Lake Leffe

About

The Lake Leffe was a Pleistocene lake, located in the present-day Val Gandino, in the Province of Bergamo.

The history of Lake Leffe can be traced back to the first phase of the Pleistocene, about 1,800,000 years ago. Its presence is clearly demonstrated both by the current geological conformation of Val Gandino, clearly visible from the surrounding heights, and by the analysis of the subsoil, rich in layers of clay, lacustrine carbonates, and lignite, formed due to the sedimentation of aquatic plants.

The creation was made possible by the barrier that formed at the terminal part of the Romna stream, which at that time flowed into the Serio through a paleovalley (now completely covered by debris) located where the Casnigo cemetery currently stands, opposite the settlement of Colzate. The mouth was obstructed by the deposition of materials carried by the Serio, also causing a backflow of the waters brought downstream by the Romna. Another theory suggests that the formation of the lake was due to the movement of the faults that make up the Pizzo Formico, which, due to tectonic activity, allowed the lowering of the rocky substrate.

The lakebed, initially at the same level as the rest of the Val Seriana, began to slowly accumulate debris, rising by about 130 meters in the basin dominated by the Farno and Formico, a level that still characterizes the Val Gandino plateau. At its maximum expansion, it covered an area of 4.2 km², a maximum width of 4.4 kilometers, and a maximum depth of 20–30 meters.

Its tributaries were the streams of the Piana and Concossola valleys, which currently merge to form the Romna, and the Re stream, while the Rino stream, unlike today, directed its course toward the San Rocco saddle, thus flowing into the basin of the Valle Rossa.

Adapted from Wikipedia (CC BY-SA)。Photography via Wikimedia Commons.