Antofagasta de la Sierra is a volcanic field in Argentina. The main type of volcanic edifice in the area are scoria cones, it is formed by the La Laguna, Jote and Alumbrera volcanoes. The first and last of these form a sub-group which is better researched. Various dating methods have yielded ages from several million to several hundred thousand years ago, but some vents appear to be of Holocene age. Geology Regional Volcanic activity in the Andes occurs in four regions, the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone and the Austral Volcanic Zone. The first three of these are found where the Nazca Plate subducts beneath the South America Plate, while the last zone occurs at the subduction zone of the Antarctic Plate. The Andean Central Volcanic Zone runs along the Western Cordillera of the Andes and along the Altiplano. During the Neogene, the position of this volcanic arc moved eastward and the arc became broader, probably due to a change in the tilt of the slab of the Nazca Plate. Volcanic activity during this time was heavily influenced by local strike-slip faults which acted to channel the magma flows. About 7 million years ago, tectonics and volcanic activity changed in the region probably in response to the delamination of the crust beneath the region: Large scale ignimbrites were erupted at Galán and small back-arc volcanoes erupted mafic basaltic andesite lavas. These small volcanic centres consist of lava domes, lava flows, maars, scoria cones and tuff rings. Local The Antofagasta de la Sierra volcanic field lies within the north–south trending tectonic depression of the same name, in the Catamarca Province. Of the individual vents the La Laguna and Alumbrera cones are the best studied ones, they lie about south of Antofagasta de la Sierra. These volcanoes are associated with black lava flow fields. The Jote volcanoes consist of a cluster of cinder cones and lava flows. Alumbrera cone is high and has an elliptical shape with a maximum length of , probably due to wind influencing the growth of the cone. The cone shows signs of having been gravitationally unstable, including a sector collapse on its northwestern flank. The cone has a wide crater and a few fissure vents. Alumbrera has a volume of and is the source of a large lava flow field which covers a surface of and surrounds the Alumbrera cone. Lapilli