The symmetrical, glacier-clad Osorno volcano forms a renowned landmark that towers over Todos los Santos and Llanquihué lakes. Osorno was constructed over a roughly 250,000-year-old eroded stratovolcano, La Picada, that has a mostly buried 6-km-wide caldera.
La Picada underlies Osorno on the NE and has postglacial maars and scoria cones. The 2652-m-high dominantly basaltic to basaltic-andesite Osorno is one of the most active volcanoes of the southern Chilean Andes.