Zona Sur (Southern Zone) is one of the five natural regions on which CORFO divided continental Chile in 1950. Its northern border is formed by the Bío-Bío River, which separates it from the Central Chile Zone. The Southern Zone borders the Pacific Ocean to the west, and to the east lies the Andean mountains and Argentina. Its southern border is the Chacao Channel, which forms the boundary with the Austral Zone. While the Chiloé Archipelago belongs geographically to the Austral Zone in terms of culture and history, it lies closer to the Southern Zone.
Llanquihue glaciation
Although many lakes can be found in the Andean and coastal regions of central Chile, the south (Sur de Chile) has the country's most lakes. Southern Chile stretches from below the Río Bío-Bío at about 37° south latitude to below Isla de Chiloé at about 43.4° south latitude. In this lake district of Chile, the valley between the Andes and the coastal range is closer to sea level, and the hundreds of rivers that descend from the Andes form lakes, some quite large, as they reach the lower elevations. They drain into the ocean through other rivers, some of which (principally the Calle-Calle River, which flows by the city of Valdivia) are the only ones in the whole country that are navigable for any stretch. The Central Valley's southernmost portion is submerged in the ocean and forms the Golfo de Ancud. Isla de Chiloé, with its rolling hills, is the last important elevation of the coastal range of mountains.
The lakes in this region are remarkably beautiful. The snow-covered Andes form a backdrop to clear blue or even turquoise waters, as at Lago Todos los Santos. The rivers that descend from the Andes rush over volcanic rocks, forming numerous white-water sections and waterfalls. Some sections still consist of old-growth forests, and in all seasons, but especially in the spring and summer, there are plenty of wildflowers and flowering trees. The pastures in the northernmost section, around Osorno, are well suited for raising cattle; milk, cheese, and butter are important products of that area.