OceansWhat is the hydrosphere?
Have you ever seen pictures of the earth from space? You can see clouds, land and water. In fact, you see mostly water. That is why Earth is sometimes called the “water planet.” Only 29 percent of Earth’s surface is land. The rest, 71 percent, is water. We call the water part of our planet the hydrosphere [HY-droh-sfeer.]
The hydrosphere includes all the salt water and fresh water on Earth. Salt water makes up about 97 percent of all the water on Earth. Most of the salt water is in the world ocean. Some fresh water is found in ponds, rivers, lakes and streams. However, most of the fresh water on Earth is frozen in ice near the poles.
The world ocean makes up most of the hydrosphere. But we think of this world ocean as three major oceans. They are the Atlantic, Pacific and Indian Oceans. We also use the names Arctic Ocean and Antarctic Ocean for areas of the Atlantic and Pacific Oceans.The Pacific Ocean covers the largest area of the world ocean. More than half of Earth’s ocean water is in the Pacific. The Pacific Ocean is also the world’s deepest ocean. The Atlantic Ocean is the second largest ocean. The Indian Ocean is the smallest ocean.
The oceans are all connected, but the waters move as if they were several separate bodies. These separate movements are called ocean currents. Currents have been called “rivers of water” in the ocean.
Key Terms
Oceanography – Study of Earth’s ocean including biological, chemical and physical features
Hydrosphere – All the fresh and salt water on planet Earth, including oceans, lakes, seas, rivers, streams and glaciers plus all the water in the atmosphere
Atmosphere – The blanket of gases surrounding a planet
Ocean Currents – Huge amount of moving water that is consistent in direction and speed
Polar– Cold regions on Earth, more than 66.5°N and 66.5°S of the equator
Tropical - Warm region on Earth between 23.5°N and 23.5°S of the equator
Tides – Predictable pattern of rise and fall of sea level caused by gravitational pull of Moon and Sun
Ocean Currents
The above diagram shows some major surface ocean currents. Notice the general circular paths. Each current moves ocean water a great distance.
What causes ocean currents?
- Global winds are the chief cause of currents.
- The spinning, rotation, of the earth causes currents to turn.
- The continents, land, cause the currents to turn.
- Different densities of water
- Salt water is denser than fresh water
- Cold water is denser then hot water
The ocean currents can be warm or cold. Currents that flow from the equator are warm currents. Currents that come from the North Pole and South Pole are cold currents.
Use the diagram aboveto answer the following questions:
1. Use a colored pencil to trace all the currents north of the equator.
2. North of the equator, the ocean currents move in a ______direction. clockwise, counterclockwise
3. Use a different colored pencil to trace all the currents south of the equator.
4. South of the equator, the ocean currents move in a ______direction. clockwise, counterclockwise
Follow the path of the Gulf Stream Current.
5. The Gulf Stream starts in the Gulf of Mexico, where the water is ______.
warm, cold
6. The Gulf Stream flows ______toward Europe.
northeast, southwest
7. The Gulf Stream flows toward the coast of ______.
Japan, England
Use the map of surface ocean currents to help you identify which current….
8. If you tossed a bottle into the ______Ocean, the bottle could be washed up on the coast of Japan. Pacific, Atlantic
9. The bottle would be carried toward Japan by the ______current. Gulf Stream, Japan
10. If you tossed a bottle into the ______Ocean, it could be washed up on the coast of England. Pacific, Atlantic
11. The bottle would be carried toward England by the ______current. Gulf Stream, California
12. The ocean currents near Brazil are ______, because they come down from the equator. warm, cold
Ocean Currents Affect Climate
The oceans and the atmosphere work together in many ways. Most water in the atmosphere has evaporated from the ocean. Air masses pick up water over the oceans and bring rain to the land. But ocean currents also affect climate.
For example, the Gulf Stream starts near the equator, which is a warmer part of the earth. Gulf Stream water is warmer than the water next to it. Winds that blow over the Gulf Stream pick up some of this warmth and moisture. The warm, moist air blowing over the Gulf Stream brings mild weather with it. London is famous for its “pea soup” fogs. These fogs form when warm Gulf Stream water meets colder water off the English coast.
Ocean Currents Also Affect Sea Navigation
Imagine that you are a ship’s captain.
1) If you were sailing to England from the United States, you would ______the Gulf Stream. seek out, avoid
2) Why? ______
______
______
3) If you were sailing from the United States to England you would ______the Gulf Stream. seek out, avoid
4) Why? ______
Fill in the Blank
Complete each statement using a term or terms from the list below. Write you answers in the spaces provided.
Continentcold currentsequatorwarm currents
Ocean currentsglobal windspolesmove at an angle
Clockwise
1) The general surface movements of the ocean waters are called ______.
2) The chief cause of the surface ocean currents is the ______.
3) The turning of the earth makes the currents ______.
4) An ocean current turns when it comes near a ______.
5) In the northern hemisphere, the ocean currents move in a ______direction.
6) Ocean currents are classified as ______and ______.
7) Warm currents start near the ______.
8) Cold currents start near the ______.
Use the diagram below to answer questions 9 – 11.
Most of the earth’s water is part of one huge ocean. But this ocean has been divided into three major oceans.
9) Name the three major oceans ______.
10) Which of these three is the largest ocean and holds the most water? ______.
11) What other names do we use for areas of the Atlantic and Pacific Oceans? ______.
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