A major Plinian eruption occurred 26,450 ± 500 years ago, releasing of ejecta, both volcanic ash and pyroclastic flows. The deposits left contain both andesite and dacite, with phenocrysts consisting of apatite, augite, biotite, iron-titanium oxides, orthopyroxene and plagioclase in a rhyolite matrix. The Plinian deposit has a colour ranging from white to creamy. Like the Piedras Grandes rocks, they tend towards high potassium quantities, and resemble other volcanic rocks of Lascar and the Central Andes in composition. The deposits are formed by a Plinian fallout deposit and an ignimbrite rich in lithics. This Plinian deposit reaches thicknesses of and fell from a eruption column.