Geology and Morphology

The geological origin of the Cimini hills and the valley of Lake Vico, must be attributed to volcanic activities with explosive phenomena that originated soils composed of different kinds of tuff. The explosive activity scattered over a great distance ashes and lapilli that, through build-up and consolidation, generated the so-called pyroclastic rocks.

The volcanic complex of Mount Cimino, situated a few km north of the Natural Reserve, started first its eruptive activity by the end of the Pliocene epoch (approx. 4.5 millions of years ago). The products of the eruptions overlapped the clay and the sea-sand of the valley of the Tiber. At that time, the Cimino cone was perhaps almost twice as high as it is today, and it was during that eruptive phase that the peperino, typical of the area, was generated.

Afterwards, during the Pleistocene epoch, the volcanic complex of Vico started its eruptive activity with the emission of lava characterized by the presence of leucite, a mineral that is completely absent in the lava of Mount Cimino.

The eruptive activity of volcano Vico alternated periods of rest and violent explosions with the formation of largely tuffaceous rocks, amongst which the grey tuff with black slags stands out.

The volcano-tectonic subsidence caused by the long period of intense volcanic activity originated the caldera of Vico.

The volcanic activity continued with alternate phases and it still continues today with minor manifestations, such as the many hot-springs existing in the area.

The boundaries of the Natural Reserve run largely along the ridge of the crateral crest and encompass both the Lake and Mount Venere (851 m) in an ample basin. The territory of the thalweg is mostly flat but the gradient of the inner side of the basin is extremely steep. The altitude varies from 510 to 965 m above sea level, and the three highest peaks are the ones of Mount Fogliano (965 m), Poggio Nibbio (896 m) and Poggio Gallesano (839 m). The rainfall is one of the heaviest in all the region, reaching 800/850 mm per annum.

All the rainwater collected by the inner side of the perimetric crown and by Mount Venere directly nourish the lake.