Report on Pavlof (United States) — 26 June-2 July 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 26 June-2 July 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, 26 June-2 July 2013. Smithsonian Institution and US Geological Survey.
55.417°N, 161.894°W; summit elev. 2493 m
All times are local (unless otherwise noted)
According to news articles, ash plumes from Pavlof caused airlines to cancel one flight and reroute six more on 25 June. AVO reported that during 25-26 June seismicity declined, and consisted of intermittent bursts of tremor and occasional small explosions. Satellite images showed a plume containing small amounts of ash drifting NW, and strong thermal anomalies at the summit. Pilot reports on 26 June indicated that plumes rose to altitudes between 6.1-7.6 km (20,000 to 25,000 ft) a.s.l., and then to heights just above the summit later that day. Seismicity during 26 June-1 July continued at low levels and consisted primarily of periodically continuous, low-level tremor. Thermal anomalies at the summit detected in satellite images were strong during 26-29 June and weak during 30 June-1 July.
Activity further declined during 1-2 July; tremor and explosions were no longer detected in seismic and pressure sensor data. Satellite images did not detect elevated surface temperatures, volcanic gas, or ash emissions, and there were no visual observations from pilots or from webcam images of any eruptive activity since 26 June. AVO lowered the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory.
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.