Report on Pavlof (United States) — 22 August-28 August 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 August-28 August 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Pavlof (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 22 August-28 August 2007. Smithsonian Institution and US Geological Survey.
55.417°N, 161.894°W; summit elev. 2493 m
All times are local (unless otherwise noted)
Seismic activity at Pavlof remained elevated during 22-28 August. A strong thermal anomaly was present at the summit on satellite imagery on 22, 24, 25, and 28 August; clouds inhibited observations on other days. Based on pilot reports and calculations using satellite imagery, a steam-and-ash plume rose to an altitude between 3-5.5 km (10,000-18,000 ft) a.s.l. On 25 August, seismic events and explosions were more energetic and a signal suggesting a large lahar was noted. Plume altitudes from previous days and seismic interpretation indicated that an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. on 26 and 28 August. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange.
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.