(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20180627/1849Z)
(3) Volcano:	Great Sitkin (VNUM #311120)
(4) Current Color Code:	GREEN
(5) Previous Color Code:	YELLOW
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:
(8) Volcano Location:	N 52 deg 4 min W 176 deg 6 min
(9) Area:	Aleutians
(10) Summit Elevation:	5709 ft (1740 m)
(11) Volcanic Activity Summary:	Earthquake activity at Great Sitkin Volcano has declined gradually and no further indications of increasing unrest have been observed since AVO detected a brief steam and ash explosion on June 10. For the time being, the volcano has returned to normal background levels of activity and AVO is thus lowering the Aviation Color Code and Alert Level to GREEN/NORMAL. 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.
(12) Volcanic cloud height:	not applicable
(13) Other volcanic cloud information:	Unknown
(14) Remarks:	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.
(15) Contacts:	Michelle Coombs, Scientist-in-Charge, USGS mcoombs@usgs.gov (907) 786-7497 Jeff Freymueller, Coordinating Scientist, UAFGI jfreymueller@alaska.edu (907) 322-4085
(16) Next Notice:

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AVO/USGS Volcanic Activity Notice

Volcano: Great Sitkin (VNUM #311120)

Current Volcano Alert Level: NORMAL
Previous Volcano Alert Level: ADVISORY

Current Aviation Color Code: GREEN
Previous Aviation Color Code: YELLOW

Issued: Wednesday, June 27, 2018, 10:49 AM AKDT
Source: Alaska Volcano Observatory
Notice Number:
Location: N 52 deg 4 min W 176 deg 6 min
Elevation: 5709 ft (1740 m)
Area: Aleutians

Volcanic Activity Summary: Earthquake activity at Great Sitkin Volcano has declined gradually and no further indications of increasing unrest have been observed since AVO detected a brief steam and ash explosion on June 10. For the time being, the volcano has returned to normal background levels of activity and AVO is thus lowering the Aviation Color Code and Alert Level to GREEN/NORMAL.

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.

Recent Observations:
[Volcanic cloud height] not applicable
[Other volcanic cloud information] Unknown

Remarks: 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.

Contacts: Michelle Coombs, Scientist-in-Charge, USGS
mcoombs@usgs.gov (907) 786-7497

Jeff Freymueller, Coordinating Scientist, UAFGI
jfreymueller@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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