Report on Redoubt (United States) — 23 September-29 September 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 September-29 September 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Redoubt (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 23 September-29 September 2009. Smithsonian Institution and US Geological Survey.
60.485°N, 152.742°W; summit elev. 3108 m
All times are local (unless otherwise noted)
On 29 September, AVO reported that seismic activity from Redoubt, along with volcanic gas output, ground deformation, lava dome temperatures, and outward signs of lava dome instability, have been declining during the previous several months. The Volcanic Alert Level was lowered to Normal and the Aviation Color Code was lowered to Green.
Geologic Background. Redoubt is a glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. The volcano was constructed beginning about 890,000 years ago over Mesozoic granitic rocks of the Alaska-Aleutian Range batholith. Collapse of the summit 13,000-10,500 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3,500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.