Printer friendly versionALASKA VOLCANO OBSERVATORY
Friday, August 26, 2005 1:30 PM AKDT (21:30 UTC)
MOUNT SPURR VOLCANO (CAVW#1103-04)
61°18'N 152°15'W, Summit Elevation 11,070 ft. (3,374 m)
Current Level of Concern Color Code: YELLOW
The level of seismic activity at Mt. Spurr volcano remains above background, similar to the levels of the past several weeks. Minor steaming continues from the summit melt pit and occasionally from Crater Peak. The volcano was visible intermittently throughout the week. No unusual activity was observed. 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 on all sides of the volcano, but primarily on the south and east flanks.
CLEVELAND VOLCANO (CAVW #1101-24)
52°49’N 169°57’W, Summit Elevation 5,674 ft (1,730 m)
Current Level of Concern Color Code: YELLOW
Clouds obscured views of the volcano during much of the week. However, when the volcano was visible, no thermal anomalies were detected. Low-level unrest may still be occurring, but is likely waning in intensity.
Based on historical eruptions at Cleveland, it is possible that explosive, ash-producing events could occur at any time and without warning (due to the lack of seismic monitoring). AVO will continue to monitor the volcano using satellite images and pilot reports.
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 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.
CHIGINAGAK VOLCANO (CAVW #1102-11)
57°8.1’N 156°59.4’W, Summit Elevation 7,005 ft (2,135 m)
Current Level of Concern Color Code: Not Assigned
An AVO field crew reported that a 1,300 ft (400 m) wide melt-water lake has formed in the snow and ice filled summit crater at Chiginagak Volcano sometime since the last observations in August 2004. Earlier this summer, the southern crater rim of Chiginagak was breached, allowing a portion of the lake to drain. The resulting flow caused flooding at Indecision Creek, Volcano Creek, Mother Goose Lake, and an unnamed Pacific drainage leading to Chiginagak Bay. The flow likely contained acidic water. Vegetation damage was observed along Indecision Creek and the unnamed Pacific drainage.
AVO geologists continue to investigate the event and its impacts. There are no indications that an eruption is imminent or that this event is necessarily precursory to an eruption. Chiginagak Volcano is not seismically monitored. The nearest seismic networks are at Aniakchak and Ugashik-Peulik Volcanoes, both about 50 miles (80 km) away. It is AVO policy not to assign a color code of Green to a volcano without a real-time seismic network.
Chiginagak is a symmetric stratovolcano located 175 km (110 mi) south of King Salmon on the Alaska Peninsula. The nearest settlement is Pilot Point, 60 km (37 mi) to the northwest. The high flanks of the volcano are snow-and ice-covered, and a prominent fumarole located high on the north flank at about 5,500 ft (~1,675 m) constantly emits steam and sulfur gases. Historical eruptive activity has been minor and is poorly documented, however, the volcano is surrounded by pyroclastic deposits and lava flows that are likely less than a few thousand years old
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, Veniaminof, 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.