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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, October 7, 2005 4:05 PM AKDT (005 UTC)




SPURR VOLCANO (CAVW#1103-04-)

61.2994°N 152.2511°W, 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 with an increase in the rate of earthquakes this week. Occasional views of the volcano by web camera and satellite much of the week showed no unusual activity. Some minor steaming continues from the summit melt pit and 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.



CLEVELAND VOLCANO (CAVW#1101-24-)

52.8232°N 169.9431°W, Summit Elevation 5676 ft (1730 m)

Current Level of Concern Color Code: ORANGE



The Alaska Volcano Observatory detected a small drifting volcanic ash cloud in satellite data this morning. The ash cloud was located east of the volcano and approximately 90 miles (150 km) ESE of Dutch Harbor at 1700 UTC. Based on the satellite data, the ash came from a small eruption of Mount Cleveland sometime before 03:00 ADT (1100 UTC). The prior estimate of 0145 AKDT for the eruption onset is questionable. AVO, in consultation with the National Weather Service, estimates the top of the ash cloud reached no more than 15,000 ft above sea level (4600 m). The ash cloud dissipated and was not detected via satellite after 1800 UTC. The level of concern color code for Cleveland remains at ORANGE.



AVO does not operate a seismic network on Cleveland Volcano. Historical eruptions at Cleveland volcano have been characterized by short-lived explosive bursts of ash, at times accompanied by lava fountaining, lava flows, and debris flows down the flanks. Based on this record, it is possible that explosive, ash-producing events could occur at any time and without warning (owing to the lack of local seismic monitoring). AVO will continue to monitor the volcano using satellite images.



Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 and had 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in July 2005.



TANAGA VOLCANO (CAVW#1101-08-)

51.885°N 178.1458°W, Summit Elevation 5925 ft (1806 m)

Current Level of Concern Color Code: YELLOW



The earthquake activity that began at Tanaga Volcano on October 1 has grown over the past 32 hours. Marked increases in the rate of earthquake occurrence took place late on October 5 and then again at roughly 5:00 AM AKDT today. The located earthquakes range in magnitude from 0.5 to 1.9 and now range in depth from 6 to 12 km beneath the volcano's summit. These locations represent both an increase in magnitude and a change in depths and locations compared with events recorded at Tanaga between October 1 and 5. In response to the observed changes in seismic activity the Alaska Volcano Observatory (AVO) raised the level of concern color code to YELLOW. While the current rate of earthquake activity represents a significant increase in rate, the size, depths and character of the events are not indicative of imminent eruptive activity. AVO will continue to monitor the activity at Tanaga closely.



Tanaga is a remote, 1,806 m (5,925 ft)-high stratovolcano located on the northwest portion of Tanaga Island, roughly 105 km (63 miles) west of Adak in the Andreanof Islands. The last known eruption of Tanaga occurred in 1914 and earlier eruptions were reported in 1763-1770, 1791, and 1829. Reports of these eruptions are vague, but deposits on the flanks of the volcano show that typical eruptions produce blocky lava flows and occasional ash clouds. Eruptions have occurred both from the summit vent and a 1,584 m (5,197 ft)-high satellite vent on the volcano's northeast flank.



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, 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-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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