St. Olaf College | Physics Department

"Fire & Ice - When volcanoes and ice mix"

Brian C. Welch

Physics Department
St. Olaf College

Volcanoes occur along rifting and subduction tectonic plate boundaries throughout the world. Many volcanoes located at high latitudes or high elevations are draped by glaciers. Glaciated volcanoes present a unique set of potential eruption hazards to those who live nearby. The glaciers can be rapidly melted by volcanic eruptions to cause mud-flows called lahars. The ice also serves as a source of long-term water that seeps into the active magma chamber where it is converted to steam.

We are working with a hazards-assessment research group at the U.S. Geological Survey's Alaska Volcano Observatory to map the icefield that fills the caldera of a large volcano at the western end of the Alaska Peninsula. Mt. Veniaminof is a large active stratovolcano that is part of the Aleutian Trench subduction system. The last major eruption occurred roughly 7,400 years ago, while smaller caldera-building eruptions have occurred as recently as 1,000 years ago. More recently, a small intra-caldera cinder cone has produced minor ash- and lava-producing eruptions with nearly decadal periodicity.

Nearby villages and salmon fisheries are concerned about the potential for significant mud-flow from the flanks of Mt. Veniaminof. Fieldwork conducted in July 2005 mapped much of the caldera icefield with ice-penetrating radar and simultaneous GPS measurements. Data processing and interpretation in late summer by Mike Helgen and Kieran Cofell-Dwyer at St. Olaf College led to the development of maps of ice thickness, bedrock topography, and ice surface topography. We can use these datasets to analyze the flow of water produced by ice melted by 1983 and 1993 lava flows to determine risks to human activity below the mountain.