The Indian Ocean is the third largest of the world's oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) (approximately 20% of the water on the Earth's surface). It is bounded by Asia on the north, on the west by Africa, on the east by Australia, and on the south by the Southern Ocean or, depending on definition, by Antarctica.
Extent of the Indian Ocean according to The World Factbook
The ocean-floor of the Indian Ocean is divided by spreading ridges and crisscrossed by aseismic structures
|Location||Indian subcontinent, Southeast Asia, Western Asia, Northeast Africa, East Africa, Southern Africa and Australia|
|Max. width||6,200 mi (10,000 km)|
|Surface area||68,556,000 km2 (26,470,000 sq mi)|
|Average depth||3,741 m (12,274 ft)|
|Max. depth||7,258 m (23,812 ft)|
|Settlements||Durban, Mumbai, Perth, Colombo, Padang, Maputo|
The Indian Ocean is named after India. Called the Sindhu Mahasagara or the great sea of the Sindhu by the Ancient Indians, this ocean has been variously called Hindu Ocean, Indic Ocean, etc. in various languages. The Indian Ocean was also known earlier as the Eastern Ocean. The term was still in use during the mid-18th century.
The borders of the Indian Ocean, as delineated by the International Hydrographic Organization in 1953 included the Southern Ocean but not the marginal seas along the northern rim, but in 2000 the IHO delimited the Southern Ocean separately, which removed waters south of 60°S from the Indian Ocean, but included the northern marginal seas.  Meridionally, the Indian Ocean is delimited from the Atlantic Ocean by the 20° east meridian, running south from Cape Agulhas, and from the Pacific Ocean by the meridian of 146°49'E, running south from the southernmost point of Tasmania. The northernmost extent of the Indian Ocean (including marginal seas) is approximately 30° north in the Persian Gulf.
The Indian Ocean covers 70,560,000 km2 (27,240,000 sq mi), including the Red Sea and the Persian Gulf but excluding the Southern Ocean, or 19.5% of the world's oceans; its volume is 264,000,000 km3 (63,000,000 cu mi) or 19.8% of the world's oceans' volume; it has an average depth of 3,741 m (12,274 ft) and a maximum depth of 7,906 m (25,938 ft).
The ocean's continental shelves are narrow, averaging 200 kilometres (120 mi) in width. An exception is found off Australia's western coast, where the shelf width exceeds 1,000 kilometres (620 mi). The average depth of the ocean is 3,890 m (12,762 ft). Its deepest point is Sunda Trench at a depth of 7,450 m (24,442 ft); Diamantina Deep has a depth of 7,079 m (23,225 ft). North of 50° south latitude, 86% of the main basin is covered by pelagic sediments, of which more than half is globigerina ooze. The remaining 14% is layered with terrigenous sediments. Glacial outwash dominates the extreme southern latitudes.
The major choke points include Bab el Mandeb, Strait of Hormuz, the Lombok Strait, the Strait of Malacca and the Palk Strait. Seas include the Gulf of Aden, Andaman Sea, Arabian Sea, Bay of Bengal, Great Australian Bight, Laccadive Sea, Gulf of Mannar, Mozambique Channel, Gulf of Oman, Persian Gulf, Red Sea and other tributary water bodies. The Indian Ocean is artificially connected to the Mediterranean Sea through the Suez Canal, which is accessible via the Red Sea. All of the Indian Ocean is in the Eastern Hemisphere and the centre of the Eastern Hemisphere, the 90th meridian east, passes through the Ninety East Ridge.
Several features make the Indian Ocean unique. It constitutes the core of the large-scale Tropical Warm Pool which, when interacting with the atmosphere, affects the climate both regionally and globally. Asia blocks heat export and prevents the ventilation of the Indian Ocean thermocline. That continent also drives the Indian Ocean monsoon, the strongest on Earth, which causes large-scale seasonal variations in ocean currents, including the reversal of the Somali Current and Indian Monsoon Current. Because of the Indian Ocean Walker circulation there is no continuous equatorial easterlies. Upwelling occurs near the Horn of Africa and the Arabian Peninsula in the Northern Hemisphere and north of the trade winds in the Southern Hemisphere. The Indonesian Throughflow is a unique Equatorial connection to the Pacific.
The climate north of the equator is affected by a monsoon climate. Strong north-east winds blow from October until April; from May until October south and west winds prevail. In the Arabian Sea the violent Monsoon brings rain to the Indian subcontinent. In the southern hemisphere, the winds are generally milder, but summer storms near Mauritius can be severe. When the monsoon winds change, cyclones sometimes strike the shores of the Arabian Sea and the Bay of Bengal.
The Indian Ocean is the warmest ocean in the world. Long-term ocean temperature records show a rapid, continuous warming in the Indian Ocean, at about 0.7–1.2 °C (1.3–2.2 °F) during 1901–2012. Indian Ocean warming is the largest among the tropical oceans, and about 3 times faster than the warming observed in the Pacific. Research indicates that human induced greenhouse warming, and changes in the frequency and magnitude of El Niño events are a trigger to this strong warming in the Indian Ocean.
Among the few large rivers flowing into the Indian Ocean are the Zambezi and Jubba in Africa; the Shatt al-Arab in the Persian Gulf; the Indus and Ganges-Brahmaputra, Godavari, Krishna, and Narmada on the Indian Subcontinent; and Irrawaddy in Myanmar.
The ocean's currents are mainly controlled by the monsoon. Two large gyres, one in the northern hemisphere flowing clockwise and one south of the equator moving anticlockwise (including the Agulhas Current and Agulhas Return Current), constitute the dominant flow pattern. During the winter monsoon (November–February), however, circulation is reversed north of 30°S and winds are weakened during winter and the transitional periods between the monsoons.
Deep water circulation is controlled primarily by inflows from the Atlantic Ocean, the Red Sea, and Antarctic currents. North of 20° south latitude the minimum surface temperature is 22 °C (72 °F), exceeding 28 °C (82 °F) to the east. Southward of 40° south latitude, temperatures drop quickly.
Precipitation and evaporation leads to salinity variation in all oceans, and in the Indian Ocean salinity variations are driven by: (1) river inflow mainly from the Bay of Bengal, (2) fresher water from the Indonesian Throughflow; and (3) saltier water from the Red Sea and Persian Gulf. Surface water salinity ranges from 32 to 37 parts per 1000, the highest occurring in the Arabian Sea and in a belt between southern Africa and south-western Australia. Pack ice and icebergs are found throughout the year south of about 65° south latitude. The average northern limit of icebergs is 45° south latitude.
Left: The oldest ocean floor of the Indian Ocean formed c. 150 Ma when the Indian Subcontinent and Madagascar broke-up from Africa. Right: The India–Asia collision c. 40 Ma completed the closure of the Tethys Ocean (grey areas north of India).
As the youngest of the major oceans, the Indian Ocean has active spreading ridges that are part of the worldwide system of mid-ocean ridges. In the Indian Ocean these spreading ridges meet at the Rodrigues Triple Point with the Central Indian Ridge, including the Carlsberg Ridge, separating the African Plate from the Indian Plate; the Southwest Indian Ridge separating the African Plate from the Antarctic Plate; and the Southeast Indian Ridge separating the Australian Plate from the Antarctic Plate. The Central Indian Ridge is intercepted by the Owen Fracture Zone.
A series of ridges and seamount chains produced by hotspots pass over the Indian Ocean. The Réunion hotspot (active 70–40 million years ago) connects Réunion and the Mascarene Plateau to the Chagos-Laccadive Ridge and the Deccan Traps in north-western India; the Kerguelen hotspot (100–35 million years ago) connects the Kerguelen Islands and Kerguelen Plateau to the Ninety East Ridge and the Rajmahal Traps in north-eastern India; the Marion hotspot (100–70 million years ago) possibly connects Prince Edward Islands to the Eighty Five East Ridge. These hotspot tracks have been broken by the still active spreading ridges mentioned above.
The opening of the Indian Ocean began c. 156 Ma when Africa separated from East Gondwana. The Indian Subcontinent began to separate from Australia-Antarctica 135-125 Ma and as the Tethys Ocean north of India began to close 118-84 Ma the Indian Ocean opened behind it.
Among the tropical oceans, the western Indian Ocean hosts one of the largest concentration of phytoplankton blooms in summer, due to the strong monsoon winds. The monsoonal wind forcing leads to a strong coastal and open ocean upwelling, which introduces nutrients into the upper zones where sufficient light is available for photosynthesis and phytoplankton production. These phytoplankton blooms support the marine ecosystem, as the base of the marine food web, and eventually the larger fish species. The Indian Ocean accounts for the second largest share of the most economically valuable tuna catch. Its fish are of great and growing importance to the bordering countries for domestic consumption and export. Fishing fleets from Russia, Japan, South Korea, and Taiwan also exploit the Indian Ocean, mainly for shrimp and tuna.
Research indicates that increasing ocean temperatures are taking a toll on the marine ecosystem. A study on the phytoplankton changes in the Indian Ocean indicates a decline of up to 20% in the marine phytoplankton in the Indian Ocean, during the past six decades. The tuna catch rates have also declined abruptly during the past half century, mostly due to increased industrial fisheries, with the ocean warming adding further stress to the fish species.
An Indian Ocean garbage patch was discovered in 2010 covering at least 5 million square kilometres (1.9 million square miles). Riding the southern Indian Ocean Gyre, this vortex of plastic garbage constantly circulates the ocean from Australia to Africa, down the Mozambique Channel, and back to Australia in a period of six years, except for debris that get indefinitely stuck in the centre of the gyre.
The garbage patch in the Indian Ocean will, according to a 2012 study, decrease in size after several decades to vanish completely over centuries. Over several millennia, however, the global system of garbage patches will accumulate in the North Pacific.
In 2016, UK researchers from Southampton University identified six new animal species at hydrothermal vents beneath the Indian Ocean. These new species were a "Hoff" crab, a "giant peltospirid" snail, a whelk-like snail, a limpet, a scaleworm and a polychaete worm.
Human culture spread early on the shores of the Indian Ocean and was always linked to the cultures of the Mediterranean and Persian Gulf. Before c. 2000 BCE, however, cultures on its shores were only loosely tied to each other; bronze, for example, was developed in Mesopotamia 5000–3500 BCE but remained uncommon in Egypt before 800 BCE.
The history of the Indian Ocean is marked by maritime trade; cultural and commercial exchange probably date back at least seven thousand years. During this period, independent, short-distance oversea communications along its littoral margins have evolved into an all-embracing network. The début of this network was not the achievement of a centralised or advanced civilisation but of local and regional exchange in the Persian Gulf, the Red Sea, and Arabian Sea. Sherds of Ubaid (2500–500 BCE) pottery have been found in the western Gulf at Dilmun, present-day Bahrain; traces of exchange between this trading centre and Mesopotamia. The Sumerians traded grain, pottery, and bitumen (used for reed boats) for copper, stone, timber, tin, dates, onions, and pearls. Coast-bound vessels transported goods between the Indus Valley Civilisation (2600–1900 BCE) in the Indian subcontinent (modern-day Pakistan and Northwest India) and the Persian Gulf and Egypt.
Periplus of the Erythraean Sea, an Alexandrian guide to the world beyond the Red Sea — including Africa and India — from the first century CE, not only gives insights into trade in the region but also shows that Roman and Greek sailors had already gained knowledge about the monsoon winds. The contemporaneous settlement of Madagascar by Austronesian sailors shows that the littoral margins of the Indian Ocean were being both well-populated and regularly traversed at least by this time. Albeit the monsoon must have been common knowledge in the Indian Ocean for centuries.
The world's earliest civilizations in Mesopotamia (beginning with Sumer), ancient Egypt, and the Indian subcontinent (beginning with the Indus Valley civilization), which began along the valleys of the Tigris-Euphrates, Nile and Indus rivers respectively, all developed around the Indian Ocean. Civilizations soon arose in Persia (beginning with Elam) and later in Southeast Asia (beginning with Funan).
During Egypt's first dynasty (c. 3000 BCE), sailors were sent out onto its waters, journeying to Punt, thought to be part of present-day Somalia. Returning ships brought gold and slaves. The earliest known maritime trade between Mesopotamia and the Indus Valley (c. 2500 BCE) was conducted along the Indian Ocean. Phoenicians of the late 3rd millennium BCE may have entered the area, but no settlements resulted.
The Indian Ocean's relatively calmer waters opened the areas bordering it to trade earlier than the Atlantic or Pacific oceans. The powerful monsoons also meant ships could easily sail west early in the season, then wait a few months and return eastwards. This allowed ancient Indonesian peoples to cross the Indian Ocean to settle in Madagascar around 1 CE.
In the 2nd or 1st century BCE, Eudoxus of Cyzicus was the first Greek to cross the Indian Ocean. The probably fictitious sailor Hippalus is said to have learnt the direct route from Arabia to India around this time. During the 1st and 2nd centuries AD intensive trade relations developed between Roman Egypt and the Tamil kingdoms of the Cheras, Cholas and Pandyas in Southern India. Like the Indonesian peoples above, the western sailors used the monsoon to cross the ocean. The unknown author of the Periplus of the Erythraean Sea describes this route, as well as the commodities that were traded along various commercial ports on the coasts of the Horn of Africa and India circa 1 CE. Among these trading settlements were Mosylon and Opone on the Red Sea littoral.
Unlike the Pacific Ocean where the civilization of the Polynesians reached most of the far flung islands and atolls and populated them, almost all the islands, archipelagos and atolls of the Indian Ocean were uninhabited until colonial times. Although there were numerous ancient civilizations in the coastal states of Asia and parts of Africa, the Maldives were the only island group in the Central Indian Ocean region where an ancient civilization flourished. Maldivian ships used the Indian Monsoon Current to travel to the nearby coasts.
The Rub' al Khali desert isolates the southern parts of the Arabic Peninsula and the Indian Ocean from the Arabic world. This encouraged the development of maritime trade in the region linking the Red Sea and the Persian Gulf to East Africa and India. The monsoon (from mawsim, the Arabic word for season), however, was used by sailors long before being "discovered" by Hippalus in the 1st century. Indian wood have been found in Sumerian cities, there is evidence of Akkad coastal trade in the region, and contacts between India and the Red Sea dates back to the 2300 B.C.. The archipelagoes of the central Indian Ocean, the Laccadive and Maldive islands, were probably populated during in the 2nd century B.C. from the Indian mainland. They appear in written history in the account of merchant Sulaiman al-Tajir in the 9th century but the treacherous reefs of the islands were most likely cursed by the sailors of Aden long before the islands were even settled.
Arabic missionaries and merchants began to spread Islam along the eastern shores of the Indian Ocean from the 8th century, if not earlier. A Swahili stone mosque dating to the 8th-15th centuries have been found in Shanga, Kenya. Trade across the Indian Ocean gradually introduced Arabic script and rice as a staple in Eastern Africa.
From 1405 to 1433 admiral Zheng He said to have led large fleets of the Ming Dynasty on several treasure voyages through the Indian Ocean, ultimately reaching the coastal countries of East Africa.
In 1497 Portuguese navigator Vasco da Gama rounded the Cape of Good Hope and became the first European to sail to India (with the help of an Indian sailor) and later the Far East. The European ships, armed with heavy cannon, quickly dominated trade. Portugal achieved pre-eminence by setting up forts at the important straits and ports. Their hegemony along the coasts of Africa and Asia lasted until the mid 17th century. Later, the Portuguese were challenged by other European powers.
The Dutch East India Company (1602–1798) sought control of trade with the East across the Indian Ocean. France and Britain established trade companies for the area. From 1565 Spain established a major trading operation with the Manila Galleons in the Philippines and the Pacific. Spanish trading ships purposely avoided the Indian Ocean, following the Treaty of Tordesillas with Portugal. By 1815, Britain became the principal power in the Indian Ocean.
The opening of the Suez Canal in 1869 revived European interest in the East, but no nation was successful in establishing trade dominance. Since World War II the United Kingdom was forced to withdraw from the area, to be replaced by India, the USSR, and the United States. The last two tried to establish hegemony by negotiating for naval base sites. Developing countries bordering the ocean, however, seek to have it made a "zone of peace" so that they may use its shipping lanes freely. The United Kingdom and United States maintain a military base on Diego Garcia atoll in the middle of the Indian Ocean.
On 26 December 2004 fourteen countries around the Indian Ocean were hit by a wave of tsunamis caused by the 2004 Indian Ocean earthquake. The waves radiated across the ocean at speeds exceeding 500 km/h (310 mph), reached up to 20 m (66 ft) in height, and resulted in an estimated 236,000 death.
In the late 2000s the ocean evolved into a hub of pirate activity. By 2013, attacks off the Horn region's coast had steadily declined due to active private security and international navy patrols, especially by the Indian Navy.
Malaysian Airlines Flight 370, a Boeing 777 airliner with 239 persons on board, disappeared on 8 March 2014 and is alleged to have crashed into the southeastern Indian Ocean about 2,000 km (1,200 mi) from the coast of southwest Western Australia. Despite an extensive search, the whereabouts of the remains of the aircraft are unknown.
The sea lanes in the Indian Ocean are considered among the most strategically important in the world with more than 80 percent of the world's seaborne trade in oil transits through Indian Ocean and its vital choke points, with 40 percent passing through the Strait of Hormuz, 35 percent through the Strait of Malacca and 8 percent through the Bab el-Mandab Strait.
The Indian Ocean provides major sea routes connecting the Middle East, Africa, and East Asia with Europe and the Americas. It carries a particularly heavy traffic of petroleum and petroleum products from the oil fields of the Persian Gulf and Indonesia. Large reserves of hydrocarbons are being tapped in the offshore areas of Saudi Arabia, Iran, India, and Western Australia. An estimated 40% of the world's offshore oil production comes from the Indian Ocean. Beach sands rich in heavy minerals, and offshore placer deposits are actively exploited by bordering countries, particularly India, Pakistan, South Africa, Indonesia, Sri Lanka, and Thailand.
Chinese companies have made investments in several Indian Ocean ports, including Gwadar, Hambantota, Colombo and Sonadia. This has sparked a debate about the strategic implications of these investments.
ocean E of Africa, S of Asia, W of Australia, & N of Antarctica area ab 73,427,795 square kilometres (28,350,630 sq mi)
The 2004 Indian Ocean earthquake occurred at 00:58:53 UTC on 26 December, with an epicentre off the west coast of northern Sumatra. It was an undersea megathrust earthquake that registered a magnitude of 9.1–9.3 Mw, reaching a Mercalli intensity up to IX in certain areas. The earthquake was caused by a rupture along the fault between the Burma Plate and the Indian Plate.
A series of large tsunamis up to 30 metres (100 ft) high were created by the underwater seismic activity that became known collectively as the Boxing Day tsunamis. Communities along the surrounding coasts of the Indian Ocean were seriously affected, and the tsunamis killed an estimated 227,898 people in 14 countries. The Indonesian city of Banda Aceh reported the largest number of victims. The earthquake was one of the deadliest natural disasters in recorded history. The direct results caused major disruptions to living conditions and commerce particularly in Indonesia, Sri Lanka, India, and Thailand.
The earthquake was the third largest ever recorded and had the longest duration of faulting ever observed; between eight and ten minutes. It caused the planet to vibrate as much as 1 centimetre (0.4 inches), and it remotely triggered earthquakes as far away as Alaska. Its epicentre was between Simeulue and mainland Sumatra. The plight of the affected people and countries prompted a worldwide humanitarian response, with donations totaling more than US$14 billion. The event is known by the scientific community as the Sumatra–Andaman earthquake.British Indian Ocean Territory
The British Indian Ocean Territory (BIOT) is an overseas territory of the United Kingdom situated in the Indian Ocean halfway between Tanzania and Indonesia, and directly south of the Maldives. The territory comprises the seven atolls of the Chagos Archipelago with over 1,000 individual islands – many very small – amounting to a total land area of 60 square kilometres (23 sq mi). The largest and most southerly island is Diego Garcia, 27 km2 (10 sq mi), the site of a joint military facility of the United Kingdom and the United States.
The only inhabitants of the territory are US and British military personnel and associated contractors, who collectively number around 2,500 (2012 figures). The removal of Chagossians from the Chagos Archipelago occurred between 1968 and 1973. The Chagossians, then numbering about 2,000 people, were expelled by the British government to Mauritius and the Seychelles to allow the United States to build a joint UK/US military base there. Today, the exiled Chagossians are still trying to return, arguing that the forced expulsion and dispossession was illegal. The islands are off-limits to Chagossians, casual tourists, and the media.
Since the 1980s the government of Mauritius has sought to regain control over the Chagos Archipelago, which was separated from the British Colony of Mauritius by the UK in 1965 to form the British Indian Ocean Territory. On 23 June 2017, the United Nations General Assembly (UNGA) voted in favour of referring the territorial dispute between Mauritius and the UK to the International Court of Justice (ICJ) in order to clarify the legal status of the Chagos Islands archipelago in the Indian Ocean. The motion was approved by a majority vote with 94 voting for and 15 against.. Judge Abdulqawi Ahmed Yusuf described the UK's administration of the Chagos Islands as "an unlawful act of continuing character". In February 2019, the International Court of Justice in The Hague ruled that Britain should transfer the islands to Mauritius as they were not legally separated from the latter in 1965. The ruling is not legally binding.Chagos Archipelago
The Chagos Archipelago () or Chagos Islands (formerly the Bassas de Chagas, and later the Oil Islands) are a group of seven atolls comprising more than 60 individual tropical islands in the Indian Ocean about 500 kilometres (310 mi) south of the Maldives archipelago. This chain of islands is the southernmost archipelago of the Chagos-Laccadive Ridge, a long submarine mountain range in the Indian Ocean.Officially a colonized territory by the United Kingdom, as part of its British Indian Ocean Territory, the Chagos were home to the Chagossians, a Bourbonnais Creole-speaking people, for more than a century and a half until the United Kingdom evicted them between 1967 and 1973 to allow the United States to build a military base on Diego Garcia, the largest of the Chagos Islands. Since 1971, only the atoll of Diego Garcia is inhabited, and only by military and civilian contracted personnel.
The sovereignty of the Chagos Archipelago was disputed between the UK and Mauritius. The United Kingdom excised the archipelago from Mauritian territory in 1965, three years before Mauritius gained independence in 1968. On 25 February 2019, the International Court of Justice (ICJ) ruled that the United Kingdom should relinquish the archipelago. The British government rejected any jurisdiction of the court to deliberate these matters.Christmas Island
The Territory of Christmas Island is an Australian external territory comprising the island of the same name. Christmas Island is located in the Indian Ocean, around 350 kilometres (220 mi) south of Java and Sumatra and around 1,550 kilometres (960 mi) north-west of the closest point on the Australian mainland. It has an area of 135 square kilometres (52 sq mi).
Christmas Island had a population of 1,843 residents as of 2016, the majority of whom live in settlements on the northern tip of the island. The main settlement is Flying Fish Cove. Around two-thirds of the island's population is estimated to have Malaysian Chinese origin (though just 21.2% of the population declared a Chinese ancestry in 2016), with significant numbers of Malays and European Australians as well as smaller numbers of Malaysian Indians and Eurasians. Several languages are in use, including English, Malay, and various Chinese dialects. Islam and Buddhism are major religions on the island, though a vast majority of the population does not declare a formal religious affiliation and may be involved in ethnic Chinese religion.
The first European to sight the island was Richard Rowe of the Thomas in 1615. The island was later named on Christmas Day (25 December) 1643 by Captain William Mynors but only settled in the late 19th century. Its geographic isolation and history of minimal human disturbance has led to a high level of endemism among its flora and fauna, which is of interest to scientists and naturalists. The majority (63 percent) of the island is included in the Christmas Island National Park, which features several areas of primary monsoonal forest. Phosphate, deposited originally as guano, has been mined on the island since 1899.Diego Garcia
Diego García is an atoll just south of the equator in the central Indian Ocean, and the largest of 60 small islands comprising the Chagos Archipelago. It was first discovered and named by the Portuguese, settled by the French in the 1790s and transferred to British rule after the Napoleonic Wars. It was one of the "Dependencies" of the British Colony of Mauritius until it was detached for inclusion in the newly created British Indian Ocean Territory (BIOT) in 1965.
Between 1968 and 1973, the population was forcibly removed by the United Kingdom and the United States to establish an American base through intimidation of locals and denying the return of any who left the island. Many were deported to Mauritius and the Seychelles, following which the United States built a large naval and military base, which has been in continuous operation since then. As of August 2018, Diego Garcia is the only inhabited island of the BIOT; the population is composed of military personnel and supporting contractors. It is one of two critical US bomber bases in the Asia Pacific region, along with Andersen Air Force Base, Guam, Pacific Ocean.The atoll is located 3,535 km (2,197 mi) east of Tanzania's coast, 1,796 km (1,116 mi) south-southwest of the southern tip of India (at Kanyakumari) and 4,723 km (2,935 mi) west-northwest of the west coast of Australia (at Cape Range National Park, Western Australia). Diego Garcia lies at the southernmost tip of the Chagos-Laccadive Ridge, a vast underwater mountain range, top of coral reefs, atolls, and islands comprising Lakshadweep, The Maldives, and the Chagos Archipelago. Local time is UTC+6 year-round (DST is not observed).On 23 June 2017, the United Nations General Assembly (UNGA) voted in favour of referring the territorial dispute between Mauritius and the UK to the International Court of Justice (ICJ) in order to clarify the legal status of the Chagos Islands archipelago in the Indian Ocean. The motion was approved by a majority vote with 94 voting for and 15 against.In February 2019, the International Court of Justice in The Hague ruled that the United Kingdom must transfer the islands to Mauritius as they were not legally separated from the latter in 1965. The ruling is not legally binding.Football at the Indian Ocean Island Games
The association football tournament at the Indian Ocean Island Games (French: Jeux des îles de l'océan Indien) which is organised every 4 years for the Islands in the Indian Ocean. (The Maldives have occasionally been invited)
From 1947 until 1963 a precursor called Triangulaire was organized between Madagascar, Mauritius and Réunion Island. The first official edition of Indian Ocean Island Games was held in 1979.Gulf of Aden
The Gulf of Aden, formerly known as the Gulf of Berbera, is a gulf amidst Yemen to the north, the Arabian Sea and Guardafui Channel to the east, Somalia to the south, and Djibouti to the west. In the northwest, it connects with the Red Sea through the Bab-el-Mandeb strait, and in the southeast, it connects with the Indian Ocean through the Guardafui Channel.The waterway is part of the important Suez Canal shipping route between the Mediterranean Sea and the Arabian Sea in the Indian Ocean, with 21,000 ships crossing the gulf annually.Indian-Ocean Rim Association
The Indian Ocean Rim Association (IORA), formerly known as the Indian Ocean Rim Initiative and Indian Ocean Rim Association for Regional Cooperation (IOR-ARC), is an international organisation consisting of coastal states bordering the Indian Ocean. The IORA is a regional forum, tripartite in nature, bringing together representatives of Government, Business and Academia, for promoting co-operation and closer interaction among them. It is based on the principles of Open Regionalism for strengthening Economic Cooperation particularly on Trade Facilitation and Investment, Promotion as well as Social Development of the region. The Coordinating Secretariat of IORA is located at Ebene, Mauritius.Indian Ocean raid
The Indian Ocean raid (known in Japan as Operation C) was a naval sortie by the fast carrier strike force of the Imperial Japanese Navy from 31 March to 10 April 1942 against Allied shipping and bases in the Indian Ocean. It was an early engagement of the Pacific campaign of World War II. The Japanese under Chūichi Nagumo compelled part of the Allied (largely Royal Navy) forces to retreat to East Africa, but Admiral Sir James Somerville kept his fast carrier division, Force A, "...in Indian waters, to be ready to deal with any attempt by the enemy to command those waters with light forces only."Indo-Pacific
The Indo-Pacific, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, is a biogeographic region of Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia. It does not include the temperate and polar regions of the Indian and Pacific oceans, nor the Tropical Eastern Pacific, along the Pacific coast of the Americas, which is also a distinct marine realm.
The term is especially useful in marine biology, ichthyology, and similar fields, since many marine habitats are continuously connected from Madagascar to Japan and Oceania, and a number of species occur over that range, but are not found in the Atlantic Ocean.
The region has an exceptionally high species richness, including 3000 species of fish, compared with around 1200 in the next richest marine region, the Western Atlantic, and around 500 species of reef building corals, compared with about 50 species in the Western Atlantic.List of islands in the Indian Ocean
This is a list of islands in the Indian Ocean.Maldives
The Maldives (, US: (listen); Dhivehi: ދިވެހިރާއްޖެ Dhivehi Raajje), officially the Republic of Maldives, is an Asian country, located in the Indian Ocean, situated in the Arabian Sea. It lies southwest of Sri Lanka and India, about 1,000 kilometres (620 mi) from the Asian continent. The chain of 26 atolls stretches from Ihavandhippolhu Atoll in the north to the Addu City in the south. Comprising a territory spanning roughly 298 square kilometres (115 sq mi), the Maldives is one of the world's most geographically dispersed sovereign states as well as the smallest Asian country by land area and population, with around 427,756 inhabitants. Malé is the capital and a populated city, traditionally called the "King's Island" for its central location.
The Maldives archipelago is located on the Chagos-Laccadive Ridge, a vast submarine mountain range in the Indian Ocean, which also forms a terrestrial ecoregion, together with the Chagos Archipelago and Lakshadweep. With an average ground-level elevation of 1.5 metres (4 ft 11 in) above sea level, it is the world's lowest country, with even its highest natural point being the lowest in the world, at 5.1 metres (17 ft). Due to the consequent risks posed by rising sea levels, the government pledged in 2009 to make the Maldives a carbon-neutral country by 2019.Islam was introduced to the Maldivian archipelago in the 12th century which was consolidated as a sultanate, developing strong commercial and cultural ties with Asia and Africa. From the mid-16th-century, the region came under the increasing influence of European colonial powers, with the Maldives becoming a British protectorate in 1887. Independence from the United Kingdom was achieved in 1965 and a presidential republic was established in 1968 with an elected People's Majlis. The ensuing decades have been characterised by political instability, efforts at democratic reform, and environmental challenges posed by climate change. The Maldives is a founding member of the South Asian Association for Regional Cooperation (SAARC). It is also a member of the United Nations, the Organization of Islamic Cooperation, and the Non Aligned Movement. The World Bank classifies the Maldives as having an upper middle income economy. Fishing has historically been the dominant economic activity, and remains the largest sector by far, followed by the rapidly growing tourism industry. Maldives is rated "high" on the Human Development Index, with its per capita income significantly higher than other SAARC nations.The Maldives was a Commonwealth republic from July 1982 until its withdrawal from the Commonwealth in October 2016 in protest of international criticism of its records in relation to corruption and human rights.North Indian Ocean tropical cyclone
In the Indian Ocean north of the equator, tropical cyclones can form throughout the year on either side of India. On the east side is the Bay of Bengal, and on the west side is the Arabian Sea.Pre-1975 North Indian Ocean cyclone seasons
The years before 1975 featured the pre-1975 North Indian Ocean cyclone seasons. Each season was an ongoing event in the annual cycle of tropical cyclone formation. The North Indian tropical cyclone season has no bounds, but they tend to form between April and December, peaks in May and November. These dates conventionally delimit the period of each year when most tropical cyclones form in the northern Indian Ocean. Below are the most significant cyclones in the time period. Because much of the North Indian coastline is near sea level and prone to flooding, these cyclones can easily kill many with storm surge and flooding. These cyclones are among the deadliest on earth in terms of numbers killed.Scattered Islands in the Indian Ocean
The Scattered Islands in the Indian Ocean (French: Îles Éparses or Îles Éparses de l'océan Indien) consist of four small coral islands, an atoll, and a reef in the Indian Ocean, and have constituted the 5th district of the French Southern and Antarctic Lands (TAAF) since February 2007. They have never had a permanent population. Two of the islands—Juan de Nova and Europa—and the Bassas da India atoll lie in the Mozambique Channel west of Madagascar, while a third island, Tromelin, lies about 450 kilometres (280 mi) east of Madagascar and the Glorioso Islands lies about 200 kilometres (120 mi) northwest of Madagascar. Also in the Mozambique Channel is the Banc du Geyser, a reef under French control claimed by Madagascar since 1976. France and the Comoros view the Banc du Geyser as part of the Glorioso Islands.
The islands have been classified as nature reserves. Except for Bassas da India, they all support meteorological stations: those on the Glorioso Islands, Juan de Nova, and Europa Island are automated. The station on Tromelin Island, in particular, provides warning of cyclones threatening Madagascar, Réunion, or Mauritius. Each of the islands, except Bassas da India and Banc du Geyser, has an airstrip of more than 1,000 metres (3,300 ft).
Mauritius, the Comoros, and Madagascar dispute France's sovereignty over the islands. Mauritius claims Tromelin and argues that the island, discovered by France in 1722, was not ceded by the treaty of Paris in 1814. Madagascar claims sovereignty over the Glorioso Islands (Banc du Geyser included) despite the islands not having been a part of Malagasy Protectorate, but rather a part of colony of Mayotte and dependencies, then a part of French Comoros that had become a separately administered colony from Madagascar in 1946. The Comoros claims the Glorioso Islands (Banc du Geyser included) too, as a part of the disputed French region of Mayotte. Madagascar claims Juan de Nova, and Europa and Bassas da India since 1972. Seychelles claimed a part of Scattered Islands too before the France–Seychelles Maritime Boundary Agreement.Southern Africa-Indian Ocean Division of Seventh-day Adventists
The Southern Africa-Indian Ocean Division of Seventh-day Adventists is a sub-entity of the General Conference of Seventh-day Adventists, which coordinates the Church's activities in the southern portion of Africa, which include the nations of Angola, Ascension Island, Botswana, Comoro Islands, Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Namibia, Réunion, São Tomé and Príncipe, Seychelles, South Africa, Swaziland, Zambia, Zimbabwe; as well as St. Helena and Tristan da Cunha, territories of the United Kingdom, and the Kerguelen Islands, territory of France. Its headquarters is in Johannesburg, South Africa. The Division membership as of June 30, 2017 is 3,779,368.Tropical cyclone naming
Tropical cyclones and subtropical cyclones are named by various warning centers to provide ease of communication between forecasters and the general public regarding forecasts, watches, and warnings. The names are intended to reduce confusion in the event of concurrent storms in the same basin. Generally once storms produce sustained wind speeds of more than 33 knots (61 km/h; 38 mph), names are assigned in order from predetermined lists depending on which basin they originate. However, standards vary from basin to basin: some tropical depressions are named in the Western Pacific, while tropical cyclones must have a significant amount of gale-force winds occurring around the centre before they are named in the Southern Hemisphere.
Before the formal start of naming, tropical cyclones were named after places, objects, or saints' feast days on which they occurred. The credit for the first usage of personal names for weather systems is generally given to the Queensland Government Meteorologist Clement Wragge, who named systems between 1887 and 1907. This system of naming weather systems subsequently fell into disuse for several years after Wragge retired, until it was revived in the latter part of World War II for the Western Pacific. Formal naming schemes and naming lists have subsequently been introduced and developed for the Eastern, Central, Western and Southern Pacific basins, as well as the Australian region, Atlantic Ocean and Indian Ocean.Tropical cyclone scales
Tropical cyclones are unofficially ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basin(s) they are located in. Only a few scales of classifications are used officially by the meteorological agencies monitoring the tropical cyclones, but some alternative scales also exist, such as accumulated cyclone energy, the Power Dissipation Index, the Integrated Kinetic Energy Index, and the Hurricane Severity Index.
Tropical cyclones that develop in the Northern Hemisphere are unofficially classified by the warning centres on one of three intensity scales. Tropical cyclones or subtropical cyclones that exist within the North Atlantic Ocean or the North-eastern Pacific Ocean are classified as either tropical depressions or tropical storms. Should a system intensify further and become a hurricane, then it will be classified on the Saffir–Simpson hurricane wind scale, which is based on the estimated maximum sustained winds over a 1-minute period. In the Western Pacific, the ESCAP/WMO Typhoon Committee uses four separate classifications for tropical cyclones that exist within the basin, which are based on the estimated maximum sustained winds over a 10-minute period.
The India Meteorological Department's scale uses 7 different classifications for systems within the North Indian Ocean, and are based on the systems estimated 3-minute maximum sustained winds. Tropical cyclones that develop in the Southern Hemisphere are only officially classified by the warning centres on one of two scales, which are both based on 10-minute sustained wind speeds: The Australian tropical cyclone intensity scale is used to classify systems within the Australian or South Pacific tropical cyclone basin. The scale used to classify systems in the South-West Indian Ocean is defined by Meteo France for use in various French territories, including New Caledonia and French Polynesia.
The definition of sustained winds recommended by the World Meteorological Organization (WMO) and used by most weather agencies is that of a 10-minute average at a height of 10 m (33 ft). However, the Saffir–Simpson Hurricane Scale is based on wind speed measurements averaged over a 1-minute period, at 10 m (33 ft) above the surface. The scale used by RSMC New Delhi applies a 3-minute averaging period, and the Australian scale is based on both 3-second wind gusts and maximum sustained winds averaged over a 10-minute interval. These make direct comparisons between basins difficult.
Within all basins tropical cyclones are named when the sustained winds hit 35 kn (40 mph; 65 km/h).
Countries and territories bordering the Indian Ocean
Hydrography of the Indian subcontinent
|Inland lakes, deltas, etc.|