During the Pliocene, fissure eruptions formed the trachytic Pérez Formation which crops out north of Chullkani. In the Wanq'u Jaqhi gorge (Huancoaki), these deposits crop out . Andesitic lavas erupted 2.3±0.2 Ma are named Wichhu Qullu lavas. Another effusive activity generated the Carbón Qullu lavas (Carbon Kollu) and finally the Pukara lava dome, whose collapse generated the Thuwas Ventilla pyroclastic flow.