The rocks of Montiferru are the remains of an extinct volcanic complex, covering an area of about , that was active 3.9 to 1.6 million years ago during the Pliocene and Pleistocene epochs of the Earth's geological history. The volcanic activity was at its most intense 3.6 million years ago. The volcano erupted a wide variety of lavas including basanite, hawaiite, phonolite, mugearite, benmoreite and trachyte, as well as small amounts of basaltic andesite and basaltic trachyandesite.