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Redoubt update, 24 March 2009 24 March 2009

Posted by admin in activity reports, Alaska, eruptions, Redoubt, United States.
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AVO Redoubt Hut webcam, 23 March 2009 19-55-58 (AVO/USGS)
Redoubt AVO Hut webcam image, 23 March 2009, 19:55:58 local time (image courtesy AVO/USGS). [source]

There have been six large explosions at Redoubt during the current eruptive phase. In its various updates, the AVO gives the following approximate starting times (local time) for these events:

  1. 22 March, 22:38
  2. 22 March, 23:02
  3. 23 March, 00:14
  4. 23 March, 01:39
  5. 23 March, 04:31
  6. 23 March, 19:41

The sixth event was captured by the AVO Hut webcam. In an update issued at 19:59 yesterday the AVO estimated from radar an eruption cloud height of ‘at least 60,000 feet above sea level’ (approximately 18200 metres). Ash emission was reported to have ended by 20:56. Pyroclastic flows were observed via the webcam, descending the north face of the volcano – one can be seen in the image reproduced at the top of this post. The picture also clearly shows the mudflows produced by the melting of the Drift Glacier and other ice and snow on the volcano, and the extensive ashfall staining the white landscape with murky grey.

In the caption to one of the images available on the AVO website (a composite of satellite images) there is a reference to seven eruption events, but with the caveat that the total of seven is ‘one preliminary interpretation and may be subject to change on further review’. So it seems best to stick with the total of six until we hear differently.

The latest from Redoubt (AVO update, 2009-03-24 06:56:32) is that seismicity is now at low levels, and has remained little changed for some hours. The subdued seismicity is clearly shown by traces from REF, RDN and NCT seismic stations, which also show clearly how rapid was the onset of explosion 5 at 19:41 yesterday, and how markedly things quietened down after it. That ‘quietened down’ is only relative: there is still a lot of low-level background tremor and occasional small quakes visible on the traces. Redoubt’s previous history would suggest that more explosions and ash emissions are to come. ‘Further explosive activity could occur with little or no warning, and could occur intermittently for weeks or months’, says the AVO.

The RSO station was knocked out yesterday, and its trace is now a rather sad and meaningless squiggle.

UPDATE: Since the above was written there’s been another AVO update (2009-03-24 09:04:19) saying that seismicity remains unchanged but noting that ‘Small discrete earthquakes are occurring’. See Akira Shirakawa’s comment below regarding a slight increase in the frequency of these quakes over the past two hours or so.

ANOTHER UPDATE: A new status report has been issued by the AVO (12:46 local time, 20:46 GMT), reporting low seismicity, no indications of ash emission, and a steam plume rising to 20000 feet (6000 metres) and extending 40 miles (64 kilometres) to the NW. Seismicity is definitely elevated and choppy: the RSAM plots (particularly the 10 minute average chart) show this clearly.

For all our Redoubt coverage: Redoubt « The Volcanism Blog.

Information
Global Volcanism Program: Redoubt – summary information for Redoubt (1103-03-)
Alaska Volcano Observatory – Redoubt – AVO information and updates for Redoubt
Alaska Volcano Observatory – main page for the AVO

The Volcanism Blog

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Comments

1. SHIRAKAWA Akira - 24 March 2009

Actually, seismic activity has been slightly increasing during the last hour and half, in the form of increased frequency of small discrete earthquakes (I have counted 25-30 events per 10 minutes). This is a waveform and spectrum view of REF seismic station between 15:30 and 16:30 UTC:


(Right click save if you want to use this later, I’m not sure if the link will last for long)

AVO also mention this in the latest observation update of 2009-03-24, 09:04:19.

2. Brian Owens - 24 March 2009

There was an article in the Seattle Times that looks like it was just posted a few minutes ago, and it had the following information:

“New tremors at Alaska’s Mount Redoubt are prompting speculation that the volcano could be in a phase that will lead to more instability. The 10,200-foot volcano erupted six times Sunday and Monday, spewing clouds of gritty ash high into the sky.

A volcanologist at the Alaska Volcano Observatory said Tuesday that Redoubt was exhibiting activity that could indicate it is creating a formation called a lava dome.

Volcanologist Peter Cervelli said such a formation can collapse, creating more ash plumes and mudflows.”

http://seattletimes.nwsource.com/html/nationworld/2008907154_apalaskavolcano.html

3. volcanism - 24 March 2009

Lava dome formation (with its attendant instability and collapses) and a period of further eruptions and ash emission would be consistent with Redoubt’s history. What the Seattle Times report says reflects the AVO’s forecasts at this point.

4. The Geology News Blog · Mount Redoubt Eruption Photos - 24 March 2009

[…] Alaska Volcano Observatory has posted some photos of the ongoing eruption at Mount Redoubt. The weather has been less than ideal, so photos have been slow to come out of the […]

5. Bits and pieces, part n | Bad Astronomy | Discover Magazine - 25 March 2009

[…] noted, I wonder if amateur exorcist and Louisiana doomer Bobby Jindal is scratching his head over volcano monitoring […]

6. theroachman - 25 March 2009

AVO complete another flight and will post photos later.

7. Top Posts « WordPress.com - 27 March 2009

[…] Redoubt update, 24 March 2009 Redoubt AVO Hut webcam image, 23 March 2009, 19:55:58 local time (image courtesy AVO/USGS). [source] There have been […] […]


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