What causes avalanches. Conditions for the occurrence of snow avalanches. The most destructive avalanches in history

Avalanches. Every year, many people die under them, either because they ignore the danger or because they know little about avalanches.

Many of us don't take the threat from avalanches seriously until someone is killed or injured in one. The sad fact is that people caught in an avalanche usually provoke it themselves. Skiers cut slopes, climbers walk in avalanche times. Moreover, the victims are often professionals in their field, but they neglect the avalanche danger. This article provides basic knowledge about avalanches.

Avalanches.

Potential threats

An avalanche can move at a speed of 200 kilometers per hour. Such a force can smear you against trees and rocks, grind you into rocks, make a mess of your insides and impale you on your own skis or snowboard. About one third of all avalanche victims die due to injury.

If you were not injured by an avalanche, you will be struggling with a mass of snow as dense as concrete, which squeezes your body. An avalanche, which begins as snow dust, heats up from friction with the slope as it moves down, melts a little and then freezes tightly around your body. All this mass is enough to squeeze all the air out of your lungs.

If you manage to create an air pocket around you before the snow settles, you have a good chance of survival. If you and your friends have an avalanche transmitter and know how to use it, then your chances of survival are even greater. However, this is where the race against time begins. Most people are unable to survive an avalanche for more than 30 minutes (Black Diamond AvaLung backpacks can extend that time to up to one hour), so it makes sense to purchase and learn how to use avalanche transmitters. A must-have item for winter freeride enthusiasts. About 70% of avalanche victims die from asphyxiation.

The best protection against avalanches is, of course, knowledge of avalanche conditions and slopes, and avoidance of dangerous situations.

Loose avalanches.

Such avalanches form when there is little or no grip on the snow cover. As a rule, such avalanches begin from one point either on the surface of the slope or close to it. Such avalanches gain greater snow mass and momentum while moving down the slope, often forming a path behind them triangular shape. The causes of such avalanches can be blocks of snow falling onto the slope from the cliffs above or melting snow cover.

Such avalanches occur on dry and wet snow and occur both in winter and summer. Winter loose avalanches usually occur during or after a snowfall. In warmer seasons, wet, loose avalanches are caused by snow or melt water. These avalanches are dangerous both in winter and summer.

Reservoir avalanches.

These avalanches pose much more danger. Sheet avalanches form when one layer of snow slides off the bottom layer and rushes down the slope. Most freeriders end up in such avalanches.

They are caused by snowfalls and strong winds, which deposit layers of snow that change over time. Some layers are tracked and held together, while others, on the contrary, are weakened. Weak layers are often grainy or very light snow (powder) so that other layers cannot grip them.

An avalanche occurs when the top layer, called the “plank,” is not sufficiently bonded to the underlying layer and is set in motion by some external agent, usually a skier or climber. Unlike loose avalanches, which start from a single point, sheet avalanches increase in depth and width, usually along a separation line at the top of the slope.

Avalanche release on Cheget:

Factors contributing to avalanches.

Terrain.

Slope steepness: Pay attention to the steepness of the slope when you are skiing or climbing. Avalanches often occur on slopes steeper than 30-45 degrees.

Slope side: In winter, southern slopes are much more stable than northern slopes, as the Sun melts and compacts the snow. Unstable layers of “deep rime,” dry, icy snow that does not adhere to adjacent layers, are most often located on northern slopes. Therefore, be vigilant when you see a tempting northern slope with excellent powder, because they are more dangerous than the southern slopes, due to the fact that they do not get enough solar heat, which will compact the snow over the winter. At the same time, in spring and summer, southern slopes melt more, which leads to dangerous wet avalanches. More warm weather at this time of year, it strengthens the snow on the northern slopes, making them safer.

Terrain hazards: Snow cover is most often unstable on convex slopes, rocky outcroppings, boulders or trees where the snow cover is interrupted, leeward slopes or under eaves. It is best to avoid bowls, circuses and pits where snow can accumulate after an avalanche (avalanche discharges). Steep, narrow couloirs (or gullies) usually accumulate a lot of snow and present great danger for tourists and skiers who find themselves in them. Often, it is impossible to get out of such places due to the steep side slopes, so in the event of an avalanche there is nowhere to run.

Weather

Precipitation: snow is least stable after snowfalls or rains. A large number of snow that has fallen in a short period of time is a sign of avalanche danger. Heavy snowfall, especially wet or dense snow falling on powder, creates unstable layers in the snowpack. Rain seeps through and heats the lower layers of the snowpack and also reduces friction between the layers, making them less stable. After heavy snowfall, you should wait at least two days before going to avalanche areas.

Wind: Another indicator of snow cover instability is wind. Often strong wind carries surface snow from one slope to another part of the ridge, where the snow falls down, forming an avalanche. Pay attention to the intensity and direction of the wind throughout the day.

Temperature: A large number of problems with snow cover are caused by temperature fluctuations. The formation of snow crystals can vary due to temperature differences between the surface and overlying layers, different layers in the center of the cover, and even between the air temperature and the upper snow layer. A particularly dangerous snow crystal, due to its inability to bond with other crystals, is “frost.”

Deep frost ("sugar snow"), due to its similarity to granulated sugar, can be located at any depth or several depths of deep snow cover. Often a sharp increase in temperature leads to wet avalanches, especially in the spring, so be careful when it gets warm in the mountains.

Snow cover

Snowfalls occur one after another throughout the winter. Temperature changes cause metamorphosis of snow crystals. If the composition of the snow remains the same, then the snow cover is uniform and stable. Snow becomes dangerous and unstable when layers of different types of snow form within the snowpack. To every freerider it is imperative to check snow layers for stability, especially on slopes of 30-45 degrees.

How to test a slope for avalanche danger:

Human factor

While terrain, weather and snow cover play a big role in triggering avalanches, it is important to remember that ego, emotions and herd mentality can seriously cloud your judgment and lead you to make rash decisions. In fact, according to a recent survey of Canadian avalanche workers, those surveyed indicated ‘ human factor’ and ‘wrong choice of terrain’ as the main causes of accidents caused by avalanches. Most avalanches are caused by people!

Typical mistakes when making decisions:

Familiar places: It is most likely that you will take risks in a place that is familiar to you. Conditions, however, can change from minute to minute, so treat any terrain as if you were seeing it for the first time.
OK: encouragement from a group can put a lot of pressure on you. “Everything will be fine, relax!” Even if you feel that something is wrong, in order to please the group you may take unnecessary risks.
Get to the place at any cost: if you want to get to your destination too much, you may act against your better judgment and ignore danger signs, focusing only on your goals. Foreign climbers call this phenomenon “summit fever.”
"We have an expert with us": You imply that there is someone else in your group with more experience than you. You think so based on the fact that this person was in this place before you or he underwent some kind of special training. It's better to ask than to guess.
Existing trails: you can feel safe because you see a well-trodden path ahead of you. In our mountains, I was once walking along a seemingly excellent path, but I felt that the slope under the path was very unreliable. Just because someone has been here before you doesn't mean it's safe to walk here.
"Virgin Fever": You can turn a blind eye to the signs of avalanche danger when there is fresh, deep and untouched snow in front of you. Don't give in to temptation!
“Others have passed!”: It is very easy to succumb to the “herd instinct” and go on a dangerous slope when other people have already passed in front of you. Always assess the situation as if you are alone. Tell me if you feel something is wrong.

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 old (stay) snow requires a cover of 70 cm thick. 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. Best condition to start moving the snow mass and gaining it certain speed is the length of the open slope from 100 to 500m. Much depends on the intensity of the snowfall. If 0.5 m of snow falls in 2-3 days, then this usually does not cause concern, but if the same amount falls in 10-12 hours, then snowfall is quite possible. In most cases, the snowfall intensity of 2-3 cm/h is close to critical.

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

One of the most important factors influencing the formation of avalanches is temperature. In winter, when the weather is relatively warm, when the temperature is close to zero, the instability of the snow cover increases greatly, but quickly passes (either avalanches occur or the snow settles). As temperatures drop, periods of avalanche danger become longer. In spring, with warming, the likelihood of wet avalanches increases. The lethality varies. An avalanche of 10 m3 already poses a danger to humans and light equipment. Large ones are capable of destroying capital engineering structures and forming difficult or insurmountable blockages on transport routes.

Speed is one of the main characteristics of a moving avalanche. In some cases it can reach 100 m/s. The ejection range is important for assessing the possibility of hitting objects located in avalanche zones. A distinction is made between the maximum emission range and the most probable, or long-term average.

The most probable ejection range is determined directly on the ground. It is assessed if it is necessary to place structures in the avalanche zone for a long period. It coincides with the boundary of the avalanche fan. The frequency of avalanches is an important temporal characteristic of avalanche activity. A distinction is made between average long-term and intra-annual recurrence rates. The first is defined as the frequency of avalanches on average over a long-term period. Intra-annual frequency is the frequency of avalanches during the winter and spring periods. In some areas, avalanches can occur 15-20 times a year.

The density of avalanche snow is one of the most important physical parameters, which determines the impact force of the snow mass, the labor costs for clearing it, or the ability to move on it. For dry snow avalanches it is 200 - 400 kg/m 3 for wet snow - 300 - 800 kg/m 3.

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

The potential period of avalanche formation 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. avalanche snow destructive natural

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. How are they classified?

To assess the probability of avalanches of freshly fallen and blizzard snow, 10 main avalanche-forming factors are used (Engineering Geology..., 2013).

1. Height of old snow. Snow first fills the unevenness on the slope, and only after that can a flat, smooth surface emerge, allowing new layers of snow to slide down. Therefore than more height old snow before the snowfall begins, the greater the likelihood of avalanches.

2. The condition of old snow and its surface. The nature of the snow surface affects the adhesion of chewed snow to old snow. The smooth surface of wind-driven snow slabs or ice crust favor avalanches. The presence of layers and interlayers of deep frost is especially predisposing to avalanche formation. A rough surface, wind-driven sastrugi, and spongy rain crusts, on the contrary, reduce the possibility of avalanche formation.

3. The height of freshly fallen snow or snow deposited by a blizzard. An increase in the depth of snow cover is one of the most important factors in avalanche formation. The amount of snowfall is often used as an indicator of potential avalanche danger.

4. The sight of freshly fallen snow. The type of solid precipitation that falls affects the mechanical properties of the snow cover and its adhesion to old snow. Thus, when prismatic and needle-shaped crystals or star-shaped crystals fall out in frosty, windless weather, a loose snow cover is formed, characterized by low adhesion. The greatest likelihood of avalanches occurs when a cover of freshly fallen fluffy and dry fine-grained snow is formed.

5. Density of freshly fallen snow. The greatest likelihood of avalanches is observed when a snow cover of low density is formed - less than 100 kg/m3. Increasing the density of snow reduces the likelihood of avalanches, but this rule does not apply to snow slabs formed during snowstorms.

6. Snowfall intensity (snow deposition rate). At low snowfall intensity, a decrease in the stability index of snow cover on a slope as a result of an increase in shear forces is compensated by an increase in stability due to an increase in adhesion and the coefficient of friction during snow compaction. As the rate of snow deposition increases, the influence of an increase in its mass prevails over the influence of its compaction, and creates conditions for a decrease in the stability of the snow cover and the formation of avalanches.

7. The amount and intensity of precipitation is a factor characterizing the increase in snow mass per unit area of the horizontal projection of the slope, including taking into account liquid precipitation and snowstorms.

8. Snow settling. The process of compaction and settling of falling snow increases its adhesion and the coefficient of internal friction and thereby contributes to increasing the stability of the snow cover.

9. Wind. Wind transfer leads to redistribution of snow cover, the formation of hard crusts, snow slabs and blows. The wind forms snow cornices and below them - accumulations of loose snow. A strong wind creates air suction from the snow layer, which contributes to the migration of water vapor and loosening of the lower layers of snow. Wind plays an important role in avalanche formation processes, especially as a factor in blizzard snow transfer.

10. Temperature. The influence of temperature on avalanche formation is multifaceted. Air temperature affects the type of solid precipitation particles that fall, the formation, compaction and temperature regime snow cover. The difference in the temperature of the snow cover in depth is also determined by the processes of temperature-gradient metamorphism. A rapid decrease in air temperature can lead to the formation of temperature cracks in the rupture of the snow layer and the occurrence of avalanches.

To active methods of avalanche protection include measures aimed at initiating avalanches so that the consequences are minimal. Shooting from guns has long been used for these purposes. artillery piece(both with a projectile - in the area where a dangerous snow mass is located, and with a blank shot, in order to create an acoustic impact leading to a deliberate avalanche). Methods of simply “trimming” snow masses with skis and collapsing snow peaks have long been used, but these methods require good skills and are very dangerous. The most modern way prevention negative consequences avalanche protection - active dynamic avalanche protection, which is a device located in areas of greatest avalanche formation and controlled remotely, which allow influencing snow masses for the purpose of artificially triggering an avalanche, using compressed air or explosions of a gas-air mixture.

Passive avalanche protection measures are aimed at holding snow on the slope and preventing avalanches or at directing avalanches in a safe direction. Such measures include the construction of avalanche barriers, chutes, avalanche cutters and dams on the slopes (Sadakov, 2009). On linear objects, such as automobile or railways, construct avalanche protection galleries.

Most catastrophic avalanches occurred after days of heavy snowfall that overloaded the slopes. Already with a snowfall intensity of 2 cm/h, lasting up to 10 hours in a row, an avalanche danger arises. Freshly deposited snow is often loose and loose, like sand. Such snow easily causes avalanches. Avalanche danger increases many times when snowfalls are accompanied by wind. When there is a strong wind, a wind or snow board is formed on the surface of the snow - a layer of fine-grained snow of high density, which can reach a thickness of several tens of centimeters. Obruchev called such avalanches “dry”: “They break in winter after a heavy snowfall without a thaw, when the snow blows on the ridges and steep slopes reach such a size that the shaking of the air from a gust of wind, a shot, even a loud scream causes them to break away. The latter is greatly facilitated, "if fresh snow falls on the smooth surface of old snow, captured by frost after a thaw. These avalanches fly down and at the same time fill the air with snow dust, forming a whole cloud."

In the absence of snowfall, the snow gradually “ripens” to generate avalanches. Over time, the snow layer gradually settles, which leads to its compaction. Sources of avalanche danger are weakened layers in which loosely bound crystals of deep frost form. It is this that eats away the lower layer of snow cover, suspending the upper layer.

The condition of the snow cover changes dramatically when water appears in it, which significantly weakens the strength of the snow. During sudden melting or intense rain, the structure of the strata quickly collapses, and then enormous “wet” avalanches form. They melt over large areas in the spring, sometimes capturing all the snow that has accumulated over the winter. They are also called ground ones because they move directly along the ground and tear off the soil layer, stones, pieces of turf, bushes and trees. These are very heavy avalanches.

Snow lying on a slope moves under the influence of gravity. For the time being, shear resistance forces (adhesion of snow to its lower layers or soil and frictional force) keep the snow on the slope. In addition, the displacement of the layer is prevented by the snow cover located below and held back by the one that lies above. Snowfall or blizzard, recrystallization of the snow column, the appearance of liquid water in the column leads to a redistribution of forces acting on the snow.

Snowfall overloads the slopes with snow, and the forces holding the snow cannot keep up with the increasing force of gravity, which tends to move it. Recrystallization weakens individual horizons, reducing holding forces. Rapid melting of snow due to rising temperatures or wetting of snow by rain sharply weakens the bonds between snow grains, also reducing the effect of holding forces.

For an avalanche to start, it needs the first impulse. Such a trigger is heavy snowfall or severe snowstorms, warming, warm rain, cutting snow with skis, vibration from a sound or shock wave, earthquakes.

Avalanches begin their movement either “from a point” (when the stability of a very small volume of snow is disrupted), or “from a line” (when the stability of a significant layer of snow is disrupted at once). The looser the snow, the less it is needed to start an avalanche. Movement begins with literally a few particles. A snow plank avalanche begins with cracking of the snow cover. A narrow crack quickly grows, side crevices appear from it, and soon the snow mass breaks off and rushes down.

For a long time, an avalanche was represented in the form of a snowball that flies down the slope and increases due to the accumulation of new portions of snow (almost all ancient engravings depicted an avalanche this way). An avalanche was represented by a ball until the 19th century. The variety of snow avalanches and the diversity of forms of their movement made it difficult to understand the physics of avalanches. An avalanche is a multicomponent flow, since it consists of snow, air and solid inclusions. The physics of such flows is very complex. The forms of avalanche movement are varied. Snow pellets can roll, slide and rotate in it snowballs and fragments of a snow board, can flow like water, a solid mass of snow, or a snow-dust cloud rise into the air. Different types of movement complement each other, transforming into one another in different sections of the same avalanche. The front of an avalanche moves faster than its main body due to the collapse of the snow cover in front of the front from the avalanche impact. So, more and more new portions of snow are included in the avalanche, while in the tail part the speeds fall. On the crests of waves arising on the surface of a moving avalanche, stone fragments appear every now and then, which indicates strong turbulent mixing in the body of the avalanche.

As the slope flattens, the body of the avalanche slows down its movement. The body of the avalanche spreads over the surface of the cone. The stopping snow quickly hardens, but continues to move for some time under the pressure of the tail part of the avalanche, until the avalanche finally calms down.

Recognizing avalanche territory is the first step in assessing avalanche risk. Many people caught in avalanches do not notice the danger until it is too late. The most common mistake is the belief that avalanches occur only in large, clearly defined areas. That's why people don't pay attention to the little traps of the terrain. Another mistake is to assume that it is safe to travel along the valley floor without considering the possibility of being caught in an avalanche from the overlying slopes. The terrain features described below affect the occurrence of avalanches, so they will help you recognize avalanche-prone areas.

Slope angle is an important variable in determining the likelihood of avalanches. Therefore, this factor plays an important role in the assessment and development of the route.

Violation of stability and the formation of avalanches is observed on slopes with steepness from 15 ° to 60 °, although cases where avalanches originate on gentler slopes are not uncommon.

On steep slopes, snow is poorly retained; most snowflakes roll down during a snowfall and large masses of snow are deposited relatively rarely. At a slope below 25°, the load is not large enough for snow avalanches to occur (exceptions include ultra-wet hydraulic avalanches and snow-water flows, which occur on steep slopes).< 15 °). Поэтому наиболее лавиноопасными считаются склоны крутизной от 25 до 50 ° (рис. 6).

Rice. 6.

The steepness of the slope is important because, simultaneously with its growth, the pressure on the snow layer and on all areas adjacent to the snow slab increases. It is important to remember that you can trigger an avalanche from below even when crossing a 15 degree slope if the top of the slope is at least 25° steep and instability exists.

On uneven slopes, additional compressive or tensile stresses arise due to the variability of snow cover flow rates depending on the angle of inclination and spatial heterogeneity of height, density and viscosity of the snow.

On convex slopes, snow slabs most often collapse right at the bend, in the place where conditions are created for the occurrence of tensile forces. Concave slopes provide some support through compression at the base. As a result of this, the density of snow on concave areas of the slope is often greater than on nearby smooth slopes and areas of convex relief. And the avalanche line can also run along them, especially during periods of unstable snow cover. On wide and smooth slopes, avalanches can occur anywhere. Boulders, trees on the slope and relief ridges act as “anchors” and help hold the snow in place until they are covered. Such slopes are less avalanche-prone than open slopes, but such anchors must be located very close to each other so that they can be walked on without causing an avalanche. Moreover, such anchors can be areas of increased load, because the snow above them on the slope is held in place, and on the sides of them slides under the influence of gravity. Thus, the pressure on the strata may be greatest near the anchors. As a result, they may turn out to be the starting points of avalanches.

Avalanches. Every year, many people die under them, either because they ignore the danger or because they know little about avalanches.

Avalanches.

Potential threats

The best protection against avalanches is, of course, knowledge of avalanche conditions and slopes, and avoidance of dangerous situations.

Loose avalanches.

Such avalanches form when there is little or no grip on the snow cover. As a rule, such avalanches begin from one point either on the surface of the slope or close to it. Such avalanches gain greater snow mass and momentum while moving down the slope, often forming a triangular-shaped path behind them. The causes of such avalanches can be blocks of snow falling onto the slope from the cliffs above or melting snow cover.

Reservoir avalanches.

These avalanches pose much more danger. Sheet avalanches form when one layer of snow slides off the bottom layer and rushes down the slope. Most freeriders end up in such avalanches.

Avalanche release on Cheget:

Factors contributing to avalanches.

Terrain.

Slope steepness: Pay attention to the steepness of the slope when you are skiing or climbing. Avalanches often occur on slopes steeper than 30-45 degrees.

Slope side: In winter, southern slopes are much more stable than northern slopes, as the Sun melts and compacts the snow. Unstable layers of “deep rime,” dry, icy snow that does not adhere to adjacent layers, are most often located on northern slopes. Therefore, be vigilant when you see a tempting northern slope with excellent powder, because they are more dangerous than southern slopes, due to the fact that they do not receive enough solar heat to compact the snow over the winter. At the same time, in spring and summer, southern slopes melt more, which leads to dangerous wet avalanches. Warmer weather at this time of year hardens the snow on northern slopes, making them safer.

Terrain hazards: Snow cover is most often unstable on convex slopes, rocky outcroppings, boulders or trees where the snow cover is interrupted, leeward slopes or under eaves. It is best to avoid bowls, circuses and pits where snow can accumulate after an avalanche (avalanche discharges). Steep, narrow couloirs (or gullies) tend to accumulate a lot of snow and pose a huge danger to hikers and skiers who get caught in them. Often, it is impossible to get out of such places due to the steep side slopes, so in the event of an avalanche there is nowhere to run.

Weather

Precipitation: snow is least stable after snowfalls or rains. A large amount of snow falling in a short period of time is a sign of avalanche danger. Heavy snowfall, especially wet or dense snow falling on powder, creates unstable layers in the snowpack. Rain seeps through and heats the lower layers of the snowpack and also reduces friction between the layers, making them less stable. After heavy snowfall, you should wait at least two days before going to avalanche areas.

Wind: Another indicator of snow cover instability is wind. Often strong winds carry surface snow from one slope to another part of the ridge, where the snow falls down, forming an avalanche. Pay attention to the intensity and direction of the wind throughout the day.

Snow cover

How to test a slope for avalanche danger:

Human factor

While terrain, weather and snow cover play a big role in triggering avalanches, it is important to remember that ego, emotions and herd mentality can seriously cloud your judgment and lead you to make rash decisions. In fact, in a recent survey of Canadian avalanche experts, respondents cited 'human error' and 'poor terrain selection' as the main causes of avalanche accidents. Most avalanches are caused by people!

Typical mistakes when making decisions:

Familiar places: It is most likely that you will take risks in a place that is familiar to you. Conditions, however, can change from minute to minute, so treat any terrain as if you were seeing it for the first time.
OK: encouragement from a group can put a lot of pressure on you. “Everything will be fine, relax!” Even if you feel that something is wrong, in order to please the group you may take unnecessary risks.
Get to the place at any cost: if you want to get to your destination too much, you may act against your better judgment and ignore danger signs, focusing only on your goals. Foreign climbers call this phenomenon “summit fever.”
"We have an expert with us": You imply that there is someone else in your group with more experience than you. You think so based on the fact that this person was in this place before you or he underwent some kind of special training. It's better to ask than to guess.
Existing trails: you can feel safe because you see a well-trodden path ahead of you. In our mountains, I was once walking along a seemingly excellent path, but I felt that the slope under the path was very unreliable. Just because someone has been here before you doesn't mean it's safe to walk here.
"Virgin Fever": You can turn a blind eye to the signs of avalanche danger when there is fresh, deep and untouched snow in front of you. Don't give in to temptation!
“Others have passed!”: It is very easy to succumb to the “herd instinct” and go on a dangerous slope when other people have already passed in front of you. Always assess the situation as if you are alone. Tell me if you feel something is wrong.

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FEDERAL STATE BUDGET EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL EDUCATION

"Tula state Pedagogical University them. L.N. Tolstoy"

(Federal State Budgetary Educational Institution of Higher Professional Education "Tashkent State Pedagogical University named after L.N. Tolstoy)

Speciality:“Pedagogical education with two profiles of training (mathematics, physics)”

Department: “Algebra, mathematical analysis and geometry"

By discipline:

"Life Safety"

on the topic: “Snow avalanche”

Completed by: st.gr. 120951(1A)

Afanasyeva T.M.

Head of work: Snegirev A.V.

Introduction

Concept and causes of avalanches

Consequences

Human actions during an avalanche

Prevention of dangerous situations

Providing first aid to an avalanche victim

Conclusion

Bibliography

Introduction

Snow avalanches are one of the natural natural phenomena, capable of causing loss of life and significant destruction. Among other dangers, avalanches are distinguished by the fact that their collapse can be caused by human activity.

Reckless use of natural resources in mountainous regions (deforestation on slopes, placement of objects in open avalanche-prone areas), access by people to snow-covered slopes, and shaking of the snow column from equipment lead to increased avalanche activity and are accompanied by casualties and material damage.

The problem of snow avalanches is most pressing in places where ski resorts and tourism flourish, for example Switzerland, Kamchatka, the Pyrenees, Finland and others.

For my essay, I took the topic “snow avalanche” because this emergency situation is little studied in school or even not touched upon at all. Life is full of surprises and I could very well end up in such a situation, so I want to know how to behave and what to do.

· Study what avalanches are and what are the causes of their occurrence

· Find out what the consequences of an avalanche are

· Review the plan for dealing with this emergency.

· Find out how you can avoid this situation

· Find out what assistance needs to be provided to victims

Concept and causes

An avalanche is the rapid descent of snow cover from a mountain slope under the influence of gravity. Falling snow masses carry melt water, soil, and vegetation with them, but snow always predominates in an avalanche.

Avalanches are possible in all mountainous areas where snow cover is established. The possibility of avalanches is determined by the presence of a favorable combination of avalanche-forming factors, as well as slopes of steepness from 200 to 500 with a snow cover thickness of at least 30-50 cm.

Avalanche-forming factors include: snow cover height; snow density; snowfall intensity; snow cover subsidence; temperature regime of air and snow cover; snowstorm distribution of snow cover.

The most important factors are the increase in freshly fallen snow, the intensity of snowfall and blowing snow transport. In the absence of precipitation, melting may be a consequence of intensive snow melting under the influence of heat, solar radiation and the process of recrystallization, leading to the destruction of the snow layer.

The formation of avalanches occurs in the avalanche source, that is, in the area of the slope and its foot, within which the avalanche moves.

An avalanche source is usually characterized by three zones:

Origin zone (avalanche collection);

Transit zone (tray);

Stopping zone (cone) of an avalanche.

Avalanche classification

Avalanche type	Peculiarities
Tray	Movement along a fixed channel
Slopovaya	Separation and movement along the entire surface of the slopes
Jumping	Free fall from slope ledges
Reservoir	Movement along the surface of the underlying layer of snow
Unpaved	Movement on the ground surface
	Dry snow in an avalanche source
	Wet snow in an avalanche source

Up to 70% of avalanches are caused by snowfall. These avalanches occur during snowfalls or within 1-2 days after they stop.

Avalanches are classified according to their frequency (recurrence):

Systematic, go every year or once every 2-3 years;

Sporadic, disappear 1-2 times every 100 years or less, the location of the disappearance is difficult to determine.

In some areas, systematic avalanches can occur 15-20 times during winter and spring.

Heavy snowfalls, as well as earthquakes of magnitude 5-6 or more, are the causes of the formation of catastrophic avalanches.

Causes of snow avalanches

1. Good heavy snowfall at a speed of 2 cm/hour

2. Rain or prolonged thaw

3. Sudden temperature changes

4. Active solar radiation

5. Disturbance of the crust in the lower part of the slope - loose snow.

6. Strong wind

7. Powerful sound or mechanical impact

Consequences

Due to its suddenness, speed, and enormous destructive power, an avalanche destroys houses on its path, knocks down forests, power lines, roads, bridges, and kills all living things.

A person caught in an avalanche, in most cases, dies from suffocation. In the first moments when a person falls into an avalanche, he is mixed with snow, which clogs his nose and mouth, making it impossible to breathe. Being in the thickness of the snow, when breathing, an ice crust forms around a person, which prevents the passage of air. Except suffocation, man.

Anyone caught in an avalanche can freeze, break arms, legs, spine, get a head injury or a concussion. Just imagine: a huge snow mass of several hundred tons rushes down the mountain at a speed of 150-350 km/h, crushing everything in its path - stones, trees, people.

Human actions

· If the avalanche breaks high enough, quickly step or run out of the way of the avalanche without dangerous place or take cover behind a rock ledge, in a recess (you cannot hide behind young trees).

· If it is impossible to escape from an avalanche, free yourself from things, take a horizontal position, tucking your knees to your stomach and orienting your body in the direction of movement of the avalanche.

· Cover your nose and mouth with a mitten, scarf, collar; When moving in an avalanche, use swimming movements of your hands to try to stay on the surface of the avalanche, moving towards the edge where the speed is lower.

· When the avalanche has stopped, try to create space near your face and chest, it will help you breathe.

· If possible, move towards the top (the top can be determined using saliva, allowing it to flow out of the mouth).

· If you find yourself in an avalanche, do not scream - the snow completely absorbs sounds, and screams and meaningless movements only deprive you of strength, oxygen and warmth. You can stuff your mouth with a gag.

· Don’t lose your composure, don’t let yourself fall asleep, remember that they are looking for you (there are cases when people were rescued from an avalanche on the fifth and even thirteenth day).

If your companion is caught in an avalanche

· 1. Try to trace the path of its movement in the avalanche. After it stops, if there is no danger of repeated avalanches, start looking for your friend down from the place where you last saw him. As a rule, the victim lies between the point of disappearance and the location of the lightest items of his equipment.

· 2. Having found the victim, first of all free his Head and chest from snow, clear his airways, and then provide him with first aid before medical care.

· 3. If within half an hour it was not possible to find the victim on your own, you must call a rescue squad.

HOW TO ACT AFTER AN AVALANCHE

· If you find yourself outside the avalanche zone, report the incident by any means to the administration of the nearest settlement and begin searching and rescuing the victims.

· After getting out from under the snow on your own or with the help of rescuers, inspect your body and, if necessary, provide yourself with help. When you reach the nearest populated area, report the incident to the local administration. Go to a health center or doctor, even if you think you are healthy. Next, act as directed by the doctor or rescue team leader.

· Inform your family and friends about your condition and whereabouts.

How to look for people under an avalanche?

Survival under an avalanche of people depends on how effectively your comrades search for them. Panic and confusion at such a moment can cost the lives of those trapped in the snow. So, how to properly look for a person under an avalanche?

· The location of the victim is often indicated by his belongings (backpack, tent, etc.) thrown onto the surface of the snow cover. In addition, a special avalanche tape attached to personal equipment can be a real salvation in such cases.

· If neither things nor avalanche tape could be found, you should visually determine the places where the victim is likely to be buried. Most often these are natural barriers, avalanche curves, trees, rocks, etc. At the same time, it is important to remember where the person was at the time of the avalanche and find out where the snow flow could have transported him, based on its direction and strength.

· You can search for people under an avalanche using a radio (if you have one). Speed probing, which has been tested for centuries - the introduction of probes (long sticks) can also be quite effective. The probes should be used carefully, slowly, without sudden movements. To increase sensitivity, it is better to take off your gloves and immerse the probe in the snow with one hand. It is advisable to probe the area with a chain, with an interval of 1 meter between rescuers. When such a chain moves forward, the probe should be immersed every 70 cm.

Prevention of dangerous situations

Signs of an avalanche zone

1. Avalanches rarely occur on slopes with a steepness of less than 25°.

2. Avalanches sometimes occur on slopes with a steepness of 25 to 35°, especially when this is facilitated by the cutting action of skis.

3. The most dangerous slopes are steeper than 35°. In such places, avalanches are likely with every heavy snowfall.

4. Steep, narrow ravines -- natural ways avalanches

5. Forest ridges, especially those tapering upward, can be avalanche routes.

6. Avalanches rarely occur in dense forests.

7. Slopes with isolated trees are no safer than completely treeless ones.

8. Leeward slopes are favorable for the accumulation of excess amounts of loose snow and the formation of snow boards. The protrusion of the snow cornice is directed towards the leeward slope. The snowdrifts are elongated perpendicular to the direction of the wind, with the leeward slope being steeper.

9. In ravines located perpendicular to the wind, the accumulation of loose snow or the formation of snow boards occurs mainly on the leeward slope.

10. On windward slopes, the snow cover is usually strongly compacted by the wind and is safe.

11. Slopes facing south are favorable for the formation of wet avalanches in the spring and avalanches from fresh snow under the influence of sunlight.

Follow the basic rules of behavior in avalanche areas:

· do not go to the mountains in snowfall and bad weather;

· while in the mountains, monitor the weather changes;

· when going out into the mountains, be aware of possible avalanche sites in the area of your path or walk.

Avoidavalanchedangersbythe followingmeasures:

1. Choose your route carefully. Research known avalanche paths, prevailing winds, and recent snowstorm data. A good source of information is your nearest avalanche guide or ski patrol leader.

2. Avoid known dangerous slopes. Cross a questionable slope one person at a time and as high up the slope as possible or as far away from the possible avalanche site. It is safe to follow the ridge crest, but do not walk on the ledge of the cornice.

3. Be careful. As you move, constantly monitor the snow conditions. Before going out on a big slope, test a small one with the same steepness and orientation in relation to the sun. If you see an avalanche trail from a snow board, know that a similar avalanche may be waiting for you nearby. Watch your shadow. When it is directed towards a slope, the exposure to the sun is greatest. Seek protection in dense forest, on windward slopes and behind natural barriers. Watch the weather: any sudden change is dangerous.

4. Use your time wisely. Wait out a strong storm and for some time after it, until the avalanches disappear or until the snow settles. Control your every step. In the very first hours of the storm, movement is possible. Use this time to exit the avalanche area. In spring, the period between ten o'clock in the morning and sunset is the most dangerous for avalanches. The early morning hours before sunrise are safest.

5. Use self-defense. If you still need to cross a very dangerous place, have one person on skis check the slope. This person must be secured with a climbing rope and avalanche cord. Don't be satisfied with just one check.

Typical avalanche weather conditions

· Large amounts of snow falling in a short period of time

· Heavy rain

Significant wind transfer of snow

· Prolonged cold and clear period following intense rainfall or snowstorm

· Snowfalls are initially cold, then warm or vice versa

Rapid rise in temperature (around or above 0°C) after a long cold period

Long periods (more than 24 hours) with temperatures close to 0°C

· Intense solar radiation

Preventing a dangerous situation

The rate of change in snow cover is measured using meteorological instruments or using stationary avalanche rods, installed vertically in areas of avalanche danger and allowing one to monitor the level of snow cover on potentially dangerous slopes from a great distance. If, as a result of observations, it is determined that the level of snow cover reaches a critical level, dangerous slopes are fired from special weapons in order to artificially provoke small avalanches and prevent a global avalanche, which can lead to destruction and human casualties.

Protection of the population from avalanches can also be passive. With passive protection, avalanche slopes are avoided or barrier shields are placed on them. In order to protect against avalanches, forest belts are planted along the roads and protective shields are installed.

First aid

In the event that a person is discovered under the snow in one way or another, it is important to very quickly extract him to the surface. To do this, you need to start intensive digging, using both shovels and improvised tools - metal sheets, etc. However, intensive digging must be careful at the same time, because there is always a risk of causing serious injury to a person with a shovel or something else.

When rescuing a victim from an avalanche, the first thing you need to do is free his mouth and nose to breathe. Moreover, if breathing and heartbeat are no longer observed, it is important to immediately apply cardiopulmonary resuscitation - mouth-to-mouth artificial respiration. While one person carries out resuscitation efforts, others should continue to dig out.

A victim removed from an avalanche without signs of life or with a weak pulse should be tried to be brought back to life with the help of a heart massage, without stopping artificial respiration. At the same time, regardless of the person’s condition, he must be placed in a tent, warmed with warm clothes and heating pads (including those improvised from plastic bags).

A rescued person who is conscious (or after consciousness returns to him) should be given a hot drink (coffee, tea, broth, milk, etc.). Any tonic will be useful. The simplest of them is caffeine, which can be taken along with coffee, in the form of tablets or an injection.

The victim can be transported or moved from place to place only after he has resumed normal cardiac activity and breathing.

Conclusion

This work examined avalanches, the causes of their occurrence and the consequences of their descent, and also provided measures taken by people to protect themselves, the rules of behavior of a person caught in this emergency situation and the provision of first aid to victims. As a result, we can conclude that most often the causes of an avalanche are natural, such as heavy snowfall or a sharp change in temperature. To avoid getting into such a situation, you should take precautions and try not to go into avalanche-prone areas, and also know how to behave if you do end up in an avalanche.

snow avalanche help victim

Literature

1. Bozhinsky A.N., Losev K.S. Basics of avalanche science. - L.: Gidrometeoizdat, 2009. 280 p.

2. Gvozdetsky N. A. Mountains. - M.: Mysl, 2007. 400 p.

3. Geography of avalanches. - M.: Moscow State University Publishing House, 2006, 334 p.

4. Dolgushin L.D., Glaciers. - M.: Mysl, 2006. 448 p.

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