AVO scientists observed the eruption of Okmok during a visit to Umnak Island on 2 and 3 August. They saw significant ashfall that had accumulated in the caldera and on the upper flanks, lahars and lahar deltas that formed in drainages from the SE to the NE flank, and continuous ash jets being emitted from three or more vents in the vicinity of Cone D in the NE sector of the caldera. Elevated seismicity was detected during 6-8 August, and declined on 9 August. According to observations of satellite imagery, steam plumes possibly containing ash rose to altitudes below 4.6 km (15,000 ft) a.s.l. during 9-10 August. On 11 August, steam plumes rose to altitudes of less than 6.1 km (20,000 ft) a.s.l. and drifted SE. Ash plumes that rose to around a hundred meters above the crater were reported by an observer in Nikolski (80 km SW). These plumes were not detected on satellite imagery due to cloud cover. On 12 August, a pilot reported an ash plume at an altitude of 4.6 km (15,000 ft) a.s.l. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.
Source: Alaska Volcano Observatory (AVO) – “Reports provided courtesy of the Smithsonian’s Global Volcanism Program and the US Geological Survey’s Volcano Hazards Program.”