Jeff Witter climbed Villarrica on 17 November and observed summit-crater activity for about an hour. The circular main crater, ~ 200 m in diameter and 100 m deep, had vertical sides and a flat floor covered by black spatter. Gas flux was vigorous and continuous from an incandescent pit, 5 m in diameter, ~ 20 m E of the center of the crater. At intervals of ~5-10 minutes, roughly 2 m³ of spatter were ejected from the pit to 15 m height. Sounds similar to ocean waves also emanated from the pit. After about 30 minutes of observations, a 2 m² section of the crater floor collapsed, enlarging the pit. Five more glowing pits, none more than 0.5 m across, were visible along the E edge of the crater floor. No tephra was found on the surface of snow and ice in the summit area, although convection carried small scoria fragments to as much as 130 m above the crater floor.

Moderate fumarolic activity occurred from a 20 x 10 m area on the SW rim, and from a 10-m vent ~ 5 m N of the main crater rim. Gases were strong-smelling and caused a burning sensation in the eyes, nose, and lungs. Fumarolic activity appeared stronger the next day, when observations from the entrance to Villarrica National Park (~ 7 km away) revealed a white billowing vapor cloud enveloping the entire summit area.

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.

Information Contacts: G. Fuentealba, Univ de la Frontera; J. Witter, Occidental College, Los Angeles.