An avalanche awaits climbers. Snow avalanche: what it is, causes, dangerous periods, consequences, photos and videos. Avalanches of dense dry powder snow

An avalanche is a mass of snow that quickly slides down the side of a mountain. The snow that falls in the mountains throughout the year does not remain motionless: it slowly, imperceptibly to the eye, slides down under the weight of its own weight or collapses in avalanches and ice slides. An avalanche can be caused by a variety of reasons: the movement of climbers, the fall of a collapsed cornice, and various atmospheric phenomena.

All types of ice collapses pose a very serious danger, which is directly dependent on the size of the collapse. The speed of an ice slide is many times higher than the speed of an avalanche and approaches the speed of a falling stone. The climber is exposed to the greater danger, the closer he is to both the place of origin of the collapse and the center of its further movement. Ice collapses can occur from the movement of the ice itself, from overloading the ice mass, from the melting and softening of ice, etc. On an icefall, due to the softening of ice from heat and imbalance during the movement of the glacier, a serax or a separate block of ice may fall.

Due to overloading of the cornice hanging on the ridge, it can break off and fall down. On an icy slope, a piece of ice can break off from faults and, finally, sometimes, although extremely rarely, entire glaciers and icy mountain slopes collapse.

For example, in 1902, the entire northeastern slope of Mount Dzhimarai-Khokh (Kazbegi region) collapsed.

The ice rolled down 12 km. 36 people and about 1,800 heads of livestock died. The people's resort of Karma-don was overwhelmed.

The occurrence of avalanches depends on the amount and condition of the snow, on the base on which the snow lies, on various atmospheric conditions, on the influence of external forces on the snow cover (an impact from a fallen cornice, a rockfall, the movement of a group of climbers).

The snow mass is held on the slope by the adhesion force both between the snow layer and the base on which it lies, and by the internal adhesion between individual snowflakes. When this connection is broken, avalanches occur. Avalanches can slide wherever the slope steepness exceeds 20-25°.

Snow is divided into four main types: powdery, fallen at low temperatures or blown downwind by the wind; wet, fallen at high temperature or exposed to it after falling out; compacted snow; firn snow. Every type of snow can form an avalanche under the right conditions, but dry, powdery snow is most dangerous. The speed of avalanche movement depends on the base soil on which the snow lies, on the steepness of the slope, on the condition and size of the snow mass set in motion.

Under equally favorable conditions for avalanches, a powdery, dusty avalanche will move at the highest speed. At the upper end and along its sides, the avalanche moves much more slowly than in the middle.

Avalanches have many varieties, but we will only point out the main ones. The most common are avalanches from freshly fallen snow. They are in turn divided into dry and wet. Due to the insignificant connection of individual snow particles with each other and with their base, the occurrence of dry avalanches is usually sudden, and they can be caused very easily, especially on a smooth hard base (ice, firn, compacted snow). Most often they happen in winter.

Wet avalanches form from snow that falls at high temperatures or from snow lying on heavily sunlit slopes. The subsequent drop in temperature transforms the unstable wet snow into a harder snow mass, which reduces and even eliminates the risk of an avalanche.

On the windward side of the slope, powdery, dry snow, under the influence of wind and frost, becomes covered with a crust that has no connection with the snow and only rests on it. Violation of the integrity of this crust causes the entire snow layer located above the break in the crust to slide, and then a formation avalanche is formed.

Sometimes this crust is quite strong, it can withstand the weight of the body, giving the beginner the impression of a reliable cover, and in this case the threat of a formation avalanche may not be noticed. In addition, it is generally difficult to determine the place and moment of occurrence of such an avalanche.

All these types of avalanches belong to the category of surface avalanches. When snow, usually old, wet snow, slides in its entire mass, exposing the soil on which it lay, such an avalanche is called a ground avalanche. Typically this type of avalanche occurs in the spring.

You should not start the route immediately after a snowfall; it is better to wait until avalanches slide down or the snow thickens. In clear weather you need to wait two days, in foggy and cloudy weather - three to four days, in severe winter frost - up to six days. If possible, avoid snow couloirs, avalanche chutes, and slopes covered with deep, powdery or wet snow lying on an icy base.

In case of unreliable snow on steep slopes, it is best to climb head-on, without crossing such slopes or moving along them in zigzags. You need to cross an avalanche-dangerous slope as high as possible, staying away from each other and taking long strides in the footsteps of the person in front. If an avalanche has just occurred, you should try to strengthen yourself with an ice ax or run to the nearest edge of the avalanche. If a climber is carried down by an avalanche, he must remain vertical. If the speed of movement and the condition of the snow allow you to get out, you need to run away or get out from the middle of the avalanche to its edges, where the speed and force of the avalanche is less. I need to take off my backpack. If it was not possible to escape the avalanche, then the climber’s task is to prevent himself from being sucked into the snow, freeing his arms and legs and performing the movements of a swimmer. Face forward.

In a dry, dusty avalanche, close your mouth so as not to suffocate from the snow dust that fills your mouth and respiratory tract.

Snow avalanches are associated with mountainous terrain and pose serious risks to people, road infrastructure, bridges and buildings.


Climbers and lovers of mountain recreation often encounter this natural phenomenon, and, despite all precautions, an avalanche is an element from which there is practically no escape and no hope of survival. Where does it come from and what danger does it pose?

What is an avalanche?

According to explanatory dictionaries, the term "avalanche" comes from the Latin word labina, which means "landslide" . The phenomenon is a huge mass of snow that falls or slides down mountain slopes and rushes into nearby valleys and depressions.

To one degree or another, avalanches are common in all high-mountain regions of the world. In warmer latitudes, they usually occur in winter, and in those places where the mountains are covered with snow caps all year round, they can disappear in any season.


Snow in avalanches reaches a volume of millions of cubic meters and during the descent sweeps away everything in its path.

Why do avalanches occur?

Precipitation that falls in the mountains is retained on the slopes due to friction. The magnitude of this force is influenced by many factors, such as the steepness of the mountain peak and the moisture content of the snow mass. As snow accumulates, its weight begins to exceed the force of friction, causing large snow caps to slide down the mountain and collapse along its flanks.

Most often, avalanches occur on peaks with a slope angle of about 25–45 degrees. On steeper mountains, snow melting occurs only under certain conditions, for example, when it falls on an ice sheet. On flatter flanks, avalanches usually do not occur due to the impossibility of accumulating large snow masses.

The main reason for avalanches lies in the current climatic conditions of the region. Most often they occur during thaws or rains.

Sometimes earthquakes and rockfalls can trigger snow melting, and in some cases, a loud sound or small pressure, such as the weight of a human body, is enough to cause a disaster.

What types of avalanches are there?

There is a fairly extensive classification of avalanches, differing in volume, path, snow consistency and other characteristics. In particular, depending on the nature of the movement, there are wasp avalanches that descend over the entire surface of the mountain, flume avalanches that slide along hollows, and jumping avalanches that fly part of the way after encountering any obstacles.


According to their consistency, natural phenomena are divided into dry, which occur at low air temperatures due to low friction force, and wet, which are formed during thaws as a result of the formation of a layer of water under the snow.

How is avalanche risk calculated?

In order to identify the likelihood of avalanches, a risk classification system was created in Europe in 1993, in which each level is indicated by a flag of a certain format. Such flags are hung at all ski resorts and allow vacationers to assess the possibility of tragedy.

The system includes five risk levels depending on the stability of the snow. According to statistics, in the mountainous regions of Switzerland, most deaths are recorded already at levels 2 and 3, while in the French mountains the disaster leads to deaths at levels 3 and 4.

How dangerous is an avalanche?

Avalanches pose a danger to people due to their large mass. If a person finds himself under a thick layer of snow, he dies from suffocation or shock resulting from broken bones. Snow has low sound conductivity, so rescuers are not able to hear the victim’s scream and find him under the snow mass.


Avalanches can pose a threat not only to people stranded in the mountains, but also to nearby populated areas. Sometimes snow melting leads to catastrophic consequences and completely destroys the infrastructure of villages. So, in 1999, an avalanche destroyed the Austrian town of Galtür and caused the death of 30 of its residents.

In France there is such an organization as ANENA - the National Association for the Research of Snow and Avalanches. The most important task of this association is to reduce the number of avalanche victims among the population. And its very first tool in this matter is informing the broad masses of people, i.e. holding lectures, seminars, courses, etc. for everyone.
Summer is coming to an end and a new skiing season is just around the corner. In order to refresh your memory of some aspects of avalanche safety, I bring to your attention several translated articles from ANENA’s “Snow and Safety” materials.
As they say, prepare your sleigh in the summer...

The author of the articles, François Sivardière, is a teacher at the Technical School of Lausanne, and for 13 years he headed ANENA (the French National Association for Snow and Avalanche Research). Since 2007, teacher and consultant on avalanche prevention.

So, the first article

Misconceptions about Avalanches.

Snow boards are easy to recognize - FALSE!

If there has been no snowfall for a long time, then there is no danger - WRONG!

When there is little snow, there are no avalanches - WRONG!

A slight slope is safe - WRONG!

There are no avalanches in the forest - WRONG!

There are no avalanches in late spring and summer - FALSE!

No, snow planks are not easy to recognize!
Snow planks are at the root of approximately 80% of avalanche accidents. Such avalanches are easy to recognize: the avalanche lifts off along a line. If you look at such an avalanche from the side, it seems that a whole piece of the slope separates and begins to slide down.
Snow boards themselves, on the other hand, can be difficult to recognize. Contrary to some popular assumptions, the snow board is not particularly dense, or matte in color, or has any dull sound.
You've probably already heard about soft and hard snow boards. The fact is that boards can be formed from snow of very different qualities, from soft (the most dangerous because of its attractiveness for skiing) to very hard. Since the boards can consist of snow of very different qualities, it becomes obvious that they cannot be the same density, the same color, much less make the same sounds. In addition, the board can be hidden under a thin or thick layer of fresh snow. Therefore, when trying to identify a snow board, you should not rely on the appearance of snow on the surface.
A more reliable way to identify a snow board is to evaluate meteorological and topographic features. But this requires a lot of experience and excellent knowledge of the terrain of the area.

It is also worth remembering that snow boards are not only “windy” (that is, formed by the wind), but can also be formed in the complete absence of wind.
And finally, “wind” boards do not necessarily appear on leeward slopes, since the winds in the mountains tend to swirl in completely unimaginable ways. As a result, snow boards can easily form on slopes exposed to dominant winds.

The danger exists even if there has been no snowfall for a long time!
It is a known fact that usually the days following a snowfall are marked by increased avalanche activity. Can we conclude from this that if there has been no snowfall for a long time, then the risk of avalanches becomes low? Unfortunately no.

Newly fallen snow takes time to compact, stabilize, and bond with the underlying layer. And the colder it is, the slower these processes go. Thus, the instability of freshly fallen snow can last several days, a week or more. This is especially true for slopes on which the sun rarely shines: slopes with northern exposures. Thus, the three-day rule (usually considered to be “wait three days after the snowfall”) should not be taken literally. The formation of bonds in the snow cover is greatly slowed down by cold. Therefore, if the temperatures are low, you should wait more than three days. At the same time, it is extremely difficult to say with accuracy how many days after the snowfall the cover stabilizes.
In addition, let us again remember about wind boards, which are the basis for deadly avalanches and are formed under the influence of wind. To form such boards, snowfall is not needed at all: even a moderate breeze is enough to create an avalanche situation on the slopes. Finally, snow boards (wind-driven or not) can remain unstable for a long time after formation. Therefore, be careful and careful, even if there has been no snowfall for a long time!

Avalanches can occur even when there is little snow!
When it comes to assessing avalanche risk, you can often hear: “there is little snow, which means it is not dangerous.” This statement is false! The risk of avalanches does not directly depend on the depth of the snow cover.
Avalanche danger depends to a much greater extent on the quality of the bonds between snow crystals and the layers that make up the snow cover. If these connections are strong, then the risk is correspondingly lower. But if there is a slack (“weak layer”), then regardless of the height of the snow cover, an avalanche can occur. Don't be fooled by scant snow cover: statistics confirm that winters with little snow appear on lists of the deadliest.
A small thickness of snow cover (mainly in November-February) contributes to the formation of layers without strong bonds. The first layers tend to be a poor base for the snow that covers them later. No connections are formed between these layers. Therefore, the basis, i.e. the lower layers of snow cover are fragile and unreliable. They break easily and provoke avalanches.
In addition, when there is little snow, skiers look for places where there is more of it, i.e. in wind transfer zones. And snow blown by the wind is prone to melting, usually has poor connections with the substrate, and therefore is especially dangerous.
So, beware of avalanches, even when you think there is not enough snow!

Even a small slope can be dangerous!
Often when assessing a slope you can hear: “Everything is in order! The slope is not steep at all.”
It often happens that on non-steep slopes we lose our vigilance. As if avalanches can only occur on steep slopes. This is not the case, and reports describe numerous cases of avalanches on low-slope slopes. Therefore, be careful – even a small slope can be dangerous!

Consider, for example, a snow board 50 m long, 10 m wide and 20 cm thick. Although it seems to us that this is a small board, it nevertheless represents 100m3 or from 10 to 30 tons of snow (depending on the quality of the snow). This is a huge weight and volume, quite sufficient to completely cover and wall up a person. In addition, you can die from asphyxia or hypothermia even under a small layer of snow.
And even if the victim is not buried in the thickness of the snow, this mass can drag him a long distance and cause various injuries, often incompatible with life (compression by snow blocks, hitting rocks and trees, falling from cliffs or into a crack...).
So remain alert, even if you are going to ride on a small and gentle slope.

There are avalanches in the forest too!
Let's look at the impact forests have on avalanche danger. This sense of security that we experience in the forest is often false.

Forests have long and often been used as elements of protection for settlements, roads and structures. But the protection that forests can provide to a skier or snowboarder is not at all as reliable, if not even ephemeral. One might even say that only a forest so dense that it is impossible to drive through is reliable. What's the matter? In fact, trees have a dual influence on the stability of the snow cover: through their trunks, but also through their branches.

First, you need to distinguish between forests that retain deciduous cover in winter and forests of other trees. The branches of coniferous trees, which retain their needles even in winter, trap falling snow. When the mass of snow accumulated on a branch becomes too heavy, the branch bends and the snow falls off. If the temperatures are not too cold, then usually heavy caps of already transformed snow fall from the branches and accumulate under the trees. This snow is quite stable.
On the contrary, deciduous trees and larches lose their leaves and needles by winter. Their branches almost do not retain snow, and the snow cover that forms under them is very similar to the snow cover in open areas.
At the same time, the trunks act as anchors: they seem to nail the snow to the ground. Thus, the snow cushion rests on the trunks, which prevent it from sliding down the slope. However, this retention effect is highly dependent on the barrel frequency. That is, it works when the forest is really dense, but in this case it is quite difficult to ride through it.
Therefore, it should be understood that the forest cannot always prevent an avalanche from starting, nor can it stop an avalanche coming from above.
And being caught in an avalanche going through a forest is much more dangerous than in an open area! Collisions with trunks are almost impossible to avoid and are often fatal. Particularly dangerous can be clearings that seem so serene and dull our vigilance, but where the snow is not fixed in any way by the trunks, and when released, such an avalanche inevitably goes down into the forest with all the ensuing consequences.
So, let's remember that an avalanche can happen in the forest, especially if the forest is sparse and bare.

Avalanches occur in late spring and summer too!
When the winter ski season ends, many of us continue to go backcountry, hike, and climb. Thus, even in summer you can find snow in the mountains. This means there may be avalanches. Contrary to all stereotypes, they can be enjoyed regardless of the time of year. If there is a slope, and there is snow on the slope, then the risk of an avalanche automatically arises.
Naturally, this risk may be greater or less depending on weather conditions and terrain.
Two studies (Zuanon, 1995 and Jarry, Sivardière, 2000) show that during the so-called “off-season”, from May 1 to December 15, avalanche casualties also occur. In France, for example, statistics say that out of 30 people killed in avalanches per year, twenty percent died in the specified non-winter period. This is not a marginal phenomenon at all, but a reality that cannot be neglected. In 1997, 8 people died in France between July and September, accounting for a third of all avalanche deaths that year.
Knowing this, do not neglect your winter habits in the summer: monitor the forecast and the situation on the ground, have a full set of sensor-shovel-probe, be vigilant and do not hesitate to turn back or bypass questionable areas.

There are several classifications of avalanches, for example:

• · According to the shape of the beginning of the avalanche movement.
• · According to the nature of the avalanche movement.
• · By volume.
• · According to the avalanche relief and the avalanche path (wasps, flume avalanche, jumping avalanche).
• · According to the consistency of the snow (dry, wet and wet avalanches).

In this case, according to the form of the onset of movement, avalanches are divided into:

• · Avalanches from the line (“snow boards”, snow-ice, ice).
• · Avalanches from a point (dry and wet).

Avalanches are classified according to the nature of their movement:

• · Osovy - landslides over the entire surface of the slope.
• · Jumping - when various obstacles (ledges, moraines, etc.) are encountered on the path of the avalanche. When encountering such an obstacle, the avalanche jumps and flies part of the way.
• · Trough - in this case, the avalanche moves along a natural trough-like base (depressions, couloirs, etc.)

Dry avalanches, as a rule, occur due to the low adhesion force between the recently fallen (or transported) mass of snow and the underlying ice crust. The speed of dry avalanches is usually 20-70 m/s (up to 125 m/s, which is 450 km/h, some sources limit the speed of such avalanches to 200 km/h) with a snow density of 0.02 to 0.3 g /cm. At such speeds, an avalanche from dry snow can be accompanied by the formation of a snow-air wave, causing significant destruction. The pressure of the shock wave can reach values ​​of 800 kg/m². The most likely conditions for this type of avalanche to occur are when the temperature is low.

Wet avalanches usually occur against the backdrop of unstable weather conditions; the immediate cause of their occurrence is the appearance of a water layer between layers of snow of different densities. Wet avalanches move much slower than dry ones, at a speed of 10-20 m/s (up to 40 m/s), but have a higher density of 0.3-0.4 g/cm³, sometimes up to 0.8 g/cm³. A higher density causes the snow mass to quickly “set” after stopping, which complicates rescue operations.

So-called “snow boards” can form when an ice crust grows on the surface of a snow mass. The crust appears as a result of the action of the sun and wind. Under such a crust, a modification of the snow mass occurs, turning into grain, over which a more massive upper layer can begin to slide. Several thawing-freezing cycles can lead to the formation of multilayer formations of this kind. The provoking factors for the initiation of avalanches of this type are snowfall at low temperatures. The additional weight of the snow layer is added to the stresses in the upper layer that arose due to colder temperatures, which leads to the separation of the “snow board”. The speed of such avalanches reaches values ​​of the order of 200 km/h.

The cause of snow-ice avalanches is the accumulation of significant masses of snow and ice in the mountains in appropriate places. At a certain moment, a collapse of these masses occurs, rushing down at a significant speed. Often such avalanches are of the “line avalanches” and “jumping” types. The density of an avalanche can reach 800 kg/m³. If, according to local conditions, the amount of snow in an avalanche is small, the result is an ice avalanche consisting almost entirely of pieces of ice. Such an avalanche can destroy everything in its path. Snow and ice avalanches are the most unpredictable; they can occur at different times of the day and year.

During the descent process, it is not necessary to preserve the type of avalanche; it can change from one to another and be combined.

In European countries, since 1993, there has been a system of classification of avalanche risks, indicated by corresponding flags, hung, in particular, in crowded places at ski resorts (this classification is used, in particular, in Russia):

Table

In the French mountains, most avalanche fatalities occur at risk levels rated between 3 and 4, and in Switzerland between 2 and 3.

avalanche disaster danger mountain

- snow masses falling from the slopes of mountains under the influence of gravity.

Snow accumulating on mountain slopes, under the influence of gravity and weakening of structural bonds within the snow column, slides or crumbles from the slope. Having started its movement, it quickly picks up speed, capturing more and more snow masses, stones and other objects along the way. The movement continues to the flatter sections or the bottom of the valley, where it slows down and stops.

Such avalanches very often threaten populated areas, sports and health resort complexes, railways and highways, power lines, mining facilities and other economic structures.

Factors in the formation of snow avalanches

Avalanches form within the avalanche source. An avalanche source is a section of a slope and its foot within which an avalanche moves. Each source consists of three zones: origin (avalanche collection), transit (trough), avalanche stopping (alluvial cone).

Avalanche-forming factors include: height of old snow, condition of the underlying surface, increase in freshly fallen snow, snow density, snowfall intensity, snow subsidence, snowstorm redistribution of snow cover, air and snow temperature.

Avalanches form when there is sufficient snow accumulation and on treeless slopes with a steepness of 15 to 50°. At a slope of more than 50°, the snow simply falls off and conditions for the formation of a snow mass do not arise. Optimal situations for avalanches occur on snow-covered slopes with a steepness of 30 to 40°. There, avalanches occur when the layer of freshly fallen snow reaches 30 cm, and for old (stale) snow a cover 70 cm thick is required. It is believed that a smooth grassy slope with a steepness of more than 20° is avalanche dangerous if the snow height on it exceeds 30 cm. With increasing slope steepness the likelihood of avalanches increases. Shrub vegetation is not an obstacle to the gathering.

The best condition for the snow mass to begin to move and gain a certain speed is the length of the open slope from 100 to 500 m.

Much depends on the intensity of the snowfall. If 0.5 m of snow falls in 2-3 days, then this usually does not cause concern, but if the same amount falls in 10-12 hours, then snowfall is quite possible. In most cases, the snowfall intensity of 2-3 cm/h is close to critical.

Wind also plays a significant role. So, in a strong wind, an increase of 10-15 cm is enough, and an avalanche can already occur. The average critical wind speed is approximately 7-8 m/s.

One of the most important factors influencing the formation of avalanches is temperature. In winter, when the weather is relatively warm, when the temperature is close to zero, the instability of the snow cover increases greatly, but quickly passes (either avalanches occur or the snow settles). As temperatures drop, periods of avalanche danger become longer. In spring, with warming, the likelihood of wet avalanches increases.

Damaging ability of snow avalanches

The lethality varies. An avalanche of 10 m3 already poses a danger to humans and light equipment. Large avalanches are capable of destroying capital engineering structures and forming difficult or insurmountable blockages on transport routes.

Speed ​​is one of the main characteristics of a moving avalanche. In some cases it can reach 100 m/s.

The ejection range is important for assessing the possibility of hitting objects located in avalanche zones. A distinction is made between the maximum emission range and the most probable, or long-term average. The most probable ejection range is determined directly on the ground. It is assessed if it is necessary to place structures in the avalanche zone for a long period. It coincides with the boundary of the avalanche fan.

The frequency of avalanches is an important temporal characteristic of avalanche activity. A distinction is made between average long-term and intra-annual recurrence rates. The first is defined as the frequency of avalanches on average over a long-term period. Intra-annual frequency is the frequency of avalanches during the winter and spring periods. In some areas, avalanches can occur 15-20 times a year.

Avalanche snow density is one of the most important physical parameters on which the impact force of the snow mass, the labor costs for clearing it, or the possibility of movement on it depend. It is 200-400 kg/m 3 for dry snow avalanches, and 300-800 kg/m 3 for wet snow.

An important parameter, especially when organizing and conducting emergency rescue operations, is avalanche flow height, most often reaching 10-15 m.

Potential avalanche period is the time interval between the first and last avalanches. This characteristic must be taken into account when planning the mode of human activity in a dangerous area. It is also necessary to know the number and area of ​​avalanche foci, the start and end dates of the avalanche period. These parameters are different in each region.

In Russia, such natural disasters most often occur in the Kola Peninsula, the Urals, the North Caucasus, the south of Western and Eastern Siberia, and the Far East. Avalanches on Sakhalin have their own characteristics. There they cover all altitude zones - from sea level to mountain peaks. Descending from a height of 100-800 m, they cause frequent interruptions in train traffic on the Yuzhno-Sakhalinsk Railway.

In the vast majority of mountainous regions, avalanches occur annually, and sometimes several times a year.

Avalanche classes

Depending on the factors of avalanche formation, they are divided into four classes:

• The immediate cause of the occurrence is meteorological factors.
• Arising as a result of the combined action of meteorological factors and processes occurring inside the snow layer during melting.
• They arise exclusively as a result of processes occurring inside the snow layer.
• As a result of an earthquake, human activity (explosions, low-altitude jet flights, etc.).

The first class, in turn, is divided into three types: caused by snowfalls, blizzards and a sharp drop in temperature.

The second class is divided into four types: those associated with radiation thaws (on the southern slopes of the mountains), spring thaws, rains and thaws during the transition to positive temperatures.

The third class consists of two types: avalanches associated with the formation of a layer of deep frost and resulting from a decrease in the strength of the snow cover under prolonged load.

By degree of impact Avalanches are divided into economic activities and the natural environment:

• on spontaneous(especially dangerous), when their collapse causes significant material damage to populated areas, sports and sanatorium-resort complexes, railways and highways, power lines, pipelines, industrial and residential buildings;
• dangerous phenomena- avalanches that impede the activities of enterprises and organizations, sports facilities, and also threaten the population and tourist groups.

By degree of repeatability are divided into two classes - systematic And sporadic. Systematic ones go every year or once every 2-3 years. Sporadic - 1-2 times per 100 years. It is quite difficult to determine their location in advance. There are many known cases where, for example, in the Caucasus, villages that had existed for 200 and 300 years suddenly found themselves buried under a thick layer of snow.

Protection against snow drifts, blizzards, blizzards, avalanches

Snow drifts occur as a result of heavy snowfalls and blizzards, which can last from several hours to several days. They cause disruption of transport communications, damage to communication and power lines, and negatively affect economic activity.

Snow drifts are accompanied by sudden changes in temperature and cause icing- covering various surfaces and objects with ice or wet snow. As a result, electrical wires and communication lines break, poles, masts and supports break, and transport contact networks are disrupted.

When receiving information about heavy snowfalls, it is necessary to stock up on food, water, emergency lighting and heating equipment and prepare for possible isolation from the outside world for several days.

In rural areas and single-story houses, it is also necessary to have entrenching tools (shovels, crowbars, etc.) at the ready to periodically clear snow from doors, windows and the roof, providing air access to the house and preventing possible collapse of the roof under the weight of fallen snow.

Snow drifts are especially dangerous when avalanches from the mountains (Fig. 1). Snow falling in the mountains accumulates on the slopes near the peaks, forming huge snowdrifts, which, under certain conditions, lose stability and rush down in the form of landslides and avalanches. A snow avalanche causes significant damage to industrial and agricultural facilities, railways and highways, power lines, buildings and structures and often leads to casualties. The power of the avalanche is amazing. The impact force of an avalanche varies from 5 to 50 tons per square meter (for example, an impact of 3 tons per meter causes the destruction of wooden buildings, and 10 tons per meter uproots trees). The speed of avalanches can vary from 25 to 75 m/s.

Rice. 1. Snow avalanche

Avalanche protection can be passive or active. With passive protection, avoid using avalanche-prone slopes or install barrier shields. With active protection, avalanche-prone slopes are bombarded, causing small, harmless avalanches and thus preventing the accumulation of critical masses of snow.

When caught in a snow avalanche, you must take all measures to get to its surface. To do this, you need to free yourself from the bulky load and move up, making movements like when swimming. Then you need to pull your knees towards your stomach, and with your hands clenched into fists, protect your face from the snow mass. When the avalanche stops moving, you must first try to free your face and chest so that you can breathe, and then take other measures to free yourself from snow captivity.

Blizzard- This is the transfer of snow by strong winds over the surface of the earth. There are drifting snow, blowing snow and general snowstorm. Drifting snow and blowing snow are phenomena where snow is lifted by the wind from the snow cover, occurring without snow falling from the clouds.

Drifting snow observed at low wind speeds (up to 5 m/s), when most snowflakes rise only a few centimeters.

Blizzard observed at high wind speeds, when snowflakes rise to 2 m or higher, as a result of which atmospheric visibility deteriorates, sometimes decreasing to 100 m or less.

Blowing snow and drifting snow only cause a redistribution of previously fallen snow.

General, or upper, snowstorm represents snowfall with a fairly strong (usually over 10 m/s) wind and is accompanied by a significant increase in snow cover throughout the entire area covered by the blizzard.

When there is strong wind and low temperature, the blizzard is locally called blizzard(mainly in the Asian part of Russia).

Blizzard- another local (in a number of regions of Russia) name for a blizzard with strong winds, occurring mainly in flat, treeless areas when cold air invades.

When it comes to blizzard, then it means a snowstorm with howling wind and blinding snow. According to the official classification, a storm can be considered if the wind speed exceeds 55 km/h and the temperature drops below -7 °C. If the wind speed reaches 70 km/h and the temperature is below -12 °C, then we are dealing with a strong snow storm.

The main damaging factor during snow drifts, during a blizzard, blizzard, and blizzard is the effect of low temperatures, causing frostbite, sometimes leading to freezing of people.

In the event of an immediate threat of such a natural disaster, the population is notified, the necessary forces and means are put on alert, road and utility services are put on alert, and radio broadcasting centers are switched to round-the-clock operation.

Since a snowstorm or blizzard can last for several days, it is necessary to create a supply of food, water, fuel in the house in advance, and prepare emergency lighting. During a blizzard, blizzard or blizzard, you can leave the premises only in exceptional cases and not alone.

When using a car, travel only on main roads. In the event of a sharp increase in wind, it is advisable to wait out the bad weather in or near a populated area. If the machine breaks down, do not move out of sight from it. If possible, the car should be installed with the engine in the windward direction. From time to time you need to get out of the car and shovel the snow so as not to be buried under it. In addition, a car not covered with snow is a good reference point for the search team. The car engine should be periodically warmed up to prevent it from “defrosting”. When warming up the car, it is important to prevent exhaust gases from “flowing” into the cabin (body, interior). For this purpose, it is necessary to ensure that the exhaust pipe is not covered with snow.

Blizzards and blizzards pose a particular danger to people caught on the road far from human habitation. Snow-covered roads and loss of visibility cause complete disorientation of the area.

To guide people suddenly caught in the snow, milestones and other signs are installed along the roads, and in some mountainous and northern regions, ropes are stretched (on paths, roads, from building to building), by holding on to which people could get into their homes and others. premises.

However, in open areas where there are no signs, it is necessary to find shelter from wind, snow and cold as quickly as possible or build it out of snow. To do this, a tunnel should be dug in a snowdrift 1.5-2 m high. Then expand the tunnel dead end to the required size. You can make a platform for a bed out of snow. It should be 0.5 m above the floor level. A hole for ventilation is carefully made in the roof of the cave. The entrance is covered with fabric or a snow block. If the snow is not deep enough, you can make small blocks from it, from which you can build a wall - a barrier 1.5-2 m high. The barrier should be positioned perpendicular to the direction of the wind. If there is a raincoat or other fabric, it is reinforced with snow blocks.

After the shelter is built, under no circumstances should it be filled in, as there is a danger of freezing. Exposure to freezing temperatures, especially if the weather is windy and humid, carries a constant risk of hypothermia and frostbite.

Hands and feet require special attention. They are located on the periphery of the blood circulation, and therefore can cool very quickly. Keep your hands protected, warming them under your arms or between your thighs if necessary. If you feel your toes getting cold, warm them up by moving them effectively and rubbing them with your hands.

The risk of frostbite requires special vigilance as it can occur unnoticed. Therefore, frequently check the condition of exposed parts of the body, especially the face, including the nose. If you feel your skin tingling or feel numb, you should immediately and naturally warm up those areas of your body. The best method of warming up is with your body heat (for example, hiding your hands under your arms).

The main types of work during a snowstorm or blizzard are searching for missing people, providing first aid to victims, clearing roads and areas around buildings, providing assistance to stranded drivers, and eliminating accidents on utility and energy networks.

All work during a snowstorm or blizzard must be carried out only in groups of several people. At the same time, all rescuers must be in sight in order to come to each other’s aid at any moment.