Video from an 11 September overflight of Villarrica, conducted by the Carabineros Región de La Araucanía, showed an active cone on the crater floor. ONEMI and SERNAGEOMIN noted that the activity was consistent with the elevated seismicity detected by the seismic network during the previous few days. Seismicity and explosive activity in the crater both began decreasing on 12 September and continued a downward trend at least through 16 September. Discrete tremor signals disappeared during 15-16 September, with moderate levels of continuous tremor dominating the signal. No explosions were detected. SERNAGEOMIN lowered the Alert Level to Yellow, the second lowest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli, and changed the exclusion zone for the public to a radius of 1 km around the crater.

Geological Summary. The glacier-covered Villarrica stratovolcano, in the northern Lakes District of central Chile, is ~15 km south of the city of Pucon. A 2-km-wide caldera that formed about 3,500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesite cone at the NW margin of a 6-km-wide Pleistocene caldera. More than 30 scoria cones and fissure vents are present on the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Eruptions documented since 1558 CE have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI), Carabineros de Chile (Región de La Araucanía)