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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, December 30, 2005 11:55 AM AKST (2055 UTC)




AUGUSTINE VOLCANO (CAVW#1103-01-)

59.3633°N 153.4333°W, Summit Elevation 4134 ft (1260 m)

Current Level of Concern Color Code: YELLOW



Unrest continues at Augustine Volcano. Although seismicity rates decreased this week compared to last week steam and gas emissions continue and small steam explosions could occur at any time. There are no indications at this time that a large eruption is imminent. Augustine remains in color code YELLOW and AVO continues to monitor the situation closely.



AVO scientists visited the volcano to install additional GPS receivers and deploy additional ash collection devices this week. While scientists were at the volcano a low cloud ceiling prevented views of the summit. The volcano was obscured by clouds in web cam and satellite images this week. However, brief views showed continued steaming. Weather prevented additional observation flights.



Observations continue to suggest that new magma is present beneath Augustine Volcano. Based on past eruptions at Augustine, AVO expects to see a sharp increase in earthquake activity prior to a significant explosive eruption. At this time, the level of seismicity is still well below that observed just prior to the 1986 eruption. However, small steam explosions are likely to continue to occur with no warning and could affect low-flying aircraft in the vicinity of the volcano.



Over the next week, AVO will conduct additional overflights and field visits to the island as weather permits.



Augustine Volcano is a 1260 m high (4134 ft) conical-shaped island stratovolcano located in southern Cook Inlet, about 290 km (180 mi) southwest of Anchorage, Alaska and 120 km (75 mi) southwest of Homer, Alaska. Historically, Augustine is the most active volcano in the Cook Inlet region with significant eruptions in 1812, 1883, 1908, 1935, 1963-64, 1976, and 1986. These eruptions were primarily explosive events that produced volcanic ash clouds (to 30,000-40,000 feet above sea level), ash fall, pyroclasic flows, and and lava domes or flows. During the 1883 eruption, a large avalanche on the north flank of the volcano flowed into Cook Inlet and may have initiated a tsunami observed at Nanwalek, about 90 km to the east.



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. Clouds obscured views of the volcano in web camera and satellite images most of this week. 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 all sides of the volcano, but primarily on the south and east flanks.



VENIAMINOF VOLCANO (CAVW#1102-07-)

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

Current Level of Concern Color Code: GREEN



Seismic activity at Veniaminof Volcano has been at background levels for several weeks. Cloudy conditions have persisted for most of the previous month preventing views of the volcano by satellite, web camera, and ground observers. However, brief views showed no activity. AVO has recieved no reports of ash emissions from pilots or observers on the ground. Given the decline of the seismicity it appears that the most recent episode of activity has ended, although based on the past behavior of the volcano, low level ash and steam emissions in the vicinity of the active cone may return at any time with little or no warning. The Level of Concern Color Code for Mount Veniaminof Volcano was thus downgraded from yellow to GREEN this week.



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. Recent significant eruptions of the volcano occurred in 1993-95 and 2005. Both were moderate Strombolian eruptions 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 and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano.



OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 30 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, Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Peulik, Ukinrek Maars, Aniakchak, Veniaminof, Pavlof, Dutton, Isanotski, Shishaldin, Fisher, Westdahl, Akutan, Makushin, Okmok, Korovin, 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



Jon Dehn, Acting Coordinating Scientist, UAF-GI

jdahn@gi.alaska.edu (907) 474-6499



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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