AVO reported that periods of elevated seismic tremor with no clear explosion signals were recorded at Pavlof during 14-18 September. Webcam images were mostly obscured by weather clouds. Minor ash deposits on the upper flanks and at least one minor ash emission was visible in a clear webcam view on 18 September. Small low-level ash emissions that dissipated quickly were noted by observers and visible in webcam images at 1500 on 19 September and at 0900 on 20 September. Ash deposits on the mid-flanks were identified in satellite data. Seismicity remained elevated during 2021 September; an explosion was recorded early on the 21 September. The vent in the crater continued to migrate N based on satellite data. The Volcano Alert Level and Aviation Color Code remained at Watch and Orange, respectively.

Geological Summary. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Source: US Geological Survey Alaska Volcano Observatory (AVO)