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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

Weekly Update

Friday, September 22, 2006 12:45 PM AKDT (2045 UTC)




FOURPEAKED VOLCANO (CAVW#1102-26-)

58°46'12" N153°40'19" W, Summit Elevation 6903 ft (2104 m)

Current Level of Concern Color Code: YELLOW



AVO raised the Level of Concern Color Code for Fourpeaked volcano from “Not Assigned” to YELLOW on Wednesday, September 20. A large steam explosion near the summit of Fourpeaked volcano occurred on Sunday, September 17 beginning at approximately 12:00 noon AKDT (2000 UTC, September 18). Photographs and NEXRAD weather radar show that the plume reached up to approximately 20,000 ft (6,000 m) above sea level. Satellite images showed a cloud originating from Fourpeaked volcano, and persisting throughout the night. No ash or thermal anomalies have been detected in satellite images. The plume was visible on NEXRAD until 9:45 PM AKDT September 17 (0545 September 18 UTC). AVO staff conducted both fixed-wing and helicopter overflights in the Cape Douglas area September 20 and confirmed the source of volcanic activity to be Fourpeaked volcano.



A small but distinct SO2 cloud over the area was detected by researchers from the Univ. of Maryland-Baltimore County using a new NASA satellite-based UV sensor (the Ozone Mapping Instrument, or OMI) at 3:00 PM AKDT (2300 UTC) September 17. Puff windfield modeling showed that the plume would have spread west and then moved north over the next day or so. This is consistent with pilot reports received by AVO on September 18 that described a strong sulfur smell in the Stony River Valley, ~200 miles west of Anchorage. Subsequent passes of the OMI have also shown an SO2 cloud whose position is consistent with Puff modeling. AVO has received several accounts of very light ashfall, in Homer and near Nonvianuk Lake in Katmai National Park, that are also consistent with Puff modeling.



There is currently no real-time local seismic network on the volcano. The closest seismometer is 40 miles (64 km) to the north. A small swarm of tectonic earthquakes was detected on the regional seismic network from 11:48 AM to 3:50 PM AKDT (19:48 to 23:50 UTC) September 17. No explosion signals were detected seismically, but the infrasound array at the University of Alaska-Fairbanks picked up a signal from the Fourpeaked area with an origin time consistent with the other data.



There have been no known historical eruptions of Fourpeaked and no known geologic evidence for activity in the last 10,000 years. These factors and the lack of close-in seismic monitoring limit AVO’s ability to forecast likely future activity. A helicopter flight is scheduled for this weekend to make geologic observations, collect samples, and install telemetered seismometers. AVO continues to monitor Fourpeaked using satellite images.





VENIAMINOF VOLCANO (CAVW#1102-07-)

56°11'44" N159°23'18" W, Summit Elevation 8225 ft (2507 m)

Current Level of Concern Color Code: YELLOW



Seismicity at Veniaminof has remained low this week, but a few larger-than-normal earthquakes were detected. Seismicity is still above background. Satellite and web camera views during brief periods of clear weather showed a small, white steam plume and no signs of ash emission.



Intermittent, short-lived, very small-volume steam and ash bursts from the intracaldera cone have been common over the past few years. Ash from these events is not likely to extend beyond the caldera rim. There are no indications that a larger eruption is imminent.





CLEVELAND VOLCANO (CAVW#1101-24-)

52°49'24" N169°56'35" W, Summit Elevation 5676 ft (1730 m)

Current Level of Concern Color Code: YELLOW



Cleveland was obscured by clouds for most of the week, but the few partly clear satellite views showed nothing unusual.



Cleveland volcano has produced brief, explosive eruptions sending ash clouds to elevations of 10,000 – 20,000 ft ASL on at least five occasions since February 2006 with the most recent confirmed explosion occurring on August 24, 2006. Additional short-lived, low-level ash explosions (less than 10,000 feet ASL) could continue intermittently for months or years.



AVO monitors Cleveland using satellite images. There is no real-time seismic network on the island and AVO is unable to track local earthquake activity that may indicate volcanic unrest. Short-lived ash explosions may continue to occur without warning. Should a more significant ash explosion occur (greater than 20,000 feet ASL), detection by satellite analysis is more likely.





OTHER ALASKA VOLCANOES



Seismic activity is monitored in real time at 30 volcanoes in Alaska. Satellite images of all Alaskan volcanoes are analyzed daily for evidence of ash plumes and elevated surface temperatures. Some volcanoes may currently display anomalous behavior but are not considered to be at a dangerous level of unrest. Wrangell, Spurr, Redoubt, Iliamna, Augustine, Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Peulik, Ukinrek Maars, Aniakchak, Pavlof, Dutton, Isanotski, Shishaldin, Fisher, Westdahl, Akutan, Makushin, Okmok, Korovin, Great Sitkin, Kanaga, Tanaga, and Gareloi volcanoes are in color code GREEN. All are at or near normal levels of background seismicity. AVO did not detect ash plumes or significant elevated surface temperatures in the vicinity of any volcano.



ABBREVIATED COLOR CODE KEY (contact AVO for complete description):



GREEN volcano is dormant; normal seismicity and fumarolic activity occurring

YELLOW volcano is restless; eruption may occur

ORANGE volcano is in eruption or eruption may occur at any time

RED significant eruption is occurring or explosive eruption expected at any time



VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu

RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478



CONTACT INFORMATION:

Tom Murray, Scientist-in-Charge, USGS

tlmurray@usgs.gov (907) 786-7497



Steve McNutt, Acting Coordinating Scientist, UAF

steve@giseis.alaska.edu (907) 474-7131



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.
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].

PDF version of these definitions
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URL: avo.alaska.edu/activity/avoreport_archives.php
Page modified: May 27, 2014 10:23
Contact Information: AVO Web Team

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