On 25 October SERNAGEOMIN reported that activity at Villarrica had been gradually increasing. Both the number and amplitude of long-period earthquakes increased during the month, and further increased the last week. Continuous tremor increased slightly. Webcams showed persistent gas emissions rising 460 m above the crater rim, and ash plumes drifting downwind on 2 and 23 October. Sulfur dioxide emissions averaged 535 (plus or minus 115) tonnes per day, peaking at 1,273 tonnes per day on 13 October. These values were within normal levels and were lower than in September. Crater incandescence increased in both frequency and intensity, consistent with reports from POVI and other collaborators, and likely indicated periodic Strombolian activity. On 14 October satellite images showed the active lava lake covering an area of 36 square meters in the E part of the crater floor. A partial collapse (less than 300 square meters) of the inner SSW crater rim was also evident.

POVI reported that lava fountaining and Strombolian explosions were visible in webcam images at 1917 on 18 October. The most intense thermal anomaly over the crater since September 2019 was detected in satellite images on 23 October, and crater incandescence was visible in webcam images. That same day tourists described seeing splashes of lava ejected from a depth of 80 m and hearing loud degassing sounds. Deposits of ejected tephra were visible around the crater rim and on the upper flanks on 24 October, and intense crater incandescence was visible in images on 25 October. The Alert Level remained at Green, the lowest level on a four-color scale.

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), Proyecto Observación Villarrica Internet (POVI)