Report on Augustine (United States) — 22 March-28 March 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 22 March-28 March 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, 22 March-28 March 2006. Smithsonian Institution and US Geological Survey.
59.363°N, 153.43°W; summit elev. 1252 m
All times are local (unless otherwise noted)
Low-level eruptive activity continued at Augustine during 17-24 March. All available information indicated that the lava dome continued to grow, but the growth rate slowed in comparison to the previous week. Signals from small block-and-ash flows, rock avalanches, rockfalls, and lava flows continued to be recorded by the seismic network though at a decreased rate. Web-camera views showed continued steaming at the summit and occasional small rockfalls. Thermal anomalies continued to be visible on satellite imagery. Low-light camera images showed a decrease in thermal features in the volcano's summit area and on the upper NE flank compared to the previous week. Visual observations during 15-22 March revealed no large-scale dome growth. Decreased SO2 gas emission was measured on 22 March in comparison to 10 and 16 March. However, the level of SO2 emission was comparable to levels in late February and early March, and remained well above background. AVO reported that dome-building eruptive activity will likely continue, perhaps intermittently, over the next several weeks or months. Augustine remained at Concern Color Code Orange.
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.