Report on Pavlof (United States) — 28 May-3 June 2014
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 28 May-3 June 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, 28 May-3 June 2014. 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 31 May elevated surface temperatures were detected over Pavlof in satellite images, suggesting a low-level eruption with lava. Observers camping near the volcano confirmed lava and noted that flows were originating from a vent on the NE flank. A low-level steam plume was visible in satellite images and recorded by the FAA web-cam located in Cold Bay. Several pilots observed a gas-and-ash plume drifting N at altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. The Aviation Color Code was raised to Orange and the Volcano Alert Level was raised to Watch. Small explosion signals were detected by a distant infrasound sensor. Later that night weak incandescence from the summit was observed in the webcam. On 1 June clouds obscured web-cam views and ash plumes were not detected in satellite images. The seismic network detected weak activity.
Activity escalated on 2 June, prompting AVO to raise the Aviation Color Code to Red and the Volcano Alert Level to Warning. Seismic tremor increased at 1500 and pilots observed ash plumes at altitudes of 6.7 km (22,000 ft) a.s.l. Satellite images showed a plume drifting more than 80 km E. Seismicity started to decrease at 2300. The web cam recorded intense lava fountaining at the summit and incandescence from a spatter-fed lava flow on the N flank. On 3 June seismicity again increased and pilots observed ash-and-steam plumes at altitudes of 7.3 km (24,000 ft) a.s.l. that drifted SSW. Later that day AVO lowered the Aviation Color Code to Orange and the Volcano Alert Level to Watch due to a decrease and stabilization of volcanic tremor. Satellite and webcam images showed two distinct parts of the plume: gas and steam with minor amounts of ash rose high above the volcano and drifted S, while pyroclastic flows on the N flank produced diffuse ash that caused hazy air and variable concentrations of ash below 3 km (10,000 ft) a.s.l. Winds were likely to push ash at lower altitudes WSW.
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.