Report on Chaiten (Chile) — 25 February-3 March 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 February-3 March 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Chaiten (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 February-3 March 2009. Smithsonian Institution and US Geological Survey.
42.833°S, 72.646°W; summit elev. 1122 m
All times are local (unless otherwise noted)
On 24 February, SERNAGEOMIN reported that an overflight of Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex revealed that a large amount of material from the 19 February partial dome collapse had accumulated in the basal ring depression surrounding the dome complex and throughout the Chaitén (Blanco) River valley. Most of the collapsed material originated from Domo Nuevo 1. Steam plumes with little ash content rose from the N part of Domo Nuevo 2 and steam and brown ash plumes were emitted from a central spine complex. Steam plumes and sporadic explosions were noted from the S part of Domo Nuevo 1; producing four plumes that mixed and rose 1.5 km above the complex. Small collapses, originating from unstable slopes of the SE part of Domo Nuevo 1, generated block-and-ash flows.
On 26 February, observers in Chaitén town (10 km SW) reported that plumes rose 2 km above the complex. During 26-27 February, small collapses caused the plume to occasionally enlarge and turn brown. On 27 February, an overflight revealed that the S part of Domo Nuevo 1 continued to grow. Numerous fan-shaped deposits from collapses were seen on the S slope. Based on web camera views, the Buenos Aires VAAC reported that during 27 February, and 2-3 March plumes rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. Plumes drifted E on 27 February and SE on 3 March.
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.