As far as geology is concerned, the area of Sirente Velino is characterized by Mesozoic formations, with Cretaceous organogenic limestone forming most of the mountains; however, there is also limestone dating back to the Jurassic period.

The Tertiary formations are well evident, with the marly limestone of the Lower Miocene both on the south-western slope and on the northern chain of Sirente, with mountain layer debris; they are also evident near the Rocche Plateau with the molassic series of the Middle-Upper Miocene.

However, the latest land of Quaternary are without any doubt, because of their diversity of origin and composition, a primary role in determining the morphological structure of the area.
The events of this geological period (alluvial deposits, the remains of glacialism of karst and river erosion) are those most clearly evident and more directly responsible for the current landscape.

The alluvial deposits, derived from ancient glacial lakes, have now become beautiful plateaus set between mountain ranges. To be remembered, just to mention the most extensive, the Pezza Plains, The Rocche and the Campo Felice Plateaus and the Sirente Meadows.

The Sirente, Magnola and Velino testify the presence of ancient glaciers not only of many glacial circuses scattered here and there on various peaks, but also the remains of moraines that sometimes stretch, as on the north-eastern side of the Sirente even for several kilometres.