Deck 9: Oceans: The Last Frontier

Question 1

Which of the following would NOT be associated with turbidity currents?

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

Answer 1

D

Question 2

No thermocline exists in high-latitude regions because there is little temperature difference between the top and bottom of the water column. In such a situation the water column is said to be ________.

A)isothermal
B)multithermal
C)clinothermal
D)pycnoclinal

Answer 2

A

Question 3

How many seconds would it take an echo sounder's ping to make the trip from a ship to the Challenger Deep (10,994 meters)and back? Recall that depth = 1/2 (1500 m/sec × Echo travel time).

A)0)1466 seconds
B)1)466 seconds
C)14.66 seconds
D)146.6 seconds

Answer 3

C

Question 4

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

A)a sound pulse travels from a ship to the seafloor and back
B)a laser beam to travels from a ship to the seafloor and back
C)a radar pulse to travel from a ship to the seafloor and back
D)a radar pulse to travel from a satellite in orbit around Earth to the sea surface and back

Question 5

Examine the graph. At what latitude do we find the maximum salinity?

A)65° north
B)25° north
C)both 25° north and south
D)5° south

Question 6

The ________ Ocean is largest; the ________ Ocean is smallest.

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

Question 7

Examine the graph. At what latitude is the ratio of ocean water to land at its maximum? Choose from the following options.

A)between 60° and 65° north
B)between 0° and 5° north
C)between 25° and 30° south
D)between 60° and 65° south

Question 8

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

A)Guyots
B)Deep-ocean trenches
C)Submarine canyons
D)Oceanic ridges

Question 9

Where would you go to find "black smokers" (deep sea hydrothermal vents)?

A)deep-ocean trench
B)oceanic ridge
C)guyot
D)continental rise

Question 10

Where is the continental rise?

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 11

The crests of mid-oceanic ridges ________.

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

Question 12

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

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

Question 13

How does the average depth of the oceans compare to the average elevation of the continents?

A)The oceans are hundreds of times deeper on average than the continents' average elevation.
B)The continents stick up above sea level by about the same vertical distance that the ocean floor is below sea level.
C)The ocean floors are about four times as deep, on average, than the average elevation of the continents above sea level.
D)The ocean floors are higher in elevation than the continents' average distance below sea level.

Question 14

Ocean covers approximately ________ percent of Earth's surface

A)11
B)51
C)71
D)91

Question 15

Which element is most common dissolved in seawater?

A)sodium
B)chlorine
C)magnesium
D)gold

Question 16

Which of the following is associated with oceanic ridges?

A)rift zones
B)elevated topography
C)volcanoes
D)all of the above

Question 17

Manganese nodules are an example of ________ sediment.

A)terrigenous
B)biogenous
C)hydrogenous
D)manganesogenous

Question 18

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 19

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

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

Question 20

Which one of the following statements concerning oceanic ridges is false?

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

Question 21

Submarine canyons form the deepest parts of the ocean basins.

Question 22

Manganese nodules do not accumulate in shallow water.

Question 23

A deep-sea fan at the base of a continental slope is more likely to be covered with thick turbidite layers than a mid-ocean ridge.

Question 24

Which of the four lettered locations in this figure shows a guyot?

A)A
B)B
C)C
D)D

Question 25

The deep-ocean basin makes up about 5% of the ocean floor's area.

Question 26

The surface waters in regions where evaporation rates are high, such as the Red Sea, have higher than average salinities.

Question 27

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

Question 28

The west coast of South America and the east coast of North America display the same kind of continental margin.

Question 29

Turbidites and siliceous oozes are both biogenous sediments.

Question 30

The average salinity of seawater is 3.5%.

Question 31

________ is the proportion of dissolved salts to pure water.

A)Pycnocline
B)Salinity
C)Density
D)Subduction

Question 32

The proportion of land to water is about the same in both the Northern Hemisphere as in the Southern Hemisphere.

Question 33

In subduction erosion, sediment and rock are scraped off the bottom of the overriding plate and transported into the mantle by the subducting plate.

Question 34

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

Question 35

The ocean has a three-part layered structure (surface mixed zone, transitional zone, and deep zone)at all latitudes.

Question 36

At low latitudes, the ________ is a zone of rapid temperature change over a relatively short depth. It is associated with a similar depth zone marked by a change in density, called the ________.

A)thermocline; pycnocline
B)pycnocline; thermocline
C)thermocline; isotherm
D)isotherm; pycnocline

Question 37

What kind of seawater is densest?

A)warm, low salinity
B)warm, high salinity
C)cold, low salinity
D)cold, high salinity

Question 38

Turbidity currents are downslope movements of dense, sediment-laden water.

Question 39

Where does an accretionary wedge form?

A)deep-ocean trench
B)oceanic ridge
C)seamount
D)continental rise

Question 40

Oceanic ridges are elevated features because they are warm and therefore less dense than older, colder oceanic lithosphere.

Question 41

Identify and label the features shown on the figure.

Question 42

________ is the total amount of solid material dissolved in water.

Question 43

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

Question 44

Valleys that lead from the continental shelf into deeper waters are known as ________. Typically, we find ________ along the continental rise at the bottom of these valleys.

Question 45

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

Question 46

The layer in the ocean that is characterized by a rapid temperature change and marks the transition between the warm surface layer and the deep zone of cold water is known as the ________.

Question 47

Compare and contrast the three types of seafloor sediments, and given an example of each.

Question 48

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

Question 49

A rising mantle plume may be responsible for the vast outpouring of lava associated with a(n)________.

Question 50

Minerals that crystallize directly from seawater are examples of ________ sediment.

Question 51

Attraction of seawater to submarine features like seamounts and oceanic ridges is due to ________; it results in areas where the surface of the ocean bulges upward by a small amount.

Question 52

The map shows the bathymetry of the ocean floor off the coast of Los Angeles, California. Note the prominent submarine canyon on the continental shelf and slope. How was this feature likely generated?

Question 53

The salts in seawater come both from the weathering of the continents and ________ by submarine volcanoes.

Question 54

The oceanic ridge system is the ________ topographic feature on Earth.

Question 55

Why doesn't the sea get saltier over time?

Question 56

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

Question 57

The oceanic ridge is elevated above the abyssal plain because it is ________.

Question 58

The HMS Challenger was the world's first ________ survey vessel.

Question 59

A pile of clam shells is an example of ________ sediment.

Question 60

Match the items in the first column with the correct descriptions in the second column.

A)sediment derived from the weathering of rock, mainly on the continents
B)sediment derived from dissolved salts in seawater
C)a layer of rapid temperature change
D)the multi-disciplinary science that studies the oceans
E)a layer of rapid density change
F)the oceanic equivalent of topography: the three-dimensional "shape" of the seafloor
G)a measure of the amount of dissolved salts in a given volume of water
H)sediment from the shells or skeletal material of living organisms
1)oceanography
2)salinity
3)thermocline
4)pycnocline
5)bathymetry
6)terrigenous
7)hydrogenous
8)biogenous

Question 61

Consider this scenario: you are hired as the sonar technician on an oceanographic research vessel. The ship is moving at a constant speed on a linear survey. Your echo-sounding equipment gives you the following dataset over the course of the 170-km transect:

Recall that the average speed of sound waves in water is 1500 meters per second. What submarine feature has been documented by these data? Interpret the dataset as fully as possible.

Question 62

Sketch a cross-section through a continent that has an active margin on one side and a passive margin on the other side. Label relevant features and briefly (one or two sentences)describe what distinguishes the two kinds of continental margins.

Question 63

Imagine that a helicopter drops you off on an island. You look north and south and see a long line of active volcanic islands poking up above the ocean's waves. At what sort of plate boundary are you likely to be? What is one way that could you test this interpretation to see if it is valid?