Cerro Acotango

Acotango is the central and highest of a group of stratovolcanoes straddling the border of Bolivia and Chile. It is 6,052 metres (19,856 ft) high. The group is known as Kimsa Chata and consists of three mountains: Acotango, Umurata (5,730 metres (18,799 ft)) north of it and Capurata (5,990 metres (19,652 ft)) south of it.

The group lies along a north–south alignment. The Acotango volcano is heavily eroded, but a lava flow on its northern flank is morphologically young, suggesting Acotango was active in the Holocene. Later research has suggested that lava flow may be of Pleistocene age. Argon-argon dating has yielded ages of 192,000±8,000 and 241,000±27,000 years on dacites from Acotango. Glacial activity has exposed parts of the inner volcano, which is hydrothermally altered. Glacial moraines lie at an altitude of 4,200 metres (13,800 ft) but a present ice cap is only found past 6,000 metres (20,000 ft) of altitude.

The volcano is a popular hiking route in the Sajama National Park and Lauca National Park. It is on the border of two provinces: Chilean province of Parinacota and Bolivian province of Sajama. Its slopes are within the administrative boundaries of two cities: Chilean commune of Putre and Bolivian commune of Turco.

To climb the summit from the Chilean side is dangerous due to land mines, however it is relatively safe to climb the summit from the Bolivian side. The southern ascent starts over a glacier and passes an abandoned copper mine.