Avalanche formation. Misconceptions about avalanches (based on ANENA materials). Dry avalanche

“It would seem that the cold inherent in the snow should have given it the numbness of winter, and the whiteness the immobility of the shroud. However, this is refuted by the rapid movement. An avalanche is snow that has become a fiery furnace. It is icy, but it devours everything.” Victor Hugo

“An avalanche is an unforgettable sight. First, somewhere in the heights there is a dull sound, and then the silent mountains seem to come to life. A huge cloud of snow rushes down the slope, sparkling with millions of snowflakes. Then it reached the bottom of the valley, spread out across it, snow dust flew up high, and everything disappeared as if in a fog... After some time, the snow dust settled down, but the bottom the valleys were blocked by shapeless piles of snow, so dense that they looked like pieces of snow. Branches, fragments of tree trunks, and stones stuck out in them.” (3) Like all the elemental forces of the Earth, it is a beautiful and terrible sight.

Two of the world's greatest avalanche disasters to occur in this century occurred in Peru in the Santa River Valley. January 10, 1962 At the top of Huascarana, a huge snow cornice about 1 km wide and more than 30 m thick broke off. This happened in the evening - a dull roar echoed for many kilometers, shaking the gorges. “A mass of snow and ice with a volume of approximately 3 million m3 rushed down at a speed of 150 km/h, carrying with it boulders, sand, and rubble. The huge shaft grew at lightning speed, and minutes later a mass with a volume of at least 10 million m3 moved along the steep valley, crushing everything in its path. After 7 minutes, the avalanche reached the town of Ranairkai and swept away its face of the Earth. Only after 16 km, having descended 4 km and spread out across a wide valley for 1.5 km, it stopped, damming the river." (1) The damage from the Huascaran avalanche was enormous: about 4 thousand people died, up to 10 thousand domestic animals.

After 8 years, a similar event repeated itself, but only on an even larger scale. May 31, 1970. In the Cordillera Blanca, where the peak of Huascaran is located, a strong earthquake occurred, which tore off at least 5 million m3 of snow and ice from the slopes. Along the way, the avalanche broke off a significant part of the underlying glacier and rushed, tearing off a thick layer of loose rock and carrying away huge stones. On the way, the avalanche lowered a small lake, which gave the entire mass even greater strength. A gigantic amount of snow, ice and mountain rock rushed through the valley at a speed of 320 km/h - 50 million m3! The avalanche overcame an obstacle 140 m high, again destroying the newly rebuilt village of Ranairka and the city of Yungai, which in 1963 saved the low hill. The mass of snow, water and stones covered almost 17 km. The consequences were terrible: out of 20 thousand inhabitants, only a few hundred people survived. Such terrible avalanches happen rarely, but avalanches of normal sizes are a formidable element of the mountains.

The ancient German word "lafina" comes from the Latin "labina", that is, sliding, landslide. Bishop Isidore of Seville (570-636 AD) mentioned “labines” and “avalanches” - this is the first literary source. In folklore, avalanches are called “white death”, “white dragons”, “white brides” and so on.

“Avalanches became of interest to man only when they began to disturb him, that is, when man began to inhabit the mountains. At the same time, avalanches became interested in man – the so-called unhealthy interest. Having arisen at a time when the Earth squeezed out mountain ranges from itself, and the first snow fell from the sky, avalanches took millions of years to get used to to solitude and therefore met its violators with hostility: why should one expect anything else from a bear sleeping peacefully in a den, which people woke up with whistling and hooting? (5)

Information about snow avalanches has come down from ancient times. In 218 BC. They caused a lot of harm to the troops of the Carthaginian commander Hannibal, who was crossing the Alps. Then many people and animals died under avalanches - every fifth foot warrior (60 thousand people), every second horseman (6 thousand), and 36 elephants out of 37 that took part in this transition.

In addition, the history of the crossing of the Alps by Suvorov’s army in 1799 is known. And here avalanches made it difficult for the army to operate on the dangerous St. Gotthard Pass.

During the First World War, when the Alps were in the sphere of military operations, about 60 thousand people died in avalanches - more than as a result of military actions. On just one “Black Thursday”, December 16, 1916, more than 6 thousand soldiers were buried in avalanches.

Peacetime losses are immeasurably smaller, but they are noticeable.

Nowadays, the Alps, “inhabited by people like bees and bees,” especially suffer from avalanches (5) From the beginning of this century to 1970. in the Swiss Alps, 1,244 people died from avalanches. In total, there are 20 thousand avalanche sites in the Alps, of which more than 10 thousand are permanent avalanche sites, and 3 thousand of them threaten populated areas, roads, and communication power lines..

“Avalanches are rampant in both Americas, they fall from the peaks of the Tien Shan, they create scandals in the Khibiny Mountains, in Siberia, in Kamchatka and in general in all mountainous regions.”(5)

“In the Caucasus, the lavains lie in wait for travelers and exact many victims,” writes Strabo in his “Geography” 2000 years ago. During the Great Patriotic War in the winter of 42/43, special units of military climbers artificially caused avalanches, thus destroying enemies.

Winter 1986/87 It was exceptionally snowy in the Caucasus - snow fell 2-3 times more than usual. In Svaneti it snowed non-stop for 46 days and gave rise to countless avalanches. Almost all the ancient houses in which people lived from the 10th to the 12th centuries were destroyed. Salvation from the “white death” could only be found in ancient towers 8-15 m high, where people once escaped from enemies.

An avalanche is a mass of snow that comes moving on a slope. "Avalanches are the most unpretentious creatures: in order to bring them to life, you only need snow and mountains with suitable slopes. Snow for avalanches is manna from heaven, the only source of food. During snowfall, it collects in avalanche collection, at the very top, in order to then choose the right moment to rush at terrible speed along tray down and form at the place of convergence avalanche cone sometimes with a thickness of several tens of meters."(5).

The fluffy blanket of snow in the mountains only looks harmless from a distance. Austrian researcher Matthias Zdagarsky said this: “Innocent-looking white snow is a wolf in sheep’s clothing, and a tiger in lamb’s clothing.” “Suitable” slopes for avalanches have a steepness of 15-45 degrees. On gentler slopes the snow flows gradually, but on steeper slopes it does not linger. Avalanche tray- a trench on a slope along which avalanches descend (as a rule, they descend along the same path).

The area of ​​the mountain slope and valley floor where an avalanche forms, moves and stops is called avalanche collection.At the top is avalanche source– place of origin, and below – channels avalanche cone.(Fig.1)

In the zone of origin, the avalanche gains strength, captures the first portions of snow from the slope and quickly turns into a stormy stream, sweeping away everything in its path. In the transit zone, it rushes down the slope, increasingly increasing its mass, breaking bushes and trees. Gradually, the movement slows down, masses of snow pile up in the form of an avalanche alluvial cone. Here, an avalanche deposition zone is formed. In the deposition zone, snow cones with a thickness of 5 to 30 m, and sometimes more, are formed. Winter 1910/11 the avalanche of the Bzyken Caucasus ridge left the river gorge. The white slope is 100 m thick. The snow melted in it for several years.

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, loose, like sand. Such snow easily generates avalanches. Avalanche danger increases many times over when snowfalls are accompanied by wind. When there is a strong wind on the surface of the snow, a wind, or snow, board is formed - 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 occur in winter after heavy snowfall without thaw, when the blowing snow on the ridges and steep slopes reaches such a size that the shock of the air from a gust of wind, a shot, even loud screaming causes them to burst out. The latter is greatly facilitated if fresh snow falls on the smooth surface of old snow, captured after a thaw and frost. These avalanches fly down and at the same time fill the air with snow dust, forming a whole cloud." (2) (Fig. 3)

In the absence of snowfalls, 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. This is what 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 thickness is quickly destroyed, and then enormous “wet” avalanches are formed. They fall in the spring over large areas, sometimes capturing all the snow that has accumulated over the winter. They are also called ground avalanches because they move straight along the ground and tear up 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. The supports keep the snow on the slope until the shear resistance forces (the adhesion of the snow to its lower layers or soil and the force of friction). In addition, the shift of the layer is prevented by the snow cover located below and held by the one that lies above. Snowfall or blizzard, recrystallization of the snow column, the appearance of liquid water in the thickness leads to a redistribution of forces acting on the snow.

Snowfall overloads the slopes with snow, and the forces holding the snow do not keep up with the increase in gravity tending to move it. Recrystallization weakens individual horizons, reducing the 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.

In order for an avalanche to move, it needs a first impulse. Such triggering mechanisms are heavy snowfalls or heavy snowstorms, warming, warm rain, cutting snow with skis, vibration from a sound or shock wave, and earthquakes.

Avalanches begin to move either “from a point” (when the stability of a very small volume of snow is disrupted), or “from the line” (when the stability of a large layer of snow is disrupted at once) (Fig. 2). The looser the snow, the less it is needed to start an avalanche. The movement begins with just a few particles. An avalanche from a snow board begins with cracking of the snow cover. A narrow crack quickly grows, side cracks are born 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 grows due to the accumulation of new portions of snow (almost all ancient engravings depicted an avalanche this way). The ball avalanche was represented until the 19th century. The variety of snow avalanches and the many forms of its movement made it difficult to understand the physics of avalanches. An avalanche is a multicomponent flow, because it consists of snow, air and solid inclusions. The physics of such flows is very complex.

The forms of movement of an avalanche are varied. Snow pellets can roll in it, snow balls and fragments of a snow board can slide and rotate, a solid mass of snow can flow like water, or a snow-dust cloud can 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 the avalanche moves faster than its main body due to the collapse of the snow cover in front of the front from the avalanche impact. Thus, more and more new portions of snow are included in the avalanche, while in the tail part the speeds drop. On the crests of waves that arise on the surface of a moving avalanche, stone fragments appear, 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.

The speed of avalanches varies from 115 to 180 km/h, sometimes reaching 400 km/h.

Avalanches have enormous impact force, easily smashing wooden houses into pieces. Even concrete buildings cannot withstand a frontal impact. If an avalanche fails to destroy a house, it pushes out doors and windows and fills the lower floor with snow. The avalanche does not spare anything that meets on its road. It twists metal power transmission masts, throws cars and tractors off the road, turns steam locomotives and diesel locomotives into a pile of scrap metal (in 1910, in the Cascade Mountains (USA) in the area of ​​​​Stevens Pass, an avalanche fell on a passenger train and smashed it into pieces. About 100 people died). She covers the roads with a layer of many meters of dense, ice-like snow. It destroys many hectares of forest at once; even hundred-year-old trees cannot withstand it. (Fig.4)

Jumping avalanches have a particularly strong impact effect (if there is a cliff or a sharp bend in the slope in the path of a snowfall, the avalanche “jumps” from it and sweeps through the air for some time). When an avalanche lands, knockout pits appear. In the New Zealand Alps, 16 lakes with an area of ​​200 to 50 thousand m2 were found in similar basins. All of them are located at the base of steep avalanche chutes.

To properly design avalanche structures, it is necessary to measure the force of the impact. Back in the 30s in our country, a railway car buffer with a powerful spring was used for this, which was fixed in the path of the avalanche. The amount of compression of the spring upon impact was recorded with a metal rod. In Switzerland, along the path of an avalanche, a shield was installed, on the reverse side of which there was a pointed steel rod, and an aluminum plate was fastened opposite it, into which the rod entered under the impact of the avalanche. The greater the pressure, the stronger the dent. Nowadays, complex devices are used that make it possible to obtain not only the maximum snow pressure, but also its change during the impact. Data show that avalanche pressures typically range from 5 to 50, although the impact of avalanches in Japan exceeded 300. In the table you can see the destruction caused by an avalanche impact of varying strengths:

To characterize avalanche danger, it is very important to know the range of the avalanche, i.e. the maximum distance that an avalanche can travel in a given avalanche collection. The ejection range ranges from a few tens of meters to 10-20 km. The Huascaran avalanche in Peru traveled almost 17 km. The longest range in the former USSR was recorded in the Kzylcha river basin in the Tien Shan; the avalanche traveled 6.5 km here. In most cases in the mountains of our country, the range of avalanches is from 0.5 to 1.5 km.

Dust avalanches have special properties - a mixture of dry snow and air of very low density, accompanied by a cloud of snow dust. They have enormous speed and great destructive power. With a slight change in movement in a dust avalanche, shock waves arise, creating a rumble and roar that accompanies the avalanche. Such avalanches are capable of moving multi-ton objects. In the Rocky Mountains, a powerful dust avalanche carried a truck weighing more than 3 tons and an excavator bucket weighing more than 1 ton 20 m to the side and then dumped them into a ravine.

Often, avalanches of dry snow are accompanied not only by a snow-dust cloud, but also by an air wave that causes destruction outside the zone of deposition of the main mass of avalanche snow. So, in the Swiss Alps, 1.5 km from the avalanche stop site, an air wave knocked out the glass windows of houses. And in another place, an air wave moved a railway car 80 m away, and a 120-ton electric train lifted the station building. A particularly tragic incident occurred in Switzerland in 1908. A small avalanche stopped a few meters in front of the building, however, the building was destroyed, the roof was carried away to the opposite slope of the valley, and 12 people sitting at a table facing the avalanche were suffocated by a sharp change in air pressure.

Scientific research into avalanches began in the Alps. In 1881, the first book about avalanches by I. Koatz, “Avalanches of the Swiss Alps,” was published. In 1932 In Switzerland, the Avalanche Commission was created to develop a research program on snow and avalanches. This was necessary to protect against avalanches from the growing railway network that covered almost the entire Alps. A small research group led by Professor R. Hefeli began a comprehensive study of avalanche problems in the Weißflujoch area, located above Davos. In 1938, the professor’s book “Snow and Its Metamorphisms” was published, summing up the results of the first stage of work. On the site of a wooden hut on Weißflujoch, at an altitude of 2,700 m above sea level, the Swiss Snow and Avalanche Institute was built - now the world's leading center for avalanche research.

Then, in the 30s, great interest in avalanches was shown in the Caucasus, where the design of trans-Caucasian roads began, and in the Khibiny Mountains, where rich apatite deposits began to be developed in 1936. A special anti-avalanche service was created at the Apatit plant. Already then, such difficult problems as calculating the stability of snow on a slope, the theory of avalanche movement, designing avalanche structures were being studied. In the post-war years, extensive research on avalanches began in the mountains of Central Asia and the Caucasus, the Carpathians and Siberia. A great contribution was made by the work of the Institute of Geophysics of the Academy of Sciences of Georgia and the High Mountain Geophysical Institute in Nalchik, Problem Laboratory avalanches of mudflows at MSU. MSU expeditions studied avalanches on the route of the future BAM from 1946 to 1975.

Currently, avalanche research is carried out mainly by the hydrometeorological service. Snow avalanche stations are especially important, the tasks of which include meteorological observations, regular measurements of the thickness, density and physical and mechanical properties of snow, and recording of avalanches. At such stations, laboratory studies of snow are carried out, descriptions of avalanches on selected routes, and avalanche forecasts are given based on local signs and local connections with meteorological indicators. Snow avalanche stations transmit avalanche danger bulletins to all interested institutions every few days. Such stations now exist in almost all mountain ranges.

In recent years, avalanche schools have become increasingly popular. Their task is to introduce the violent nature of avalanches, teach the rules of behavior in avalanche-prone areas, and convey the experience of predicting and preventing avalanches.

The newspaper "Avalanches" is published in the USA. It publishes information about avalanche conditions, avalanche research, experience in preventing and combating them, advertises new devices and equipment, and talks about avalanche workers and their work. It also reports on classes at avalanche schools, of which there are about 20 in the USA and Canada, and on seminars and symposiums on avalanche topics.

In Russia, scientific and practical seminars are also held in half of the world. However, regularly operating avalanche schools have not yet been created.

The disappointing statistics of the catastrophic consequences of avalanches puts the task of avalanche prevention and protection in the first place. Back in the 15th century. in the Alps they shot from firearms in order to cause snow to fall with the sound of the shot. Now shelling avalanche-prone slopes is the most common way to combat avalanches. In many places, permanent “firing” positions have been established. They use field and anti-aircraft guns, mortars and howitzers. Through artificial shelling, it is possible to cause smaller avalanches: “a runaway cone is piled up below, now a hundred-thousand-ton mass of avalanche snow is no longer threatening to anyone. On a kilometer-long slope, chutes and couloirs are empty, the soil turns black, bare stones - all the snow has been torn down: an ugly, but sweet picture to the avalanche hunter’s heart. We have our own concepts of beauty: a bare slope and avalanche cone pile - This is truly frozen music! "(5)

Artillery systems for firing avalanches must be lightweight, mobile, provide high accuracy and have a range of 2-3 km, a powerful projectile with a small number of fragments, and special reliability. Unfortunately, there are cases when shells fly to the opposite slope and up to 1% of fired shells do not explode. All this limits the use of anti-avalanche artillery.

Sometimes shelling can play a fatal role in catastrophic avalanches. This happened in the Swiss town of Zuots in 1951. The slopes were overloaded with snow and a fatal decision was made - to shell the surrounding mountains. The first shots caused the snow to move, and soon a terrible avalanche descended. She swept away an artillery position and 32 houses in the town.

The dangerous method of cutting snow with skis is still practiced, but there are many known cases when an avalanche carried away a skier, not always leaving him alive. Sometimes mines are laid in advance in the nucleation zones, exploding them at the right moment by radio. In Kyrgyzstan, a powerful charge was placed at the foot, so that the blast wave spreads up the slope and releases unstable snow. Recently, mass avalanche discharges using shock waves produced by low-flying supersonic aircraft have begun to be used.

Snow cover on a slope can be secured using snow-retaining shields, fences, and nets. In Switzerland, over the last hundred years, hundreds of kilometers of such structures have been installed. In blizzard areas, high multi-row fences are installed that prevent the formation of dangerous accumulations of snow near snow cornices. In avalanche hotspots, special snow-blowing shields are placed - kolktofel (two shields, combined perpendicular to each other). The blowing wind blows them, forming blowing funnels around them. So uneven snow cover turns out to be much more durable. To prevent movement of the snow layer, flexible metal meshes are stretched over the slope.

In the middle part of the slope on the path of an avalanche it is necessary to build powerful structures: wedges, mounds, and over-cuts. Their task is to reduce the speed of the avalanche, break it into pieces and slow it down. And to stop the avalanche, dams are built. They are placed at the exit of an avalanche, when its energy is no longer enough to overcome an obstacle. Sometimes a dam is placed so that it does not stop the avalanche, but deflects it, changing the path of the avalanche. To protect the mast of power line supports, avalanche cutters are used - wedge-shaped structures that cut through the rushing snow, forcing it to flow around structures. In Davos there is a church built back in the 16th century. In 1602, it was demolished by an avalanche, but, having been restored, it was no longer destroyed, although it was not covered almost to the roof by avalanche snow. The shape of the back wall, built like a wedge towards the avalanche ravine, helped.

Roads in the mountains are laid so that they avoid avalanche-dangerous slopes whenever possible. Sometimes it is necessary to pave a road along a slope, protecting it with the help of an avalanche pass - a concrete chute that directs the avalanche over the road or with the help of a gallery that covers the road from the avalanche. (Fig. 5, 6)

Forests play a huge role in preventing avalanches. Where a continuous forest grows, consisting of different types of trees of unequal age, it prevents avalanches from forming. The snow cover in the forest creates a continuous layer, and if the snow begins to slide down the slope, its pressure is absorbed by the tree trunks. They bend, but hold onto the snow and do not allow it to begin dangerous movement. The forest is absolutely reliable when its upper boundary rises to the avalanche zone. If it is destroyed by an avalanche, burned by a forest fire, or cut down by people, it takes decades to restore it. And during this period, there are many snowy winters, and then avalanches go where the forests previously did not allow them. Forestation in the mountains is extremely difficult. Avalanches often occur in treeless areas, and seedlings must be protected in order to grow, protecting plantings with earthen banks and dams, wooden and metal fences, poles and overdoubles. This is difficult and expensive, but still much cheaper than the construction of stationary avalanche structures. Forest protection is natural, rational and reliable.

“An avalanche is safe only when it is dead, that is, lowered down.” (5) Avalanche danger awaits a person on a variety of slopes. In the mountains, you need to carefully choose a route, avoid known dangerous slopes. In an avalanche zone, you need to be attentive to all extraneous sounds and movements: “an avalanche behaves honestly for the only time in its life: before it breaks, it makes a guttural sound: “thump!” wow! ", leaving a few stunningly fleeting seconds for reflection. If you find yourself on the slope alone, scramble to the side with all the speed available to you..." (5) Sad events associated with avalanches usually arise from the fact that people forget or ignore the simplest rules of behavior in the mountains, naively believing that nothing bad can happen to them. “What avalanches really can’t stand are reckless people who forget about everything in the world at the sight of a snow-covered slope; however, except for good snowfall, they love no one and nothing at all” (5).

Once in an avalanche, a person has almost no chance of getting out of it while moving, and very soon finds himself buried in avalanche snow. An avalanche kills its victim using cold, shock, and suffocation. Most often, suffocation occurs: while moving in an avalanche, snow dust clogs the nostrils and throat, and sometimes even penetrates the lungs; after the avalanche stops, the hardening snow compresses the chest and impairs breathing; a dense avalanche rubble is almost not ventilated, and there is very soon a lack of air for breathing; finally, even if a person in the rubble has some space, soon an icy crust appears on the inside of the snow resting cavity, finally clogging the victim. Finding himself in the snow, a person is deprived of the opportunity to announce himself by shouting. The sounds coming from the snow do not come up. The immured victim hears the sounds of the rescuers’ steps and everything that is happening on the surface of the snow, but cannot communicate anything to himself.

Starting from the 13th century, dogs began to be used in searches, even a special breed of St. Bernards was bred, trained to work in the rubble of avalanche snow. A well-trained dog can examine a 1-hectare area of ​​rubble in just half an hour. It easily finds prey at a depth of 2-3 m, and under favorable conditions even at a depth of 5-6 m. The use of dogs is very difficult in wet and contaminated snow, in severe frost and strong winds. In the Alps, avalanche dogs are trained in special schools. They participated in 305 rescue operations and found 269 people, but only 45 of them were able to be brought back to life, in other cases it was too late.

The main thing in search and rescue is efficiency. During the first hour of being in an avalanche, a person retains a 50% chance of surviving, and after three hours it does not exceed 10%. When there are no dogs, searches are carried out using an avalanche probe. A 1-hectare area of ​​the dam is inspected by 20 rescuers in 4 hours. If sounding is not successful, and it is known that the avalanche buried people in this area, they begin to dig longitudinal trenches in the rubble - one from the other at a distance of the length of the avalanche probe. This is labor-intensive and ineffective work. Receiving and transmitting devices are used: if someone caught in an avalanche has a miniature transmitter, it can be easily found from the surface. The long-standing traditional method of marking those in trouble is avalanche cords 30-40 m long, painted in bright colors. They are attached to the handle of a ski pole, and when a person falls into an avalanche, they unravel and may end up on the surface of the avalanche. Such a happy outcome does not always happen.

Today, the search for avalanche victims remains a serious problem, and therefore it is still important to provide advance warning of avalanche danger using all modern media.

In conclusion, I would like to cite two stories of famous avalanche climbers M. Otwater and M. Zdarsky, who themselves were in an avalanche and remained alive after that.

M. Otwater, American avalanche expert: “... It was an avalanche made of a soft snow board, and, consequently, the entire slope became unstable. I found myself as a sliver of wood floating in a stream of snow... I was immersed knee-deep in boiling snow, then waist-deep, then neck-deep...

Very quickly and suddenly, I was flipped forward twice, like a pair of trousers in a clothes dryer... The avalanche took my skis off and thereby saved my life, giving up the lever with which it could have twisted me...

I traveled all this way under the snow... Instead of the shine of the sun and snow, which are never as bright as immediately after a snowfall, there was complete darkness in the avalanche - foaming, twisting, and in it it was as if millions of hands were fighting with me. I began to lose consciousness, the darkness came from within.

Suddenly I found myself on the surface, in the rays of the sun. Having spat out a snow gag from my mouth and taking a deep breath, I thought: “This is why those killed in an avalanche always have their mouths full of snow!” You fight like the devil, your mouth is wide open to take in more air, and the avalanche fills it with snow.

When I was next thrown to the surface, I managed to take two breaths. So it happened several times: up, take breaths, swim to the shore - and down, covered in snow, spinning into a ball. It seemed to drag on for a long time, and I began to lose consciousness again. Then I felt that the snowfall was slowing down and becoming more dense. Instinctively or in the last flicker of consciousness, I made a desperate effort and the avalanche spat me out onto the surface like a cherry pit."

Matthias Zdarsky once fell into an avalanche. Here is the description he left: “At that moment... the roar of an avalanche was heard; shouting loudly to his companions, who had taken refuge under a rocky wall: “Avalanche! Stay there!" - I ran to the edge of the avalanche lair, but before I could make three jumps, something blocked the sun: like a giant sling, about 60-100 meters across, a black and white spotted monster was descending on me from the western wall. I was dragged into the abyss... It seemed to me that I was deprived of arms and legs, like a mythical mermaid, and finally I felt a strong blow to the lower back. The snow pressed on me more and more, my mouth was filled with ice, my eyes seemed to be coming out of their sockets, blood threatened to spurt out of my pores. It felt like my insides were being pulled out, like an avalanche cord. I had only one desire - to quickly go to a better world. But the avalanche slowed down, the pressure continued to increase, my ribs were cracking, my neck was twisted to the side, and I already thought: “It’s all over!” But my avalanche suddenly fell into another and broke it into pieces. With a distinct “Damn” with you!" the avalanche spat me out."

Zdarsky had eighty fractures - he not only survived, but also

eleven years later I started skiing again!

A little history of avalanches.

What are avalanches and what types of them are there?

Causes of occurrence.

The way she moves.

What can it do?

Avalanche Research.

Methods of combating avalanches.

Why is it dangerous for humans?

Ways to save people.

Two eyewitness accounts.

List of used literature:

Kotlyakov V.M. World of snow and ice. M.: Nauka, 1994

Obruchev V.A. Entertaining geology M.: publishing house of the USSR Academy of Sciences, 1961

Encyclopedia for children: GEOGRAPHY. M.: Avanta+, 1997

Encyclopedia for children: GEOLOGY.M.: Avanta+, 1995

SaninV. White curse.

A snow avalanche is one of the most dangerous natural phenomena that 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 rare cases, not only the snow melts, 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. On ski slopes There are also risks of avalanches. 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 employees rescue services informed in advance that this was 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, wind create hazardous conditions, so it’s 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.

Most dangerous period An avalanche is considered to occur in 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 of the 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 outside world 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

Matthias Zdarsky, an Austrian researcher who studied the question of what an avalanche is, called the innocent, at first glance, white snow a tiger in lamb's skin. Softly falling snow fascinates even those who don’t like winter - too much Nice picture, similar to fairy tale. And the crystal stars smoothly falling to the ground create a deceptive impression of fragility and defenseless tenderness. However, excessively active snowfalls are fraught with danger, and a serious one. After all, not only snowdrifts, but also avalanches can grow from small snowflakes. So what is an avalanche? The definition of this concept is given below. And now a little history.

A brief excursion into history

In all likelihood, an avalanche is a phenomenon that exists as long as the steep slopes of mountains, and Polybius mentions the first large-scale snowfalls, causing the death of hundreds of people, in the context of the history of the campaign of the Carthaginian army through the Alps. And in general, this mountain range, beloved by tourists and climbers, has a long history of disasters behind it. It is not for nothing that in the 20th century, in some areas, masses were celebrated in memory of those killed under snow rubble, because in this case an avalanche means pain and grief for the relatives and friends of those who suffered from it. It is also noteworthy that in one of the last winters of the First World War, more soldiers died from this on the Austro-Italian front than directly during hostilities. And December 16, 1916 went down in history as “Black Thursday,” when six thousand people were missing in one day. Hemingway, who was in the Alps during the same time period and described his definition of what an avalanche means, noted that winter landslides are terrible, sudden and bring with them instant death.

Residents of Norway, Iceland, Bulgaria, the United States, the Russian Federation, Canada, as well as Asian countries: Turkey, Nepal, Iran, Afghanistan also suffered from the “white death”, and in the latter, by and large, no records of the dead are kept. Tens of thousands of lives were also attributed to snow avalanches that fell from Mount Huascaran in Peru.

What is an avalanche? Etymology of the word

The ancient Romans called this phenomenon a “pile of snow.” Each nation had its own definition. What does avalanche mean? This is a beautiful, exciting and dangerous natural phenomenon. The very meaning of the word “avalanche” is also interesting, the origins of which are the Latin root lab, meaning “instability”, although it came into the Russian language through German, since in ancient German there was a definition of Lavine. Xuan Zang poetically called them “white dragons,” and in Pushkin’s time avalanches were called landslides. In the Alps and the Caucasus, the names of individual mountains, gorges and valleys are already “speaking”. For example, Lansky Forest or Zeygalan Khokh (“the mountain from which avalanches always come down”). Sometimes the ability to read onomastics, although it won’t tell you everything about snow debris, can protect you from unforeseen circumstances.

What is an avalanche

An avalanche is a type of landslide, a significant mass of snow that moves or even falls from the slopes of mountains under the influence of gravity. It simultaneously creates an air wave, which accounts for a significant part of the destruction and damage that is almost inevitable in this natural disaster.

Having started its movement, the avalanche can no longer stop, falling lower and lower and capturing accompanying stones, ice blocks, branches and uprooted trees on its way, turning from seething white snow into a dirty mass, vaguely reminiscent of a mudflow. The flow can continue its “fascinating journey” until it stops in flat areas or at the bottom of the valley.

Factors influencing the descent of snow masses from the mountains

The reasons that cause avalanches largely depend on the old snow - its height and density, the condition of the surface underneath it, as well as on the increase in new masses of precipitation. The intensity of snowfall, subsidence and compaction of the cover, and air temperature also influence. In addition, a fairly long open slope (100-500 m) is optimal for the start of an avalanche path.

It is not for nothing that the main “architect” of this natural phenomenon is called the wind, since an increase of 10-15 cm is enough for the snow to melt. Temperature is also one of the most important factors that can provoke a disaster. Moreover, if at zero degrees the instability of the snow, although it arises quickly, passes no less actively (it either melts or an avalanche occurs). And when the low temperature is stable, the avalanche period increases.

Seismic vibrations can also activate snow melting, which is not uncommon in mountainous areas. In some cases, jet flights over dangerous zones are enough.

In general, the increasing frequency of snow avalanches is indirectly or directly related to stormy economic activity a person who is not always reasonable. For example, those cut down today forested areas They used to serve as a natural protection against snow slides.

Periodicity

Depending on the frequency of occurrence, intra-annual convergence is distinguished (for winter and spring periods) and the long-term average, which includes, respectively, the overall frequency of avalanche formation. There are also systematic avalanches (annually or every 2-3 years) and sporadic ones, which occur at most twice per century, which makes them especially unpredictable.

Movement, source of natural phenomenon

The nature of the movement of snow masses and the structure of the source determine the following classification: flume snow avalanches, special and jumping. In the case of the former, the snow moves either along a tray or along a specific channel. Special avalanches cover the entire accessible area of ​​​​the terrain while moving. But with the jumping ones it’s already more interesting - they are degenerated from the flume, appearing in places where the drainage is uneven. The snow mass has to “bounce”, as it were, to overcome certain areas. The latter type is capable of developing highest speed Therefore, the danger is very significant.

Snow is treacherous and may well creep up unnoticed and silently, falling with an unexpected shock wave, destroying everything in its path. The peculiarities of the movement of these natural masses underlie another division into types. It distinguishes a layer avalanche - this is when the movement occurs tangent to the surface of the snow located below, as well as a ground avalanche - it slides directly along the ground.

Scale

Depending on the damage caused, avalanches are usually divided into especially dangerous (they are also spontaneous) - the volume of material losses amazes the imagination with their scale, and simply dangerous - they complicate activities various organizations and threaten a peaceful, measured life settlements.

Properties of snow

It is also important to note the classification associated with the properties of the snow itself, which is the basis of the avalanche. There are dry, wet and wet. The former are characterized by high convergence speed and powerful destructive air wave, and the masses themselves are formed at fairly low temperatures after significant snowfalls. A wet avalanche is snow that has decided to leave its cozy slopes at temperatures above zero. The speed of movement here is lower than in the previous ones, however, the density of the cover is greater. In addition, the base can freeze, turning into a hard and dangerous layer. For wet avalanches, the raw material is viscous, wet snow, and the mass of each cubic meter is about 400-600 kg, and the movement speed is 10-20 m/sec.

Volumes

Well, the simplest division is small and almost harmless, medium and dangerous to humans, as well as large ones, which in their path wipe out buildings and trees from the face of the earth, and turn vehicles into a pile of scrap metal.

Is it possible to predict the occurrence of avalanches?

It is extremely difficult to predict avalanches with a high degree of probability, since snow is an element of nature, which, by and large, is practically unpredictable. Of course, there are maps of dangerous areas and both passive and active methods are being taken to prevent this phenomenon. However, the causes and consequences of avalanches can be different and very noticeable. Passive methods include special shield barriers, forest areas, and observation points for dangerous areas. Active actions consist of shelling areas of possible landslides from artillery and mortar installations in order to provoke the convergence of snow masses in small batches.

Snow avalanches sliding down the mountains in any of the options represent no matter how small or large they are. It is extremely important to take into account all the factors influencing the occurrence of snow masses and their movement along an uncertain route to unknown goals, so as not to sacrifice too expensive gifts to the elements.

All about avalanches: interesting facts

1. The avalanche speed can reach 100-300 km/h. A powerful air wave instantly turns houses into ruins, crushes rocks, and demolishes cable cars, uproots trees and destroys all life around.
2. Avalanches can come from any mountain. The main thing is that they are covered with snow. If there have been no avalanches in a certain area for 100 years, then there is always the possibility that they may occur at any time.
3. Approximately 40 thousand to 80 thousand people lost their lives during the First World War, they were buried under avalanches in the Alps. Data is approximate.
4. In America (California), people surrounded Mount St. Gabriel with deep ditches. Their dimensions are equal to football fields. Avalanches descending from the mountain linger in these ditches and do not roll into populated areas.
5. This destructive natural phenomenon is called differently among different peoples. The Austrians use the word "schneelaanen", which means "snow flow", the Italians say "valanga", the French - "avalanche". We call this phenomenon an avalanche.

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 weight is enough to cause a disaster. human body.

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.


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

How is avalanche risk calculated?

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

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

How dangerous is an avalanche?

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


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

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

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

So, the first article

Misconceptions about Avalanches.

Snow boards are easy to recognize - FALSE!

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

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

A slight slope is safe - WRONG!

There are no avalanches in the forest - WRONG!

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

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

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

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

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

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

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

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

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

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

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

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