Madagascar

Geography

Madagascar is an island in the Indian Ocean, off the eastern coast of southern Africa, east of Mozambique, with a total area of 587,041 km2, it is the fourth largest island in the world. The terrain comprises an interior highland plateau (800-1800m) and flanking lowlands. Towards the east, a steep escarpment leads from the central highlands down into a ribbon of rain forest with a narrow coastal plain further east. The coastline is straight, with the exception of Antongil Bay in the north of the island. Descent from the highlands toward the west is more gradual and the lowland fringe much wider and the coastline more indented. The central highlands have scattered volcanic massifs. The Tsaratanana Massif region at the north end of the island contains the highest point on the island at 2,880m. A rift valley runs north-south along the eastern escarpment zone and is host to Lac Alaotra the largest body of water on the island. All major rivers drain westward and empty into the Mozambique Channel. 

Geology

The eastern two thirds of Madagascar are underlain by voluminous Precambrian, Archean and Proterozoic, rocks of diverse character, sporadically intruded by Cretaceous to Neogene age basalts and rhyolites. The Archean sequences are found throughout the length of the Island and comprise gneiss, migmatites, charnockites, granitoid-migmatites, amphibolites, schist and greenstones. Paleoproterozoic rocks comprise paragneiss, granite-gneisss, charnockites, metasediments and schist. The western third is composed of two large basins of Mid-Paleozoic to Recent sedimentary rocks.