ALASKA VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Saturday, July 24, 2021, 11:23 AM AKDT (Saturday, July 24, 2021, 19:23 UTC)


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

A new small ~50 m (~150 ft) diameter area of uplift in the center of the crater suggestive of rising magma near the surface was identified in satellite imagery from July 22 prompting AVO to increase the Aviation Color Code to ORANGE and the Alert Level to WATCH yesterday afternoon. Small earthquakes were detected throughout the past day but no explosive activity was observed in local and regional infrasound data. Clouds obscured views of the volcano by satellite but sulfur dioxide emissions were possibly detected. AVO will continue to closely monitor this new lava-dome like feature.

Renewed explosive activity or lava effusion remain possible outcomes of the current period of unrest. This is not certain and a decline in unrest to background levels of activity is also possible. Great Sitkin volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.


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 volcano over the past day. Seismicity is above background but no evidence of explosive activity was detected in seismic or infrasound data. Sulfur dioxide emissions were observed in satellite data and robust steaming from the active vent was observed in web camera images from last night.

Small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Cerberus and ash clouds under 10,000 ft above sea level are typical of recent activity at Semisopochnoi. Small explosions may occur without warning and could be undetected by regional infrasound sensors and cloudy weather conditions.

Semisopochnoi is monitored by local seismic and infrasound sensors, satellite data, regional infrasound, and lightning detection instruments.


PAVLOF VOLCANO (VNUM #312030)
55°25'2" N 161°53'37" W, Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest continues at Pavlof volcano over the past day. Seismic tremor continues to be detected but no evidence of explosive activity was observed in seismic or infrasound data. No activity was observed in partly cloudy satellite and clear web camera views.

The level of unrest at Pavlof can change quickly and the progression to eruptive activity can occur with little or no warning. AVO continues to monitor Pavlof closely and will provide any new information about the status of the volcano when or if it becomes available.

Pavlof is monitored by local seismic and infrasound sensors, satellite data, web cameras, and distant infrasound and lightning networks.


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 continues at Cleveland volcano over the past day. Seismicity has been at very low levels and no evidence of explosive activity was detected in seismic or regional infrasound data. Moderately elevated surface temperatures were observed within the summit crater in satellite data from yesterday.

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 operational, Cleveland volcano is monitored by only two seismic stations, which restricts AVO's ability to precisely locate earthquakes and 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.


GARELOI VOLCANO (VNUM #311070)
51°47'21" N 178°47'46" W, Summit Elevation 5161 ft (1573 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest continues at Gareloi volcano over the past day. Seismicity continues to be above background levels. No explosive activity was detected in seismic or infrasound data. No activity was observed in cloudy satellite and web camera views.

Gareloi volcano persistently emits magmatic gases from a fumarole field on the south crater and commonly exhibits low-level seismic activity. These observations suggest the presence of shallow magma and potential interaction with a hydrothermal system. The current increase in seismicity likely reflects a change to the magmatic-hydrothermal system, but it is not clear that the likelihood of a volcanic eruption has increased. AVO will continue to monitor activity to determine if the recent changes are related to influx of new magma or other changes to the magmatic system.

Gareloi is monitored by a local seismic and infrasound network, satellite data, and regional infrasound and lightning-detection 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

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CONTACT INFORMATION:

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

David Fee, Coordinating Scientist, UAF 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.