Report on Pavlof (United States) — October 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 10 (October 1987)
Managing Editor: Lindsay McClelland.
Pavlof (United States) Ash-rich explosions; blocks and spatter form flow
Please cite this report as:
Global Volcanism Program, 1987. Report on Pavlof (United States). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 12:10. Smithsonian Institution. https://dx.doi.org/10.5479/si.GVP.SEAN198710-312030.
55.417°N, 161.894°W; summit elev. 2493 m
All times are local (unless otherwise noted)
Activity increased 17 October when ash-rich explosions from the NW summit vent occurred every 30 seconds to several minutes. Ash plumes, reported through 9 November attained a maximum altitude of 4500-5800 m on 30 October (table 4). Plumes stretched E as much as 200 km and tephra fell at Canoe Bay, 45 km ENE, on 19 October. Blocks and spatter ejected to 30 m from the near-summit vent formed a short spatter flow. Night glow from the summit was visible on several evenings in mid-October. Incandescent rocks and spatter were reportedly continuing in early November. Ash deposits were last reported on 4 September (SEAN 12:09).[Skip text table]
Date Time Activity Reported [Observers] 16 Oct 1646 Thin gaseous plume on NOAA 9 satellite image. 17 Oct 1130 Loud explosions (continued through the night); incandescent flow feature on NE flank. [SH] 18 Oct 0800 Incandescent material flowed 800 m from vent. [SH] 0950 Ash to 3,200 m altitude, drifting 16 km NW; lava spatter to 30 m above vent. [DC] afternoon Rain, very black with ash near volcano. [SG] 1200-1600 Nearly continuous black ash emission to 3,050 m altitude, then clouds obscure volcano. [DO & TO] 1830 Volcano still very active. [SH] 19 Oct 1101 Plume on NOAA 10 satellite image drifting 200 km E. [SS & WG] 1138 Ash rising to 3,000 m altitude, drifting ESE. [JG & GW] morning Coarse black tephra fell at Canoe Bay. [SH] 1210 Ash to 4,250 m altitude, drifting E at least 90 km; ash pulses every 30 seconds and rocks (some incandescent) ejected to 180 m above the vent, landing about 800 m down the flank. [BC] 1300 Plume to over 3,350 m, extended at least 100 km E. [GM] afternoon Black, steaming, flow feature on NE flank, melted snow; incandescent material ejected. [BC] 1600 Nearly continuous ash emission formed a plume, drifted SE. [FAA] 1700 Mushroom-shaped plume rose to 1,220 m above summit. [FAA] 2000 Ejection of incandescent material. [JY & CT] evening Incandescent glow from summit. [HJ] 25 Oct Red glow from vent; ash to 900 m above vent, drifting NE; incandescent rocks ejected. [MB] 26 Oct 1828 Ash to 460 m above volcano. [CN, GL, H] 1907 Incandescent material ejected 30 m; ash to 300 m above volcano, drifting E. [JS] 1940 Ash to 4,600 m altitude, drifting SSE; incandescent material ejected. [DR] 27 Oct morn. Ash to 60 m above volcano, drifting NE. [SH] 29 Oct 1608 Ash to 30 m above volcano, drifting ESE. [CT] 1742 Plume to 4,600 m altitude, driftin ESE; ash fell from plume 1 km from vent. [CT] 30 Oct Ash plumes reached 4,500-5,800 m altitude. 01 Nov Volcano obscured. 05 Nov 0921 Dark ash rose about 250 m above summit, drifting NE. [JS] 06 Nov 1657 Dark ash was blown down SE flank, then drifted 20-25 km WNW. [JF]. 07 Nov 1238 Dark ash rose 150-300 m above summit. [TD] 1450 Ash plume rose to 3.6 km altitude; some ash drifted 20-25 km WNW. [JF] 1600 Dark ash to 3.6 km altitude, drifted 35 km NW. [JF] 09 Nov 0900 Ash plume rose to a maximum of 3.6 km altitude. [TD] 1000 Ash blown down S flank. [MB] 1210 No eruptive activity. [CG] 10-16 Nov Poor visibility. 16 Nov 0931 White steam rose to summit. [MB] 27 Nov 0934 Steam rose 60 m above the summit. [JY]
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; M.E. Yount, USGS Anchorage.