Report on Pavlof (United States) — 22 May-28 May 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 May-28 May 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on Pavlof (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 May-28 May 2013. Smithsonian Institution and US Geological Survey.
55.417°N, 161.894°W; summit elev. 2493 m
All times are local (unless otherwise noted)
AVO reported that seismic tremor at Pavlof markedly declined around 1100 on 21 May, and was followed through 23 May by the detection of small discrete events, likely indicative of small explosions, by pressure sensors. Although cloud cover prevented satellite observations, elevated surface temperatures at the vent were detected. On 22 May both a pilot report and photographs indicated weak steam-and-gas emissions containing little to no ash.
The eruption continued but at a lower level during 24-26 May. Neither evidence of elevated surface temperatures nor a plume were observed in partly clear satellite images during 24-25 and 27 May. Clouds obscured views on 26 May. The Volcanic Alert Level was lowered to Advisory and the Aviation Color Code was lowered to Yellow on 28 May.
Geologic Background. 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.