Lake Cornino is a small body of water that originated during the retreat of the ice, which occurred around 10,000 years ago. In this period numerous and impressive landslides occurred along the sides of the valleys, which were suddenly deprived of the support represented by the mass of ice itself. The current morphology is the result of one of these landslides.
These waters are easily distinguishable from those coming from the Prealps by a chemical "trace" that distinguishes them: coming from the Tagliamento basin they are loaded with calcium sulphate obtained from the dissolution of the chalks that abound in its basin. Waters of different origins also reach the lake, coming from the Monte Prat plateau.
The lake is just over 140 meters long and 8 m deep. It has neither tributaries nor emissaries, but the underground water circulation is such that it still allows rapid water exchange. Hence its particular transparency and the very low temperature variations (which generally fluctuate between 9-11 °C) over the course of the year. These characteristics allow it to be classified as an oligotrophic lake as it is poor in nutrients. The bottom is populated by green algae that form dense underwater meadows, while the rocks are colonized by blue algae. The scarcity of nutrients present and the low temperature of its waters significantly reduce the possibility of life within it. The fish fauna present is scarce and linked to the introduction of Cyprinids and Salmonids but the presence of the Crayfish is certainly interesting.