Printer friendly versionALASKA VOLCANO OBSERVATORY
Friday, September 23, 2005 11:30 AM AKDT (18:10 UTC)
56.2 ° W 159.39 ° N, Summit Elevation 8225 ft (2507 m)
Current Level of Concern Color Code: YELLOW
Cloudy weather this week prevented web camera and satellite observations of Veniaminof, but seismic data indicated diminishing activity. Some minor ash emissions may have occurred, with diffuse ash plumes rising less than 10,000 ft above sea level and remaining within the caldera. There are no indications that more vigorous activity is imminent or even likely. Even minor emissions can pose a hazard to people and low-flying aircraft in the vicinity of the active cone.
AVO will continue to monitor activity at Mount Veniaminof using seismic data, satellite images, internet camera data and observer reports.
Mount Veniaminof volcano is a young stratovolcano with an ice-filled 10-km (6 mi) diameter summit caldera located on the Alaska Peninsula, 775 km (480 mi) southwest of Anchorage and 35 km (22 mi) north of Perryville. Veniaminof is one of the largest and most active volcanic centers in the Aleutian Arc and has erupted at least 12 times in the past 200 years. The most recent significant eruption of the volcano occurred in 1993-95 and was characterized by intermittent, low-level emissions of steam and ash, and a small lava flow onto the summit caldera ice field producing an ice pit. Previous historical eruptions have produced ash plumes that reached 6,000 m (20,000 ft) above sea level and associated ash fall within about 40 km (25 mi) of the volcano. Minor ash emissions similar to those that occurred this week were also detected in early 2005.
61.3 ° W 152.25 ° N, Summit Elevation 11070 ft (3374 m)
Current Level of Concern Color Code: YELLOW
The level of seismic activity at Mt. Spurr volcano remains above background, but the overall rate of seismicity continues to gradually decline. Preliminary data from a gas sensing flight made earlier in the week show a substantial reduction in gas emissions compared to the last measurements, taken in May 2005. The declining seismicity, the reduced gas emissions, and the changing summit lake color -- thought to reflect lower levels of acidity -- all suggest a reduced level of activity at the volcano. Minor steaming continues from the summit melt pit and occasionally from Crater Peak. There are no indications that an eruption is imminent.
Mount Spurr volcano is an ice- and snow-covered stratovolcano located on the west side of Cook Inlet. The only known historical eruptions occurred in 1953 and 1992 from the Crater Peak flank vent located 3.5 km (2 mi) south of the summit of Mount Spurr. These eruptions were brief, explosive, and produced columns of ash that rose up to 20 km (65,000 ft) above sea level and deposited several mm of ash in south-central Alaska, including approximately 6 mm of ash on Anchorage in 1953. The last known eruption from the summit of Mount Spurr was more than 5,000 years ago. Primary hazards during future eruptions include far-traveled ash clouds, ash fall, pyroclastic flows, and lahars or mudflows that could inundate drainages all sides of the volcano, but primarily on the south and east flanks.
OTHER ALASKA VOLCANOES
Seismic activity is monitored in real time at 28 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, Redoubt, Iliamna, Augustine, Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Peulik, Aniakchak, Pavlof, Dutton, Isanotski, Shishaldin, Fisher, Westdahl, Akutan, Makushin, Okmok, Great Sitkin, Kanaga, Tanaga, and Gareloi volcanoes are in color code GREEN. 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.
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
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, Acting Coordinating Scientist, UAF-GI
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.