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. http://dx.doi.org/10.5479/si.GVP.SEAN198710-312030.

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Pavlof

United States

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).

Table 4. Reports of activity at Pavlof, 16 October-27 November 1987, compiled by John Reeder and M.E. Yount from the following observers (initials in brackets): Steve Hakala (Canoe Bay); Dan Coy (Sand Point Air); Scotty Gibbens and John Sarvis (USFWS); Deedee and Tom O'Malia (Cold Bay); Marsha Brown, Theresa Dubber, Chuck Taylor, Jim Yakal (FAA Flight Service, Cold Bay); Steve Shivers (USGS, Anchorage); James Gibson, George Wooliver, Chuck Nickerson, Gary Lintner, Harding (Reeve Aleutian Airways); Guy Morgan, Bryan Carricaburu, Doug Ruberg (Peninsula Airways); Harold Johnson Sr. (Nelson Lagoon); Will Gould (NOAA/NESDIS); John Sarvis (USFWS); Sand Point Air pilot; James Fredenhagen (Reeve Aleutian Airways);Coast Guard pilot. Unattributed reports were compiled by M.E. Yount.

[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.