With a volume of of tephra the 4.2 ka eruption has been tentatively classified as 7 in the volcanic explosivity index, making it comparable to the largest Holocene volcanic eruptions. It is the largest Holocene eruption in the Central Andes and of the Central Volcanic Zone, larger than the 1600 Huaynaputina eruption, the largest historical eruption of the Central Volcanic Zone. Most of the erupted volume was ejected by the eruption column, while only about ended up in pyroclastic flows. Caldera collapse occurred during the course of the eruption, generating the unusually small (for the size of the eruption) Cerro Blanco caldera through a probably irregular collapse.