AVO reported that low-level unrest at Shishaldin continued during 13-20 February. Occasional small volcanic earthquakes were recorded daily by the seismic network. Robust steaming was observed in satellite and webcam images and reported by local pilots on 13 February, and minor steaming was visible in satellite and webcam images during 14-15 February. AVO noted that steam emissions were not uncommon at Shishaldin. At 1126 on 17 February AVO lowered the Volcano Alert Level to Advisory (the second lowest level on a four-level scale) and the Aviation Color Code to Yellow (the second lowest color on a four-color scale) noting that there were no signs of eruptive activity.

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)