The US Geological Survey operates five volcano observatories, which keep watch on regions of volcanic activity in the United States. The five observatories are for the Cascades, Hawaii, Yellowstone, Long Valley (in California) and Alaska. My web site of the week is for the Alaska Volcano Observatory.
Here’s a description of the Alaska volcanoes from the AVO site:
Alaska contains over 100 volcanoes and volcanic fields which have been active within the last two million years. Over 40 of these have been active in historic time. These volcanoes make up about 80% of all active volcanoes in the United States and 8% of all active above-water volcanoes on earth.
Most of these volcanoes are located along the 2,500 km-long (1,550 mile-long) Aleutian Arc, which extends westward to Kamchatka and forms the northern portion of the Pacific “ring of fire”. Other volcanoes which have been active within the last few thousand years exist in southeastern Alaska and in the Wrangell Mountains. Smaller volcanoes, some active within the last 10,000 years, exist in interior Alaska and in western Alaska as far north as the Seward Peninsula.
Hardly a year goes by without a major eruption from a volcano in the Aleutian Arc. Eruptions in the largely unpopulated western arc often go unremarked by all but volcanologists. The remote volcanoes are potentially hazardous, as jet airplanes which enter eruption clouds often are severely damaged, and sometimes lose all engines temporarily. There are more than 70,000 large aircraft per year, and 20,000 people per day, in the skies over Aleutian volcanoes, mostly on the heavily travelled great-circle routes between Europe, North America and Asia. Volcanoes in the eastern arc, especially those from Cook Inlet volcanoes, can have severe impacts. The series of 1989-1990 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, and disrupted air traffic as far east as Cleveland, Ohio. The 1912 Katmai eruption, which formed the Valley of Ten Thousand Smokes on the Alaska Peninsula was the largest 20th century eruption on earth.
I chose this site because it has a wealth of great pictures and high-resolution topographic maps:
Grace and Peace