Based on analyses of satellite images, the Buenos Aires VAAC reported that on 16 January steam-and-gas emissions with minor amounts of ash rose from the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, to an altitude of 2.4 km (8,000 ft) a.s.l. The plume quickly dissipated. The Alert Level remained at Green (lowest on a four-color scale).

Geological Summary. The Puyehue-Cordón Caulle volcanic complex (PCCVC) is a large NW-SE-trending late-Pleistocene to Holocene basaltic-to-rhyolitic transverse volcanic chain SE of Lago Ranco. The 1799-m-high Pleistocene Cordillera Nevada caldera lies at the NW end, separated from Puyehue stratovolcano at the SE end by the Cordón Caulle fissure complex. The Pleistocene Mencheca volcano with Holocene flank cones lies NE of Puyehue. The basaltic-to-rhyolitic Puyehue volcano is the most geochemically diverse of the PCCVC. The flat-topped, 2236-m-high volcano was constructed above a 5-km-wide caldera and is capped by a 2.4-km-wide Holocene summit caldera. Lava flows and domes of mostly rhyolitic composition are found on the E flank. Historical eruptions originally attributed to Puyehue, including major eruptions in 1921-22 and 1960, are now known to be from the Cordón Caulle rift zone. The Cordón Caulle geothermal area, occupying a 6 x 13 km wide volcano-tectonic depression, is the largest active geothermal area of the southern Andes volcanic zone.

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