Situated off the southeast coast of Africa, Madagascar is the fourth largest island in the world. It is separated from the coast of Africa by the Mozambique Channel, the shortest distance between the island and the mainland is 400 km.
Madagascar consists mainly of a block of crystalline rocks. It is generally described as a plateau, rising sharply from the narrow plain of the east coast and descending in a series of steps to the strip of sedimentary rocks along the west coast. The high plateau is much indented and, on the eastern edge, cut by deep gorges and waterfalls. There are numerous volcanic outcrops that produce heights over 6,000 ft (the highest point being Tsaratanan, at 9,450 ft) and two former volcanic areas, Ankaratra and Andringingtra, which are over 8,500 ft.

The eastern coast is almost straight and has very few anchorages. Behind its coral beaches there is an almost continuous line of lagoons from Foulpointe to Farafrandana. These are linked by man-made channels to form an inland waterway called the Pangalanes Canal. The island's major rivers flow westward.