Chapter 4: Marine Sediments

What have oceanographers determined from analyzing sea floor cores?

climate change and past extinctions

Two common types of chemical compounds found in biogenous sediments are __________ and __________.

calcium carbonate; silica

Where on the ocean floor do abyssal clays develop?

on the deep-ocean floor, far from land

What mechanism(s) is/are responsible for transporting clay to deep ocean basins?

slow-moving ocean currents; wind

Forams, which are composed of calcium carbonate, __________ above the CCD and __________ below the CCD.

do not dissolve; dissolve

Diatomaceous earth, which is composed of silica, __________ above the CCD and __________ below the CCD.

does not dissolve; does not dissolve

Which of the following statements about the calcite compensation depth (CCD) is correct?

Below the calcite compensation depth (CCD), physical conditions cause calcium carbonate to dissolve.

How does the analysis of forams in ocean sediment cores reveal climate change?

The presence and relative dominance of different species of forams reveal different global climate conditions.

Where do calcareous oozes exist on the seafloor?

Underneath areas where calcareous organisms live, above the CCD.

Which sediment below cannot accumulate below the CCD?

calcareous tests

What is the approximate depth of the calcite compensation depth (CCD) in the ocean?

3 miles (4.5 kilometers)

On average, at what ocean depth does calcite readily dissolve into seawater?

4500 meters (14,764 feet)

What did the discovery of tillite in South Africa reveal about southern Africa's past?

An ice sheet covered southern Africa 300 million years ago.

What is calcareous ooze composed of?

At least 30% the remains of calcareous organisms.

Why is this drilling process called rotary drilling?

Because the drill bit turns around in a circle.

Why does calcareous material dissolve below the CCD?

Below the CCD, weak acid is formed, which dissolves calcareous material.

Which of the following explains why calcareous ooze is sometimes found below the calcite compensation depth (CCD)?

Calcareous ooze can be deposited above the CCD and covered with other sediment, which protects it as the tectonic plate, and the ooze moves into deeper water.

Where is calcareous ooze most likely to be found in surface sediments in the ocean?

Calcareous ooze is most likely to be found in relatively shallow areas with warm surface water.

Why might ocean floors be better than continental locations for studying long-term changes in the size of ice sheets?

Continental records are fragmented and discontinuous, missing parts of the climate record.

Generally, what has been the pattern of global temperature change during the past 70 million years?

Earth's average temperature is approximately 15° cooler now than than it was 70 million years ago.

In which setting would calcareous ooze be most likely to form?

On the crest of a seamount under warm surface water.

How does siliceous ooze accumulate on the seafloor if silica-based residues are dissolved slowly at all depths?

Silica tests accumulate faster than seawater can dissolve them.

Why do some organisms thrive in warm surface waters?

Warm water is generally saturated in carbonate.

What factor primarily determines the distribution of radiolarian ooze?

areas of upwelling

Which of the following are examples of pelagic sediments?

biogenic ooze, abyssal clay; volcanic dust

Sediments derived from the remains of the hard parts of once-living organisms are called __________ sediments.

biogenous

Which of the following sediments would you expect to find in a lagoon?

broken bits of coral; salt

Where might one find calcareous oozes on the seafloor?

buried beneath siliceous oozes; buried beneath abyssal clay; along the crests of mid-ocean ridges, above the CCD

Which sediment type dominates in the neritic environment?

coarse lithogenous sediment, such as sand and small rocks

The tests from which of the following organisms will dissolve below the CCD?

coccolithophores; foraminifera

What sediment type(s) is/are included in the pink category labeled "Other" on the map?

cosmogenous sediments; hydrogenous sediments

The two major types of microscopic, planktonic organisms that produce siliceous oozes are __________ and __________.

diatoms; radiolarians

Which of the following organisms thrive in cold surface waters?

diatoms; siliceous organisms; radiolarians

Which of the following are examples of neritic sediments?

evaporite deposits; beach sand

What conditions exist below the CCD?

high carbon dioxide concentration; high acidity; cold temperature

Siliceous ooze is particularly abundant on the seafloor at __________ and at __________.

high latitudes; equatorial upwelling zones

What factor primarily controls the distribution of calcareous ooze?

water depth

Which of the following factors affect the distribution of biogenic oozes on the seafloor?

water depth; dissolution; biological productivity; seafloor spreading