Redoubt, Jan. 30, 2009.
Alaska Residents Prepare for Possible Eruption
Geologists say Alaska's Mount Redoubt could erupt within days, the first time in 20 years. Nearby residents are preparing for a possible ash storm.
The Alaska Volcano Observatory reported that during 24-25 January seismic activity at the Redoubt volcano increased markedly.
On 25 January, seismic tremors became sustained and amplitude increased notably prompting AVO to raise the Aviation Color Code to Orange and the Alert Level to Watch. During an overflight later that day, observers saw no evidence of an eruption. However, they also noted increased steaming through previously identified sources in the snow and ice cover, along with sulfur gas emissions.
An overflight on 26 January revealed elevated sulfur dioxide emissions from the summit and new outflows of muddy debris along the glacier that is downslope of the summit. On 26 and 27 January, seismicity fluctuated but remained above background levels.
Information Statement
Friday, January 30, 2009 7:16 AM AKST (1616 UTC)
Redoubt Volcano
60°29'7" N 152°44'38" W, Summit Elevation 10197 ft (3108 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
Unrest at Redoubt Volcano continues, though no eruption has yet occurred. Seismicity levels have risen within the last 8 hours. Redoubt remains at Aviation Color Code ORANGE and Volcano Alert Level WATCH.
Staff are currently monitoring the volcano 24 hours a day. We will issue further information as it becomes available.
Images associated with the Redoubt Hazard Report
Click to enlarge map.
Redoubt is a 3108-m-high 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 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 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 of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano. -- More
A dramatic, mushroom-shaped eruption column, lit by the rising sun, rises above Alaska's Redoubt volcano on April 21, 1990. Clouds of this shape, which are produced when the upper part of an eruption column attains neutral buoyancy and is spread out above the troposphere-stratosphere boundary, are common during powerful explosive eruptions. This column at Redoubt, however, did not originate from an eruption at the summit crater, but is an ash column that is rising buoyantly above a pyroclastic flow sweeping down the volcano's north flank. Photo by Joyce Warren, 1990 (courtesy of U.S. Geological Survey).
2 comments:
To the south, in Washington state's Puget Sound area, a magnitude 4.6 earthquake rattled residents early this morning. That probably is coincidental.
12:20 PM update: Seismicity levels have increased since yesterday evening and have also risen markedly over the last hour.
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