The volcanic history of Aracar is poorly understood. The bottom lava flows have ages of 3.4 ± 1.2 to 2.6 ± 0.4 mya but an age of 100,000 years has also been given. Presumably at first fluid basaltic lavas were erupted. Subsequently, dacite lavas were erupted, accompanied with the formation of a strong slope in the edifice and hydrothermal activity at a northwestern lava dome. Finally the central crater and andesite lava flows were erupted. Beneath altitude lava flows are well conserved. No historical activity is recorded but March 1993, inhabitants of Tolar Grande southeast of Aracar observed a high ash or steam column rising from Aracar, which may be either an eruption or the result of landslides. Satellite images did not detect any deformation of the edifice during this episode, probably due to aliasing.