SERNAGEOMIN reported that during 16 December 2009-4 January 2010 steam-and-gas plumes from Chaitén's lava-dome complex seen on the web camera during periods of clear weather rose 1.5 km above the lava domes. Seismicity, along with occasional block-and-ash flows, indicated that the lava domes continued to grow. Based on web camera views and analyses of satellite imagery, the Buenos Aires VAAC reported that on 6 January a plume drifted 50 km ENE at an altitude of 2.1 km (7,000 ft) a.s.l. The next day an ash plume drifted SE and E at the same altitude.

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)