effectively, but it is now exposed to greater weathering through the freeze-thaw cycle of water, with maximum occurrence during warm summers. In 2015, climbers captured video footage of a huge rockfall on the Tour Ronde's east face, which suggests that instability continues in this area. In 2001, researchers from France, Italy and Korea published the results of a study into uranium contamination of the wider environment by wind-borne particles. They analysed an ice core that had been drilled to a depth of on the Dôme du Goûter, and at an altitude of . It produced an accurate timeline of contamination levels going back 200 years and was the first published uranium concentration data for any alpine or polar icefield. Ice that pre-dated 1940 was shown to contain fairly uniform and low levels of uranium, consistent with natural background contamination. In contrast, ice that had been laid down after World War II showed large excesses. These were attributed to aerial transport of uranium dust, produced by extensive mining and milling operations that occurred in East Germany (and also in France to a lesser extent) between 1965 and the end of the 1980s. No evidence was found that either the 1986 Chernobyl disaster or other nuclear power plants had caused the high levels of observed uranium contamination. Modern military history A troop garrison, known as the Casermetta, was active for many years at the Col de la Seigne, on the border between France and Italy. In the 1930s, during a period of increased international tension, the Mont Blanc massif was used by both countries wanting to demonstrate their military might, and large drills and troop exercises were undertaken at high altitude. During World War II, at a time when the French army had already been defeated by Nazi Germany, France found itself under attack again, but this time by Italian soldiers in many alpine locations including the area around the Col de la Seigne. Evidence of past fortifications and old firing points are still visible throughout the area Towards the end of World War II, the highest engagement of the entire war occurred on the glaciers above Chamonix. With the Germans nearly defeated, and their garrison in Chamonix surrounded by the liberating forces, a contingent of Austro-German soldier—who were based around the Torino Hut on the Italian side of the massif—launched a dawn bombardment on Chamonix from positions adjacent to the cable