The Indian Ocean is bounded by Iran, Pakistan, India, and Bangladesh to the north; the Malay Peninsula, the Sunda Islands of Indonesia, and Australia to the east; Antarctica to the south; and Africa and the Arabian Peninsula to the west. In the southwest it joins the Atlantic Ocean south of the southern tip of Africa, and to the east and southeast its waters mingle with the ones of the Pacific Ocean.
The question of defining the oceanic limits of the Indian Ocean is complicated and stays unsettled. The clearest border and the one most usually agreed upon is that with the Atlantic Ocean, which runs from Cape Agulhas, on the southern tip of Africa, due south alongside the 20° E meridian to the beaches of Antarctica. The border with the Pacific Ocean to the southeast is typically drawn from South East Cape at the island of Tasmania south alongside the 147° E meridian to Antarctica. Bass Strait, between Tasmania and Australia, is considered by way of some to be part of the Indian Ocean and with the aid of others to be a part of the Pacific. The northeastern border is the maximum difficult to outline. The one maximum generally agreed upon runs northwest from Cape Londonderry in Australia throughout the Timor Sea, along the southern shorelines of the Lesser Sunda Islands and of Java, after which throughout the Sunda Strait to the beaches of the island of Sumatra. Between Sumatra and the Malay Peninsula the boundary is commonly drawn across the Singapore Strait.
There is no common settlement on the southern restrict of the Indian Ocean. In fashionable (and for the functions of this newsletter), it's miles described as extending southward to the coast of Antarctica. However, many—significantly in Australia—don't forget the element closest to Antarctica (at the side of the corresponding southern extensions of the Atlantic and Pacific) to be part of the Southern (or Antarctic) Ocean. Australians regularly name the complete expanse south of that continent’s south coast the Southern Ocean.
The Indian Ocean has the fewest marginal seas of the principal oceans. To the north are the inland Red Sea and Persian Gulf. The Arabian Sea is to the northwest, and the Andaman Sea to the northeast. The massive gulfs of Aden and Oman are to the northwest, the Bay of Bengal is to the northeast, and the Great Australian Bight is off the southern coast of Australia.
The Indian Ocean differs from the Atlantic and Pacific Oceans in several other respects. In the Northern Hemisphere it's far landlocked and does no longer amplify to Arctic waters or have a temperate-to-bloodless area. It has fewer islands and narrower continental cabinets. It is the handiest ocean with an asymmetric and, in the north, semiannually reversing surface circulation. It has no separate source of bottom water (i.E., the Indian Ocean’s backside water originates outside its barriers) and has assets of exceptionally saline water (the Persian Gulf and the Red Sea). Below the floor layers, especially within the north, the sea’s water is extraordinarily low in oxygen.
Origin
The starting place and evolution of the Indian Ocean is the most complicated of the three major oceans. Its formation is a result of the breakup, which began about one hundred eighty million years in the past, of the southern supercontinent Gondwana (or Gondwanaland); by using the motion to the northeast of the Indian subcontinent (starting approximately one hundred twenty five million years in the past), which started out colliding with Eurasia approximately 50 million years in the past; and by means of the western movement of Africa and separation of Australia from Antarctica some 53 million years in the past. By 36 million years ago, the Indian Ocean had taken on its gift configuration. Although it first opened some one hundred forty million years in the past, nearly all the Indian Ocean basin is much less than eighty million years old.
Submarine features
Oceanic ridges and fracture zones
The oceanic ridges include a rugged, seismically active mountain chain this is part of the global oceanic ridge device and nevertheless incorporates centres of seafloor spreading in numerous locations. The ridges shape an inverted Y on the sea floor, starting in the top northwest with the Carlsberg Ridge in the Arabian Sea, turning due south past the Chagos-Laccadive Plateau, and becoming the Mid-Indian (or Central Indian) Ridge. Southeast of Madagascar the ridge branches: the Southwest Indian Ridge keeps to the southwest till it merges into the Atlantic-Indian Ridge south of Africa, and the Southeast Indian Ridge traits to the east until it joins the Pacific-Antarctic Ridge south of Tasmania. Most hanging is the aseismic (sincerely earthquake-unfastened) Ninetyeast Ridge, that is the longest and straightest in the global ocean. First determined in 1962, it runs northward alongside the ninety° E meridian (subsequently its call) for 2,800 miles (4,500 km) from the zonal Broken Ridge at latitudes 31° S to nine° N and may be traced farther under the sediments of the Bay of Bengal. Other crucial meridional aseismic ridges include the Chagos-Laccadive, Madagascar, and Mozambique plateaus, which aren't part of the global oceanic ridge gadget.
The fracture zones of the Indian Ocean offset the axis of the oceanic ridges frequently in a north-south course. Prominent are the Owen, Prince Edward, Vema, and Amsterdam fracture zones alongside the ridges, with the monstrous Diamantina Fracture Zone determined to the southwest of Australia.
Seamounts
Seamounts are extinct submarine volcanoes that are conically fashioned and frequently flat-crowned. They upward push all of sudden from the abyssal undeniable to heights as a minimum 3,300 toes (1,000 metres) above the ocean floor. In the Indian Ocean, seamounts are especially considerable between Réunion and Seychelles inside the Central Indian Basin and the Vening Meinesz group near Wharton Basin. Bardin, Kohler, Nikitin, and Williams seamounts are examples.
Ocean basins
Ocean basins are characterized by smooth, flat plains of thick sediment with abyssal hills (i.E., functions that are less than three,three hundred toes excessive) at the lowest flanks of the oceanic ridges. The Indian Ocean’s complex ridge topography caused the formation of many basins that range in width from 200 to five,six hundred miles (320 to nine,000 km). From roughly north to south they include the Arabian, Somali, Mascarene, Madagascar, Mozambique, Agulhas, and Crozet basins in the west and the Central Indian (the largest), Wharton, and South Australia basins within the east.
Continental upward thrust, slope, and shelf
The continental shelf extends to a median width of approximately 75 miles (120 km) within the Indian Ocean, with its widest factors (one hundred ninety miles [300 km]) off Mumbai (Bombay) at the western coast of India and rancid northwestern Australia. The island shelves are most effective approximately 1,000 toes (300 metres) wide. The shelf spoil is at a depth of about 460 feet (140 metres). Submarine canyons indent the steep slope beneath the smash. The Ganges (Ganga) and Indus rivers of Asia and the Zambezi River of Africa have all carved particularly huge canyons. Their sediment hundreds extend a ways beyond the shelf, form the rises at the foot of the slope, and make contributions to the abyssal plains of their respective basins. The Ganges sediment cone is the world’s widest and thickest.
Trenches
The Indian Ocean has the fewest trenches of any of the world’s oceans. The slim (50 miles [80 km]), volcanic, and seismically active Java Trench is the arena’s 2d longest, stretching extra than 2,800 miles (four,500 km) from southwest of Java and continuing northward as the Sunda Trench beyond Sumatra, with an extension along the Andaman and Nicobar Islands. The part of that device adjoining to Sumatra turned into the centre of a large undersea earthquake in 2004 (magnitude nine.1) that affected a few 600 miles (1,000 km) of the associated fault quarter. A series of devastating tsunamis generated via the quake swamped coastal cities, mainly in Indonesia, and reached to the northern stop of the Bay of Bengal and as a ways as the Indian Ocean’s western shorelines.
No comments:
Post a Comment