Villarrica is one of Chile's most active volcanoes, rising above the lake and town of the same name. The volcano is also known as Rucapillán, a Mapuche word meaning "House of the Pillán". It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain along the Gastre Fault. Villarrica, along with Quetrupillán and the Chilean portion of Lanín, are protected within Villarrica National Park. Ascents of the volcano are popular with several guided ascents reaching the top during summer.
Villarrica, with its lava of basaltic-andesitic composition, is one of only five volcanoes worldwide known to have an active lava lake within its crater. The volcano usually generates strombolian eruptions, with ejection of incandescent pyroclasts and lava flows. Melting of snow and glacier ice as well as rainfalls often cause massive lahars (mud and debris flows), such as during the eruptions of 1964 and 1971.
Villarica's symmetrical edifice stands in the Chilean Central Valley as the westernmost of an alignment of three large stratovolcanoes. The alignment is attributed to the existence of an old fracture in the crust, the North West-West trending sinistral Gastre Fault Zone, the other volcanoes in the chain Quetrupillán and Lanín are far less active. This alignment is unusual as it crosses the N-S running Liquiñe-Ofqui Fault, around which most currently active volcanoes are aligned. Currently the volcano covers up an area of 400 km2 and has a volume 250 km3 according to estimates.