Printer friendly versionALASKA VOLCANO OBSERVATORY
Tuesday, November 29, 2005 12:15 PM AKST (2115 UTC)
59.3633°N 153.4333°W, Summit Elevation 4134 ft (1260 m)
Current Level of Concern Color Code: YELLOW
Previous Level of Concern Color Code: GREEN
AVO has detected important changes in earthquake activity and ground deformation at Augustine Volcano in southern Cook Inlet. These data are consistent with renewed volcanic unrest. AVO is therefore raising the level-of-concern color code from green to YELLOW and will continue to monitor activity closely. There is no indication that an eruption is imminent or certain.
Beginning in May 2005, there has been a slow increase in the number of earthquakes located under Augustine Volcano. The earthquakes are generally small (less than magnitude 1.0) and concentrate roughly 1 km below the volcano's summit. These earthquakes have slowly increased from 4-8 earthquakes/day to 20-35 earthquakes/day. Additionally, data from a 6-station Global Positioning System (GPS) network on Augustine Volcano indicate that a slow, steady inflation of the volcano started in mid-summer 2005 and continues at present. The GPS benchmark located nearest the summit has moved a total of 2.5 cm (1 inch). This motion is consistent with a source of inflation or pressure change centered under the volcano. This is the first such deformation detected at Augustine Volcano since measurements began just prior to the 1986 eruption.
No reports of increased steaming have been received by AVO, nor have satellite data shown increased thermal activity.
Historic eruptions of Augustine typically begin with explosive bursts that may send plumes of ash to 30,000-40,000 feet above sea level. The primary hazards to communities, aviation, and mariners in Cook Inlet and parts of south-central Alaska from an Augustine eruption are ash fall and drifting ash clouds. In 1986, 6 mm (0.25 inch) of ash fell in Homer, 120 km (75 mi) east of Augustine and light ashfall was recorded in Anchorage, 290 km (180 mi) away. Hot, ground-hugging flows of volcanic rock debris called pyroclastic flows may form during an eruption and could be hazardous to people, aircraft, or boats on or in the immediate vicinity of the island.
Island volcanoes can generate tsunamis by collapse into the sea. There is no evidence that conditions are developing that would lead to a major volcanic landslide or similar event at Augustine that, upon entering Cook Inlet, could generate a tsunami. No tsunami waves were generated during any of the last five eruptions of Augustine Volcano.
The full hazard assessment for Augustine Volcano can be obtained at http://www.avo.alaska.edu/pdfs/augustine_ofr.pdf
Augustine Volcano is a 1260 m high (4134 ft) conical-shaped stratovolcano located on Augustine Island in southern Cook Inlet, about 290 km (180 mi) southwest of Anchorage, Alaska. Augustine is the most historically active volcano in the Cook Inlet region. Historical eruptions occurred in 1812, 1883, 1908, 1935, 1963-64, 1976, and 1986. These eruptions were primarily explosive events that produced volcanic ash clouds and pyroclasic flows. During the 1883 eruption, a volcanic rock avalanche occurred on the north flank of the volcano; it flowed into Cook Inlet and initiated a tsunami observed at Nanwalek, about 90 km to the east.
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.