Report on Shishaldin (United States) — 13 November-19 November 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 November-19 November 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, 13 November-19 November 2019. 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 the eruption at Shishaldin continued at variable levels during 13-19 November. Seismicity increased during 13-14 November, and elevated surface temperatures were visible in satellite and webcam data. Minor ash emissions were visible and likely resulting from spatter cone collapses. Lava and debris flows had not advanced since 8 November; lava flows had traveled as far as 1.2 km and a large branched network of debris flows extended at least 5.5 km NE. Strongly elevated surface temperatures and a steam plume drifting more than 100 km SE were visible on 15 November. An incandescent lava flow on the NE flank was recorded in webcam images. Activity during 17-18 November was characterized by low seismic tremor and weakly-to-moderately elevated surface temperatures, consistent with cooling lava flows. Seismicity and surface temperatures again increased during 18-19 November. 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.