SERNAGEOMIN reported that during 23-26 June visual observations of Chaitén were inhibited due to inclement weather. Based on web camera views, SIGMET reports, observations of satellite imagery, pilot reports, and information from the Puerto Montt Flight Information Region (FIR), the Buenos Aires VAAC reported continuous ash emissions on 25 June. They further reported ash plumes at altitudes of 0.6-4.6 km (2,000-15,000 ft) a.s.l. during 30 June-1 July. Ash plumes drifted NE and NNW on 30 June, and NNE on 1 July.

Geological Summary. 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)