Lake Llanquihue, situated in the southern Los Lagos Region of Chile, is the largest and one of the best-known Chilean lakes. Osorno volcano stands on the southeastern shore of Lake Llanquihue, one of the most active volcanoes of the southern Chilean Andes.
In southern Chile's Lake District, Lake Llanquihue (Lago Llanquihue) is the second-largest and neighbors Todos Los Santos, the best-known Chilean lake. It is in the southern Los Lagos Region, in northern Patagonia's Llanquihue and Osorno provinces.
Lake Llanquihue is known for its vast waters and black sand shores. Puerto Varas, a colonial city famous for its German-style architecture, lies on its southwest shore. The lake has an area of about 330 sq mi (860 sq km) and is 22 mi (35 km) long and 25 mi (40 km) wide with depths of 5,000 ft (1,500 m). Puerto Varas, Llanquihue, and Puerto Octay are popular resorts on its shores.
Successive Piedmont glaciers created Lake Llanquihue's fan-like form during the Quaternary glaciations. The last glacial period is called the Llanquihue glaciation in Chile after the terminal moraine systems around the lake.
Osorno Volcano (Volcán Osorno) is a 2,652 m (8,701 ft) tall conical stratovolcano between Osorno Province and Llanquihue Province in the Los Lagos Region of Chile. Osorno sits atop a 250,000-year-old eroded stratovolcano, La Picada, with a 6 km (3.7 mi) wide caldera.
Osorno is one of the most active volcanoes of the southern Chilean Andes, with 11 historical eruptions recorded between 1575 and 1869, including an eruption on January 19, 1835, which British naturalist Charles Darwin witnessed. The basalt and andesite lava flows generated during these eruptions reached Llanquihue and Todos Los Santos Lakes.
The volcano's upper slopes are almost entirely covered in glaciers despite its 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.