SERNAGEOMIN reported that during 14-20 October a gas-and-ash plume from Chaitén rose to an altitude of 3.1 km (10,200 ft) a.s.l. The lava dome continued to grow, especially the E side. The Volcanic Alert level remained at Red. Based on web camera views, information from the Puerto Montt Flight Information Region (FIR), analysis of satellite imagery, and SIGMET reports, the Buenos Aires VAAC reported that during 14-18 and 21 October continuous ash plumes from Chaitén rose to altitudes of 2.1-4 km (7,000-13,000 ft) a.s.l. and drifted N, NE, and ESE.

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