The terrain around Llullaillaco consists of andesite and dacite lavas and pyroclastics of Miocene to Pliocene age. Some Oligocene-Miocene layers are exposed in the Quebrada de las Zorritas. Dates obtained by argon-argon dating range between 11.94 ± 0.13 and 5.48 ± 0.07 million years ago. west of Llullaillaco do Paleozoic granites and volcanite rocks crop out. Elsewhere these layers are buried by Cenozoic rocks. There are several faults in the region, such as the Imilac-Salina del Fraile lineament whose movement has influenced the activity of Llullaillaco.