Avalanches are more likely to occur at the end of the day because temperatures are generally higher at that time, which can cause the surface snow to melt and make the lower layer unstable, thus favoring the triggering of avalanches.
The period of daytime warming can contribute to triggering avalanches at the end of the day. Under the effect of solar radiation, the temperature of the surface snow increases, which can make this layer more unstable. This is due to the formation of ice bridges that promote the sliding of the snow on colder and more stable lower layers. As a result, fractures can form in the snow layer, thus triggering an avalanche.
When snow warms up at the end of the day, it can cause increased instability. This phenomenon is due to the partial melting of the snow on the surface, creating a heavier and slipperier layer of wet snow. The melting water that infiltrates through the different layers of snow can reduce the cohesion between them, thus increasing the risk of triggering an avalanche. Temperature differences between the different layers of snow can also contribute to this instability, as they promote the formation of fragile ice bridges that can collapse under pressure. As a result, at the end of the day, the combination of these factors can make the snow more likely to detach and cascade down the slope, triggering an avalanche.
The increase in the number of skiers in the late afternoon can contribute to triggering avalanches for several reasons. First of all, the repeated passage of skiers on a slope can weaken the already unstable snow layer. Indeed, each passage creates additional stress on the snow structure, thus increasing the risk of triggering an avalanche.
Furthermore, the pressure exerted by the weight of skiers may be enough to destabilize a fragile snow layer, especially in the late afternoon when it has had time to warm up and lose cohesion. Consequently, an increase in the number of skiers on a slope that is already potentially dangerous can be a determining factor in triggering an avalanche.
Moreover, a greater number of skiers in the late afternoon also means a greater number of potential triggers present on the slopes. Thus, even a small mistake by a skier, such as a tight turn or an unintentional skid, can have dramatic consequences by triggering an avalanche. This concentration of skiers on the slopes at a time when the snow is particularly unstable significantly increases the risk of serious accidents related to avalanches.
The withdrawal of the sun's influence at the end of the day can also contribute to triggering avalanches. Indeed, when the sun disappears behind the horizon, the air temperature drops rapidly. This cooling can cause a contraction of the surface snow, creating a denser and potentially unstable layer. This sudden temperature variation can weaken the snow structure, increasing the risk of avalanches.
Did you know that avalanches can occur naturally without human intervention, when an unstable layer of snow is present on a steep enough slope?
Did you know that the first historical record of an avalanche dates back to the year 563 BC in China, where an avalanche swept away part of an army?
Did you know that the speed at which an avalanche can be triggered can reach several tens of meters per second, making it one of the fastest natural phenomena on Earth?
Avalanches are more likely to occur in the late afternoon due to daytime warming which weakens the snow layer and causes instability.
The increase in skiers' attendance can contribute to destabilizing the snow by creating vibrations and additional stress on the snowpack, which can trigger an avalanche.
The withdrawal of the sun's influence at the end of the day can lead to a rapid cooling of the snow, creating conditions conducive to the formation of avalanches by breaking the fragile upper layer.
At the end of the day, it is recommended for skiers to stay on marked slopes, not to venture off-piste, and to follow the safety instructions given by the relevant authorities.
Some avalanche prevention devices, such as barriers or explosives, can be used to trigger avalanches in a controlled manner and thereby reduce risks for skiers and residents in affected areas.
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