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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, November 4, 2005 2:50 PM AKST (2350 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 Mount Spurr volcano remains above background. Steaming was observed in clear webcam views much of the week. In response to a vigorous summit steam plume on Wednesday, AVO scientists conducted an observation overflight Thursday morning. The crater lake level and actively steaming areas in and around the crater were unchanged from previous observations from October 9. We expect steaming to continue. Clear to partly cloudy webcam and satellite views have shown no other unusual activity. 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 approximately 120 km (75 mi) west of Anchorage. 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 on 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: YELLOW



Mostly clear satellite views last night showed a return of thermal anomalies at the summit of Cleveland volcano. No ash has been detected since a brief ash burst that rose no higher than 4,600 m (15,000 ft) ASL on October 7. No reports of activity have been received from pilots or ground-based observers. Based on the past eruptive activity at Cleveland, occasional ash emissions may occur with little warning. Cleveland is not monitored with seismic instruments and our only means of ash detection at this time is satellite observation or eyewitness observations.



Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located 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 three 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 occurred in October 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



Elevated seismic activity below young volcanic vents on Tanaga Island continues. Extended periods of low-level volcanic tremor were detected at stations closest to Takawangha volcano, the easternmost vent of the Tanaga volcano cluster. Partly cloudy satellite views of the volcano showed nothing unusual.



Tanaga Island lies in the Andreanof Islands approximately 100 km (62 miles) west of the community of Adak and 2025 km (1260 miles) SW of Anchorage. The northern half of the island is home to the Tanaga volcanic complex, comprising three main volcanic edifices. Tanaga volcano is the tallest of these (1,806 m or 5,925 ft) and lies in the center of the complex. The last reported eruption of Tanaga occurred in 1914 and earlier eruptions were reported in 1763-1770, 1791, and 1829. Records 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 from a 1,584 m (5,197 ft)-high satellite vent on the volcano's northeast flank. Immediately west of Tanaga volcano lies Sajaka, a 1,354 m (4,443 ft)-high compound edifice with an older cone to the east that collapsed into the sea within the last few thousand years, and a new cone that has grown in the breach. The new cone is 1,312 m (4,305 ft) high and consists of steeply dipping, interbedded cinders and thin, spatter-fed lava flows. To the east of Tanaga lies Takawangha. Takawangha's 1,449 m (4,754 ft)-high summit is mostly ice-covered, except for four young craters that have erupted ash and lava flows in the last few thousand years. Parts of Takawangha's edifice are hydrothermally altered and may be unstable, and they could produce localized debris avalanches. No historical eruptions are known from Sajaka or Takawangha; however, field work shows that recent eruptions have occurred and it is possible that historic eruptions attributed only to Tanaga may instead have come from these other vents.



VENIAMINOF VOLCANO (CAVW#1102-07-)

56.1956°N 159.3883°W, Summit Elevation 8225 ft (2507 m)

Current Level of Concern Color Code: YELLOW



A low-level, minor ash emission was observed coming from the intracaldera cone of Mount Veniaminof this morning in AVO webcam images from Perryville. Since the activity is above normal background, the color code for Mount Veniaminof was upgraded to YELLOW today in an earlier Information Release.



The ash emission started at about 9:29 AM AST (1829 UTC) this morning. The discrete ash emission was small, rising a few hundred meters (several hundred feet) above the cone, which has an elevation of 2,156 m (7,073 ft) above sea level, and dissipated rapidly as it drifted towards the east. Ash fall is likely very minor, and confined to the summit caldera. Occasional steaming from the intracaldera cone has also been observed during the past two weeks.



Very weak seismic tremor and a few small discrete seismic events have been seen at the station closest to the active cone. However, there are no indications from seismic data that a significantly larger eruption is imminent. We expect that steam and ash emissions may continue intermittently and could pose a hazard to people and low-flying aircraft in the vicinity of the active cone.



Mount Veniaminof volcano is an andesitic stratovolcano with an ice-filled 10-km 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 (~ 300 km3) and most active volcanic centers in the Aleutian Arc and has erupted at least 13 times in the past 200 years. Significant eruptions of the volcano occurred most recently in 1993-95 and 2005. Both were moderate Strombolian episodes producing intermittent low-level jets of incandescent lava fragments, and low-level emissions of steam and ash from the main intracaldera cone. During the 1993-95 activity, a small lava flow was extruded into the summit caldera ice field producing an ice pit. Minor ash-producing explosions occurred in 2002, 2004, early 2005, and in recent weeks. Previous historical eruptions have produced ash plumes that reached 6,000 m (20,000 ft) above sea level. Ash fallout that blanketed areas within about 40 km (25 mi) of the volcano.



KATMAI VOLCANO (CAVW#1102-17-)

58.2797°N 154.9633°W, Summit Elevation 6716 ft (2047 m)

Current Level of Concern Color Code: GREEN



Strong winds in the Katmai area picked up loose 1912 volcanic ash and carried it east over Kodiak Island. AVO detected in satellite data a large area of resuspended ash blowing from the vicinity of Katmai and the Valley of Ten Thousand Smokes to Kodiak Island. The National Weather Service estimated the top of the plume at 1,525m (5,000 ft).



This phenomenon is not the result of volcanic activity and has occurred before in the Katmai area and other young volcanic areas of Alaska. No eruption is in progress. Resuspended volcanic ash should be considered as hazardous as primary volcanic ash and could be damaging to aircraft. All of the volcanoes of the Katmai area (Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin) remain at color code GREEN.





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, 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



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].

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Page modified: May 27, 2014 10:23
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