Chapter 3 Oceanography

A. abyssal hill B. abyssal plain D. seamount E. tablemount

C. submarine canyon

A. Turbidity currents B. Graded bedding C. Turbidite deposits E. Deep-sea fans

D. Abyssal plains

A. rift valley B. oceanic ridge C. oceanic rise E. seafloor spreading

D. seaknoll

What kinds of unusual life can be found associated with hydrothermal vents? how do these organisms survive

Hydrothermal vents are home to unusual deep-ocean ecosystems that include giant tube worms, large clams, beds of mussels, and many other creatures. These organisms are able to survive in the absence of sunlight because the vents discharge hydrogen sulfide gas, which is metabolized by Archaea (bacteria adapted to harsh conditions to provide a source of food for other organisms

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

True

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

abyssal plains

Sediments deposited by the process of suspension settling produce the main sediment found on

abyssal plains

Tablemounts

also called a guyot; sub-oceanic volcano with a flattened top that once existed about sea level

Describe how an echo sounder works

an echo sounder sends a signal from a ship downward into the ocean, where it produces echoes when it bounces off any density difference. 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

Seamounts

below sea level but rises more than 1 kilometer above the surrounding ocean floor, with a conical or pointy top like an upside-down ice cream cone that never reached the ocean surface

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 are turbidity currents

dense mixtures of sand, mud, and other debris that move at high speeds down submarine canyons

Oceanic ridges and rises result form seafloor spreading along:

divergent plate boundaries

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

false

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

false

Seamounts are 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

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 expect the:

fracture zone

Explain what graded bedding is and how it forms

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

What types of deposits do turbidity currents leave in alluvial fans

graded bedding that begins as coarse material and becomes finer upward

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

What would you look for as evidence that a rock layer formed from materials deposited by ancient turbidity currents

repeated sequences of graded bedding that begin as coarse material and become finer upward

Measurement of ocean floor bathymetry from satellites relies on

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

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

A ships 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

5,500 meters

Multi-beam sonar

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

Describe differences between transform faults and fracture zones

A transform fault is a seismically active are that shows evidence of pst transform fault activity. Two lithospheric plates are moving in opposite directions in a transform fault. A fracture zone, on the other hand, is a seismically inactive area that offsets the axis of a mid-ocean ridge. There is no relative motion because the lithospheric plates are moving in the same direction.

A. black smoker C. hydrothermal vent D. rift valley E. white smoker

B. Deep focus earthquake

A. Continental margin B. Active margin C. Convergent Active margin D. Transform active margin

E. Rift valley

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

How do turbidity currents affect canyons

Turbidity currents erode material from canyons as currents move downslope

Continental shelf

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

How often do turbidity currents occur

infrequently

Continental shelf

is a flat, gently sloping zone extending from the shore beneath the ocean surface to a point at which a marked increase in slope angle occurs

Submarine canyon

is a narrow, deep submarine valleys that are V-shaped in profile and have branches with steep to overhanging walls found on the continental shelf and slope

Continental rise

is a transition zone between the continental margin and the deep-ocean floor composed of a huge submerged pile of sediments

Deep sea fan

is deposits at the mouth of submarine canyons; create the continental rise when they merge along the base of the continental shelf

What process is involved in the formation of continental shelves

large fluctuations in sea level

Continental slope

lies beyond the shelf break, with a steeper incline, extending out to the deep-ocean basin

Transform faults have all of the following characteristics except:

movement occurs in the same direction

The majority of ocean trenches are associated with

narrow or no continental shelves

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

The method that used more frequently to investigate sediment and rock layers of the sea floor

sound waves (specifically seismic reflecting profiling)

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

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

true

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

Abyssal hills

volcanic features on the ocean floor are less than 1km; some of hte most abundant features on the planet that cover a large percentage of the entire ocean basin floor

Nearly all oceanic islands are

volcanic in origin