Thursday, May 13, 2010

Redoubt Volcano

Redoubt Volcano is an active stratovolcano which is situated in the largely volcanic Aleutian Range of the State of Alaska, in Lake Clark National Park. It is just west of Cook Inlet, in the Kenai Peninsula Borough about 110 mi southwest of Anchorage. Redoubt Volcano, or Mount Redoubt, is 9,000 feet high, towering above the surrounding valleys to the north, south, and southeast. It is also the third highest within the range, with nearby Mount Torbert, at 11,413 feet, being the highest and Mount Spurr at 11,070 feet being the second highest.

Redoubt has been the most active Holocene volcano in the upper Cook Inlet. The volcano began to build up about 890,000 years ago over Mesozoic granitic rocks of the Alaska-Aleutian Range batholith. Collapse of the summit of Redoubt 10,500-13,000 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 3500 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 of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.