Chapter 8 (Chapter 6) Ocean Sediments

Refer to figure 3. Where would you find the highest rate of sedimentation of terrigenous particles?

A

The only river that discharges significant amounts of lithogenous sediment to either the Pacific or the Atlantic Oceans is the

Amazon.

Refer to figure 1. Where would you expect to find layers of sediment deposited by turbidity currents?

B: Point I

Refer to figure 3. Where would you find that the thickness of the sediments is LEAST?

C

Refer to figure 3. Where would you find the highest concentration of skeletons of marine organisms in the surface layer of the sediment?

C

Which of the following statements concerning calcareous particles from marine organisms' skeletal material is true?

Calcite parts are generally less soluble than aragonite parts.

Refer to figure 3. Where would you find there is NO calcium carbonate in the surface sediment?

D

Sediment particles are transported by ocean currents. Which of the following are true? Particles of all sizes sink at the same rate. Large particles are easily suspended by the currents on the deep ocean floor so they are not found in sediments deeper than the edge of the continental shelf. All types of fine-grained sediments that have accumulated on the seafloor are more easily resuspended by currents than are all types of large-grained sediments. none of the above

E: none of the above

True or False Cosmogenous sediment particles are always magnetic.

False

True or False Deep seafloor marine sediments typically have a high organic content from the accumulation of detritus.

False

True or False Manganese nodules grow quickly in areas with high sedimentation rates.

False

True or False Seawater is saturated with silica.

False

True or False The carbonate compensation depth (CCD) is deeper in the Pacific Ocean than in the Atlantic Ocean.

False

Wind-blown dust is transported over the North Pacific Ocean from the _____ desert.

Gobi

Extensive buried evaporite layers beneath the Mediterranean Sea indicate that the

Mediterranean Sea must have evaporated almost to dryness in the past.

Refer to figure 1. Where would you expect to find surface sediments that are calcareous oozes (sediments with more than 30% calcium carbonate skeletal material)? Point H Point E Point I Point A Point C

Point C

True or False Fine lithogenous sediment is continuously deposited on the ocean surface even far from the continents.

True

True or False Phosphorite nodules grow near zones of upwelling along continental margins.

True

True or False Volcanic ash from major eruptions can remain in the atmosphere for years.

True

Turbidity currents are

able to move large quantities of sediments down submarine canyons, usually triggered by earthquakes, and the reason that course-grained sediments can be found in some areas of the continental rise and abyssal plain.

Lithogenous sediments are often rich in silicate minerals because these minerals

are resistant to weathering.

Rivers that empty on subduction zone margins

are usually short and drain small regions.

The first salt to precipitate out as an evaporite when sea water is evaporated is

calcium and magnesium carbonate.

Calcium carbonate sedimentation rates on seamounts or oceanic plateaus can be an order of magnitude higher than in the deep ocean basins because

calcium carbonate dissolves more easily in deep water.

The carbonate compensation depth (CCD) depends on the concentration of _____ in the water.

carbon dioxide

Studying the fossils in deep ocean sediments and the sediment chemistry can provide information concerning

changes in climate over millions of years.

Changes in concentration of carbon dioxide in seawater regulate the carbonate compensation depth (CCD) by

changing the pH of the water.

Which of the following are phytoplankton that are covered by small calcareous plates?

coccolithophores

Which of the following is never the principle component of marine sediment?

cosmogenous particles

The carbonate compensation depth (CCD) is shallower in the Pacific than in the Atlantic because

deep Pacific Ocean water has a higher concentration of carbon dioxide.

Most glacial sediment is

deposited near the lower end of the glacier.

The siliceous phytoplankton in zones of upwelling and around Antarctica are dominated by

diatoms.

Which of the following is NOT a major mechanism of transport of lithogenous sediment to the oceans?

earthquakes

Much of the suspended sediment carried by rivers are deposited in _____ before reaching the open ocean.

estuaries

Most life on the deep seafloor sustains itself by

feeding on a constant rain of detritus from above.

Rivers transport primarily _____ particles to the oceans.

fine-grained

Fjords are

flooded glacial valleys.

Turbidite deposits can be identified by their

graded bedding.

Phosphorite nodules form

in some areas of the continental shelf and slope.

Calcium carbonate hydrogenous sediments form

in the Bahamas.

The second most abundant metal in manganese nodules is

iron.

Hydrothermal water leaches metal sulfides easily from the oceanic crust because

it has a low oxygen concentration and a high pH.

Which of these would you expect to find on the deep ocean floor at depths of 5000 m or more in areas at mid-latitudes and far from the continents?

muds of fine-grained terrestrial clays

Sediment lies everywhere on the deep seafloor except where

new seafloor is created during active volcanism.

Seawater is generally saturated with calcium carbonate only in

shallow, warm water.

Cosmogenous sedimentary particles are _____ spherical particles that show the effects of melting.

silicate and iron-rich

The major source of metals for manganese nodules is thought to be

small suspended particles from hydrothermal vents

Unlike the Pacific, the Atlantic Ocean does not have an equatorial band of radiolarian ooze because

the accumulation rate of lithogenous particles is much higher in the Atlantic.

The area with the highest known concentration of manganese nodules is

the deep Pacific Ocean north of the equator.

The two major factors that determine the accumulation rate of biogenous sediment are

the rates of production and dissolution of biogenous particles.

On the outer part of the American North Atlantic continental shelf, the surface sediments are coarse beach sands containing many shells of marine species, such as oysters, that live only in shallow water because

these sediments were deposited thousands of years ago during the peak of an ice age when more of the Earth's water was found in glaciers and the sea level was much lower.

Fecal pellets often increase the accumulation rate of biogenous sediments because

they sink rapidly and partially protect siliceous and calcareous particles from dissolution.

Large-grained sediments are transported down submarine canyons to the abyssal plain by

turbidity currents.

Most of the organisms that live in surface waters are

very small

Relict sediments on the continental shelf

were deposited when sea level was lower during ice ages.

Hydrothermal vent minerals form

when metal sulfides in the hot vent water are oxidized on contact with seawater.