Friday, January 30, 2009

Alaska's Mount Redoubt Volcano Could Still Erupt Anytime, According To Alaska Volcano Observatory

Click HERE to view all previous posts on the 2009 Mt. Redoubt episode in inverse chronological order, with the most recent post appearing first.

Update March 22nd: Mount Redoubt erupts to 50,000 feet, ashfall expected in Susitna Valley with slight chance in Anchorage. Details HERE.

The Alaska Volcano Observatory still believes Mount Redoubt could erupt on short notice, and still has designated it ORANGE, according to the latest statements posted on their website. I've also posted a dedicated category on my sidebar with pertinent links, which will remain until the color state is downgraded back to YELLOW.

As a matter of fact, according to the latest report, posted on
2009-01-30 00:55:33 Alaska time, seismicity at Redoubt has changed character again. Since early Thursday evening, there have been several periods of volcanic tremor increasing in amplitude through time. This activity is more energetic than that of the previous several days, however it is still less vigorous than that observed last weekend.

Additional information links:

-- NWS Redoubt page: Includes latest forecast ash trajectory.
-- Air Resources Laboratory Multiple Ash Forecast Trajectories
-- Experimental Puff Ash Cloud Prediction Model (animated)
-- Mt Redoubt Webcam #1 (Hut)
-- Mt Redoubt Webcam #2 (CI)

Alaska volcanoes tend to erupt explosively, because lava domes form, bottling up the gas until it reaches explosive force. They can shoot ash as high as eight miles up (nearly 50,000 feet). So the 40,000 ft trajectories indicated on the various models are the most representative trajectories to watch. As discussed in my previous post, the forecast trajectories simply represent where the ash will be carried in the atmosphere and may not always result in ashfall on the surface beneath until they're carried sufficiently downrange.

According to the Anchorage Daily News, Mt. Redoubt is playing a similar pre-eruption scenario to 1989. Two decades earlier, when Redoubt last erupted on December 14th, 1989, its labor pains were fast and furious, recalls John Power, a veteran geophysicist at the Alaska Volcano Observatory in Anchorage.

One day prior to the eruption, the five seismographs positioned around Redoubt's flanks were still quiet -- then, in a matter of minutes, they were sounding the alarm. Which came not a moment too soon. Redoubt quickly erupted. "It went basically from what we would describe as 'background activity' to full eruption over a 23-hour period ... which is very rapid for a volcano," Power said.

With that as the only detailed account of a Redoubt eruption in the scientific record, observatory geologists on the night shift on Sunday January 25th reacted swiftly when -- at 1 A.M. -- the volcano's seismographs suddenly began to red-line all over again. After a quick conference, AVO officials upgraded the aviation color code for Redoubt from yellow to orange and sent out an all-points advisory noting that an eruption was possibly imminent, perhaps within hours to days.

Since then, earthquakes and seismic readings at Redoubt have waxed and waned -- but generally remained at a level not seen since 1989, Power said Thursday. "This particular sequence seems to be playing out a little bit slower. It hasn't resulted in an eruption yet, but we are still seeing these very elevated levels of earthquake activity.... We still feel the most likely outcome is going to be an eruption".

The Associated Press captured KTVA Channel 11's report and posted it to YouTube:

And the last time Redoubt erupted, it remained active over a four-month period. You can read a detailed 47-page report about that eruption HERE. One of the more interesting media stories was published by the Charleston (WV) Daily Mail about a former Soldotna resident who was in Soldotna during the 1989 eruption. He said there was 8-10 inches of ash on the streets when it was over. KTUU's latest report also includes video of the 1989 eruption.

Visit the USGS Volcano website to find out what you should do in the event of an ashfall in your area.

1 comment:

  1. great post,very informative.i have some friends in thoughts are with all of you.