Science Notes
February 8, 2012(Revised)
SOL 5.6 Oceans
The Earth is composed of approximately 70% water. Keep in mind that all the
Earth’s oceans are connected and are constantly in motion. The basic motions of
the ocean are current, tides, and waves. Currents are ocean waters that travel in
huge circular patterns. Currents mix the waters of the world together and affect
where ocean plants and animals live, weather patterns, and also the movement of
ships around the world. Three things cause currents: wind patterns, temperature,
and salinity.
Tides are influenced by the gravitational pull of the moon and the sun. However,
the moon has a greater influence because the Earth is closer to the moon.
Waves have tiny water particles, which move in circles. Waves are moved by
energy.
Winds that blow in the same directions every year create wind patterns, which in
turn create huge currents. One of the strongest and most known currents in the
world is the Gulf Stream. Located in the Atlantic Ocean, the Gulf Stream blows
warm winds along the east coast of the United States.
Changes in temperature can create currents. The sun heats the surface of the
ocean, especially at the equator. As these waters near the surface get warmer, the
water gets lighter and rises. As the warm water rises, cold water gets pushed down
deeper in the ocean. These up and down movements of hot and cold water
create currents.
Salinity also creates currents. When ocean water is heated, it begins to evaporate,
leaving the salt behind. Salt is heavy and sinks deeper into the ocean. Less salty
water is lighter and rises to the surface. This sinking and rising of salt water
creates currents.
Ocean water is an extensive mixture of gases, such as air, and dissolved solids,
such as salts. This mixture supports many marine animals and plants. These plants
and animals are affected by the physical characteristics of the ocean environment.
The physical characteristics include depth, temperature, salinity, waves, and
currents.
Depth refers to how deep the ocean is. The ocean differs in depths throughout the
world. Depth can affect where marine plants and animals live. Sunlight can
penetrate only so far beneath the ocean’s surface. The deeper one goes down into
the ocean, visibility decreases. Plant life is especially dependent upon depth. Plants
need sunlight in order for photosynthesis to occur, therefore, they need to live
near the surface of the ocean. After about 3,000 feet, there is no plant life, but
there are animals that live in the pitch black depths of the ocean. These animals
have adapted to their surroundings and thrive in this environment.
Temperature is another factor that affects where ocean plants and animals live.
Temperatures range from the warm waters of the tropics to the freezing waters
of the Polar Regions. Animals that live in warmer waters include living coral reefs,
manatees, rays, and horseshoe crabs. Animals that live in colder regions include sea
mammals and fish. These fish have special antifreeze in their blood that assists
them in their survival of the cold water. Sea mammals in the arctic regions rely on
a thick layer of fatty blubber and fur to help them survive.
Salinity can also affect where marine plants and animals can live. Salinity is the
amount of salt that is dissolved in the ocean. Salinity in the ocean varies. Factors
such as rainfall, river runoff, evaporation, and ice formation can cause the
salinity of a body of water to change. When rain falls to the Earth, it either falls
into rives or soaks into the ground. This water runs to the ocean. As this fresh
water enters the ocean, it actually lowers the salinity of the ocean water. When
this water eventually evaporates, the salt is left behind, which increases the
salinity of ocean water. Ice formation has the same result as evaporation.
Animals that live in salty water have developed ways to deal with the salty
environments in which they live. Their bodies regulate the amount of salt they take
in to equal the amount of salt that is in the surrounding water. If they are moved
to waters that have a higher or lower amount of salt, they could eventually die.
Other important terms to know:
Density refers to how tightly packed an object is, which can affect its buoyancy.
Buoyancy is the ability of an object to float. When an object is able to float, it
must weigh less than the amount of water that surrounds it. Think of a ship that
weighs several tons afloat in the Atlantic Ocean. The Atlantic Ocean is a vast body
of water. All of that water outweighs the ship, enabling the ship to float. That
same ship weighing several tons, in all probability, would not float in the Smith
River because the water in the Smith River does not outweigh the ship.
As stated before, oceans depths vary throughout the world. The ocean floor looks
a lot like the land formations we see on land, such as plains, valleys, hills, and
mountains. Some important parts of the ocean floor are the continental shelf,
continental slope, continental rise, abyssal plain, mid ocean ridge, seamount,
guyot, and ocean trenches.
The continental shelf is the part of the ocean floor that is connected to the
shoreline. When we play in the ocean, we are standing on the continental shelf. It
has thick layers of sand, mud, and rocks.
The continental slope begins as the edge of the continental shelf and drops to
depths of over two miles. It also has layers of sand, mud, and rocks.
The continental rise is a smooth sloping area that connects the steep walls of the
continental slope to the bottom of the ocean floor. It, too, is covered with thick
layers of sand, mud, and rocks.
The abyssal plain is the flat area of the ocean floor. It is covered with sand, mud
and plant and animal remains.
Mid ocean ridges are mountain ranges that are found on the ocean floor.
Seamounts are isolated volcanoes or mountains found on the ocean floor.
A guyot is an extinct volcano with a flat top found on the ocean floor.
Ocean trenches are the deepest part of the ocean floor. They are similar to
canyons that are found on land. The deepest ocean trench on Earth is found in the
Pacific Ocean called the Marianas Trench at 36, 198 feet. The Grand Canyon, which
is the largest canyon on Earth, is only 5, 300 feet.
All living things on Earth need food to survive. When an animal eats a plant or
another animal, a food chain has begun. All food chains begin with a producer. On
land, the primary producers in food are plants. The same is true in oceans. The
producers in the ocean are microscopic plants called phytoplankton. In the ocean,
as in any food chain, there are producers, consumers, and decomposers.
An example of a food chain could be: Phytoplankton are eaten by small, shrimp-like
animals called krill; small fish eat the krill; jellyfish eat the small fish; and then,
sea turtles eat the jellyfish. In addition to this food chain are organisms that live
on the ocean floor. These decomposers feed on the decaying remains of surface
plants and animals that slowly sink to the ocean floor. Rock lobsters and different
forms of bacteria are examples of these ocean food chain decomposers.
When two or more food chains overlap and connect, a food web is formed. The
above food chain can easily be turned into a web by adding huge whales that will
eat the krill; tuna and kingfish that will eat the smaller fish and jellyfish; and
swordfish that will the tuna, kingfish, jellyfish, and the small fish.
The ocean affects our lives as well. We depend on the ocean for resources such as
oil, gas, and food. When you think about it, our environment is greatly affected by
the ocean environment.