Aleutian Islands
The Aleutian Islands form a curving arc of volcanically active and earthquake-prone islands stretching
southwest for 1,900 km from the Alaska Peninsula towards the Siberian peninsula of Kamchatka. The islands
— around 150 in number — form a barrier between the Pacific Ocean on the south and the Bering
Sea on the north.
Although forming a continuous chain of islands, they are divided in to several main groups (the 13 main islands are shown in parenthesis): The Fox Islands (Akutan, Umnak, Unalaska, and Unimak), the Andreanof Islands (Amlia, Adak, Atka, Kanaga, and Tanaga), the Rat Islands (Amchitka and Kiska) and the Near Islands (Agattu and Attu). The largest island is Unimak — located off the tip of the Alaska Peninsula — with an area of 4,118 km². Smaller island groups include: the Delarof Islands (located at the western end of the Andreanof Islands), the Krenitzin Islands (at the eastern end of the Fox Islands), the Islands of Four Mountains (at the western end of the Fox Islands) and the Semichi Islands (at the eastern end of the Near Islands).
The islands of the Aleutians are mountainous, being the emergent peaks of a submarine mountain range — part the so-called Pacific Ring of Fire. They have formed — and continue to be shaped by — the movement of the Pacific plate downwards beneath the Bering Sea plate. Strong earthquakes and active volcanism are common. Of the 76 volcanoes occurring within the Aleutian chain, 40 are known to have erupted within the last 250 years.
The Aleutians have an almost barren appearance, being largely treeless — a vegetation type classified as terrestrial-marine tundra. In exposed areas and at higher elevations vegetation consists of dwarf shrub communities. Lower elevations support grass and herb covered lands dominated by Bluejoint (Calamagrostis canadensis) as well as low scrub communities. High rainfall and fog helps to support extensive bog and marsh lands with prolific communities of mosses, lichens and ferns.
Most of the islands lie within the Aleutian Islands Wilderness — part of the Alaska Maritime National Wildlife Refuge.
In addition to the islands that extend westwards from the tip of the Alaska Peninsula, the Aleutian Islands are generally considered to include also those islands and groups of islands that lie off the southern third of the Alaska Peninsula. This includes the Sanak, Pavlof and Shumagin Islands. In all, there are around two dozen larger islands and hundreds of small islets.
At the extreme western end of the Aleutian Islands lie the Russian owned Komandor Islands. Although geologically and ecologically they can be described as part of the Aleutian chain, they are not usually considered as part of the Aleutians.
