Report on Shishaldin (United States) — 13 December-19 December 2017
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 13 December-19 December 2017
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2017. Report on Shishaldin (United States) (Sennert, S, ed.). Weekly Volcanic Activity Report, 13 December-19 December 2017. 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 seismic and infrasound data from Shishaldin continued to indicate elevated activity during 13-19 December. Robust steaming was recorded by a webcam during 13-14 December; ice and poor weather conditions prevented views during the rest of the period. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.
Geological Summary. The symmetrical glacier-covered Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. It is the westernmost of three large stratovolcanoes in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." Constructed atop an older glacially dissected edifice, 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. A steam plume often rises from the summit crater.