The Hydrosphere
* The Hydrosphere is made up of water.
* Water covers more than 71% of the earth’s surface and land covers just 29%.
* More than 97% of water on the earth is in the oceans and seas.
* A little less than 3% of water is in the form of glaciers.
* A very small percentage of water is available as fresh water.
The four major oceans are:
* Pacific Ocean
* Atlantic Ocean
* Indian Ocean
* Arctic Ocean
Oceans Currents
* Oceans currents are streams of water flowing constantly on the Ocean’s surface in definite directions.
* Ocean currents move in the same pattern as winds – clockwise in the northern hemisphere and anti – clockwise in the southern hemisphere.
* Warm ocean currents originate near the equator and move towards the poles.
* Cold Ocean originates near the poles and move towards the tropics.
* Ocean currents affect the climate of an area.
* The mixing of warm and cold currents gives rise to foggy weather.
* The areas where warm and cold currents meet provide the best fishing grounds of the world.
Ocean Movements
* The movements that occur in the oceans can be classified as waves, tides and ocean currents.
* The alternate rise and fall of water in the ocean is called a wave.
* Tsunami is a series of huge, destructive waves, caused by underwater earthquakes, volcanic eruptions and underwater landslides.
* The rhythmic rise and fall of ocean water twice a day is called a tide.
* When ocean water rises to its highest level and covers much of the shore, it is high tide.
* When the water falls to its lowest level and recedes from the shore is a low tide.
* The gravitational pull of the moon and the sun on the earth’s surface causes tides.
* Spring tides are exceptionally high tides, and occur when the sun, the moon and the earth are in the same line.
* Neap tides are low tides that occur when the sun and the moon are at right angles to each other.
* Tides help in navigation, fishing and generating electricity.
