Mascarene Islands
The Mascarene Islands — Réunion, Mauritius,
and Rodrigues — are located in the southwestern Indian Ocean, lying east of Madagascar
and south of the Seychelles. Réunion forms an overseas department of France, while Mauritius and its dependent
territory of Rodrigues form the independent nation of the Republic of Mauritius. Also included in this section are the
dependent territories of Mauritius — the Cargados Carajos Shoals and the
Agalega Islands — and the small island of Tromelin —
a territory of Réunion. The islands have a combined land area of 4,514 km².
The main islands of the group are all located at the southern end of the Mascarene Plateau and lie in a northeast to southwest line stretching for some 875 km; Rodrigues lies at the eastern end of the chain, Réunion at the western end. Réunion, at 2,500 km² in area, is the largest of the mascarene islands. It is still volcanically active — the Piton de la Fournaise being one of the most active volcanoes of the Indian Ocean region. The mountainous and rugged interior of Réunion also contains the Mascarene Islands highest elevation above sea level, where the Piton des Neiges reaches a height of 3,069 m.
The older and slightly smaller island of Mauritius (1,865 km²) is located 170 km to the northeast of Réunion. Mauritius is no longer volcanically active; instead, its eroded interior has a more rounded appearance with its highest point reaching 828 m above sea level. Being older than Réunion, fringing and barrier reefs have had time to develop around it shores.
Smaller (119 km²) and older still is the island of Rodrigues, situated a farther 570 km to the east. It sits within an extensive lagoon and barrier reef system with its eroded central spine reaching a height of 395 m above sea level.
The Mascarene Plateau itself is a huge submarine composite arc system that extends across some 2,300 km of the western Indian Ocean, running from the Seychelles in the north through the Saya de Malha, Nazareth, and Cargados Carajos banks to the mountainous islands of Mauritius and Réunion in the south. In all, the plateau covers a region encompassing some 120,000 km² with much of this consisting of shallow waters with a depth of between 10 and 150 m. These bank formations were originally created as a result of the same hotspot that gave rise to the Deccan Plateau of India, as well as to the Chagos, Lakshadweep and Maldive islands between 65 and 20 million years ago.
The formation of the islands at the southern end of the plateau is of more recent origin — a result of the same hotspot that is currently located beneath Réunion. The islands of the Seychelles, located at the northern extremities of the Mascarene Plateau, have a different geological origin to those of the Mascarene group, being the eroded continental fragments arising from the break-up of the former Gondwanaland super-continent some 130 million years ago.
