the Central Volcanic Zone, one of the four volcanic zones of the Andean Volcanic Belt. The Central Volcanic Zone spans Peru, Bolivia, Chile and Argentina and contains about 44 active volcanoes, plus a number of monogenetic volcanoes and silicic caldera volcanoes. A number of older inactive volcanoes are well preserved owing to the dry climate of the region. Many of these systems are in remote regions and thus are poorly studied but pose little threat to humans. The largest historical eruption in the Central Volcanic Zone occurred in 1600 at Huaynaputina in Peru, and the recently most active volcano is Lascar in Chile. Socompa is a high composite volcano consisting of a central cone and several lava domes; it is the most voluminous conical volcano of the Central Volcanic Zone and one of the highest edifices there, rising more than above the surrounding terrain. Several dacitic lava flows form the summit area of the volcano, the youngest of which originates in a summit dome. This summit dome is capped off by a summit crater at an altitude of , and four additional craters occur northeast of the summit at altitudes of . Northwest of the summit, a dacitic lava dome is the source of a high talus slope. The summit area is surrounded by an inwards-dropping scarp that opens to the northwest and whose southern margin is buried by lava flows. Pyroclastic flows crop out beneath lava flows in the northwestern segment of the volcano, within the scarp. On the southern and eastern side the scarp is long and high, while the southern side is about long. A large wedge-shaped scar is recognizable on the northwestern flank, delimited by prominent scarps running through the western and northern flanks of the edifice. The existence of a lake in the summit area within the scarps at elevations of has been reported. On the northeastern flank a pumice deposit is clearly visible. Lava domes have various shapes and are recognizable in the southern and western slopes, while lava flows appear mainly on the eastern and northern slopes. The whole edifice has a diameter of and, like many Central Andes volcanoes, probably originally consisted of lava domes, lava flows and various pyroclastic formations. The volcano apparently developed within a northwest-striking valley, the southern part of which now contains Laguna Socompa. This lake lies at an elevation of ; to the north the volcano is