Printer friendly versionALASKA VOLCANO OBSERVATORY
Friday, November 25, 2005 12:20 PM AKST (2120 UTC)
61.2994°N 152.2511°W, Summit Elevation 11070 ft (3374 m)
Current Level of Concern Color Code: YELLOW
The level of seismic activity at Mount Spurr volcano remains above background. Satellite and web camera views of the volcano showed nothing unusual during the past week. 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 approximately 120 km (75 mi) west of Anchorage. 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.
52.8232°N 169.9431°W, Summit Elevation 5676 ft (1730 m)
Current Level of Concern Color Code: Not Assigned
Activity at Cleveland Volcano in the east central Aleutians appears to have diminished. Clear satellite views this morning show no thermal anomaly. AVO has not detected a temperature anomaly in the vicinity of the volcano since November 6. Following the brief ash burst on October 7, no further ash emissions have been noted. Based on this trend, the likelihood of significant ash-producing events has decreased, and AVO is terminating Level of Concern Color Code YELLOW. Cleveland Volcano is not monitored with seismic instrumentation, therefore we do not assign Color Code GREEN. This will be the last mention of Cleveland in our weekly update unless activity at the volcano changes.
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 July 2005.
56.1956°N 159.3883°W, Summit Elevation 8225 ft (2507 m)
Current Level of Concern Color Code: YELLOW
Seismicity at Veniaminof remains low. Very small steam and ash bursts were last seen on November 20. It is possible that this activity has continued but gone unnoticed due to cloudy conditions. These steam and ash emissions may continue intermittently and they do pose a hazard to people and low-flying aircraft in the vicinity of the active cone. However, seismic data do not indicate that larger eruptions are imminent.
Mount Veniaminof volcano is an andesitic stratovolcano with an ice-filled 10-km 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 (~ 300 km3) and most active volcanic centers in the Aleutian Arc and has erupted at least 13 times in the past 200 years. Recent significant eruptions of the volcano occurred in 1993-95 and 2005. Both were moderate Strombolian eruptions producing intermittent low-level jets of incandescent lava fragments, and low-level emissions of steam and ash from the main intracaldera cone. During the 1993-95 activity, a small lava flow was extruded into the summit caldera ice field producing an ice pit. Minor ash-producing explosions occurred in 2002, 2004, early 2005, and in recent weeks. Previous historical eruptions have produced ash plumes that reached 6,000 m (20,000 ft) above sea level and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano.
51.885°N 178.1458°W, Summit Elevation 5925 ft (1806 m)
Current Level of Concern Color Code: GREEN
Over the past several weeks, seismic activity beneath young volcanic vents on Tanaga Island has decreased significantly from levels seen in early October. Satellite views of the island have shown no anomalous temperatures or evidence of ash emission. Based on the decay of earthquake counts and frequency of tremor episodes, the likelihood of an eruption has diminished. Therefore, AVO is downgrading the Level of Concern Color Code to GREEN. This will be the last mention of Tanaga in our weekly update unless activity at the volcano changes.
Tanaga Island lies in the Andreanof Islands approximately 100 km (62 miles) west of the community of Adak and 2025 km (1260 miles) SW of Anchorage. The northern half of the island is home to the Tanaga volcanic complex, comprising three main volcanic edifices. Historically active Tanaga volcano is the tallest of these (1,806 m or 5,925 ft) and lies in the center of the complex. Immediately west of Tanaga volcano lies Sajaka, a 1,354 m (4,443 ft)-high compound edifice with an older cone to the east that collapsed into the sea within the last few thousand years, and a new cone that has grown in the breach. The new cone is 1,312 m (4,305 ft) high and consists of steeply dipping, interbedded cinders and thin, spatter-fed lava flows. To the east of Tanaga lies Takawangha, which is separated from the other active volcanic vents by a ridge of older rock. Takawangha's 1,449 m (4,754 ft)-high summit is mostly ice-covered, except for four young craters that have erupted ash and lava flows in the last few thousand years. Parts of Takawangha's edifice are hydrothermally altered and may be unstable, and could produce localized debris avalanches. No historical eruptions are known from Sajaka or Takawangha; however, field work shows that recent eruptions have occurred and it is possible that historic eruptions attributed only to Tanaga may instead have come from these other vents.
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
John Eichelberger, Coordinating Scientist, UAF-GI
email@example.com (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.