Report on Augustine (United States) — 25 January-31 January 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 January-31 January 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Augustine (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 January-31 January 2006. Smithsonian Institution and US Geological Survey.
59.363°N, 153.43°W; summit elev. 1252 m
All times are local (unless otherwise noted)
After several days with no ash emissions and relatively low seismicity, Augustine erupted again on 27 January around 2001, with the most vigorous activity beginning around 2024. The eruption lasted about 9 minutes. AVO raised the Concern Color Code from Orange to Red, the highest level. According to the National Weather Service (NWS), the ash plume produced from the eruption reached ~12.2 km (40,000 ft) a.s.l. and drifted SE. An ashfall advisory was issued by the NWS. That same day, an eruption at 2337 lasted 1 minute and produced an ash plume below 3 km (10,000 ft) a.s.l. On 28 January at 0204 a 2-minute-long eruption began that sent ash to a height of 7.9 km (26,000 ft) a.s.l. and drifted SE. Later that day a 3-minute-long eruption began at 0742 that sent a NE-drifting ash plume to a height of 7.6 km (25,000 ft) a.s.l.
Augustine was in a state of continuous eruption from 1430 on 28 January through 31 January. The activity was characterized by steady ash emission and small pyroclastic flows. An observation flight on 29 January revealed diffuse drifting ash clouds at a height of ~7.6 km (25,000 ft) a.s.l. Also, ash-and-steam clouds rose from pyroclastic flows on the N flank of the volcano. Steam plumes rose from the NNE coastline, indicating that some of the pyroclastic flows had entered the sea. Satellite imagery on 31 January showed that plumes did not exceed 3.9 km (13,000 ft) a.s.l. and generally drifted N. According to a news article, Alaska Airlines cancelled flights to and from Anchorage on 30 and 31 January due to ash from Augustine in the airspace.
Geologic Background. Augustine volcano, rising above Kamishak Bay in the southern Cook Inlet about 290 km SW of Anchorage, is the most active volcano of the eastern Aleutian arc. It consists of a complex of overlapping summit lava domes surrounded by an apron of volcaniclastic debris that descends to the sea on all sides. Few lava flows are exposed; the flanks consist mainly of debris-avalanche and pyroclastic-flow deposits formed by repeated collapse and regrowth of the volcano's summit. The latest episode of edifice collapse occurred during Augustine's largest historical eruption in 1883; subsequent dome growth has restored the volcano to a height comparable to that prior to 1883. The oldest dated volcanic rocks on Augustine are more than 40,000 years old. At least 11 large debris avalanches have reached the sea during the past 1800-2000 years, and five major pumiceous tephras have been erupted during this interval. Historical eruptions have typically consisted of explosive activity with emplacement of pumiceous pyroclastic-flow deposits followed by lava dome extrusion with associated block-and-ash flows.