Report on Pavlof (United States) — 12 November-18 November 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 November-18 November 2014
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2014. Report on Pavlof (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 12 November-18 November 2014. Smithsonian Institution and US Geological Survey.
55.417°N, 161.894°W; summit elev. 2493 m
All times are local (unless otherwise noted)
On 12 November AVO raised the Aviation Color Code for Pavlov to Orange and the Volcano Alert Level to Watch, citing the beginning of a new phase of eruptive activity at about 1500. An observer in Cold Bay (52 km SW) reported that ash emissions rose slightly above the summit; minor ash emissions were also recorded by an FAA-operated webcam in Cold Bay beginning at 1650. Seismicity increased and remained elevated. Lava fountaining occurred from a vent just N of the summit and flows of rock debris and ash descended the N flank. A thermal anomaly appeared in satellite images at 1740. The eruption continued on 14 November. A narrow ash plume observed in satellite images drifted 200 km at an altitude of 4.8 km (16,000 ft) a.s.l.
The eruption intensified on 15 November prompting AVO to raise the Aviation Color Code to Red and the Volcano Alert Level to Warning. Ash plumes rose to an altitude of 7.6 km (25,000 ft) a.s.l. and drifted 200 km NW. The intensity of seismic tremor had increased significantly. Pilot reports through 1230 indicated that the ash plume had risen to an altitude of 9.1 km (30,000 ft) a.s.l. At about 1900 seismicity abruptly decreased and remained low. Satellite observations confirmed a significant decrease in ash emissions; discrete seismic events possibly indicated minor ash emissions that were not detected in satellite images. The Aviation Color Code was lowered to Orange and the Volcano Alert Level was lowered to Watch. Pilot reports on 16 November indicated no eruptive activity, and satellite images showed diminished temperatures in the summit crater. During 17-18 November seismic activity remained at low levels and elevated surface temperatures on the upper NW flank were observed, consistent with a flow of lava and/or hot debris.
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.