Printer friendly versionALASKA VOLCANO OBSERVATORY
Friday, October 7, 2005 1:20 PM AKDT (2120 UTC)
51.885°N 178.1458°W, Summit Elevation 5925 ft (1806 m)
Current Level of Concern Color Code: YELLOW
Previous Level of Concern Color Code: Green
The earthquake swarm that began at Tanaga Volcano on October 1 has increased over the past 32 hours. Marked increases in the rate of earthquake occurrence took place late on October 5 and then again at roughly 5:00 AM AKDT today. The located earthquakes range in magnitude from 0.5 to 1.9 and now range in depth from 6 to 12 km beneath the volcano’s summit. These locations represent both an increase in magnitude and a shallowing in depth compared with events recorded at Tanaga between October 1 and 5. In response to the observed changes in seismic activity the Alaska Volcano Observatory (AVO) is increasing the level of concern color code to Yellow. While the current rate of earthquake activity represents a significant increase in rate, the size, depths and character of the shocks are not indicative of imminent eruptive activity. AVO will continue to monitor the activity at Tanaga closely.
Tanaga is a remote, 1,806 m (5,925 ft)-high stratovolcano located on the northwest portion of Tanaga Island, roughly 105 km (63 miles) west of Adak in the Andreanof Islands. The last known eruption of Tanaga occurred in 1914 and earlier eruptions were reported in 1763-1770, 1791, and 1829. Reports of these eruptions are vague, but deposits on the flanks of the volcano show that typical eruptions produce blocky lava flows and occasional ash clouds. Eruptions have occurred both from the summit vent and a 1,584 m (5,197 ft)-high satellite vent on the volcano's northeast flank.
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.