Report on Pavlof (United States) — November 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 11 (November 1986)
Managing Editor: Lindsay McClelland.
Pavlof (United States) Eruption continues; lava flow reaches ocean
Please cite this report as:
Global Volcanism Program, 1986. Report on Pavlof (United States). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 11:11. Smithsonian Institution. https://dx.doi.org/10.5479/si.GVP.SEAN198611-312030.
55.417°N, 161.894°W; summit elev. 2493 m
All times are local (unless otherwise noted)
The eruption continued into December with steam plumes from the N-summit vent and ash emissions from a SE flank vent 200-300 m below the summit (table 2). Steam and ash emissions were continuing at 1840 on 10 December when pilots saw an orange-red glow in a cloud above the summit. They did not observe any material moving through the clouds. The next day at 1324, airplane pilots reported that 3-4 lava flows had moved down the SSE flank and that one had reached the Pacific Ocean at Pavlof Bay, 10 km from the summit [but see 11:12]; a 300-m-high steam column rose where the flow entered the water.[Skip text table]
Date Time Activity Reported [Observers] 17 Nov 1006- Constant steaming from N vent; black ash pulsed (every 5- 1600 8 minutes at 1200) from SE vent, feeding a plume to 3,600-4,200 m altitude that drifted 25-30 km S; ash covered the entire SE flank. [CB, EL, JC, MA] 18 Nov 1200- Steam emission from N vent; ash emission from SE vent, 1652 drifting SW. [JC, JF, CB] 19 Nov 1030 Ash plumes to 3,000-3,300 m altitude emitted at 5-minute intervals from SE vent. [EL] 1600 No eruption apparent despite clear visibility. [RA] 21 Nov 1522 Small amounts of ash formed 1.5-km-long plume. [PA] 23 Nov 1545 Plume rose to 3,000 m altitude; drifted NE. [Cessna] 26 Nov 1130 Dark gray ash pume rose 90-150 m above summit from SE vent and drifted 8 km SE. [LG & DM] 02 Dec 1045 Ash column from SE vent rose to 3,000 m, drifted E. [MB] 1359 60-m-high brown ash cloud from SE vent. [JC & MB] 10 Dec 1840 Pilots at 3,600 m altitude observed an orange-red glow in a thin cloud horizon at 2,500 m altitude (just above the summit). [LG & DM] 11 Dec 1324 SE-vent ash plume reached 4,500-5,400 m altitude and drifted WSW for 32 km; three to four narrow lava flows had moved down the SSE flank. [HB & DM] 16 Dec 1140 60-m-high steam plume from the SE vent; no other activity was observed. [LG]
Seismicity in early November reached more than 150 events/day, all apparently explosion shocks. Individual events had similar durations but variable amplitudes. Only a few hours of tremor were recorded.
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.
Information Contacts: J. Reeder, ADGGS; J. Taber, LDGO.