The 4-km-wide, glacier-filled Sollipulli caldera lies E of the Pleistocene Nevados de Sollipulli complex. Major silicic pyroclastic rocks associated with caldera formation have not been found; it may have a non-explosive origin. Post-caldera eruptions have been focused along the caldera walls and have increased its height. A series of dacitic lava domes lines the E and S caldera rims. The 1-km-wide Alpehué crater, which cuts the SW rim, was the source of a large Plinian eruption 2900 years before present (BP). Explosion craters and scoria cones are found on the outer flanks. Two N-flank cones produced lava flows during the latest documented activity about 700 years BP (Naranjo et al., 1993). This low-profile volcano is less prominent than its neighbors Llaima and Villarrica, but its explosive history makes it a potentially hazardous volcanic center.