SERNAGEOMIN reported that during 28 February-3 March Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex continued to grow. Collapses, originating from unstable slopes of the SE part of Domo Nuevo 1 and from a central spine complex, generated block-and-ash flows. Material from the collapses accumulated in the basal ring depression surrounding the dome complex and throughout the Chaitén (Blanco) River valley. Ash-and-gas plumes drifted mainly SE. Data collected during an overflight on 3 March revealed that temperatures of deposited material in the Chaitén River valley remained elevated. A steam-and-ash plume rose 1 km above the domes and drifted S.

Based on web camera views and analysis of satellite imagery, the Buenos Aires VAAC reported that during 3 and 5-9 March ash plumes rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted SE, E, and NE.

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