Why are there avalanches

Sun-exposed slopes present a higher risk of avalanches during drier spring weather, resulting in rapid warming and melting due to snow weakening. Atmospheric humidity is the amount of water vapor that gets held in the air. We can measure it as water vapor pressure, the mixing ratio, or even specific humidity the ratio of water vapor mass against total air mass.

In humid conditions, surface hoar frost can form on top of the snow in above-freezing temperatures. While there are several red flags that can help people determine the likelihood of an avalanche, some of them relate to timing. For example, evidence of recent avalanches on the slopes is a sure sign of instability. In general, if you can see recent avalanche activity, that means the snowpack is no longer stable.

During daylight hours, avalanches are prevalent due to air temperatures getting warmer. But, they are less likely to occur in the evening or early in the morning. Any new snow that has fallen in the past 24 hours will not have had time to bond with existing snow surfaces, and so will be inherently unstable. The problem is a lot of skiers are keen to create new tracks in the fresh snow, triggering a plethora of new avalanches.

New snow, alongside wind, can potentially be a lethal combination and creates ideal conditions for wind loading and instability. Some skiers may take to the slopes with an avalanche airbag to help them stay as high up as possible in the snowpack should the worst happen.

If you ever spot rollerballs and pinballs out on the slopes, you are likely witnessing the beginning of a loose wet avalanche. Such avalanches form due to new snow or old existing surface snow that is melting. Without the cohesion with the snow layer underneath the snow is too heavy to settle.

This type of avalanche can travel between 62 and miles per hour. Slab avalanche Most common type of winter avalanche due to the build up fresh snow. A slab is a compact snow surface layer that can detach from a weaker snow layer underneath.

The slab slips forward as a whole block or breaks into pieces. Wet avalanche Often occurs after a warm spell or during the spring thaw. Snow becomes heavier as it begins to turn into water. Occurs frequently and are generally small and generally easier to predict than the other types.

Three snow-bound trains were swept into a canyon which killed people. Thousands of avalanches occur in Canada each year. They happen in all regions of Canada, but are more frequent in the mountains of British Columbia, Yukon and Alberta. Avalanches can be triggered by wind, rain, warming temperatures, snow and earthquakes.

They can also be triggered by skiers, snowmobiles, hikers, vibrations from machinery or construction. Avalanches Thousands of avalanches occur in Canada each year. Avalanche facts Avalanche safety What to do: During an avalanche Avalanche facts An avalanche occurs when a layer of snow collapses and slides downhill. Avalanches are caused by four factors: a steep slope, snow cover, a weak layer in the snow cover and a trigger. Roads and railway tracks may be rerouted to reduce risks.