The Alaska Volcano Observatory (AVO) has experienced failure of all monitoring instruments at Aniakchak Volcano and can no longer seismically monitor unrest at the volcano. The final station failure was confirmed this week. As a result AVO is unable to (1) assess whether this volcano may be building towards an eruption and (2) quickly confirm or dismiss reports of activity. Because this volcano is no longer seismically monitored, it will move from volcano alert level Normal and Aviation Color Code Green to "unassigned". As at other volcanoes without real-time seismic networks, AVO will continue to use satellite and infrasound data, and reports from pilots and ground observers to detect signs of eruptive activity.
Aniakchak Volcano is located on the Alaska Peninsula about 670 km (416 mi) southwest of Anchorage, Alaska in the Aniakchak National Monument. The volcano is a 10-km-wide (6 mi), 0.5- to 1.0-km-deep (1,640 to 3,281 ft) caldera that has been the source of many violent, explosive eruptions in the past 1,000 years. The last eruption at Aniakchak occurred in 1931 producing a large ash cloud that extended over much of the Alaska Peninsula and south-central Alaska and is the second largest explosive eruption historically in Alaska.
AVO has also experienced numerous station failures at Fourpeaked, Isanotski, Fisher, Shishaldin, Westdahl, and Gareloi volcanoes and many of the stations that continue to work provide data only intermittently. Because we have lost the capacity to reliably identify and locate earthquakes and other seismic indicators of unrest, our ability to monitor volcanic activity and forecast eruptions in advance at these volcanoes is heavily impaired. These volcanoes currently remain on our list of seismically monitored volcanoes because we maintain a minimal capability to detect anomalous activity through intermittent data transmission or at least one functional station. Although we may be able to detect an eruption seismically, we may not be able to identify precursory seismicity and provide advance warning.
The status of the impaired networks may change in coming weeks and months. Seismic stations are partially solar-powered and some may resume operating as daylight hours increase in the spring. AVO will continue to attempt repairs as conditions permit. We will update this information statement as appropriate, or if it becomes clear that we can no longer seismically monitor specific volcanoes.
We continue to monitor all Alaskan volcanoes with satellite and regional infrasound data. Additionally some volcanoes also are monitored with real-time GPS and webcams. Although we cannot forecast eruptions with these data, we may detect eruptions with a delay of tens of minutes to hours in some cases. However poor weather, common in the North Pacific, can also prohibit detection of significant eruptions using these alternate data sources.
AVO can no longer seismically monitor the following volcanoes because of seismic station outages. As a result, AVO is unable to (1) assess whether these volcanoes may be building towards an eruption and (2) quickly confirm or dismiss reports of activity at these volcanoes.
Because these volcanoes are no longer seismically monitored, they will move from volcano alert level Normal and aviation color code Green to "unassigned". They will likely remain without real-time seismic monitoring until next summer, when necessary upgrades at these and other networks will occur. As at other volcanoes without real-time seismic networks, AVO will continue to use satellite data and reports from pilots and ground observers to detect signs of eruptive activity.