Saya de Malha Bank

The Saya de Malha Bank (also Sahia de Malha Bank, Modern Portuguese: saia de malha, English mesh skirt) is a large submerged bank in the Indian Ocean, part of the vast undersea Mascarene Plateau. It lies east of Madagascar, southeast of the Seychelles, and north of the Nazareth Bank, the Cargados Carajos shoals, and the island of Mauritius, and falls into Mauritian Territorial waters. The closest piece of land are the tiny Agalega Islands (a remote dependency of Mauritius), some 300 km further west, followed by the southern Seychellois island of Coëtivy, some 400 km northwest. Mauritius administers Saya de Malha Bank and it is part of its Exclusive Economic Zone.

Map of Saya de MalhaThe bank was named by Portuguese explorers 500 years ago, who encountered the bank on the voyage between the Cape of Good Hope and India. After traversing miles of the deep blue Indian Ocean, they found themselves sailing above the shallow bank, which was covered with swaying green seagrass.

The first serious survey of the bank was undertaken by Captain Robert Moresby of the Royal Navy in 1838, who had previously surveyed the Laccadives, the Red Sea, the Maldives and the Chagos. Owing to health reasons, the Saya de Malhas bank was Moresby's last survey in a long and brilliant career exploring and charting the archipelagoes and reefs of the Indian Ocean.

The bank covers an area of 40,808 km²[1]. It is in fact composed of two separate structures, the smaller North Bank (also called Ritchie Bank) and the huge South Bank. If the South Bank were to be recognized as a submerged atoll structure, it would be the largest of the world, being almost three times as big as the Great Chagos Bank that is commonly considered the largest atoll structure of the world. Even the smaller North Bank by itself would be one of the largest atolls worldwide. The North Bank and the South Bank very likely have different origins, since they appear to be separated by a fault. Studies also conclude that the South Bank and the Great Chagos Bank were one single feature until about 64 to 69 million years ago the opening of an ocean ridge between them started pushing them apart.

Saya de Malha Bank consists of a series of narrow shoals, with depths from 17 to 29 meters on the rim. They are arranged in a semicircular manner, around a space, the former lagoon, about 73 meters deep, which slopes on the Southeast. Parts of the bank are quite shallow, coming closer than 10 meters below the surface. The shallowest sites known are Poydenot Rock, with a depth of 8 meters, and an unnamed site 145 km further northwest, with a depth of 7 meters. The banks are covered with sea grass interspersed with small coral reefs. Because of its remote location, the bank is among the least-studied shallow marine ecoregions on the planet. The banks are a breeding ground for Humpback Whales and Blue Whales.


The bank was formed 35 million years ago by the Réunion hotspot, and is made up of basaltic basal rock overlain with limestone. The limestone banks found on the plateau are the remnants of coral reefs. Millions of years ago, the bank was one or more mountainous volcanic islands, like present-day Mauritius and Réunion, which subsequently sank below the waves. Some of the banks may have been low islands as recently as 18,000 - 6,000 years ago, when sea levels were up to 130 meters lower during the most recent ice age.

Artificial Island Project

The North Bank is the site of an artificial island project. The name of the island that is to grow around steel structure that had been anchored to the sea floor in 2003 at a depth of 11 meters is Autopia, and it is the projected center of a new micronation of the same name. Mauritius will claim and annex any new piece of land that might emerge in the area automatically, just as occurred in the similar case of the Republic of Minerva on the Minerva Reefs, which is now part of Tonga. Mauritius does already claim the entire area.

Further Reading

Saya de Malha Bank (Lighthouse Foundation)

Proposed artificial island and micronation Autopia (in German)

Saya de Malha exploration and coral ark construction expedition 2002