Chapter 3

Question 1

What is the primary reason why sulfide mineral deposits on the ocean floor are not being mined?

Answer 1

No technology exists to retrieve them.

Reason: Recall that most of these deposits are found in the very deep ocean.

Question 2

Manganese nodules are considered a valuable resource from the ocean floor because they are abundant and contain not only manganese but also ____.

Answer 2

cobalt; copper; nickel

Reason: Cobalt is considered “strategic” because it is needed to manufacture aircraft engines.

Question 3

Why are scientists so interested in gas hydrates?

1. They may play a significant role in slope collapse along continental margins.
2. Scientists believe that they are extraterrestrial.
3. They may play a role in climate change.
4. They contain a tremendous amount of potential energy.

Answer 3

1. They may play a significant role in slope along continental margins.
2. They may play a role in climate change.
3. They contain a tremendous amount of potential energy.

Question 4

What are gas hydrates?

Answer 4

solid, icelike structures composed primarily of methane

Reason: Gas hydrates represent a tremendous amount of potential fuel resources.

Question 5

The sediment and rock layers of the ____ floor provide us with information to understand how climate and life has changed through geologic time.

Answer 5

ocean or sea

Question 6

____ minerals are formed on the ocean floor when hot seawater laden with minerals pours out from rifts and hits the cold ocean water, quickly precipitating the metals.

Answer 6

Sulfide

Reason: Compounds of zinc, iron, copper, gold, and many others are formed in this manner.

Question 7

Although offshore drilling is very ____, the resources are large enough to make the enterprise financially worthwhile.

Answer 7

expensive

Question 8

Manganese nodules on the sea floor are a possible resource of many desirable metal resources. Where are these nodules found?

Answer 8

Scattered in many different types of locations, including across the world’s deep ocean floors

Question 9

Which of the following represent the highest valued resources extracted from the sea floor or below?

sand and gravel
phosphorite and sulfide minerals
oil and gas

Answer 9

oil and gas

Reason: Oil and gas account for 95% of the value of all resources extracted from the sea floor or below.

Question 10

Gas hydrates found on the sea floor contain a tremendous amount of ____, which is natural gas that can be used as an energy resource.

Answer 10

methane

Question 11

____ is a seabed resource used to produce fertilizers.

Answer 11

Phosphorite

Question 12

Gas ____ are solid, icelike structures composed primarily of methane that are formed in high-pressure locations such as the deep-ocean floor.

Answer 12

hydrates

Question 13

Which of the following correctly describe sand and gravel resources found on the sea floor?

1. Sand is mined as a source of metals.
2. Sand and gravel is mostly mined for use in construction.
3. The technology needed to mine sand and gravel from the shallow ocean floor is quite different from that used on land.

Answer 13

1. Sand is mined as a source of metals.
   Reason: Some of the metals found in sand include iron, tin, platinum, and gold.
2. Sand and gravel is mostly mined for use in construction.

Question 14

The large-scale reasons that scientists are studying the layers of sediment and rock on the ocean floor are to ____.

Answer 14

discover how life-forms have evolved over geologic history
understand the formation of ocean basins and continents
find out how Earth’s climate has changed in the past

Question 15

What is the primary reason that we continue to drill for oil and gas in offshore fields?

Answer 15

The deposits are very large.

Question 16

Seabed resource exploitation ____.

Answer 16

extends back to the time of ancient Greek civilizations

Question 17

Of all seabed resources extracted from the sea floor or below, ____ represent more than 95% of the value.

Answer 17

oil and gas

Question 18

A high ration of 18O:16O in marine organism shells preserved in ocean floor sediments indicates ____.

Answer 18

colder, glacier periods

Question 19

Phosphorite is a seabed resource used ____>

Answer 19

to produce fertilizers

Question 20

____ are atoms of the same element that have a different number of neutrons in the nucleus.

Answer 20

Isotopes

Question 21

What resource is the most commonly sought after (in terms of volume) on the sea floor?

Answer 21

sand and gravel

Question 22

The study of ocean basin history through the analysis of sediments is called ____.

Answer 22

paleoceanography

Question 23

The sediment and rock layers of the ____ floor provide us with information to understand how climate and life has changed through geologic time.

Answer 23

ocean or sea

Question 24

True or false: Seabed resource have only recently bee n exploited (beginning in the mid-1900s) because their mining required modern technological devices.

Answer 24

false

Reason: Seabed resource exploitation extends back to the time of ancient Greek civilizations.

Question 25

What is the name of the process through which loose sediments on the sea floor are transformed into sedimentary rocks?

Answer 25

lithification

Question 26

Different types, or isotopes, of oxygen exist in the ocean and are incorporated into the skeletal fragments of animals. What can the ratio of preserved isotopes tell us about climate?

Answer 26

certain ratios of oxygen reflect either warmer or cooler ocean temperatures

Question 27

How is acoustic profiling used to study ocean-floor sediments?

Answer 27

Sound is bounced off and collected from the ocean floor, behaving differently for different layers.

Question 28

Isotopes are atoms of ____ number of neutrons in the nucleus.

Answer 28

the same element that have a different

Question 29

Which of the following devices would be best used to obtain a continuous and lengthy, undisturbed sediment sample from the sea floor?

Answer 29

corer

Question 30

A person who studies the sediments of the oceans to recreate geologic history works in a field of study called ____.

Answer 30

paleoceanography

Question 31

Which of the following describe where corse-grained sediments tend to be found on the sea floor?

Answer 31

in high-energy environments close to their source areas close to shore

Question 32

The large-scale reasons that scientists are studying the laters of sediment and rock on the ocean floor are to ____.

Answer 32

find out how Earth's climate has changed in the past understand the formation of ocean basins and continents discover how life-forms have evolved over geologic history

Question 33

Sandstone, shale, and limestone are ____ rocks formed on the sea floor.

Answer 33

sedimentary

Question 34

What physical processes are involved in the process of lithification (i.e., turning sediment into rock)?

Answer 34

cementation; compaction; burial

Question 35

____ profiling uses the behavior of sound reflected at the sea floor to study the different layers of ocean sediments.

Answer 35

Acoustic

Question 36

What transportation agent is responsible for directly bringing large amounts of ash, sand, and clay particles up to 1000 km offshore?

Answer 36

wind

Question 37

a net or basket dragged across the sea floor

Answer 37

dredge

Question 38

hinged device that obtains a sample from a specific location on the sea floor

Answer 38

grab sampler

Question 39

long barrel that obtains continuous and undisturbed sediment layers

Answer 39

corer

Question 40

Glaciers and kelp are both responsible for transporting relatively large rock particles to the sea floor through the process of ____.

Answer 40

rafting

Question 41

Fine-grained sediments on the sea floor dominate in areas farther away from their source and the shore because ____.

Answer 41

they are deposited in low-energy environments away from currents and waves

Question 42

``` Various sedimentary rocks are formed on the sea floor, and they record important details about their environments, such as water depth, current directions, and biological environments. Choose the sedimentary rocks from the list below. shale marble basalt sandstone limestone ```

Answer 42

shale sandstone limestone

Question 43

____ sediments are produced in the water through chemical reactions.

Answer 43

Hydrogenous

Question 44

What is the name of the process through which loose sediments on the sea floor are transformed into sedimentary rocks?

Answer 44

lithification

Question 45

found at cold and temperate latitudes

Answer 45

diatomaceous ooze

Question 46

found beneath warm waters of equatorial latitudes

Answer 46

radiolarian ooze

Question 47

Which of the following sources provide significant amounts of airborne sediment to the sea? deltas; volcanic ash; sand dunes; deserts; rivers

Answer 47

volcanic ash; sand dunes; deserts

Question 48

What happens to the majority of terrigenous sediments deposited on the continental margins?

Answer 48

They are moved seaward and down continental slopes by waves, currents, and turbidity flows.

Question 49

Rafting is a form of sediment transport in the oceans that occurs as ____.

Answer 49

land-based glaciers become floating icebergs and drop out sediment that was incorporated into the ice when it was previously formed on land; large kelp that was attached to rocks breaks off, gets blown out to sea, and brings the rock along with it

Question 50

____ sediments are generally small particles that hit the ocean after surviving the trip from space through Earth's atmosphere.

Answer 50

Cosmogenous

Question 51

Which of the following describe where coarse-grained sediments tend to be found on the sea floor?

Answer 51

in high-energy environments; close to shore; close to their source areas

Question 52

____ nodules are named after the mineral that is dominant within these rounded masses. They also contain high amounts of iron, copper, cobalt, and nickel. Most grow very slowly and often around a piece of bone or tooth.

Answer 52

Manganese or Mn

Question 53

Which of the following are ways in which hydrogenous sediments form?

Answer 53

Carbonates form by direct precipitation. | Sulfides form as hot, mineral-rich water from vents cools very quickly.

Question 54

Diatomaceous ooze is located at ____ latitudes than radiolarian ooze is.

Answer 54

higher, temperate, cold, polar, or colder

Question 55

What percent of marine sediment is terrigenous?

Answer 55

75%

Question 56

In what type of water does dissolution of siliceous tests most readily occur?

Answer 56

warm, shallow water

Question 57

Cosmogenous sediments are derived from ____.

Answer 57

space

Question 58

Siliceous ____ originate from diatoms and radiolaria.

Answer 58

tests

Question 59

Even though they are called manganese nodules, these deposits also contain high amounts of the metal ____.

Answer 59

iron

Question 60

How does the carbonate compensation depth (CCD) affect accumulation of calcareous ooze on the ocean floor?

Answer 60

Ooze accumulates at depths above the CCD. Ooze does not accumulate at depths below the CCD. Reason: Below the CCD, dissolution of calcium carbonate dominates, so the material is not deposited on the ocean floor in the form of ooze.

Question 61

____ sediments are produced in the water through chemical reactions.

Answer 61

Hydrogenous

Question 62

Common in high latitudes

Answer 62

chlorite

Question 63

More abundant in the tropics than in polar regions

Answer 63

kaolinite

Question 64

comes from volcanic materials

Answer 64

Montmorillonite

Question 65

More common in the Northern Hemisphere

Answer 65

Illite

Question 66

The ____ is the depth in the ocean at which calcareous skeletal material first begins to dissolve.

Answer 66

lysocline | Reason: The prefix lyso- means to loosen or dissolve.

Question 67

Dissolution of calcareous tests occurs in ____ ocean water, whereas dissolution of siliceous tests occurs in ____ ocean water.

Answer 67

deep, cold; warm shallow

Question 68

Of the organisms listed that create calcareous tests, which is the smallest overall?

Answer 68

coccolithophores

Question 69

Diatoms Radiolarians

Answer 69

Phytoplankton Zooplankton

Question 70

Depending on the chemical composition of the tests within them, pelagic sediments with over 30% biogenous materials are known as either calcareous or siliceous ____.

Answer 70

ooze