Great Sitkin Volcano Grows Restless Near Adak


After more than 40 years of quiet, the Great Sitkin Volcano has grown restless.
The Alaska Volcano Observatory (AVO) raised its alert level last week after Adak residents reported a steam plume rising 1,000 feet above the summit.
AVO Geophysicist Dave Schneider said the plume is just the latest sign of life at Great Sitkin, which has shown increasing seismic activity since the summer of 2016. That’s why the AVO upgraded its alert level from “normal” to “advisory.”
“The earthquake activity has been consistent, it’s on a slight upward trend, [and] it’s continuing," said Schneider. "That’s the kind of signal you look for in the earliest stage of volcanic eruptions.”
Still, it’s too soon to say whether Great Sitkin will actually explode.
Schneider said magma has collected beneath the volcano, but it’s impossible to predict if it’ll push its way to the surface or just cool off and solidify into rock.
“There is no single silver bullet in volcano monitoring," he said. "There is a possibility that it will erupt, but we can’t really provide any short-term forecast on that at this time.”
If the volcano does blow, Schneider said ash could affect flights to and from Adak, which is located about 25 miles west of Great Sitkin.
Worldview-3 satellite image of the summit area of Great Sitkin volcano, November 21, 2017. The area of steaming indicated by the red arrow is the likely source of the volcanic emissions noted and photographed by local observers on Adak, November 19, 2017. The melt depressions on the east side of the 1974 lava flow were evident in a September 14, 2017, satellite image but not present in an April 18, 2017, image indicating that they likely formed during the spring-summer 2017. Image by Chris Waythomas, USGS Volcanoes/ AVO.
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U.S. Geological Survey
Wednesday, November 29, 2017, 12:56 PM AKST (Wednesday, November 29, 2017, 21:56 UTC)

53°55'38" N 168°2'4" W, Summit Elevation 492 ft (150 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Low-level unrest at Bogoslof Volcano is likely continuing. Nothing significant was observed in cloudy satellite images over the past day. Nothing noteworthy was detected in seismic or infrasound data from sensors located on neighboring islands.

Volcanic explosions producing high-altitude (>15,000 ft asl) volcanic clouds remain possible with little or no warning. Some previous explosions have been preceded by an increase in earthquake activity that allowed for short-term forecasts of imminent significant explosive activity. Although we are able to detect energetic explosive activity in real-time, there can be a lag of tens of minutes until we can characterize the magnitude of the event and the altitude of the volcanic cloud. With existing data sources, AVO may not detect low-level unrest, including minor explosive activity. Such low-level periods of unrest and possible explosions could pose hazards near the volcano.

AVO has no ground-based volcano monitoring equipment on Bogoslof volcano. We continue to monitor volcanic activity with satellite images, seismic and infrasound instruments on nearby islands, and lightning data from the World Wide Lightning Location Network.

52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Unrest at Cleveland volcano is continuing at a low level. Nothing significant was observed in cloudy satellite images over the past day. No activity was detected by seismic or infrasound sensors during the past 24 hours.

Lava effusion is typically confined to the summit crater at Cleveland, with the last significant lava flow (that extended to the ocean) occurring in 2001. The lava domes that have been erupted since 2001 have all been destroyed by explosive activity within weeks to months after lava effusion. These explosions typically produce relatively small volcanic ash clouds that dissipate within hours; however, more significant ash emissions have occurred.

Cleveland volcano is monitored with a limited real-time seismic network, which inhibits 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. 

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

Low-level unrest is occurring at Great Sitkin volcano. Nothing of note was observed in seismic data and in cloudy satellite data over the past day.

Great Sitkin volcano is monitored with a local real-time seismic network, which will typically allow AVO to detect changes in unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption would be accomplished using a combination of seismic, infrasound, lightning, and satellite data. The last explosive eruption of Great Sitkin volcano occurred in February, 1974 and resulted in at least one ash cloud that reached about 7.6 km (25,000 feet) above sea level. The 1974 eruptive period also resulted in a lava flow of about 600,000 square meters that was emplaced on the floor of the snow-and-ice filled summit crater. 


Information on all Alaska volcanoes is available at : 

For definitions of Aviation Color Codes and Volcano Alert Levels, see:





Michelle Coombs, Scientist-in-Charge, USGS (907) 786-7497

Jeff Freymueller, Coordinating Scientist, UAFGI (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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