Summary
Iliamna Volcano is a 3,053-meter-high, ice- and snow-covered stratovolcano in the southwestern
Cook Inlet region about 225 kilometers southwest of Anchorage and about 100 kilometers
northwest of Homer. Historical eruptions of Iliamna Volcano have not been positively
documented; however, the volcano regularly emits steam and gas, and small, shallow earthquakes
are often detected beneath the summit area. The most recent eruptions of the volcano occurred
about 300 years ago, and possibly as recently as 90-140 years ago. Prehistoric eruptions have generated
plumes of volcanic ash, pyroclastic flows, and lahars that extended to the volcano flanks
and beyond. Rock avalanches from the summit area have occurred numerous times in the past.
These avalanches flowed several kilometers down the flanks and at least two large avalanches
transformed to cohesive lahars. The number and distribution of known volcanic ash deposits from
Iliamna Volcano indicate that volcanic ash clouds from prehistoric eruptions were significantly
less voluminous and probably less common relative to ash clouds generated by eruptions of other
Cook Inlet volcanoes. Plumes of volcanic ash from Iliamna Volcano would be a major hazard to
jet aircraft using Anchorage International Airport and other local airports, and depending on wind
direction, could drift at least as far as the Kenai Peninsula and beyond. Ashfall from future eruptions
could disrupt oil and gas operations and shipping activities in Cook Inlet. Because Iliamna
Volcano has not erupted for several hundred years, a future eruption could involve significant
amounts of ice and snow that could lead to the formation of large lahars and downstream flooding.
The greatest hazards in order of importance are described below and shown on plate 1.
|
First posted April 18, 2000
Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge.
|