Deck 4: Ocean Basins

Question 1

What type of margin is generally steep?

A) Passive margin
B) Active margin
C) Continental margin
D) Shelf breaks

Answer 1

B
Active margins are generally steep, especially in comparison to passive margins. Information can be found in the section Continental Margins May Be Active or Passive.

Question 2

A continental margin facing a spreading ridge is considered ____ and ____.

A) a passive margin; converging
B) a passive margin; diverging
C) an active margin; diverging
D) an active margin; converging

Answer 2

B
These types of continental margins are considered passive because there is relatively little earthquake and volcanic activity, especially in comparison to converging plate boundaries. Areas of ridges are diverging because they are moving away from one another. Information can be found in the section Continental Margins May Be Active or Passive.

Question 3

John Murray was an oceanographer who sailed on the HMS Challenger between 1872 and 1876 and he completed the following

A) Edited 50 volumes that resulted from the HMS Challenger expedition
B) Used satellites to pinpoint his position along his expedition
C) Discovered deep sea vents
D) Provide evidence of chemosynthesis

Answer 3

A
Sir John Murray was a distinguished oceanographer who edited 50 volumes from the HMS Challenger expedition that occurred from 1972- 1976, well before the discovery of plate tectonics, hydrothermal vents, chemosynthesis and satellite technology. Information can be found in the section Insights to a National Geographic Explorer.

Question 4

What partly explains the seabed topography we observe?

A) The jostling due to plate tectonics.
B) The greater density of continental lithosphere.
C) The presence of continental margins.
D) The little interaction with the asthenosphere.

Question 5

What statement is true of the surface area of oceanic ridges and their associated features?

A) They consist of slightly less area than that of all the land above sea level.
B) They consist of more area than that of all land above sea level.
C) These are almost always located in the mid-ocean.
D) These areas are largely covered by sediments.

Question 6

What vessel made the first continuous profile across the ocean?

A) USS Stewart
B) HMS Challenger
C) Meteor
D) Mars Reconnaissance Orbiter

Question 7

If oceanic ridges in the Pacific are more active, then it is expected that the ridges are:

A) steeper in profile.
B) narrow.
C) wide.
D) the only areas to find transform faults.

Question 8

Which is not a major factor in the width of a continental shelf?

A) The proximity to a plate boundary
B) The speed of ocean currents
C) Natural dams that allow sediment accumulation
D) The number of rivers depositing new sediments

Question 9

The submerged outer edge of a continent is called:

A) a continental shelf
B) a continental margin
C) an active margin
D) a continental rise

Question 10

What is the origin of most abyssal plain sediments?

A) Deep-ocean basalt
B) Biological activity
C) New crust development
D) Erosion from the continent

Question 11

What is not a general characteristic of an active margin?

A) A broad shelf
B) Faulting and volcanism
C) Varied topography
D) Little sedimentation

Question 12

What is a Pacific-type margin referring to?

A) Diverging plate boundary
B) Passive margin
C) Active margin
D) Rift valley

Question 13

Who led the earliest bathymetric studies?

A) Captain James Cook
B) Posidonius
C) Scientists of the HMS Challenger
D) Aristotle

Question 14

What specifically connects the continental shelves to the deep-ocean floor?

A) Continental rise
B) Continental slope
C) Shelf break
D) Submarine canyon

Question 15

How long is it estimated to take the ocean's volume of water to circulate through the oceanic crust at spreading centers?

A) 1 million years
B) 10 million years
C) 100 million years
D) 1 billion years

Question 16

Where are abyssal plains most common?

A) Atlantic Ocean
B) Pacific Ocean
C) Indian Ocean
D) Southern Ocean

Question 17

What is a disadvantage of using multibeam echo systems to map the entire seafloor?

A) It can only detect a single narrow corridor of the seafloor.
B) There are many beams that radiate from the ship's hull.
C) There are very few vessels that are actually outfitted with these systems.
D) The systems send a pulse of sound every ten seconds.

Question 18

What is not thought to have an effect on the formation of submarine canyons?

A) The sea level
B) Turbidity currents
C) Earthquakes
D) Geothermal heating

Question 19

What offsets the mid-Atlantic ridge's movement at fairly regular intervals?

A) Hydrothermal vents
B) Cooling lithosphere
C) Transform faults
D) Seamounts

Question 20

What is considered an important factor in shaping western boundary continental rises?

A) Turbidity currents
B) The width of the shelf slope
C) Erosion rates
D) Deep-ocean currents

Question 21

What is a characteristic of the water that is expelled from hydrothermal vents?

A) The water is colder than when entering the vent
B) The water is enriched with metals.
C) The water has higher concentrations of organic material
D) The water has lower concentrations of dissolved gases

Question 22

What was not a factor in making the mapping of the Earth's ocean more difficult?

A) The water covering our planet
B) The clouds in the atmosphere
C) Technology to measure depths
D) The gravitational pull of underwater features

Question 23

Where does most of the material on the continental shelf come from?

A) Erosion from the adjacent continent
B) Sediments transported from rivers
C) Accumulations behind natural dams
D) New crust formation

Question 24

Only temperature and salinity have an effect on the speed of sound.

Question 25

What process explains how hydrothermal vents are created?

A) Fracture zones
B) Conduction
C) Convection
D) Pressure

Question 26

The weight of ice atop a continent can depress the depth of the shelf break.

Question 27

Trenches are often the originators of large earthquakes and tsunamis.

Question 28

Turbidity currents are propelled by the water within them.

Question 29

Deep-ocean basins can be covered by sediments up to 5 kilometers (3 miles) thick.

Question 30

Continental rises are found along active margins due to the variation in topography.

Question 31

Hydrothermal vents are only found in the depths of the ocean.

Question 32

What type of bathymetric feature was heavily influenced by wave action at some point in its history?

A) Abyssal hill
B) Seamount
C) Guyot
D) Trench

Question 33

The continental margin is divided into three sections with the continental slope blending the continental margin into the deep-ocean basins.

Question 34

Satellites use ____ to calculate the depths of the ocean.

A) variations in elevation of surface water
B) multibeam echo sounding
C) radiometrics
D) variations in ocean density

Question 35

Over half of the Earth's solid surface is at least 3,000 meters below sea level.

Question 36

The sinking of the RMS Titanic fueled research that would change the science of bathymetry.

Question 37

____ are likely to be found in subduction zones.

A) Abyssal hills
B) Submarine canyons
C) Mid-ocean ridges
D) Trenches

Question 38

What is the flatness of abyssal plains associated with?

A) The large amounts of sediment
B) The depth of abyssal plains
C) The pressure above the abyssal plains
D) The lack of sediment

Question 39

What is a characteristic of transform faults?

A) They are fractures along two plates that slide vertically.
B) They move in opposite directions, horizontally of each other.
C) They are just as active as fracture zones.
D) All of these choices are true.

Question 40

What transports most of the sediment that forms the continental rise?

A) Plate tectonics
B) Turbidity currents
C) Convection
D) Active margin geological activity

Question 41

Active margins tend to be narrow in comparison to broad passive margins.

Question 42

Describe what trenches and island arcs are. Why are these features linked with large earthquakes and tsunamis?

Question 43

The continental crust has a greater percentage of continental shelves and slopes than mountains.

Question 44

What is a hydrothermal vent? What process is involved in their making? Who is responsible for discovering these vents?

Question 45

What is a continental margin? What are the differences between active and passive margins? Include alternative names for the margins and the plate boundaries associated with each.

Question 46

How did the study of bathymetry progress with new technologies? Include important developments and events in history that impacted bathymetry.

Question 47

Sediments on the deep-ocean floor are able to give information on the age and history of the surrounding continents and even the biological productivity of the water itself.

Question 48

The fundamental success of ocean depth measurements taken by satellites is based on the variation of gravitational pull associated with bathymetric features.

Question 49

Describe how submarine canyons are formed? Where are they formed? How have past ice ages affected the formation of submarine canyons?

Question 50

Fracture zones are seismically inactive areas that show evidence of past transform fault activity.