Geography of American Samoa
American Samoa is an "unorganized, unincorporated Territory" of the United States, and is the only U.S. possession in the southern hemisphere. It consists of the islands of Tutuila, Manu'a (Ta'u, Ofu and Olosega), Swains Island and Rose Atoll. Its total area is 76.2 square miles.
The Samoan Islands extend from 168 degrees to 173 degrees east longitude, and from 13 degrees to 15 degrees south latitude. American Samoa occupies the 168 degrees-171 degrees longitudinal portion of the archipelago, the eastern part of the Samoan Archipelago. Rainfall varies from 120 to 200 inches annually, with an average temperature of 80 degrees F. The climate is hot and humid; erosion and biodegradation are rapid.
Tutuila and the Manu'a islands are rugged, mountainous volcanic isles, clad in dense tropical rainforest vegetation. The area available for human habitation and the cultivation of crops is limited. The valley bottoms are not very flat and are quite narrow, and the coastal plains are narrow. Recent geomorphological information indicates that many of the valleys were deep embayments when Polynesians first arrived that have subsequently filled in (see Clark & Michlovic 1996). The largest flat area is the Tafuna Plain on the southern side of Tutuila; this is a large volcanic plain. In the twentieth century some areas, such as the perimeter of Pago Pago Bay, have been filled in to provide more flat areas for development.
Swains Island and Rose Atoll are both atolls. Rose Atoll is 80 miles east of Ta'u and consists of two low sandy islands - Rose Island and Sand Island - encompassing a 2000m (6500ft) wide lagoon with a total land and reef area of 1600 acres. Rose Atoll is a U.S. National Wildlife Refuge. Swains Island is ring-shaped atoll encompassing a large brackish water lagoon about 230 miles north of Tutuila; it is privately owned.