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AVO/USGS Volcanic Activity Notice

Volcano: Redoubt (CAVW #1103-03-)

Current Volcano Alert Level: WATCH
Previous Volcano Alert Level: WARNING

Current Aviation Color Code: ORANGE
Previous Aviation Color Code: RED

Issued: Wednesday, March 25, 2009, 1:35 PM AKDT (20090325/2135Z)
Source: Alaska Volcano Observatory
Notice Number: 2009/A15
Location: N 60 deg 29 min W 152 deg 44 min
Elevation: 10197 ft (3108 m)
Area: Cook Inlet-South Central Alaska

Volcanic Activity Summary: Seismic activity at Redoubt Volcano has declined over the last 36 hours, although there have been several brief increases in seismicity associated with minor low-level ash emissions. The last known ash emission was at 5:12 AKDT this morning. The plume from this event did not extend above about 15,000 feet. Based on the level of seismic activity, AVO is lowering the aviation color code to ORANGE and the volcanic alert level to WATCH.

Current seismicity at Redoubt is at times suggestive of intermittent lava extrusion at the volcano's summit. However, the existence of a new lava dome has not been confirmed because of poor weather. Growth of lava domes is common at volcanoes like Redoubt and was observed several times throughout the last eruption of 1989-1990. As dome size increases, so does the possibility of dome collapse along with a return to a more explosive eruptive style. Though a distinct rise in seismicity often precedes dome failure, domes can fail with little or no warning and may result in a sudden explosion and ash emission.

Based on observations from the Redoubt eruption of 1989-1990, episodes of dome growth followed by explosive dome destruction is a likely but by no means certain, near-term scenario. Cycles of dome growth and failure could occur for several months. In the event of an escalation in seismic activity or confirmation of a significant ash producing eruption, AVO would accordingly raise the color code and alert level to Red/Warning.

It is possible that dome collapse events will initiate pyroclastic flows over Drift glacier that will result in meltwater generation and downstream mudflows and floods. Some of these floods could reach Cook Inlet within hours.

Recent Observations:
[Volcanic cloud height] Ash and steam plumes in the immediate vicinity of the volcano are likely, but generally less than 20,000 feet above sea level.
[Mudflow] Mudflows and floods in the Drift River valley will be an ongoing hazard. Significant changes in water level and flow direction may occur rapidly.
[Other volcanic cloud information] Refer to the NWS Redoubt Coordination web page (http://pafc.arh.noaa.gov/volcano.php) for more information about ashfall advisories.

Remarks: Over a 21 hour period beginning on Sunday, at March 22, 2009, 22:38 AKDT (Monday, March 23, 2009, 06:38 UTC ), 6 separate explosions occurred at Redoubt Volcano, each producing ash plumes exceeding 30,000 feet (10,000 m) above sea level. The last of these explosions occurred on Monday, March 23, 2009, at 19:41 AKDT (Tuesday, March 24, 2009, 03:41 UTC), about 36 hours ago as of this writing.

During and following these events, large lahars (volcanic mud and debris flows) were observed traveling down the Drift River Valley, some reaching the mouth of the Valley at the Cook Inlet. Light ashfall (less than 5 mm) from the explosions has been reported at several locales spanning a region of about 100,000 square kilometers, mainly to the north of the volcano.

Contacts: Tom Murray, Scientist-in-Charge, USGS
tlmurray@usgs.gov (907) 786-7497

Steve McNutt, Coordinating Scientist, UAF
steve@giseis.alaska.edu (907) 474-7131

Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at
http://www.avo.alaska.edu

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.


(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:(20090325/2135Z)
(3) Volcano:Redoubt (CAVW# 1103-03-)
(4) Current Color Code:ORANGE
(5) Previous Color Code:red
(6) Source:Alaska Volcano Observatory
(7) Notice Number:2009/A15
(8) Volcano Location:N 60 deg 29 min W 152 deg 44 min
(9) Area:Cook Inlet-South Central Alaska
(10) Summit Elevation:10197 ft (3108 m)
(11) Volcanic Activity Summary:Seismic activity at Redoubt Volcano has declined over the last 36 hours, although there have been several brief increases in seismicity associated with minor low-level ash emissions. The last known ash emission was at 5:12 AKDT this morning. The plume from this event did not extend above about 15,000 feet. Based on the level of seismic activity, AVO is lowering the aviation color code to ORANGE and the volcanic alert level to WATCH.

Current seismicity at Redoubt is at times suggestive of intermittent lava extrusion at the volcano's summit. However, the existence of a new lava dome has not been confirmed because of poor weather. Growth of lava domes is common at volcanoes like Redoubt and was observed several times throughout the last eruption of 1989-1990. As dome size increases, so does the possibility of dome collapse along with a return to a more explosive eruptive style. Though a distinct rise in seismicity often precedes dome failure, domes can fail with little or no warning and may result in a sudden explosion and ash emission.

Based on observations from the Redoubt eruption of 1989-1990, episodes of dome growth followed by explosive dome destruction is a likely but by no means certain, near-term scenario. Cycles of dome growth and failure could occur for several months. In the event of an escalation in seismic activity or confirmation of a significant ash producing eruption, AVO would accordingly raise the color code and alert level to Red/Warning.

It is possible that dome collapse events will initiate pyroclastic flows over Drift glacier that will result in meltwater generation and downstream mudflows and floods. Some of these floods could reach Cook Inlet within hours.
(12) Volcanic cloud height:Ash and steam plumes in the immediate vicinity of the volcano are likely, but generally less than 20,000 feet above sea level.
(13) Other volcanic cloud information:Refer to the NWS Redoubt Coordination web page (http://pafc.arh.noaa.gov/volcano.php) for more information about ashfall advisories.
(14) Remarks:Over a 21 hour period beginning on Sunday, at March 22, 2009, 22:38 AKDT (Monday, March 23, 2009, 06:38 UTC ), 6 separate explosions occurred at Redoubt Volcano, each producing ash plumes exceeding 30,000 feet (10,000 m) above sea level. The last of these explosions occurred on Monday, March 23, 2009, at 19:41 AKDT (Tuesday, March 24, 2009, 03:41 UTC), about 36 hours ago as of this writing.

During and following these events, large lahars (volcanic mud and debris flows) were observed traveling down the Drift River Valley, some reaching the mouth of the Valley at the Cook Inlet. Light ashfall (less than 5 mm) from the explosions has been reported at several locales spanning a region of about 100,000 square kilometers, mainly to the north of the volcano.
(15) Contacts:Tom Murray, Scientist-in-Charge, USGS
tlmurray@usgs.gov (907) 786-7497

Steve McNutt, Coordinating Scientist, UAF
steve@giseis.alaska.edu (907) 474-7131
(16) Next Notice:A new VONA will be issued if conditions change significantly or alert levels are modified. While a VONA is in effect, regularly scheduled updates are posted at
http://www.avo.alaska.edu
VOLCANO ALERT LEVELS
NORMAL
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
ADVISORY
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
WATCH
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.
WARNING
Hazardous eruption is imminent, underway, or suspected.
AVIATION COLOR CODES
GREEN
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
YELLOW
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
ORANGE
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].
RED
Eruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].
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Page modified: May 16, 2014 09:40
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