Unimak Island, Aleutian Islands, Alaska
54.75 N, 163.97 W
summit elevation 2857 m
Shishaldin volcano is located on Unimak Island, Aleutian Islands, Alaska. It is the highest volcano in the Aleutian Islands. The cone has been built in the past 10,000 years. The nearest permanent settlement is False Pass,
32 km to the east, with a population under 100 people.
Shishaldin has 55 vents on the NW flank of the volcano, which consist of basaltic cinder cones and associated lava flows. There are also maars and subglacial domes.
Shishaldin is one of the most active Aleutian arc volcanoes, with nearly 40 historic eruptions, which have been brief and explosive. During quiet periods, a steam plume is usually present at the summit.
An ash plume rising to 3 km altitude was visible at the volcano on 12th February.
2004 Seismic Unrest
In early May tremor was observed at the volcano for the first time since the 1999 eruption, and continued until June. In July the crater rim was warmer than the surrounding area.
The 1999 eruption was the largest known at the volcano in the 20th century. Starting in late June 1998, a swarm of low-frequency events was detected beneath the volcano. Observations of unusual activity at Shishaldin volcano began with a report by the US Coast Guard of steam and ash plumes “puffing” at 10-min intervals to about 30 m above the vent on 5th November 1998. On 17th April 1999 Strombolian eruptions were detected using Forward Looking Infrared Radiometer on board an aircraft. The main phase of the eruption was sub-Plinian and changing Strombolian eruptions after 80 minutes. The eruption ended on 24th April 1999.
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