Download to Ch. 14, 16 Notes

Geology Ch. 14 and 16 Notes – Oceans
Objectives:
1. Recognize that most of the Earth’s surface is covered by water.
2. List Earth’s four main ocean basins and identify their locations.
3. Describe the topography of the ocean floor and compare it to land.
4. Identify and describe three major technologies used to study the ocean floor.
5. List the three main regions of the ocean floor.
6. Differentiate between the continental margins of the Atlantic and Pacific oceans.
7. Explain the formation of new ocean floor at deep ocean trenches abyssal plains
and mid-ocean ridges.
8. Identify ocean resources used for energy production.
9. Explain how gas hydrates are formed.
10. List other types of ocean resources.
11. Recognize the factors that influence the density of ocean water.
12. Explain how surface currents develop.
13. Describe how ocean currents affect climate.
14. State the importance of upwelling.
15. Describe the formation of density currents
16. List the agents responsible for the movement of sediments along the shoreline
17. Describe the processes that form shoreline features
18. List the structures that can be built to protect a shoreline
14.1 The Vast World Ocean
The Blue Planet
 Nearly _____ percent of Earth’s surface is covered by the global ocean
 _______________is a science that draws on the methods and knowledge of
geology, chemistry, physics, and biology to study all aspects of the world ocean.
Geography of the Oceans
 The world ocean can be divided into four main ocean basins—the Pacific
Ocean, the Atlantic Ocean, the Indian Ocean, and the Arctic Ocean.
• The ___________is the largest and has the greatest depth.
• The _____________is about half the size of the Pacific and not quite as
deep.
• The____________, largely a southern hemisphere body, is slightly smaller
than the Atlantic.
• The _____________is about 7 percent of the size of the Pacific.
Mapping the Ocean Floor
 The topography of the ocean floor is as diverse as that of the continents.
 ________________is the measurement of ocean depths and the charting of the
shape or topography of the ocean floor.
 Today’s technology—particularly sonar, satellites, and submersibles—allows
scientists to study the ocean floor in a more efficient and precise manner than ever
before.
 Sonar
• ___________is an acronym for sound navigation and ranging. It is also
referred to as echo sounding.
• Sonar works by transmitting sound waves toward the ocean bottom.
 Satellites
• Satellites are able to measure small differences by bouncing
________________ off the ocean surface.
• Using this new technology, scientists have discovered that the ocean
surface is___________________________.
• Differences in the height of the ocean surface are caused by ocean-floor
features.
 Submersibles
• _______________are small underwater crafts used for deep-sea research.
• Today, many submersibles are unmanned and operated remotely by
computers. These remotely operated vehicles (ROVs) can remain underwater
for long periods.
14.2 Ocean Floor Features
 The ocean floor regions are the continental margins, the ocean basin floor, and
the mid-ocean ridge.
Continental Margins
 A ___________________is the zone of transition between a continent and the
adjacent ocean basin floor.
 In the Atlantic Ocean, thick layers of undisturbed sediment cover the
continental margin. This region has very little volcanic or ___________________
 In the Pacific Ocean, oceanic crust plunges beneath continental crust. This
force results in a narrow continental margin that experiences both volcanic
activity and _________________________
 Continental Shelf
• A ______________is the gently sloping submerged surface extending
from the shoreline.
• Continental shelves contain important mineral deposits, large reservoirs of
oil and natural gas, and huge sand and gravel deposits.
 Continental Slope
• A _________________is the steep gradient that leads to the deep-ocean
floor and marks the seaward edge of the continental shelf.
• A _______________is the seaward extension of a valley that was cut on
the continental shelf during a time when sea level was lower—a canyon
carved into the outer continental shelf, slope, and rise by turbidity
currents.
• A _________________is the downslope movement of dense, sedimentladen water created when sand and mud on the continental shelf and slope
are dislodged and thrown into suspension.
 Continental Rise
•
A ______________________is the gently sloping surface at the base
of the continental slope.
Ocean Basin Floor
 The ______________________is the area of the deep-ocean floor between the
continental margin and the oceanic ridge.
 Deep-Ocean Trenches
• Trenches form at the sites of plate _____________________where one
moving plate descends beneath another and plunges back into the
mantle.
 Abyssal Plains
• An ____________________is a very level area of the deep-ocean floor,
usually lying at the foot of the continental rise.
• The sediments that make up abyssal plains are carried there by turbidity
currents or are deposited as suspended sediment settles out.
 Seamounts and Guyots
• A ______________is an isolated volcanic peak that rises at least 1000 meters
above the deep-ocean floor, and a guyot is an eroded, submerged seamount.
Mid-Ocean Ridges
 A _______________is found near the center of most ocean basins. It is an
interconnected system of underwater mountains that have developed on newly formed
ocean crust.
 Seafloor Spreading
• _______________________is the process by which plate tectonics produces
new oceanic lithosphere at ocean ridges.
• New ocean floor is formed at mid-ocean ridges as magma rises between the
diverging plates and cools.
14.4 Resources from the Seafloor
Energy Resources
 Oil and natural gas are the main energy products currently being obtained from
the ocean floor.
 Gas Hydrates
• _________________are compact chemical structures made of water and
natural gas.
• Most oceanic __________________are created when bacteria break down
organic matter in ocean-floor sediments.
Other Resources
 Other major resources from the ocean floor include sand and gravel, evaporative salts,
and _______________________________
 Sand and Gravel
• The offshore sand-and-gravel industry is second in economic value only to the
_______________________industry.
 Manganese Nodules
• ________________________are hard lumps of manganese and other metals
(like cobalt, copper, and iron) that precipitate around a small object.
 Evaporative Salts
• When seawater evaporates, the salt increases in concentration until it can no
longer remain dissolved. When the concentration becomes high enough, the
salts precipitate out of solution and form _____________________________
• The most economically important salt is_____________—common table salt.
15.1 The Composition of Seawater
Salinity
 _____________is the total amount of solid material dissolved in water.
 Because the proportion of dissolved substances in seawater is such a
small number, oceanographers typically express salinity in parts per
thousands
 Most of the salt in seawater is________________, common table salt.
Salinity
 Sources of Sea Salt
• Chemical weathering of rocks on the continents is one source of
elements found in seawater.
• The second major source of elements found in seawater is from
Earth’s interior.
Ocean Temperature Variation
 The ocean’s surface water temperature varies with the amount of solar
radiation received, which is primarily a function of latitude.
 Temperature Variation with Depth
• The ____________is the layer of ocean water between about 300
meters and 1000 meters where there is a rapid change of
temperature with depth.
• The thermocline is a very important structure because it creates a
barrier to marine life.
Ocean Density Variation
 _____________is defined as mass per unit volume. It can be thought of
as a measure of how heavy something is for its size.
 Factors Affecting Seawater Density
• Seawater density is influenced by two main factors: salinity and
______________________________
16.1 The Composition of Seawater
Surface Circulation
 ____________is the mass of ocean water that flows from one place to another
 Surface Currents
• __________________are movements of water that flow horizontally in
the upper part of the ocean’s surface.
* Surface currents develop from friction between the ocean and the wind
that blows across its surface.
Surface Circulation
 Gyres
____________are huge circular-moving current systems that dominate the
surfaces of the oceans.
• The _________________is the deflection of currents away from their
original course as a result of Earth’s rotation.
 Ocean Currents and Climate
• When currents from low-latitude regions move into higher latitudes,
they transfer heat from ___________________areas on Earth.
• As cold water currents travel toward the equator, they help moderate the
warm temperatures of adjacent _________________________
 Upwelling
• _____________________is the rise of cold water from deeper layers to
replace warmer surface water.
• Upwelling brings greater concentrations of dissolved nutrients, such as
nitrates and phosphates, to the ocean _________________
Deep-Ocean Circulation
 Density Currents
• _________________________are vertical currents of ocean water that
result from density differences among water masses.
• An increase in seawater density can be caused by a decrease in
temperature or an increase in ______________________
 High Latitudes
• Most water involved in deep-ocean currents begins in high latitudes at
the surface.
 Evaporation
• ____________________can also result from increased salinity of ocean
water due to evaporation.
 A Conveyor Belt
• In a simplified model, ocean circulation is similar to a
_________________that travels from the Atlantic Ocean, through the
Indian and Pacific Oceans, and back again.
16.3 Shoreline Processes and Features
Forces Acting on the Shoreline
 A ____________is the accumulation of sediment found along the shore of a
lake or ocean.
 Waves along the shoreline are constantly eroding, transporting, and depositing
sediment. Many types of shoreline features can result from this activity.
Forces Acting on the Shoreline
 Wave Impact
• The impact of large, high-energy waves against the shore can be
awesome in its violence. Each breaking wave may hurl thousands of tons
of water against the land, sometimes causing the ground to ___________
 Abrasion
• __________is the sawing and grinding action of rock fragments in the
water.
• Abrasion is probably more intense in the surf zone than in any other
_________________
 Wave Refraction
• _________________is the bending of waves, and it plays an important
part in the shoreline process.
• Because of refraction, wave energy is concentrated against the sides and
ends of headlands that project into the water, whereas wave action is
weakened in _________________________
 Longshore Transport
• A ________________is a near-shore current that flows parallel to the
shore
• ___________________allows longshore currents to easily move fine
suspended sand and to roll larger sand and gravel particles along the
bottom
Erosional Features
 Shoreline features that originate primarily from the work of erosion are called
erosional features. Sediment that is transported along the shore and deposited in
areas where energy is low produces depositional features.
 Wave-Cut Cliffs and Platforms
• ______________result from the cutting action of the surf against the
base of coastal land. A flat, bench-like, wave-cut platform forms in front
of the wave-cut cliff.
 Sea Arches and Sea Stacks
• When two caves on opposite sides of a headland unite, a sea arch
results. Eventually, the arch falls in, leaving an isolated remnant, or sea
stack, on the ___________________________
Depositional Features
 Spits, Bars, and Tombolos
• Where longshore currents and other surf zone currents are active,
several features related to the movement of sediment along the shore may
develop.
- A __________is an elongated ridge of sand that projects from the land
into the mouth of an adjacent bay.
- A ____________bar is a sandbar that completely crosses a bay.
- A___________ is a ridge of sand that connects an island to the mainland
or to another island.
 Barrier Islands
• _____________are narrow sandbars parallel to, but separate from, the
coast at distances from 3 to 30 kilometers offshore.
Stabilizing the Shore
 Protective Structures
• Groins, breakwaters, and ______________are some structures built to
protect a coast from erosion or to prevent the movement of sand along a
beach.
 Beach Nourishment
• Beach nourishment is the addition of large quantities of _________to
the beach system.
Ch. 14 and 16 Definitions:
1. oceanography: the scientific study of the oceans and oceanic phenomena
2. bathymetry: the measurement of ocean depths and the charting of the shape or
topography of the ocean floor
3. sonar: an electronic depth-sounding mechanism, sonar calculates ocean depth by
recording the time it takes for an energy pulse to reach the ocean floor and return
4. submersible: a small underwater craft used for deep-sea research
5. continental margin: that portion of the seafloor adjacent to the continents; it may
include the continental shelf, continental slope, and continental rise.
6. continental shelf: the gently sloping submerged portion of the continental margin
7. continental slope: the steep gradient that leads to the deep-ocean floor and marks
the seaward edge of the continent
8. submarine canyon: a seaward extension of a valley that was cut on the continental
shelf during a time when sea level was lower; a canyon carved into the outer
continental shelf by turbidity currents
9. turbidity current: a downslope movement of dense, sediment laden water created
when sand and mud on the continental shelf are dislodged and thrown into
suspension
10. continental rise: the gently sloping surface at the base of the continental slope
11. ocean basin floor: area of the deep-ocean floor between the continental margin
and the oceanic ridge
12. abyssal plain: very level area of the deep-ocean floor, usually lying at the foot of a
continental rise
13. seamounts: an isolated volcanic peak that rises at least 1000 meters above the
deep-ocean floor
14. mid-ocean ridges: a continuous elevated zone on the floor of all major ocean
basins and varying in width from 1000 to 4000 km, associated with divergent
plate boundaries
15. seafloor spreading: the process by which plate tectonics creates new ocean floor at
ocean ridges
16. gas hydrates: a gas such as methane; trapped in a lattice-like structure of water
molecules
17. manganese nodules: rounded lump of hydrogenous sediment scattered on the
ocean floor, consisting mainly of manganese and iron with small amounts of
copper, nickel and cobalt
18. salinity: the proportion of dissolved salts to pure water, usually expressed in parts
per thousand
19. thermocline: a layer of water in which there is rapid change in temperature with
depth
20. density: mass per unit volume of a substance, usually expressed as grams per
cubic centimeter
21. ocean current: mass of ocean water that flows from one place to another
22. surface current: movement of water that flows horizontally in the upper part of the
ocean’s surface
23. gyre: the large circular surface current pattern found in each ocean
24. Coriolis Effect: the apparent deflection of winds and ocean currents due to the
rotation of the Earth. It deflects to the right in the Northern Hemisphere and the
left in the Southern hemisphere.
25. upwelling: the rising cold water from deeper layers to replace warmer surface
water that has been moved away
26. density current: current of ocean water that results from density differences
among water masses
27. beach: the accumulation of sediment found along the shore of a lake or an ocean
28. longshore current: a near-shore current that flows parallel to the shore
29. barrier islands: a low, elongated ridge of sand that parallels the coast