Oceanography Study Guide- KEY 14-15
I. Ocean Floor
1. Define and describe:
a. continental shelf:




Undersea extension of a continent which can stretch for many miles out to sea.
Rich in natural resources and marine life.
Most commercial fishing takes place here.
Sunlight can reach the floor in many places.
b. abyssal plains:





Flat parts of the ocean and flattest parts of Earth.
They cover about 40% of the ocean floor.
Do not support much aquatic life because of a thick blanket of sediment that covers the area.
Found at ocean depths of over 6,500 feet.
Found in all major oceans but are more common in the Atlantic and Indian oceans.
c. pelagic division:

Open ocean waters
d. benthic division:

Area of the ocean nearest the ocean floor
2. Identify factors that limit our ability to explore the ocean floor:
 Darkness, since sunlight doesn't penetrate far below the surface.
 Water is cold, only a few degrees above freezing.
 There is tremendous pressure due to the mass of the water pushing down.
II. Salinity, Density and Pressure
1. Identify the 4 most abundant elements in seawater:
1.Hydrogen
3.Sodium
2. Oxygen
4. Chlorine
2. Describe how salinity and temperature affect density:
 Colder temperature=more density

Higher temperature=less density

Higher salinity=more density
3. Explain the relationship between depth temperature and pressure:
 The deeper you go, the colder it gets, as well as the pressure increases.
4. Salinity:
a. define:
•
Salinity is the measure of how much salt is in water
b. identify the average % of salt in sea water: 3.5 %
c. identify the % of Earth’s water that is salt water: 97 % percent is saltwater
d. identify the % of salinity of brackish water:
Brackish water is fresh and salt water mixed. The salinity is not as high as the 3.5%
found in ocean water
e. list two factors that cause salinity to decrease:
Salinity decreases
1. near the surface of the water as the dense salty water sinks
2. in places where fresh and salt water mix
III. Waves, Currents & Tides:
1. Define and describe:
a. wave: A forward motion of energy.
b. breakers: As breakers approach the shoreline, the water becomes shallow and the
bottom of the wave hits the ground. This causes the wave to slow down. When the
wave slows down it changes shape and “breaks” on the shore forming surf
c. tsunami: A giant wave usually caused by an earthquake beneath the ocean floor.
d. current: The movement of streams of water throughout the ocean are called currents.
There are three types of ocean currents: 1) surface, 2) deep, and 3) upwellings.
Deep water currents are caused by temperature and salinity.
Surface currents are caused by the force of winds and the rotation of the Earth.
e. surface currents: Currents that affect water to a depth of several hundred meters. They
are driven mainly by wind.
f. upwelling: Upwellings force nutrients from the ocean bottom up to the surface. Often
many schools of fish are found in these areas due to “easy” feeding grounds.
g. El Niño: An abnormal climate event that occurs every two to seven years in the Pacific
Ocean, causing changes in winds, currents and weather patterns for one to two years.
h. La Niña: A climate event in the eastern Pacific Ocean in which surface waters are
colder than normal.
i.
The Coreolis Effect: Currents in the Northern hemisphere move in a clockwise direction,
while currents in the southern hemisphere move in a counterclockwise direction. This
is known as the Coreolis effect.
j.
gyre: Large system of rotating ocean currents caused by the Coreolis Effect.
k. Tide: The regular rise and fall of sea level due to the moon’s gravitational pull on Earth.
2. Identify factors that affect waves:



The distance over which the wind blows
The strength of the wind
The length of time the wind blows
3. Be able to calculate tidal range for daily high and low tides.
 Subtract low tide from high tide.
4. Describe the differences between spring tides vs. neap tides. Draw a model of the position
of the sun, moon and Earth causing each.

Neap tide- The tides with the least difference between consecutive low and high
tides. Occurs during the first and third quarter moons.

Spring tide- The tides with the greatest difference between consecutive low and
high tides. Occurs during the new or full moon.
IV. Restore the Shore:
1. Describe overwash: Occurs when waves exceed the elevation of the dune and transport
the sand across the land.
2.Explain why there is less vegetation on a primary dune compared to a secondary dune:
The location of the vegetation on the primary dune is non-existent
on the ocean side of the dune, while on the side facing the secondary dune plant life
begins to grow because it is protected from the wind/ and salt spray of the ocean.
As you go further away from the harsh elements of the ocean plant life grows in
abundance.
3. Identify positives and negatives for each of these shore restoration techniques:
a. Jetties and Groins:
 Groins and jetties can be used to help restore the beaches.
 They are placed perpendicular to the beach to catch sand as it travels north
 However, they can cause erosion on the other side of the structure
b. Wooden fencing:
 Ideal for dune-building structures because it is inexpensive, readily available,
easy to handle, and can be erected quickly.
 However, can decompose easily and not attractive
c. Plastic fencing:


The advantage of being strong, durable, and reusable, and it won't be taken for
campfire fuel.
Plastic fencing, however, is about three times as expensive as wooden sand
fencing.
V. Wetlands:
1. Describe and list the benefits of wetlands: Land area covered with a shallow layer of water
during some or all of the months of the year. Some benefits of the wetlands are the following…




many migrating animals stop in wetlands to rest during their migration.
provides a protective haven for young animals
the spongy soil removes the pollution before the water moves on to the larger body of water
filter out sediments and pollutants that are carried by flowing water to the ocean.
2. Describe brackish water: Brackish water is fresh and salt water mixed. The salinity is not as
high as 3.5% found in ocean water.
3. Explain how salinity affects animals in estuaries:
Animals living in estuaries have trouble because sometimes throughout the year
salinity levels are very high, while different times in the same year salinity levels drop
and can become very low.
VI. Human Impact: Garbage Island
:
1. Identify a material that photodegrades? plastics
2. Explain what nurdles are and their impact on the environment.
Nurdles are small bits of plastic produced by photodegradation. Nurdles soak up toxic
chemicals. Over time, even chemicals or poisons that are widely diffused in water can
become highly concentrated as they're mopped up by nurdles. The animals then eat
the nurdles thinking they are food, either killing them or greatly affecting the food
chain/webs.
3.Describe why we have not been able to get rid of Garbage Island and what we can do to
try to stop it from getting larger.
The great size of the patch and it is constantly shifting. The pieces of small plastic
(nurdles) are hard to capture. We can stop using single-use disposable containers/bags
and use reusable bags/containers instead.