The Oceans Flashcards
The hydrosphere covers ___% of the Earth’s surface and is divided into ___ major oceans
71
5
Name Earth’s 5 oceans in order of increasing size
Arctic Antarctic Indian Atlantic Pacific
Compare the depth of the ocean to the height of the continents
The average depth of the ocean is 2.5 miles below sea level while the average height of the continents is 1/2 mile above sea level. The ocean is 7 miles deep in the Pac. Ocean’s Marianas Trench; Mt. Everest is only 5 mi high
What are the predominant elements and compounds in seawater?
Sodium chloride Magnesium chloride Magnesium sulfate Calcium sulfate Nitrogen Oxygen Carbon Dioxide
Salinity
The “saltiness” of the ocean water. Determined by the weight of salt present in a given weight of water. Five percent salinity means 100 lbs of water contains 5 pounds of dissolved salt
Is salinity the same everywhere in the ocean?
No. Fresh water entering the ocean reduces the salinity. High evaporation rates increase the salinity.
How is the ocean heated?
by the Sun
Where is the ocean warmer?
It is warmer near the equator and from the surface to a few hundred feet deep
Where is the ocean cooler?
Cooler farther from the Equator and closer to the poles of the Earth and at depths below a few hundred feet
How does the ocean affect the climate of land nearby?
Keeps climate more stable by reducing the temp in the summer and raising it in the winter. Summer cooling effect: water absorbs heat from the air, reducing the temp. Winter heating effect: water retains heat well and gives it off gradually to warm the air
Describe echo sounding
Current method of measuring the depth of the ocean. An echo sounder on a ship sends sound waves into the water. They bounce off the bottom of the ocean and reflect back to the machine. Scientists can calculate the distance the wave has traveled down to the bottom by measuring the time it takes to reflect back to the machine
Bathyscaphe (submersible)
Small sub that can take a person to the bottom of the ocean. (can also be remote control). It is equipped with scientific instruments to observe the landscape and living creatures at great ocean depths
Ocean basin
Depressions in the earth’s crust that contain the oceans. Lower than the continents because they are made of basalt, which is more dense than granite. They are only 8 km thick. Continents are about 40 km thick.
Approx. depth and description of continental shelf
The gently sloping edges of the continents that are under water at edge of oceans. Average 400 feet in depth.
Continental slope and approx. depth
The steeply sloping area beyond the continental shelf. May be from 10,000 to 30,000 feet deep
Underwater canyon
Same as a canyon on land; a groove cut in the Earth’s crust under the ocean
Ridge - what is the largest on earth?
Underwater mountain range. Marks the spreading plate boundary between west-moving N. American plate and E. moving European plate. The Mid-Atlantic ridge is largest on earth. About 10,000 miles long. Runs between Americas and African continent.
3 ways in which islands are formed
- peaks of underwater ridges rise above sea level
- tops of underwater volcanoes rise above the surface of the water (Canary Islands, Hawaii…)
- coral animals deposit lime and coral deposits on the top of underwater volcanoes; they eventually rise above the surface (Coral Islands, Barbados Terraces)
Trench
Deep valley in ocean floor. They are plate boundaries called subduction zones (one plate diving under another to join mantle). They can reach a depth of several miles; usually located near coastal mountain ranges (Marianas Trench, Guam)
Define ooze. What are some of the other sediments found on the ocean floor?
Sediment present in large quantities on the ocean floor. Consists of miscroscopic plant and animal remains
Other examples e.g. gravel, sand, mud, volcanic dust, particles from meterorites, lumps of metallic minerals, bones of sharkes, etc.
How is ocean wave produced?
Wind blows over top of water, causing ripples which become small waves (lger as wind blows harder). Tsunamis (tidal waves) are caused by submarine motions driven by earthquakes
Define a crest
the top peak of the wave
Define a trough
The bottom (valley) of the wave
Define wavelength in relation to ocean
Distance between two adjacent crests or troughs
Define amplitude as it relates to ocean
Height of wave measured from surface of water to crest or trough
Swells
Waves traveling away from their source appear as rounded peaks that rise and fall with a regular rhythm
Breakers
When a swell reaches shallow water, bottom of wave drags along bottom and slows. Top moves forward and eventually falls. Before wave reaches shallow water, its motion is circular. Waves washing up on beach are breakers
Undertow
A current produced as the water from a breaker flows back out to ocean
Surface current
Mass of water that flows in a given direction on surface of the ocean. Formed by wind motion. Wind motion large caused by differential heating of the Earth by the Sun
Subsurface Current
Caused by convection currents in water. Two masses of water of different density (due to variation in temp or salinity) move relative to each other. The denser water sinks and forces less dense water to rise
Ocean currents in the N. Hemisphere move in a _____ direction; in the Southern H. in a ____ direction. Why?
Clockwise
Counterclockwise
Caused by Coriolis effect. Spinning Earth causes an apparent change in current direction
Polar current
A subsurface current originating in the polar regions. Polar water is denser because it is cold and often has high salinity
Polar creep
Water from polar currents moves very slowly toward the Equator, taking years to reach it. Hence… polar “creep”
Drift
Shallow, wide mass of ocean water that moves more slowly than a current
Tide
Rise and fall of ocean as a whole in regular rhythm. Two factors: gravitational pull between Moon and Earth and tendency of the water on surface of rotating Earth to travel in a straight line away from the center
Sandbar
Deposits of sand are moved by waves and currents moving parallel to the shore
Offshore bar
Sandbar not connected to the mainland
Ex: Fire Island, NY
Lagoon
Water between an offshore bar and the mainland
Ex: Jamaica Bay, NYC
Compare spit to hook
Both sandbars formed by current flowing across a bay and away from shore. A spit is straight and parallel to the shore; a hook has the shape of a hook
Hook: Cape Cod, MA
Spit: Sandy Hook, NJ; Cape Hatteras
Sea cliff
Wave action erodes the bases of mountains or steep coastal land bordering on the ocean shore, forming cliffs that overhang the ocean
Estuary
River valley that has been flooded by rising sea level
Fjord
A valley formed by a glacier that is now below sea level
Desalination
Method to obtain fresh water by extracting salt. Can be done by freezing or evap.
How are the chemicals that contribute to ocean pollution picked up and deposited in the oceans?
Rainwater
Give examples of ocean pollution’s harmful effects
Contaminate the normally clean water in which algae thrive
The fish that depend on algae die as well
This affects local economies that depend on fishing
Toxic waste can be consumed by organisms low on the food change
Sometimes toxic waste can move up the food chain even to humans (are what you eat, etc)
Lead is good example
How does ozone depletion affect marine life?
Electromagnetic energy can penetrate depths to 20 meters. This radiation can cause cell damage in marine species especially in small species. This can continue throughout food chain and impact entire ecosystems.
How does coastal upwelling happen?
This occurs due to the combined effects of wind and Ekman transport. Wind often blows parallel to a coastline; Ekman transport causes warm surface water along shore to swing outward away from land. Then coastal upwelling happens when cooler water swells up from higher depths to replace the water moving away from the coast. The water that rises during coastal upwelling contains high levels of nutrients. Plants near the surface absorb these and experience population growth. Etc. etc.
Oceanic tides
The daily oscillations in sea level along coastlines
Two causes of tides
Gravitational force
Centripetal acceleration
Why is the attraction of the Moon more effective in tide formation than the Sun?
It is close
A landform associated with costal areas when large, high-energy waves attack coastlines during storms and abrade portions of a rock face, forming a usually steep cliff. The intensity of this effect is related to the durability of the material being eroded and the slope of the land surface
Sea cliff
Besides sea cliffs, name another wave erosion formed formations
wave cut platforms (truncated sea cliff with leveled surface)
When are beaches created?
When the portion of the platform closest to the sea is covered with sand or other grainy materials. These formations constantly being eroded away and reformed. Marine-built terrace (deposit of material transported by waves) often formed inland from beach
Live river and stream erosion, most wave erosion is accomplished by abrasion through ____
eroded materials like sand and gravel carried in the water
Re the ocean: what are the main factors in the rate of wave erosion?
energy of waves
strength of material shoreline composed of
Describe the basic process of a wave
Two processes: disturbing, restoring
Disturbing force drives water into pile or crest… water that makes up the crest comes from an adjacent section of water and therefore produces a depression or trough on nearby water ssurface
Then, gravity (restoring force) attempts to restore by forcing crest back down
Due to inertia the gravitational force presses water down below that level making another trough
Water displaced by this motion creates another crest, etc etc
When crest is higher than associatted trough the wave moves forward
Not water that moves but the wave
Velocity of a wave
The distance it moves during a specified period of time
Two main forces in seawater circulation
atmospheric winds
Coriolis effect
In North Hemisphere waters move ____, and waters in S. Hemisphere tend to move _____
eastward
westward
Gyres
The wide circular patterns through which air circulates in the atmosphere making warm surface waters travel from regions near equator toward cooler poles redistributing the heat within ocean
Ekman transport
Theory states that as each layer of oceanic water is touched by wind, it also experiences the effects of the Coriolis force which causes it to move 90 degrees to the right (left in Southern hemisphere) and spiral downward (Ekman spiral)
Ooze
Sediment that accumulates over time from fragments of deceased surface organisms
Calcareous ooze
Ooze made up mostly of the carbonate remains of organisms such as shells. Dissolves at depths below 4 km
Silliceous ooze
Ooze composed of remains of silica-cell producing organisms. More resistant to dissolution than carbonate material.
What is sediment at deepest layers of ocean mostly composed of?
inorganic clay and occassional fossils like sharks teeth
Coral reef
underwater formation composed mainly of coral and algae. Usually form in clear, warm water. Develop their own ecosystems.
Charles Darwin identified 3 types of coral reefs:
Fringing reef
Barrier reef
Atoll
Fringing reef
Begins to grow around sinking volcanic island
Barrier reef
What fringing reef becomes when the portion of reef closest to the shore cannot keep up with live growth of outer portion. Inner portion becomes lagoon
Atoll
What barrier reef becomes when the island sinks completely
Briefly define abyss floor, abyssal hills, ocean ridge system, and seamounts AND GUYOTS
- deepest level of seafloor (covered with basaltic floods or sediment also called plains)
- fairly gentle rises along floor of abyss
- high areas undersea like mountain chains
- basaltic seafloor volcanoes that are not tall enough to reach earth’s surfaces
- enormous undersea volcanoes whose apexes appear to have been shorn off creating nearly level underwater shelf
Submarine canyon
steep walled valley in continental slope
