Licancabur

Licancabur () is a stratovolcano on the border between Bolivia and Chile, south of the Sairecabur volcano and west of Juriques. Part of the Andean Central Volcanic Zone, it has a prominent, -high cone. A summit crater containing Licancabur Lake, a crater lake which is among the highest lakes in the world, caps the volcano. Three stages of lava flows emanate from the edifice.

Licancabur formed atop of Pleistocene ignimbrites and has been active during the Holocene, after the ice ages. Although no historic eruptions of the volcano are known, lava flows extending into Laguna Verde have been dated to 13,240 ± 100 BP. The volcano has primarily erupted andesite, with small amounts of dacite and basaltic andesite.

Its climate is cold, dry and very sunny, with high levels of ultraviolet radiation. Licancabur is not covered by glaciers. Cushion plants and shrubs form the vegetation lower on its slopes. Chinchillas were formerly hunted on the volcano.

Licancabur is considered a holy mountain by the Atacameno people, which consider it a relative of Cerro Quimal mountain in northern Chile. Archeological sites have been found on its slopes and in the summit crater, which was possibly a prehistoric watchtower.

Name

"Licancabur" derives from the Kunza words used by the Atacameño people to refer to the volcano: ("people", or ''pueblo'') and ("mountain"); thus, "mountain of the people". It is also known as "Volcan de Atacama" and "Licancaur". The border between Bolivia and Chile, defined by the 1904 Treaty of Peace and Friendship, crosses the volcano.

Geography and geology

General setting

Off the western coast of South America, the Nazca Plate subducts into the Peru-Chile Trench beneath the South American Plate. The Andean Volcanic Belt consists of three main volcanic zones: the Northern Volcanic Zone (from 2° N to 5° S), the Central Volcanic Zone (16° to 28° S) and the Southern Volcanic Zone (33° to 46° S). These volcanic zones are separated by gaps without volcanic activity, where the subducting plate is shallower. These shallower zones have been attributed to the high speed of the plate collision, the young age of the subducting oceanic lithosphere and the curvature of the subducting plate. The most plausible theory is that variations in buoyancy of a subducting plate creates a flat subduction zone. The Cocos, Juan Fernandez and Nazca Ridges are associated with such volcanic gaps where they collide with the oceanic trench. The subduction of spreading ridges can also diminish volcanism, as observed at the Chile Rise further south. The buoyancy of these crustal structures may hinder subduction, reducing water supply to the mantle and inducing the formation of melts.

Not all volcanism in Chile is relative to subduction of the Nazca Plate; the Chile Ridge exhibits submarine volcanism, and volcanism in the Austral Volcanic Zone is triggered by the Antarctic Plate subducting beneath the South American Plate. , one hundred ninety-eight South American volcanoes were on the Global Volcanism Program's list of volcanoes with Holocene activity.

Local setting

Licancabur is part of the Central Volcanic Zone and is situated at the western edge of the Altiplano. Among the active volcanoes of the region are Putana (erupted at the end of the 19th century), Llullaillaco (1868) and Lascar (1993). Other stratovolcanoes are Tacora, Nevados de Payachata, Isluga, Tata Sabaya, Ollague, Tocorpuri, Sairecabur and Socompa. The Central Volcanic Zone has more than 1,100 volcanic centres—many older than the Pleistocene, since the area's prevailing arid climate prevented substantial erosion. During the Miocene, the area around Licancabur was the site of major ignimbrite-forming eruptions. Llano de Chajnantor (southeast of Licancabur) is the site of several observatories, including the Llano de Chajnantor Observatory.

Licancabur is a -high symmetrical cone. The cone rises above the surrounding terrain, covering a base diameter of . The volcano has a total volume of , with mean slopes of the cone being about 30°. The volcano has erupted blocky lava flows, with thicknesses ranging from ; younger lava flows are thinner. Young lava flows on the western sides of the volcano are long; older flows extend . Some old lava flows reach Laguna Verde, and -long pyroclastic flow deposits have been found. There are no glacial cirques on the volcano. The volcano's eastern and western flanks have distinct appearances, since it formed on a basement which dips towards the Salar de Atacama. West of Licancabur are deposits stemming from debris avalanche activity, including blocks wide.

Crater and lake

The top of the mountain features a -wide crater which contains an elliptical lake. The lake is below the crater rim, it has a length of and a depth of . Fed by snowfall, it is one of the highest lakes in the world. Based on its relative lack of salt deposits, in 1955 researchers postulated that the lake spilled through a notch in the crater's southwestern rim when the climate was wetter. Excess water now leaves through seepage, keeping salt levels low. There are other lakes (usually frozen) at similar altitudes in the Andes.

Neighbouring volcanoes

Licancabur is just south of Sairecabur, a group of volcanoes which rises to and is an apparent source of recent volcanic activity. East of Licancabur is its companion volcano, Juriques. It is high and has a large——deep crater. West–east alignments of volcanoes like Licancabur and Juriques are common in the region, due to tectonic influences. Araral, Cerro Cabana, Cerro Canapa, Cerros de Tocorpuri, Cerro Linzor, Inacaliri, Inca, Jardin, Putana, Volcan Tatio and Zapaleri are other volcanoes in the neighbourhood of Licancabur. southeast, volcanoes continue with Tocol, the Purico Complex and the -high Llullaillaco. Volcanoes in the Puna de Atacama

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