Ash emissions at Veniaminof volcano increased significantly on November 21, 2018, forcing Alaska Volcano Observatory to raise the Aviation Color Code to Red and Volcano Alert Level to Warning.
Veniaminof is generating a plume of ash up to 4.6 km (15 000 feet) above sea level, extending for more than 240 km (150 miles) to the SE, AVO said 19:15 UTC, November 21. "This morning observers in Perryville and webcam views indicated continuous ash emissions. This activity is a significant increase from the past month and AVO is raising the Aviation Color Code to Red and the Volcano Alert Level to Warning."
Landsat 8 false color image (short-wave infrared, near infrared, and red bands) of the Veniaminof eruption from November 19, 2018, showing the active lava flow through low clouds within the caldera and the steam and ash plume drifting to the southeast. Credit: Hannah Dietterich
The November 21, 2018 eruption of Veniaminof volcano as seen from the FAA Perryville webcam, located ~21 miles (~33km) south-southeast of the active vent. Credit: Janet Schaefer
Seismic activity has remained elevated in the past 24 hours, and ramped up around 08:00 UTC before falling slightly throughout the day today, the observatory said 23:40 UTC.
By 11:43 UTC (02:43 AKST), an ash plume was observed in satellite data extending 130 km (80 miles) to the SE, with maximum height estimated at 3.9 km (13 000 feet) asl.
This plume continued to develop throughout the night extending to over 240 km (150 miles).
In response, the national weather service issued a SIGMET.
Clear webcam views in the morning indicated continued ash emission to the SE, and a second plume developed extending over 193 km (120 miles) to the SE. A pilot report from the morning indicated that the ash cloud was below 3 km (10 000 feet).
Ash3d forecasts suggest a possible shift to northerly winds overnight tonight that may result in ash impacts on the community of Perryville, and the National Weather Service has issued an advisory for trace to minor ash fall.
No satellite observations of thermal anomalies associated with the continued lava flow were observed in the last 24 hours, but such signatures could be obscured by increased ash emissions and/or cloud cover.
"Nearly continuous ash emissions continued for much of today with a plume below 15 000 feet asl extending over 400 km (250 miles) to the southeast until around 23:45 UTC (14:45 AKST)," AVO reported 06:08 UTC, November 22.
After that, a short eruptive pulse was visible from the Perryville webcam at 00:26 UTC, November 22 (15:26 AKST, November 21) but largely dissipated by 02:26 UTC (17:26 AKST).
No ash emissions were visible in the last daylight webcam images, and satellite images do not indicate continued ash emissions at this time.
Veniaminof volcano is monitored with a local real-time seismic network, which will typically allow AVO to detect changes in unrest that may lead to a more significant explosive eruption. Rapid detection of such an event would be accomplished using a combination of seismic, infrasound, lightning, and satellite data.
Image credit: NASA/NOAA Suomi NPP/VIIRS. Acquired November 21, 2018
Ash emissions at Veniaminof have decreased but continue at lower levels, AVO said 20:05 UTC, November 22, and lowered the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH.
Ashfall remains possible in nearby communities from current activity, and emissions could increase at any time.
Featured image: Ash plume produced by erupting Veniaminof volcano, Alaska. Credit: NASA/NOAA Suomi NPP/VIIRS. Acquired November 21, 2018