The Quaternary-age Casiri is one of the youngest volcanic systems in southern Peru with postglacial activity, and Peru's southernmost Holocene volcano. Holocene lavas sourced from fissure vents overlie Pleistocene-age moraines and are uneroded; radiometric dating on the volcano has yielded ages of 50,000 years and surface exposure dating carried out more recently has found ages of 6,000 ± 900 and 2,600 ± 400 years for two dark lava flows southwest and south of Casiri's main summit, respectively.