AVO reported that seismicity at Shishaldin was characterized as near-continuous tremor during 18-20 March and continuous tremor during 21-24 March. Steam-and-gas plumes rising from the summit crater were recorded daily by the webcam and sometimes identified in satellite images. Elevated surface temperatures, consistent with lava in the summit crater, were also identified in satellite images. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

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)