Download OCEANS: EARTH`S LAST FRONTIER

OCEANS:
EARTH'S LAST
FRONTIER
1 videocassette. . . . . . . . . . . . . . . 25 minutes
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Rainbow Educational Media
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CREDITS
Author and Producer:
Director of Photography:
Graphics and Animation:
Production Coordinator:
Narrators:
Peter Cochran
Peter Scheer
Roger Meyer
Kathy Kavanaugh
Richard Cassell
Randye Kaye
Consultant: Michael Worosz
Stock Video: Encyclopaedia Britannica
European Space Agency
Georgia Dept. of Natural Resources
Jason Foundation for Education
Kaw Valley Films
NASA
National Park Service
Newport News Shipbuilders
Photo Researchers, Inc.
Scripps Institution of Oceanography
Woods Hole Oceanographic Institution
Post-Production: North Country Media
Audio Sweetening: Acme Recording Studios
Our appreciation to: Coastal Ecology Learning Program
(C.E.L.P.)
Caumsett State Park
Produced for Rainbow Educational Media by
Cochran Communications
TABLE OF CONTENTS
Introduction .......................................................................1
Program Summary ............................................................1
Objectives ..........................................................................4
Review Questions .............................................................5
Activities............................................................................7
Glossary .............................................................................9
Bibliography..................................................................... 12
Related Videos from Rainbow.........................................12
Script ...............................................................................13
INTRODUCTION
Covering more than 70% of the earth's surface and containing
95% of its water, the oceans are the dominant feature of our planet.
They are also the least explored. For most of human history, we
have had little knowledge about what exists below the ocean
surface. However, with the development of sophisticated
research tools such as submersibles and satellites, we have
recently learned a great deal more about the oceans and how they
affect the earth's ecology. This video program provides viewers
with a tour of the basic features of the oceans; including the
topography of the ocean floor, examples of different types of
marine life and the properties of waves, currents and tides.
The video uses a variety of techniques to be both informative and
entertaining. The narration alternates between male and female
narrators. Computer graphics clarify key points. Colorful footage
provides views of unusual marine life. Portions of the program
show students doing a variety of activities and experiments to
illustrate important concepts. Many of these experiments and
demonstrations students themselves can perform, either in class or
at home. In this way, the video promotes active participation in
the scientific process.
The video is designed to be used by students in grades four
through seven, but younger and older students can use it effectively as well.
SUMMARY
The video states that the earth is unique among the planets
because it is covered mostly by water. In spite of the predominance of the oceans, however, they are the earth's last frontier,
the part of our world that remains largely unexplored.
The program shows how scientists are busy finding out more
about what goes on in the oceans, but argues that it is not necessary
to be a scientist to explore them. The scene shifts to the
schooner Phoenix, part of the Coastal Ecology Learning Program
on Long Island Sound. The video shows students aboard the
Phoenix measuring the salinity of seawater, and the captain
describes the major source of this salt: dissolved solids from
rocks, carried by rivers to the sea.
Next the program shows the students pulling in a net and examining marine life that lives on the ocean bottom. The video draws
distinctions among three types of life found in the oceans: benthos, bottom dwellers; nekton, the free swimmers; and plankton,
floaters and drifters. It shows students aboard the Phoenix examining plankton and explains the importance of phytoplankton,
which produce the major share of the earth's oxygen. It also
describes the importance of plankton as the source of food for
many other kinds of life.
The next section of the program looks at differences in light,
temperature and pressure, at different ocean depths. The top
layer gets the most light and heat. For these reasons, it is here
that most life in the oceans exists. As you go deeper into the
ocean, the temperature drops quickly and there are fewer living
things. In the deepest layer, the temperature is uniformly cold
and there is no light from the sun. Even here, however, there is
some life.
The program also talks about how pressure increases with depth. It
shows a student doing an experiment that illustrates that. She puts
three holes in a milk carton at different levels and then fills the
carton with water. Differences in the resulting streams of water
coming from the holes indicate differences in pressure.
Then the video shows how submersibles like the Alvin are able to
resist great pressure, allowing humans to explore depths that were
once beyond their reach.
The next segment examines the topography of the ocean floor.
The shallowest parts of the oceans are the continental shelves that
stretch out from the continents in a gentle slope. The video shows
students using a net to gather samples of marine life along the
continental shelf off Long Island, New York.
Graphics show that when the shelf reaches the continental slope,
the ocean bottom drops off sharply. In some places, particularly in
the Pacific, deep trenches parallel the continental slope. Trenches
are formed when plates that form the earth's crust collide and one
plate slips under another. The program also shows how mountain
ranges, called rifts, form when plates move apart on the ocean
floor. Here, magma from deep within the earth seeps out to form
new crust.
Shots of tube worms that feed on sulfur-eating bacteria on rifts
show unusual marine life that are the only known living things
that don't directly or indirectly depend on photosynthesis to survive.
The video then returns to things about the ocean that we can
observe on its surface. It describes how waves form and move. A
student performs an experiment that shows that waves move
water up and down but not forward. Next, video footage and
graphics explain how the moon's gravity causes tides. Finally, the
program describes currents and the effects of currents on weather.
A brief summary concludes the video.
LEARNING OBJECTIVES
After viewing the program, students will be able to:
1. describe different geological features of the oceans,
including:
continental shelf
continental slope
trenches mid-ocean
ridges
2. describe different life forms that exist in different
parts of the ocean.
3. explain in simple terms the chemistry of seawater.
4. describe differences in light, temperature and
pressure at different ocean depths.
5. explain what waves are and how they move.
6. explain how tides function.
7. explain how different kinds of currents function and
the effects of currents on climate.
8. describe how the development of submersibles and
other forms of technology has advanced our
understanding of the oceans.
REVIEW QUESTIONS
1. Why is the earth called "the blue planet"?
Because the earth's most distinguishing characteristic is its
oceans.
2. How is ocean water different from fresh water?
Ocean water contains much more salt, on average about 35 parts
per thousand parts of seawater.
3. Why can't you drink ocean water?
The salt in ocean water robs your cells of water, causing them to
dry out.
4. What are the three main groups of marine life described in
the video and how are they different? Give some examples of
each.
Benthos are things that live on the ocean floor. Horseshoe crabs
are the example in the video. Encourage students to think of
others.
Nekton are things that swim freely through the water. Fish, turtles,
whales and dolphins are examples.
Plankton are plants and animals that float or drift in the water.
Phytoplankton are plant plankton and zooplankton are animal
plankton.
5. Why are phytoplankton important to the survival of other
things that live on earth?
Phytoplankton, through photosynthesis, produce most of the
earth's atmospheric oxygen. They are also an important source of
food for zooplankton, which in turn are eaten by other living
things.
6. What are several ways that the oceans change the deeper you
go?
As you descend from the surface, light disappears. Pressure
increases. It gets colder.
7. What are some of the geological features of the ocean bottom?
The continental shelf, the shallowest part of the ocean bottom,
slopes gently from the continents.
The continental slope, drops off sharply from the continental shelf.
Trenches, deep canyons exist where two plates of the earth's
crust collide.
Mid-ocean ridges, mountain ranges, form where plates move
apart and magma from deep within the earth spills out onto the
ocean floor.
8. What causes tides?
Gravity from the moon causes tides.
9. How do currents affect the earth's weather? Currents such
as the Gulf Stream warm the air above it.
Water from the oceans evaporates and is carried by winds
across the land where it condenses and forms rain.
ACTIVITIES
1. A sea is a large body of saltwater that is nearly surrounded by
land. Seas are part of the world's oceans.
Ask students to locate on a globe or map the earth's major seas:
Aegean Sea Coral Sea
Sea of Marmara
Arabian Sea Irish Sea
Red Sea
Bismark Sea Sea of Japan White Sea
Black Sea
Java Sea
Yellow Sea
2. Winds are not the only things that cause waves. They can also
be caused by underwater disturbances such as earthquakes. Large
surface waves caused by such disturbances are called tsunamis. A
tsunami can be as high as 32 meters (105 feet) and travel
thousands of miles.
Ask students to research and report on tsunamis and the damage
they cause.
3. Oceanography is the study of the ocean. Historians consider
Matthew Maury of the United States Navy the founder of
oceanography because of the information he gathered and published on ocean currents, temperatures and winds from 1842 to
1861. From 1872 until 1876, scientists aboard the British ship
Challenger were the first to make detailed studies of the ocean
bottom. In this century, important contributions have been made
as a result of scientists' working aboard surface research vessels
like the Glomar Challenger and submersibles like the Alvin.
Increasingly, satellites and underwater robots also play an
important role in ocean research.
Ask students to research and report on the history of oceanography.
4. Students interested in finding out more about careers in
oceanography can write to:
National Oceanography Association
1900 L Street, N.W. Washington, D.C.
20036
U.S. Naval Oceanographic Society
Washington, D.C. 20390
5. If you live near the ocean, there are many organizations that
will take students out on excursions to perform investigations
similar to those performed aboard the Phoenix in the video. Such
trips are most profitable when students prepare beforehand by
studying what they will be observing, such as plankton.
6. If you don't live near the ocean, specimens of marine life can
be ordered from a variety of sources, including:
Carolina Biological Supply
Eastern U.S.: 1-800-334-5551
Western U.S: 1-800-547-1733
Science Kit and Boreal Laboratories 1800-828-7777
Wards Natural Science Establishment 1800-962-2660
If you order live specimens, you will need an all-glass saltwater
aquarium, filters, an air pump, tubing and other things. Carolina
Biological sells a basic tank kit.
7. The video describes how, on average, there are 35 parts of salt
in every thousand parts of seawater. If you live near the oceans,
obtain a sample of seawater. Then have the students put the
seawater in a shallow dish and leave the dish outside or on a
window ledge that gets a lot of sun. After the water has evaporated, ask the students to describe what is left in the dish.
You can also have students do an experiment where they add salt
to tap water in a dish. Have them leave this dish and another dish
with plain water in a sunny place. After the water has evaporated
from both dishes, have the students describe what they see.
8. Each student can choose a different form of marine life to
research and report on. The report should include information
about the distinguishing characteristics of the plant or animal,
where in the ocean it lives and how it gets its energy. Students
could then present their reports orally to the whole class. They
could also make posters and other visual displays.
GLOSSARY benthos:
organisms that live on the ocean bottom
bioluminescence: emission of visible light by living
organisms
chloroplast: chlorophyll-containing organelle in plants
where photosynthesis takes place
continental shelf: shallow part of ocean floor next to a
continent
continental slope: steep section of ocean floor that
stretches from the continental shelf to the ocean basin
current: river of water that flows through an ocean
diatom: kind of phytoplankton
magma: liquid rock
mid-ocean ridge: long, underwater mountain range
nekton: marine organisms that can swim freely
photosynthesis: process by which plants use energy from
the sun, water and carbon dioxide to produce sugar and
oxygen
phytoplankton: tiny plants that float in the ocean
plankton: aquatic organisms that drift, float or swim feebly
plates: parts into which the crust of the earth is divided
pressure: force acting on something
salinity: measure of the amount of salt in seawater, usually
given in parts of salt per thousand parts of seawater
sea: large body of salt water nearly surrounded by land
sonar: system of transmitting underwater sound waves and
receiving the reflected waves to determine the depth of
ocean floor
submersible: research vessel designed to go to deep
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depths of the oceans
tide: rising and falling of water levels along the coast
trench: deep valley in ocean floor where two plates collide
zooplankton: tiny animals that float, drift or swim feebly
in the ocean
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BIBLIOGRAPHY
Carson, Rachel. The Sea Around Us. New York; Oxford
University Press, 1961.
Doris, Ellen. Marine Biology. New York; Thames and Hudson, 1993.
ReVelle, Penelope and ReVelle, Charles. The Environment: Issues
and Choices for Society. Boston; Jones and Bartlett Publishers, 1988.
Ronan, Colin A., General Editor. Science Explained. New York;
Henry Holt and Company, 1993.
The Ocean Unfolds. New York; Van Dam Publishers, Inc.
Thorndike, Joseph J., Jr., ed. Mysteries of the Deep. New York;
American Heritage Publishing Co., 1980.
Weiner, Jonathan. Planet Earth. New York; Bantam Books, 1986.
Whipple, A.B.C. Restless Oceans. Alexandria, VA.; Time-Life
Books, 1983.
Williams, Brian. The Sea. New York; Kingfisher Books, 1991.
RELATED VIDEOS FROM RAINBOW
Continents Adrift: An Introduction to Continental
Drift & Plate Tectonics
Earthquakes: Our Restless Planet Our
Changing Earth
Source of Life: Water in Our Environment Volcanoes:
Mountains of Fire What's Inside The Earth?: An
Introduction to The
Earth's Interior, Crust and Mineral Resources
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SCRIPT
Male Narrator:
There are places on earth where mountain ranges stretch
much farther than the Rockies,
and where there are trenches several times deeper than the
Grand Canyon.
There are places never seen by human eyes where lava spills
out of cracks in the earth's crust,
and where there are animals, only recently discovered, as
strange and wonderful as any found in a zoo.
We know more about the surface and features of the moon
than we do about most of these places,
because they remain largely unexplored - under the surface
of the oceans, the earth's last frontier.
Title: Oceans: Earth's Last Frontier
Female Narrator:
The earth is often called the blue planet because its most
distinguishing characteristic is not its continents but its
oceans.
One ocean alone, the Pacific, could fit all the continents
within its borders and still have room to spare.
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Besides the Pacific, there are four other oceans - the
Atlantic, the Indian, the Arctic and the Antarctic. Together,
these oceans and some smaller seas form one huge body of
water that covers over 70% of our planet's surface and
contains 97% of its water.
Yet, for much of human history people viewed the oceans
as mainly boundaries marking the edges of the continents.
For the most part, people could only imagine what secrets
were contained in the ocean depths.
Male Narrator:
Today, the oceans are revealing many of their secrets as
scientists use sophisticated tools to explore below the ocean
surface,
to analyze the properties of waves and currents,
and to find out more about what kinds of life live in the
oceans.
But you don't have to be a scientist to explore the oceans.
Each summer, for example, thousands of students from
New York and Connecticut have a chance to study Long
Island Sound aboard the schooner Phoenix.
The Phoenix belongs to a program called C.E.L.P., or
Coastal Ecology Learning Program.
Under captain Dennis Watson and his crew, students per-
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form a variety of activities that help them learn more about
ocean ecology.
One thing they investigate is the chemistry of ocean water
and how it is different from fresh water.
A student lowers a probe that measures the salinity, or salt
content, of the Sound's water.
Instructor:
Turn this to where it says salinity... and read the red numbers.
Male Narrator (contd.)
On average, there are 35 parts of salt per thousand parts of
ocean water. That may not seem like much, but it is enough
to make this water undrinkable for humans.
Captain Watson explains why.
Captain Watson:
Salt water is something the fish like, but we can't drink it. If
you drink salt water, you actually get thirstier. It's a dehydrating
agent that will actually rob water from the cells of your body,
making the situation worse. You will die quicker drinking salty
water than if you don't drink water at all.
Salt water came into the ocean from the land. As water runs
over the rocks it actually leaches out salt and miner-
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ah from the rocks thereby depositing it in solution in the
ocean.
Female Narrator:
Animals and plants that live in the ocean either have special
cells that aren't affected by salt or have ways of ridding their
bodies of salt.
To see some things that live in the ocean, the Phoenix drags
a net along the bottom of Long Island Sound.
The students then help pull in the net.
Students:
Horseshoe crab!
Instructor:
O.K. Everybody agree it's a horseshoe crab? It's got two
names - horseshoe crab, known also as a king crab. He's
really feisty, this guy. There's no stinger on the tail or anything, but say you were walking along the bottom and
accidentally stepped on him. Look at these burrs on his
carapace - that would feel like a sting, wouldn't it? Also on
the tail, look how the burrs go up. So, if you were to step
down, you'd end up with a nice laceration.
Female Narrator (contd.)
Horseshoe crabs and all other kinds of animals that live on
the ocean bottom are members of a group called benthos.
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The bottom is called the benthic layer of the ocean.
Another group of marine organisms are called nekton.
These swim freely through the water. Among the nekton
are thousands of different species of fish,
sea turtles,
and mammals like whales and dolphin.
Male Narrator:
A third group that lives in the oceans are plankton, living
things that simply float or drift wherever the waves or
currents take them.
Many kinds of plankton are plants and animals, too small to
be seen by the naked eye.
But they can be gathered using special plankton nets. This
jar of water contains thousands of plankton.
With the help of a microscope, you can see an incredible
diversity of these tiny ocean-dwellers.
Some are called phytoplankton. Phytoplankton are plant
plankton. The most abundant are diatoms whose unusual
shapes come from the glass boxes in which their cells are
encased.
Looking like Christmas ornaments, diatoms come in a
variety of shapes.
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Phytoplankton get their green color from structures inside
their cells called chloroplasts. Chloroplasts are responsible
for photosynthesis, the process by which plants produce
oxygen.
Phytoplankton produce more oxygen than all the earth's trees
and forests combined. In fact, over half the oxygen in the
earth's atmosphere was made by phytoplankton floating on or
near the surface of the oceans. Without this oxygen, life as
we know it couldn't exist.
Phytoplankton are important for other reasons. They are
the main food for animal plankton, or zooplankton.
The zooplankton in turn are eaten by many other kinds of
marine animals, from tiny fish to baleen whales.
Without plankton, most kinds of marine life would starve
and become extinct.
Female Narrator:
Plankton and most other kinds of marine life exist in the
top layer of the water, within a few meters of its surface.
This layer gets the most light and heat from the sun.
But light from the sun's rays decreases rapidly as you go
deeper into the ocean water.
Most of the ocean, in fact, is totally dark.
As you descend into the ocean, the water temperature also
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becomes colder.
And there is another change that occurs the deeper into the
ocean you go. The pressure of the water increases rapidly
with depth.
Male Narrator:
A simple experiment demonstrates the effects of water depth
on pressure.
Poke three holes in the side of a milk carton; one near the
top, one halfway down, and the third near the bottom.
Fill the carton with water and observe the streams of water
that escape.
The stream at the bottom is the strongest because there is
greater water pressure at the bottom of the carton than at
the top.
Pressure is measured in pounds per square inch. Standing on
land at sea level, each square inch of a person's body is
being pressed by about 15 pounds of air.
At 5 meters, or about 16 feet, below the ocean's surface, the
pressure from the weight of the water is much greater enough to make a diver's ears begin to hurt.
Scuba divers can swim to depths of only about 75 meters, or
about 245 feet. Beyond this depth, the pressure would
squeeze against the divers so hard that it would be difficult
for them to breathe.
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Most submarines dive to only 465 meters, or about 1,500
feet. Much beyond this depth the pressure would be great
enough to crush a submarine's hull.
Female Narrator:
There are, however, special submarines, called submersibles, that are designed to resist great pressure. This is
the Alvin, owned and operated by the Woods Hole
Oceanographic Institute in Massachusetts.
The Alvin is used to explore to depths as great as 4,000
meters, over 13,000 feet.
Submersibles like the Alvin have allowed humans to explore
areas of the ocean depths that were previously unreachable.
One of the things they found is that even here life exists, like
this lantern fish, whose soft flexible skeleton can resist great
pressure. Like many deep water fish, the lantern fish is
bioluminescent, which means that its body contains
chemicals that give off light.
Male Narrator:
The flatness of the ocean surface is broken only by waves.
But the surface disguises features that are as diverse as those
found on land.
Scientists have been able to map the ocean bottom using
sonar. A sonar device on a ship sends sound waves
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through the water.
These sound waves bounce off the ocean bottom and back to
the boat. By measuring how long it takes for the sound
waves to return, researchers can tell how deep the ocean is.
Satellites provide another way to study the ocean bottom.
Using computers, scientists can analyze measurements made
by satellites of the height of the ocean surface.
These measurements indicate bumps on the surface caused
by mountains on the sea floor.
Valleys and canyons, on the other hand, cause slight
depressions on the ocean surface.
Using information from satellites and sonar soundings,
researchers have drawn maps of the ocean bottom. This
computer-generated image shows what the Earth would look
like if its oceans were drained of water.
Female Narrator:
The part of the ocean floor with which we are most familiar is
the continental shelf. The continental shelf is part of a
continent that is under water. It extends out from the shore in
a gentle slope.
This is one part of the ocean that you can partly explore on
foot by wading out into the water, as these students are
21
doing at Caumsett State Park on Long Island, New York.
Along the continental shelf there is an abundance of sea life,
for here the water is shallow and gets a lot of light.
By dragging a net carefully through the water, you can see
some of the kinds of marine life that live close to shore.
The catch here includes tiny hermit crabs and baby flounder.
Male Narrator:
At the end of the continental shelf, the ocean bottom drops
off sharply. This part is called the continental slope.
Beyond the slope are large flat areas of the ocean floor that
are called the abyssal plain.
However, in some places, particularly the Pacific, the continental slope ends in a deep trench. Scientists believe that
the earth's surface is made up of large plates or sections of
rock that are constantly moving. Trenches are formed when
two plates collide and one moves under the other.
Some trenches are thousands of kilometers long and are the
deepest places in the oceans. The deepest trench of all is the
Manannas Trench in the western Pacific. In places it reaches
a depth of more than 11,000 meters, or about 36,000 feet
below the ocean surface.
From its lip to its bottom, the Manannas Trench is several
22
times deeper than the Grand Canyon.
Female Narrator:
Along the ocean bottom there are also long mountain
ranges called mid-ocean ridges. The Mid-Atlantic Ridge
stretches down the middle of the Atlantic Ocean and is only
one part of a ridge that winds its way around the earth.
Ridges are formed where two ocean plates are moving
apart.
Here, magma - or hot liquid rock - from deep within the
earth seeps out between the plates and then cools to form
new crust.
Near mid-ocean ridges, the Alvin has found hydrothermal
vents - cracks in the ocean floor where hot, smoky water
shoots up. This water contains hydrogen sulfide.
Amazingly, even here there is life. Bacteria absorb the
hydrogen sulfide for nourishment.
These bacteria, in turn, are food for other living things,
including these giant tube worms,
white crabs,
and giant clams.
The living things that exist at ocean vents are different
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from all other kinds of life.
Other living things depend either directly or indirectly on
the sun for energy.
Through photosynthesis, plants use the energy of light from
the sun to manufacture their own food.
And animals eat either plants or other animals that eat
plants.
But the life that exists at ocean vents depends not on the
sun for energy but on chemicals from the earth.
The discovery of these unusual forms of life emphasizes
how much we still don't know about what goes on in the
deepest reaches of the oceans.
Male Narrator:
Other things that occur on the surface are easier to observe.
Look at this dock and notice where the water reaches.
Here is the same spot 6 hours later. See where the water
reaches now.
Twice a day, along coasts worldwide, the level of the water
rises and falls.
The daily rises and falls of ocean waters are called tides.
Tides are caused mainly by the moon. Like the earth, the
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moon has gravity.
The moon's gravity pulls both the solid earth and the ocean
water, but it pulls the ocean waters nearest it more strongly.
This causes the water to bulge toward the moon, resulting in
a high tide.
At the far end of the earth, the water is pulled less strongly
than the earth, and this causes a tidal bulge there as well.
Halfway between the two high tides, low tides are formed.
These low tides are the result of water's flowing to the
locations where there are high tides.
If the earth and moon stood still, high and low tides would
always be in the same place. However, the moon orbits
around the earth, and the earth rotates.
This movement of both the moon and the earth results in two
high tides and two low tides each day.
Female Narrator:
Another thing we can observe, even standing on shore, is that
the oceans are constantly moving. Every few seconds a new
wave breaks onto a beach. This is repeated thousands of
times a day, millions of times a year.
Most waves are caused by wind that blows across the water's
surface. On a calm day, there may be a steady movement of
smooth, low waves caused by winds far out at sea.
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Hurricanes, on the other hand, can cause waves as high as
30 meters, or almost 100 feet. Even with waves this high,
however, the water moves up and down, but it doesn't move
forward.
You can see that this is true by putting a piece of paper in a
tray filled with water.
Then, using a straw, blow straight down on the water.
Air from the straw creates small waves that move the piece
of paper up and down, but otherwise the paper keeps its
position.
Male Narrator:
Waves caused by wind are different from another kind of
ocean movement that can be seen along most coasts.
If you walk along a beach, you may see bottles, wood, pieces
of plastic and other things that have washed ashore.
Many of these things are debris tossed overboard from boats
and ships far out at sea.
Even on uninhabited islands in the Pacific, there is debris on
the beaches. Some of it came from places thousands of miles
away.
The debris was carried by currents, rivers of water that flow
through the oceans.
26
Female Narrator:
Scientists can trace currents by using pictures, taken by
satellites, that measure different temperatures of the oceans'
water.
In this map, warmer temperatures are shown in red and
yellow, and cooler temperatures in blue and green.
Currents from the equator move warm water toward the
poles where it becomes cooler again.
Currents from the polar regions move cold water towards
the equator, where the water becomes warmer.
Surface currents like these are caused by winds and the
rotation of the earth.
Male Narrator:
There are also currents under the ocean surface. Some are
caused by differences in the density of water. Just as a
submarine sinks when it is more dense than the water
around it, cold water is denser and sinks under warmer
water.
You can simulate the effects of these currents by putting a
colored ice cube in a glass of warm water.
As the ice melts, the colder, denser water sinks, just as cold
water in the oceans sinks.
27
to microscopic plankton that are responsible for producing
most of our atmosphere's oxygen to strange tube worms that live near vents in the ocean floor.
Female Narrator:
We looked at the landscapes that form the ocean bottom,
including the shallow continental shelf and the steep continental slope.
We saw mountain ranges called mid-ocean ridges where
lava from deep in the earth spills out to form new ocean
floor,
and trenches that are the deepest places on earth.
Male Narrator:
We also looked at how the moon affects tides. We
examined waves and currents And we saw how scientists have used submersibles and
other tools to explore parts of the ocean that until recently
were hidden from human view.
Female Narrator:
But the oceans are not just for scientists to explore. There is
much that each of us can discover.
29
Even by just wading in the shallow water along a beach, we
can all learn more about the oceans.
And as we learn, we appreciate more the importance of the
oceans to Earth, the blue planet.
END.
30
CLOZE EVALUATION QUESTIONS
OCEANS: EARTH'S LAST FRONTIER
NAME_______
DIRECTIONS: Select the answer, from the four choices given, by circling the correct letter.
1. Our earth is often called the blue planet because about 70% of the planet is
covered by water. The ocean _____ is a dynamic environment of plant and animal
species. The types and varieties of creatures are as extensive as anything found
on land.
1.
A.
B.
C.
D.
2. Scientists have studied the ocean for many years and have identified various
areas or zones of life forms. At the bottom of the ocean, called the ________
zone, you might find such creatures as crabs and shellfish.
2.
A. benthos
B. nekton C.
cellar D.
trench
3. Another ocean zone is found between the bottom and surface regions. This
zone is called the _____ and is home to a large variety of fish. Depending upon
the ocean, you might find sharks, bluefish, tuna, cod and a multitude of other freeswimming species in this region.
3.
A. benthos B.
trench C. nekton
D. fish region
4.
A. zooplankton B.
plankton C.
phytoplankton D.
algae
5.
A. protozoa B. algae
C. zooplankton D.
phytoplankton
6.
A. amoeba
B. protozoa
C. zooplankton
D. one-cell-life-forms
7.
A. tanker
B. submersible
C. scuba tank D.
snorkel
8.
A. continental shelf B.
continental slope C.
trench D. ocean valley
9.
A. trench
B. continental shelf C.
continental slope D.
ocean valley
4. In order for ocean life to thrive there must be producers and consumers of food.
One of the ocean's basic food sources is a group of creatures collectively known as
_______. These plant and animal life forms are too small to be seen
with the naked eye. They live in very large colonies and are of two basic types.
5. The first group of plankton are of the plant variety. These _____ come in a great
many shapes and are green in color. They produce food, as plants do on land,
through the process of photosynthesis. They are a food source for others.
6. The phytoplankton produce oxygen which is necessary for life in the sea and on
land. These creatures serve as a food source for another type of plankton called
_____. This type of plankton becomes part of the ocean food chain as they are
eaten by small fish as well as the largest ocean dweller, the whale.
7. Scientists have studied the ocean by diving beneath the surface and observing
the life forms there. In order to collect data about the life deep in the ocean, a
_____ must be used. This device can stand the great water pressure that is
found deep below the surface.
8. Over the years, scientists have mapped the world's oceans and the rock and
sand formations below the surface. The _____ is a part of the ocean that extends
out from the shoreline in a gentle decline. In this region there is an abundance of
sea life and here is where marine life is harvested.
9. As the ocean land form begins to drop, we come upon another important
ocean feature. This is the _______ and it is an area that leads to some of the
ocean's deepest regions. As one travels farther down to the great depths, the
marine life diminishes.
10. Other ocean features that are similar to our canyon areas on land are found at
great depths. These _____ can be so deep that one in particular, the Marianna
formation, is seven times deeper than the Grand Canyon. Our oceans are truly
the earth's last frontier and we must do all we can to protect it from pollution and
preserve its beauty and life forms.
This form may be reproduced without permission from Rainbow Educational Media.
bottom
current
surface
ecology
10. A. ocean basins B.
ocean valleys C.
ridges D. trenches