Madagascar is the fourth largest island in the world, located off the southeastern coast of Africa in the Indian Ocean, and separated from the African coast by the channel of Mozambique. The island is divided by ridges, valleys, rivers and tropical forests into many sections, each with a somewhat different climate and topography: a central plateau with scattered trees and tall grasses, narrow coastal plains in the east, and low plateaus and plains in the west. A backbone of mountains stretches the length of the island. Rivers are short and fast flowing in the east and longer in the west. Behind the coral beaches of the east coast an almost continuous chain of lagoons is connected by the Pangalanes Canal, which forms and inland waterway.