A cataclysm in the Dolomites
About 12,000 years ago, near the end of the last glacial period, a massive section of the Pomagagnon-Tondi di Faloria ridge collapsed into the Boite River valley. An estimated 0.2 cubic kilometers of rock and debris suddenly slid away, creating a natural barrier across the valley floor. This event, known as the Cortina d'Ampezzo landslide, fundamentally reshaped the local area. The Boite River, its path obstructed, began to back up, forming a large lake in the basin where the town of Cortina d'Ampezzo is located.
Geologists determined the age of this rockslide using a technique called cosmogenic nuclide dating. When rock is exposed at the Earth's surface, it is bombarded by cosmic rays. These high-energy particles cause nuclear reactions within minerals like quartz, producing rare isotopes such as Beryllium-10 (¹⁰Be). The production rate of these nuclides is known, so by measuring the concentration of ¹⁰Be in the surface of the landslide's boulders, scientists can calculate how long that rock has been exposed to the sky. This method provides a precise timeline for when the landslide occurred, placing it at the boundary between the Pleistocene and Holocene epochs.