Printer friendly versionALASKA VOLCANO OBSERVATORY
Friday, September 14, 2007 12:25 PM AKDT (2025 UTC)
55°24'57" N161°53'24" W, Summit Elevation 8261 ft (2518 m)
Current Aviation Color Code: ORANGE
Current Volcano Alert Level: Watch
The eruption of Pavlof Volcano that began August 15th continues. Seismicity this week has declined markedly from levels recorded last week, but volcanic tremor and small explosions are still being recorded. Although it has been mostly cloudy this week, satellite observations through the clouds on several days, showed a thermal anomaly from continued lava production. Steam plumes were observed by satellite on two occasions, one up to ~20,000 feet above sea level, and a pilot reported a steam and weak ash plume drifting from the summit area on one occasion this week. The decrease in seismicity may be only a lull in the current eruption. Typical eruptions at Pavlof are characterized by periods of dimished activity interspersed with the periods of renewed eruptive activity. Renewed activity could begin at any time with little seismic warning.
If activity should increase in intensity, larger ash clouds that could affect higher-flying aircraft may be produced. The most immediate ground hazard in the vicinity of the volcano includes light ash fall on nearby communities. Previous historical eruptions from Pavlof caused only a few millimeters (about 1/10th of an inch) of ash to fall on King Cove, Nelson Lagoon, Cold Bay, and Sand Point. Mudflows in drainages from the flanks of the volcano, and lava flows and avalanching of hot debris on the upper reaches of the volcano are also of concern in the uninhabited areas around the volcano. Satellite and seismic data and eyewitness observations suggest most of the surface lava activity is occurring on the southeast sector of the steep-sided volcano; this suggests that the Pacific Ocean side of the volcano is at most risk from avalanching hot debris.
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
Pavlof volcano is located on the southwestern end of the Alaska Peninsula. Pavlof is a stratovolcano which rises to an elevation of 8262 feet. With almost 40 historic eruptions, it is one of the most consistently active volcanos in the Aleutian arc. Eruptive activity is generally characterized by sporadic strombolian fountaining continuing for a several-month period. The community of Cold Bay is located 60 km (37 miles) to the southwest of Pavlof.
52°49'20" N169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Aviation Color Code: YELLOW
Current Volcano Alert Level: Advisory
Clouds obscured views of the volcano by satellite and web camera most of the week. A partly clear satellite image from last night showed steaming and new snow at the summit of Cleveland. The temperature of the thermal anomaly in the crater has decreased. These data are consistent with our decision to decrease the aviation color code to yellow last week.
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.
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, Korovin, 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
Tom Murray, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Steve McNutt, Coordinating Scientist, UAF
email@example.com (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.