Report on Shishaldin (United States) — February 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 2 (February 1987)
Managing Editor: Lindsay McClelland.
Shishaldin (United States) Small ash eruption followed by steaming
Please cite this report as:
Global Volcanism Program, 1987. Report on Shishaldin (United States). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 12:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198702-311360.
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
On 15 February at 1600, Marsha Brown observed a large dark-gray plume rising at least 600 m above the summit, drifting ENE. The plume had not been evident 2 hours earlier and lasted until at least 1830. Larger-than-average steam plumes were later observed on 21 and 26 February and 3 March. [The following reports describing activity at Shishaldin during 15 February-3 March 1987 were collected by John Reeder. Observers were Marsha Brown (MB) and Theresa Dubber (TD), FAA, Cold Bay; and Andy Livingston (AL), Don Munson (DM), and Lee Goch (LG), Reeve Aleutian Airways.]
15 February (1600): 600-m-high plume to the ENE. (MB)
21 February (1314): 150-m-high plume to the NE. (JF, AL)
26 February (0925): 300-m-high plume to the SW. (TD)
2 March (1254): Minor steam to the SW. (JF, DM)
3 March (1240): 300-m-high plume extending 20 km ENE. (LG)
Geologic Background. The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.
Information Contacts: J. Reeder, ADGGS.