Topography

The Andaman and Nicobar Islands, unlike the Lakshadweep-Chagos chain, are high volcanic islands, arising from a submerged mountain chain that follows the southward extension of the continental shelf.

Extensive fringing reefs exist here, as well as a 320 kilometers-long barrier reef on the west coast. Much of the wildlife on these islands is endemic, including 112 species of endemic birds. While poorly known scientifically, these reefs may prove to be the most diverse and best preserved in the Indian Ocean.

The islands forming Great Andaman consist of a mass of hills enclosing very narrow valleys, the whole covered by dense tropical jungle. The hills rise to a considerable elevation: the chief heights being in the North Andaman, Saddle Peak (732 m); in the Middle Andaman, Mount Diavolo behind Cuthbert Bay (511 m); in the South Andaman, Koiob (459 m), Mount Harriet (364 m) and the Cholunga range (324 m); and in Rutland Island, Ford’s Peak (433 m).

Little Andaman is practically flat. There are no rivers and few perennial streams in the islands. The whole of the Andamans and the outlying islands were completely surveyed topographically by the Indian Survey Department under Colonel Hobday in 1883-1886, and the surrounding seas were charted by Commander Carpenter in 1888-1889.

Harbours

The coasts of the Andamans are deeply indented, giving existence to a number of safe harbours, which are often surrounded by mangrove swamps. The chief harbours are (starting northwards from Port Blair, the great harbour of South Andaman) on the East coast: Port Meadows, Colebrooke Passage, Elphinstone Harbour (Homfray’s Strait), Stewart Sound and Port Cornwallis.

The last three are very large. On the West coast: Temple Sound, Interview Passage, Port Anson or Kwangtung Harbour (large), Port Campbell (large), Port Mouat and Macpherson Strait. There are many other safe anchorages about the coast, notably Shoal Bay and Kotara Anchorage in South Andaman; Cadell Bay and the Turtle Islands in North Andaman; and Outram Harbour and Kwangtung Strait in the archipelago.