Snow avalanche, three words that should not be forgotten in the mountains

If you enjoy doing crossword puzzles, you may have come across something like “mass of snow that collapses violently,” 4 letters. The answer is indeed “avalanche,” one of the worst nightmares for mountain lovers and winter sports enthusiasts.

The first snowfalls have already begun, and ski resorts are finalizing preparations for the 2019-2020 ski season. So let’s talk about what an avalanche is, its consequences, and what technological solutions exist to minimize its effects.

Things you should know about an avalanche

Although we provided an initial approximation in the introduction, a more accurate definition would be the one used by Godoy, Pedraza, and Carrasco (1). According to them, snow avalanches can be defined as “masses of snow that slide downhill through a rupture from a plane or weak point between layers of snow or snow-substrate layers.”

Generally, based on the surface area displaced, the type of rupture, and the transported snow, three types of avalanches are distinguished:

  • Slab avalanche occurs when a compacted and cohesive snow slab breaks abruptly, exhibiting weak adherence to the lower layer or the surface terrain. Within this type of avalanches, there are also wind slabs, as stated by the Cartographic and Geological Institute of Catalonia, which are formed by the action of wind in windward areas. Accumulated snow in this way causes most of the incidents.
  • Loose snow or powder snow avalanche typically starts from a point where dry snow (precipitated at temperatures well below 0ºC) or wet snow (snowfall at temperatures close to 0ºC) with little cohesion accumulates. They are common in steep slopes (between 17-35º) and exhibit an inverted V-shaped trajectory. They can be highly destructive, as the snow can reach speeds exceeding 60 km/h.
  • Wet snow avalanche is associated with late snowfalls or melting processes as atmospheric temperatures rise or snow is replaced by rain.

Are “avalanche” and “snowslide” the same thing?

In general, “avalanche” and “snowslide” can be considered synonymous, and throughout the rest of the article, we will use both terms interchangeably. However, it is worth noting the etymological difference between these words. After all, knowledge is power.

Regarding the word “avalanche,” there is some discussion about its true origin. Nevertheless, one of the most widely accepted theories associates it with the Basque language, directly related to the terms “lur” (earth) and “elur” (snow) (2).

On the other hand, the term “avalanche” is of French origin and is believed to have evolved from the word “valanche.” This term is also related to the Latin word “labes” (fall), which was later combined with “aval” (downhill). From an etymological perspective, “avalanche” does not specifically mention snow (3).

Why and how do snow avalanches occur?

Snow avalanches occur primarily because the layers of snow lose cohesion and homogeneity. This loss reduces the shear resistance of the snowpack, making it prone to sliding downhill.

Meteorology is one of the main modifying factors that affect the characteristics of ice crystals. However, other factors are also typically considered when assessing the stability of the snowpack, as shown in the following table (4, 5).

CategoríaFactorCondición crítica
TerrenoTerreno en la zona de inicioPendiente mayor de 28º
ExposiciónRadiación solarPendiente expuesta al sol
Orientación de la pendientePendientes a sotavento
Condiciones de la nieveNieve reciente0-10 cm peligro bajo
10-20 cm peligro moderado
20-40 cm peligro considerable
40-80 cm peligro alto
80-160 cm peligro muy alto
Estratificación de la nieveCapas intermedias débiles
Profundidad de la nieveSuelo liso > 30 cm
Suelo pedregoso > 60 cm
Temperatura de la nieve0 ºC
Condiciones meteorológicasVelocidad del viento5 m/s
Humedad relativaNieve húmeda
Temperatura del aire0 ºC y más alta o -10 ºC y más baja
Datos históricos de aludes de nieve¿Avalancha desde la última tormenta?No ha habido avalancha desde la última tormenta

Once we have an unstable snowpack and a sloping area, the final ingredient needed is the presence of a triggering factor. The sliding itself can be initiated by:

  • Natural causes, such as the accumulation of more snow, which can lead to the release of snow cornices due to gravity.
  • The presence of animals or people who, by stepping on or sliding over the snow, indirectly break the layers. For example, this was the trigger for a distressing avalanche that swept away several skiers on Tuc de la Llansa in the Aran Valley in February 2019.

Main impacts of a snow avalanche

As mentioned by McClung & Schaerer (6), snow avalanches, in addition to affecting small areas, occur in mountainous regions characterized by low population density. Compared to other events such as earthquakes or floods, the number of casualties caused by a snow avalanche is much smaller.

However, this circumstance is secondary for those individuals whose properties or personal safety are threatened by an avalanche.

Avalanches, in addition to causing fatalities and injuries, also have impacts on the following areas or activities:

  • Transportation routes and means, causing difficulties in free movement. This consequence entails a significant cost for public administrations and companies that need to restore services.
  • Construction, as buildings or infrastructure in ski resorts may be affected.
  • Tourism, as the number of visitors in avalanche-prone areas may decrease.

The following video shows the speed at which an avalanche poses a risk to several buildings and infrastructure.

How to Reduce the Risk of Snow Avalanches

Completely avoiding the possibility of a snow avalanche is nearly impossible. However, considering that avalanche-prone areas tend to be recurrent, preventive measures can be taken to reduce the risk of uncontrolled spontaneous avalanches.

In this regard, technologies such as drones, analysis of historical data, or the use of powerful simulation programs complement traditional techniques such as visual monitoring or the construction of protective structures.

However, the use of sensors, such as the ones offered in our Smarty Snow solution, is possibly one of the technologies that can provide the best results. Having real-time data on weather and snow conditions is essential for forecasting avalanche risk (7). Recently, we have also signed a distribution agreement with IAV Technologies SARL, which will allow us to incorporate the Flowcapt acoustic sensor into our monitoring system. This device measures the intensity of snow transport by the wind, a key parameter in the formation of slab avalanches.


Although a snow avalanche does not cause as much damage as an earthquake, it is a latent threat in mountainous areas. In fact, several dozen victims are recorded each year due to snow avalanches. This trend will also undergo modifications in the coming years due to global warming. The reason is that a warmer atmosphere contains more water vapor. And this high humidity, under the right conditions, can precipitate as snow and lead to record snowfalls.

Therefore, knowing which areas are prone to such events, taking necessary precautions, and monitoring weather conditions and snow conditions are crucial to ensure the safety and enjoyment of snow enthusiasts.

Sources consulted:

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