Web posted Saturday, April 20, 2002

Volcanoes: Homer's view of the Ring of Fire

Those who drive to Homer on a clear day will be familiar with Cook Inlet's volcanoes long before they reach Baycrest Hill. The white giants on the far side of the Inlet slumber peacefully most of the time, but are capable of putting on spectacular displays.

Remember the acronym "AIR" to name the volcanoes on display. Augustine, Iliamna and Redoubt run south to north (or left to right from the vantage of Baycrest Hill). Mount Douglas is farther south yet, but only visible on the clearest of days.

In the not-too-distant future, the proposed North Pacific Volcano Learning Center may provide even more information about the Ring of Fire. A group of lower Kenai Peninsula residents is actively working to build the educational center north of Anchor Point, but it will be several years before their work bears fruit.

photo: culture

Mount Douglas

Mount Douglas is a dissected stratovolcano, about 7,000 feet high, southwest of Homer at the tip of Shelikof Strait. A stratovolcano is one composed of explosively erupted cinders and ash with occasional lava flows. Mount Douglas is covered by the Spotted Glacier and the summit is marked by a small crater lake. Most of the volcano is ice-covered, but isolated outcrops of lava flows are found within the ice. Historically inactive, the presence of unglaciated lava flows and active fumaroles on Mount Douglas indicate some recent activity.

Augustine Volcano is an island volcano in lower Cook Inlet, about 4,025 feet high. Structurally, Augustine consists of a central complex of young lava domes and steep, short lava flows. The center is surrounded by an apron of debris avalanches and pyroclastic flows which form the bulk of Augustine Island. Debris avalanches occur on all flanks of Augustine, indicating repeated collapse of the growing central dome complex. Any debris avalanche activity presents a special hazard in the lower Cook Inlet region -- the impact of such rock slides into the sea can potentially create tsunamis. During the most recent eruptions in 1963-64, 1976 and 1986, much of the Cook Inlet region was affected by ash falls.

Iliamna Volcano is a prominent stratovolcano, part of the Aleutian Range in Lake Clark National Park. At 10,016 feet high it is not a simple symmetrical cone; rather, the present summit peak is the northernmost of four peaks. Most of the volcano is covered by snow and ice, and at least 10 glaciers radiate from its summit area. Little of the original cone remains as the volcano has been deeply eroded and glaciated. Iliamna Volcano has an ice-filled summit crater and has had no recent activity. It is easily discerned from Redoubt by the twin, 7,500-foot peaks that form Iliamna's southern shoulder.

Redoubt Volcano is another stratovolcano, 10,197 feet high, in the Aleutian Range in Lake Clark National Park. Like Iliamna, it is heavily covered by glaciers with an ice-filled summit crater. The crater is the accumulation basin for a large glacier that drains north; deposits of numerous younger and smaller debris flows fill the Drift River canyon and contribute large volumes of sediment to the Drift River delta. Redoubt's most recent activities were during 1966-68 and 1989-90. The '89 eruptions caused air traffic delays throughout Southcentral Alaska.

Photos and information provided by Alaska Volcano Observatory in Anchorage.