Report on Shishaldin (United States) — 15 November-21 November 2023
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 15 November-21 November 2023
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2023. Report on Shishaldin (United States) (Sennert, S, ed.). Weekly Volcanic Activity Report, 15 November-21 November 2023. Smithsonian Institution and US Geological Survey.
Shishaldin
United States
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
AVO reported that unrest continued at Shishaldin during 15-21 November. Seismicity remained elevated with ongoing seismic tremor and small, low-frequency earthquakes. Elevated surface temperatures were identified in satellite images during 15-16 and 19-20 November. Robust steam emissions were visible in satellite and webcam images during 17-20 November. Small explosions were observed in infrasound data during 18-21 November, consistent with weak Strombolian activity. Sulfur dioxide emissions were also identified in satellite images. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale).
Geological Summary. The symmetrical glacier-covered Shishaldin in the Aleutian Islands 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 edifice 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 covered 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.
Source: US Geological Survey Alaska Volcano Observatory (AVO)