Eruption rates increased 6 million years ago, coinciding with magmas becoming more uniform in composition and the onset of strong hydrothermal alteration. It is possible that solidification of magmas below the volcano insulated the feeding channels from heat loss and caused the temperatures in the system to increase. Activity waned again 2 million years ago, with magma and included crystals being drawn from depths of and forming the Aucanquilcha volcano proper. The 10-million-year duration of activity of the Altiplano-Puna volcanic complex systems is comparable to the duration of Aucanquilcha activity. The age of the lava flows ranges from heavily glaciated andesite flows overlying less-eroded ones to possibly postglacial lava flows that may be tens of thousands of years old.