Ch.10 The Seafloor And Continental Margins Exam Questions

Exploring Geology, 5e (Reynolds)

Chapter 10 The Seafloor and Continental Margins

1) Which of the numbered features on this figure is a continental shelf?

A) 1

B) 2

C) 3

D) 4

2) Which of the numbered features on this figure is a continental slope?

A) 1

B) 2

C) 3

D) 4

3) What feature is on the seafloor near Monterey, California?

A) an active subduction zone that causes earthquakes

B) an active mid-ocean ridge that has opened up a rift on the continental margin

C) a large submarine canyon and a number of smaller ones

D) a circular scar interpreted to represent a huge impact crater

E) None of these choices are correct.

4) What features are NOT recognized on the seafloor near Monterey, California?

A) a canyon partly cut into hard granite

B) faults that cut across the seafloor

C) a broad continental shelf

D) a continental slope

E) All of these features are recognized on the seafloor.

5) Which of the following CANNOT be observed on a seismic-reflection profile?

A) orientation of rock layers

B) shape of the seafloor

C) folds

D) faults

E) All of these can be observed.

6) Which of the following is NOT a way in which we map and investigate the seafloor?

A) bouncing sound waves from a ship off the bottom

B) drilling holes into the seafloor from ships

C) using satellites to observe the sea surface

D) conducting seismic surveys to investigate rock layers

E) We use all of these techniques.

7) Rock units beneath the seafloor can be imaged with sound waves using a method called

A) seismic-reflection profiling.

B) magnetic profiling.

C) bounce profiling.

D) physical profiling.

8) What method produces images of the materials beneath the seafloor using sound waves?

A) seismic-reflection profiling

B) ocean drilling

C) satellites

D) submersibles

9) What information can be determined directly by analyzing drill cores?

A) the type of sediment on the seafloor

B) the rate of sediment deposition

C) the type of rock on the seafloor

D) All of these choices are correct.

10) Which of the following is associated with mid-ocean ridges?

A) a great thickness of oceanic sediment trapped within the central rift

B) very smooth topography as a result of the sedimentary cover

C) melting of the entire thickness of the asthenosphere to produce magma

D) compression that buckles the crust forming the ridge

E) None of these choices are correct.

11) Which of the following is associated with a fast-spreading ridge?

A) rates of about 10 centimeters per year or more

B) a broad ridge because the rocks remain hotter farther from the center of spreading

C) less of a deep central rift than in a slow spreading ridge

D) All of these choices are correct.

12) What occurs near black smokers?

A) Circular features (called chimneys) form, composed of sulfide and sulfate minerals.

B) Heated fresh water is derived from the land.

C) Organic-rich shale burns in the subsurface.

D) Coal-rich layers burn in the subsurface.

E) None of these choices are correct.

13) What is the ultimate source of food for animals living around deep-sea hydrothermal vents?

A) sunlight and photosynthesis

B) the decay of creatures that float on the ocean surface and settle to the bottom

C) nuclear energy from the heated uranium-rich rocks

D) bacteria that break down hydrogen sulfide

14) What is the source of energy for giant worm tubes and clams that live at hydrothermal vents?

A) bacteria that break down H2S

B) plants that grow on the seafloor

C) sunlight

15) Which creatures belong to the community of organisms that live at hydrothermal vents?

A) giant clams

B) red worm tubes

C) white crabs

D) All of these creatures belong to the community of organisms that live at hydrothermal vents.

16) The source of heat for the water emitted by black smokers at the mid-ocean ridges comes from

A) magma.

B) friction.

C) radioactive decay.

D) an unknown source.

17) Which of these numbers is near a site with active seafloor spreading?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

18) Which of these numbers is on the abyssal plane?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

19) Which of these numbers is near a continental shelf?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

20) Which of these numbers is closest to an oceanic trench?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

21) Which of these numbers has the thinnest sequence of marine sediments?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

22) This figure shows ages of seafloor. Which of the numbered sites is on the oldest seafloor, based on its position?

A) 1

B) 2

C) 3

D) 4

23) This figure shows ages of seafloor. Which of the numbered sites is on the youngest seafloor, based on its position?

A) 1

B) 2

C) 3

D) 4

24) This figure shows ages of seafloor. Which pair of numbers likely has crust of similar age?

A) 1 and 2

B) 1 and 3

C) 2 and 3

D) 2 and 4

E) 3 and 4

25) This figure shows ages of seafloor. Which of the numbered sites is on the deepest seafloor, based on its position?

A) 1

B) 2

C) 3

D) 4

26) This figure shows ages of seafloor. Which of the numbered sites is on the shallowest seafloor, based on its position?

A) 1

B) 2

C) 3

D) 4

27) What setting has the thinnest cover of sediment in the oceans?

A) mid-ocean ridges

B) abyssal plain

C) oceanic trenches

D) continental shelves and slopes along passive margins

28) The deepest parts of the seafloor are

A) mid-ocean ridges.

B) abyssal plain.

C) seamounts.

D) oceanic trenches.

E) continental shelves.

29) Which of the following parts of the seafloor are the shallowest?

A) mid-ocean ridges

B) abyssal plain

C) oceanic trenches

D) continental shelves

30) Which parts of the seafloor have the youngest oceanic crust?

A) mid-ocean ridges

B) abyssal plain

C) oceanic trenches

D) continental shelves along passive margins

31) Why does the elevation of the seafloor decrease from the mid-ocean ridge to the abyssal plain?

A) The oceanic lithosphere cools and becomes denser.

B) The weight of sediments depresses the oceanic crust.

C) The oceanic plate is flexed downward near a subduction zone.

D) Slab rollback pulls the oceanic lithosphere deeper.

32) In what setting does the thickest sediment accumulate in the oceans?

A) mid-ocean ridges in any location in the ocean

B) abyssal plain in the middle of the ocean

C) oceanic trenches in the middle of the ocean

D) continental shelves and slopes along passive margins

33) In the Atlantic Ocean, where is the oldest oceanic crust?

A) Mid-ocean ridges

B) Abyssal plain next to the continents

C) Oceanic trenches

D) Seamounts

E) Continental shelves close to the shoreline

34) On a map showing the age of the seafloor, why are the patterns symmetrical in the Atlantic Ocean but not the Pacific Ocean?

A) Spreading along the Atlantic ridge added seafloor to plates on both sides, while subduction has consumed large areas of old oceanic crust in the Pacific.

B) Subduction occurred at the same rate along the eastern and western sides of the Atlantic, but not in the Pacific.

C) Subduction has consumed large areas of old oceanic crust in the Atlantic, more than in the Pacific.

D) Spreading in the Atlantic has been faster than seafloor spreading in the Pacific

35) On the map shown, R has the youngest oceanic crust because

A) it is at a spreading center.

B) it is at a passive margin.

C) it is at a trench.

36) Which area shown on the map has the greatest seafloor depth?

A) (T) trench

B) (P) passive margin

C) (R) oceanic ridges

37) Which area shown on the map has the shallowest seafloor depth?

A) (P) passive continental margin

B) (R) oceanic ridge

C) (T) trench

38) If you wanted to locate hot spots on Earth, which of the following would NOT be good place to look?

A) the volcanically active end of a linear island chain

B) clusters of volcanically active islands

C) Hawaii and the Galapagos

D) All of these would be good places.

39) Most oceanic plateaus are

A) small pieces rifted apart from continents.

B) places where the seafloor has been buckled upward by convergence.

C) constructed by volcanic eruptions probably over mantle plumes.

D) large fan-shaped mounds deposited by turbidity currents.

40) If you drilled into an oceanic plateau, what would you most likely find?

A) a thin layer of oceanic sediment over continental crust

B) andesitic volcanoes buried by turbidity currents

C) a normal thickness of oceanic crust overlain by andesitic volcanoes

D) large amounts of basalt derived from melting in the mantle

41) Most oceanic islands and seamounts are

A) small pieces rifted apart from continents.

B) places where the seafloor has been buckled upward by convergence.

C) constructed by volcanic eruptions that first occur under water.

D) large fan-shaped mounds deposited by turbidity currents.

42) Oceanic plateaus form from basaltic volcanism originating from 

A) hot spots.

B) mid-ocean ridges.

C) trenches.

43) What rock type forms oceanic plateaus? 

A) basalt

B) granite

C) rhyolite

44) Hot spots form linear island chains because 

A) the plate moves relative to the underlying hot spot.

B) they are aligned with trenches formed by subduction.

C) they occur along the mid-oceanic ridges.

45) What do the island chains of Hawaii, Tahiti, and Tristan da Cunha have in common?

A) They formed from hot spots.

B) They are part of island arcs.

C) They are part of an oceanic plateau.

46) The red dots that coincide with volcanically active island chains shown on the map are called

A) hot spots.

B) mid-ocean ridges.

C) abyssal plains.

D) island arcs.

47) The area behind an island arc that develops a spreading center is a(n)

A) back-arc basin.

B) trench.

C) abyssal plain.

D) passive margin.

48) Which of the following is associated with a typical island arc?

A) oceanic trench

B) subduction

C) melting in the mantle

D) ocean-ocean convergence

E) All of these choices are correct.

49) Which of the following is an island arc?

A) Hawaiian Islands

B) Iceland

C) the East African Rift

D) Aleutian Islands

E) None of these choices are correct.

50) What processes can occur in front of or behind some island arcs?

A) trench rollback or back-arc rifting

B) fold and thrust belts in the mountains, and formation of a continental plateau

C) formation of an oceanic plateau related to subduction

D) All of these choices are correct.

51) Island arcs are curved because

A) the shapes of the continents were arcuate as they rifted apart.

B) the shape of the mid-ocean ridge matches the shape of the continents.

C) Earth is a sphere, not a flat plane.

D) most terranes added to the continental margin are circular.

52) Island arcs form in association with what type of tectonic setting?

A) ocean-ocean convergent

B) ocean-continent convergent

C) transform

D) continental rift

53) Subduction zones in the open ocean produce a (an)

A) island arc.

B) abyssal plain.

C) mid-ocean ridge.

54) Which of the following is the present plate-tectonic setting of oceanic crust in the Bering Sea?

A) It contains a mid-ocean ridge.

B) It is being generated by back-arc spreading.

C) It does not contain any currently active plate boundaries.

D) It was formed by thinning of continental crust.

55) Which of the following is the presently occurring near the Sea of Japan?

A) Oceanic crust in the sea of Japan is being generated by back-arc spreading.

B) Japan is moving closer to Asia over time.

C) Volcanoes in Japan are related to subduction of oceanic crust that forms in the Sea of Japan.

D) All of these choices are correct.

56) Which of the following seas was formed when spreading and transform faulting sliced off a sliver of the continent?

A) Sea of Japan

B) Bering Sea

C) Philippine Sea

D) Gulf of California

57) Which of the following letters marks the Bering Sea and Aleutian Islands off Alaska?

A) A

B) B

C) C

D) D

E) E

58) Which of the following letters marks the Sea of Japan?

A) A

B) B

C) C

D) D

E) E

59) Which of the following seas currently has back-arc spreading?

A) Sea of Japan

B) Baltic Sea

C) Bering Sea

D) Gulf of California

E) All of these choices are correct.

60) Which of the following sea(s) was formed when subduction jumped or shifted outward from the continent?

A) North Sea

B) Bering Sea

C) Philippine Sea

D) Gulf of California

E) All of these choices are correct.

61) The Sea of Japan formed as a deep basin between Asia and Japan because

A) of back-arc seafloor spreading.

B) of trench subduction.

C) it is part of a continental platform.

62) Submerged ridges in the Philippine Sea were formed by a

A) back-arc basin.

B) trench.

C) hot spot.

63) Which of the following letters marks the Red Sea?

A) A

B) B

C) C

D) D

E) E

64) Which of the following seas was formed by rifting or seafloor spreading?

A) North Sea

B) Red Sea

C) Persian Gulf

D) Baltic Sea

65) Which of the following seas was formed by loading of thrust sheets of the Zagros Mountains?

A) North Sea

B) Red Sea

C) Persian Gulf

D) Baltic Sea

E) All of these choices are correct.

66) Which sea is shallow because it is underlain by continental crust?

A) Mediterranean Sea

B) Red Sea

C) Black Sea

D) Persian Gulf

67) Which of the following letters marks the Persian Gulf?

A) A

B) B

C) C

D) D

E) E

68) Which sea was a lake prior to being flooded by the ocean at the end of the Ice Age?

A) Black Sea

B) Caspian Sea

C) Persian Gulf

D) Mediterranean Sea

69) Which of these numbered features is an atoll?

A) 1

B) 2

C) 3

D) All of these choices are correct.

E) None of these choices are correct.

70) What is a popular model for the formation of an atoll?

A) A moderate-sized meteoroid forms a circular crater on the seafloor.

B) A volcanic eruption forms a large circular caldera.

C) A volcanic island forms and subsides.

D) A barrier reef becomes buried by volcanic eruptions.

71) Which of the following places would NOT be a good place to visit a reef?

A) shallow seas that are relatively free of suspended sediment

B) the area offshore of northeastern Australia

C) the Caribbean

D) islands in the southwestern Pacific Ocean

E) shallow, clear waters off Iceland

72) Which of the following is a consistent feature of reefs and atolls?

A) volcanic islands

B) passive continental margins

C) divergent plate boundaries

D) carbonate rocks and accumulations

73) Which conditions promote the growth of coral reefs?

A) shallow water

B) warm water

C) clear water

D) All of these conditions promote the growth of coral reefs.

74) Why did the Great Barrier Reef in Australia grow upward, forming the largest organic structure on Earth?

A) Sea level rose.

B) Sea level fell.

C) Elevation of the seafloor rose.

75) Which of the following locations contains modern coral reefs?

A) Bahamas

B) Philippines

C) Polynesia

D) All of these locations are contain modern coral reefs.

76) Which of these numbered features is on the continental shelf?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

77) Which of these numbered features is on the continental slope?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

78) Which of these numbered features has the thinnest sediment?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

79) Which of these numbered features is over continental crust that has been the most thinned by rifting?

A) 1

B) 2

C) 3

D) 4

E) None of these choices are correct.

80) Which of the following are associated with turbidity currents?

A) A dense slurry of water and sediment that moves downhill

B) submarine canyons

C) submarine fans

D) graded beds

E) All of these choices are correct.

81) Which of the following is associated with a continental slope?

A) submarine canyons

B) turbidity currents

C) submarine landslides

D) All of these choices are correct.

82) If you were looking for graded beds, where would be a good place to look?

A) in a warm and shallow lagoon

B) in the center of an atoll

C) just offshore of a sediment-poor beach

D) in a submarine fan

E) None of these choices are correct.

83) What causes the seafloor to deepen across a typical continental slope?

A) thinning of continental crust because of normal faults

B) a transition from continental crust to oceanic crust

C) down flexing of oceanic crust because of subduction

D) deposition of sediment from turbidity currents

E) thinning of continental crust because of normal faults and a transition from continental crust to oceanic crust

84) The abrupt change from thinned, faulted continental crust to oceanic crust occurs at the

A) continental slope.

B) continental shelf.

C) continental rise.

D) abyssal plain.

85) What process thins the continental crust before it meets the oceanic crust at the continental slope?

A) normal faulting

B) subduction

C) river erosion

D) sediment deposition

86) Submarine canyons in the continental slope are eroded by

A) turbidity currents.

B) rivers.

C) glaciers.

87) Once salt deposits are formed, they can

A) flow upward because they are less dense than normal rocks.

B) slip and flow, allowing overlying rocks to fold and fault.

C) flow down hillslopes, forming a salt glacier.

D) form a steep slope or escarpment on the seafloor.

E) All of these choices are correct.

88) Which of the following features are NOT associated with salt structures along the Gulf Coast of the United States?

A) a layer of salt deposited during continental rifting

B) folding and doming of layers above rising masses of salt

C) puzzling bumps and pits on the seafloor

D) a steep slope or escarpment marking the front of a large mass of salt

E) All of these are present in this region.

89) How do most salt deposits form?

A) dense slurries of sediment and water along continental slopes

B) rapid deposition offshore of deltas, like in the Gulf of Mexico

C) evaporation of water, such as in restricted seaways

D) conversion of limestone to dolostone

90) What are the characteristics of natural salt (NaCl) deposits? 

A) deposited in layers

B) very soluble in water

C) can flow to form domes

D) All of these are characteristics of natural salt deposits.

91) Salt is less dense and weaker than other types of rocks so it flows upward to form 

A) domes.

B) folds.

C) basins.

D) faults.

92) Salt is a weak rock that can flow and therefore it forms

A) domes.

B) slip plane fold thrust faults.

C) salt glaciers.

D) All of these choices are correct.

93) These globes show the position of the continents and ocean basins at various times in the past. What is the correct order of these globes, from oldest to youngest?

A) 1, 2, 3, 4

B) 1, 4, 3, 2

C) 4, 3, 2, 1

D) 4, 3, 1, 2

E) 4, 1, 3, 2

94) These globes show the position of the continents and ocean basins at various times in the past. Which of these represents the oldest time?

A) 1

B) 2

C) 3

D) 4

95) These globes show the position of the continents and ocean basins at various times in the past. Which of these represents the youngest time?

A) 1

B) 2

C) 3

D) 4

96) Approximately when did the central Atlantic Ocean form?

A) four billion years ago

B) two billion years ago

C) two hundred million years ago

D) twenty million years ago

E) two thousand years ago

97) How did the South Atlantic Ocean Form?

A) Asia rifted apart from Europe.

B) Africa and North America collided to form the Appalachian Mountains.

C) A piece of California started moving northward up the west coast.

D) South America rifted apart from Africa.

E) None of these choices are correct.

98) What has happened to the Pacific Ocean in the last 200 million years?

A) It has become deeper as the rate of seafloor spreading increased.

B) It became wider because of seafloor spreading.

C) It became smaller as the Atlantic Ocean opened.

D) It remained unchanged in size.

E) None of these choices are correct.

99) Which two continents rifted apart to form the central Atlantic Ocean?

A) India and Australia

B) South America and Antarctica

C) Europe and Asia

D) North America and Africa

E) None of these choices are correct.

100) Which part of the Atlantic Ocean was the most recently formed?

A) North Atlantic

B) Central Atlantic

C) South Atlantic

D) Pacific Ocean

101) This map shows plate boundaries in the Caribbean region. Which number is in the Gulf of Mexico?

A) 1

B) 2

C) 3

D) 4

E) 5

102) This map shows plate boundaries in the Caribbean region. Which number is closest to a transform boundary?

A) 1

B) 2

C) 3

D) 4

E) 5

103) This map shows plate boundaries in the Caribbean region. Which number is closest to a subduction zone that has formed an island arc?

A) 1

B) 2

C) 3

D) 4

E) 5

104) Which of the following features is NOT present near the present-day Caribbean?

A) a subduction zone

B) an island arc

C) a long transform fault

D) reefs

E) All of these are present.

105) What is currently the dominant type of motion along the northern boundary of the Caribbean plate?

A) subduction of the Caribbean plate beneath Cuba

B) subduction of the Gulf of Mexico beneath the Caribbean plate

C) subduction of the Caribbean plate beneath the volcanoes of Central America

D) seafloor spreading that is moving North America farther from South America

E) a long transform fault moving the Caribbean plate eastward relative to North America

106) How did the Gulf of Mexico form?

A) loading of thrust sheets of the Appalachian and Ouachita Mountains

B) a large meteoroid impact that formed a crater the same size as the present-day gulf

C) back-arc spreading behind the Lesser Antilles arc

D) Mesozoic (Jurassic) continental rifting and seafloor spreading

107) What type of feature is interpreted to cause some parts of the Caribbean to be shallower than expected?

A) seafloor spreading along the Mid-Atlantic Ridge

B) an impact crater that formed at about the time that the dinosaurs died

C) an oceanic plateau that may have originated in the Pacific

D) a currently active hot spot that is not associated with volcanoes

108) What is the origin of the volcanoes in the Lesser Antilles and Central America?

A) two hot spots on either side of the Caribbean plate

B) subduction of oceanic crust beneath the Caribbean plate

C) magma leaking up along transform faults

D) rapid spreading along the Mid-Atlantic Ridge

109) The Lesser Antilles is an example of

A) a subduction zone and island arc.

B) a transform boundary and large scale faulting.

C) rifting and a spreading center.

110) In the ocean Investigation in the textbook, which process(es) probably formed islands?

A) volcanism associated with a hot spot

B) volcanism associated with a mid-ocean ridge

C) fragmentation of continents by long transform faults

D) back-arc spreading

E) All of these choices are correct.

111) In the ocean Investigation in the textbook, what feature is present at the end of a line of islands?

A) submarine canyons

B) a submarine fan

C) an oceanic plateau

D) All of these choices are correct.

112) Where was seafloor spreading occurring in the Investigation area?

A) in the middle of the ocean between two continents

B) beneath a line of islands in the center of the region

C) within the central continent

D) within the eastern continent

E) All of these choices are correct.

113) Based on the features of the ocean floor in this figure, which cross section is the most appropriate match?

A) Cross section A

B) Cross section B

C) Cross section C

D) Cross section D

114) Where was the oceanic plateau relative to the hot spot 20 million years ago?

A) farther away than today

B) the same distance as today

C) half the distance as today

D) on top of the hot spot

115) What was the length of the linear chain of islands 20 million years ago?

A) longer than today

B) same length as today

C) half as long as today

D) it did not yet exist

116) Which way is the plate on which the oceanic plateau rests moving relative to the hot spot at depth? Assume you are looking north.

A) west

B) northwest

C) north

D) northeast

E) south

F) southwest

G) east southeast

117) How wide was the narrow sea between the western continent and adjacent volcanic islands 20 million years ago?

A) wider than it is today

B) same width as it is today

C) a little narrower than it is today

D) it was much narrower

118) How wide was the narrow ocean between the central and eastern continents 20 million years ago?

A) wider than it is today

B) same width as it is today

C) a little narrower than it is today

D) it was much narrower

119) How wide do you think the narrow ocean between the central and eastern continents will be 20 million years in the future?

A) nearly twice as wide as it is today

B) a little wider than today

C) same width as today

D) much narrower than today

120) What do you think might happen to the oceanic plateau 20 million years into the future?

A) It may become much larger than it is today.

B) It may collide with and become part of the central continent.

C) It may subside and become part of the abyssal plain.

D) It may collide with the trench.