Report on Shishaldin (United States) — 9 March-15 March 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 March-15 March 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Shishaldin (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 9 March-15 March 2016. Smithsonian Institution and US Geological Survey.
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
On 10 March AVO reported that there had been a continual decrease in thermal activity at Shishaldin over the past several months; no anomalous activity had been observed in several clear satellite images since 13 January, when moderately elevated surface temperatures were detected. Airwaves generated by low-level explosive degassing had not been detected in infrasound data since 7 February. Low-amplitude seismic tremor was at background levels. The Aviation Color Code was lowered to Green and the Volcano Alert Level was lowered to Normal.
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.