Chapter 3 Flashcards
What is the primary reason why sulfide mineral deposits on the ocean floor are not being mined?
No technology exists to retrieve them.
Reason: Recall that most of these deposits are found in the very deep ocean.
Manganese nodules are considered a valuable resource from the ocean floor because they are abundant and contain not only manganese but also ____.
cobalt; copper; nickel
Reason: Cobalt is considered “strategic” because it is needed to manufacture aircraft engines.
Why are scientists so interested in gas hydrates?
- They may play a significant role in slope collapse along continental margins.
- Scientists believe that they are extraterrestrial.
- They may play a role in climate change.
- They contain a tremendous amount of potential energy.
- They may play a significant role in slope along continental margins.
- They may play a role in climate change.
- They contain a tremendous amount of potential energy.
What are gas hydrates?
solid, icelike structures composed primarily of methane
Reason: Gas hydrates represent a tremendous amount of potential fuel resources.
The sediment and rock layers of the ____ floor provide us with information to understand how climate and life has changed through geologic time.
ocean or sea
____ 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.
Sulfide
Reason: Compounds of zinc, iron, copper, gold, and many others are formed in this manner.
Although offshore drilling is very ____, the resources are large enough to make the enterprise financially worthwhile.
expensive
Manganese nodules on the sea floor are a possible resource of many desirable metal resources. Where are these nodules found?
Scattered in many different types of locations, including across the world’s deep ocean floors
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
oil and gas
Reason: Oil and gas account for 95% of the value of all resources extracted from the sea floor or below.
Gas hydrates found on the sea floor contain a tremendous amount of ____, which is natural gas that can be used as an energy resource.
methane
____ is a seabed resource used to produce fertilizers.
Phosphorite
Gas ____ are solid, icelike structures composed primarily of methane that are formed in high-pressure locations such as the deep-ocean floor.
hydrates
Which of the following correctly describe sand and gravel resources found on the sea floor?
- Sand is mined as a source of metals.
- Sand and gravel is mostly mined for use in construction.
- The technology needed to mine sand and gravel from the shallow ocean floor is quite different from that used on land.
- Sand is mined as a source of metals.
Reason: Some of the metals found in sand include iron, tin, platinum, and gold. - Sand and gravel is mostly mined for use in construction.
The large-scale reasons that scientists are studying the layers of sediment and rock on the ocean floor are to ____.
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
What is the primary reason that we continue to drill for oil and gas in offshore fields?
The deposits are very large.
Seabed resource exploitation ____.
extends back to the time of ancient Greek civilizations
Of all seabed resources extracted from the sea floor or below, ____ represent more than 95% of the value.
oil and gas
A high ration of 18O:16O in marine organism shells preserved in ocean floor sediments indicates ____.
colder, glacier periods
Phosphorite is a seabed resource used ____>
to produce fertilizers
____ are atoms of the same element that have a different number of neutrons in the nucleus.
Isotopes
What resource is the most commonly sought after (in terms of volume) on the sea floor?
sand and gravel
The study of ocean basin history through the analysis of sediments is called ____.
paleoceanography
The sediment and rock layers of the ____ floor provide us with information to understand how climate and life has changed through geologic time.
ocean or sea
True or false: Seabed resource have only recently bee n exploited (beginning in the mid-1900s) because their mining required modern technological devices.
false
Reason: Seabed resource exploitation extends back to the time of ancient Greek civilizations.
What is the name of the process through which loose sediments on the sea floor are transformed into sedimentary rocks?
lithification
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?
certain ratios of oxygen reflect either warmer or cooler ocean temperatures
How is acoustic profiling used to study ocean-floor sediments?
Sound is bounced off and collected from the ocean floor, behaving differently for different layers.
Isotopes are atoms of ____ number of neutrons in the nucleus.
the same element that have a different
Which of the following devices would be best used to obtain a continuous and lengthy, undisturbed sediment sample from the sea floor?
corer
A person who studies the sediments of the oceans to recreate geologic history works in a field of study called ____.
paleoceanography
Which of the following describe where corse-grained sediments tend to be found on the sea floor?
in high-energy environments
close to their source areas
close to shore
The large-scale reasons that scientists are studying the laters of sediment and rock on the ocean floor are to ____.
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
Sandstone, shale, and limestone are ____ rocks formed on the sea floor.
sedimentary
What physical processes are involved in the process of lithification (i.e., turning sediment into rock)?
cementation; compaction; burial
____ profiling uses the behavior of sound reflected at the sea floor to study the different layers of ocean sediments.
Acoustic
What transportation agent is responsible for directly bringing large amounts of ash, sand, and clay particles up to 1000 km offshore?
wind
a net or basket dragged across the sea floor
dredge
hinged device that obtains a sample from a specific location on the sea floor
grab sampler
long barrel that obtains continuous and undisturbed sediment layers
corer
Glaciers and kelp are both responsible for transporting relatively large rock particles to the sea floor through the process of ____.
rafting
Fine-grained sediments on the sea floor dominate in areas farther away from their source and the shore because ____.
they are deposited in low-energy environments away from currents and waves
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
shale
sandstone
limestone
____ sediments are produced in the water through chemical reactions.
Hydrogenous
What is the name of the process through which loose sediments on the sea floor are transformed into sedimentary rocks?
lithification
found at cold and temperate latitudes
diatomaceous ooze
found beneath warm waters of equatorial latitudes
radiolarian ooze
Which of the following sources provide significant amounts of airborne sediment to the sea?
deltas; volcanic ash; sand dunes; deserts; rivers
volcanic ash; sand dunes; deserts
What happens to the majority of terrigenous sediments deposited on the continental margins?
They are moved seaward and down continental slopes by waves, currents, and turbidity flows.
Rafting is a form of sediment transport in the oceans that occurs as ____.
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
____ sediments are generally small particles that hit the ocean after surviving the trip from space through Earth’s atmosphere.
Cosmogenous
Which of the following describe where coarse-grained sediments tend to be found on the sea floor?
in high-energy environments; close to shore; close to their source areas
____ 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.
Manganese or Mn
Which of the following are ways in which hydrogenous sediments form?
Carbonates form by direct precipitation.
Sulfides form as hot, mineral-rich water from vents cools very quickly.
Diatomaceous ooze is located at ____ latitudes than radiolarian ooze is.
higher, temperate, cold, polar, or colder
What percent of marine sediment is terrigenous?
75%
In what type of water does dissolution of siliceous tests most readily occur?
warm, shallow water
Cosmogenous sediments are derived from ____.
space
Siliceous ____ originate from diatoms and radiolaria.
tests
Even though they are called manganese nodules, these deposits also contain high amounts of the metal ____.
iron
How does the carbonate compensation depth (CCD) affect accumulation of calcareous ooze on the ocean floor?
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.
____ sediments are produced in the water through chemical reactions.
Hydrogenous
Common in high latitudes
chlorite
More abundant in the tropics than in polar regions
kaolinite
comes from volcanic materials
Montmorillonite
More common in the Northern Hemisphere
Illite
The ____ is the depth in the ocean at which calcareous skeletal material first begins to dissolve.
lysocline
Reason: The prefix lyso- means to loosen or dissolve.
Dissolution of calcareous tests occurs in ____ ocean water, whereas dissolution of siliceous tests occurs in ____ ocean water.
deep, cold; warm shallow
Of the organisms listed that create calcareous tests, which is the smallest overall?
coccolithophores
Diatoms
Radiolarians
Phytoplankton
Zooplankton
Depending on the chemical composition of the tests within them, pelagic sediments with over 30% biogenous materials are known as either calcareous or siliceous ____.
ooze