Sollipulli was active during the Pleistocene and Holocene; the Nevados de Sollipulli are less than 1.8 million years old with argon-argon dating having obtained ages of 490,000 ± 30,000 and 312,000 ± 20,000 years ago. Six separate volcanic units form the edifice; from the oldest to the youngest they are the Sharkfin, Northwest, South, Peak, Alpehué and Chufquén units. The first two may be contemporaneous to the formation of the caldera, or they may predate it. The Sharkfin unit was emplaced in a subglacial environment and later disrupted by faulting, later units show substantial evidence of having been altered by glaciers. Radiometric dates have been obtained on the Sharkfin unit (700,000 ± 140,000 and 350,000 ± 90,000 years before present), the Northwest unit (120,000 ± 16,000, 120,000 ± 140,000, 110,000 ± 30,000 and 100,000 ± 30,000 years before present) and the South and Peak units (68,000 ± 14,000, 64,000 ± 15,000 and 26,000 ± 5,000 years before present). The caldera is nested within an older and eroded caldera, and some parasitic cones are heavily eroded whereas others appear to be younger.