ATTU ISLAND, ALASKA: AN INTERESTING TECTONIC HISTORY AND A BIRD-WATCHER'S WONDERLAND

Attu Island  (located at approximately 52.8 degrees North latitude and 173 degrees East longitude) is the most westward island in Alaska and is 1600 miles southwest of Anchorage, Alaska (Fig. 1).

Figure 1. Location of Attu Island, indicated by the red arrow, in the Pacific Northwest (Google Earth image).

The island is near the western tip of the Aleutian Islands chain, and it is one of the westernmost points of the United States. Its location required a major redrawing of the western boundary of the International Date Line (see the “V” shaped line on Figure 2---just west of the lettering for “Near Islands”). 

Figure 2. Location of Attu Island (indicated by the red arrow) relative to the inter-national date line (Rand McNally Earth Map).

The island is located at 53 degrees North latitude North, 173 degrees longitude East, and is 35 miles long. The Russian Kamchatka Peninsula is 208 miles west of Attu.

The island (Fig. 3) was occupied by Japanese forces during World Ware II, and subsequent fierce battles took place there in 1943. Some warfare equipment is still present but very rusted. The Coast Guard was present on the island for quite awhile, but it left in 2010, leaving the island uninhabited.

Figure 3. ERTS imagery of Attu Island, with latitude and longitude;(a Google Earth image).

The island is now a sanctuary for migrating birds (with many species from Asia). The island is a “birder’s paradise,” with about 748 species of birds recognized. In the references below, I have listed a few URL’s in the References herein, if you want to see detailed lists of birds that have seen on the island. A few examples are: Cacking Goose, Green-Winged Teal, Harlequin Duck, Red-Breasted Mergansa, Black-Tailed Godwit, Tuffed Puffin, Laysan Albabross, Snowy Owl, Common Cucko, White-Tailed Eagle, Chinese Pond Heron, etc. Some of the birds are endemic, whereas others migrate from Asia. Literally millions of sea birds visit the island yearly.

The climate on the island is “subpolar oceanic,” which translates into cold, foggy, and rainy. It has 49 inches of rainfall per year. The cold also has allowed a recently recognized glacier (with crevasses) that formed near the top of the highest mountain on the island (3,000 feet in height). Clear days are rare (only about 8 or 10 per year!) on Attu Island; the rest of the time it is overcast, cold, and rainy (not exactly a resort-type place to visit!). On Attu, five or six days a week are likely not to be rainy.

This island is at the western end of a volcanic chain of islands (i.e., the Aleutian Arc) in which volcanic islands have been formed by subduction of the Pacific Plate beneath the North American plate. Attu will be subducted into the Aleutian Trench located immediately southwest of Attu (Fig. 4).

Figure 4. Location of Attu Island (indicated by red arrow) relative to the Aleutian Trench (source National Geographic map, Pacific Ocean Floor, October, 1969).

 As a result of its geologic history, Attu is dominated by volcanic rocks (e.g., andesite and dacite dikes). The oldest rocks on the island are Oligocene-Miocene, about 30 million years in age. Eventually, Attu Island will be subducted back into the Earth’s interior, from which it originally came from.

References;

https://ebird.org/hotspot/L8200014/bird-list

https://fws.gov/refuge/alaska-maritime, visit-us/activities/birding

Wikipedia, 2025.