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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: Friday, April 3, 2009, 11:44 AM AKDT (20090403/1944Z)
Source: Alaska Volcano Observatory
Notice Number: 2009/A31
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: The eruption of Redoubt Volcano continues. Over the past several days, the intensity of ash-production has decreased. Current observations indicate a lava dome is growing in the summit crater. Therefore, we are lowering the alert level and aviation color code.

The 2009 eruption is now characterized by continuous emission of steam, volcanic gas, and variable amounts of ash. These processes are occurring as effusion of lava in the summit crater produces a lava dome. While at this level of activity, trace amounts of ash and a perceptible volcanic haze layer may be intermittently present throughout south-central Alaska.

A growing lava dome is inherently unstable; a sudden dome collapse or explosion can occur with no warning and produce a more voluminous ash cloud that rises to elevations above 25,000 feet. If such an event is detected, AVO would issue appropriate warnings.

Recent Observations:
[Volcanic cloud height] Over the last few days, a diffuse cloud of volcanic gas, ash, and steam is rising to variable altitudes over the volcano, but mostly less than 15,000 feet above sea level. At times of more vigorous ash production, the cloud has risen as high as 25,000 feet.
[Ash fall] Trace amounts of ash fall (less than 0.8 mm or less than 1/32 inch) have been reported at Kenai and at Valdez. The area in the immediate vicinity of the volcano is blanketed by a thin layer of ash visible in the AVO web cameras.
[Lava flow/dome] AVO overflights and photography have confirmed that a lava dome is actively growing in the summit crater. Occasional avalanches of hot blocks tumbling from the dome are traveling a short distance down the north flank of the volcano.
[Mudflow] To our knowledge, no mudflows have occurred in the Drift River since the last significant explosion.
[Other volcanic cloud information] An intermittent volcanic haze has been reported over south central Alaska. This cloud likely consists of water vapor, small quantities of volcanic gases, aerosols, and ash.

Hazard Analysis:
[Ash fall] While this type of activity persists, low-level clouds consisting of minor amounts of ash and volcanic gas may extend downwind for tens of miles and drop trace amounts of ash on communities.
[Ash cloud] Diffuse clouds containing trace amounts of ash and volcanic gas may be present downwind of the volcano.
[Lava flow/dome] A growing lava dome is inherently unstable and may produce explosions or avalanches of hot debris at any time.
[Mud flow] Additional mudflows may be produced by dome collapse events.

Remarks: Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano which rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, and 1989-90. The 1989-90 eruption produced mudflows, or lahars, that traveled down the Drift River and partially flooded the Drift River Oil Terminal facility. The ash plumes produced by the 1989-90 eruption affected air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities.

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:(20090403/1944Z)
(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/A31
(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:The eruption of Redoubt Volcano continues. Over the past several days, the intensity of ash-production has decreased. Current observations indicate a lava dome is growing in the summit crater. Therefore, we are lowering the alert level and aviation color code.

The 2009 eruption is now characterized by continuous emission of steam, volcanic gas, and variable amounts of ash. These processes are occurring as effusion of lava in the summit crater produces a lava dome. While at this level of activity, trace amounts of ash and a perceptible volcanic haze layer may be intermittently present throughout south-central Alaska.

A growing lava dome is inherently unstable; a sudden dome collapse or explosion can occur with no warning and produce a more voluminous ash cloud that rises to elevations above 25,000 feet. If such an event is detected, AVO would issue appropriate warnings.
(12) Volcanic cloud height:Over the last few days, a diffuse cloud of volcanic gas, ash, and steam is rising to variable altitudes over the volcano, but mostly less than 15,000 feet above sea level. At times of more vigorous ash production, the cloud has risen as high as 25,000 feet.
(13) Other volcanic cloud information:An intermittent volcanic haze has been reported over south central Alaska. This cloud likely consists of water vapor, small quantities of volcanic gases, aerosols, and ash.
(14) Remarks:Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano which rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, and 1989-90. The 1989-90 eruption produced mudflows, or lahars, that traveled down the Drift River and partially flooded the Drift River Oil Terminal facility. The ash plumes produced by the 1989-90 eruption affected air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities.
(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].
URL: www.avo.alaska.edu/activity/avoreport.php
Page modified: October 23, 2013 13:13
Contact Information: AVO Web Team

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