The southern Argentine glacier Perito Moreno was set to fracture Monday, in a rare collapse during the winter in the southern hemisphere, according to dpa. Give the unusual timing for this spectacular natural phenomenon, foreign tourists did not gather by the thousand in the area, as has happened on other years. It was mostly a local crowd who waited to see how the glacier - a natural dike into the lake Lago Argentino, made of millions of tonnes of ice - breaks in a deafening crash. Despite the snow, the rain and very low temperatures, some 1,500 people travelled 80 kilometres on dirt roads from the town of El Calafate to the glacier, inside the Glaciers National Park. The glacier started to let water in on Friday, and a tunnel was created through the ice whose roof was expected to collapse Monday. The Perito Moreno, in the Argentine Patagonian province of Santa Cruz, is one of the few still-growing glaciers in the world. In the process, it dams up large masses of water. There is a difference of up to 30 metres in altitude between water on the two sides of the ice barrier, which can be up to 60 metres high itself. Large blocks of ice have already collapsed in recent days, and the definitive crash appeared imminent Monday, Argentine media reported. Recent episodes of the phenomenon were to be seen in 2004 and 2006, when the ice barrier collapsed causing a huge avalanche of water. The region, some 2,500 kilometres south-west of Buenos Aires, is very thinly populated, and the phenomenon does not entail risks for people or property. The Perito Moreno last collapsed in winter in 1951.