Its sedimentary layers slope toward the Mozambique Channel and produce a succession of hills. The western zone is between 60 and 125 miles (100 and 200 km) wide. To the extreme north the plateau is bordered by the low belt of the Ambohitra Mountains, which include a series of volcanic craters. However, in places the central plateau is bordered by an impassable escarpment, such as the Cliff of Bongolava in the west-central part of the island. Toward the west the descent is made in a series of steps. To the south the two steep gradients meet and form the Mahafaly and the Androy plateaus, which overhang the sea in precipitous cliffs. Behind the scarp face are the remains of ancient lakes, including one called Alaotra. This cliff, which is called the Great Cliff or the Cliff of Angavo, is often impassable and is itself bordered by the Betsimisaraka Escarpment, a second and lower cliff to the east, which overhangs the coastal plain. To the east it descends in a sharp fault, by vertical steps of 1,000 to 2,000 feet (300 to 600 metres). The plateau slopes with some regularity toward the extreme southern plain, but its boundaries to the east and west are more abrupt. Farther south, Andringitra is a vast granite massif north of Tôlan̈aro (Faradofay) it rises to 8,720 feet (2,658 metres) at Boby Peak. Ankaratra is a major watershed divide separating three main river basins. Ankaratra Massif in the centre is an enormous volcanic mass whose summit, Tsiafajavona, is 8,671 feet (2,643 metres) high. The Tsaratanana region in the north is separated from the rest of the plateau by the Tsaratanana Massif, whose summit, Maromokotro, reaches 9,436 feet (2,876 metres) and is the highest point on the island. Three massifs are more than 8,500 feet (2,600 metres) high. Situated between 2,500 and 4,500 feet (800 and 1,400 metres) above sea level, the plateau has been uplifted and worn down several times and is tilted to the west. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.
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