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ALASKA VOLCANO OBSERVATORY
Wednesday September 11, 2002 2:30 PM ADT (2230 UTC)
MT. VENIAMINOF VOLCANO (CAVW #1102-07)
Summit Cone Elevation 7,073 ft (2,156 m)
Current Level of Concern Color Code: YELLOW
On September 10, AVO detected minute-long pulses of low-frequency tremor occurring every 2-5 minutes on several seismic stations at Mt. Veniaminof volcano. This type of seismicity is indicative of volcanic unrest. Tremor amplitudes gradually increased throughout the day, then remained constant overnight. Amplitudes have fluctuated today, but remain at levels similar to yesterday afternoon. Retrospective analysis of seismic data suggests tremor began as early as September 8th. AVO has not received any visual reports of anomalous activity at Veniaminof. Poor weather conditions have limited satellite observations.
Mt. Veniaminof volcano is an andesitic stratovolcano with an ice-filled 10-km diameter summit caldera located on the Alaska Peninsula, 775 km (480 mi) southwest of Anchorage, and 35 km (22 mi) north of Perryville. Veniaminof is one of the largest (~ 300 km3) and most active volcanic centers in the Aleutian Arc and has erupted at least 12 times in the past 200 years. The most recent eruption of the volcano occurred in 1993-95 and was a moderate Strombolian eruption from the main intracaldera cone in the northwest sector of the caldera above Cone Glacier. The eruption was characterized by intermittent low-level emissions of steam and ash, and a small lava flow was extruded into the summit caldera ice field producing an ice pit. Previous historical eruptions have produced ash plumes that reached 6,000 m (20,000 ft) above sea level and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano.
AVO has been receiving data from the Mt. Veniaminof seismic network since late June 2002. Sufficient time has passed for AVO to have a good understanding of background seismicity levels and station reliability. We are now adding Mt. Veniaminof to our seismically-monitored volcanoes and initiating it at Level of Concern Color Code YELLOW because of the anomalous seismicity. AVO will continue to monitor the situation closely and will issue further updates as information becomes available.