44 active systems, 18 minor volcanic centres and over 6 large ignimbrite or caldera systems. One of these volcanoes, Ojos del Salado, is the highest volcano in the world. The largest historical eruption in the CVZ occurred in 1600 at Huaynaputina in Peru while Lascár is its most active member, with a major eruption in 1993. Local Purico is a circular shield with a diameter of , whose slopes descend away from a centre at an elevation of . This shield forms a plateau, which is known as the Chajnantor Plateau, and which contains further flat areas such as Llano de Chajnantor, Pampa El Vallecito and Pampa La Bola. There is no evidence that a caldera exists there, unlike in many other volcanoes of this type. To the west, close to the margin of the Salar de Atacama, the shield drops down to a bajada. A north-south trending system of fractures and conspicuous normal faults cuts across the western margin of the Purico complex. On top of this shield, a complex of lava domes and lavas reaches elevations of over above sea level; the vent of the ignimbrite may be buried beneath this complex. This complex forms approximately a wide semicircle open to the southwest around the centre of the shield, which may reflect the existence of a ring fault on which the individual centres were emplaced. Clockwise starting from the west this semicircle includes high Cerro Negro (), Cerro Purico, "dacite dome D" and high El Cerillo which is also known as Cerro Chajnantor (), high Cerro El Chascon (), the high Cerro Aspero ( and the high Cerro Putas () to the south. All these domes (with the exception of the pancake-like "dacite dome D") have conical shapes, and Aspero, El Cerillo and El Chascon appear to be post-glacial in age. The Chascon dome is constructed by lava flows and has a well preserved summit crater, while Cerro Purico is a stratovolcano and also known as Cerro Toco (). Additional more subdued structures in the principal complex are high Cerro Agua Amarga () just southwest of El Chascon and the Cordon Honor with Cerro Purico Sur in the "opening" of the semicircle. Lahars and debris flows from the volcanoes have covered parts of the ignimbrite shield with gravels. A meltwater-fed spring on Cerro Toco is known as Aguada Pajaritos, and a small lake Laguna de Agua Amarga is