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ARCHIVED REPORT
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SHISHALDIN VOLCANO



CURRENT LEVEL OF CONCERN COLOR CODE IS YELLOW



The level of concern color code is raised to YELLOW due to the persistence of a thermal anomaly in the summit crater of Shishaldin, identification of low-level seismic tremor, and pilot and ground observations reported today of a large steam plume rising to 19,000 feet (5,800 m) ASL.



National Weather Service (NWS) personnel in Cold Bay, 58 miles (93 km) east-northeast of the volcano, observed anomalous steaming at Shishaldin volcano last week, and a vigorous steam plume rose as high as 6,000 feet (1,830 m) above the vent. Satellite imagery of February 9 showed the steam plume and a thermal anomaly at the vent. The steam activity decreased throughout the week to light puffs rising a few hundred feet above the vent, however the thermal anomaly at the vent persisted through today. A new seismic net monitoring Shishaldin volcano recorded slightly elevated seismicity beginning the end of January, and low-level tremor has now been identified. A large steam plume was visible to NWS ground observers in Cold Bay today. No ash has been detected on satellite imagery but the thermal anomaly persists. Under these conditions, a low-level ash burst could occur with little or no warning.

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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