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Pavlof reported activity





Event Name : Pavlof 1983/11

Start:November 14, 1983 Observed
Stop:December 18, 1983 Observed

Lava flow: BibCard
Tephra plume: BibCard BibCard BibCard
Eruption Type:Explosive
Duration: About one month BibCard
MaxVEI: 3 BibCard
ColHeight: 7500 m BibCard

Description: From Miller and McNutt (1986): "Eruptive activity was first observed from Sand Point (about 90 km E of the volcano) late on 14 November and pilots observed tephra columns the next afternoon. On 19 November a small vapor cloud rose approximately a hundred meters above the vent. Bad weather prevented observations until 26 November when Pavlof was visible until mid-afternoon from Cold Bay (about 60 km SW of the volcano). During the morning, a vapor plume containing a little ash rose to 4.5 km altitude. At intervals of approximately 30 minutes, puffs of dark ash were emitted. The intervals became shorter, and by 1500 ash emission was nearly continuous.

"Through October and early November, a Lamont-Doherty seismic monitoring station near the volcano recorded background levels of 0-40 (usually 0-30) small low-frequency events per day. A 30-minute burst of volcanic tremor began at 2000 on 4 November, and a 6-minute burst at 1757 on 9 November. Between 1430 on 11 November and 1100 on 13 November, 15 explosions were recorded. Several bursts of tremor of 1-2 minute duration occurred between 1700 and 1900, when continuous tremor started. Its amplitude gradually increased, and tremor began to saturate the seismograph at 1100 on 14 November. Tremor was strongest between midnight and 1200 on 15 November, and continued to saturate the seismograph until 2100 on 15 November when its amplitude began to decrease. Tremor remained continuous but at low amplitude between 1300 on 16 November and 1200 on 18 November. Intermittent low-amplitude tremor and numerous low-frequency (B-type) events recorded after 1200 on 18 November were continuing on 21 November.

"Airline pilots last reported eruption clouds from Pavlof at 1400 on 15 December and there have been no eyewitness reports of eruptive activity since then. Six explosions were recorded between 1600 and 2000 on 15 December by Lamont-Doherty's 5-station seismic net 4.5 - 10 km from the volcano. One of these stations, about 7.5 km from Pavlof, detected bursts of harmonic tremor 17 December, 1100 - 18 December, 0330; 18 December, 0530 - 0615 and 1040-1110; 20 December, 2200 - 2245; and 21 December, 2035 - 2048. Seismicity then decreased to the background level of several tens of events per day and remained at that level as of 26 January.

"Eruption plumes were observed on 3 images returned 15-17 December from the NOAA 8 polar orbiting satellite. The images returned at 2101 on the 15th and 1031 on the 17th showed well-defined, relatively dense plumes extending 225 km E and 400 km NE from Pavlof above the weather cloud layer. A diffuse plume was observed on the image returned at 2108 on 18 December.

"No volcanic plumes were observed on other images returned 15-21 December, but heavy weather clouds obscured the area."

McNutt (1985) calculates an estimated lava volume based on photoanalysis and pilot reports as 1.2 - 2.8 x10^6 cubic meters, and an additional 2-8 x10^6 cubic meters of ash. McNutt (1999) reports a single dense rock equivalent volume of 10.8 x10^6 cubic meters for this eruption.

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