Oceans Of The World

Oceanography:  Water covers 70.9% of the Earth's surface and is vital for all known forms of life. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and o.001% in the air as vapour, clouds (formed of solid and liquid water particles suspended in air), and precipitation.Oceans hold g97% of surface water; glaciers and polar ice caps 2.4%; and other land surface water bodies such as rivers, lakes and ponds hold around 0.6% of surface water. A very small amount of the Earth's water is contained within biological bodies and manufactured products.

Water, on the Earth, moves continually through a cycle of evaporation or transpiration, precipitation, and runoff - usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land. Brief description about the five oceans is given below:

(1) The Arctic Ocean: It is smallest of the world's oceans and centred approximately on the North Pole. Surrounded by landmasses of Eurasia, North America and Green land, it covers an area of about 4,372,000 square miles. It is not marked by perennial ice cover.

(2) The Atlantic Ocean: The Atlantic Ocean is located between North and South Americas in the west, and Europe and Africa in the east. It covers an area of about 82,000,0o square km. It is 'S' shape ocean, which is supposed to be formed about 700 million years ago due to sea-floor spreading.

The Mid-Atlantic Ridge is the most important geographical feature of the Atlantic Ocean. It spreads throughout this ocean from Greenland in the north to Falkland Island in the south, dividing the ocean into two parts. It was formed due to divergence of American and African plates.

(3) The Pacific Ocean: The Pacific Ocean, the largest ocean of the world, covering 1/3rd of its area, extends from for 16,000 km from the east coast of Asia in the west to the west coasts of America in the east. It is marked by parallel mountain ranges along both its coasts. There are number of trenches, deeps, guyots and submarine canyons in this ocean. Mariana trench, the deepest trench in the world is found in this ocean.

(4) The Southern Ocean: Extending from the coast of Antarctica north to 60 degrees south latitude, this acean covers the area around the South Pole. It is the fourth largest ocean of the world. It is marked by narrow continental shelf; icebergs; cold oceanic currents etc.

(5) The Indian Ocean: The Indian Ocean is smaller than the Pacific and Atlantic Oceans in area and is bounded by, on all its sides, Asia in the north, Africa in the west, Asia in the east, Australia in the southeast and Antarctica in the south. It is triangular and its average depth is 4,000 m. Major parts of the coastal  lands of Indian Ocean formed by Block Mountains of Gondwanaland are compact and solid. Sunda trench near Indonesia is its main feature.

The Indian Ocean is triangular and bordered by Africa, Asia, Antaretica, and Australia, and stretches southward to Antaretica. Although it covers about 28.5 million square miles, it is smaller than the Atlantic Occan and less than half the size of the Pacific Ocean. Its maximum width is 6,200 miles between the southernmost portions of Africa and Australia. The Indian Ocean contains about 20 percent of the earth's water surface. The average depth of the Indian ocam a abou12,750 fect. The deepest is 24,440 feet in the Java Trench in the extreme northeast corner of the basin.

The Profile of the Ocean Floor: The floors of the oceans are rugged and complex with world's langest mountain ranges, deepest trenches and larges plains. In general, the occan floor can be divided into four major divisions:

(i) The continental shelf

(ii) The continental slope.

(iii) The continental rise.

(iv) The abyssal plain

OCEANS OF THE WORLD (by size):

Pacific              (155,557,000 sq km)

Atlantic            (76,762,000 sq km)

Indian                (68,556,000 sq km)

Southern           (20,327,000 sq km)

Artic                   (14,056,000 sq km)Note: The International Hydrographic Organisation approved the Southern Ocean in year 2000. It is now the fourth largest ocean.