Report on Chaiten (Chile) — 13 August-19 August 2008

Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 August-19 August 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, 13 August-19 August 2008. Smithsonian Institution and US Geological Survey.

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Chaiten

Chile

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

All times are local (unless otherwise noted)


SERNAGEOMIN reported that continuous emissions of gas-and-ash plumes from Chaitén were observed on 13 August, after three days of bad weather prevented visual observations. Plumes rose to an altitude of 2 km (6,600 ft) a.s.l., but later that day rose to greater altitudes of 6-7 km (19,700-23,000 ft) a.s.l. The increased activity did not correspond to any significant variation in seismicity. Plumes were emitted from two areas on the E and S flanks and were different colors; the area on the E flank produced steam plumes with minor ash content and the area on the S flank emitted darker ash plumes. The plumes drifted SW and caused ashfall in Chaitén town for several hours. The ash accumulation was 1.5 cm thick.

Based on web camera views, SIGMET reports, analysis of satellite imagery, and information from the Puerto Montt Flight Information Region (FIR), the Buenos Aires VAAC reported that during 16 and 18-19 August ash plumes rose to altitudes of 1.4-2.4 km (4,500-8,000 ft) a.s.l. and drifted NE, E, and SE.

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