Banc du Geyser (also Banc du Geysir) is a mostly submerged

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

in the

Mozambique Channel The Mozambique Channel (, , ) is an arm of the Indian Ocean located between the Southeast African countries of Madagascar and Mozambique. The channel is about long and across at its narrowest point, and reaches a depth of about off the coa ...

's northeastern part, northeast from

Mayotte Mayotte ( ; , ; , ; , ), officially the Department of Mayotte (), is an Overseas France, overseas Overseas departments and regions of France, department and region and single territorial collectivity of France. It is one of the Overseas departm ...

, southwest of the

Glorioso Islands The Glorieuses or Glorioso Islands ( or officially also ) are a group of islands and rocks totaling . They are controlled by France as part of the Scattered Islands in the Indian Ocean in the French Southern and Antarctic Lands, a French overse ...

and off the northwestern coast of

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

Description

The Banc is a dangerous oval-shaped reef long and wide that becomes exposed only at low

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

s, with the exception of some rock formations in the southern part of the reef. The rocks are generally in height; the largest is South Rock, with a height of , similar to a boat under sail. In the eastern part of the reef there are some sandy

cay A cay ( ), also spelled caye or key, is a small, low-elevation, sandy island on the surface of a coral reef. Cays occur in tropical environments throughout the Pacific, Atlantic, and Indian oceans, including in the Caribbean and on the Grea ...

s, in height covered with grass and small bushes. The entrance into the central lagoon is possible from a south-southeastern direction. There is an abundance of

seabird Seabirds (also known as marine birds) are birds that are adaptation, adapted to life within the marine ecosystem, marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent ...

s, and the cays are covered in tons of

guano Guano (Spanish from ) is the accumulated excrement of seabirds or bats. Guano is a highly effective fertiliser due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant growth. Guano was also, to a le ...

. About southwest of Geysir is Zélée Bank, a deep submarine feature.

History

The Geysir Reef was first known by Arab sailors around the year 700, and was shown on some navigation-charts dated around 800. Around 1650 the reef was shown on Spanish maps as ''Arecife de Santo Antonio''. The current name was given on 23 December 1678, when a British vessel, Geysir, ran on the reef. France and the

Comoros The Comoros, officially the Union of the Comoros, is an archipelagic country made up of three islands in Southeastern Africa, located at the northern end of the Mozambique Channel in the Indian Ocean. Its capital and largest city is Moroni, ...

claim the Banc du Geyser as part of their

exclusive economic zone An exclusive economic zone (EEZ), as prescribed by the 1982 United Nations Convention on the Law of the Sea, is an area of the sea in which a sovereign state has exclusive rights regarding the exploration and use of marine natural resource, reso ...

(EEZ). The reef is also claimed by

. From the French point of view, it is a part of the EEZ of

, one of their

Scattered Islands in the Indian Ocean The Scattered Islands in the Indian Ocean ( or ') consist of four small coral islands, an atoll, as well as a reef in the Indian Ocean; they constitute the fifth district of the French Southern and Antarctic Lands, though sovereignty over some ...

. Madagascar announced its annexation in 1976, presumably because of the possibility of

oil fields A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presen ...

in the vicinity but the Banc du Geyser is controlled in fact by the French ''forces armées de la zone sud de l'océan Indien''. In 2012, France included the reef in the ''parc naturel marin des Glorieuses'', a

marine protected area A marine protected area (MPA) is a protected area of the world's seas, oceans, estuaries or in the US, the Great Lakes. These marine areas can come in many forms ranging from wildlife refuges to research facilities. MPAs restrict human activity ...

, to preserve the endangered flora and fauna of the

. The Scattered Islands in the Indian Ocean are partially claimed by the Comoros, Madagascar, and Mauritius. The Malagasy and Mauritian claims, however, are significantly later than their access to independence. However, the agreement reached in October 2024 on the restitution to Mauritius of the Chagos Islands by Great Britain, in the heart of the Indian Ocean, notably home to the American base of Diego Garcia, has relaunched the debate in Madagascar.

References

External links

*
Sailing Directions: East Africa and the South Indian Ocean
Accessed 30 September 2022. {{Scattered islands in the Indian Ocean Disputed waters Reefs of France Territorial disputes of France Territorial disputes of Madagascar Territorial disputes of the Comoros Reefs of the Indian Ocean Landforms of Madagascar Landforms of the Comoros Comoros–Madagascar relations France–Madagascar relations Comoros–France relations Islands of Madagascar