Author: Chris Waythomas, U.S. Geological Survey, Alaska Volcano Observatory (AVO), Anchorage, Alaska
The AVO is a partnership of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute (UAFGI), and the Alaska Division of Geological and Geophysical Surveys (ADGGS).
The Aleutian Islands are part of the Aleutian arc, one of the most active volcanic provinces on Earth, and they owe their existence to long-term volcanic activity. Volcanoes and their products dominate the landscape. Volcanic ash from explosive eruptions in this area poses a substantial threat to the several hundred jet aircraft that fly over the region every day. To address the hazards associated with explosive ash producing eruptions, the Alaska Volcano Observatory (AVO) monitors and studies volcanoes in the Aleutian Islands and disseminates information regarding the status of unrest at active volcanoes in this area as well as other parts of Alaska.
Reporting Volcanic Unrest
AVO provides regular updates on volcanic unrest when a major change in the status of an Alaskan volcano occurs. Information is distributed to state and federal agencies, municipalities, industry, and the general public through the USGS Volcano Notification System (VNS). This information is also posted on the AVO web page (www.avo.alaska.edu) and a short synopsis is distributed via Twitter and Facebook.
Seismic Networks, Satellite Data, and Infrasound
AVO operates seismic networks on 32 historically active volcanoes and monitors all 52 historically active volcanoes in Alaska (including those in the Aleutian Islands) using remotely sensed data from satellites, observations from local observers and pilots, and other types of geophysical monitoring equipment. The seismic networks provide real-time information on earthquake activity that occurs at or beneath the volcano. An increase in earthquake activity is often the best way to determine that a volcano may be progressing toward an eruption. The number and type of earthquakes provide important information used to give advance warning of an eruption. Once a volcano becomes restless, AVO provides information about potential hazards that may affect life and property. The principal hazard of concern to AVO is airborne volcanic ash and its impact on aircraft. Additional hazards of concern include ash fallout, volcanic mudflows or lahars, and rapidly flowing mixtures of hot rock fragments, fluids, and gases known as pyroclastic flows.
AVO also does routine analyses of satellite data to identify thermal features indicative of magma at or near the surface. Usually, elevated levels of seismicity correspond with the appearance of thermal features at a restless volcano and the satellite information helps confirm that an eruption is occurring. Significant eruptive activity is typically explosive and results in the production of ash clouds, which can be detected and tracked in satellite data. Explosive eruptions usually generate pressure waves that travel through the air, which can be detected at locations hundreds of kilometers from the erupting volcano. Explosion signals detected by infrasound monitoring equipment are becoming an increasingly important tool for eruption detection at volcanoes that are not seismically monitored.
AVO in the Aleutian Islands
AVO scientists have not worked extensively in the Aleutian Islands. AVO did several weeks of helicopter-supported fieldwork in the western Aleutian Islands in 2003 and 2005, and preliminary geologic maps and hazard assessments were completed for Gareloi and Tanaga Volcanoes. Reconnaissance-level field visits were made to Little Sitkin and Semisopochnoi. In the late 1990’s AVO had brief field projects on Kanaga, Great Sitkin, and Unimak Islands, and also produced preliminary geologic maps and hazard assessments of Fisher caldera and Great Sitkin, Kanaga, Westdahl and Shishaldin volcanoes. AVO was very involved in the monitoring, analysis, and eruption response to the 2008 Kasatochi eruption, and continues to have a role in the study of ecosystem recovery and post-eruption landscape adjustment and erosion.
Funding for monitoring of Alaskan volcanoes, especially the hard-to-maintain volcanoes in the Aleutian Islands, has been in decline for several years. AVO has deferred maintenance on geophysical monitoring networks at many previously well-monitored Alaskan volcanoes including those in the Aleutian Islands. As a result, many seismic stations have gradually become inoperable or are functioning intermittently. As of mid-January 2014, only about half of AVO’s roughly 200 seismic stations were operating. Ground-based seismic monitoring is currently not operational or is functioning poorly at Gareloi, Shishaldin, Westdahl, and Semisopochnoi, which are considered high threat volcanoes. Ground-based seismic monitoring at Fisher caldera, Little Sitkin, and Isatnoski also is compromised or not functioning, although these volcanoes pose a lesser threat. To address these shortcomings in monitoring capability, AVO makes routine observations to detect unrest at all Alaskan volcanoes using satellite and regional infrasound data. It is not possible to forecast eruptions with these data, but eruption detection is possible, although delays in reporting unrest of tens of minutes to hours in some cases are likely.
The Future of AVO
Over the coming years, AVO will continue to pursue its volcano-monitoring mission, and will engage in geological field studies focused on hazards and past eruptive behavior where possible. Most of AVO’s resources will be directed to study and monitoring the highest threat volcanoes in the Aleutian arc, which are Mount Spurr, Redoubt, Augustine, Akutan, and Makushin volcanoes. Studies at other volcanoes will still take place, but this work will have lesser priority.