SERNAGEOMIN reported that seismicity from Chaitén increased during 9-12 January. The unstable slopes of Domo Nuevo 2 and spine collapses continued to produce block-and-ash flows. Based on SIGMET notices, analysis of satellite imagery, and web camera views, the Buenos Aires VAAC reported that on 15, 17, 19, and 20 January ash plumes rose to altitudes 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted NE, E, and SE. A small thermal anomaly was detected in satellite imagery on 19 January.

Geological Summary. Chaitén is a small caldera (~3 km in diameter) located 10 km NE of the town of Chaitén on the Gulf of Corcovado. Multiple explosive eruptions throughout the Holocene have been identified. 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 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 recorded eruption, beginning in 2008, produced major rhyolitic explosive activity and building a new dome and tephra cone on the older rhyolite dome.

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