VOLCANOES

Alaska contains over 100 volcanoes and volcanic fields which have been active within the last one and a half million years. Over 40 of these have been active in historic time. These make up about 80% of all active volcanoes in the United States and 8% of all active above-water volcanoes on earth. Hardly a year goes by without a major eruption from a volcano in the Aleutian Arc. The series of 1989-90 eruptions from Mt. Redoubt was the second-most costly in the history of the United States, and had significant impact on the aviation and oil industries, as well as the people of the Kenai Peninsula.

The three eruptions of Mt. Spurr's Crater Peak in 1992 deposited ash on Anchorage and surrounding communities, closing airports and making even ground transportation difficult. Air traffic was disrupted as far east as Juneau. The 1912 Katmai eruption, which formed the Valley of Ten Thousand Smokes on the Alaska Peninsula, was the largest 20th century eruption on earth.