Sunday, April 19, 2009

Joanna Tornes Update No. 8 Redoubt volcano.

The past week of activity at the Redoubt volcano was not dramatic. The aviation color code is ORANGE and the alert level WATCH.

A lava dome continues to grow in size within the summit crater. Based on photography and thermal images obtained Friday April 17, the current dome is estimated to be about 500 m (1640 ft) by 700 m (2297 ft) and at least 50 m (160 ft) thick.

Dome growth during the past week was accompanied by intermittent emissions of volcanic gases and minor amounts of ash.

The Alaska Volcano Observatory continues to monitor the situation on a 24/7 schedule.

The last lava explosion during the current eruption occurred on the morning of April 4 (05:55 AKDT).

Since then, seismicity has remained elevated.

Dome growth and occasional rock falls continue.

The vapor and gas cloud rising above the volcano has remained mostly below 15,000 feet above sea level.

Satellite images show thermal anomalies at the summit as well as the low -level plumes and sulfur dioxide clouds drifting away from the volcano.

Pilots have noted occasional sulfur smell down wind.

On Thursday, April 16, AVO field crews repaired a summit seismic station that was destroyed in the March 23 explosion.

They AVO field crew installed a new camera at the AVO hut that has remote zooming capabilities.

AVO geologists sampled material from the last explosive event.

They also investigated the site of a smaller ash and water vapor plume seen intermittently during the last two weeks. This secondary site is down slope from the Rdoubt summit.

Based on the observations of these geologists, it appears that the secondary plume resulted from hot pyroclastic debris falling into a crevasse in glacial ice.

A gas measurement flight was conducted by the AVO on Thursday April 16.

The AVO expects the current Redoubt eruption to continue for weeks and months.

The AVO also predicts that a cycle of relatively quiet periods of lava dome growth will be followed by explosive episodes of dome destruction.

Future explosions pose an ongoing threat of lahars in the Drift River Valley, trace to minor ash fall throughout south-central Alaska, and ash-related impacts to aviation.

This report is based on AVO materials.


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