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ARCHIVED REPORT
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Alaska Volcanoes Update

February 13, 1997, 12:30 PM AST (2130 UTC)



Okmok Volcano: 5524' N, 16810' W;

caldera rim elevation 3520 feet (1,073 m) elevation of erupting

cone about 2500 feet (760 m)



A small eruption began this morning at Okmok volcano on Umnak Island,

in the eastern Aleutian Islands, about 75 miles west-southwest of

Dutch Harbor. AVO received a report from observers at the

former Fort Glenn military base at the east end of the island at 10:46

am AST that an ash plume began rising from a cone inside the

caldera at about 10 am AST. The dark plume rose to about 5,000

feet ASL, was carried to the southwest by prevailing winds and

was described as dissipating somewhat at the time of the call.

Satellite images from 5 am and 10:30 am AST show a hot spot in

the vicinity of a cone along the south rim of the caldera. AVO

does not have seismic monitoring equipment on the island and

therefore at this time is not instituting a color code designation.



Okmok volcano is a 6-mile-wide caldera that occupies most of the

eastern end of Umnak Island that has had several eruptions in

historic time. Historic eruptions typically consist of ash emissions

occasionally to over 30,000 feet but generally to much lower

altitudes; lava flows crossed the caldera floor in 1945 and 1958.

The last eruption occurred November 1986 through February

1988 and was characterized by intermittent ash emission.

The nearest settlements are Nikolski, population about 35, about 45

miles west of the volcano, and a small number of people at the

abandoned Fort Glenn military base 10 miles east of the volcano.

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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