Lascar (volcano)

Lascar is a stratovolcano in Chile within the Central Volcanic Zone of the Andes, a volcanic arc that spans Peru, Bolivia, Argentina and Chile. It is the most active volcano in the region, with records of eruptions going back to 1848. It is composed of two separate cones with several summit craters. The westernmost crater of the eastern cone is presently active. Volcanic activity is characterized by constant release of volcanic gas and occasional vulcanian eruptions.

Lascar has been active since at least 56,000 years ago, though some argue for activity beginning 220,000 years ago. The first known activity occurred at the eastern cone and was characterized by lava flows, before shifting to the western cone where lava domes were emplaced. An eruption event known as Piedras Grandes was followed by the large Soncor eruption. A new western edifice was constructed on top of the Soncor vent, during the Holocene activity then shifted again to the eastern edifice and continues there to this day. The magma supplied to the volcano ultimately comes from the subduction of the Nazca Plate beneath the South America Plate. A number of other volcanoes are found in the region, such as Aguas Calientes, Cordon de Puntas Negras and the giant La Pacana caldera.

The volcano experienced at least three major eruptions throughout its history: One is the Soncor eruption about 26,450 ± 500 years ago, another in 7,250 BCE and the third in 1993. The first of these eruptions released 10–15 cubic kilometres (2.4–3.6 cu mi) of material and is known as the Soncor eruption. The largest eruption of Lascar known to recorded history occurred in April 1993 and caused ash fall as far away as Buenos Aires. Because Lascar is located in a remote area, it is monitored primarily by remote sensing. Explosive eruptions are the greatest hazard at Lascar.

The name originates from the Atacameño word láskar or lassi (English: tongue), thought to refer to the shape of the volcano. Other names for the volcano are Hlàscar, Hlascar, Ilascar, Kar Las, Laskar, Toconado and Toconao.

The new town of Talabre is 17 kilometres (11 mi) west of Lascar. As of 2012^[update], it had a population of 50 inhabitants. Toconao and San Pedro de Atacama lie 34 kilometres (21 mi) and 68 kilometres (42 mi) from the volcano, respectively. As of 2017^[update], stockbreeding and farming were the principal economic activities in Talabre. Chile Route 23 passes about 10 kilometres (6.2 mi) west of Lascar.

Lascar, like El Tatio, is a destination for volcano tourism. Unlike the neighbouring volcanoes Acamarachi, Licancabur and Quimal, there is no evidence of archeological sites on Lascar, possibly because of the volcanic activity. However, the inhabitants of the town of Camar consider Lascar a protective mountain spirit and in Susques (Argentina) it is believed that snow will fall if Lascar is steaming strongly. The inhabitants of Talabre give the volcano gifts, viewing it as their source of water.

Volcanoes in the Andes occur in four separate regions: the Northern Volcanic Zone between 2°N and 5°S, the Central Volcanic Zone between 16°S and 28°S, the Southern Volcanic Zone between 33°S and 46°S, and the Austral Volcanic Zone, south of the Southern Volcanic Zone. These volcanic zones are separated by areas where recent volcanism is absent; one common theory is that the subduction processes responsible for volcanism form a subducting plate that is too shallow to trigger the formation of magma. This shallow subduction appears to be triggered by the Nazca Ridge and the Juan Fernandez Ridge; the areas where they subduct beneath the Peru-Chile Trench coincide with the limits of the Central Volcanic Zone. It is possible that when these ridges are subducted, the buoyancy they carry disrupts the subduction process and reduces the supply of water, which is important for the formation of melts.

Of these volcanic zones, the Central Volcanic Zone of which Lascar is a member of is the largest, covering parts of Peru, Bolivia, Argentina and Chile. The Central Volcanic Zone is located between two areas where subduction is shallower and volcanic activity is absent. In the Central Volcanic Zone, volcanism has been active for 120 million years, although it has undergone eastward migration during this time. Water released from the subducting plate triggers the formation of basaltic magmas that are then injected into the crust.