Based on web camera views and analyses of satellite imagery, the Buenos Aires VAAC reported that on 14 October an ash plume from Chaitén's lava-dome complex rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 150 km NNE. A diffuse plume was seen the next day drifting 15 km SW at the same altitude as the previous day. During 15-16 October, a thermal anomaly was seen. On 18 October, a possible plume drifted 50 km SE at an altitude of 2.1 km (7,000 ft) a.s.l. Diffuse ash plumes possibly mixed with steam and gas rose to an altitude of 1.8 km (6,000 ft) a.s.l. on 20 October and drifted NE and SE.

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.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)