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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, February 4, 2005 12:00 PM AST (21:00 UTC)



MOUNT VENIAMINOF VOLCANO (CAVW #1102-07)

56°10'N 159°23'W, Summit Cone Elevation 7,073 ft (2,156 m)

Current Level of Concern Color Code: ORANGE



Last night, strombolian activity, or ejection of hot blocks and lava, was

clearly visible to residents of Perryville, 30 km (22 miles) from the

volcano. The eruption was also visible in web camera views and seen by

satellite as an increase in surface heat. After a decrease in seismic

activity through the early morning, seismicity has picked up and is again

at a level similar to last night, suggesting that strombolian activity is

continuing; however, clouds currently block views of the volcano. We still

do not expect that this current activity will put ash into the air above

13,000 ft (4,000 m) above sea level. The Level of Concern Color Code for

Mount Veniaminof Volcano remains ORANGE.



Prior to last night, seismicity this week was similar to what was observed

the previous week, consisting of low-amplitude volcanic tremor with

occasional larger bursts. When weather permitted, satellite imagery showed

anomalous heat at the summit cone, consistent with hot blocks and ash being

ejected from the active vent, and the web camera showed intermittent ash

plumes reaching as high as 10,000 ft (3,000 m) above sea level.



Mount Veniaminof has been at ORANGE since January 10, 2005. Very weak

volcanic tremor was first observed on January 1 and it significantly

increased in magnitude over the next week. Beginning on January 8 satellite

images showed a heat anomaly in the vicinity of Veniaminof’s summit. Web

camera views showed that small ash emissions from the intracaldera cone of

Mount Veniaminof, some reaching nearly 13,000 ft (4,000 m) above sea level,

were occurring more or less continuously from January 8-10. The maximum

amplitude of the seismicity so far during this period has slightly exceeded

that observed during the previous phase of unrest, which ended in September

2004. An overflight of the volcano on January 11 showed no evidence of lava

flows or substantial glacial melting.



Low-level strombolian activity that ejects blocks of hot rock and lava

could occur with little or no warning, though the ejecta would stay within

the summit caldera. We expect steam and ash emissions to continue and could

pose a hazard to people and low-flying aircraft in the vicinity of the

active cone. Light ash falls outside of the summit caldera are possible.



Web-camera pictures of Mount Veniaminof are available on the internet at:



http://www.avo.alaska.edu/avo4/atlas/volc/venia/veni2004/index.htm



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 12 times in the past

200 years. The most recent significant eruption of the volcano occurred in

1993-95 and was a moderate Strombolian eruption from the main intracaldera

cone in the northwest sector of the caldera above Cone Glacier. The

eruption was characterized by intermittent low-level emissions of steam and

ash, and a small lava flow was extruded into the summit caldera ice field

producing an ice pit. Minor ash-producing explosions occurred in 2002,

2004, 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.



MOUNT SPURR VOLCANO (CAVW#1103-04)

61°18' N 152°15' W, Summit Elevation 11,070 ft (3,374 m)

Current Level of Concern Color Code: YELLOW



Elevated levels of seismicity continue to be recorded at Mount Spurr. The

level of seismicity was particularly high on January 28 and 29, with 86 and

44 located earthquakes on those days, respectively. Since then, activity

has dropped to previous, still elevated, levels at a rate of approximately

seven events per day. No activity was observed in satellite and web camera

images this week. There are no indications that an eruption is imminent.



Web-camera pictures of Mount Spurr are available on the internet at:



http://www.avo.alaska.edu/avo4/atlas/volc/spurr/spurr2004/index.html



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 27 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, Aniakchak, 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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Page modified: May 27, 2014 10:23
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