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Pavlof reported activity





Event Name : Pavlof 1981/9

Start:September 25, 1981 Observed
Stop:September 27, 1981 Observed

Lava flow: BibCard BibCard
Tephrafall: BibCard BibCard BibCard
Tephra plume: BibCard BibCard BibCard
"Fire", "Glowing", or incandescence: BibCard
Eruption Type:Explosive
MaxVEI: 3 BibCard
Duration: About 2 days BibCard
Eruption Product: basaltic andesite BibCard
ColHeight: 11300 m BibCard

Description: From McNutt and Shackleford (1983): "About two weeks before this eruption, a seismometer 7.5 km SE of summit began to register occasional harmonic tremor, plus an increase in the size of B-type events. However, just a few days before the commencement off visible activity, there was a decrease in the number and size of earthquakes recorded. On 24 Sept. there were no visible signs of unrest at Pavlof.

"On 25 September, explosive eruption started possibly at 10:00 local time (= GMT - 9 hr.). An eruption plume was observed at 10:30. This plume drifted to the E & SE. During the day eruptive activity waxed. At 15:45 the plume had risen to 9 km a.s.l. Another major eruptive pulse commenced shortly before 19:45; by 22:15 the new plume top had reached 10.5 km a.s.l. The strongest activity of the eruption took place on the night of 25-26 Sept. A boat in Pavlof Bay received 4 cm of ash that night; the ash was medium coarse sand size. Observations from Pavlof Bay that night noted vividly incandescent, violent Strombolian activity with black ash clouds.

"On 26 September, another significant eruption began at ca. 07:00, plume height of 7.5 km a.s.l. noted at 09:30. Again, local observers reported billowing clouds of black ash and a brightly incandescent eruption column. By 10:00, the plume had decreased in height to 6 - 7 km a.s.l., and an active lava flow - brightly glowing - was seen on NNW flank, coming from a vent some 100 m below the summit crater. Waning activity in the afternoon. During the night of 26-27 Sept. ash fell on Squaw Harbor (Unga Island, 90 km ESE of Pavlof) to, perhaps, a depth of 1 cm. This ash was fine sand size.

"On 27 September, fine ash still fell at Squaw Harbor in the early morning hours. Ground reports indicate eruptions of black ash and glowing tephra also. Strong, continuous harmonic tremor ended at 12:20. However, seismicity (B-type earthquakes) of small magnitude (0-1) remained high for several months afterwards.

"This eruption is fairly typical of eruptions observed over the last 10 years at Pavlof."

McNutt, 1987 reports this eruption produced approximately 1.0-1.7x10^7 cubic meters of ash, and 4.7-5.8x10^6 cubic meters of lava as a rootless lava flow of basaltic-andesite composition."

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