Deck 3: The Sea Floor and Its Sediments

Question 1

Geologic dredges are used to quantitatively sample the seafloor.

Answer 1

False

Question 2

Abyssal hills are single, rounded domes extending at least 3km above the deep-sea floor.

Answer 2

False

Question 3

In the deep sea biogenous sediments make up the majority of the pelagic deposits.

Answer 3

True

Question 4

Manganese nodules are composed entirely of manganese.

Question 5

Oil and gas represent only 50% of the mineral value presently taken from the seafloor.

Question 6

Large particles sink faster than small particles of the same density.

Question 7

Submarine canyons are features associated principally with the continental slope; some are associated with past or present rivers.

Question 8

Calcareous sediments of the North Atlantic occur at deeper depths than calcareous sediments in the North Pacific.

Question 9

The flat-topped seamounts called guyots found with their tops 1800m below the surface were flattened by erosion at the sea surface.

Question 10

Particles of a well-sorted sediment sample fall within a limited size range.

Question 11

Siliceous oozes are found at all ocean depths because of the slow dissolving rate of silica.

Question 12

Calcareous deposits are most likely to be found in more acidic seawater undersaturated in calcite.

Question 13

Red mud or brown clay deposits are found under oceanic regions of high biological productivity.

Question 14

Satellite radar altimeters measure sea surface topography.

Question 15

Large boulders and cobbles scattered over the deep-sea floor at high-temperate latitudes were most likely deposited by turbidity currents.

Question 16

Hydrogenous sediments of the deep-ocean floor predominate in regions where other sediment sources are reduced.

Question 17

The distinctive layering found in marine sediments indicates that the properties of the sediment and the rates of sedimentation have varied with time.

Question 18

Calcareous oozes of the open ocean are associated with midocean ridge and rise systems rather than the deep-ocean basin floor.

Question 19

The vertical relief across the mountains of the western United States is similar to the vertical relief across the Mid-Atlantic Ridge.

Question 20

The smaller the footprint of a sound beam, the greater the detail of the seafloor features.

Question 21

Major deposits of silicous oozes from the radiolaria are found centered on which latitudes?

A) 5 °N
B) 20 °N and S
C) 30 °N and S
D) 45 °N and S
E) 65 °N and S

Question 22

The floor of a major ocean basin is called a(n)

A) ocean valley floor.
B) abyssal plain.
C) midocean flat.
D) seamount province.
E) ridge depression.

Question 23

Lithogenous sediment is

A) derived from rock.
B) derived from plants and animals.
C) always found at depths over 4500m.
D) always associated with deep-sea trenches.
E) derived from the chemistry of the water.

Question 24

A fathom is a unit of

A) distance.
B) depth.
C) speed.
D) weight.
E) time.

Question 25

Flat-topped, submerged seamounts are referred to as

A) mesas.
B) abyssal hills.
C) atolls.
D) guyots.
E) flattops.

Question 26

Pelagic sediments are commonly more fine-grained than neritic sediments.

Question 27

Inactive volcanic seamounts on top of the oceanic crust will

A) continue to elevate with time.
B) subside with time.
C) remain in equilibrium once formed.
D) keep a constant elevation.
E) steepen in slope.

Question 28

Surface coral formations growing around completely submerged seamounts are called

A) atolls.
B) fringing reefs.
C) edge reefs.
D) conical reefs.
E) barrier reefs.

Question 29

What minimum percent must be exceeded for a deep-sea biogenic ooze to be named after its principal component?

A) 75
B) 50
C) 30
D) 20
E) 10

Question 30

Calcareous oozes are more common in deep water than shallow water.

Question 31

Manganese nodules are

A) pelagic ooze.
B) volcanic.
C) lithogenous sediment.
D) pelagic biogenous sediment.
E) pelagic hydrogenous sediment.

Question 32

Continental shelves are geologically part of the continental crust.

Question 33

The continental shelf on the east coast of the U.S. is generally wider than the continental shelf on the west coast of the U.S.

Question 34

Passive continental margins are commonly associated with volcanic and earthquake activity.

Question 35

The deepest depth of the oceans is located in which trench?

A) Japan-Kuril
B) Aleutian
C) Peru-Chile
D) Puerto Rico-Cayman
E) Mariana

Question 36

The continental rise is a product of

A) volcanic activity.
B) sedimentation.
C) seismic upheaval.
D) All of these are correct.
E) None of these are correct.

Question 37

The seafloor tends to be more flat and featureless than the continental areas.

Question 38

The deep ocean basins or areas with depth between 4000m and 6000m cover more of the Earth's surface than the continents.

Question 39

Turbidity currents produce some

A) trenches.
B) abyssal hills.
C) submarine canyons.
D) All of these are correct.
E) None of these are correct.

Question 40

Sediment accumulation in the deep ocean tends to be greater than near the continental margins.

Question 41

Red clay obtains its characteristic color from

A) the remains of bottom organisms.
B) the oxidation of iron.
C) the silica liberated from diatoms.
D) calcium carbonate.
E) bacteria of the deep sea.

Question 42

Side scan sonar images are the product of the

A) reflectivity of the material.
B) depth of the water.
C) angle at which the sound strikes the object.
D) reflectivity of the material and depth of the water.
E) reflectivity of the material, depth of the water, and angle at which the sound strikes the object.

Question 43

Which of the following is least likely to be a major component of marine sediments?

A) Silicous ooze
B) Calcareous ooze
C) Cosmogenous materials
D) Hydrogenous sediments
E) Lithogenous sediments

Question 44

Turbidites are

A) graded sequence of sediments.
B) found in submarine canyons.
C) characterized by coarse sediments on top of fine sediments.
D) graded sequence of sediments and found in submarine canyons.
E) found in submarine canyons and characterized by coarse sediments on top of fine sediments.

Question 45

The silica rich oozes of the Pacific Ocean are due to _______ at high latitudes and ______ at low latitudes.

A) radiolarians, diatoms
B) diatoms, diatoms
C) diatoms, radiolarians
D) radiolarians, radiolarians
E) None of these are correct.

Question 46

Diatomaceous sediments are

A) oozes.
B) found below 4500m.
C) found in cold water.
D) All of these are correct.
E) None of these are correct.

Question 47

Close to shore on the continental shelf at high-temperate latitudes, _______ deposits are most likely to predominate.

A) cosmogenous
B) hydrogenous
C) pelagic
D) neritic
E) terrigenous

Question 48

Sediments found on the seafloor and attributed to processes no longer in existence are called

A) nonexisting sediments.
B) pelagic sediments.
C) relict sediments.
D) rafted sediments.
E) sorted sediments.

Question 49

Which type of sediment is the greatest contributor, on a world scale, to the sediments of the neritic zone?

A) Biogenous
B) Terrigenous
C) Hydrogenous
D) Cosmogenous
E) Volcanic

Question 50

Why do small particles descend to the seafloor at rates exceeding expectation?

A) The particles attract each other
B) The particles increase their density
C) The particles are incorporated into the fecal pellets of small animals
D) The particles attract each other and the particles are incorporated into the fecal pellets of small animals
E) The particles attract each other, the particles increase their density, and the particles are incorporated into the fecal pellets of small animals

Question 51

The particle size of terrigenous sediments generally ________ with distance from shore.

A) increases
B) decreases
C) stays the same
D) become less uniform
E) is less graded

Question 52

Submarine canyons are associated with

A) river systems.
B) turbidity currents.
C) volcanic eruptions.
D) river systems and turbidity currents.
E) turbidity currents and volcanic eruptions.

Question 53

Acoustic profiling is used to study

A) sediment size.
B) sediment distribution.
C) seafloor structure.
D) sediment size and sediment distribution.
E) sediment distribution and seafloor structure.

Question 54

Which of the following is NOT true about passive continental margins?

A) They have little seismic or volcanic activity
B) They form after continents are rifted apart
C) They tend to be wider than active margins
D) They occur away from plate boundaries
E) They are commonly at subduction zones

Question 55

Lithification of sediments produces

A) coral.
B) turbidites.
C) mud flows.
D) rock.
E) red clay.

Question 56

A sediment deposit close to the continental rise having a coarse material overlaid by successively finer materials of nonmarine origin is called a

A) pelagic deposit.
B) rafted deposit.
C) hydrogenic deposit.
D) turbidite.
E) well-sorted deposit.

Question 57

The seabed is presently being mined in the U.S. for

A) phosphorite.
B) manganese nodules.
C) sand and gravel.
D) All of these are correct.
E) None of these are correct.

Question 58

The sediments of the central deep-ocean basins of the North Pacific are formed chiefly from

A) radiolaria.
B) foraminaferia.
C) red clay particles.
D) diatoms.
E) coral reefs.

Question 59

Manganese nodule mining has not developed because of

A) low international market prices in metal.
B) unresolved legal ownership problems.
C) technical and developmental costs.
D) All of these are correct.
E) None of these are correct.

Question 60

Seventy five percent of all marine sediments are

A) terrigenous.
B) neritic.
C) pelagic.
D) suspended in the water column.
E) produced by active seamounts.

Question 61

The deep-sea floor, between 4000 and 6000 m depth, covers more of Earth's surface than the continents.

Question 62

Guyots are flat-topped islands.

Question 63

The _____ of phytoplankton and zooplankton contribute to marine sediments.

A) fecal pellets
B) tests
C) limbs
D) fecal pellets and tests
E) tests and limbs

Question 64

Barrier reefs can develop into atolls as the seafloor sinks with age.

Question 65

Which of the following is NOT an example of a hydrogenous sediment?

A) Manganese nodules
B) Phosphorites
C) Salts
D) Ooliths
E) Tektites

Question 66

The most common topographic features on Earth are probably

A) rivers.
B) beaches.
C) abyssal hills.
D) continental shelves.
E) island arcs.

Question 67

Turbidity currents are often triggered by earthquakes along passive continental margins.

Question 68

In general, coarse sediments are found closer to shore and fine sediments are found further offshore.

Question 69

One fathom is equal to

A) 6 feet.
B) 6 meters.
C) roughly 2 meters.
D) one meter.
E) 6 feet and roughly 2 meters.

Question 70

In general, sedimentation rates decrease the further offshore.

Question 71

Gas hydrates are rich in

A) ethanol.
B) diesel.
C) propane.
D) carbon dioxide.
E) methane.

Question 72

Calcareous sediments are well-preserved in cold, deep water below the CCD.

Question 73

The first scientific voyage to use an echo sounder on a large scale was the

A) Meteor expedition.
B) Beagle expedition.
C) Fram expedition.
D) Discovery expedition.
E) Endeavor expedition.

Question 74

The east coast of South America

A) is a passive continental margin.
B) has a relatively wide continental shelf.
C) is an active continental margin.
D) is marked by a deep ocean trench.
E) is a passive continental margin and has a relatively wide continental shelf.