Some glaciers are subject to sudden “expansions” called surges: suddenly, without warning and with incredible rapidity, the speed of the glacier increases and the front advances by several metres or hundreds of metres, inexorably burying and destroying whatever comes in its path. It gives the feeling of watching a film on glacier advance put ‘’fast forward’: in a few days or a few hours you can see what usually takes a much longer time. This kind of glacier ‘floods’ can cause severe damage to neighbouring anthropic infrastructures, can destroy villages, woods and forests, cultivated fields , tourist structures, mountain cabins and skiing facilities: stopping an expanding glacier is impossible. Many glaciers of Alaska, Pamir and the Karakorum are unfortunately famous for the repetition of these phenomena and for their grandiosity. One of the most impressive surges occurred in the Karakorum in 1953, when the Kuthiah Glacier advanced 10 km in two months at a speed of 16 m a day, as measured by Prof. Desio and stopped its advance just 2 km from a village. The Black Rapids Glacier in Alaska, between 1936 and 1937 advanced 6.5 km in three months. The Hubbard glacier, one of the biggest of North America, which discharges into Disenchantment Bay in Alaska, dammed part of the bay, the Russell Fijord, many times between 1986 and 2002 with its rapid advancement – this brought about the formation of a lake that subsequently overflowed with dramatic consequences. A glacier that has been greatly observed from this point of view is the Variegated Glacier in Alaska, subject to cyclic surge phenomena, about every 20 years. The results of these studies have shown that the phenomenon is due to the sliding of the glacier on a ‘bed’ of melt water at its base. In the Alps, on the contrary, glacial surges are a rare phenomenon: 4 surge episodes have occurred, for example, on the Vernagtferner, in the Oetztal, between 1899 and 1848, forming, on each occasion, a barrage lake that caused floods downstream when it drained out.