Irruputuncu underwent a flank collapse that subdivides the volcano into two edifices, the older Irruputuncu I and the younger Irruputuncu II, about 140 ± 40 ka ago. This flank collapse extends southwest from the older crater I and is about thick. It was formed by the collapse of the southwestern flank and forms three distinct units formed by hummock-forming lava blocks and flow ridges up to long. Each stage is associated with an individual crater named Crater I and Crater II. The flank collapse was probably produced by oversteepening of the volcano or by asymmetric growth. Subsequent activity of the volcano has completely filled the scarp. The lack of ground deformation during eruptive activity suggests the magma chamber of Irruputuncu may be more than deep, which may be linked to the thickness of the crust beneath the Central Andes, ranging .