Event Name : Veniaminof 2008/2
|Start:||February 22, 2008 ± 7 Days||Observed|
|Tephra plume: ||
|MaxVEI: ||1 ||
|ColHeight: ||3050 m ||
From AVO's Volcanic Activity Notice on February 22, 2008: "On February 22, 2008, several minor bursts of ash from Veniaminof were observed on AVO webcam images and recorded in seismic data this morning. The bursts rose less than 9000 ft ASL (only a few hundred feet above the active intracaldera cinder cone), and were confined to the caldera." Since February 22, AVO has continued to note elevated seismicity at Veniaminof and to view steam and occassional ash in Veniaminof webcam images.
From Neal and others (2011): Intermittent low-level activity at Veniaminof continued in 2008 with minor phreatic ash emissions and periods of slightly elevated seismicity. Beginning in mid-February, seismicity (in the form of 1-2 minute tremor bursts with occasional harmonic banding) became slightly more energetic and AVO staff noted vapor plumes in web camera images from Perryville, 35 km (22 mi) south of the volcano.
"A weak ash emission event was captured on the AVO web camera on February 22, noted during routine analysis by AVO and reported via email by a watchful citizen, prompting AVO to issue a YELLOW/ADVISORY. Minor eruptions of ash occurred about once every 20-30 minutes over several hours, producing small plumes that rose at most about 300 m (1,000 ft) above the intracaldera cinder and spatter cone [fig. 8; imageid 14025]. Some of these small bursts could be correlated with a clear multi-station seismic event [see fig. 9 in original text]. Ash clouds dissipated rapidly and did not extend beyond the caldera rim; in between bursts, a white water vapor plume was common. These were similar to those seen during 2005 (McGimsey and others, 2007).
"On February 23, only a white vapor plume rose above the cone. Tremor bursts continued, increasing in intensity (both number of discrete volcano-tectonic earthquakes (VTs) and longer tremor episodes) on February 29. In response, AVO initiated additional checks of seismic data for the volcano and implemented a Real Time Seismic Amplitude (RSAM) alarm for Veniaminof (Murray and Endo, 1992). A pilot reported ash to 10,000 ft (3,050 m) on February 29 and the NWS issued a SIGMET. Perryville residents using a telescope reported seeing large blocks, orange in color, thrown out of the plume during daylight hours on February 28. The lack of a thermal anomaly or night time reports of incandescence suggests these ballistic objects probably were altered and oxidized lava bombs rather than fresh, hot (and thus, 'glowing') magmatic ejecta.
"In addition to more frequent analysis of seismicity, AVO initiated automatic ash dispersal runs using the PUFF model (Searcy and others, 1998) for hypothetical Veniaminof eruptions.
"Seismicity and emissions decreased in early March and AVO discontinued the heightened seismic watch. A March 4 ASTER image showed a small vapor plume emanating from the intracaldera cone but no anomalous temperatures indicative of significant activity (R.L. Wessels, USGS, written commun., 2008).
"On May 3, after several months of no further ash emission events, AVO downgraded Veniaminof to GREEN/NORMAL, where it remained for the rest of 2008 and into 2009."