Report on Shishaldin (United States) — 4 September-10 September 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 September-10 September 2019
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2019. Report on Shishaldin (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 September-10 September 2019. Smithsonian Institution and US Geological Survey.
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
Low-level lava fountaining and minor explosive activity within Shishaldin’s summit crater was last observed on 17 August and likely continued during 4-10 September; continuous tremor was recorded by the seismic network and moderately-elevated surface temperatures were visible in satellite images. Elevated surface temperatures on the upper SE flank suggested that minor amounts of lava spatter may have extended beyond the summit crater; clear webcam images showed no evidence of hot deposits on the upper flank the next day. 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.