Towering above Cook Inlet, Mt. Redoubt, at 10,200 feet, is one of the largest volcanoes in Alaska and one of four that pose a threat to Anchorage, the State's largest city. Over the past few weeks, geologists have detected the telltale signs of an imminent eruption which, in this mountain's case, last occurred in 1989-90; on that occasion, the volcano sent rivers of caustic mud into nearby streams and spewed abrasive ash 40,000 feet into the atmosphere. The latter almost brought down one passenger jet and disrupted air travel across much of western North America.
According to the Alaska Volcano Observatory, the State has over 130 volcanoes and volcanic fields, of which more than 50 have been active in the past 250 years; over the past forty years, Alaska has averaged 2 eruptions per year. The great majority of these active volcanoes are in the Aleutian Chain which formed (and continues to form) as a volcanic island arc, just north of the Aleutian Trench; within the latter, the Pacific Plate subducts beneath the North American Plate and its melting (as it nears the mantle) feeds the volcanic activity. Mt. Cleveland, in the central Aleutians, has erupted at least 11 times in the past 25 years.
Earthquakes and volcanism are the most potent reminders that our planet's evolution, which began 4.6 billion years ago, continues today. We are not the culmination of natural history; rather, we are part of it.
