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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

Weekly Update

Friday, August 17, 2007 2:30 PM AKDT (2230 UTC)




PAVLOF VOLCANO (CAVW#1102-03-)

55°24'57" N161°53'24" W, Summit Elevation 8261 ft (2518 m)

Current Aviation Color Code: ORANGE

Current Volcano Alert Level: Watch



Pavlof Volcano, on the Alaska Peninsula, has been erupting since at least early Wednesday, August 15. AVO is maintaining aviation color code ORANGE and volcanic activity alert level WATCH at this time.



Persistent earthquake activity and flow events, probably lahars (mudflows), continue at Pavlof Volcano. Several discrete explosion earthquakes have also been recorded. Though clouds obscured the volcano in satellite images Friday morning, one GOES satellite image shows that the large thermal feature from the summit eruption persists. These observations show that an eruption of lava at the surface is continuing. While a primary hazard from this eruption is airborne ash, explosions producing ash do not seem to be significant at this time. We have no evidence that ash has exceeded 10,000 ft asl and any ash produced is likely staying below 15,000 ft above sea level.



The current episode began at approximately 9:30 UTC (01:30 AKDT) on Tuesday, August 14 with an abrupt increase in seismic activity. Based on the patterns of unrest leading to past eruptions at Pavlof, AVO raised the alert level and color code to ADVISORY / YELLOW on Tuesday afternoon.



The rate of low frequency earthquakes steadily increased through Tuesday night. Strong thermal anomalies began to appear in AVHRR and GOES satellite data as early as 06:33UTC Wednesday, August 15 (22:33 AKDT Tuesday, August 14) and continued to be observed in all subsequent clear satellite views. AVO raised the alert level and color code to WATCH / ORANGE on Wednesday morning.



Mariners offshore to the east and south observed incandescent blocks of lava tumbling down the east-southeast slopes and fire fountaining on the southeast side of the summit during the predawn hours Wednesday morning. Pilots reported that Pavlof was emitting ash with a plume extending as far as 8 km (5 mi) south-southeast of the summit at an altitude of about 2.6 km (8400 ft) later on Wednesday morning. They also reported that the normally snow-covered volcano was now covered with ash.



Immediate hazards in the vicinity of the volcano include light ash fall on nearby communities, mudflows in drainages from the flanks of the volcano, and lava flows and avalanching of hot debris on the upper reaches of the volcano. At this time, we expect this eruption to follow the pattern of previous eruptions. The last eruption of Pavlof began in September, 1996 and consisted of a several-month-long series of ash explosions, lava-fountaining, and lava-flow production. Ash clouds reached as high as 30,000 ft ASL on one occasion. However, most ash clouds were below 20,000 ft ASL. Prior to 1996, Pavlof erupted in 1986 sending ash as high as 49,000 ft ASL on at least one occasion. A hazard assessment for Pavlof and the Emmons Lake volcanic center is available on the web at http://www.avo.alaska.edu/pdfs/SIR2006-5248.pdf



AVO continues to monitor the activity closely; satellite and seismic data are checked frequently around the clock. An AVO crew is enroute to Cold Bay to install additional monitoring equipment near the volcano.



Pavlof volcano is a steep-sided, symmetrical, 8261-ft-high stratovolcano located on the southwestern end of the Alaska Peninsula about 590 miles southwest of Anchorage. The community of Cold Bay is located 37 miles to the southwest of Pavlof; Nelson Lagoon, King Cove, and Sand Point are other communities within 75 miles of the volcano. With almost 40 historic eruptions, it is one of the most active volcanoes in the Aleutian arc. Eruptive activity is generally characterized by sporadic lava fountaining continuing for a several-month period. Additional hazards in the vicinity of the volcano included light ash fall on nearby communities, mudflows, lava flows and avalanching of hot debris on the flanks of the volcano. For more information on Pavlof and potential volcano hazards, please see our web site: http://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Pavlof



CLEVELAND VOLCANO (CAVW#1101-24-)

52°49'20" N169°56'42" W, Summit Elevation 5676 ft (1730 m)

Current Aviation Color Code: ORANGE

Current Volcano Alert Level: Watch



Clouds obscured satellite and webcam views of Cleveland all week. On Sunday, a commercial pilot observed that Cleveland was not steaming and showed no other signs of activity.



Photographs of a small burst of ash rising a few thousand feet above the summit of the volcano on July 20 (posted on the AVO web page http://www.avo.alaska.edu/) illustrate the kind of intermittent activity that is likely occurring. Based on previous historical eruptions of Cleveland, however, sudden explosions sending ash higher than 20,000 ft above sea level remain possible.



AVO continues to monitor the volcano closely with satellite imagery as weather allows. The lack of a real-time seismic network at Cleveland means that AVO is unable to track local earthquake activity related to volcanic unrest. Short-lived explosions of ash that could exceed 20,000 ft above sea level can occur without warning and may go undetected on satellite imagery.



Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 and had 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in October 2006.



KOROVIN VOLCANO (ATKA ISLAND) (CAVW#1101-16)

52°22'48" N174°9'22" W, Summit Elevation 5030 ft (1533 m)

Current Aviation Color Code: YELLOW

Current Volcano Alert Level: Advisory



Intermittent, low-level seismic activity continues at Korovin. Cloudy conditions prevented views of the volcano by satellite for most of the past week.



Korovin Volcano is a 1553-m-high (5030 ft) stratovolcano located on the northern part of Atka Island in the central Aleutian Islands, about 184 km (110 mi) east of Adak, 538 km (350 mi) west of Dutch Harbor, and 1760 km (1100 mi) southwest of Anchorage. The volcano has two distinct summit vents about 0.6 km (2000 ft) apart, that have been the sites of eruptive activity as recently as June, 1998. The most recently active of the vents maintains a small, roiling, lake that occasionally produces energetic steam emissions. Thermal springs and fumaroles located on and near the volcano indicate an active hydrothermal system. Korovin has erupted several times in the past 200 years, including 1907, 1951, 1953, 1954, 1973, 1976, 1986, 1987, 1996, and 1998. All of these eruptions produced minor amounts of ash and occasional but small lava flows. Reports of the height of the ash plume produced by the 1998 eruption ranged from 4900 to 9200 m (16,000 to 30,000 feet) above sea level.



OTHER ALASKA VOLCANOES



Seismic activity is monitored in real time at 31 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, Spurr, Redoubt, Iliamna, Augustine, Fourpeaked, Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Peulik, Ukinrek Maars, Aniakchak, Veniaminof, Dutton, Isanotski, Shishaldin, Fisher, Westdahl, Akutan, Makushin, Okmok, Great Sitkin, Kanaga, Tanaga, and Gareloi volcanoes are at Aviation Color Code GREEN and Volcano Alert Level NORMAL. 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.



Please see http://www.avo.alaska.edu/color_codes.php for complete definitions of Aviation color codes and volcano alert levels.



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



Steve McNutt, Coordinating Scientist, UAF

steve@giseis.alaska.edu (907) 474-7131



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].

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Page modified: May 27, 2014 10:23
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