The islands in the atolls of the Maldives are usually flat and sandy. All islands in the Maldives have an underlying coralline reef. Islands may disappear when the currents on the reef change but also new islands may appear, beginning as sandbanks or coral gravel heaps at another location of the reef. The environment of most of Maldives islands is the same. There is a few types of trees, low houses with yards and the waterside. There is typical 300 inhabitants per island.