Mascarene Plateau

The Mascarene Plateau is an underwater ridge and system of banks in the western Indian Ocean, extending broadly between the Seychelles region and the Mascarene Islands, including Réunion and Mauritius. Encyclopaedia Britannica also uses the name Seychelles-Mauritius Plateau for the submarine ridge, describing it as a shallow, crescent-shaped feature in the Indian Ocean. The geographical scope of the broader Mascarene Plateau can vary among sources; it should not be confused with the Mascarene Islands, the group of inhabited islands to its south.

The plateau is not a uniform block of seafloor: it comprises banks and ridges with distinct origins and depths. The Saya de Malha Bank, a major shallow bank, is capped by carbonate deposits and reef-derived sediments, and its central depressions descend substantially below the shallow rims. The northern Seychelles-related portions include continental material, while other parts of the plateau are associated with volcanic activity. These different geological histories make simple descriptions of the entire plateau as either wholly continental or wholly volcanic misleading.

Submerged banks shape currents and habitats in the region. A survey published in Deep-Sea Research I found that the South Equatorial Current is divided into northern and southern cores as it passes the plateau, with part of its flow crossing a sill between the Saya de Malha and Nazareth banks. Shallow areas support extensive seagrass, while ocean-platform interactions can affect productivity and marine food webs. The remote banks remain difficult to study and manage.

Mauritius and Seychelles jointly manage an area of extended continental shelf in the Mascarene Plateau region under a bilateral framework. The countries' Joint Management Area covers the seabed and subsoil and is intended to coordinate stewardship and management of marine resources. Official accounts describe continuing work on environmental monitoring, marine planning and scientific data gathering. This joint seabed-management arrangement does not mean the two states jointly administer every part of the wider plateau or all waters above it.