OREGON STATE UNIVERSITY
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| Last Update: June 4, 1997. |
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June 3, 1997
An increase in earthquake activity was noted at Pavlof on June 1, 1997. Two days later the National Weather Service in Cold Bay reported a steam plume rising 3,000 feet (1,000 m) above Pavlof's summit. The Alaska Volcano Observatory monitors the volcano and expects renewed activity. Pavlof last erupted from September to December, 1996. This update is based on information posted by the U.S. Geological Survey's Alaska Volcano Observatory on Volcan ListServ on June 3, 1997.
Volcanologists at the Alaska Volcano Observatory reported a small eruption at Pavlof volcano on the Alaska Peninsula. The eruption began on September 16, 1996. The volcano observatory was alerted to the eruption by residents near the volcano who saw an unusual plume. Satellite images showed a hot spot near the cone. Earthquakes indicated a low level eruption. The volcano is monitored by six seismic stations operated by the volcano observatory. Bad weather hampered visual observations.
The seismic stations continued to record earthquakes the following week that indicated a low level of activity.
On Tuesday the 24th, earthquake activity began to increase, indicating stronger eruptions relative to the previous week. Although visual and satellite observations were difficult due to bad weather volcanologists correlated the increased earthquake activity with eruptions that sent plumes as high as 4,000 feet (1,200 m) above the summit. Satellite images showed thin ash plumes extending as far as 30 miles (45 km) from the volcano.
On the 27th, staff of the volcano observatory made airborne observations and reported low level fountaining and occasional small explosions of incandescent material in the summit crater. Incandescent spatter accumulated on the summit and was moving down a deep gully on the northwest flank of the volcano. The observers also reported small steam plumes with sporadic ash content.
As of September 28, a Strombolian eruption continues at Pavlof.
An update released by the Alaska Volcano Observatory on October 2 described the continuing Strombolian eruption at Pavlof Volcano. Staff from the volcano observatory reported incandescent spatter fountaining from two vents in the crater. The spatter continues to feed a lava flow that is moving to the northwest. The Alaska Volcano Observatory believes eruptive activity at Pavlof could continue at this level for weeks or months.
Late on the night of Friday, October 18, earthquake activity at Pavlof indicated a considerable increase in eruption strength. Scientists of the Alaska Volcano Observatory estimated that an eruption plume more than 25,000 feet above sea level was possible and could potentially present a hazard to aircraft. Poor weather conditions at the volcano hampered direct observations. By mid-morning the following day earthquake activity had returned to the previous level. The eruption continues with lava fountaining in the crater.
On Tuesday, October 22, the Alaska Volcano Observatory reported a short-lived burst in earthquake activity at Pavlof. Lava fountaining continues at the crater. Pilots reported an ash plume that reached an altitude of 25,000 feet (7,500 m). Satellite observations showed the ash drifting to the northeast.
The November 1, 1996 update of the Alaska Volcano Observatory reported that the eruption continues. Eruption plumes were seen on satellite images and reported by pilots. Two vents at the summit of the volcano feed flows that are moving down the west and northwest flanks of Pavlof. Lava fountaining continues. Staff of the volcano observatory believe the eruption will continue for weeks or months.
On the morning of November 4, 1996, eruptive activity at Pavlof increased significantly. Ash plumes reached altitudes of 25,000 feet (7500 m) and extended downwind at least 100 miles (160 km). Direct observations of the volcano were hampered by poor weather.
An increase in the seismic activity within the past 24 hours seems to indicate that new eruptive activity may be on the way. The increase came after a ten day period in which there was little or no activity. It is possible this current eruptive event will cause ash plumes that could reach 20,000 feet above sea level.
Seismic activity now indicates very strong eruptive activity. This seismic activity is at the highest level of the current eruptive event. Early in the morning of the 27th, a summit hot spot is seen along with an active lava flow and an ash plume which stretches for several tens of miles. Later in the afternoon of the 27th, periodic bursts of ash and steam rise a few hundred feet above the summit of the volcano.
According to sources at the AVO seismic activity is still high. Ash plumes rise 12,000 to 16,000 feet above sea level. Early in the day, lava fountaining and an active lava flow are observed. Activity subsides later in the day and into the night.
For further information visit the Alaska Volcano Observatory home page. Additional background information on Pavlof Volcano including history of volcanic activity, location, and geologic maps is also available on the Alaska Volcano Observatory home page and in VolcanoWorld.
Sources of Information:
Alaska Volcanoes Updates, Alaska Volcano Observatory, October 19, 1996
Alaska Volcano Observatory, Alaska volcanoes weekly update, VOLCANO ListServ, November 1, 1996
Alaska Volcano Observatory, Alaska Volcanoes Update, VOLCANO ListServ, November 4, 1996
Alaska Volcano Observatory updates in Volcano ListServ.
Additional Sources of Information
McNutt, S.R., and Beavan, R.J., 1981, Volcanic earthquakes at Pavlof Volcano correlated with the solid earth tide, Nature, v. 294, no. 5842, pp. 515-618.
McNutt, S. R., 1986, Observations and analysis of B-type earthquakes, explosions, and volcanic tremor at Pavlof Volcano, Alaska, Bull. Seis. Soc. Amer., v. 76, pp. 153-175.
McNutt, S.R., and Jacob, K.H., 1986, Determination of large-scale velocity structure of the crust and upper mantle in the vicinity of Pavlof Volcano, Alaska, J. Geophys. Res., v. 91, pp. 5013-5022.
McNutt, S.R., 1987, Eruption characteristics and cycles at Pavlof Volcano, Alaska, and their relation to regional earthquake activity, J. Volcanol. Geoth. Res., v. 31, pp. 239-267.
McNutt, S.R., 1987, Volcanic Tremor at Pavlof Volcano, Alaska, October 1973 - April 1986. PAGEOPH, v. 125, pp. 1051-1077.
McNutt, S.R., and Beavan, R.J., 1987, Eruptions of Pavlof Volcano and their possible modulation by ocean load and tectonic stresses, J. Geophys. Res., v. 92, pp. 11,509-11,523.
McNutt, S.R., 1989, Some seismic precursors to eruptions at Pavlof Volcano, Alaska, October 1973 - April 1986. in: Latter, J.H. (ed.), IAVCEI Proceedings in Volcanology, v. 1, pp. 463-485.
McNutt, S.R., Miller, T., and Taber, J.J., 1991, Pavlof Volcano: seismological and geological evidence of increased explosivity during the 1986 eruptions. Bull. of Volcanol., v. 53, pp. 86-98.