Alaskan activity update: Cleveland and Iliamna (updated)

Beautiful, symmetrical Cleveland volcano in the Aleutians, which has been rumbling on and off over the last few months as its lava dome has grown, produced a small eruption last night, reports the Alaska Volcano Observatory:

A small, short duration explosion was detected from Cleveland Volcano on distant seismic stations and infrasound arrays. The time of the explosion was approximately 4:05 UTC March 8 (7:05 PM March 7, AKST.) Weather cloud conditions prevented the detection of an eruption cloud in satellite images or visual observation of the summit. This explosion was similar to recent small events that occurred in December 2011 and produced small ash clouds that dissipated quickly and did not affect air traffic. At this time, no further activity has been detected.

Alaska Public Radio gets a bit over-excited, reporting that ‘Cleveland Volcano has blown its top again’. Talking of Cleveland blowing its top is putting it a little strongly. This latest eruption, as AVO says, was a small event. There may well be more of this kind of small-scale explosion, often caused by localized rock fracturing and movement, as the lava dome continues to grow. Cleveland does not have a real-time seismic monitoring network, but AVO will continue to monitor Cleveland closely. Cleveland is currently at Orange/Watch.

UPDATE. An article in the Anchorage Daily News quotes Steve McNutt of the Alaska Volcano Observatory airing the possibility that the explosion last night may have ‘blasted away a lava dome building inside the volcano’s summit crater’. AVO volcanologists are hoping that satellite images will shortly show what exactly happened during this eruption. It will be interesting to see if all or part of the lava dome has indeed gone missing.

Another Alaskan volcano, Iliamna, which does have real-time seismic monitoring, has been experiencing episodes of increased earthquake activity and is being carefully watched by AVO. So far the alert status for Iliamna has not been raised and remains at Green/Normal.

News
4.1 earthquake comes as scientists watch Alaska’s Iliamna volcano – Alaska Dispatch, 8 March 2012
Explosion detected at Alaska’s Cleveland volcano – Alaska Dispatch, 8 March 2012
Two Alaska volcanoes show signs of activity – Chicago Tribune, 8 March 2012
Seismic stations pick up Cleveland blast – alaskapublic.org, 8 March 2012
Blast shakes restless volcano in remote Aleutian Islands – Anchorage Daily News, 8 March 2012

Information
Global Volcanism Program: Cleveland – summary information for Cleveland (1101-24-)
Global Volcanism Program: Iliamna – summary information for Iliamna (1103-02-)
AVO Cleveland Eruption Page – information on current activity at Cleveland
Alaska Volcano Observatory – AVO main page