The avalanche that buried an Italian mountain hotel trapped at least 30 people under tonnes of snow on Wednesday. The region of Abruzzo had exceptionally heavy snowfall, up to 2.5m deep in places. The weight of that fresh snow on top of older, smoother snow created an unstable snowpack that would have made it prone to crack and slip easily. It is quite likely that earthquakes or their aftershocks on Wednesday could have triggered the avalanche; the new snow sliding and rapidly accelerating to create a deadly avalanche.
These are capable of carrying a million tonnes of snow at speeds up to 200mph, with a shock wave of air at the leading edge that blasts away buildings and trees in its path.
The deadliest avalanches were experienced in Italy during the First World War. The Western Front stretched across the Alps, where Austrian and Italian armies faced each other in trenches dug in snow and ice. The troops suffered atrocious conditions in bitterly cold winters, with temperatures down to minus 30C. It was called the White War, and avalanches were a significant threat. “Entire platoons were hit, smothered, buried without a trace, without a cry, with no other sound than the one made by the gigantic white mass itself,” wrote one Italian observer.
The worst incidents happened at the end of December 1916 when 4m of snow fell in 48 hours, setting off two days of avalanches that killed about 10,000 troops. Whole companies of men, guns and animals were swept away and many of their remains were not found until the next spring. Some historians believe that many of the avalanches were set off deliberately using artillery fire. However, the risks to the attacking side would have been enormous. More than 60,000 men died in the Alps in the entire war, about a third of those killed from avalanches and another third died from cold. Even today, frozen bodies of soldiers are still emerging as mountain glaciers thaw.