Report on Shishaldin (United States) — 22 October-28 October 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 October-28 October 2014
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2014. Report on Shishaldin (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 October-28 October 2014. 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 partly cloudy satellite images and mostly cloudy webcam views showed nothing unusual at Shishaldin during 21-24 October. Seismicity increased on 25 October, and was followed by a tremor event and elevated surface temperatures detected at the summit in satellite images. Tephra deposits at the summit were noted in clear webcam images on 26 October, indicating that the event was energetic enough to eject material onto the flank from a depth of several hundred meters within the summit crater. 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.