Banc du Geyser
Other names: Banc du Geysir, Arecife de Santo Antonio
|Satellite image of Banc du Geyser (center) with Mayotte (left), Glorioso Islands (top right) and Madagascar (bottom right)|
|Length||8 km (5 mi) (low tide only)|
|Width||5 km (3 mi) (low tide only)|
|Highest point||South Rock
Banc du Geyser (also Banc du Geysir) is a mostly submerged reef in the Mozambique Channel's northeastern part, 125 km (78 mi) northeast from Mayotte, 112 km (70 mi) southwest of the Glorioso Islands, and 200 km (124 mi) off the northwestern coast of Madagascar.
The Banc is a dangerous oval-shaped reef 8 km (5 mi) long and 5 km (3 mi) wide that becomes exposed only at low tides, with the exception of some rock formations in the southern part of the reef. The rocks are generally 1.5 to 3 m (4 ft 11.1 in to 9 ft 10.1 in) in height; the largest is South Rock, with a height of 8 m (26 ft), similar to a boat under sail. In the eastern part of the reef there are some sandy cays, 1 to 3 m (3 ft 3 in to 9 ft 10 in) 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 sea birds, and the cays are covered in tons of guano.
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 the British vessel Geysir ran on the reef.
The reef is claimed by France, Madagascar and the Comoros alike. From the French point of view, it is part of their Scattered Islands in the Indian Ocean; Madagascar announced its annexation in 1976, presumably because of the possibility of oil fields in the vicinity. The Comoros claim the Banc du Geyser as part of its exclusive economic zone.
About 20 km (12 mi) southwest of Geysir is Zélée Bank, a deep submarine feature.
- Satellite images of Banc du Geysir at the Wayback Machine (archived December 23, 2010)
- Sailing Directions: East Africa and the South Indian Ocean