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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, September 16, 2005 12:55 PM AKDT (20:55 UTC)






VENIAMINOF VOLCANO CAVW#(1102-07-)

56.2 W 159.39 N, Summit Elevation 8225 ft (2507 m)

Current Level of Concern Color Code: YELLOW



Poor weather this week hampered web camera and satellite observations of Veniaminof, but seismic data indicated that minor ash emissions continued at a very low rate of 1-5 events per day. Based on past experience, it is likely that diffuse ash plumes rose to heights of less than 10,000 ft above sea level and were confined to the summit caldera. There are no indications that more vigorous activity is imminent or even likely. We expect steam and ash emissions to continue intermittently and these emissions could pose a hazard to people and low-flying aircraft in the vicinity of the active cone.



AVO will continue to monitor activity at Mount Veniaminof using seismic data, satellite images, internet camera data and observer reports.



Mount Veniaminof volcano is a young stratovolcano with an ice-filled 10-km (6 mi) diameter summit caldera located on the Alaska Peninsula, 775 km (480 mi) southwest of Anchorage and 35 km (22 mi) north of Perryville. Veniaminof is one of the largest and most active volcanic centers in the Aleutian Arc and has erupted at least 12 times in the past 200 years. The most recent significant eruption of the volcano occurred in 1993-95 and was characterized by intermittent, low-level emissions of steam and ash, and a small lava flow onto the summit caldera ice field producing an ice pit. Previous historical eruptions have produced ash plumes that reached 6,000 m (20,000 ft) above sea level and associated ash fall within about 40 km (25 mi) of the volcano. Minor ash emissions similar to those that occurred this week were also detected in early 2005.





SPURR VOLCANO CAVW#(1103-04-)

61.3 W 152.25 N, Summit Elevation 11070 ft (3374 m)

Current Level of Concern Color Code: YELLOW



The level of seismic activity at Mt. Spurr volcano remains above background, but there are several indications that the level of unrest is declining. Recent observations of the summit lake show a change in the water color from slate gray to blue-green, which may be indicative of decreasing sulfur dioxide gas emissions. In addition, there were no observations of the vigorous upwelling (of gases) that had been seen in the lake earlier this summer. The overall rate of seismicity has been gradually declining over the past several months, further suggesting a reduced level of activity. Minor steaming continues from the summit melt pit and occasionally from Crater Peak. There are no indications that an eruption is imminent.



Mount Spurr volcano is an ice- and snow-covered stratovolcano located on the west side of Cook Inlet. The only known historical eruptions occurred in 1953 and 1992 from the Crater Peak flank vent located 3.5 km (2 mi) south of the summit of Mount Spurr. These eruptions were brief, explosive, and produced columns of ash that rose up to 20 km (65,000 ft) above sea level and deposited several mm of ash in south-central Alaska, including approximately 6 mm of ash on Anchorage in 1953. The last known eruption from the summit of Mount Spurr was more than 5,000 years ago. Primary hazards during future eruptions include far-traveled ash clouds, ash fall, pyroclastic flows, and lahars or mudflows that could inundate drainages all sides of the volcano, but primarily on the south and east flanks.



OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 28 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, Redoubt, Iliamna, Augustine, Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Peulik, Aniakchak, Veniaminof, Pavlof, Dutton, Isanotski, Shishaldin, Fisher, Westdahl, Akutan, Makushin, Okmok, 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



John Eichelberger, Coordinating Scientist, UAF-GI,

eich@gi.alaska.edu (907) 474-5530





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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