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Based on satellite imagery and pilot reports received by the Federal Aviation Administration, Shishaldin Volcano on Unimak Island in the eastern Aleutian Islands erupted yesterday sometime around 6:30 pm AST (0330 UTC). Between 6:30 and 8:00 pm AST (0330 and 0500 UTC) Saturday, December 23, pilots reported an ash plume as high as 35,000 feet above sea level; prevailing winds at that altitude carried the plume primarily north and northwest. AVO analysis of a satellite image from 7:12 pm Saturday shows a possible small ash plume extending approximately 50 km northwest of Shishaldin. This morning, AVO received a report of a possible very light ashfall at approximately 1:30 am (1030 UTC) in Cold Bay, 56 mi (90 km) northeast of Shishaldin; this ash would have been carried from the volcano by westerly low altitude winds.
Shishaldin Volcano is located near the center of Unimak Island in the eastern Aleutian Islands. It is a spectacular symmetric cone with a summit elevation of 9373 ft (2875 m) above sea level. A small summit crater produces a steady, vigorous cloud of steam with occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, erupting at least 27 times since 1775. The most recent eruptive period occurred in 1986-1987; activity consisted of minor steam and ash emissions that continued for several months. The nearest village is False Pass, 20 mi (32 km) east-northeast of the volcano.
Based on the record of historic activity at Shishaldin, additional eruptions of ash may continue intermittently for days or weeks. The Alaska Volcano Observatory will continue to monitor the situation through pilot reports and analysis of satellite images.
NOTE: Due to the partial shutdown of the Federal Government, the Alaska Volcano Observatory is currently operating with reduced staff. However, we continue to seismically monitor Spurr, Redoubt, Iliamna, and Augustine volcanoes. A computerized alarm system is capable of
notifying AVO seismologists during non-business hours
should unusual seismic activity occur.