Printer friendly versionALASKA VOLCANO OBSERVATORY
Friday, January 27, 2006 2:50 PM AKST (2350 UTC)
59.3633°N 153.4333°W, Summit Elevation 4134 ft (1260 m)
Current Level of Concern Color Code: ORANGE
Nine explosions of Augustine Volcano occurred between January 11-17, each sending volcanic ash to more than 30,000 feet (9,000 m) above sea level. Currently the volcano is in a state of relative quiescence, although elevated rates of earthquake activity and gas emission continue as does swelling of the mountain's flanks. Based on all available data AVO believes that eruptive activity will resume over the next few days or weeks with either renewed explosive activity or dome building or a combination of both. AVO continues 24/7 monitoring of the volcano.
Observations and Background:
Between January 11 and 17 Augustine Volcano erupted nine times. Each of these explosive eruptions produced a significant ash plume and small mudflows and pyroclastic flows on the volcano's flanks. The most recent explosion occurred on January 17, 2006 at 7:58 AM (AST) and the volcano has since been relatively quiet. However, elevated rates of earthquake activity, gas emission and continued swelling of the volcanic cone continue. Observations from overflights and thermal images of the summit of the volcano indicate that little new material has been added to the summit since the eruption of January 17.
The 2006 eruption of Augustine can thus far be divided into three phases or episodes:
1) The early precursory period: This phase of the eruption began in late May 2005 and is characterized by a slow increase in the rate of earthquake activity and a slight swelling of the volcano's flanks. The average rate of earthquake occurrence was 1 to 2 per day in May and 3 to 4 per day in October. The total amount of uplift or swelling of the volcanic edifice was about 2 inches during this period.
2) The later precursory period: In early and mid December the volcano began to steam vigorously, and increased earthquake activity and gas emission were observed. In response to this activity, AVO deployed additional seismometers, GPS receivers, and time-lapse cameras on the flanks of the volcano, and established a web-based camera system.
3) On January 11 the volcano entered an explosive phase, and nine individual explosions were recorded between January 11 and 17. Most of the explosive activity was concentrated on January 13 and 14. A small lava dome was observed at the volcano's summit between January 14 and the last explosion on January 17. Each of the nine explosions produced ash plumes that rose in excess of 30,000 ft above sea level and generated pyroclastic flows and mudflows on the volcano's flanks.
Interpretation and Hazards:
Based on our current understanding of Augustine's past eruptions and our analysis of the current activity, AVO considers the following future scenarios as possible:
1) Eruption Ends: No further eruptive activity occurs and earthquake activity, ground deformation, gas output, and steaming slowly decrease over several weeks or months.
2) Initiation of Dome Building Eruption: A period of dome building like those of 1976 and 1986 will ensue. The explosive phase of both the 1976 and 1986 eruptions were followed by several months of intermittent dome building eruptions. These eruptions were characterized by the slow intermittent extrusion of lava on the summit of the volcano. Occasionally portions of the lava dome would become over-steepened and would slide down the flanks of the volcano producing small pyroclastic flows and small to moderate ash plumes. Depending upon prevailing winds, such ash plumes might be large enough to affect air traffic and communities in south-central Alaska.
3) Renewed Explosive Activity: Explosive activity such as that observed between January 11 and 17 could resume. Though the current eruption thus far is significantly smaller than those that occurred in 1986, 1976 and 1963-64, a return to explosive activity cannot be ruled out at this time. Historical reports of the 1963-64 eruption suggest that explosive activity continued for a much longer time period than that observed in either 1976 or 1986.
4) Larger Explosive Eruption: A significantly larger eruption could occur, perhaps similar to eruptions that are thought to have taken place prehistorically. Such an eruption might involve the production of larger ash plumes, significant modification of the island's summit, and large pyroclastic flows and mudflows on the island.
5) Flank Collapse: The intruding magma or other processes could destabilize a portion of the Augustine cone that could result in a large landslide. If such a landslide entered Cook Inlet, a localized tsunami could be generated. Such a landslide and tsunami occurred during the 1883 eruption of Augustine Volcano. It is also likely that a landslide of this type would be accompanied by an eruption.
Based on all available monitoring data AVO regards scenario two and three as most probable. At this time scenarios one, four and five are considered less likely. It is also possible that renewed eruptive activity may comprise both explosive activity and dome building, a combination of scenarios two and three.
AVO will continue to monitor the volcano closely. We plan to add additional instrumentation on the volcano to help us better understand the nature of the current eruption as conditions allow. New data and observations may lead us to change our assessment. Any changes would be announced in a subsequent Information Release.
Further information on Augustine Volcano and related hazards and response plans can be found at the following web sites:
Recent information on Augustine Volcano:
Hazards associated with volcanic ash fall:
Ash cloud trajectories and aviation warnings:
Tsunami issues related to Augustine:
ABBREVIATED COLOR CODE KEY
(contact AVO for complete description):
GREEN volcano is dormant; normal seismicity and fumarolic activity occurring
YELLOW volcano is restless; eruption may occur
ORANGE volcano is in eruption or eruption may occur at any time
RED significant eruption is occurring or explosive eruption expected at any time
VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478
Tom Murray, Scientist-in-Charge, USGS
email@example.com (907) 786-7497
John Eichelberger, Coordinating Scientist, UAF-GI
firstname.lastname@example.org (907) 474-5530 OR (907) 590-8247
The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.