Osorno is one of the most active volcanoes of the southern Chilean Andes, with 11 historical eruptions recorded between 1575 and 1869. The basalt and andesite lava flows generated during these eruptions reached both Llanquihue and Todos los Santos Lakes. The upper slopes of the volcano are almost entirely covered in glaciers despite its very modest altitude and latitude, sustained by the substantial snowfall in the very moist maritime climate of the region. This mountain also produces pyroclastic flow, since it is a composite volcano.