Printer friendly versionAVO/USGS Volcanic Activity Notice
Volcano: Great Sitkin
Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: NORMAL
Current Aviation Color Code: YELLOW
Previous Aviation Color Code: GREEN
Sunday, July 1, 2018, 10:37 AM AKDT
Alaska Volcano Observatory
N 52 deg 4 min W 176 deg 6 min
5709 ft (1740 m)
Volcanic Activity Summary: Earthquake activity at Great Sitkin Volcano has increased above background levels over the past day. Numerous small, shallow earthquakes are occurring beneath the summit at rates as high as 10-20 per hour. It is uncertain if this unrest will lead to any eruptive activity but this remains a possibility given the general degree of unrest at Great Sitkin over the past several months. Thus AVO is raising the Aviation Color Code and Alert Level to YELLOW /ADVISORY.
AVO detected a brief steam and ash explosion at Great Sitkin on June 10, and earthquake activity then declined to background levels over a period of about 2 weeks. Over the past several days, nothing significant has been observed in satellite data and no other signs of unrest have been detected or reported to AVO.
Great Sitkin Volcano is monitored by a five-station seismic network on Great Sitkin Island and with additional seismic stations on the nearby islands of Igitkin, Adak, Kagalaska, and Kanaga. A six-element infrasound array to detect explosions (atmospheric pressure waves) was installed on Adak Island in June, 2017, although it is currently (June 2018) only partly operational. AVO also uses satellite imagery to monitor Great Sitkin Volcano.
[Volcanic cloud height] not applicable
[Other volcanic cloud information] Unknown
Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It is located 43 km (26 miles) east of the community of Adak. Great Sitkin erupted at least three times in the 20th century, most recently in 1974. That eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft above sea level. A poorly documented eruption occurred in 1945, also producing a lava dome that was partially destroyed in the 1974 eruption. A seismic swarm occurred from July 2016 through the end of 2017.
Michelle Coombs, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Jeff Freymueller, Coordinating Scientist, UAFGI
email@example.com (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.