Report on Chaiten (Chile) — 11 June-17 June 2008

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 June-17 June 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, 11 June-17 June 2008. Smithsonian Institution and US Geological Survey.

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42.833°S, 72.646°W; summit elev. 1122 m

All times are local (unless otherwise noted)

SERNAGEOMIN reported that visual observations of Chaitén were inhibited due to inclement weather during 10-12 June. Customs officers in the town of Chaitén reported noises on 11 June. They also reported the presence of two new craters to the S that emitted ash-and-gas plumes on 12 June. The plumes drifted S. Later that day in Chaitén town, an abrupt swelling of the river Chaitén was observed. Seismic events increased in number and intensity.

An overflight on 14 June revealed spines rising above the top of the new lava dome, which had grown in height to exceed the old dome. Gas, ash, and steam plumes were primarily emitted from a vent, about 100 m in diameter, at the SE contact between the old and the new lava dome. Previously, emissions came from the NW contact between the old and new domes. Continuous explosions produced ash plumes that rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted E. Several other points of gas-and-steam emissions were seen along the contact. Small block-and-ash flows from the new dome had descended the S flank of the old dome and occasionally reached the caldera floor. The Alert Level remained at Red.

Based on observations of satellite imagery, SIGMET reports, and pilot observations, the Buenos Aires VAAC reported that during 11-16 June ash plumes rose to altitudes of 2.1-3.7 km (7,000-12,000 ft) a.s.l. and drifted N, NE, 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.

Sources: Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Nacional de Geología y Minería (SERNAGEOMIN)