Report on Shishaldin (United States) — 17 June-23 June 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
17 June-23 June 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, 17 June-23 June 2015. 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 seismicity at Shishaldin continued to be elevated over background levels 17-23 June, indicating that low-level eruptive activity confined to the summit crater likely continued. Elevated surface temperatures were periodically detected in satellite images, and minor steaming was recorded by the webcam. On 18 June pilot and satellite observations indicated a weak ash plume rising around 100 m above the summit crater, resulting in ash deposits on the upper flanks. Weak ash emissions were also visible with the webcam the next day. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geological Summary. 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.