Based on observations of satellite imagery, pilot reports, SIGMET notices, and web camera views, the Buenos Aires VAAC reported that during 3-8 December, ash plumes from Chaitén rose to altitudes 1.8-4.6 km (6,000-15,000 ft) a.s.l. and drifted NE, NW, and SW. A thermal anomaly was detected on satellite imagery during 4 and 6-8 December.

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.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)