Extending from c. 10°S to 15°N, the CLR includes the Laccadive, Maldives, and Chagos archipelagos and can be divided into three corresponding blocks, of which the first is continental and the two latter are oceanic. The CLR is asymmetrical with a steeper eastern slope and has an average depth of less than 1,000 m (3,300 ft). It formed south of or near the Equator together with the remaining western continental margin of India, when India separated first from Madagascar in the Mid-Cretaceous and then from the Seychelles in the Late Cretaceous.
The CLR extends northward for c. 2,550 km (1,580 mi) from 10°S at the southern end of the Chagos Archipelago to 14°N around the Adas Bank. The second element of the name is for the Laccadive Islands, among the islands of Lakshadweep. ("Laccadive" is a form of the name "Lakshadweep".) The islands of Chagos, the Maldives and Lakshadweep are the above-water parts of the Chagos-Laccadive Ridge.
The Laccadive Ridge, the northern part of the CLR, parallels the Indian west coast (8°N–16°N) and has an average width of 270 km (170 mi). It is separated from the flanking basins by fault scarps made of thick, high-density crust. It is made of thinned continental crust marked by the volcanism that occurred near the KT-boundary c. 66 Ma. This caused by the passage over the Rėunion hotspot and the resulting India–Madagascar breakup.
The western coastal margin of the Indian subcontinent was affected by two large igneous provinces at 85 Ma and 65 Ma associated with the Marion and Réunion hotspots, respectively. This has left a complex of ridges that run parallel to the west coast of which the Laccadive Ridge is the larger. A complex of considerably smaller ridges constitutes a northern extension to the CLR. The Laxmi Ridge, the larger of these, is made of continental crust and formed during the Seychelles-India breakup. East of the Laxmi Ridge in the Laxmi Basin, the Panikkar Ridge is made of stretched continental crust and has a similar tectonic history. In contrast, the Palitana Ridge north of the Panikkar Ridge probably represents an extinct spreading centre and on the nearby shelf and slope a lineament, known as the Prathap Ridge Complex, is similarly made of oceanic crust and both are probably leftovers from the India–Madagascar breakup.
The vast Chagos-Laccadive Ridge was formed by the Réunion volcanic hotspot along with the southern part of the Mascarene Plateau. Both plateaux are volcanic traces of the Réunion hotspot. Although the Chagos-Laccadive Ridge is an aseismic ridge, between 1965 and 1970 an unusual, isolated swarm of earthquakes occurred on the west side of the Great Chagos Bank at approximately .
Adas Bank is a submerged bank located off the west coast of India, between Angria Bank (200 km to the north) and Cora Divh bank of the Laccadive Islands (90 km to the south).Arabian Basin
The Arabian Basin is an oceanic basin located in the
southern part of the Arabian Sea between the Arabian Peninsula and India. It is centered at 10° N, 65° E. The basin depth ranges from 3,400 m in the north to 4,400 m in the south, with a maximum depth of 4,652 m. The floor is covered by sediments from the Indus submarine fan and is relatively smooth.The southern enclosure of this basin is formed by the Central Indian Ridge, the Carlsberg Ridge and the Chagos-Laccadive Ridge. Bottom water enters the basin through the Owen Fracture Zone to the west. The Carlsberg Ridge, at a depth of 3,800 m, separates this basin from the Somali Basin to the southwest. The Arabian Basin is separated from the shallow Oman Basin by the Murray Ridge. Most of the northern and eastern limits are formed by the Laxmi Ridge and the Laccadive Plateau.Bhargavaea
Bhargavaea is a bacteria genus from the family of Planococcaceae.Bhargavaea cecembensis
Bhargavaea beijingensis is a Gram-positive, non-spore-forming, rod-shaped and non-motile bacterium from the genus of Bhargavaea which has been isolated from deep-sea sediments from the Chagos-Laccadive Ridge from the Indian Ocean.Central Indian Ridge
The Central Indian Ridge (CIR) is a north-south-trending mid-ocean ridge in the western Indian Ocean.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.The Chagos was 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. Since being expelled, Chagossian natives have been prevented from returning to the islands.
The sovereignty of the Chagos Archipelago is disputed between the United Kingdom and Mauritius. In 1965, three years before Mauritius gained independence, the United Kingdom excised the archipelago from Mauritius and the islands of Aldabra, Farquhar and Desroches from the Seychelles to form the British Indian Ocean Territory (BIOT). The islands were formally established as an overseas territory of the United Kingdom on 8 November 1965. On 23 June 1976, Aldabra, Farquhar and Desroches were returned to the Seychelles. On 22 June 2017, the UN General Assembly asked the International Court of Justice to give an advisory opinion on the separation of the Chagos Archipelago from Mauritius. On 25 February 2019, the International Court of Justice ruled that the United Kingdom is under an obligation to bring to an end to its administration of the Chagos Archipelago as rapidly as possible. On 22 May 2019, the United Nations General Assembly debated and adopted a resolution that affirmed that the Chagos archipelago “forms an integral part of the territory of Mauritius.” The resolution demanded that the UK “withdraw its colonial administration … unconditionally within a period of no more than six months.” 116 states voted in favour of the resolution, 55 abstained and only 5 countries supported the UK. During the debate, the Mauritian Prime Minister described the expulsion of Chagossians as "akin to a crime against humanity." The resolution's immediate consequence is that the UN and other international organisations are now bound by UN law to support the decolonisation of the Chagos Islands. The United Kingdom claims that it has no doubt about its sovereignty over the archipelago.Diego Garcia
Diego Garcia is an island of the British Indian Ocean Territory, an overseas territory of the United Kingdom. It is a militarised 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 by Europeans 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 the Chagos Islands were detached for inclusion in the newly created British Indian Ocean Territory (BIOT) in 1965.
In 1966, the population of the island was 924. These people were employed as contract farm workers on coconut plantations owned by the Chagos-Agalega company. Although it was common for local plantation managers to allow pensioners and the disabled to remain in the islands and continue to receive housing and rations in exchange for light work, children after the age of 12 were required to work. In 1964, only 3 of a population of 963 were unemployed. In April 1967, the BIOT Administration bought out Chagos-Agalega for £600,000, thus becoming the sole property owner in the BIOT. The Crown immediately leased back the properties to Chagos-Agalega but the company terminated the lease at the end of 1967.Between 1968 and 1973, the now unemployed farm workers were forcibly removed from Diego Garcia by the UK Government so a joint US/UK military base could be established on 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 with peaks consisting 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.In May 2019, the United Nations General Assembly affirmed the decision of the International Court of Justice and demanded that the United Kingdom withdraw its colonial administration from the Islands and cooperate with Mauritius to facilitate the resettlement of Mauritian nationals in the archipelago.In a written statement the U.S. government said that neither the Americans or the British have any plans to discontinue use of the military base on Diego Garcia. The statement said in a footnote:
"In 2016, there were discussions between the United Kingdom and the United States concerning the continuing importance of the joint base. Neither party gave notice to terminate and the agreement remains in force until 2036".Geography of the British Indian Ocean Territory
The British Indian Ocean Territory (BIOT) is an archipelago of 55 islands in the Indian Ocean, located south of India. It is situated approximately halfway between Africa and Indonesia. The islands form a semicircular group with an open sea towards the east. The largest, Diego Garcia, is located at the southern extreme end. It measures 60 square kilometres (23 sq mi) and accounts for almost three-quarters of the total land area of the territory. Diego Garcia is the only inhabited island and is home to the joint UK-US naval support facility. Other islands within the archipelago include Danger Island, Three Brothers Islands, Nelson Island, and Peros Banhos, as well as the island groups of the Egmont Islands, Eagle Islands, and the Salomon Islands.Geology of Réunion
Réunion is a mafic island formed as a result of the Réunion hotspot in the Indian Ocean, the same hotspot that produced the massive basalt flows of the Deccan Traps, when it was beneath India more than 66 million years ago.Hassan Nasiem Siddiquie
Hassan Nasiem Siddique (1934–1986) was an Indian marine geologist and the director of the National Institute of Oceanography. He was the deputy leader of the first Indian expedition to the Antarctica during 1981–82. He was known for his geological studies on Bay of Bengal and the Arabian Sea and was an elected fellow of the Indian National Science Academy, Geological Society of India, Association of Exploration Geophysicists and the National Academy of Sciences, India. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards for his contributions to Earth, Atmosphere, Ocean and Planetary Sciences in 1978. The Government of India awarded him the fourth highest Indian civilian honour of Padma Shri in 1983.Indian Ocean
The Indian Ocean is the third-largest of the world's oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) (19.8% 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.Lakshadweep
Lakshadweep (; ISO: Lakṣadvīp ), formerly known as the Laccadive, Minicoy, and Aminidivi Islands (), is a group of islands in the Laccadive Sea, 200 to 440 km (120 to 270 mi) off the southwestern coast of India. The archipelago is administered as a union territory and district of India. They were also known as Laccadive Islands, although geographically this is only the name of the central subgroup of the group. Lakshadweep means "one hundred thousand islands" in Sanskrit and Malayalam. The islands form the smallest Union Territory of India and their total surface area is just 32 km2 (12 sq mi). The lagoon area covers about 4,200 km2 (1,600 sq mi), the territorial waters area 20,000 km2 (7,700 sq mi) and the exclusive economic zone area 400,000 km2 (150,000 sq mi). The region forms a single Indian district with 10 subdivisions. Kavaratti serves as the capital of the Union Territory and the region comes under the jurisdiction of Kerala High Court. The islands are the northernmost of the Lakshadweep-Maldives-Chagos group of islands, which are the tops of a vast undersea mountain range, the Chagos-Laccadive Ridge.As the islands have no aboriginal inhabitants, scholars have suggested different histories for the settlement of these islands. Archaeological evidence supports the existence of human settlement in the region around 1500 BC. The islands have long been known to sailors, as indicated by an anonymous reference from the first century AD to the region in Periplus of the Erythraean Sea. The islands were also mentioned in the Buddhist Jataka stories of the sixth century BC. Islam was established in the region when Muslims arrived around the seventh century. During the medieval period, the region was ruled by the Chola dynasty and Kingdom of Cannanore. The Catholic Portuguese arrived around 1498 but were expelled by 1545. The region was then ruled by the Muslim house of Arakkal, followed by Tipu Sultan. On his death in 1799, most of the region passed on to the British and with their departure, the Union Territory was formed in 1956.
Ten of the islands are inhabited. At the 2011 Indian census, the population of the Union Territory was 64,473. The majority of the indigenous population is Muslim and most of them belong to the Shafi school of the Sunni sect. The islanders are ethnically similar to the Malayali people of the nearest Indian state of Kerala. Most of the population speaks Malayalam with Mahi (or Mahl) being the most spoken language in Minicoy island. The islands are served by an airport on Agatti Island. The main occupation of the people is fishing and coconut cultivation, with tuna being the main item of export.Maldives
The Maldives (, US: (listen); Dhivehi: ދިވެހިރާއްޖެ Dhivehi Raajje), officially the Republic of Maldives, is a small country in South Asia, located in the Arabian Sea of the Indian Ocean. 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 Addu Atoll 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 the most 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 one of 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 granted 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 member of the Commonwealth from July 1982 until its withdrawal from the organisation in October 2016 in protest of international criticism of its records with regard to corruption and human rights.Mantle plume
A mantle plume is a proposed mechanism of convection of abnormally hot rock within the Earth's mantle. Because the plume head partly melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries or in large igneous provinces.
The hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the "Plate model". This proposes shallower, passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it, attributing most volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.Mascarene Plateau
The Mascarene Plateau is a submarine plateau in the Indian Ocean, north and east of Madagascar. The plateau extends approximately 2,000 km (1,200 mi), from the Seychelles in the north to Réunion in the south. The plateau covers an area of over 115,000 km2 (44,000 sq mi) of shallow water, with depths ranging from 8–150 m (30–490 ft), plunging to 4,000 m (13,000 ft) to the abyssal plain at its edges. It is the second largest undersea plateau in the Indian Ocean after the Kerguelen Plateau.Ninety East Ridge
The Ninety East Ridge (also rendered as Ninetyeast Ridge, 90E Ridge or 90°E Ridge) is a linear structure on the Indian Ocean floor named for its near-parallel strike along the 90th meridian at the center of the Eastern Hemisphere. It is approximately 5,000 kilometres (3,100 mi) in length and can be traced topographically from the Bay of Bengal southward towards the Southeast Indian Ridge (SEIR), though the feature continues to the north where it is hidden beneath the sediments of the Bengal Fan. The ridge extends between latitudes 33°S and 17°N and has an average width of 200 km.The ridge divides the Indian Ocean into the West and East Indian Ocean. The northeastern side is named the Wharton Basin and ceases at the western end of the Diamantina Fracture Zone which passes to the east and almost to the Australian continent.The ridge is primarily composed of Ocean Island Tholeiites (OIT), a subset of basalt which increase in age from approximately 43.2 ± 0.5 Ma in the south to 81.8 ± 2.6 Ma in the north though a more recent analysis using modern Ar–Ar techniques is currently pending publication. This age progression has led geologists to theorize that a hotspot in the mantle beneath the Indo-Australian Plate created the ridge as the plate has moved northward in the late Mesozoic and Cenozoic. This theory is supported by a detailed analysis of the chemistry of the Kerguelen Plateau and Rajmahal Traps, which together, geologists believe, represent the flood basalts erupted at the initiation of volcanism at the Kerguelen hotspot which was then sheared in two as the Indian subcontinent moved northward. However, the existence of so-called deep mantle hotspots is currently a topic of debate in the geologic community, with a few geochemists favoring an alternative hypothesis which postulates a much shallower origin for hotspot volcanism.The ridge has been surveyed several times in the past, including several times by the Deep Sea Drilling Program (DSDP). In 2007, the RV Roger Revelle collected bathymetric, magnetic and seismic data together with dredge samples from nine sites along the ridge as part of an Integrated Ocean Drilling Program (IODP) site survey intended to examine the hotspot hypothesis for the ridge.It had been assumed that the India and Australia are on a single tectonic plate for at least the last 32 million years. However, considering the high level of large earthquakes in the Ninety East Ridge area and the evidence of deformation in the central Indian Ocean, it is more appropriate to consider the deformed region in the central Indian Ocean as a broad plate boundary zone separating the Indian Plate and the Australian Plate.Outline of oceanography
The following outline is provided as an overview of and introduction to Oceanography.Réunion hotspot
The Réunion hotspot is a volcanic hotspot which currently lies under the island of Réunion in the Indian Ocean. The Chagos-Laccadive Ridge and the southern part of the Mascarene Plateau are volcanic traces of the Réunion hotspot.The hotspot is believed to have been active for over 65 million years. A huge eruption of this hotspot 65 million years ago is thought to have laid down the Deccan Traps, a vast bed of basalt lava that covers part of central India, and opened a rift which separated India from the Seychelles Plateau. The Deccan Traps eruption coincided roughly with the nearly antipodal Chicxulub impactor and the Cretaceous–Paleogene extinction of the dinosaurs, and there is considerable speculation that the three events were related. As the Indian plate drifted north, the hotspot continued to punch through the plate, creating a string of volcanic islands and undersea plateaux. The Laccadive Islands, the Maldives, and the Chagos Archipelago are atolls resting on former volcanoes created 60–45 million years ago that subsequently submerged below sea level. About 45 million years ago the mid-ocean rift crossed over the hotspot, and the hotspot passed under the African Plate.
The hotspot appears to have been relatively quiet 45–10 million years ago, when activity resumed, creating the Mascarene Islands, which include Mauritius, Réunion, and Rodrigues. Mauritius and Rodrigues Ridge were created 8–10 million years ago, and Rodrigues and Réunion Islands in the last two million years. Piton de la Fournaise, a shield volcano on the southeastern corner of Réunion, is one of the most active volcanoes in the world, erupting last in February 2019.Search for Malaysia Airlines Flight 370
The disappearance on 8 March 2014 of Malaysia Airlines Flight 370, a scheduled international passenger flight from Kuala Lumpur International Airport to Beijing Capital International Airport, prompted a large, multinational search in Asia and the southern Indian Ocean that became the most expensive search in aviation history. Analysis of communications between the aircraft and Inmarsat by multiple agencies has concluded that the flight ended in the southern Indian Ocean.
An analysis of possible flight paths was conducted, identifying a 60,000 km2 (23,000 sq mi) primary search-area, approximately 2,000 km (1,200 mi) west of Perth, Western Australia, which takes six days for vessels to reach from Fremantle Harbour, near Perth. The underwater search of this area began on 5 October 2014 at a cost of A$60 million (approximately US$56 million or €41 million). With no significant delays, the search of the priority search-area was to be completed around May 2015. On 29 July 2015, a piece of marine debris, later confirmed to be a flaperon from Flight 370, was found on Réunion Island. On 20 December 2016, it was announced that an unsearched area of around 25,000 square kilometres (9,700 sq mi), and approximately centred on location 34°S 93°E, was the most likely impact location for flight MH370. The search was suspended on 17 January 2017. In October 2017, the final drift study believed the most likely impact location to be at around 35.6°S 92.8°E / -35.6; 92.8 (CSIRO crash area). The search based on these coordinates was resumed in January 2018 by Ocean Infinity, a private company; it ended in June 2018 without success.
Ships and aircraft from Australia, China, India, Japan, Malaysia, New Zealand, South Korea, the United Kingdom, and the United States were involved in the search of the southern Indian Ocean. Satellite imagery was also made available by Tomnod to the general public so they could help with the search through crowdsourcing efforts.