The Erosion Pyramids

Shortly before reaching the town of Zone in Cislano, the view opens on a monumental scenery with the Pyramids of Erosion, commonly called “Fairy Stones”, but scientifically identified as erosion pyramids. This rare natural phenomenon, which has few examples in the world, is caused by the action of water on a moraine on steep slopes; the large rocks lying on top of the pyramids act as "hats" thus protecting the ground below, thereby reducing the erosive effects of the water. An important testament of the geological evolution of the ice age and post-glacial Alps.

The vast deposit causing this phenomenon has been left about 150,000 years ago by a side branch of a glacier penetrated into the valley of Bagnadore, glacier originating from the Camonica Valley that, during the third glaciation of Riss, filled the basin now occupied by the Lake Iseo.
The moraine is a mixture of earth and small pebbles of different caliber and of various origins, cemented and hardened to the point just to have some firmness, but also easily eroded by the runoff of rainwater. The erosive action of rain on the deposit gradually isolate large rock boulders (up to 6 meters in diameter). These boulders exert a protective action, like an umbrella, on the underlying material shaping a column of earth, the pyramid which can reach 30 meters in height is also sheltered by a protective film formed by insoluble clay that is transported by water along the sides of the same. When the boulder on the top falls, the pyramid disintegrates rapidly to find another hat at a lower level, a delicate magic, due to very rare environmental and physical combinations.