Information About Different And Famous Oceans Of The World.

Oceans,

 Pacific Ocean, largest and deepest of the world's four oceans, covering more than a third of the earth's surface and containing more than half of its free water. It is sometimes divided into two nominal sections: the part north of the equator is called the North Pacific; the part south of the equator, the South Pacific. The name Pacific, which means peaceful, was given to it by the Portuguese navigator Ferdinand Magellan in 1520.
BOUNDARIES AND SIZE
The Pacific Ocean is bounded on the east by the North and South American continents; on the north by the Bering Strait; on the west by Asia, the Malay Archipelago, and Australia; and on the south by Antarctica. In the southeast it is arbitrarily divided from the Atlantic Ocean by the Drake Passage along 68° west longitude; in the southwest, its separation from the Indian Ocean is not officially designated. Apart from the marginal seas along its irregular western rim, it has an area of 166 million sq km (64 million sq mi), substantially larger than the entire land surface of the globe. Its maximum length north to south is 15,500 km (9,630 mi) from the Bering Strait to Antarctica, and its greatest width is 17,700 km (11,000 mi) from Panama to the Malay Peninsula. Its average depth is 4,280 m (14,040 ft). The greatest known depth in any of the world's oceans is 11,033 m (36,198 ft) in the Mariana Trench off Guam.
III  GEOLOGIC FORMATION AND STRUCTURAL FEATURES
The Pacific is the oldest of the existing ocean basins, its oldest rocks having been dated at 200 million years. The major features of the basin and rim have been shaped by the phenomena associated with plate tectonics. The coastal shelf, which extends to depths of 180 m (600 ft), is narrow along North and South America but is relatively wide along Asia and Australia. The East Pacific Rise, a midocean ridge system, extends 8,700 km (5,400 mi) from the Gulf of California to a point 3,600 km (2,240 mi) west of the southern tip of South America, and rises an average of 2.1 m (1.3 ft) above the ocean floor. Along the East Pacific Rise molten rock upwells from the earth's mantle, adding crust to the plates on both sides of the rise. These plates, which are huge segments of the earth's surface, are thus forced apart, causing them to collide with the continental plates adjacent to their outer edges. Under this tremendous pressure, the continental plates fold into mountains, and the oceanic plates downbuckle, forming deep trenches, called subduction zones, from which crust is carried back into the mantle (see Earth: Plate Tectonics). The stresses at the areas of folding and subduction are responsible for the earthquakes and volcanoes that give the rim of the Pacific basin the name “ring of fire” (see Ocean and Oceanography).
IV  ISLANDS
The Pacific Ocean contains more than 30,000 islands; their total land area, however, amounts to only one-quarter of one percent of the ocean's surface area. The largest islands, in the western region, form volcanic island arcs that rise from the broad continental shelf along the eastern edge of the Eurasian Plate. They include Japan, Taiwan, the Philippines, Indonesia, New Guinea, and New Zealand. The oceanic islands, collectively called Oceania, are the tops of mountains built up from the ocean basin by extruding molten rock. The mountains that remain submerged are called seamounts. In many areas, particularly the South Pacific, the land features above the sea surface are accretions of shell material (see Coral Reef). Along the eastern edge of the Pacific, the continental shelf is narrow and steep, with few island areas. The major groups are the Galápagos at the equator, which rise from the Nazca Plate, and the Aleutians in the north, which are part of the North American continental shelf.
V  CURRENTS
The driving forces for ocean currents are the earth's rotation, wind friction at the surface of the water, and variations in seawater density due to differences in temperature and salinity. The interaction between wind and current has a major effect on climate and is studied for long-range weather prediction and for sea travel.
The surface currents of the North Pacific consist of two gyres, or circular systems. In the extreme north the counterclockwise Subarctic Gyre encompasses the westward-flowing Alaska Current and the eastward-flowing Subarctic Current. The main body of the North Pacific, however, is dominated by the huge North Central Gyre, which circulates clockwise. It encompasses the North Pacific Current, flowing east; the California Current, flowing southeast; and the Kuroshio Current (or Japan Current), flowing north up the coast of Japan. The California Current is cold, broad, and slow-moving; the Kuroshio is warm, narrow, and rapid, similar to the Gulf Stream. Close to the equator at 5° north latitude, the eastward-flowing Equatorial Countercurrent separates the North and South Pacific systems but sends most of its waters into the North Equatorial Current. The South Pacific is dominated by the counterclockwise-moving South Central Gyre, which encompasses the South Equatorial Current flowing east and south, the South Pacific Current flowing west, and the Mentor Current flowing north, parallel to South America. Located in the extreme south is the Antarctic Circumpolar Current (West Wind Drift), which encircles the globe, merging the waters of the Pacific, Atlantic, and Indian oceans. It is the most important source of deep-sea circulation. From it flows the broad, cold Peru, or Humboldt, Current, which travels north along the coast of South America and sends its waters into the South Equatorial Current.
VI  WIND SYSTEMS
The outstanding wind systems of the Pacific Ocean are the twin belts of westerlies, which blow from west to east between 30° and 60° latitude, one in the northern hemisphere and one in the southern hemisphere. These winds vary in seasonal patterns. The stormy and unpredictable westerly of the North Central Pacific is being studied for its possible controlling effect on global weather patterns. Between the westerlies are the much more steady trade winds, which move from the east in the northern hemisphere and from the west in the southern hemisphere. Violent tropical storms, called typhoons in the western Pacific and hurricanes in the southern and eastern Pacific, originate in the trade wind belt in late summer and early autumn. At the equator are the equatorial doldrums, light winds with seasonal cyclonic activity. At the highest latitudes of the Pacific, the winds have little direct effect on climate and water currents.
RESOURCES
Much of the plant and animal life of the Pacific Ocean is concentrated along its margins. Nutrient-rich waters from the deep Antarctic Circumpolar Current upwell to the surface in the Peru Current along the coast of Chile and Peru, and the area sustains a large population of anchovetas that is of great importance as a world food resource. A large guano industry has been established from droppings of the seabirds that feed upon the anchovetas. The northwestern Pacific, including the Sea of Japan (East Sea) and the Sea of Okhotsk, is another major world fishery. Coral reefs rich with sea life reach their peak in the Great Barrier Reef, which extends for 2,010 km (1,250 mi) along the northeastern coast of Australia. Tuna is another important Pacific resource, bringing fleets of many nations in search of the schools that migrate over much of the ocean. The Pacific has also begun to be exploited for its vast mineral resources. The continental shelves off the coasts of California, Alaska, China, and the Indonesian area are known to contain large reserves of petroleum. Patches of the ocean floor are covered with “manganese nodules,” potato-sized concretions of iron and manganese oxides that sometimes also contain copper, cobalt, and nickel. Programs are under way to examine the feasibility of mining these deposits. See also Deep-Sea Exploration.
Arctic Ocean, smallest of the four world oceans. The Arctic Ocean extends south from the North Pole to the shores of Europe, Asia, and North America.
BOUNDARIES AND SIZE
The surface waters of the Arctic Ocean mingle with those of the Pacific Ocean through the Bering Strait, by way of a narrow and shallow channel, which has a depth of 55 m (180 ft). More importantly, the Arctic waters mix with those of the Atlantic Ocean across a system of submarine sills (shallow ridges) that span the great distances from Scotland to Greenland and from Greenland to Baffin Island at depths of 500 to 700 m (1,600 to 2,300 ft). Emptying into the Arctic Ocean are the Ob’, Yenisey, and Lena rivers in Asia and the Mackenzie River in North America. The total surface area of the Arctic Ocean is 14.1 million sq km (5.4 million sq mi). The major subdivisions of the Arctic Ocean include the Norwegian, Barents, Kara, Laptev, and Beaufort seas.
III  STRUCTURAL FEATURES
Approximately one-third of the Arctic Ocean is underlain by continental shelf, which includes a broad shelf north of Eurasia and the narrower shelves of North America and Greenland. Seaward of the continental shelves lies the Arctic Basin proper, which is subdivided into a set of three parallel ridges and four basins (also known as deeps). These features were discovered and explored beginning in the late 1940s. The Lomonosov Ridge, the major ridge, cuts the Arctic Basin almost in half, extending as a submarine bridge 1,800 km (1,100 mi) from Siberia to the northwestern tip of Greenland. Parallel to it are two shorter ridges: the Alpha Ridge on the North American side, defining the Canada and Makarov basins, and the Arctic Mid-Ocean Ridge on the Eurasian side, defining the Nansen and Amundsen basins. The average depth of the Arctic Ocean is only 1,300 m (4,300 ft) because of the vast shallow expanses on the continental shelves. The deepest point in the Arctic Ocean is 5,450 m (17,880 ft).
IV  ISLANDS
The islands of the Arctic Ocean lie on the continental shelves. To the northeast of Norway lies the archipelago of Svalbard (formerly known as Spitsbergen); to the east are Franz Josef Land, Novaya Zemlya, Severnaya Zemlya, the New Siberian Islands, and Wrangel Island, all of which are located north of Russia. The numerous islands of the Canadian Arctic Archipelago extend north and east from the Canadian mainland to Greenland, the largest island of the Arctic Ocean.
V  ICE
Three forms of ice are found in the Arctic Ocean: land ice, river ice, and sea ice. Land ice enters the ocean in the form of icebergs, which are created when pieces of glaciers break off. In the Arctic Ocean, icebergs are created primarily along the coasts of Greenland. The freezing of fresh water, and its subsequent transport into the ocean by rivers, produces nearshore concentrations of river ice over small areas of the Siberian and North American shelves. Sea ice is formed by the freezing of seawater. It is the most extensive form of ice in the Arctic Ocean. In winter a permanent cap of sea ice covers all of the ocean surface, except for the area northeast of Iceland and north of Scandinavia. In summer the ice cover shrinks to expose narrow bands of relatively open water along the coasts of most of Siberia, Alaska, and Canada. The ice cap is composed of pack ice—that is, pieces of ice that pile up and are pressed in ridges or hummocks that may be more than 10 m (30 ft) in depth.
VI  RESOURCES
Fish, in commercially exploitable quantities, are found only in the warmer marginal seas of the Arctic Ocean, notably in the Barents Sea (primarily cod). Sea mammals, including various species of seal and whale, were hunted to near extinction before being protected by quotas set during the 1900s. Tin is actively mined off the coast of eastern Siberia, and petroleum and natural gas are extracted north of Alaska and Canada.
Indian Ocean, third largest of Earth's four oceans, bounded on the west by Africa, on the north by Asia, on the east by Australia and the Australasian islands, and on the south by Antarctica. No natural boundary separates the Indian Ocean from the Atlantic Ocean, but a line 4,000 km (2,500 mi) long on the 20th meridian east of Greenwich, connecting Cape Agulhas at the southern end of Africa with Antarctica, is generally considered to be the boundary.
The total area of the Indian Ocean is 73.4 million sq km (28.4 million sq mi). The ocean narrows toward the north and is divided by the Indian peninsula into the Bay of Bengal on the east and the Arabian Sea on the west. The Arabian Sea sends two arms northward, the Persian Gulf and the Red Sea. The average depth of the Indian Ocean is 3,900 m (12,800 ft), or slightly greater than that of the Atlantic, and the deepest known point is 7,725 m (25,344 ft), off the southern coast of the Indonesian island of Java. In general, the greatest depths are in the northeastern sector of the ocean, where 130,000 sq km (50,000 sq mi) of the ocean floor lie at a depth of more than 5,500 m (18,000 ft).
The Indian Ocean contains numerous islands, the largest of which are Madagascar and Sri Lanka. Smaller islands include the Maldive group and Mauritius. From Africa the ocean receives the waters of the Limpopo and Zambezi rivers, and from Asia those of the Irrawaddy, Brahmaputra, Ganges, Indus, and Shatt al Arab rivers. As a rule, the winds over the Indian Ocean are gentle, with frequent extended periods of calm. Tropical storms occur occasionally, however, particularly near Mauritius, and the ocean is notable for seasonal winds called monsoons.
Atlantic Ocean, the second largest of the earth's four oceans and the most heavily traveled. Only the Pacific Ocean is larger, covering about twice the area of the Atlantic Ocean. The Atlantic is divided into two nominal sections: The part north of the equator is called the North Atlantic; the part south of the equator, the South Atlantic. The ocean's name is derived from Atlas, one of the Titans of Greek mythology.
 BOUNDARIES AND SIZE
The Atlantic Ocean is essentially an S-shaped north-south channel, extending from the Arctic Ocean in the north to the Antarctic continent in the south and situated between the eastern coast of the American continents and the western coasts of Europe and Africa. The Atlantic Ocean proper has a surface area of 82 million sq km (32 million sq mi). Including its marginal seas—the Gulf of Mexico-Caribbean Sea, the Arctic Ocean, and the North, Baltic, Mediterranean, and Black seas—the total area is 106 million sq km (41 million sq mi).
The boundary between the North Atlantic and the Arctic Ocean is arbitrarily designated as lying along a system of submarine ridges that extend between the land masses of Baffin Island, Greenland, and Scotland. More clearly defined is the boundary with the Mediterranean Sea at the Strait of Gibraltar and with the Caribbean Sea along the arc of the Antilles. The South Atlantic is arbitrarily separated from the Indian Ocean on the east by the 20° east meridian and from the Pacific on the west along the line of shallowest depth between Cape Horn and the Antarctic Peninsula.
III  GEOLOGIC FORMATION AND STRUCTURAL FEATURES
The Atlantic began to form during the Jurassic period, about 150 million years ago, when a rift opened up in the supercontinent of Gondwanaland, resulting in the separation of South America and Africa. The separation continues today at the rate of several centimeters a year along the Mid-Atlantic Ridge. Part of the midoceanic ridge system that girdles the world, it is a submarine ridge extending north to south in a sinuous path midway between the continents. Roughly 1,500 km (930 mi) wide, the ridge has a more rugged topography than any mountain range on land, and is a frequent site of volcanic eruptions and earthquakes. The ridge ranges from 1 to 3 km (0.6 to 2 mi) above the ocean bottom.
Along the American, Antarctic, African, and European coasts are the continental shelves—embankments of the debris washed from the continents. Submarine ridges and rises extend roughly east-west between the continental shelves and the Mid-Atlantic Ridge, dividing the eastern and western ocean floors into a series of basins, also known as abyssal plains. The three basins on the American side of the Mid-Atlantic Ridge are 5,000 m (16,000 ft) deep: the North American Basin, the Brazil Basin, and the Argentina Basin. The Eurafrican side is marked by several basins that are smaller but just as deep: the Iberia, Canaries, Cape Verde, Sierra Leone, Guinea, Angola, Cape, and Agulhas basins. The large Atlantic-Antarctic Basin lies between the southernmost extension of the Mid-Atlantic Ridge and the Antarctic continent.
The Atlantic Ocean has an average depth of 3,600 m (11,810 ft). At its deepest point, in the Puerto Rico Trench, the bottom is 8,605 m (28,231 ft) below the surface.
IV  ISLANDS
The largest islands of the Atlantic Ocean lie on the continental shelves. Newfoundland is the principal island on the North American shelf; the British Isles are the major island group of the Eurafrican shelf. Other continental islands include the Falkland Islands (Islas Malvinas), the only major group on the South American shelf, and the South Sandwich Islands on the Antarctic shelf.
Oceanic islands, usually of volcanic origin, are less common in the Atlantic Ocean than in the Pacific. Among these are the island arc of the Antilles (including Puerto Rico, Hispaniola, Jamaica, and Cuba). In the eastern Atlantic, the Madeiras, Canaries, Cape Verde, and the São Tomé-Príncipe group are the peaks of submarine ridges. The Azores, Saint Paul's Rocks, Ascension, and the Tristan da Cunha group are isolated peaks of the Mid-Atlantic Ridge system; the large island of Iceland is also the result of volcanic action at the Mid-Atlantic Ridge. Bermuda rises from the floor of the North American Basin, and Saint Helena from the Angola Basin.
V  CURRENTS
The circulatory system of the surface waters of the Atlantic can be depicted as two large gyres, or circular current systems, one in the North Atlantic and one in the South Atlantic. These currents are primarily wind driven, but are also affected by the rotation of the earth. The currents of the North Atlantic, which include the North Equatorial Current, the Canaries Current, and the Gulf Stream, flow in a clockwise direction. The currents in the South Atlantic, among which are the Brazil, Benguela, and South Equatorial currents, travel in a counterclockwise direction. Each gyre extends from near the equator to about latitude 45°; closer to the poles are the less completely defined counterrotating gyres, one rotating counterclockwise in the Arctic regions of the North Atlantic and one rotating clockwise near Antarctica in the South Atlantic. See Ocean and Oceanography: Ocean Currents.
The Atlantic receives the waters of many of the principal rivers of the world, among them the St. Lawrence, Mississippi, Orinoco, Amazon, Paraná, Congo, Niger, and Loire, and the rivers emptying into the North, Baltic, and Mediterranean seas. Nevertheless, primarily because of the high salinity of outflow from the Mediterranean, the Atlantic is slightly more saline than the Pacific or Indian oceans.
VI  TEMPERATURES
The Atlantic Ocean may be described as a bed of water colder than 9° C (48° F)—the cold-water sphere—within which lies a bubble of water warmer than 9° C—the warm-water sphere. The warm-water sphere extends between latitude 50° north and latitude 50° south and has an average thickness of 600 m (2,000 ft). The most active circulation is found in the uppermost layer of warm water. Below this, circulation becomes increasingly sluggish as the temperature decreases.
Surface temperatures range from 0° C (32° F), found year-round at the Arctic and Antarctic margins, to 27° C (81° F) in the broad belt at the equator. At depths below 2,000 m (6,600 ft), temperatures of 2° C (36° F) are prevalent; in bottom waters, below 4,000 m (13,200 ft), temperatures of -1° C (30° F) are common.
VII  MARINE RESOURCES
The Atlantic Ocean contains some of the world's most productive fisheries, located on the continental shelves and marine ridges off the British Isles, Iceland, Canada (especially the Grand Banks off Newfoundland), and the northeastern United States. Upwelling areas, in which the nutrient-rich waters of the ocean depths flow up to the surface, as in the vicinity of Walvis Bay off southwestern Africa, also have abundant sea life. Herring, anchovy, sardine, cod, flounder, and perch are the most important commercial species. Tuna is taken off northwestern Africa and northeastern South America in increasing numbers. The catch per unit area is much higher in the Atlantic than in the other oceans.
A remarkable example of plant life is found in the Sargasso Sea, the oval section of the North Atlantic lying between the West Indies and the Azores and bounded on the west and north by the Gulf Stream. Here extensive patches of brown gulfweed (Sargassum) are found on the relatively still surface waters.
Actively mined mineral resources in the Atlantic include titanium, zircon, and monazite (phosphates of the cerium metals), off the eastern coast of Florida, and tin and iron ore, off the equatorial coast of Africa. The continental shelves and slopes of the Atlantic are potentially very rich in fossil fuels. Large amounts of petroleum are already being extracted in the North Sea and in the Caribbean Sea-Gulf of Mexico region; lesser amounts are extracted off the coast of Africa in the Gulf of Guinea.