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Snow avalanches. Avalanche - what is it? Causes and consequences of avalanches Avalanches of monolithic ice and ice-snow formations

In France, there is such an organization ANENA - the National Association for the Study 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 the new skiing season is just around the corner. To brush up on some aspects of avalanche safety, here are some translated articles from ANENA's Snow and Safety.
As they say, prepare the sleigh in the summer ...

Author of articles François Sivardière is a teacher at the Technical School of Lausanne, for 13 years he headed ANENA (French National Association for the Study of Snow and Lavigne). Since 2007, he has been an avalanche victim prevention teacher and consultant.

So the first article

Misconceptions about Avalanches.

Snow boards are easy to recognize - WRONG!

If there has not been snowfall for a long time, then there is no danger - WRONG!

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

A small slope is safe - WRONG!

There are no avalanches in the forest - WRONG!

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

No, snow boards are not easy to recognize!
Snow boards underlie about 80% of avalanches. Such avalanches are easy to recognize: the avalanche breaks off along a line. If you look at such an avalanche from the side, it seems that a whole piece of the slope is separated and begins to slide down.
The snow boards themselves, on the contrary, can be difficult to recognize. Contrary to some common assumptions, the snow board does not differ in any particular density, or matte color, or some dull sound.
You've probably heard of soft and hard snowboards by now. 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 boards can consist of snow of very different qualities, it becomes obvious that they cannot be of the same density, not of the same color, much less produce 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 snowboard, do not rely on the appearance of snow on the surface.
A more reliable way to identify a snowboard 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 "wind" (that is, formed by the wind), but can also form in the absence of wind.
And finally, "wind" boards do not necessarily appear on the lee slopes, since the winds in the mountains tend to swirl in a completely unthinkable way. 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.

Freshly fallen snow takes time to pack, 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 for several days, a week or more. This is especially true for slopes on which the sun rarely shines: the slopes of northern exposures. Thus, the rule of three days (it is usually said that "one must wait three days after a snowfall") is not to be taken literally. The formation of bonds in the snow cover is strongly slowed down by cold. Therefore, if there are low temperatures, then 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's remember again about wind boards, which are the basis for deadly avalanches and are formed under the influence of wind. For the formation of 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 or not) can remain unstable for a long time after formation. Therefore, be careful and careful, even if there has not been a snowfall for a long time!

Avalanches can come down even when there is little snow!
When it comes to assessing avalanche risk, you can often hear: "little snow means not dangerous." This statement is false! The risk of avalanches does not depend directly on the height of the snow cover.
Avalanche hazard is much more dependent on the quality of the bonds between the 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 come down. Don't be fooled by the meager snow cover: statistics confirm that winters with little snow are among the deadliest.
A small thickness of snow cover (mainly in November-February) contributes to the formation of layers without strong bonds. The first layers are usually a poor base for the snow that covers them later. There are no links between these layers. Therefore, the basis, i.e. the lower layers of the 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 zones. And snow swept by the wind is prone to melting, usually has poor connections with the substrate, which means it is especially dangerous.
So, beware of avalanches, even when it seems to you that there is little 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 gentle slopes we lose our vigilance. As if avalanches can only descend on steep slopes. This is not the case, and reports describe numerous cases of avalanches on slopes with a slight slope. Therefore, attention - even a small bias can be dangerous!

Consider, for example, a snowboard 50m long, 10m wide and 20cm 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 immure a person. In addition, it is possible to 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 it a long distance and cause various injuries, often incompatible with life (squeezing with snow blocks, hitting stones and trees, falling from rocks or into a crack ...).
So stay alert even if you are going to ride on a small and not steep slope.

There are also avalanches in the forest!
Let's take a look at the impact forest has on avalanche danger. This sense of security 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 ephemeral. It can even be said that only a forest so dense that it is impossible to drive through it is reliable. What is the matter here? In fact, trees have a dual effect on snowpack stability: with their trunks, but also with their branches.

To begin with, it is necessary to distinguish between forests that retain deciduous cover in winter and forests of other trees. The branches of coniferous trees, which retain their needles in winter, hold back the 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. Such snow is quite stable.
On the contrary, deciduous trees and larches lose their leaves and needles by winter. Their branches hardly 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 pin the snow to the ground. Thus, the snow cushion rests on the trunks, which prevent it from sliding down the slope. However, this delay effect is highly dependent on the frequency of the trunks. 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 can not always prevent the start of an avalanche, nor stop an avalanche coming from above.
And to be in an avalanche going through the forest is much more dangerous than in an open area! The barrels are nearly impossible to dodge, and are often fatal. Clearings can be especially dangerous, which seem so serene and dull our vigilance, but where the snow is not fixed in any way by trunks, and when detached, 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 descend in late spring and summer too!
When the winter skiing season ends, many of us continue to go backcountry, hiking and mountaineering. Thus, even in summer in the mountains you can meet snow. So, there may be avalanches. Contrary to all stereotypes, they can go regardless of the season. If there is a slope, and there is snow on the slope, then the risk of an avalanche automatically arises.
Naturally, this risk can be greater or less depending on weather conditions and topography.
Two studies (Zuanon, 1995 and Jarry and Sivardière, 2000) show that during the so-called off-season, from 1 May to 15 December, avalanche casualties also occur. In France, for example, statistics say that out of 30 avalanche deaths per year, twenty percent died during the specified non-winter period. This is not at all a marginal phenomenon, but a reality that cannot be neglected. In 1997, between July and September, 8 people died in France, which accounted for a third of all avalanche victims that year.
Knowing this, do not neglect your winter habits in summer: follow the forecast and the situation on the ground, have a full set of sensor-shovel-sonde, be vigilant and do not hesitate to turn back or bypass questionable areas.

According to the nature of the movement and depending on the structure of the avalanche focus, the following three types are distinguished:

  • - tray,
  • - wasp,
  • - jumping.

The trough moves along a specific drain channel or avalanche chute.

Osovaya is a snow landslide that does not have a specific runoff channel and slides across the entire width of the site.

The jumping one arises from the flumes where there are sheer walls or sections with a sharply increasing steepness in the drain channel. Having met a steep ledge, the avalanche breaks off the ground and continues to move through the air in the form of a huge jet. Their speed is especially great.

Depending on the properties of snow, avalanches can be:

  • - dry,
  • - wet
  • - wet.

Dry avalanches are usually caused by a low cohesive force between the recently fallen (or transferred) 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 that produces significant damage. The pressure of the shock wave can reach values ​​of 800 kg / m². The most likely conditions for the occurrence of this type of avalanches are when the temperature is low.

Wet avalanches occur in spring as a result of an increase in the weight of the snow mass during warm winds (foehns) in the high-mountain zone, during drizzling rains in the upper reaches of snowy valleys, and also during snowfall at zero ambient temperature. Wet avalanches are distributed mainly in the high mountain zone.

Wet avalanches usually occur against the background of unstable weather conditions, the direct cause of their descent 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 a quick "grasping" of the snow mass after a stop, which makes it difficult to carry out rescue operations.

According to the nature of the sliding surface, the following types are distinguished:

  • - reservoir, when the movement is carried out on the surface of the underlying layer of snow;
  • - unpaved - the movement occurs directly on the surface of the soil.

According to the degree of impact on economic activity and the natural environment, avalanches are divided into:

  • - spontaneous (especially dangerous), when their descent causes significant material damage to settlements, sports and sanatorium complexes, railways and roads, power lines, pipelines, industrial and residential buildings,
  • - dangerous phenomena - avalanches that impede the activities of enterprises and organizations, sports facilities, as well as threatening the population and tourist groups.

According to the degree of repetition, they are divided into two classes

  • - systematic
  • - sporadic.

Systematic descend every year or once every 2-3 years. Sporadic - 1-2 times in 100 years. It is rather difficult to determine their place in advance. Many cases are known when, for example, in the Caucasus, villages that existed for 200 and 300 years suddenly found themselves buried under a thick layer of snow.

Many dangers lie in wait for climbers, snowboarders and skiers. But the most inexorable and unpredictable of them is snow avalanches. What are they like? Below is a detailed classification of avalanches.

According to Tushinsky

Back in 1949, Professor Georgy Tushinsky proposed a typology of snow avalanches based on differences in the specifics of the movement paths.

The geographer divided the types of snow masses descending from the mountains into:

  1. Tray. They move along a strictly fixed vector from glacial troughs, as well as from funnels formed as a result of the destruction of rocks.
  2. Basics. When a gap forms in the layer of snow and part of the mass slides down a flat slope, on which there are no erosion cuts or furrows.
  3. Jumping. There are sheer cliffs on the way of the site, from which the snow slides into free fall.

By the nature of the movement and the structure of the mass

A dust avalanche is formed from dry snow. In the process of movement, the structure of the mass is destroyed and creates a cloud of snow dust. The speed of snow avalanches of this type can reach 250 km/h. It is the most dangerous and destructive.

The same classification of avalanches established the presence of so-called "snow slabs". They are formed from a layer of fine-grained dry snow with a density of up to 400 kg per cubic meter, under which there is a less dense snow mass. Hollow areas are formed under the plates, which destroy the top layer and provoke its subsidence.

When the imbalance reaches a critical point, a stepped separation line is formed, perpendicular to the surface of the mass, and collapse occurs over a large area, the speed of which can reach 200 km / h.

There is also an "avalanche from a point." It is formed from wet snow in the form of a huge drop coming off a rocky ledge. This is due to the heating of the rocks, as a result of which the lower layer of the mass is fed with moisture, becomes heavier and begins to shift. Most snow avalanches of this type can be observed in spring. The speed of their movement does not exceed 120 km / h.

In the summer season, hydro-driven avalanches often appear, in which masses move that resemble mudflows in composition: they contain a mixture of stones, water, soil and snow.

Due to the occurrence

According to this criterion, in 1984 V. Akkuratova proposed the following typology:

  • snow avalanches

They are formed from the redistribution of the upper layer due to mass transfer during a snowstorm. Accumulations of snow grains carried by the wind are deposited in the depressions of the relief. The rate of formation of a snowstorm layer depends on the structure of the relief, as well as on the speed of the snowstorm.

  • advection

They are formed as a result of water infiltration into a layer of snow, due to which its structure is destroyed and the lower layer thaws and the bonds between dense accumulations of snowflakes break.

  • Avalanches from dry "young" snow

In the process of intense snowfall, a fresh layer is formed on the surface of the mass, consisting of crystals with a density of not more than 200 kg per 1 cubic meter.

The stability of this structure depends on the strength of adhesion, as well as on the area of ​​contact with the "old" layer and on the rate of accumulation of dry crystals.

  • Avalanches due to metamorphism

Due to the deformation of the structure of ice particles and the bonds between them, snow recrystallization occurs, as a result of which loose layers appear in the upper cover. This leads to an avalanche.

  • Insolation

Snow absorbs solar energy, under the influence of which it begins to move. The movement speed is relatively low.

  • mixed

The movement of snow masses occurs due to an increase in air temperature with the simultaneous accumulation of solar energy in the thickness of the snow.

  • Avalanches triggered by snow compression

They are formed as a result of overvoltages arising from an increase in the density of snow masses caused by a strong decrease in air temperature.

Classifications by strength and level of danger

According to the volume and approximate weight of the moving layer, avalanches can be divided into five varieties:

  1. A catastrophe capable of destroying a settlement or having a destructive effect on a vast forest area (more than 4,000 km²);
  2. Sliding of minor accumulations of snow that are not capable of harming a person;
  3. An avalanche that can destroy an area of ​​forest up to 4,000 km², as well as cause damage to buildings, vehicles and equipment;
  4. A slight shift in the snow mass that can harm a person;
  5. A medium-sized avalanche capable of breaking trees, damaging vehicles and buildings.

If we talk directly about the danger of an avalanche for a person, then it is customary to evaluate it on a 5-point scale:

The danger is minor. There is a minimal chance of snowfall, but in general the surface is dense and stable. Conditions for holding events are quite reliable.

The formation of an avalanche is possible only in critical areas of the relief, subject to additional pressure on the slope by the movement of several athletes along it. In quiet areas, slopes up to 50 degrees can be loaded. It is advisable not to lay routes through problem areas with an inclination angle of more than 45 degrees.

Average level of danger. At some points on the slope, there is a decrease in density and slight destabilization. On steep terrain, the risk of an avalanche is increased. Spontaneous shift of snow masses is unlikely.

Events are allowed if the organizers take into account the structure of the relief and the peculiarities of the conditions at the sites. It is allowed to stress normal slopes with an angle of up to 40 degrees. On areas with problematic relief, loads at an angle of up to 35 degrees are permissible.

Increased danger. On most slopes, snow masses are unstable and have a loose structure. The probability of an avalanche formation is high. The most dangerous points are steep slopes. Spontaneous descent of several avalanches of medium strength and single descents of large volumes of snow are expected. Events are allowed, but only if their participants are only experienced athletes with sufficient knowledge of avalanche science, familiar with the geography of the region, and not planning to go to high-risk areas. On most routes, the movement of groups of athletes is prohibited. Permissible load on slopes forming an angle of up to 35° in normal areas and up to 30° in hazardous areas.

The snow cover is not compacted and unstable in the vast majority of areas. The probability of an avalanche coming down is high even with a slight load on the slope surface. The movement of groups of athletes is prohibited. Only single events are allowed.

Access to the route is allowed only for professional athletes who are perfectly familiar with the geography of the area, who have impeccable knowledge of avalanche science and good intuition, who are ready to return to the base at the slightest suspicion. Loading in normal and potentially hazardous areas is allowed on slopes up to 25° and 20° respectively.

catastrophic danger. Snow masses are mobile and unpredictable. Events are strictly prohibited. Avalanches of large volumes are coming down on all slopes, regardless of the degree of inclination.

Mountains are undoubtedly one of the most beautiful and fascinating panoramas of the Earth. Many strive to conquer the majestic peaks, not fully realizing how harsh such beauty is. That is why, deciding on such a brave step, extreme people face difficulties in all their manifestations.

The mountains are a rather dangerous and complex terrain, in the expanses of which there is a constant mechanism of gravity, so the destroyed rocks move and form plains. Thus, the mountains eventually turn into small hills.

In the mountains, danger can always await, so you need to undergo special training and be able to act.

Definition of Avalanches

Snow avalanches are one of the most devastating, dangerous destructive phenomena of nature.

An avalanche is a rapid, sudden, minute process of moving snow with ice, occurring under the influence of gravity, water circulation and many other atmospheric and natural factors. Such a phenomenon most often occurs in the winter/spring period, much less often in summer/autumn, mainly at high altitudes.

It is always worth remembering that the avalanche is primarily a harbinger of weather conditions. Hiking in the mountains in bad weather: snowfall, rain, strong wind - is quite dangerous.

Most often, an avalanche occurs, lasting about a minute, while passing a distance of about 200–300 meters. It is extremely rare to hide or run away from an avalanche, and only if it became known about it at least 200–300 meters away.

The avalanche mechanism consists of a sloping slope, an avalanche body and gravity.

Sloping slope

The level of the slope, the roughness of its surface greatly affect the avalanche risk.

A slope of 45–60° is usually not dangerous, as it gradually unloads during snowfalls. Despite this, such places under certain weather conditions can create avalanche accumulations.

Snow will almost always fall from a slope of 60–65°, and this snow can linger on convex sections, creating dangerous blowouts.

Slope 90 ° - the collapse is a real snow avalanche.

avalanche body

Formed from accumulations of snow during an avalanche, it can crumble, roll, fly, flow. The type of movement directly depends on the roughness of the lower surface, the type of snow accumulation, and swiftness.

Types of avalanches according to the movement of snow accumulations are divided:

  • to streaming;
  • cloudy;
  • complex.

Gravity

It acts on the body on the surface of the Earth, is directed vertically downwards, being the main mobile force that contributes to the movement of snow accumulations along the slope to the foot.

Factors affecting the occurrence of an avalanche:

  • type of matter composition - snow, ice, snow + ice;
  • connectivity - loose, monolithic, reservoir;
  • density - dense, medium density, low density;
  • temperature - low, medium, high;
  • thickness - thin layer, medium, thick.

General classification of avalanches

Avalanches of powdered, dry recent snow

The convergence of such an avalanche usually occurs during heavy snowfall or immediately after it.

Powder snow is called fresh, light, fluffy snow, consisting of tiny snow flakes and crystals. The strength of snow is determined by the rate of increase in its height, the strength of the connection with the ground or previously fallen snow. It has a fairly high fluidity, which makes it possible to easily flow around a variety of obstacles. In different cases, they can reach speeds of 100–300 km / h.

Avalanches created by snowstorms

Such a convergence is the result of the transfer of snow by a blizzard. Thus, the snow is transferred to the mountain slopes and negative landforms.

Avalanches of dense dry powder snow

They arise from snow a week old or more, which during this time is pressed, becomes much denser than freshly fallen. Such an avalanche moves more slowly, partially turning into a cloud.

landslide avalanches

They grow after the collapse of snow cornice blocks, which set in motion a large amount of snow.

Dust avalanches

An avalanche is characterized by a huge cloud or a thick layer of snow on trees and rocks. Created when dry, powdery recent snow melts. A dust avalanche sometimes reaches a speed of 400 km/h. Risk factors are: snow dust, strong shock wave.

Formation avalanches

They arise through the descent of layered snow, reach a speed of 200 km / h. Of all the snow avalanches are the most dangerous.

Avalanches from hard sheet snow

A stream is formed by the descent of solid layers of snow over a weak, loose layer of snow. They consist mainly of flat snow blocks resulting from the destruction of dense formations.

Soft plastic avalanches

Snow flow is formed by the descent of a soft layer of snow on the underlying surface. This type of avalanche is created from wet, settled, dense or moderately cohesive snow.

Avalanches of monolithic ice and ice-snow formations

At the end of winter, snow deposits remain, which, under the influence of external factors, become much heavier, turning into firn, eventually turning into ice.

Firn is snow cemented by frozen water. It is formed during temperature drops or fluctuations.

Complex avalanches

Consist of several parts:

  • flying cloud of dry snow;
  • a dense stream of formation, loose snow.

They arise after a thaw or a sharp cold snap, which is the result of the accumulation of snow, its separation, thereby forming a complex avalanche. This type of avalanche has catastrophic consequences and can destroy a mountain settlement.

Avalanches are wet

Formed from snow accumulations with the presence of bound water. Occur during the period of accumulation of moisture by snow masses, which occurs during precipitation and thaw.

Avalanches are wet

They arise due to the presence of unbound water in snow accumulations. Appear during a thaw with rain and warm wind. They can also occur by sliding a wet layer of snow over the surface of old snow.

Mudflow-like avalanches

They arise from snow formations with a large amount of moisture, the driving mass of which floats in a large volume of unbound water. They are the result of long thaws or rains, as a result of which the snow cover has a large excess of water.

The presented types of avalanches are quite dangerous, fast-moving flows, so you should not think that some are safer than others. The basic safety rules must always be followed.

Avalanche safety

The term avalanche safety refers to a set of actions aimed at protecting and eliminating the tragic consequences of avalanches.

As practice shows, in most accidents the extreme people themselves are to blame, who, without calculating their own strength, themselves violate the integrity and stability of the slopes. Unfortunately, there are deaths every year.

The main rule for the safe crossing of mountain ranges is the full knowledge of the passable territory, with all the dangers and obstacles, so that in an emergency you can safely, carefully leave the dangerous section of the path.

People going to the mountains, the basic rules of avalanche safety, be able to use avalanche equipment, otherwise the likelihood of falling under a snow blockage and death is very high. The main equipment is avalanche shovels, beepers, avalanche probes, float backpack, maps, medical equipment.

Before going to the mountains, it will be useful to take courses on rescue operations during a collapse, first aid, making the right decisions to save lives. Also an important stage is the training of the psyche and ways to overcome stress. This can be learned in courses on working out techniques for saving people or yourself.

If a person is a beginner, it will be useful to read books about avalanche safety, which describe different situations, moments, stages of overcoming them. For a better understanding of avalanches, the best option would be a personal experience gained in the mountains in the presence of an experienced teacher.

Avalanche safety basics:

  • mental attitude and preparation;
  • obligatory visit to the doctor;
  • listening to an avalanche safety briefing;
  • taking with you a sufficient amount of food, small in volume, a spare pair of clothes, shoes;
  • careful study of the route, upcoming weather conditions;
  • taking a first aid kit, flashlight, compass, equipment on a hike;
  • departure to the mountains with an experienced leader;
  • studying information about avalanches in order to have an idea of ​​the degrees of avalanche safety during a collapse.

The list of avalanche equipment, which you need to be able to work with confidently, quickly, for your own safety and rescue of the victims:

  • victim search tools: transmitter, avalanche ball, beeper, radar, avalanche shovel, avalanche probe, other necessary equipment;
  • tools for checking snow flooring: saw, thermometer, snow density gauge and others;
  • tools for rescuing victims: backpacks with inflatable pillows, avalanche breathing apparatus;
  • tools for transporting victims, as well as medical equipment: bags, stretchers, backpacks.

Avalanche slopes: precautions

In order to avoid getting into an avalanche or if there is a high probability of an avalanche situation, you need to know a few important rules for avalanche safety and how to prevent it.

  • move on safe slopes;
  • do not go to the mountains without a compass, know the basics of the direction of the winds;
  • move along elevated places, ridges that are more stable;
  • avoid slopes with snow cornices hanging over them;
  • return along the same road that went ahead;
  • monitor the top layer of the slope;
  • do tests on the strength of the snow cover;
  • it is good and reliable to fix the insurance on the slope, otherwise the avalanche can drag a person with it;
  • take on the road spare batteries for the phone and a flashlight, and also have in the memory of the mobile phone the numbers of all nearby rescue services.

If a group or a certain number of people still find themselves under an avalanche, you need to call rescuers, immediately starting the search on your own. In such a situation, the most necessary tools will be an avalanche probe, a beeper, a shovel.

Every person who goes to the mountains should have an avalanche probe. This tool performs the function of sounding snow during search operations. It is a dismantled rod, two to three meters long. In safety courses, an obligatory item is the assembly of an avalanche probe in order to assemble it in the shortest possible time when creating an extreme situation.

An avalanche shovel is indispensable when searching for victims, it is necessary for digging snow. It is more effective when combined with an avalanche probe.

A beeper is a radio transmitter that can be used to track a person covered in snow.

Only with coordinated, quick actions can a comrade be saved. After a thorough briefing on avalanche safety, a person will be mentally and physically ready to help others.

As a result, I would like to emphasize that hiking in the mountains cannot be carried out in bad weather, in the evening or at night, when crossing a dangerous area, it is imperative to use rope insurance, be sure to have beepers, flashlights, avalanche shovels and avalanche probes in your arsenal. Some part of these instruments must necessarily have a length of 3-4 m.

Observing all the rules, following the instructions, a person will protect himself from disastrous consequences and return home safely.

Write to us if the article was useful.

The materials of the site www.snowway.ru and from other open sources were used.

It is not difficult to say how avalanches arise: on steep mountain slopes, individual layers of snow or the entire snow cover lose their adhesion to the ground or the underlying layer. Due to the enormous weight of the snow, stress is generated inside the snow mass, leading to cracks; it spreads over them and slides down.

Of course, in reality, the science of avalanches is much more complicated, because snow is not a dead mass, having fallen to the ground from clouds, it is constantly changing. At first, it forms, depending on temperature and wind strength, a relatively light and loose cover. An avalanche can sometimes be set in motion by minor disturbances in the structure of the snow cover.

Even a slight heating on a solar noon can increase the tension between the upper and lower layers of snow so much that it will lead to the excavation of the snow shelf. This cause of avalanches is considered the most common.

The four most dangerous types of avalanches are:

1. Dry avalanches consisting of loose snow are very dangerous. They break into the valley at high speed and are accompanied by a monstrous shock wave that crushes even massive concrete barriers. They form on the principle of a growing snowball.

2. Of particular danger are glacial avalanches, which occur, in particular, when the tongue of a glacier breaks off. With their incredible weight, they develop a very high speed. Forces operate in them that can grind even ice, hard as a stone, into powder. Such avalanches have caused many devastating disasters.

3. The term "ground", "soil" and "surface" avalanche designate layers of snow cover that come into motion; soil and soil avalanches slide down the slope and cause its powerful erosion; after the snow melts, the blown material settles at the bottom of the valley. In contrast, surface avalanches slide into the valley on deep, very stable layers of snow.

4. Snow shelves break off along one long line and slide into the valley along their entire width directly along the ground or along an unstable snow layer.

FACTORS PROVOTING AVALANCHES

It is not difficult to say how avalanches arise: on steep mountain slopes, individual layers of snow or the entire snow cover lose their adhesion to the ground or the underlying layer. Due to the monstrous weight of snow, stress is created inside the snow mass, leading to cracks; it spreads over them and slides down.

However, these days, avalanches are increasingly being triggered by reckless skiers and snowboarders. Thrill-seekers, despite the prohibitions, leave the safe track for unstable slopes, getting special pleasure from skiing on virgin snow untouched by skiing, and this endangers not only their own lives, but also the lives of other people.

FORMATION OF CRYSTALS

During the daily rhythm with its temperature fluctuations, individual snowflakes disintegrate and stick together into crystals.

The surface of the snow cover hardens, forming a crust. Under the weight of snow, the lower layers are compressed more and more. From the rays of the sun and warm air currents, snowflakes melt and stick together into an ice layer.

If fresh snow falls after this, the danger of avalanches increases sharply for several days, since the new layer initially does not adhere well to the snow crust (which is called firn). Only when it settles and bakes more strongly with the base, the snow cover again acquires greater stability.

The situation becomes especially dangerous in cases where a lot of snow falls or when the old layer of snow has not yet had time to harden. Therefore, avalanche watchers take drill samples in particularly dangerous places - mainly on steep slopes, ridges and slopes heavily indented by troughs and mounds - and carefully study individual layers. Thus, the uniformity and strength of the entire snow cover are determined. The weaker the individual layers are interconnected, the higher the risk of avalanches. The situation is assessed according to three factors: the structure of the snow cover, weather conditions (by the amount of fresh snow, wind strength and direction) and the terrain (steepness, shape, underlying material, and which way the slope faces).

Avalanche development

1. Loose snow slides over a layer of denser snow.

2. Having accelerated, a mass of snow can rise into the air.

3. The avalanche picks up speed, sometimes reaching up to 350 km/h.

Dry avalanche

Dry avalanches are composed of loose snow and rush especially rapidly.

They begin with small snow landslides, but due to ground shaking and the occurrence of a shock wave, they quickly increase.

STONES THROWING DOWN

Avalanches also include rock masses falling down, that is, rockfall, collapse, mudflow.

During a rockfall, individual stones or stone blocks fall out of a rocky wall; with a more powerful collapse, a large stone mass collapses or rolls down.

A mudflow is an avalanche consisting of a mixture of stones and liquid mud. Such liquid rock avalanches can be triggered by precipitation or rapid changes in the ice sheet, with often catastrophic consequences. So, in 1938, 200 people died in Los Angeles when a mudflow hit the city.

The first victims of the avalanche were the military.

The first victims of the avalanche, which are mentioned in history, were warriors. When Hannibal and his army marched north across the Alps in 218 BC, the White Death claimed about 18,000 men, 2,000 horses, and several elephants.

The largest snow disaster of modern times is also related to the military. In December 1916, during the First World War, about 10,000 soldiers died under avalanches on the Austrian-Italian front in just two days. After a week of continuous snowfall, both belligerents began to fire artillery on the slopes located above the positions of the enemy. The shots caused a powerful avalanche, which buried entire sections of the front along with the troops.

During the First World War, avalanches in the Tyrolean Alps claimed 60,000 lives. Italian and Austrian troops fought for three years in the highlands, suffering from lack of supplies, cold and snow. One of the soldiers recalled: “Nature was our most terrible enemy ... Entire platoons were knocked down, blown into the abyss, filled up without a trace.” The heaviest was December 1916, when 4 m of snow fell in 48 hours, which led to avalanches that killed about 10,000 who fought on both sides of the front.

In Peru, the May 31, 1979 earthquake and the resulting avalanche killed 66,000 people. The force of the shocks reached 7.7 on the Richter scale, the epicenter was located near the large port and industrial city of Chimbote, and the consequences were the most disastrous in the 20th century. A massive layer of soil and ice broke from Mount Huascaran, which demolished the village of Ranrairca, destroyed 5,000 inhabitants and filled up the mountain resort of Yungai. Nearly all of its 20,000 inhabitants perished here.

DECEIVELY IDYLL

After many days of heavy snowfalls, the sun finally came out and warmed the western and southern slopes of the mountains. Fresh snow, not yet compacted, began to slide down faster and faster; soon many small and large avalanches were rushing into the valley. According to experts, on steep slopes, their speed reached 400 km / h, which gave enormous energy to the snow masses. Even massive defensive structures and large houses were demolished like toys.

A 300-meter avalanche with a roar broke off in 1999 from the top of Griskopf, bringing death with it.

In the Austrian Galtür on February 23, 1999, 31 people died in a few minutes, and thousands of guests and inhabitants of this skiing paradise were locked up for many days in the Paznau valley.

On the ruins of Galtür

At first, only local residents and their guests-athletes had to deal with rescue and assistance to the victims, since the valley was completely cut off from the outside world: the roads were covered with a ten-meter layer of snow. Mountain safety authorities have banned rescuers from making their way along the roads to the affected valley due to the high likelihood of new avalanches. Help to the disaster area arrived only the next day by helicopters of the Austrian Air Force.

Victims suffocate or get crushed

An avalanche can carry up to a million tons of snow from a slope and drive an air shock wave in front of it, which, like a bomb explosion, destroys everything in its path. Whoever meets her on the road will be crushed.

Most avalanche victims die very soon, as a snow wall rushing at a speed of 100 km / h and above creates a shock wave; it instantly clogs the lungs and airways of the victim with snow, and the person dies of suffocation. The survivors of this first onslaught are killed when they find themselves inside an avalanche that hurls them against rocks, trees, and other obstacles at great speed.

The deeper a person is buried under an avalanche, the less likely it is to get him out of there alive. After all, if a cubic meter of freshly fallen snow weighs only 60-70 kg, then the packed snow mass of an avalanche presses on the body with a weight of more than a ton, does not allow breathing and simply flattens a person.

Many avalanche victims suffocate already under a meter layer of snow, as fresh air does not reach them.

Therefore, rescuers advise in case of an accident, if possible, press your palms to your face in order to create at least a small space for air, and then the victim, if he is lucky, can hold out until the rescuers arrive. And also, the use of a special one will help the victim hold out for some time until rescuers arrive under a layer of snow.

People covered by an avalanche are searched for by probes. This must be done quickly, because after 20 minutes half of the victims die. The chance of rescue is increased if rescuers and victims carry “ ” with them, which send and receive signals.

STUDYING AVALANCHES

On February 25, 1999, the Sion Valley in the Swiss Alps shook with a terrible roar. In a few seconds the ground shook and the valley was filled with deafening thunder. 600,000 tons of snow fell down the mountainside at a speed of 300 km/h.

In the middle of an avalanche-prone slope, a group of people is sitting in a massive bunker. All of them pinch their ears that hurt from the roar. The bunker is covered with a three-meter layer of hard, like concrete, snow. However, nothing happened to people - they are employees of a Swiss institute that studies snow and avalanches. They have just caused an explosion to cause a dry avalanche, the largest in the world. Thus, they observe the most terrible danger that can only lie in wait in the mountains - for avalanches, which, despite the huge costs of protective and rescue measures, claim the lives of 150-200 people year after year in the mountains of Europe alone.

To prevent such catastrophes, Switzerland alone has spent over the past 50 years 1.5 billion francs on the construction of barriers against avalanches and another billion on the cultivation of forests that block the path of avalanches. And not without success: if in 1951 98 people died under snow masses, then at the end of the millennium “only” 17. And despite the fact that now the mountainous regions are more densely populated than before, and besides, many skiers come here .

This success is by no means accidental. For more than 70 years, the Alpine Republic has been systematically studying the dangers that snow brings with it. The Central Research Institute was founded near Davos on Mount Weisflujoch (altitude 2662 m). Scientists from various scientific fields are developing topics such as “Formation of snow cover”, “Snow mechanics and avalanche formation”.

The purpose of the research, among other things, is to more accurately and timely predict avalanches and to develop effective protective structures that reduce the damage that avalanches cause to nature and buildings. In its forecasts, the institute works closely with meteorologists, because the danger increases significantly when a lot of fresh snow falls on the old snow layers.

The avalanche monitoring service operating in the countries of the Alpine region is installing more and more automatic weather stations, but an accurate forecast of avalanches is still not possible. As before, skiers should remember to take reasonable care in the mountains and avoid dangerous places.

NO ABSOLUTE PROTECTION

Despite all the successes of scientists, avalanches, as before, can suddenly come off the slope. They are born from time to time even in the most seemingly safe places. Sometimes even expensive defensive structures are not able to keep them. Until now, far from all the factors that lead to the fact that snow masses come into motion, crush everything that comes in their way, and drag what they have captured down, have not been studied.

PHOTOS OF AVALANCHES IN DIFFERENT REGIONS OF THE WORLD or DEADLY BEAUTY:

Bezengi wall. Avalanche from Dzhangi-Tau. Photo-Baskakov Andrey

Avalanche between Western and Main Victory

An avalanche from the Bezengi wall that descended between the peaks of Dzhangi-Tau and Katyn. View from the hut Dzhangi-Kosh. Photo by Alexey Dremin

Bezengi, Dykh-Tau, 2009 (4x zoom) Photo: Tatyana Senchenko

Avalanche from Western Shkhara, Bezengi.Photo by Vladimir Chistikov

An avalanche from the Belukha massif flying to the Mensu glacier. January 2003. Photo by Pavel Filatov

Avalanche from the northern wall of the Mizhirgi massif - Dykh-Tau. Photo by Vladimir Kopylov

Avalanche from the northern slopes of Pobeda Peak. Photo by Vladimir Kopylov

An avalanche covering the right edge of the l. Small Tanymas. Photo by Georgy Salnikov

Avalanches from Pobeda Peak

Avalanches from the North Face of Dykh-Tau. Photo by Mikhail Golubev

Elbrus. Winter avalanche from the Northern Face of Donguz-Orun. Photo: Innokenty Maskileison

Antarctica

Krasnaya Polyana. Caucasus

An avalanche descended from one of the five-thousanders of the Caucasus Dzhangitau. Bezengi wall. Photo: Mikhail Baevsky

Avalanche on the railroad in 1935 Canada