the High Andes and rises from the southern end of the Puna de Atacama, a high plateau next to the Atacama Desert with an average elevation of metres. The border between Argentina and Chile runs across the summit of the mountain in east-west direction. The Argentine part is within Catamarca Province and the Chilean in Copiapo Province of the Atacama Region. The highway runs between the city of Copiapo west of the volcano and the Paso San Francisco to Argentina, lying about north of the volcano, making it more accessible than many other volcanoes there. The region is uninhabited and lacks water resources; many parts are only accessible through dirt roads. Ojos del Salado is a dormant volcano that rises to , or elevation. It is the world's highest volcano and the second-highest summit of the Andes, and the highest summit in Chile. Ojos del Salado is not a single conical summit but a massif/complex volcano formed by overlapping smaller volcanoes, with over 20 craters. Two edifices, less than wide, flank the wide summit crater on its eastern and western side. Basalt, gravel, pumice and scoria crop out in its rim, which is lower on the northern side. A second wide crater lies just west of the summit crater. Reportedly, the summit is separated by a deep gap into two separate peaks. Thick short dacitic lava flows make up the core area of the volcano but pyroclastic fall material covers much of the summit area. The massif rises about above the surrounding terrain and covers an oval area of about -, consisting of lava domes, lava flows, pyroclastic cones and volcanic craters that rise about above the surrounding terrain. The massif appears to feature a buried caldera, visible through a slope break from the western side, and/or a wide depression. The occurrence of a rift-like structure with numerous small craters has also been reported. Volcanic cones form a north-northeast trending alignment on the western flank. Cerro Solo and El Fraile are large lava domes on the flanks of Ojos del Salado, and produced pyroclastic flows. Wind-driven erosion has produced megaripple sand fields on the northern flank. Above elevation talus-covered slopes and lava flows form the bulk of the surface, while the vast desert plains begin below elevation. The ground above elevation is expected to contain permafrost, which is likely continuous at higher elevations and overlaid with a thin active layer.