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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

INFORMATION RELEASE

Tuesday, August 23, 2005 1:45 PM AKDT (21:45 UTC)




CHIGINAGAK VOLCANO (CAVW #1102-11)

57°8.1’N 156°59.4’W, Summit Elevation 7,005 ft (2,135 m)

Current Level of Concern Color Code: Not Assigned



An AVO field crew reports that a 1,300 ft (400 m) wide melt-water lake has formed in the snow and ice filled summit crater at Chiginagak Volcano sometime since the last observations in August 2004. Sometime earlier this summer, the southern crater rim of Chiginagak was breached, allowing a portion of the lake to drain. The resulting lahar (a debris flow consisting of a mixture of volcanic sediment, water, and ice) left a deposit on the unnamed glacier draining the crater to the south and caused flooding of 3 to 6 ft (1 to 2 m) above normal on Indecision Creek. Volcano Creek and Mother Goose Lake, the headwaters of King Salmon River, were affected as well. Floodwaters also flowed on and through Chiginagak’s southeast glacier, spilling out into an unnamed Pacific drainage leading to Chiginagak Bay. The lahar likely contained acidic water. Although we have no direct samples of the summit lake water, measurements from crater lakes at similar volcanoes have shown pH values ranging from 0 to 3, the acidity arising mainly from sulfuric acid. Vegetation damage was observed along Indecision Creek and the unnamed Pacific drainage.



The breach in the crater rim and the ensuing lahar probably occurred in July 2005; reports from Painter Creek Lodge at this time tell of strong sulfur smells and cloudy, yellowish water in the Indecision Creek drainage



AVO geologists continue to investigate the event and its impacts. There are no indications that an eruption is imminent or that this event is necessarily precursory to an eruption.



Chiginagak Volcano is not seismically monitored. The nearest seismic networks are at Aniakchak and Ugashik-Peulik Volcanoes, both about 50 miles (80 km) away. It is AVO policy not to assign a color code of Green to a volcano without a real-time seismic network.



Chiginagak is a symmetric stratovolcano located 175 km (110 mi) south of King Salmon on the Alaska Peninsula. The nearest settlement is Pilot Point, 60 km (37 mi) to the northwest. The high flanks of the volcano are snow-and ice-covered, and a prominent fumarole located high on the north flank at about 5,500 ft (~1,675 m) constantly emits steam and sulfur gases. Historical eruptive activity has been minor and is poorly documented, however, the volcano is surrounded by pyroclastic deposits and lava flows that are likely less than a few thousand years old





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-GI

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].

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Page modified: May 27, 2014 10:23
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