 The volcano is mainly of Pleistocene age, but well preserved surface features indicate it may be still active.Other parts of the volcano have been subject to glacial erosion and hydrothermal alteration, and evaporite deposits have formed on its feet.The basement that Paniri is constructed on consists of both Oligocene-Miocene sediments of the San Pedro formation and ignimbrites of Miocene age which are formed by rhyodacitic and rhyolitic material.