American Samoa is composed of seven main islands totaling 201 square kilometers. Tutuila, Aunu'u, and the Manu'a Group (Ofu, Olosega, Ta'u) are high volcanic islands; Rose and Swains are small coral atolls. Tutuila is about midway between the far larger island of Upolu and the smaller Manu'a Group.
Tutuila is by far the largest island, with a steep north coast cut by long ridges and open bays. The entire eastern half of Tutuila is crowded with rugged jungle-clad mountains, continuing west as a high broken plateau pitted with the verdant craters of extinct volcanoes. The only substantial flat area is in the wide southern plain between Leone and the airport.
Fjordlike Pago Pago Harbor, which almost bisects Tutuila, is a submerged crater, the south wall of which collapsed millions of years ago. Despite the natural beauty, recent studies have shown that the harbor is dying biologically as a result of pollutants dumped by the two tuna canneries and local villagers, and the culminating effect of oil and ammunition spills by the U.S. Navy decades ago. The marinelife of inner Pago Pago harbor is poisonously contaminated by heavy metals and unfit for human consumption. Swimming in the harbor is not a wise idea.