Report on Shishaldin (United States) — 20 August-26 August 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 August-26 August 2014
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2014. Report on Shishaldin (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 20 August-26 August 2014. Smithsonian Institution and US Geological Survey.
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
AVO reported that during 20-26 August low-level eruptive activity continued at Shishaldin volcano. A steam and gas plume was visible in web camera and satellite images occasionally during the week. On 20 August satellite images showed a steam plume extending 60 km N of the volcano. On 23 August a pilot reported a steam-and-ash plume rose about 300 m (1,000 ft) above the summit and drifted NE. On 20-22 and 26 August elevated surface temperatures at the summit were detected in clear satellite views. Infrasound sensors located in Dillingham and on Akutan Island detected sound waves from the direction of Shishaldin that were consistent with low-level eruptive activity. No significant activity noted in seismic data. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
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.