Oceanography Ch 3

Ocean trenches are deep linear scars in the ocean floor caused by the divergence of plates along divergent plate boundaries.

False

Seamounts form from ancient tablemounts.

False

The continental shelf is generally defined as a steeply sloping zone extending from the shoreline to the shelf break.

False

The deepest portions of the ocean are part of the relatively narrow features called submarine canyons.

False

The three major provinces of the ocean floor are continental margins, deep-ocean basins, and submarine canyons.

False

Explain what graded bedding is and how it forms.

Graded bedding is created by turbidity currents. As the current slows, the larger suspended pieces of sediment fall out first, and then progressively smaller pieces settle out.

Black smokers are hydrothermal vents that discharge superheated water with high concentrations of metal sulfides.

True

Oceanic ridges are cut by a number of transform faults, which offset spreading zones.

True

Satellites measurements of the ocean surface can be used to make maps of the seafloor.

True

Sediments of the continental rise can exhibit characteristics similar to those formed by rivers on land.

True

Sediments deposited by the process of suspension settling produce the main sediment found on ___________. Select only one answer.

abyssal plains

Extending from the base of the continental rises into the deep-ocean basins are flat depositional surfaces called:

abyssal plains.

ocean trench

deep linear scars on the deep-ocean floor caused by plate convergence

Passive continental margins are characterized by all of the following except:

deep-sea trenches.

What process(es) is/are involved in the formation of continental shelves?

deposition by waves

Oceanic ridges and rises result from seafloor spreading along:

divergent plate boundaries.

abyssal plain

flat depositional surfaces that cover extensive portions of the deep-ocean basins

All of the following are considered part of the continental margin except the:

fracture zone.

The direction of motion along a seafloor transform fault is:

in the same direction as the plates are spreading.

Most ocean floor features owe their origins to _________.

plate tectonic processes

Measurement of ocean floor bathymetry from satellites relies on ___________. Select only one answer.

sea surface elevation, which varies depending on the shape of the underlying sea floor

Volcanic peaks on the deep-ocean floor with conical tops are called:

seamounts.

The method that used most frequently to investigate sediment and rock layers of the sea floor is:

sound waves (specifically seismic reflecting profiling).

The majority of ocean trenches are associated with ___________.

the Pacific Ring of Fire

Along the margins of the Pacific are found most of Earth's:

oceanic trenches.

The greatest proportion of Earth's surface lies in this elevation/depth interval.

4,000-5,000 m below sea level

Describe how an echo sounder works.

An echo sounder sends a sound signal from a ship downward into the ocean, where it produces echoes when it bounces off any density difference (e.g., the seafloor). The time it takes for the echoes to return to the point of origination is then used to determine the depth and corresponding shape of the ocean floor.

A ship's fathometer (an echo sounder) transmits a sound pulse and records the return of an echo 7.4 seconds later. If the speed of sound in water is 1,500 m/second, what is the water depth in meters?

D = V x T/2 5550 meters

Due to the very harsh environmental conditions, very few types of organisms are found in association with hydrothermal vents.

False

Describe characteristics and features of the mid-ocean ridge, including the difference between oceanic ridges and oceanic rises.

The mid-ocean ridge is a topographically high feature, composed of basaltic lavas. Along the crest is a rift valley created by seafloor spreading. Cracks and faults are commonly observed in the central rift valley. Ocean ridges are segments of the mid-ocean ridge with a prominent rift valley and steep, rugged slopes resulting from slower plate divergence. Oceanic rises have slopes that are gentler and less rugged due to faster plate divergence.

continental shelf

a generally flat zone extending from the shore to the shelf break

multi-beam sonar

a method of mapping the topography of the ocean floor along a strip up to 60 km

Transform faults have all of the following characteristics except:

movement occurs in the same direction.

Segments of the oceanic ridge system that are gentler and less rugged in slope due to faster rates of seafloor spreading are called:

oceanic rises.

In comparison with other ocean basins, major sedimentary features such as continental rises and abyssal plains are relatively rare in the Pacific. The primary reason for their scarcity in the Pacific is that __________.

sediment is trapped within the trenches of the convergent plate boundaries ringing the Pacific

The two relatively flat areas on the hypsographic curve represent:

some interior continental areas/coastal plains and abyssal plains on the ocean floor.

Underwater avalanches of muddy water mixed with rocks and debris are:

turbidity currents.

precision-depth recorder (PDR)

uses high frequency sound waves to measure ocean depth

Nearly all oceanic islands are __________. (Choose the best answer.)

volcanic in origin