Lazufre is a Quaternary volcanic dome in the central Andes, on the border between Chile and Argentina. It is part of the Central Volcanic Zone (CVZ), one of the four distinct volcanic belts of South America. The CVZ includes a number of calderas and supervolcanoes that have emplaced ignimbrites in the region. Lazufre and the majority of the Andean volcanoes formed from the subduction of the oceanic Nazca Plate under the continental South American continental lithosphere. The dome has been uplifting for the past 400,000 years and features three recent volcanoes, Lastarria, Cordón del Azufre and Cerro Bayo Complex. It may be a volcano that will in the future develop a caldera. The dome began uplifting in the late 19th century at an increasing rate, before slowing down since 2010. The uplift is among the largest in the world and has drawn attention from the scientific communities. Various explanations have been proposed, the most common being that a magma chamber is filling up.
Geography and geomorphology The Lazufre uplift is in the Western Cordillera of the southern central Andes, on the border between Argentina (Catamarca Province) and Chile at about 4,300 metres (14,100 ft) elevation. The city of Antofagasta is about 250 kilometres (160 mi) northwest of Lazufre. Owing to the low population density, the volcanoes of the region and their eruption history are poorly known. The Lazufre volcanic system is made up of the volcanoes Lastarria, Cordón del Azufre and Cerro Bayo. Cerro Bayo, Lastarria and Cordón del Azufre are complex volcanoes consisting of craters, lava flows and individual cones. Cordón del Azufre has produced young-looking lava flows, Lastarria is one of the most fumarolically active volcanoes in the region and a steam explosion was observed at Cerro Bayo in 2007. Their eruption products have dacitic to andesitic composition, with lesser amounts of basaltic andesite. The uplifting area coincides with a 70-kilometre (43 mi) long and 500-metre (1,600 ft) high raised dome with a central depression, surrounded by a ring of Quaternary volcanoes that may share a common magma reservoir and were fed through a network of radial and circumferential lineaments. Among these are the Corrida de Cori-Cerro Escorial, Rio Grande northeast, Chuta southwest, Atalaya and Azufre west and Pirámide northwest of the centre of the uplift. There is no clear evidence of a caldera at Lazufre, but the Los Colorados caldera borders the dome to the southeast. There are no known geothermal manifestations except on Lastarria, although the region is rarely visited.
Geological context Off the coast of South America, the Nazca Plate subducts at a rate of 7 centimetres per year (2.8 in/year) into the Peru-Chile Trench. Subduction gives rise to the Andean Volcanic Belt, which is subdivided into four segments: The Northern Volcanic Zone, the Central Volcanic Zone (CVZ), the Southern Volcanic Zone and the Austral Volcanic Zone. The CVZ between Peru and Chile is about 1,500 kilometres (930 mi) long and includes about 50 potentially active volcanoes in Peru, Bolivia, Chile and Argentina, as well as active faults and multiple large calderas such as Galán and La Pacana. Some of the largest known explosive eruptions and enormous ignimbrites have been erupted here during the last ten million years, producing the Altiplano-Puna volcanic complex. Thirteen volcanoes have erupted during the 20th century. Satellite observations have found ongoing ground movements at volcanoes previously thought extinct, such as Uturuncu in Bolivia, which is uplifting like Azufre; others bear evidence of past uplift. Only a few CVZ volcanoes are monitored. The region of Lastarria-Cordón del Azufre consists mostly of volcanic rocks from the Miocene to Pleistocene. Their composition ranges from andesite to dacite; basalt is less common. About 120 cubic kilometres (29 cu mi) of volcanic rocks have been emplaced there since the Pliocene, with activity migrating northwest to the Lazufre area over time. Lastarria and Cordón del Azufre have been active for the past 600,000-300,000 years. Two major faults, the northeast–southwest trending Pedernales-Arizaro and the north-northwest-south-southeast trending Imilac-Salina del Fraile faults cross at Lazufre, and a major geological lineament named Archibarca traverses the volcanic arc there. The elliptical shape of Lazufre may reflect the regional tectonic stress pattern, which features northwest–southeast compression. The volcanic rocks overlie Permian sedimentary and metamorphic rocks. The "Southern Puna Magma Body", an area with partially molten rock in the southern Puna, extends from Lazufre to Galán.
Climate and vegetation The environment at Lazufre is characterized by an arid climate, large temperature differences between day-night and summer-winter, high insolation, dry air and intense winds. The region lacks vegetation although extremophile microbial life has been identified in salt pans in the area.
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