Volcanoes: The fire beneath the ice

Posted: Saturday, April 20, 2002

The beautiful mountains west of the Kenai Peninsula include some of the world's most active volcanoes and could rumble to life any day now.

The Chigmit Mountains, the range across from the peninsula, is part of the "Ring of Fire," a string of volcanic and seismic hot spots that circles the Pacific Ocean.

Beneath the Gulf of Alaska, the North Pacific geologic plate slides beneath the continental shelf about as fast as fingernails grow, pushing up the young mountains of the outer Kenai, Kodiak and Prince William Sound. The buried crust breaks up in the planet's molten interior. The melting zone generates lava that pushes toward the surface miles to the northwest.

Alaska volcanoes spew not lava but plumes of airborne ash and avalanches of hot rocks, ash and boiling mud that tumble down their slopes.

Inlet volcanoes have had numerous historic eruptions, blanketing the ground with powdery ash and endangering aircraft.

The Alaska Volcano Observatory in Anchorage monitors the region. It posts information about the peaks and updates on their activity on its Web site at fm.gi.alaska.edu/.

Plans are on the drawing board to build a North Pacific Volcano Learning Center near Stariski Creek between Ninilchik and Anchor Point. The proposed facility would include public educational displays and monitoring programs.

Volcanoes visible from the peninsula, north to south, are:

Mount Spurr, 11,070-feet tall, lies nearly due west of Anchorage. It erupted in 1953 and 1992, dumping ash on the city and closing its airport.

Mount Redoubt, the 10,197-foot symmetrical peak dominates the western horizon from the central peninsula. Beginning Dec. 14, 1989, and extending into 1990, it sent mushroom clouds of ash to an altitude of 12 miles. The eruption shut down air traffic and threatened the Drift River Oil Terminal. It also erupted from 1966 to 1968.

Mount Iliamna, 10,016-feet tall and just south of Redoubt, has been quiet in historic times. Glaciers radiate from its rambling multiple peaks.

Mount Augustine near Homer occupies its own island in Kamishak Bay. The cone rises 4,025 feet. Young and restless, Augustine erupted in 1963, 1976 and 1986. It poses an additional threat because its unstable dome could break apart, fall into the sea and generate a tsunami.

Mount Douglas is the southernmost inlet volcano. The 7,000-foot peak has not erupted in historic times, but scientists report activity since the last ice age.

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