Alitar is constructed on Miocene-Pliocene La Pacana and Atana ignimbrite. The volcano is composed from andesites and dacites of Pliocene-Pleistocene age. A wide, deep maar lies at the southwest foot of the volcano. Fumarolic activity occurs both in the northern sector of the maar and another area northwest of it. west of the maar a hydrothermal well system comprising six pools and gas discharges is located in a creek.