Report on Shishaldin (United States) — April 1976
Natural Science Event Bulletin, vol. 1, no. 7 (April 1976)
Managing Editor: David Squires.
Shishaldin (United States) Ashfall on the flanks in late April
Please cite this report as:
Global Volcanism Program, 1976. Report on Shishaldin (United States) (Squires, D., ed.). Natural Science Event Bulletin, 1:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.NSEB197604-311360.
54.756°N, 163.97°W; summit elev. 2857 m
All times are local (unless otherwise noted)
2 April (0600): Steaming weakly, snow on cone uniformly white.
6 April (1500): Appeared to be radially covered with ash.
14 April (0800-1800): Steaming intermittently.
25 April (2200): Steaming weakly.
27 April (1110): A faint, veil-like ash cloud was observed over the volcano. Within ten minutes the cloud had disappeared, the ash having settled on the cone, which appeared to be irregularly covered with radial ash sprays. A dark black streak was observed on the NW flank, extending 5-10 km from the summit to about the 300 m level where the slope of the cone diminishes to about 20°. The volcano was observed until 1900 and no further activity was noted.
30 April (1100-1800): The cone appeared to be ash-covered. Strong S winds had blown black ash sprays, more noticeable than the day before, onto the N flank.
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.
Information Contacts: P. Sventek, USAF, Cold Bay.