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Redoubt a-rumbling 5 May 2009

Posted by admin in activity reports, Alaska, eruptions, Redoubt, United States.
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Seismicity at Redoubt is elevated, reports the Alaska Volcano Observatory, with ‘frequent rockfall signals, numerous small earthquakes, and low levels of volcanic tremor’. Even at reduced scale the pattern is clear on the RSO webicorder trace, as is the increasing intensity of the seismic activity:

RSO webicorder trace, 5 May 2009 (Alaska Volcano Observatory)

This type of seismicity is the language spoken by an actively-growing and unstable lava dome under increasing stress. The lava dome may well be headed for a collapse in the near future: it’s worth keeping an eye on the AVO Hut Webcam.

Further information from the AVO is that the volcano is producing a constant steam plume to about 4600 metres (15000 feet), with rockfalls on the dome putting a little diffuse ash into the emissions. Incandescence was visible after dark on the lower portions of the dome yesterday.

UPDATE. The latest Volcanic Activity Notice from the AVO (2009-05-05 06:59 AKDT) reads:

Current activity at Redoubt volcano suggests that a significant explosive event is likely, though not certain, in the coming days. This event could occur at any time with little or no warning. Since about May 2 shallow earthquake activity beneath the actively growing lava dome of Redoubt volcano has been slowly increasing. The growing lava dome is becoming increasingly unstable.

Should a significant explosion occur, the event will likely produce high altitude (>30,000 ft ASL) ash plumes, trace to minor ash fall in parts of south-central Alaska, lahars in the Drift River Valley, and pyroclastic flows in the immediate vicinity of the volcano.

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

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


1. SHIRAKAWA Akira - 6 May 2009

I have a question: what is exactly the cause of the dome stress (and related seismicity) ? Is magma having a hard time passing through its vents because the dome grew so much that internal partially molten rocks have become increasingly hard to displace (due to their weight,etc) ?

2. SHIRAKAWA Akira - 6 May 2009

Bright incandescence spotted (image digitally enhanced by me):

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