| Lake Tauca | |
|---|---|
| Lake Pocoyu | |
 Satellite image of the Altiplano. The green, brown and white surfaces in the lower right quadrant of the image are Lake Poopó, Salar de Coipasa and Salar de Uyuni, respectively. The blue surface at centre top is Lake Titicaca | |
  Lake Tauca | |
| Location | Andes, South America |
| Coordinates | 20°S 68°W / 20°S 68°W[1] |
| Type | Former lake Pleisto- Holocene glacial lake 72,600–7200 BP |
| Part of | Altiplano |
| Primary inflows | Glacial meltwater Desaguadero River, Río Grande de Lipez, Lauca River |
| Primary outflows | Potentially Pilcomayo River |
| Basin countries | Bolivia, Chile, Peru |
| Surface area | 48,000–80,000 km2 (19,000–31,000 sq mi) |
| Average depth | 100 m (330 ft) |
| Max. depth | 142 m (466 ft) |
| Water volume | 1,200–3,810 km3 (290–910 cu mi) |
| Salinity | 20–90 g/L (0.00072–0.00325 lb/cu in) |
| Surface elevation | 3,660–3,770 m (12,010–12,370 ft) |
| Max. temperature | 10 °C (50 °F) |
| Min. temperature | 2 °C (36 °F) |
Lake Tauca is a former lake in the Altiplano of Bolivia. It is also known as Lake Pocoyu for its constituent lakes: Lake Poopó, Salar de Coipasa and Salar de Uyuni. The lake covered large parts of the southern Altiplano between the Eastern Cordillera and the Western Cordillera, covering an estimated 48,000 to 80,000 square kilometres (19,000 to 31,000 sq mi) of the basins of present-day Lake Poopó and the Salars of Uyuni, Coipasa and adjacent basins. Water levels varied, possibly reaching 3,800 metres (12,500 ft) in altitude. The lake was saline. The lake received water from Lake Titicaca, but whether this contributed most of Tauca's water or only a small amount is controversial; the quantity was sufficient to influence the local climate and depress the underlying terrain with its weight. Diatoms, plants and animals developed in the lake, sometimes forming reef knolls.
The duration of Lake Tauca's existence is uncertain. Research in 2011 indicated that the rise in lake levels began 18,500 BP, peaking 16,000 and 14,500 years ago. About 14,200 years ago, lake levels dropped before rising again until 11,500 years ago. Some researchers postulate that the last phase of Lake Tauca may have continued until 8,500 BP. The drying of the lake, which may have occurred because of the Bølling-Allerød climate oscillation, left the salt deposits of Salar de Uyuni.
Lake Tauca is one of several ancient lakes which formed in the Altiplano. Other known lakes are Lake Escara, Ouki, Salinas, Minchin, Inca Huasi and Sajsi, in addition to several water-level rises of Lake Titicaca. The identity of these lakes is controversial; Sajsi is often considered part of Lake Tauca, and the lake is frequently divided into an earlier (Ticaña) and a later (Coipasa) phase.
The formation of Lake Tauca depended on a reduction in air temperature over the Altiplano and an increase in precipitation, which may have been caused by shifts in the Intertropical Convergence Zone (ITCZ) and increased easterly winds. It was originally supposed that glacial melting might have filled Lake Tauca, but the quantity of water would not have been sufficient to fill the whole lake. The lake was accompanied by glacial advance, noticeable at Cerro Azanaques and Tunupa. Elsewhere in South America, water levels and glaciers also expanded during the Lake Tauca phase.