AVO reported that by 28 October two stalled lava flows extended as far as 1.8 km down Shishaldin’s NW flank, lahars had traveled at least 4 km down the NW flank, and trace ash deposits on the N flank were identified in satellite images. Activity paused during 29-30 October but resumed on 31 October. Numerous small explosions were detected by the local seismic network during 31 October-1 November and incandescence was visible in webcam images. There was no evidence of active lava flows outside of the summit crater. During 1-2 November seismicity remained elevated characterized by periods of high-amplitude tremor. Small explosions were recorded in seismic and infrasound data. Elevated surface temperatures were detected in satellite images and incandescence was observed in webcam images overnight. A pilot observed a lava flow in the morning of 2 November. Sporadic incandescence recorded by the webcam overnight during 2-3 November suggested minor explosive activity and/or lava fountaining. On 3 November lava overflowed the summit crater and traveled at least 400 m down the NW flank and 300 m down the SE flank. By 4 November the flow on the NW flank had branched and lengthened to 1 km. Lahars were as long as 2 km on the N and S flanks. Spatter deposits from explosions or fountaining were visible on the summit cone. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

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)