Based on seismicity during 14-16 and 18-20 September, OVDAS-SERNAGEOMIN reported that the eruption from the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, continued at a low level. Although cloudy weather mostly prevented observations of the vent, a plume was observed in satellite imagery drifting 60 km E on 14 September, and the next day, a plume observed by an area camera rose 4 km above the crater and drifted SE. Plumes observed in satellite imagery drifted 40-70 km N and NW during 18-20 September. Plumes observed during 19-20 September by an area camera rose 3-4 km above the crater. According to a news article, on 17 September the first commercial plane landed at the airport in Bariloche, about 60 km SE, since the airport had closed on 4 June. Private planes had been occasionally using the airport since mid-July. The Alert Level remained at Red.

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: Agence France-Presse (AFP), Servicio Nacional de Geología y Minería (SERNAGEOMIN)