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Archived Report
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ALASKA VOLCANO OBSERVATORY

Weekly Update

Friday, August 24, 2007 11:40 AM AKDT (1940 UTC)






PAVLOF VOLCANO (CAVW#1102-03-)

5524'57" N16153'24" W, Summit Elevation 8261 ft (2518 m)

Current Aviation Color Code: ORANGE

Current Volcano Alert Level: Watch



Activity at Pavlof has continued to increase throughout the week and we have reports that the steam and ash plume is now exceeding 10,000 ft above sea level (asl). A pilot reported the top of the plume to be 18,000 ft (5500 m) late Thursday afternoon. A height of 13,000 ft (4000 m) was calculated using satellite data from 2210 UTC (14:10 AKDT) yesterday. However, at 0430 UTC August 24 (18:30 AKDT August 23) another pilot reported that the plume was only "a couple thousand feet" above the summit (or approximately 10,000 ft [3000 m] asl) AVO believes that plumes exceeding this height, and perhaps reaching as high as 20,000 ft (6100 m), are likely, but not certain, to occur in the coming days to weeks.



Seismic activity has remained elevated all week at Pavlof, with moderate levels of tremor occurring almost continuously and with occasional bursts of higher amplitude. The average seismic amplitude has increased slowly throughout the week. Many small to moderate explosions have been recorded in the seismic record; lahars flowing down Pavlof's southeast flank have also been recorded. Satellite data showed strong thermal anomalies at the summit throughout the week as well as occasional ash clouds.



An AVO field crew visited Pavlof August 18 - 19. The crew performed instrument maintenance and made visual and FLIR (thermal) observations of the ongoing eruption. The FLIR confirmed the existence of a new vent about 200 m (650 ft) below the summit on the southeast flank of the volcano. The vent is approximately 50 m (160 ft) across and is feeding a lava flow that, at the time of the observation (August 18), was more than 0.5 km (0.3 mi) long and about 25 m (80 ft) across. The crew also observed a lahar reaching the Pacific coast, incandescent lava, and explosions at the vent that sent 5 m (15 ft) long blocks flying 50 m (150 ft) through the air.



The current episode began at approximately 9:30 UTC (01:30 AKDT) on August 14 with an abrupt increase in seismic activity; AVO raised the alert level and color code to ADVISORY / YELLOW on the afternoon of August 14. Strong thermal anomalies began to appear in AVHRR and GOES satellite data as early as 06:33 UTC August 15 (22:33 AKDT August 14), leading AVO to raise the alert level and color code to WATCH / ORANGE on the morning of August 15.



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 3.5-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.



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-)

5249'20" N16956'42" W, Summit Elevation 5676 ft (1730 m)

Current Aviation Color Code: ORANGE

Current Volcano Alert Level: Watch



Satellite and webcam views were predominantly cloudy all week, though on several occasions thermal anomalies were seen.



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)

5222'48" N1749'22" W, Summit Elevation 5030 ft (1533 m)

Current Aviation Color Code: YELLOW

Current Volcano Alert Level: Advisory



An earthquake swarm, consisting of about 40 located events with a maximum magnitude of 1.2, occurred on August 19-20 about 5 km southeast of 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].
PDF version of these definitions
URL: avo.alaska.edu/activity/avoreport_archives.php
Page modified: June 11, 2012 11:50
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