Report on Shishaldin (United States) — 25 December-31 December 2019
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
25 December-31 December 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, 25 December-31 December 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 during 25-31 December. Seismicity was elevated with weak explosions recorded by the network during 26-27 December. The seismicity decreased to relatively low levels on 27 December and remained low through 31 December. Strongly elevated surface temperatures were periodically identified in satellite images, indicating continuing lava effusion; images acquired during 25-26 December confirmed a 1.5-km-long lava flow on the NW flank and tephra deposits on the upper flanks. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
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.