Printer friendly versionALASKA VOLCANO OBSERVATORY
Wednesday, June 6, 2007 1:10 PM AKDT (2110 UTC)
58°46'9" N153°40'26" W, Summit Elevation 6903 ft (2104 m)
Current Aviation Color Code: GREEN
Current Volcano Alert Level: Normal
Previous Aviation Color Code: YELLOW
Previous Volcanic Activity Alert Level: Advisory
AVO is lowering the Aviation Color Code for Fourpeaked Volcano from YELLOW to GREEN and the Volcanic Activity Alert Level from ADVISORY to NORMAL based on declining rates of seismicity and gas emission. At this time, AVO sees no indication that a sudden eruption of Fourpeaked is likely. Local hazards still exist near the summit, including jetting steam and/or very small explosions, unstable snow and ice, hot water and rock, and the possibility for high concentrations of dangerous volcanic gas.
Following the initial unrest at Fourpeaked, AVO installed a telemetered, geophysical monitoring network, consisting of three short-period seismometers, two co-located pressure sensors, and a web camera. These new instruments augment a pre-existing regional network that includes two seismometers within 60 km of Fourpeaked. The network operated successfully through the winter, and continues to record seismic activity; AVO has located nearly 400 earthquakes since installing the Fourpeaked seismic network. Most of these events occurred between November 2006 and February 2007. AVO located 33 earthquakes in March 2007, 20 in April, and 7 in May.
AVO has flown 7 gas monitoring flights since September 2006. Initial measurements showed high rates (1000s of tons/day) of SO2 emission. Subsequent flights showed declining emission rates, with the most recent measurement, taken in mid-May 2007, yeilding only about 50 tons/day of SO2.
In late September 2006, AVO presented a short list of scenarios describing possible future eruptive activity at Fourpeaked. At that time, AVO ranked a small to moderate eruption as the most likely scenario, with the possibility of no eruption occurring being only slightly less probable. A large eruption was not ruled out, but was considered much less likely than the other two scenarios. Based on the declining rates of seismicity and gas emission, and on the eight months that have elapsed without eruptive activity, AVO now considers the most likely scenario to be a gradual return to quiescence. If the current trend at Fourpeaked reverses toward an increasing likelihood of eruption, geophysical instrumentation would likely detect marked precursory activity.
Fourpeaked volcano lies within the northeast corner of Katmai National Park and Preserve on the Alaska Peninsula, 7.5 miles (12 km) southwest of Mount Douglas. It is a stratovolcano that is mostly covered by Fourpeaked Glacier. Small isolated volcanic exposures along ridge crests and cliff faces radiate out from the ice-covered summit. The last major eruption at Fourpeaked was probably more than 10,000 years ago. If there have been eruptions within the last 10,000 years, they were small enough that they did not leave recognizable deposits. There is no record of eruptions within the past few hundred years. Local residents report that steaming similar to the recent activity may have occurred several decades ago.
NORMAL Typical background activity of a volcano in a non-eruptive state
ADVISORY Elevated unrest above known background activity
WATCH Volcano is exhibiting heightened or escalating unrest with increased potential for eruptive activity
WARNING Highly hazardous eruption underway or imminent
ABBREVIATED AVIATION COLOR CODE KEY:
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
Please see http://volcanoes.usgs.gov/2006/vhpalertlevel.pdf for a complete description of alert levels and color codes.
VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478
John Power, Acting Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Jessica Larsen, Acting Coordinating Scientist, UAF
email@example.com (907) 322-4085
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.