What is an avalanche hazard called? Definition of a snow avalanche: varieties, safety. Sloping slope

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, 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 time, and in those places where the mountains are covered with caps of snow all year round, they can melt 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 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 on everyone 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.

Many dangers await climbers, snowboarders and ski lovers. alpine skiing. But the most inexorable and unpredictable of them are avalanches. What are they? 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 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 trenches, as well as from craters formed as a result of the destruction of rocks.
2. Basics. When a gap forms in a layer of snow and part of the mass slides down a flat slope, on which there are no erosion cuts or furrows.
3. Jumping. On the path of the site there are steep cliffs from which snow slides into free fall.

By the nature of movement and structure of mass

A dust avalanche is formed from dry snow. During the movement, the structure of the mass is destroyed and creates a cloud of snow dust. Avalanche speed 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 form under the slabs, which destroy upper 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 a 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 outcrop. This is due to the heating of the rocks, which causes bottom layer the mass is fed with moisture, becomes heavier and begins to shift. Most snow avalanches of this type can be observed in spring. Their speed does not exceed 120 km/h.

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

Due to the occurrence

Based on this criterion, in 1984 V. Akkuratova proposed the following typology:

• Blizzard avalanches

They are formed from the redistribution of the upper layer due to the transfer of masses during a snowstorm. Wind-blown accumulations of snow grains are deposited in relief depressions. 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 seeping into a layer of snow, which causes its structure to be destroyed and the lower layer to thaw and the connections between dense clusters of snowflakes to break.

• Avalanches of dry “young” snow

During intense snowfall, a fresh layer is formed on the surface of the mass, consisting of crystals with a density of no 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 caused by metamorphism

Due to the deformation of the structure of ice particles and the connections between them, snow recrystallization occurs, as a result of which loosened 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 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

Based on the volume and approximate weight of the moving layer, avalanches can be divided into five types:

1. A disaster capable of destroying a populated area or having a destructive impact on a vast area of ​​forest (more than 4,000 km²);
2. Sliding of minor accumulations of snow that are not capable of causing harm to humans;
3. An avalanche, which can destroy a forest area of ​​up to 4,000 km² and also cause damage to buildings, vehicles and technology;
4. A slight shift in the snow mass that can harm a person;
5. A medium-sized avalanche capable of breaking trees and damaging cars and buildings.

If we talk directly about the danger of an avalanche for humans, then it is usually assessed on a 5-point scale:

The danger is negligible. There is a minimal chance of snow melting, but in general the surface is dense and stable. The conditions are quite reliable for holding events.

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, you can load slopes with a steepness of up to 50 degrees. It is advisable not to lay routes through problem areas with an inclination angle of more than 45 degrees.

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

Events are permitted if the organizers take into account the structure of the terrain and the specific conditions at the sites. It is allowed to strain normal slopes with an angle of up to 40 degrees. In areas with problematic terrain, loads at an angle of up to 35 degrees are permissible.

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

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

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

Catastrophic danger. Snow masses are mobile and unpredictable. Events are strictly prohibited. Large volume avalanches are occurring on all slopes, regardless of the degree of inclination.

A slope of 15-20 degrees can be considered avalanche dangerous, with a snow thickness of about 40 cm. There are cases of avalanches from flatter slopes of 10-15 degrees.
The greatest danger of avalanches occurs when the snow thickness is 50-70 cm and the slope steepness is 25-50 degrees.

According to the shape of the start of movement Avalanches can be divided into two types:
1. Avalanches from the point - dry and wet.
2. Avalanches from the line are “snow boards”.
Dry Avalanches usually occur due to little adhesion between recently fallen or transported snow and the dense icy crust covering the slope. Most often, dry avalanches occur in conditions of low temperatures, when the density of freshly fallen snow is less than 100 kg/sq.m. and more. In this case, the density of the snow mass can reach 150 kg/cub.m.

Wet Avalanches occur in unstable weather against the backdrop of thaws and rains. The cause of wet avalanches is the appearance of a layer of water between layers of snow with different densities. Wet avalanches are significantly inferior in speed to dry ones, not exceeding 50 km/h, but in terms of the density of the snow mass, sometimes reaching 800 kg/cub.m., they are ahead of other types of avalanches. Distinctive feature Wet type avalanches have a rapid setting when stopping, which often makes rescue efforts difficult to carry out.

"Snow boards"- These are avalanches, the mechanism of which originates when particles of the surface layer of snow freeze. Under the influence of the sun, wind and heat, an ice crust forms, under which the snow recrystallizes. Over the resulting loose mass, reminiscent of cereals, a denser and heavier layer easily slides down when the layer is separated from the mass, it carries with it more and more snow mass: The speed of “snow boards” can reach 200 km/h, just like dry avalanches .

The possibility of “snow boards” falling off is characterized by the multi-layered nature of the snow mass - alternating dense and loose layers. The likelihood of their disappearance increases with a sharp cold snap accompanied by snowfall. A slight layer of snow is enough for separation to occur. The cold causes additional stress in the upper layer and, together with the weight of the fallen snow, tears off the “snow board”. At the point of separation, snow boards can be from 10-15 cm to 2 meters or more in height.

During their movement, avalanches can change from one type to another or form a combination different types avalanches, due to different densities, humidity and temperatures of oncoming snow masses.

By nature of movement Avalanches are divided into:

Osovy- snow slides descending over the entire surface of the slope.
Jumping- avalanches falling from ledges and shelves.
Tray- avalanches passing through chutes, couloirs and weathering zones of rocks in the form of furrows.

Degree of danger Snow depth Characteristics of avalanche danger

I 15-30 cm Danger appears on the slope of St. 30°

II 30-50 cm Significant danger

III 50-70 cm High avalanche danger

IV 70-100 cm Very large already on the slope of St. 20°

V 120 cm Catastrophic position

Types of avalanches

Osov- snow that has slid along a wide front outside a strictly fixed channel.
When the fall occurs, snow masses detach and slide down the slope, but the underlying snow retards the movement of the sliding masses and they stop before reaching the bottom of the valley.
Typically, the height of snow sliding during snow fall is several times less than the width of its front and sometimes reaches several tens of meters; the speed of snow movement is low.
It is believed that such movement of snow does not pose a particular danger. This doesn't hit the mark once in a while. For example, the famous mountain guide Sepp Kurz died on February 10, 1951 near his home in a snow slide, the length and width of which were 6 and 4 meters, and the thickness of the snow cover was only 24 centimeters.

Trough avalanche

In the case of concentration of moving snow in drainage channels (along strictly fixed channels), the speed of movement increases significantly. The movement of snow takes the form of a current. An avalanche cone forms at the foot of the slope.

Jumping avalanche.

If the drainage channel along which the snow moves has steep sections, then the movement of snow masses during free fall acquires enormous speed. Avalanches of loose fluffy fresh snow that falls in frosty weather can reach speeds of up to 250-300 km/h. Most often, they arise from loose fluffy snow directly during a snowfall or immediately after it.
Even more dangerous are the air waves that arise from the movement of jumping avalanches. Soon after the start of movement, avalanches appear as a cloud of tiny snow dust. Such avalanches do not leave avalanche cones.
If someone falls into such an avalanche at the initial stage, then it does not pose a danger to him, because the snow flows lightly around your feet. But in the middle and further parts there is a threat not only of suffocation by snow dust, but also of being thrown down.
The direct front of the shock wave breaks everything and throws it down. Such avalanches have great destructive power; the pressure can reach 9000 kg/m2. This is enough to break pine trunks like matches.
As an example, I will give a description of the consequences of an avalanche at st. Dallas (Austria) in 1954. An air wave from an avalanche of dry snow threw a railway car weighing 42 tons through the air, and lifted a 120-ton electric locomotive off the rails and hit it into the station building.

Snow board- During the day, in the sun, the top layer of snow heats up and melts, and at night it freezes, turning into a dense, hard crust. The lower layers, compacted under their own weight, sag, and an air cavity is created between it and the crust. The dense crust, not fastened to the bottom layer of snow and as if hanging in the air, is a snow board.
It is very fragile, sometimes a slight external influence is enough for it to break off and an avalanche to begin.
Avalanches from snow boards usually occur during periods of sharp cold weather, hairdryers, and snowfalls, when the latter significantly overload the slope.

Signs of avalanche danger

The surest sign of avalanche danger is the presence of avalanche cones. Most avalanches occur year after year in the same places, and if you see a cone, the avalanche has passed and will pass here more than once.
During their movement, avalanches destroy all vegetation, so dense Pine forest on a slope is a sure sign of the absence of avalanche danger, and vice versa, vertical clearings in forests are a sure sign of an avalanche. Only slopes on which stones or rock outcrops protrude from under the snow, and below there are thickets of bushes that prevent sliding until the snowfall completely covers them, can be considered relatively safe.
A sure sign is heavy snowfall. The degree of avalanche danger gradually decreases during the day after a snowfall, depending on the thickness of the fallen snow cover.
Most weakness The snow cover on the slope is located in its upper part, so spontaneous avalanches begin from here.
Leeward slopes where large masses of snow have accumulated.
Valleys shaped like gorges are very dangerous. Deep ravines filled with snow.
When approaching the highlands, the choice of movement depends on the nature of the valley.
When moving along wide trough-shaped glacial valleys, you should stick to the middle (but avalanches and exposure to air waves are possible from the slopes)

Precautionary measures.

After a snowfall, you should wait a day for the snow to settle
The safest are the slopes irregular shape or overgrown with forest.
The sun's heat, which causes snow to melt, can cause an avalanche, so you should walk in shaded areas before noon, avoiding sunlit areas.
In the afternoon, stick to slopes that have previously been exposed to the sun and avoid areas that are new to the sun's rays.
Avoid small ravines, ravines and valleys with steep slopes.
Walk along mountain ridges and hills above avalanche paths. In this case, however, the likelihood that you will provoke an avalanche increases, but in this case there is a good chance of remaining on the surface of the snow masses or not being carried down by them at all. Always be aware of the possibility of an avalanche, even if you have never witnessed one yourself. Try to determine where the avalanches started, their direction, and how long ago they occurred. This will indicate the places where you can expect them to converge.
By choosing a path at the very top of the avalanche slope (above the line of maximum stress of the snow layer), you can trigger an avalanche from loose snow. However, given the small size of the snow masses located above and the fact that the avalanche will gain its strength only on the section of the slope located below, such an avalanche will not pose a serious danger.
If closer to the lower part, when moving on the snow, its natural support is destroyed (the slope is cut), then first some minor (10-15 cm) movements of the snow occur, instantly setting the higher-lying masses of snow into motion.
Slopes with snow board. The crust can be so strong that there are almost no traces left on it, not only from boots but also from the edges of skis, and when moving on it there is no movement of snow. But, if the crust is damaged in the upper part of the board (in the tension zone), this can instantly lead to the formation of longitudinal cracks in the overstressed layer and the formation of an avalanche. The same thing will happen if you overload the board with your weight. In the lower part of the board (compression zone), the same actions do not lead to the formation of avalanches.
In an avalanche zone, the ascent must take place along prominent relief forms. Under no circumstances should you climb up depressions (gullies, couloirs). If there is no other way, climbing through snow should be done head-on, regardless of snow conditions. If there are rocky outcrops on the slope or large forms of ice protruding from under the snow, movement is carried out under their protection. On a ski trip, the track along an avalanche-prone slope is laid at a slope of 8-12 degrees.

Rules for overcoming avalanche areas.
Firstly think over and choose the safest route through avalanche-prone areas.
Secondly– prepare for the worst, put on a sweater and a windbreaker, cover your face with a scarf or windproof mask, raise the hood, fasten the collars and cuffs of your windbreaker tightly, put on mittens. The straps of the backpack must be moved so that it can be quickly thrown off the shoulders. The ski bindings are loosened or unfastened, and the hands are removed from the lanyards of the ski poles.
Third. If there are people in the movement area, take and tie an avalanche cord.

When an avalanche begins to move
Try to escape, leave, if this cannot be done (in case of small avalanches), you can take the avalanche upon yourself if you are near the separation zone. Sticking an ice ax, ski poles or removed skis deep into the dense snow, secure yourself in place to let the moving stream pass.
Caught in an avalanche
Immediately get rid of ski poles, backpack, skis, because all these objects will play the role of a kind of anchor and pull you upside down into the snow.
Once caught in an avalanche, you need to try with all your might to stay on the surface and try to rake to its edge, where the snow moves much slower. Swimming movements along the flow of snow flow to a certain extent prevent a person from being sucked into an avalanche.
If you can’t get out, then you need to group yourself, pulling your knees to your stomach and protecting your face from the snow with clenched fists, while simultaneously creating a void near your face, allowing you to breathe freely.
When stopping an avalanche, determine your position (where is up and where is down) Collect saliva and let it flow out of your mouth, this will allow you to find out where is down, and begin to move in the opposite direction if possible.. Keep your spirit and air calm.
Do not consider your situation hopeless, do not lose confidence in your position, under no circumstances should you sleep. You must fight sleep with all your might.
A person caught in an avalanche can only scream when he hears the voices and footsteps of the search participants above him. Since the sound from the depths of the snow layer is heard only in the immediate vicinity of the source
With all types of avalanches made of dry snow, and especially with avalanches made of fluffy snow, snow dust gets into the mouth, nose, eyes, ears and suffocates a person, even if the snow that covers him is only 15-20 cm thick (the importance of protecting the mouth and nose scarf). Warm clothes protect against freezing.
When an avalanche stops, immediately try to gain as much ground as possible from the snow. more space. To do this, try to move your arms, head, and legs. Push the snow, then determine where is up and where is down
For an avalanche to move, the snow becomes very hot and freezes very quickly when it stops, so don’t waste time, catch your breath and start getting out without wasting time. It is not at all necessary that you will be covered with many meters of snow; it is possible that you are very close to the surface, but it will be impossible to break through the frozen snow.
When caught in an avalanche of wet and wet snow, it is very important to maintain a snow-free space in front of your face.
Wet snow is a gigantic load of 800 kg/m3. At the moment the avalanche stops in its cone, due to the high pressure of the snow masses, the temperature rises. The resulting meltwater fills the gaps between the fused snow particles and soon freezes. The resulting “snow cement” cannot be shoveled and is difficult to break with an ice ax.
When caught in an air wave- throw yourself face down into the snow, trying to bury yourself deeper into it and at the same time be sure to close your nose, mouth and ears from the penetration of snow dust. You can hide behind a large rock; trees cannot serve as protection.
Don’t despair, there are known cases where the living were dug up after a few days. However, only a few survived

"Mountaineering Federation of the Nizhny Novgorod Region" Nizhny Novgorod

A snow avalanche is one of the most dangerous natural phenomena, which is typical for mountainous areas. From the name itself it is clear that snow is involved in this process.

Avalanche definition. This is a type of landslide when a large volume of snow and ice slides or falls down steep mountain slopes. The speed depends on the steepness of the slope, the volume and severity of the snow. On average this is 20–30 meters per second.

Avalanche in the mountains

Along the way, the weight of the snow mass increases because it captures new volumes. And the weight of some of them can reach tens, hundreds of tons. IN in rare cases Not only the snow is melting, but also the glacier. Then the weight of the entire mass can reach tens and hundreds of thousands of tons.

Causes

In mountainous areas, especially if it high peaks, almost always, including in summer, there is snow. In winter, the layer of snow cover becomes larger. This increases the load, as a result of which, due to the steepness of the slope, a certain mass begins to roll down, gradually increasing. A snow avalanche is a natural process.

Avalanche: photo

They have always been and will be in mountainous areas. But if people live in these areas, the avalanche becomes dangerous. In the mountains they try to build houses in safe places where avalanches do not reach. Therefore, residential buildings and other structures rarely suffer from such natural phenomena, but such cases sometimes occur.

In most cases, the victims are people who, for one reason or another, ended up in this place. These are athletes involved in alpine skiing, climbers who conquer peaks. There are also risks of avalanches on ski slopes. In these places, avalanches are provoked in advance and artificially using special equipment to ensure safety.

In most cases the cause is natural. But an avalanche can also be triggered by people if they decide to go to the mountains when rescue workers have informed in advance that it is dangerous. Any slightest mechanical impact can be the beginning of snow melting.

The most common causes of avalanches include:

• heavy snowfalls, increasing the volume of snow mass on the slopes
• human factor (mechanical impact, loud sound, shot, etc.)
• an increase in air humidity, which also makes the snow heavier
• earthquakes (mountains are usually located in seismic zones)

According to the nature of movement they are divided into:

• Osovy — go down over the entire surface and look more like a landslide
• Jumping - fall from ledges
• Tray - pass in the form of furrows through rock weathering zones and natural gutters

According to movement they are divided into:

• Streaming
• Cloud
• Complex

How dangerous is an avalanche?

Large snowfalls can destroy entire settlements located at the foot of the mountains. Fortunately, this happens extremely rarely, because people try not to settle in dangerous areas. Mostly people suffer. There is very little chance of survival. The snow mass is very heavy and can immediately break bones, which deprives a person of the chance to get out. And then there is a high risk of remaining disabled, even if he is found and dug out from under the snow.

Even if the bones are intact, snow can clog the airways. Or simply, under a huge layer of snow, a person simply does not have a sufficient supply of oxygen, and he dies from suffocation. Some are lucky, and they manage to be saved. And it’s good if without negative consequences, because many have frostbitten limbs amputated.

Precursors of an avalanche

The main harbinger is weather. Heavy snowfall, rain, and wind create dangerous conditions, so it is better not to go anywhere on this day. You can also look at the whole general state terrain. Even small landslides of snow indicate that it is loose and the humidity is high. It's better to play it safe.

The most dangerous period for avalanches is considered to be winter, in the moments after precipitation falls.

If you notice an avalanche 200–300 meters away, there is a small chance of escaping from it. You need to run not down, but to the side. If this was not possible, you must perform the following steps:

• cover your nose and mouth with gloves to prevent snow from getting in there
• clear the snow in front of the face and also in the chest area so that you can breathe normally
• you can’t scream, because it takes energy, and anyway, due to the high sound-absorbing properties of snow, no one will hear anything
• you need to try to get out, trying to remove the snow on the way, compact it
• you should not fall asleep to be alert and give a sign if rescuers are close

How to escape an avalanche

Compliance with these rules increases the chances of survival in such an extreme situation.

Avalanche equipment

Today, many manufacturers of sports and tourism goods offer special avalanche equipment. This includes the following devices and equipment:

• Avalanche sensor- it must be turned on immediately as soon as the athlete goes to the mountains. In the event of an avalanche, other members of the group who managed to escape from it, as well as rescuers, will be able to record the signal from this sensor, quickly find and rescue the person.

• Shovel. It is more needed by those in the group who managed to escape the avalanche in order to dig out those who fell under it.

• Avalanche probe. This device is needed to quickly find a person. With its help, you can determine the exact depth of snow under which a person is located in order to calculate the forces and dig him out.

• Avalung system from Black Diamond- a special device that removes exhaled air to the back. This is necessary so that the exhaled warm air did not form a snow crust in front of the face, completely blocking the access of oxygen.

We talk in more detail about avalanche equipment in our separate article.

Avalanche areas in Russia

Avalanches in Russia are not uncommon. These are the mountainous regions of our country:

• Khibiny on the Kola Peninsula
• Kamchatka
• Caucasus Mountains
• ridges and highlands Magadan region and Yakutia
• Ural Mountains
• Sayan Mountains
• Altai Mountains
• ridges of the Baikal region

The most destructive avalanches in history

Destructive, terrible avalanches are mentioned in many ancient chronicles. In the 19th and 20th centuries, information about avalanches was already more detailed and reliable.

The most famous snow avalanches:

• 1951 Alps (Switzerland, Italy, Austria). This winter there was a whole series of avalanches due to heavy snowfalls and bad weather. 245 people died. Several villages were wiped off the face of the earth, and almost 50,000 people lost contact with the outside world for a long time until rescuers came to their aid.

• 1954 Austria, village Blons. On January 11, 2 avalanches occurred at once, which claimed the lives of several hundred residents. More than 20 people are still missing.

• 1980 France. The avalanche killed about 280 tourists at the ski resort.

• 1910 USA, Washington state. A huge avalanche in an area where there had never been one before hit railway station and claimed more than 10 lives.

A lot of avalanches occur in Asia: in Pakistan, Nepal, China. But there are no accurate statistics about deaths and destruction.

We also invite you to watch a video of the largest snow avalanches:

Interesting too

- 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 sanatorium-resort complexes, iron and highways, power lines, mining facilities and other utility 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 at relatively warm weather 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 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, in the south of Western and Eastern Siberia, 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 on economic activity and natural environment avalanches are divided into:

• 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 outside world for several days.

IN rural areas and single-story houses, it is also necessary to have entrenching tools (shovels, crowbars, etc.) 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. At passive protection Avoid using avalanche slopes or install barrier shields. At active protection fire at avalanche-prone slopes, 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 when high speeds winds, when snowflakes rise to 2 m or higher, as a result of which atmospheric visibility deteriorates, sometimes dropping 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 we're talking about O 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.

Main damaging factor during snow drifts, during a blizzard, blizzard, blizzard, exposure to low temperatures causes frostbite, sometimes leading to freezing of people.

If there is an immediate threat of such natural disaster notification of the population is organized, the necessary forces and means are put on alert, road and utility services, radio broadcasting centers are transferred 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 locality or near it. 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, on open area where there are no signs, you need 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 medical care, clearing roads and areas around buildings, providing assistance to stranded drivers, 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.