Waves, Tides and Currents in Ocean water
The waters of the oceans are never still. In fact there are three types of motions of these waters---- waves, Tides and currents. |
| Motion of ocean water |
What are Waves?
The action of winds causes disturbance on the surface of water. When a wind blows over the Ocean surface, it pushes down the small particles of water.
Each particle is push down and it comes up again. So it actually moves up and down in a circular path. But the particles are all tightly packed together. So every particles passes on its motion to the next. The rhythmic movement of the water particles produce a pattern which we see as waves.
The disturbance, or the wave, travels in the direction of the wind. It is important to note that water actually does not travel with the wave. This is somewhat like the spectators in a stadium doing the Mexican wave. Each spectator only moves up and down, but the ways passes right down the stadium.
The height of the Waves depends on the speed of the wind. During a storm the waves are very high and when the weather is calm the waves are gentle.
What is Tsunami?
A tsunami is a very long wave caused by a submarine or costal earthquake, landslide or volcanic eruption. As it near near the coast, it built up in height. When it crashes onto the shore, it causes enormous destruction.
Tsunami in the Indian Ocean in 2004
a powerful earthquake occurred on the floor of the Indian oceans on 26 December 2004.
It originated near the Indonesian island of Sumatra where the Indian Plate slides under the Eurasian plates. It was a part of the ocean floor by several metres comma causing tsunami that killed more than 275,000 people.
The regions worst affected were the cost of Indonesia,South India,Srilanka and Thailand. Some places in this reasons wahit by waves are most 30 metres height. The tsunami is also travel across the globe, causing death on the eastern coast of Africa. They were even noticed on the Western coast of North and South America.
Tsunamis are rare in the Indian Ocean.So Earth Tsunami warning system like the one for the Pacific oceans, had not been developed for this region.
Most of the victims were, therefore, caught unprepared. And, they could not recognise warning sign such as that temporary receding of the ocean from the shore and frothing bubbles near the water's edge. However Tilly Smith British school girl holidaying in Phuket , Thailand, did recognise the warning signs.She saved many lives by raising a timely alarm.
In India about 16000 you were killed. The Andaman and Nicobar Island were the worst affected. Some islands in the reason were completely washed away stop on the mainland, tsunamis travel several kilometre inland, causing widespread destruction and death in Andhra Pradesh, Pondicherry,Tamil Nadu and Kerala.
TIDES
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| Low Tide |
What are Tides?
High Tide when the level of water rises and water moves for the update it is high tide.
Low Tide when the level of water falls in water recedes from the shore, it is low tide.
A place usually has high and low Tides twice in a day.
What are the cause of Tides?
Tides are caused by the gravitational pull of the moon and the sun on the earth attraction of the moon is stronger because the moon is much closer to the Earth than the Sun is.
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| Spring tide and Neap tide |
What are Spring Tides?
Sometimes the poles of moon and the sun in the same line. This happens during is full moon and New Moon, when the sun the moon and the earth are practically in a line. On Saturdays, the high Tides are higher than usual and the low Tides, lower than usual. Such Tides are called spring tides.What are Neap Tides?
When the moon is in the first quarter or the third quarter, the position of the moon and the sun with respect to the earth are at right angle to each other. The height of the tide produced by the Moon's attraction is reduced by the sun's attraction on the water in the low tide regions.On such days high tide are not as high as usual and low Tides are not as low. Such Tides are called neap tides.What are importants of tides?
Tides are helpful to us in the following ways:--
The rise in water level during high tide allows big ships to enter or leave harbours safely. The ports of Kandla in Gujarat and Diamond Harbour in West Bengal depend on such tides.
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| tide useful for navigation |
During high tide, water rushes up the mouth of river. This helps large ship to move in and out of river ports like Kolkata, London, Hamburg, Rotterdam and New York.
The saline water of the sea freeze at the lower temperature than river water does. In cold countries, the sea water rushing in during high tide, prevents from freezing in winter. The harbour of London is one such harbour.
The water at high tide can be store behind specially built dams and used for hydroelectric power generation.
What are Ocean currents?
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| Ocean Current |
In certain parts of the oceans, the water moves along a definite Direction. This masses of ocean water moving in different direction are called ocean currents .
What are drifts
Slow moving masses of water are called drifts. Often, as a current moves away from its origin, it becomes a drift.
What are the causes of Ocean Currents?
Oceans currents are caused chiefly by the action of the planetary winds on the surface water of the ocean.
The shapes of the land of the land masses modify the causes of ocean currents.
Due to the rotation of the earth the currents in the Northern hemisphere are deflected to the right of their paths, while in the Southern hemisphere they are deflected to the left.
Generally the currents move clockwise in the Northern hemisphere and anticlockwise in the southern hemisphere.
What are Warm Current?
The current that carry warm water from the tropical reason to the higher latitude are warm currents.
What are Cold Current?
The current that carry colder water from the higher latitude to the lower latitude are called cold currents.Generally warm currents flow along the east coast of the continents while cold currents flow along the West Coast.
The colder and salter water of the polar regions being heavy sink below the surface waters.They are carried by deep ocean current towards the lower latitudes.
How ocean currents influence the climate of coastal regions?
Ocean currents influence the climate of coastal regions.In fact ,winds blowing from the sea often carry the influence of ocean currents far inland.Cold currents make a place older then other places on the same latitude. one current make a place somewhat warmer. for example the course of Norway located within the Arctic Circle remind free of ice in winter due to the warming influence of the North Atlantic drift. spots on the labrador cost of North America lying at much lower latitude freeze over in winter under the influence of the cold labrador current.
Ocean currents also influence rainfall.Winds passing over warm currents pick of moisture and cause heavy rainfall. Eastern USA and the Western coast of Europe receives much rainfall.
On the other hand,winds passing over cold currents become cool and dry and bring hardly any rainfall. Hence desert are found near the Western coast of continents along,which cold current generally flow.
The Atacama desert in South America and the Namib desert in Africa are example of such desert.
Other effects of Ocean Currents
The places where warm and cold currents meet are rich in organism, known as plankton that serve as food for fish.Such places are good fishing ground.
the meeting place of the warm Gulf Stream and the cold Labrador Current near Newfoundland, and the meeting place of the warm Kuro Shio and the cold Oya Shio,or Kuril Current near Japan are good fishing grounds.
Ocean currents influence navigation too. If a ship sails along a current its speed increases.If it sails against a current, its speed decreases. So in order to save time and fuel, ships generally sail with the current.Warm Current also help to melt Iceberg which are dangerous for ships.
Sometimes, however ocean current cause problem for ships. Thick fogs occure where cold and warm currents meet, this reduce visibility.
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