Volcán Putana

Volcán Putana, sometimes referred to as Jorqencal or Machuca, is a stratovolcano located in the Central Volcanic Zone (CVZ) of the Andes on the border between Bolivia and Chile and close to the Sairecabur volcanic complex. Its summit is 5,884 metres (19,304 ft) above sea level and contains a summit crater with two smaller craters nested within it. Beneath the summit, the volcano features a number of lava domes and lava flows, some of which originated in flank vents.

While the occurrence of historical activity is unclear (aside from an episode in 2009–2010 where the edifice was uplifted by 4 centimetres (1.6 in)), the volcano features persistent and vigorous fumarolic activity that creates a large plume of gas above the summit. Sulfur deposited by the fumaroles has been mined.

Volcán Putana lies on the border between Chile and Bolivia, and is also known as Jorgencal, Jorjencal or Machuca. The area is remote and difficult to access and thus poorly studied.

Volcanism in the Central Andes is the consequence of the subduction of the Nazca Plate beneath the South American Plate and occurs in form of the 1,500 kilometres (930 mi) long Central Volcanic Zone, one of four volcanic belts in the Andes. The Peruvian and the Pampean "flat slab" segments separate this volcanic belt from its neighbours, the Northern Volcanic Zone to the north and the Southern Volcanic Zone south respectively.

Volcán Putana is part of the Central Volcanic Zone, which aside from this volcano contains a number of large calderas associated with silicic volcanism. Over 13 volcanoes in the Central Volcanic Zone have been active in historical time, out of about 69 with evidence of Holocene activity. Of these volcanoes Láscar is the most active volcano in the Central Volcanic Zone; a major eruption occurred there in 1993.

Volcán Putana is a 5,890 metres (19,320 ft) high volcano elongated from north to south. It is constructed by lavas and pyroclastic material, with effusive products such as lava domes and lava flows forming the bulk of the edifice. Most lava flows were viscous enough that they do not exceed 3 kilometres (1.9 mi) of length, older flows are longer. Younger lava flows occur on the western slope, and some lava flows appear to be younger than the last glacial age.

The summit contains a 500 metres (1,600 ft) wide summit crater which itself contains two smaller craters, one is 300 metres (980 ft) wide and lies on the northeastern side and the other with a width of 130 metres (430 ft) is in the centre of the summit crater. Lava flows/lava domes are emplaced in the southern part of the main summit crater, and there are deposits of past Vulcanian eruptions. Additional adventive vents occur on the slopes of Volcán Putana; a particularly noticeable fan-shaped flow northwest of Volcán Putana originated in such a flank vent.

The volcano forms part of a complex of ash flows and cones which covers a surface area of 600 square kilometres (230 sq mi). Volcán Putana was constructed on the Purificar and Tatio ignimbrites of Pliocene-Pleistocene age; the whole edifice is constructed around a pre-Holocene volcano.