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Archived Report
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ALASKA VOLCANO OBSERVATORY

INFORMATION RELEASE

Friday, December 2, 2005 10:55 AM AKST (1955 UTC)




This email was mistakenly sent as an AVO weekly update rather than an information release.



The Alaska Volcano Observatory announces formal seismic monitoring of two additional volcanic centers in Alaska. New seismic networks have been in place for a sufficient period of time to allow us to define a level of non-eruptive background earthquake activity and character. Thus, we will add Ukinrek Maars and Korovin Volcano to our weekly status reports.



UKINREK MAARS VOLCANO (CAVW#1102-131)

57.8317°N 156.5097°W, Summit Elevation 299 ft (91 m)

Current Level of Concern Color Code: GREEN



In August 2004, a seven station seismic network was installed in the Ugashik-Peulik area. The geometry of this network is sufficient to detect all earthquakes above a ML=0.9 in the vicinity of the Ukinrek Maars. For the last 16 months, an average of seven earthquakes per month were detected, with little seismicity in the vicinity of the Ukinrek Maars.



Ukinrek Maars are a pair of low-relief explosion craters that formed over 9-day eruption in March and April of 1977. The craters developed on a low ridge just south of the southern shore of Becharof Lake on the Alaska Peninsula, about 100 km (62 mi) south of King Salmon. The west maar is the smaller of the two and is about 170 m across, and 35 m deep. The east maar is more circular in shape, up to 300 m across and about 70 m deep. It contains a lake that now covers remnants of a spatter cone that developed late in the eruption. The rims of these craters are constructed of deposits from the explosive activity including coarse to fine ash, lapilli, and large blocks or bombs. The ash clouds associated with this eruption in 1977 reached approximately 6.5 km (21,000 ft) above sea level. Maar eruptions form when rising magma intersects water-saturated ground or a shallow body of water. They tend to be monogenetic, meaning that usually, no further eruptions will occur from the same site. However, the maars are only the most recent of at least four monogenetic vents in the immediate vicinity, therefore additional monogenetic vents may form in the future.



More information regarding Ukinrek can be found on the AVO web site:

http://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Ukinrek%20Maars





KOROVIN VOLCANO (CAVW#1101-16)

52.3811°N 174.1542°W, Summit Elevation 5030 ft (1533 m)

Current Level of Concern Color Code: GREEN



Since March 2005 AVO has been receiving seismic data from a seven-station network surrounding Korovin Volcano and neighboring Mount Kliuchef. Over the last nine months, an average of eight earthquakes per month have been detected on the northern part of Atka Island. A broadband station in Atka, operated by AEIC provides additional information on the Korovin earthquakes.



Korovin Volcano is a 1,553 m (5,030 ft) high stratovolcano located on the northern part of Atka Island in the central Aleutian Islands, about 184 km (110 mi) east of Adak, 538 km (350 mi) west of Dutch Harbor, and 1748 km (1086 mi) southwest of Anchorage. The volcano has two distinct summit vents that have been the sites of historic eruptive activity as recently as June 1998. The southeastern summit vent consists of a steep-walled crater that contains a shallow lake that has an elevated temperature due to fumaroles within the crater. Occasionally, a vigorous steam plume rises from this crater. Known eruptions at Korovin occurred in 1907, 1951, 1953, 1954, 1973, 1976, 1986, 1987, 1996, and 1998. All produced minor amounts of ash and in some cases, small lahars and lava flows. The ash plume produced by the 1998 eruption was not well-constrained but may have reached 4900 to 9200 m (16,000 to 30,000 ft) above sea level. Other young volcanic cones in the vicinity of Korovin include Konia and Kliuchef; both of which have likely erupted within the last 10,000 years. Hot springs and fumaroles occur on the south and west flanks of Kliuchef and also in a glacial valley about 4 miles (6 km) southwest of Korovin.



More information regarding Korovin can be found on the AVO web site:

http://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Korovin





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



Chris Nye, Acting Coordinating Scientist, UAF-GI

cnye@giseis.alaska.edu (907) 590-3111



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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Page modified: June 11, 2012 11:50
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