Deck 13: The Ocean Floor

Question 1

The gently sloping submerged surface extending from the shoreline toward the deep ocean is termed the ________.

A) continental shelf
B) continental slope
C) continental rise
D) submarine canyon

Answer 1

A

Question 2

The BEST definition of the outer edge of the continental shelf is that point where ________.

A) the gradient becomes very gentle
B) the water depth reaches 100 fathoms
C) it meets an oceanic ridge
D) a rapid steepening of the gradient occurs

Answer 2

D

Question 3

Minerals that crystallize directly from seawater are examples of ________.

A) terrigenous sediment
B) biogenous sediment
C) hydrogenous sediment
D) both terrigenous and biogenous sediment

Answer 3

C

Question 4

Which ocean has the greatest average depth?

A) Atlantic
B) Pacific
C) Indian
D) Arctic

Question 5

The ________ Ocean is largest.

A) Atlantic
B) Pacific
C) Indian
D) Arctic

Question 6

________ develop where oceanic lithosphere bends downward and sinks into the mantle.

A) Submarine canyons
B) Abyssal seamounts
C) Deep ocean trenches
D) Rift valleys on mid-ocean ridges

Question 7

Which of the following is NOT true of deep ocean trenches?

A) They are long and narrow depressions.
B) They are sites where plates plunge back into the mantle.
C) They are geologically very stable.
D) They may act as sediment traps.

Question 8

The crests of mid-oceanic ridges ________.

A) are heavily mantled with sediment
B) lie at depths exceeding 6 kilometers
C) contain active rift zones
D) are geologically old features

Question 9

Which of the following is associated with ocean ridges?

A) rift zones
B) mountainous topography
C) volcanic structures
D) all of these

Question 10

How do calcareous oozes form?

A) The particles are precipitated in warm surface waters and sink to the bottom.
B) The particles are precipitated by bottom-dwelling organisms.
C) The particles are precipitated in the water column below the depth of sunlight penetration and then sink to the bottom.
D) The particles settle out from calcite-rich turbidity currents at depths greater than 15,000 feet.

Question 11

Seamounts ________.

A) are a special type of oceanic trench
B) are volcanoes that form on the ocean floor
C) form only in the Pacific Ocean basin
D) are submarine canyons found near Australia

Question 12

Sediments derived primarily from the products of weathering on the continents are called ________.

A) terrigenous sediment
B) biogenous sediment
C) hydrogenous sediment
D) both terrigenous and biogenous sediment

Question 13

Which one of the following would you NOT associate with turbidity currents?

A) deposits of graded beds
B) density current
C) excavation of submarine canyons
D) formation of seamounts

Question 14

Which one of the following is NOT part of the continental margin?

A) continental shelf
B) continental slope
C) continental rise
D) continental trench

Question 15

It is thought that submarine canyons on the continental slope have been generated by ________.

A) streams when sea level was much lower than it is today
B) streams when sea level was much higher than it is today
C) a submarine glaciation
D) turbidity currents

Question 16

Which one of the following would most likely be covered with thick turbidite layers?

A) axial rift zone of an active mid-ocean spreading center
B) upper part of a steep, narrow, submarine canyon
C) deep-sea fan at the base of a continental slope
D) ocean floor around a conical-shaped seamount

Question 17

The oceans cover approximately ________ percent of Earth's surface.

A) 40
B) 50
C) 60
D) 70

Question 18

Submarine canyons found on the continental slope are believed to have been created ________.

A) by rivers during the ice age
B) by faulting
C) because of a plate plunging into the mantle
D) none of these

Question 19

Manganese nodules are an example of ________.

A) terrigenous sediment
B) biogenous sediment
C) hydrogenous sediment
D) both terrigenous and biogenous sediment

Question 20

An echo sounder operates by measuring the time required for a ________.

A) light beam to travel from a satellite at a known altitude to the sea bottom and back
B) radar beam to travel from a harbor patrol boat to a fuzz-buster on a speeding yacht
C) radar beam to travel from a ship to the seafloor and back
D) sound pulse travels from a ship to the seafloor and back

Question 21

Submerged, flat-topped seamounts are known as guyots.

Question 22

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
a. continental shelf b. continental rise c. continental slope d. continental volcanic arc

Question 23

The Atlantic and Pacific basins have oceanic ridges; the Indian Ocean has no oceanic ridge.

Question 24

Matching. Match the ocean floor sediment with each phrase.
A. biogenous B. terrigenous C. hydrogenous
abyssal plain clay

Question 25

Matching. Match the ocean floor sediment with each phrase.
A. biogenous B. terrigenous C. hydrogenous
diatom ooze

Question 26

Which one of the following concerning mid-ocean ridges is false?

A) They are sites for submarine eruptions of basaltic lava.
B) They are where young lithosphere is added to the edges of spreading, oceanic plates.
C) Terrigenous sediment coverings are very thin or absent.
D) Sediments include thick siliceous ooze deposits and sandy turbidite beds.

Question 27

Matching. Match the ocean floor sediment with each phrase.
A. biogenous B. terrigenous C. hydrogenous
calcareous ooze

Question 28

Concerning the distribution of land and water, which of the following statements is true?

A) The percentage of land and water is about the same in both the Northern and Southern Hemispheres.
B) The Southern Hemisphere has much more water surface than the Northern Hemisphere.
C) The Northern Hemisphere has much more water surface than the Southern Hemisphere.
D) None of the above is true.

Question 29

Matching. Match the ocean floor sediment with each phrase.
A. biogenous B. terrigenous C. hydrogenous
quartz sand

Question 30

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
a. echo sounder b. doppler radar c. sidescan sonar d. radar altimeters

Question 31

Abyssal plains with sediments covering the seafloor igneous rocks are more extensive in the central Pacific basin than in the North Atlantic.

Question 32

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
a. manganese nodules b. calcareous ooze c. metal sulfides d. evaporites

Question 33

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
a. rift valley b. subduction c. volcanic island arc d. trench

Question 34

Matching. Match the ocean floor sediment with each phrase.
A. biogenous B. terrigenous C. hydrogenous
manganese nodule

Question 35

Matching. Match the ocean floor sediment with each phrase.
A. biogenous B. terrigenous C. hydrogenous
turbidite deposits

Question 36

The west coast of South America and the east coast of North America have very different continental margins.

Question 37

The ________ Ocean has more extensive abyssal plains than the Pacific Ocean because it has fewer trenches to trap sediments moving down the continental slope.

A) Indian
B) Atlantic
C) Arctic
D) none of these

Question 38

The continental rise is located ________.

A) at the top of a mid-ocean ridge
B) at the top of the continental slope
C) between an abyssal plain and continental slope
D) at the seaward edge of a deep ocean trench

Question 39

Word Analysis. Examine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
a. sodium chloride b. magnesium chloride c. sodium sulfate d. carbon dioxide

Question 40

"Black smokers" are associated with ________.

A) oceanic ridges
B) mineral-rich waters
C) hot water
D) all of these

Question 41

Flat-topped volcanic structures located on the floor of the deep ocean basin are termed ________.

Question 42

Seafloor hot springs occur mainly in oceanic, abyssal plains.

Question 43

A(n) ________ is the vast, relatively deep, flat, sediment-covered portion of the deep-ocean basin.

Question 44

A(n) ________ marks the site where old, oceanic lithosphere begins its descent into a subduction zone.

Question 45

The gently sloping submerged surface extending from the shoreline toward the deep ocean is termed the ________.

Question 46

Compared to the Southern Hemisphere, a higher percentage of the Northern Hemisphere is water covered.

Question 47

Manganese nodules are an example of ________ sediment.

Question 48

A prominent feature of the Mid-Atlantic Ridge is a very deep linear valley known as a(n) ________ valley.

Question 49

________ continental margins typically exhibit wide, extensive, continental shelves.

Question 50

________ continental margins occur where oceanic lithosphere is being subducted beneath the edge of a continent.

Question 51

Turbidites and siliceous oozes are both biogenous sediments.

Question 52

Discuss the distribution of seafloor sediments in the ocean basins. What are the different types of sediments, and what are the factors that control their distribution (geologic setting, climate, etc.)?

Question 53

The continental rise lies at the bottom of the continental slope.

Question 54

Valleys that lead from the continental shelf into deeper waters are known as ________.

Question 55

Sand, silt, and clays deposited on the ocean floor are described as terrigenous sediments.

Question 56

Manganese nodules do not accumulate below 4500 meters depth because the manganese minerals are highly soluble in seawater below that depth.

Question 57

The most extensive mountain range on Earth extends for about 65,000 kilometers on the ocean floor and is known as the ________.

Question 58

A(n) ________ is a volcanic mountain, built up from the seafloor that never reached the sea surface.

Question 59

________ sediment consists of shells and hard parts of marine organisms.

Question 60

Submarine canyons form the deepest parts of the ocean basins.

Question 61

What type of continental margin is illustrated in the diagram below?

Question 62

Examine Figure 13.C from Earth Science, 12e below. Briefly explain the main points of Charles Darwin's hypothesis on coral atoll formation. Have we tested his hypothesis and is it still thought to be correct today? Can you think of another possible explanation that would explain the origin of such coral atolls?

Question 63

How might you distinguish an ancient passive continental margin from an active continental margin? What geologic features or rock sequences would be unique to each one? Also, what features of modern continental margins may not be preserved in the geologic record?

Question 64

Label the different features of the passive continental margin on the diagram below.