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AVO/USGS Volcanic Activity Notice

Volcano: Okmok (CAVW #1101-29-)

Current Volcano Alert Level: NORMAL
Previous Volcano Alert Level: ADVISORY

Current Aviation Color Code: GREEN
Previous Aviation Color Code: YELLOW

Issued: Friday, March 20, 2009, 11:01 AM AKDT (20090320/1901Z)
Source: Alaska Volcano Observatory
Notice Number: 2009/A9
Location: N 53 deg 23 min W 168 deg 9 min
Elevation: 3520 ft (1073 m)
Area: Aleutians Alaska

Volcanic Activity Summary: AVO is decreasing the Aviation Color Code to GREEN and the Volcanic Alert Level to NORMAL for Okmok volcano.

Seismic activity at Okmok has been at low to near background levels and satellite views show no activity over the past two weeks. AVO has received no reports of activity.

Recent Observations:
[Volcanic cloud height] Unknown
[Other volcanic cloud information] Unknown

Remarks: Okmok volcano was in vigorous eruption from July 12 through mid-August, 2008. Energetic, intermittent ash emission from several vents within the caldera blanketed much of the northeast portion of Umnak Island with ash and dusted Unalaska/Dutch Harbor with fine ash on several occasions. Rain-induced remobilization of debris from high on the volcano's flanks produced lahars down many drainages, forming new deltas at the coastline. A new, 200-300 m-high (660-980 ft) tephra cone developed inside the caldera at the primary eruption site. Since late August 2008, seismicity at Okmok has generally declined. The last confirmed ash emission at Okmok occurred on August 19, 2008.

Okmok volcano is a 6-mile-wide caldera that occupies most of the eastern end of Umnak Island, located 75 miles southwest of Unalaska/Dutch Harbor in the eastern Aleutian Islands. Okmok has had several eruptions in historic time typically consisting of ash emissions occasionally to over 30,000 feet ASL but generally much lower; lava flows crossed the caldera floor in 1945 and 1958. Prior to 2008, the volcano last erupted in February 1997 producing lava flows and intermittent ash emissions over the course of several months.

The nearest settlement is Nikolski, population about 35, roughly 45 miles west of the volcano. A ranch caretaker family lives at Fort Glenn on the flank of the volcano about 6 miles east of the caldera rim.

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:(20090320/1901Z)
(3) Volcano:Okmok (CAVW# 1101-29-)
(4) Current Color Code:GREEN
(5) Previous Color Code:yellow
(6) Source:Alaska Volcano Observatory
(7) Notice Number:2009/A9
(8) Volcano Location:N 53 deg 23 min W 168 deg 9 min
(9) Area:Aleutians Alaska
(10) Summit Elevation:3520 ft (1073 m)
(11) Volcanic Activity Summary:AVO is decreasing the Aviation Color Code to GREEN and the Volcanic Alert Level to NORMAL for Okmok volcano.

Seismic activity at Okmok has been at low to near background levels and satellite views show no activity over the past two weeks. AVO has received no reports of activity.

(12) Volcanic cloud height:Unknown
(13) Other volcanic cloud information:Unknown
(14) Remarks:Okmok volcano was in vigorous eruption from July 12 through mid-August, 2008. Energetic, intermittent ash emission from several vents within the caldera blanketed much of the northeast portion of Umnak Island with ash and dusted Unalaska/Dutch Harbor with fine ash on several occasions. Rain-induced remobilization of debris from high on the volcano's flanks produced lahars down many drainages, forming new deltas at the coastline. A new, 200-300 m-high (660-980 ft) tephra cone developed inside the caldera at the primary eruption site. Since late August 2008, seismicity at Okmok has generally declined. The last confirmed ash emission at Okmok occurred on August 19, 2008.

Okmok volcano is a 6-mile-wide caldera that occupies most of the eastern end of Umnak Island, located 75 miles southwest of Unalaska/Dutch Harbor in the eastern Aleutian Islands. Okmok has had several eruptions in historic time typically consisting of ash emissions occasionally to over 30,000 feet ASL but generally much lower; lava flows crossed the caldera floor in 1945 and 1958. Prior to 2008, the volcano last erupted in February 1997 producing lava flows and intermittent ash emissions over the course of several months.

The nearest settlement is Nikolski, population about 35, roughly 45 miles west of the volcano. A ranch caretaker family lives at Fort Glenn on the flank of the volcano about 6 miles east of the caldera rim.
(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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