Réunion
Geology and relief

La Réunion is a volcanic island born some three million years ago with the emergence of the Piton des Neiges volcano. It has an altitude of 3,070.5 m (10,074 ft), the highest peak in the Mascarene Islands and the Indian Ocean. The eastern part of the island is constituted by the Piton de la Fournaise, a much more recent volcano (500,000 years old) which is considered one of the most active on the planet. The emerged part of the island represents only a small percentage (about 3%) of the underwater mountain that forms it.

In addition to volcanism, the relief of the island is very uneven due to active erosion. The center shelters three vast cirques dug by erosion (Salazie, Mafate and Cilaos) and the slopes of the island are furrowed by numerous rivers digging gullies, estimated at least 600, generally deep and whose torrents cut the sides of the mountains up to several hundreds of meters deep.

The ancient massif of the Piton des Neiges is separated from the massif of La Fournaise by a gap formed by the plaine des Palmistes and the plaine des Cafres, a passageway between the east and the south of the island. Apart from the plains, the coastal areas are generally the flattest regions, especially in the north and west of the island. The coastline of the wild south is however steeper.

Between the coastal fringe and the Hauts, there is a steep transitional zone whose gradient varies considerably before arriving at the ridge lines setting the cirques or the Enclos, the caldera of the Piton de la Fournaise.
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