Report on Shishaldin (United States) — 12 May-18 May 2004
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
12 May-18 May 2004
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2004. Report on Shishaldin (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 12 May-18 May 2004. Smithsonian Institution and US Geological Survey.
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
During 7-14 May seismic unrest continued at Shishaldin, characterized by sequences of volcanic earthquakes, small explosions, and seismic tremor. A weak thermal anomaly observed at Shishaldin's summit on 11 May was similar to those detected occasionally since January 2004. Shishaldin remained at Concern Color Code Yellow.
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.
Source: US Geological Survey Alaska Volcano Observatory (AVO)