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Beginning on October 22, AVO received multiple reports of increased steaming, snow-melt, and sulfur smell at Chiginagak Volcano, a 2135-m-tall, snow- and ice-covered symmetric stratovolcano located 175 km south of King Salmon on the Alaska Peninsula. Robust steam plumes have issued from an active fumarole at an elevation of about 1676m on the north flank of the volcano since at least the early 1970's and sulfur deposition in the vicinity of the fumarole discolors the adjacent snow and ice. Although no reports of historic eruptions at Chiginagak are well documented, the volcano is surrounded by extensive young pyroclastic deposits and lava flows.
Yesterday, AVO dispatched an observation flight to Chiginagak. Observers reported an enlarged area of fumarolic activity, including new fumaroles at about 1890 m, directly above the previously known site. There was no sign of recently erupted ash or mud flows. Residents of the area, including the community of Pilot Point 60 km northwest of the volcano, reported noticing an increase in steam emission as early as mid (?) summer, 1997.
Accompanying the increased steaming of the last 10 days, a possible new thermal anomaly at the volcano has also been noted on AVHRR satellite imagery as recently as 10/30/97.
This change in fumarolic activity at Chiginagak may reflect an increased heat flux at the volcano. Chiginagak is unmonitored by seismic instrumentation, however, AVO is keeping a close watch on the volcano with satellite imagery. Additional overflights may occur if the activity persists or intensifies. The volcano is located on National Wildlife Refuge land managed by the USFWS. AVO is also in contact with USFWS staff who frequently overfly the area.
Seismic activity is monitored in real time at 14 volcanoes in Alaska. Some of these volcanoes may currently display anomalous seismicity, but they are not considered to be at a dangerous level of unrest.
Spurr, Redoubt, Iliamna, Augustine, Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Pavlof, Dutton, Akutan, and Makushin volcanoes are all at or near normal levels of background seismicity.