AVO raised the Volcano Alert Level for Shishaldin to Watch (the third level on a four-level scale) and the Aviation Color Code to Orange (the third color on a four-color scale) at 1246 on 11 February due to a slight increase in volcanic activity. Minor ash emissions were observed in a webcam image timestamped at 0925 on 11 February. The low-level ash cloud extended from the summit crater and draped over the N flank. AVO posited that since seismic signals typically associated with surficial mass flows were recorded at the same time as the ash emission event, a collapse event of previously deposited material on the upper area of the cone could have occurred. After the minor ash episode occurred, weather clouds obscured views of the summit and there was no evidence of ash in satellite images.

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)