Report on Chaiten (Chile) — 1 October-7 October 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 October-7 October 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Chaiten (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 October-7 October 2008. Smithsonian Institution and US Geological Survey.
42.833°S, 72.646°W; summit elev. 1122 m
All times are local (unless otherwise noted)
SERNAGEOMIN reported that during 23-25 September, Chaitén continued to produce two vigorous gas-and-ash plumes from separate locations on the lava dome that rose to an altitude of 2.6 km (8,500 ft) a.s.l. During 27-28 September, activity increased and the two plumes rose to an altitude of 5.1 km (16,700 ft) a.s.l. Later in the day on 28 September, the plumes rose to an altitude of 4.1 km (13,500 ft) a.s.l. During an overflight on 30 September, scientists observed the small lagoon that remained in a depression in the N area of the basal "ring" that lies between the new lava dome and the caldera rim. The base of the S flank of the old lava dome was still evident; fumaroles were noted along the contact of the old and new domes. The new lava dome had grown higher and laterally from the NE flank until it touched the caldera rim. The Alert level remained Red.
Based on pilot observations, analysis of satellite imagery, and SIGMET reports, the Buenos Aires VAAC reported that during 3 and 5-8 October continuous ash plumes rose to altitudes of 2.4-3.5 km (8,000-11,500 ft) a.s.l. and drifted NE, ENE, and E.
Geologic Background. Chaitén is a small, glacier-free caldera with a compound Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. Early work had identified only a single explosive eruption during the early Holocene prior to the major 2008 eruption, but later work has identified multiple explosive eruptions throughout the Holocene. A rhyolitic obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km from the volcano to the N and S. The caldera is breached on the SW side by a river that drains to the bay of Chaitén. The first historical eruption, beginning in 2008, produced major rhyolitic explosive activity and growth of a lava dome that filled much of the caldera.