AVO reported that the thirteenth significant explosive event since 12 July was recorded at Shishaldin on 2 November. An increase in seismic and infrasound tremor amplitudes began at 1940 on 2 November, indicating a likely eruption. The Volcano Alert Level was raised to Watch (the third level on a four-level scale) and the Aviation Color Code was raised to Orange (the third color on a four-color scale), though ash was not identified in satellite data. At 2000 a sustained ash cloud drifting W was identified in satellite data at an altitude of 6.1 km (20,000 ft) a.s.l. By 0831 on 3 November ash emissions were no longer visible in satellite images and seismic and infrasound data indicated a decline in activity. During 4-7 November seismic activity remained elevated with ongoing tremor and small, low-frequency earthquakes. Minor emissions of steam and sulfur dioxide were visible in webcam and satellite images. Elevated surface temperatures were identified in satellite images on a few occasions. Infrasound signals consistent with small explosions were recorded during 5-7 November.

Geological Summary. The symmetrical glacier-covered Shishaldin in the Aleutian Islands 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 edifice 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 covered 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)