Cerro del León

Cerro del León is part of the Central Volcanic Zone, a volcanic belt in the Andes. Volcanic activity occurs since the Oligocene and includes dacitic–rhyolitic ignimbrites. On top of these the main volcanic arc, including andesitic-dacitic stratovolcanoes, has formed 300–350 kilometres (190–220 mi) away from the Peru–Chile Trench on a crust 120 kilometres (75 mi) thick. San Pedro and Lascar have historical activity, but only a few volcanoes have been studied, namely Lascar, Ollagüe and Parinacota.[2]

The volcano is part of the San Pedro-Linzor lineament, a 65 kilometres (40 mi) long volcanic chain that extends northwest-southeastward. It was constructed on top the Toconce and Sifon Ignimbrites. The alignment was active during the late Pleistocene–Holocene and contains San Pedro-San Pablo–Paniri–Cerro del León–Toconce–Linzor.[2]

The volcano was constructed in various phases. The base of the volcano is constructed from andesitic lava flows that directly overlie the ignimbrite basement. These at first erupted in the west and east, subsequently northwest and southeast. Dacites and andesites form the last stage and the bulk of the edifice.[2]

The volcano was subject to glaciation, leaving moraines down to 5,200 metres (17,100 ft) altitude, formed during the last glaciation 15,000–11,000 years ago. Glacial effects are noticeable on the north-northwest flanks.[2]

Lavas contain phenocrysts of plagioclase with variable amounts of biotite, clinopyroxene, opaque minerals, and orthopyroxene. The matrix is glassy and contains hornblende and plagioclase. The lavas have vesicular and minor proportions of amygdaloid, porphyric, trachytic and vitrophyric texture.[2] Hydrothermal alteration has been reported.[4]