Deck 2: The Way the Earth Works: Plate Tectonics

Question 1

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.
B) inclination.
C) subduction.
D) striation.

Answer 1

A

Question 2

Limestone reefs and salt deposits are important in the reconstruction of the Earth's history because they

A) can be used to infer the ancient climate of the Earth; they are deposited in environments that are restricted to warm climates.
B) automatically provide age information; all such deposits occurred between 200 and
400 million years ago.
C) are deposited in warm climates today,but there is good reason to think that they were deposited in cold climates millions of years ago.
D) pinpoint the locations of old subduction zones.

Answer 2

A

Question 3

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.

Answer 3

D

Question 4

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.

Question 5

If we mentally align the continents to fit Wegener's concept of Pangaea,evidence of Late Paleozoic glacial deposits

A) is more difficult to explain than if continents are in their modern configuration.
B) is much more readily explained than if continents are in their modern configuration.
C) makes very little sense in either the Pangaea configuration or the modern configuration.
D) is consistent with both Pangaea and the modern continental configuration.

Question 6

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.

Question 7

Beneath a blanket of sediments,oceanic crust is primarily composed of

A) granite.
B) basalt.
C) limestone.
D) coal.

Question 8

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.

Question 9

Deep-sea trenches are likely to be located near

A) fracture zones.
B) mid-ocean ridges.
C) volcanic arcs.
D) seamounts.

Question 10

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.

Question 11

The term and concept of seafloor spreading were developed by

A) Harry Hess and Alfred Wegener.
B) Robert Dietz and Alfred Wegener.
C) Alfred Wegener.
D) Harry Hess and Robert Dietz.

Question 12

What can be said about the ocean sediments collected from location B as compared to location D?

A) They are thicker and older.
B) They are thinner and older.
C) They are thinner and younger.
D) They are thicker and younger.

Question 13

Wegener's evidence for a united Pangaea comes from the fossil record of which type of organisms?

A) plant pollen
B) plankton
C) marine animals
D) land animals

Question 14

With increasing distance from a mid-ocean ridge,the age of oceanic crust

A) increases.
B) decreases.
C) stays constant.
D) varies randomly.

Question 15

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.

Question 16

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.

Question 17

_________ 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

Question 18

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.

Question 19

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.

Question 20

Which of these is a result of plate tectonics?

A) glaciation
B) seafloor spreading
C) extinction
D) convection in the outer core

Question 21

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.

Question 22

Marine magnetic anomaly belts run parallel to

A) mid-ocean ridges.
B) fracture zones.
C) continental coastlines.
D) continental shelves.

Question 23

On either side of a mid-ocean ridge,oceanic lithosphere slowly _________

A) rises because it becomes thicker away from the ridge.
B) rises because it becomes buoyant.
C) sinks into the asthenosphere because it cools and thickens,increasing in density.
D) sinks into the asthenosphere because convection pulls it downward.

Question 24

Subduction zones are found at _________ plate boundaries.

A) divergent
B) transvergent
C) convergent
D) transform

Question 25

Continental lithosphere is approximately 150 km thick,while old oceanic lithosphere away from mid-ocean ridges is

A) 1 km thick.
B) 100 km thick.
C) similar in thickness to continental lithosphere.
D) unpredictable,because the thickness of old lithosphere is highly variable.

Question 26

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.

Question 27

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.

Question 28

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.
D) is absent because there are no earthquakes at subduction zones.

Question 29

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.

Question 30

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.

Question 31

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

Question 32

Which basic type of plate boundary is shown in the image below?

A) convergent
B) divergent
C) transform
D) submerged

Question 33

Paleomagnetic evidence for seafloor spreading is found in:

A) basaltic rocks.
B) ocean floor sediments.
C) continental sediments.
D) all rocks and minerals.

Question 34

Continental lithosphere does not subduct because it is too

A) thick.
B) buoyant.
C) young.
D) warm.

Question 35

The rock produced at mid-ocean ridges consists of

A) 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.

Question 36

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).

Question 37

Continental coastlines that occur within the interior of a lithospheric plate are called ___________ margins.

A) internal
B) passive
C) active
D) inert

Question 38

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.

Question 39

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.

Question 40

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.

Question 41

What are magnetic anomalies? Why are these important supports for the theory of seafloor spreading?

Question 42

How can hot-spot volcanoes be used to measure past plate velocities?

Question 43

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.

Question 44

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.

Question 45

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

Question 46

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.

Question 47

In a hot-spot volcanic island chain,such as the Hawaiian Islands,which of the following is true?

A) All volcanoes in the chain can be simultaneously active.
B) The ages and distance between volcanoes can be used to calculate plate velocities.
C) The presence of volcanism is related to a plate boundary.
D) The magma source moves to form a hot-spot track.

Question 48

At transform plate boundaries,

A) earthquakes are common but volcanoes are absent.
B) volcanoes are common but earthquakes do not occur.
C) both earthquakes and volcanoes are common.
D) neither earthquakes nor volcanoes are common.

Question 49

Why is it possible for oceanic lithosphere to subduct under continental lithosphere at a convergent boundary but continental lithosphere cannot subduct under oceanic lithosphere?

Question 50

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.

Question 51

In plate tectonics,a triple junction is a place on the Earth's surface where

A) three volcanoes form a tight,triangular cluster.
B) glacial ice,continental rocks,and the ocean can be found together.
C) the boundaries of three lithospheric plates meet at a single point.
D) all three of the basic rock types are found in the same location.

Question 52

What evidence did Alfred Wegener use to support his continental-drift hypothesis and the formation and break-up of Pangaea? Was the evidence compelling? Why or why not?

Question 53

Compare and contrast a convergent boundary involving two continental plates with a convergent boundary involving two oceanic plates.

Question 54

What are deep sea trenches and volcanic island arcs,and why are these features commonly adjacent to each other?

Question 55

Describe how the thickness and age of sediments on the seafloor change with distance from a mid-ocean ridge.What can be learned from this?

Question 56

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

Question 57

Describe the process of seafloor spreading,making sure to address why the diameter of the Earth is not growing.

Question 58

What does the distribution of earthquakes around the globe tell us about plate tectonics? How do earthquakes differ among the three types of plate boundaries?

Question 59

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

Question 60

How does continental rifting lead to the formation of a new plate boundary and new ocean basin?