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North equatorial stream, the Kurushivo stream, North Pacific stream, the California stream.

(a) Labrador current.

Unlike Atlantic and Pacific ocean, the ocean currents of Indian ocean are not so definite and systematic. It is because of the seasonal winds which flow in Indian ocean. In summer season, these winds blow in south-west direction and in winter season, these direction blow in north-eastern direction. Because of this change the ocean currents also change their direction.

• According to Ferral’s law, ocean currents move to their right in the southern hemisphere.
• Warm currents move towards cold seas and cold currents move towards the warm seas.
• In the lower latitudes, warm currents flow on the eastern shores and cold on the western shores.
• In the higher latitudes, warm currents flow on the eastern shores and cold on the western shores.
• Cold and warm currents meet along the convergence and move out along divergence.
• Cold currents move as sun-surface currents and warm currents move as surface currents.

The rhythmic rise and fall of ocean water twice in a day is called Tide.

The sea water continues its up and down movement. According to climatic positions, the speed sometimes increases and sometimes slows down and it produces waves. The water particles run up and down and it looks as if there are wrinkles on the surface of the sea.

Sometimes the ocean water takes a fix direction, then it is called oceanic current. In the ocean water leaves one place and moves towards the other place regularly. The speed of the current can be 2 km/hr to 10 km/hr.

Near this place, there is a meeting of the warm gulf stream and cold labrador current. So, there is a blanket of dense fog.

Many salts are mixed in seawater. That is why the seawater is salty.

1. True

2. False

3. False

4. True

5. True

The ocean water has three speeds waves, currents and tides.

On the surface of earth, there are big storehouses of water which are known as oceans. The water of these oceans is salty.

(a) Cold stream

Fresh Water:  Rainfall, melting snow, rivers, canal, water pumps, etc. give us fresh water.

Saline Water: Mostly found in oceans. The most salt is in Dead sea. It is surrounded by earth from all the sides.

There are five oceans on earth. 

Their names are :

• Pacific ocean, Atlantic oceans, Indian ocean, Arctic ocean, Antarctic ocean.
• All these oceans are” combined with each other. The water of one ocean mixes with the other. 

he most important hot water stream in the world is Gulf Stream. It starts from Mexico Gulf and reaches Newfoundland Islands.

This happens because on these two nights the attraction of sun doubles up with the attraction of moon. Because of its double attraction the high tide takes place.

In wave, the water goes up and down continuously but it does not take speed. On the contrary in the current, water moves from one place to another.

1. Northern ocean and southern ocean

2. 16.6 crore sq. km

3. Pacific

4. South Atlantic

5. Maxico

Sea water is salty or saline. This is because the sea contains a great variety of salts and minerals in solution. These minerals are brought down by the rivers in the silt they carry. It is estimated that the ocean contains enough salt to cover the continents with a layer 100 metres thick.

Tides

Tides are caused by gravitational pull of the moon, and to some extent the pull of the sun on the earth’s surface.

The moon exerts gravitational pull on the earth as it orbits around it. This has little effect on land which is solid and inflexible but it has a great effect on the ocean waters because water is liquid can freely move about.

There is the hot current of water which is called North Oceanic hot water current. It flows near the Norway Coast. So, the fishermen go deep into the sea for fishing.

On these two dates the Moon and the Sun make 90° turn with the Earth. As a result, both attract the sea water in reverse directions. Because moon is closer to-the sea, the water jumps more towards the moon. But because of counter attractions of sun the effect of moon’s attractions becomes very less and as a result the jump of water becames too low and it is called low tide.

The ocean water always remains up and down. The water particles keep on jumping and this makes the ripples on the surface of sea. These are called waves. The waves are created because of the speed of the winds. When winds passes over the sea they shake the surface of water. This shaking and shivering of water surface is called waves.

Because of the effect of North Oceanic warm current these ports do not freeze and remain open even during the winter season.

The local winds have the greatest effect on the direction of the currents. The direction in which the winds blow for a longer period, the ocean water also takes the same direction. In the north-Indian ocean the winds move in reverse direction in summer and winter. So, the water current also has reverse direction during summer and winter.

Whenever some winds pass over the cold currents, then these become cold and dry. So, the closer regions become deserts.

The ships generally move in the direction of currents. It increases there speed and consumes less fuel.

1. The warm currents increased the temperature of their neighbouring areas and cold currents decrease the temperature of their neighbouring areas.

2. The winds passing over warm currents absorb the humidity and bring rainfall on coastal areas. Whereas the winds passing over cold currents become cold and dry.

South Atlantic ocean has two main currents :

1. The Falkland current and

2. Venezuela current.