Report on Fourpeaked (United States) — 27 September-3 October 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 27 September-3 October 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Fourpeaked (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 27 September-3 October 2006. Smithsonian Institution and US Geological Survey.
58.77°N, 153.672°W; summit elev. 2105 m
All times are local (unless otherwise noted)
Volcanic unrest continued at Fourpeaked volcano during 23-29 September. Satellite observations by scientists from the University of Maryland-Baltimore County indicate that sulfur dioxide emission was continuing. Early in the week, AVO conducted several helicopter and fixed-wing missions during which observers photographed a linear series of vents running N from the summit for about 1 km. Some of the vents were vigorously emitting steam and other volcanic gases. Thermal measurements of up to 75°C were recorded at the vents, although steam was likely obscuring hotter areas. Adjacent glacial ice had been disrupted and showed signs of subsidence. Airborne gas measurements taken on 23, 24, and 30 September documented high emission rates of sulfur dioxide, hydrogren sulfide, and carbon dioxide, and a distinct sulfur smell was evident up to 50 km from the summit. An AVO status report on 3 October noted that cloudy conditions had prevented visual or satellite observations, but limited seismic data now being received did not indicate significant volcanic activity.
Geologic Background. Poorly known Fourpeaked volcano in NE Katmai National Park consists of isolated outcrops surrounded by the Fourpeaked Glacier, which descends eastward almost to the Shelikof Strait. The orientation of andesitic lava flows and extensive hydrothermal alteration of rocks near the present 2105-m-high summit suggest that it probably marks the vent of Fourpeaked volcano. Eruptive activity during the Holocene had not been confirmed prior to the first historical eruption of Fourpeaked in September 2006. A N-trending fissure extending 1 km from the summit produced minor ashfall.