Aucanquilcha is part of a cluster of volcanoes located between the Rio Loa and the Chile-Bolivia border. Aucanquilcha sits on top of a 2.7-3.3 mya andesite platform and rises more than over it. The main volcano is composed of an east-west long chain of stratovolcanoes and has an estimated volume of . The maximum slope of the summit area is 25°. During the Cumbre Negra stage, a pyroclastic flow occurred on the northwestern side of the volcano. It covered on a run of and now has a volume of . It was at first identified as a debris avalanche, but the lack of hummocky topography and the presence of large juvenile blocks identify it as a pyroclastic flow. One block in the flow and the lava dome from which the flow originated have been dated at 0.6 mya. Lava flows, mostly from the summit areas, are dark to grey in colour and extend as far as from their vents. It is likely that two small lava domes (Cerro Cumbre Negra and Summit 5867) on the northwest flank occupy flank vents. To the north lies the 3.3 mya old andesite Cerro Tres Monos ridge; to the west lies the east-west Cerro Polan and La Luna ridge.