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The Alaska Region
The 2500-km-long Aleutian arc is a chain of large calc-alkaline stratovolcanoes and impressive calderas. This largely uninhabited arc, whose western end lies across the International Date Line and reaches within 900 km of Kamchatka, is responsible for nearly all the historical volcanism of Alaska. Alaska possesses more than half the Holocene volcanoes in the United States, but has produced nearly 70% of its historical eruptions, including many of its most explosive. The Wrangell Mountains, near the Canadian border to the east, include some of world's largest andesitic shield volcanoes, including Mount Wrangell itself, a glacier-covered caldera which has erupted in the past century, and the Mount Churchill-Bona complex, at 5005 m the highest volcano in the U.S. and the 4th highest in North America. Churchill was the source of the bilobate rhyodacitic White River Ash deposits, produced during two of the largest explosive eruptions in North America during the past 2000 years. Basaltic lava fields are scattered throughout the Bering Sea, the western interior, and the southeastern panhandle of Alaska.
Western record keeping began in 1741 when Vitus Bering (see introduction to Regions 09 & 10, above) landed in Alaska, but these commonly cloud-covered volcanoes were only occasionally documented in the following decades. Eruption reporting began with Kasatochi in 1760 (which also had a major eruption in 2008 that devastated the entire island and extended its shoreline); 4 more had erupted by 1768 and there has been a steady increase since. The first government of Russian America was set up near Sitka in 1799, and in 1867 the US bought Alaska from Russia for $7.2 million. Gold was discovered in 1896, and the population of this vast region had grown substantially by 1912, when the major eruption of Novarupta/Katmai, the world's largest in the 20th century, brought widespread attention to Alaska's many volcanoes. Recognition of their significance during WW-II led to a major USGS mapping program in the Aleutians during the early 1950s, bringing a quantum jump to understanding of these volcanoes. In 1959 Alaska entered the US as our 49th state, ranking first in area, 49th in population, and first in volcanism, with 42 of the nation's 65 historically active volcanoes.
Alaska has the world's largest proportion of stratovolcanoes (72%), several other regions have higher totals. Only Indonesia, Japan, and South America have had more volcanoes erupt during the past 100 years. Most volcanoes lie in sparsely populated areas, however, and only three Alaskan eruptions have caused fatalities. Weather in the Aleutian arc is notoriously bad, and eruptions take place even today without being observed. Only Antarctica has fewer people living within 100 km of volcanoes, but the Aleutian arc underlies the heavily traveled Great Circle commercial air corridor between the mainland U.S. and Asia, and several Alaskan eruptions have produced ash plumes that have damaged commercial aircraft. The Alaska Volcano Observatory has increased monitoring capability on many of these volcanoes to help anticipate and mitigate the impact of ash eruptions on aircraft.
Alaska is the latest region to be covered in the CAVW series. That catalog, published in the USGS Open-File Report format by Tom Miller and colleagues at the Alaska Volcano Observatory, and two other book-length treatments of Alaskan volcanoes (starred under REFERENCES - 1100) bring excellent modern coverage to this important volcanic group. These authors have not all followed the CAVW numbering of clockwise progression around the Pacific Rim, but naming has been reasonably consistent throughout. The Alaska Volcano Observatory, a collaborative program involving the USGS, the Geophysical Institute of the University of Alaska, and the Alaska Division of Geological & Geophysical Surveys, now posts detailed information about Alaska's present and past volcanism on the AVO website.
List of Holocene volcanoes in the Alaska region.