Aleutian Islands - Geography

Geography

The islands, known before 1867 as the Catherine Archipelago, comprise five groups (east to west): the Fox, Islands of Four Mountains, Andreanof, Rat, and Near island groups (with Buldir Island halfway between Favian and Diana Islands, but part of neither group). They are all located between 51° and 55° N latitude and 172° E and 163° W longitude. The largest islands in the Aleutians are Attu (the furthest from the mainland), and Unalaska, Umnak, and Akun in the Fox Islands.

The axis of the archipelago near the mainland of Alaska has a southwest trend, but near 179° its direction changes to the northwest. This change of direction corresponds to a curve in the line of volcanic fissures that have contributed their products to the building of the islands. Such curved chains are repeated about the Pacific Ocean in the Kuril Islands, the Japanese chain, and in the Philippines. All these island arcs are at the edge of the Pacific Plate and experience much seismic activity, but are still habitable; the Aleutians lie between the Pacific and North American tectonic plates. The general elevation is greatest in the eastern islands and least in the western. The island chain is a western continuation of the Aleutian Range on the mainland.

The great majority of the islands bear evident marks of volcanic origin, and there are numerous volcanic cones on the north side of the chain, some of them active; many of the islands, however, are not wholly volcanic, but contain crystalline or sedimentary rocks, and also amber and beds of lignite. The coasts are rocky and surf-worn, and the approaches are exceedingly dangerous, the land rising immediately from the coasts to steep, bold mountains.

These volcanic islands reach heights of 6,200 feet (1,900 m). Makushin Volcano (5,691 feet (1,735 m)) located on Unalaska Island, is not quite visible from within the town of Unalaska, though the steam rising from its cone is visible on a (rare) clear day. Residents of Unalaska need only to climb one of the smaller hills in the area, such as Pyramid Peak or Mt. Newhall, to get a good look at the snow-covered cone. The volcanic Bogoslof and Fire Islands, which rose from the sea in 1796 and 1883 respectively, lie about 30 miles (50 km) west of Unalaska Bay...