ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Saturday, June 20, 2020, 11:40 AM AKDT (Saturday, June 20, 2020, 19:40 UTC)

The Weekly Update was inadvertently sent out earlier today as a Daily Update. This release corrects that error.

MAKUSHIN VOLCANO (VNUM #311310)
53°53'24" N 166°55'30" W, Summit Elevation 5906 ft (1800 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Seismic unrest at Makushin continues, with small earthquakes being detected in a region about 12 km ( 7.5 miles) southeast of the summit. Clear satellite images from last night show no evidence of increased heating of the summit and clear web camera images from this morning show typical minor steaming from summit fumaroles.

The earthquakes that began earlier this week may be associated with volcanic unrest but there have been no signs of deformation or surficial activity observed in other monitoring data. It is likely that we would see additional signs of unrest prior to eruptive activity, should it occur. The volcano is monitored with a network of seismic and GPS instruments, a web camera, satellite data, and regional infrasound and lightning detection instruments.

If an eruption were to occur, the main hazard would likely be from airborne ash and ash fall. Wind trajectory plots and hypothetical ash fall model information is available at https://www.avo.alaska.edu/activity/Makushin.php These models are updated twice per day in a hypothetical mode and would be update immediately if there was an eruption. Seismic data, web camera images and information products are also available at this site.

VENIAMINOF VOLCANO (VNUM #312070)
56°11'52" N 159°23'35" W, Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Infrequent periods of low-amplitude seismic tremor continue, but no eruptive activity has been observed over the past day. Web camera images from this morning so no signs of activity from the summit cone (the site of historical eruptions). Satellite observations of the volcano were mostly obscured by clouds over the past day.

This seismic activity that was observed earlier in the week typically precedes eruptive activity at Veniaminof but does not mean that an eruption will occur. Eruptive activity usually consists of minor ash emissions, lava fountaining and lava flows from the small cone in the summit caldera. Ash emissions are typically confined to the summit crater, but larger events can result in ash fall in nearby communities and drifting airborne ash.

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. AVO combines seismic, infrasound, lightning, and satellite data for rapid detection of such events.

SEMISOPOCHNOI VOLCANO (VNUM #311060)
51°55'44" N 179°35'52" E, Summit Elevation 2625 ft (800 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest continues at Semisopochnoi. Infrequent periods of low-amplitude tremor were observed over the past day and sulfur dioxide emissions were detected in satellite data from yesterday afternoon. Tremor amplitude and frequency of occurrence are greatly reduced compared to earlier in the week. Partly cloudy satellite images show no evidence of eruptive activity and no pressure waves produced by rapid degassing or explosions were detected.

Semisopochnoi is monitored by local seismic sensors, satellite data, and lightning detection networks. An infrasound array on Adak Island may detect explosive emissions from Semisopochnoi with a slight delay (approximately 13 minutes) if atmospheric conditions permit.

CLEVELAND VOLCANO (VNUM #311240)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest likely continues at Cleveland. No activity was seen in clear satellite views or detected on regional geophysical networks over the past day. The local geophysical stations and web camera at Cleveland are currently unavailable due to an ongoing network outage.

Episodes of lava effusion and explosions can occur without advance warning. Explosions from Cleveland are normally short duration and only present a hazard to aviation in the immediate vicinity of the volcano. Larger explosions that present a more widespread hazard to aviation are possible, but are less likely and occur less frequently.

When the network is operational, Cleveland volcano is monitored by only two seismic stations, which restricts AVO's ability to detect precursory unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption may be possible using a combination of seismic, infrasound, lightning, and satellite data.

SHISHALDIN VOLCANO (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Seismic unrest continues at Shishaldin, but at at rate approaching background conditions. Satellite data and web camera observations were mostly obscured by clouds over the past day. No explosive activity was detected by regional infrasound sensors.

Although unrest is currently at very low levels, conditions could change rapidly with minimal warning, and eruptive activity in the summit crater could resume. If eruptive activity does resume, lava flows, lahars, and ash-producing events could occur.

Shishaldin is monitored by local seismic and infrasound sensors, satellite data, web cameras, a telemetered geodetic network, and distant infrasound and lightning networks.

GREAT SITKIN VOLCANO (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest continues at Great Sitkin. Small local earthquakes continued over the past day. No explosive activity was detected by regional infrasound sensors. Satellite and web camera images were mostly obscured by clouds over the past day.

Great Sitkin volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.

OTHER ALASKA VOLCANOES

Information on all Alaska volcanoes is available at : http://www.avo.alaska.edu.

For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://www.avo.alaska.edu/color_codes.php

SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/

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CONTACT INFORMATION:

Matt Haney, Acting Scientist-in-Charge, USGS
mhaney@usgs.gov (907) 786-7497

David Fee, Coordinating Scientist, UAFGI
dfee1@alaska.edu (907) 322-4085

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

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