| UNREST AT SHISHALDIN VOLCANO |
February/March, 1999 |  |
WEEKLY UPDATE
Friday, May 28, 1:30 pm ADT (21:30 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: ORANGE Satellite imagery today shows no evidence of an ash plume or a thermal anomaly. A ground crew from AVO is currently on the north flank of the volcano and reports white steam from the summit crater. However, low levels of seismicity persist beneath the volcano, suggesting that explosive activity is still possible, characterized by low-level steam and ash bursts. The Level of Concern Color Code is therefore being kept at ORANGE. AVO staff members continue to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
INFORMATION RELEASE
Thursday, May 27, 4:00 pm ADT (00:00 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: ORANGE The lengthy ash-rich plume of last night from Shishaldin has not reappeared thus far today. However, low levels of seismicity persist beneath the volcano, suggesting that explosive activity characterized by low-level steam and ash bursts may still be occurring or likely to occur. A small thermal anomaly in the summit crater was visible in a satellite image at 1708 UT. The Level of Concern Color Code is therefore being kept at ORANGE. AVO staff continue to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
INFORMATION RELEASE
Thursday, May 27, 10:25 am ADT (1825 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: ORANGE Satellite imagery last night showed a continuous narrow ash-rich plume extending about 500 miles east-southeast from the volcano at altitudes of 15,000 to 20,000 ft. ASL until about 1:00 am ADT this morning (May 27). After 1:00 am ADT, the ash plume became detached from the volcano and had diminished significantly by 3:00 am ADT. However, low levels of seismicity persist beneath the volcano, suggesting that explosive activity characterized by low-level steam and ash bursts may still be occurring or likely to occur. The Level of Concern Color Code is therefore being kept at ORANGE. AVO staff continue to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
INFORMATION RELEASE
Wednesday, May 26, 4:45 pm ADT (0045 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: ORANGE Satellite imagery continues to show a narrow ash-rich plume extending at least 100 miles east-southeast from the volcano, likely at altitudes of 15,000 to 20,000 ft. ASL. Low to moderate levels of seismicity also persist beneath the volcano, suggesting that explosive activity characterized by low-level steam and ash bursts is occurring. The Level of Concern Color Code is therefore being kept at ORANGE. AVO staff continue to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
INFORMATION RELEASE
Wednesday, May 26, 10:00 am ADT (1800 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: ORANGE Satellite imagery indicates that a narrow ash-rich plume continues to be emitted from the volcano, extending about 70 miles southeast from Shishaldin at altitudes of up to 20,000 ft ASL; a pilot report at 4:03 pm ADT yesterday (May 25) indicated an ash-rich plume at 18,000 ft ASL. Currently, low to moderate levels of seismicity beneath the volcano suggest that short-lived explosive activity characterized by low-level steam and ash bursts is occurring. The Level of Concern Color Code is therefore being kept at ORANGE. AVO staff continue to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
INFORMATION RELEASE
Tuesday, May 25, 3:30 pm ADT (2330UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: ORANGE Satellite imagery indicates that a narrow ash-rich steam plume continues to be emitted from the volcano, extending 110 miles south from Shishaldin at altitudes of ~15,000 ft ASL. Currently, low to moderate levels of seismicity beneath the volcano suggest that short-lived explosive activity characterized by low-level steam and ash bursts is occurring. The Level of Concern Color Code is therefore being kept at ORANGE. AVO staff continue to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
WEEKLY UPDATE
Tuesday, May 25, 9:30 am ADT (1730UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Current Level of Concern Color Code: ORANGE
Previous Level of Concern Color Code: YELLOW A narrow ash-rich steam plume was seen in satellite imagery at 14:59 UTC this morning, extending 100 miles south from Shishaldin at an estimated altitude of ~15,000 ft ASL. An earlier pilot report at 0711 UTC last night also indicated a plume up to 20,000 ft ASL. Currently, low to moderate levels of seismicity beneath the volcano suggest that eruptive activity characterized by low-level steam and ash bursts is occurring with ash plume levels probably below 20,000 ft ASL. The Level of Concern Color Code has therefore been raised to ORANGE. AVO staff continues to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
WEEKLY UPDATE
Friday, May 21, 1:30 pm ADT (2130UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: YELLOW During this week, no eruptive activity was observed or reported at Shishaldin, perhaps due to the poor weather conditions. Because of the persistence of low level seismicity and the summit thermal anomaly, the Level of Concern Color Code remains YELLOW. Eruptive activity similar to that of last week, characterized by low-level steam and ash bursts, could occur with little or no warning. AVO staff continues to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
WEEKLY UPDATE
Friday, May 14, 1999 12:00 pm ADT (2000 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: YELLOW The only activity recorded or observed at Shishaldin during the last week was a brief steam and ash emission on Thursday that produced a short-lived plume which rose 1,000 ft (300 m) above the summit. On Wednesday night, a weak thermal anomaly was visible on satellite imagery and weak seismic tremor was recorded. The Level of Concern Color Code at Shishaldin remains Yellow. Although thermal and seismic levels are low, eruptive activity similar to that of yesterday, characterized by minor, low-level steam and ash bursts, could occur with little or no warning. AVO staff continues to monitor the situation 24 hours a day with real-time seismic and satellite data.
ALASKA VOLCANO OBSERVATORY
INFORMATION RELEASE
Thursday, May 13, 1999 2:30 PM ADT (2230 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: YELLOW AVO received a report from the National Weather Service (NWS) in Cold Bay at 11 am ADT (1900 UT) of a small steam and ash burst at Shishaldin observed by the crew of a NWS boat at the north end of False Pass. The activity was observed at about 10:25 am ADT (1825 UT) and characterized as 3 puffs which produced a plume that rose to about 1,000 ft (300 m) above the summit. A pilot report at 11:55 am ADT (1955 UT) confirmed the activity. A weak thermal anomaly was noted on satellite imagery last night, and there were some indications of weak seismic tremor.
ALASKA VOLCANO OBSERVATORY
WEEKLY UPDATE
Friday, May 7, 1999 2:00 pm ADT (2200 UT) SHISHALDIN VOLCANO
54°45.33' 163°58.00'
Summit Elevation 9,373 ft (2,857 m) Level of Concern Color Code: YELLOW During the last week a few small ash-poor plumes were observed at Shishaldin in satellite data, but no thermal anomalies or other indicators of significant eruptive activity were seen. Seismicity levels continue to be low, and so the Level of Concern Color Code at Shishaldin remains Yellow. Although seismicity levels are low, eruptive activity could resume with little or no warning. AVO staff continues to monitor the situation 24 hours a day with real-time seismic and satellite data.
Due to the high number of updates concerning Shishaldin Volcano, we have archived information releases prior to the month of June. May updates
April updates
March updates
February updates 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 RECORDING OF THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478 CONTACT INFORMATION:
Terry Keith, Scientist-in-Charge, USGS tkeith@tundra.wr.usgs.gov (907) 786-7443
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.
