confined to the trench. c. is absent because there are no earthquakes at subduction zones.
a. extends from the trench westward underneath Japan.
The idea that the continents had once fit together as a single supercontinent called Pangaea was rejected when first proposed because a. geologists did not know of a force great enough to move continents. b. the continents did not fit together tightly enough. c. the fossil evidence was inconclusive. d. the distribution of climatic belts did not make sense in that configuration.
a. geologists did not know of a force great enough to move continents.
With increasing distance from a mid-ocean ridge, the age of oceanic crust a. increases. b. decreases. c. stays constant. d. varies randomly.
a. increases.
Marine magnetic anomaly belts run parallel to a. mid-ocean ridges. b. fracture zones. c. continental coastlines. d. continental shelves.
a. mid-ocean ridges.
According to the theory of plate tectonics, plates are a. pieces of lithosphere that move over the surface of the Earth with respect to one another. b. layers of lithosphere that are stacked one atop the other from the surface to the outer core. c. pieces of continental rocks that move through the weaker oceanic rocks. d. very thick (approximately one-quarter of the Earth's radius).
a. pieces of lithosphere that move over the surface of the Earth with respect to one another.
The discovery that each continent had different and separate apparent polar-wander paths, such as those in the figure below, proved that a. the continents move independently of each other relative to fixed magnetic poles. b. the magnetic poles move but the relative positions of continents to each other remain constant. c. both the poles and continents move, but only one at a time. d. both the poles and continents move, and do so together.
a. the continents move independently of each other relative to fixed magnetic poles.
Multiple types of plate boundaries can often be found in close proximity to one another. Below is an image of the Juan de Fuca plate subducting beneath Washington and Oregon in the American Northwest. Match the type of plate boundary with the correct letter on the image a. A - Convergent, B - Divergent, C - Transform b. A - Divergent, B - Transform, C - Convergent c. A - Transform, B - Divergent, C - Convergent d. A - Transform, B - Convergent, C - Divergent
b. A - Divergent, B - Transform, C - Convergent
Which of the following is true of the lithosphere? a. It is the same thing as the crust. b. It is composed of the crust and the uppermost rigid part of the mantle. c. It is a very ductile layer in the upper part of the mantle. d. It is the layer of the mantle directly below the asthenosphere.
b. It is composed of the crust and the uppermost rigid part of the mantle.
The following figures show what happens when two continents collide. In the upper figure, oceanic crust is being subducted until the continents collide. The bottom figure shows the collision. What happens to the subducting plate when continents collide? a. The subducting plate is uplifted into a volcanic-island arc. b. The subducting plate becomes detached and the convergent boundary sutures become closed, leaving a single plate. c. The subducting plate creates a transform-plate boundary. d. The subducting plate creates a backarc basin.
b. The subducting plate becomes detached and the convergent boundary sutures become closed, leaving a single plate FEEDBACK: Continent-to-continent collisions lead to extensive mountain building and the eventual end of the convergent boundary as two plates fuse into one. This result occurs because continental crust is too buoyant to be subducted.
The constant motion of tectonic plates leads to convergent, divergent, and transform-plate boundaries. Which type of structure is shown in the figure below? a. a subduction zone b. a mid-ocean ridge c. a passive margin d. a strike-slip faul
b. a mid-ocean ridge FEEDBACK: The image shows where two plates are being pulled apart, leading to volcanic activity and faulting. This is a submarine divergent-plate boundary.
Seafloor spreading is driven by volcanic activity a. in the middle of abyssal plains. b. along mid-ocean ridges. c. at the edges of continental shelves. d. along fracture zones.
b. along mid-ocean ridges.
Beneath a blanket of sediments, oceanic crust is primarily composed of a. granite. b. basalt. c. limestone. d. coal.
b. basalt.
Continental lithosphere does not subduct because it is too a. thick. b. buoyant. c. young. d. warm.
b. buoyant.
Slab pull occurs because subducting slabs are _________, and therefore are _________ dense than the surrounding asthenosphere. a. hotter; less b. cooler; more c. hotter; more d. cooler; less
b. cooler; more
Which basic type of plate boundary is shown in the image below? a. convergent b. divergent c. transform d. submerged
b. divergent
The distribution of _________ around the globe provides the primary indicator of the boundaries between lithospheric plates. a. basalt b. earthquakes c. mountains d. ocean basins
b. earthquakes
At a subduction zone, the downgoing (subducting) plate a. is always composed of continental lithosphere. b. is always composed of oceanic lithosphere. c. may be composed of either oceanic or continental lithosphere. d. is composed entirely of asthenosphere.
b. is always composed of oceanic lithosphere.
Continental coastlines that occur within the interior of a lithospheric plate are called ___________ margins. a. internal b. passive c. active d. inert
b. passive
Which of these is a result of plate tectonics? a. glaciation b. seafloor spreading c. extinction d. convection in the outer core
b. seafloor spreading
The map below depicts the locations of earthquakes in the ocean basins. Which of the following locations is most likely to be located along a plate boundary? a. the interiors of continents, where there are few or no earthquakes b. the middle of the north Atlantic Ocean, where there is a north-south belt of earthquakes c. the southwest Atlantic Ocean, far away from any earthquakes d. None of these are likely locations for plate boundaries.
b. the middle of the north Atlantic Ocean, where there is a north-south belt of earthquakes
This figure shows the mid-Atlantic ridge, south of Iceland. The arrows show the orientation of Earth's magnetic field as it has reversed several times over the last 180 Million Years. What information can be determined based on the width of the different anomaly rock units? a. the severity of the magnetic anomaly b. the relative duration of the anomaly c. the rate of crustal uplift d. the depth of the ocean at the time the anomaly was created
b. the relative duration of the anomaly FEEDBACK: Because new crust is being formed at the mid-ocean ridge at a fairly constant rate, we can surmise that wider anomaly units represent longer durations of time.
Mid-ocean ridges are a. associated with continental hot spots. b. underwater volcanic mountain ranges. c. topographic low points on the ocean floor. d. difficult to discern from the abyssal plains.
b. underwater volcanic mountain ranges.
Lithospheric plates move relative to other along plate boundaries at velocities between ___________ a. 1 and 15 meters per year b. 50 and 80 centimeters per year c. 1 and 20 centimeters per year d. 0.1 and 0.8 centimeters per year
c. 1 and 20 centimeters per year
During the past 5 million years, approximately how long have chrons lasted before the next major magnetic polarity reversal? a. 10 to 20 years. b. 500 to 1000 years. c. 700,000 to 1.5 million years d. There has not been a magnetic polarity reversal during the past five million years.
c. 700,000 to 1.5 million years
Through plate tectonics, plates move about the Earth, slamming into, pulling away from, and sliding past one another. Match the images from the figure below with the appropriate boundary name. a. A - Convergent, B - Divergent, C - Transform b. A - Transform, B - Convergent, C - Divergent c. A - Divergent, B - Convergent, C - Transform d. A - Divergent, B - Transform, C - Convergent
c. A - Divergent, B - Convergent, C - Transform FEEDBACK: Divergent boundaries are found at ocean ridges and continental-rift zones. Convergent boundaries occur where plates collide. Subduction and mountain building commonly result. Transform boundaries occur where plates slide past one another, such as at the San Andreas Fault in California.
_________ proposed the continental-drift hypothesis, suggesting that the arrangement of continents on the planet has changed over geologic time. a. Harry Hess b. Robert Dietz c. Alfred Wegener d. Harry Hess and Robert Dietz
c. Alfred Wegener
Which is likely to slowly flow when subjected to a geologic force? a. continental lithosphere b. oceanic lithosphere c. asthenosphere d. Neither the lithosphere nor asthenosphere flows when subjected to stress.
c. asthenosphere
The majority of new oceanic crust is created a. at subduction zones. b. along fracture zones. c. at mid-ocean ridges. d. by hot spot volcanism.
c. at mid-ocean ridges.
Most of the pulling force driving plate motion is produced a. at mid-ocean ridges. b. at collision zones. c. at subduction zones. d. in the interiors of continental plates.
c. at subduction zones.
The rock produced at mid-ocean ridges consists of c. entirely basalt. b. entirely gabbro. c. basalt at shallow depths and gabbro at deeper depths. d. gabbro at shallow depths and basalt at deeper depths.
c. basalt at shallow depths and gabbro at deeper depths.
A ________ is a linear feature in continental lithosphere where a plate is pulled apart, resulting in a deep valley, extensive faulting and volcanism, and if sustained, division into two plates separated by new oceanic lithosphere. a. forearc basin b. volcanic island arc c. continental rift d. mid-ocean ridge
c. continental rift
Subduction zones are found at _________ plate boundaries. a. divergent b. transvergent c. convergent d. transform
c. convergent
Hot spots are caused by a. friction due to the lithosphere sliding atop the asthenosphere. b. unusually dense concentrations of radioactive isotopes at various points in the crust. c. hot plumes of mantle material that rise up through cooler, denser surrounding rock. d. zones of localized subduction that produce melting of the mantle.
c. hot plumes of mantle material that rise up through cooler, denser surrounding rock.
Marine magnetic anomalies in oceanic crust result from seafloor spreading in conjunction with a. global warming. b. magnetic storms on the surface of the Sun. c. magnetic polarity reversals. d. apparent wander of the magnetic poles.
c. magnetic polarity reversals.
Oceanic lithosphere thickens as it moves away from mid-ocean ridges primarily because of a. the addition of new crust due to hot-spot volcanism. b. the addition of new crust due to sedimentation. c. the addition of new lithospheric mantle as a result of cooling. d. reasons that geologists cannot determine at present.
c. the addition of new lithospheric mantle as a result of cooling.
Deep-sea trenches are likely to be located near a. fracture zones. b. mid-ocean ridges. c. volcanic arcs. d. seamounts.
c. volcanic arcs.
The distribution of various geological features can be used to recreate what the world looked like millions of years ago. This figure shows the location and direction of glacial striations, which are indicators of the direction of glacial movement. Based on this information, where was the pole located? a. Antarctica b. North America c. Australia d. Southern Africa
d. Southern Africa FEEDBACK: The continents of South America, Antarctica, Africa, and Australia can be reconstructed to form the polar region of Earth from 260-280 Mya. The glacial striations radiate away from southeastern Africa, suggesting it was the pole.
Which of the following best describes the distribution of earthquakes around the globe? a. They tend to occur randomly on the continents. b. They tend to occur randomly in the ocean basins. c. They tend to occur randomly both on the continents and in the ocean basins. d. They occur in distinct zones.
d. They occur in distinct zones.
During subduction, one tectonic plate is forced beneath another. In this image, an oceanic plate is subducting under another oceanic plate. What geologic feature is being created in the image? a. a forearc basin b. a backarc basin c. a mid-ocean ridge d. a volcanic island arc
d. a volcanic island arc
Large, thick-crusted, nonvolcanic mountain belts, like the Himalayas, are associated with a. mid-ocean ridges. b. subduction zones. c. hot spots. d. continent-continent collisions.
d. continent-continent collisions.
Transform plate boundaries are unlike other plate boundaries because a. all movement of plates along transform boundaries is vertical. b. they are always very short in length. c. they do not penetrate into the lithosphere. d. old plate is not consumed nor is new plate created.
d. old plate is not consumed nor is new plate created.
The apparent tendency of the north and south magnetic poles to vary in position over time is termed a. dipole. b. declination. c. inclination. d. polar wander.
d. polar wander.
