Report on Pavlof (United States) — 15 May-21 May 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 15 May-21 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, 15 May-21 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 on 14 May a diffuse ash plume from Pavlof drifted about 160 km NE at an altitude of 4.6 km (15,000 ft) a.s.l. before dissipating. Pilot reports and photographs indicated that the lava flow extending down the NW flank was still active and generated debris-laden flow deposits, presumably from the interaction of hot lava with the snow and ice on the flank. Light ashfall was reported the evening of 14 May in a mining camp 80 km NE of the volcano. No other nearby communities had reported ash fall. During 14-15 May elevated seismicity persisted and steam-and-ash clouds observed with a web camera occasionally rose up to 6.1 km (20,000 ft) a.s.l. Residents in Cold Bay (37 km SW) observed incandescence from the summit during the night. On 15 May a pilot reported a dark ash cloud drifting ENE at an altitude of 6.1 km (20,000 ft) a.s.l.
On 16 May lava fountaining at the summit was observed and photographed, and a continuous ash, steam, and gas cloud extended downwind 50-100 km at an altitude of about 6.1 km (20,000 ft) a.s.l. Satellite images showed persistent elevated surface temperatures at the summit and on the NW flank, commensurate with the summit lava fountaining and resulting lava flow.
During 18-19 May a narrow plume of steam, ash, and gas, occasionally rising up to 6.7 km (22,000 ft) a.s.l., and drifting southeast, was visible in satellite images. Pilot reports indicated that lava fountaining and ash emission continued. Overnight, trace amounts of ash fell on the community of Sand Point. During the afternoon on 19 May pilots reported that ash plumes rose to altitudes of 4.6-6.7 km (15,000-22,000 ft) a.s.l. Trace amounts of ash fell in Nelson Lagoon, 78 km NNE, during 19-20 May. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange.
A news article stated that on 20 May a regional airline canceled about a dozen flights to several remote communities, including Sand Point. Another regional airline canceled a few flights, but mostly re-routed flights. On 21 May AVO reported that a low-level plume of steam, gas, and ash occasionally rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted NNE. Trace amounts of ash again fell in Nelson Lagoon.
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.