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ARCHIVED REPORT
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ALASKA VOLCANOES UPDATE

Friday, February 11, 2000 12:30 PM

AST (2130 UT)

Shishaldin Volcano:

5445.33N 16358.00W (CAVW

#1101-36)

Summit Elevation 9,373 ft (2,857 m)

LEVEL OF CONCERN COLOR CODE

IS YELLOW

Small low-frequency seismic events,

present at Shishaldin volcano

since last summer, continued this

past week at a slower rate and

slightly lower amplitude. Seismic

data also continue to show the

presence of small explosions,

which we interpret to be phreatic

(caused by the flashing of water

to steam). No thermal anomaly

has been observed in satellite

imagery and no seismic tremor

has been identified; both were

seen prior to the last eruptive

episode in April and May of 1999.

Due to the elevated seismicity, we

are maintaining the Level of

Concern Color Code for

Shishaldin at YELLOW.

AVO is monitoring the situation closely

with real-time satellite and seismic

data and will issue further updates

as the situation warrants.

Alaska Volcanoes:

No Change.

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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