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Report on Shishaldin (United States) — 29 July-4 August 2015

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 July-4 August 2015
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2015. Report on Shishaldin (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 July-4 August 2015. Smithsonian Institution and US Geological Survey.

Volcano Profile |  Weekly Report (29 July-4 August 2015)


Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


AVO reported that seismicity at Shishaldin continued to be elevated over background levels 28 July-4 August indicating that low-level eruptive activity confined to the summit crater continued. Cloud cover sometimes prevented satellite and webcam observations; elevated surface temperatures were sometimes detected in satellite images. Satellite images detected a 24-km-long steam plume drifting SE on 28 July and vigorous steaming and plumes drifting SW on 31 July. A steam plume was recorded by the webcam on 2 August. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geologic Background. The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 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 steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 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.

Source: US Geological Survey Alaska Volcano Observatory (AVO)