Snow avalanches are one of the most dangerous. How to escape from an avalanche? Avalanche slopes: precautions

COURSE WORK

on the topic: “Snow avalanches - a threat to the sustainable development of mountain areas”

Introduction

1. General concept of avalanches

1.1 Example of avalanche disasters

2. The nature of avalanches

3. Cause of avalanches

4. Avalanche classification

4.1 Genetic classification

4.2 Morphological types

4.3.1 Level slopes

4.3.2 Narrow cuts

4.4.1 Avalanche sources

4.4.2 Avalanche pools

5. Avalanches and snow cover

6. Avalanches and terrain

7. Avalanches and vegetation cover

8. Avalanche protection

8.1 Avalanche control measures

Conclusion

Applications

Introduction

Every year the development of mountain areas increases - roads, mines, hydroelectric power stations are built, cities, recreation and sports centers are erected. The development of mountains is associated with numerous natural processes flowing here. These are earthquakes, avalanches, mudflows, landslides, collapses, catastrophic movements of glaciers. Such phenomena are accompanied by rapid displacements of huge masses of snow, rocks, mud-stone mixtures and powerful floods. The study of these catastrophic phenomena, the development of methods for their prediction and the justification of measures to protect against them are becoming relevant and practically significant.

Natural disasters in the mountains they arise due to exogenous processes. The most widespread natural phenomena, widespread throughout the mountains, include avalanches and mudflows. Familiarity with their main features, distribution and conditions of development shows the complexity of the problem of studying the nature of these phenomena and, in particular, developing forecasts. Many components of the natural environment are involved in the formation of avalanches and mudflows, each of which is in continuous change. The combination of various natural conditions leading to the formation of avalanches and mudflows turns out to be new each time, different from the previous ones.

Within an avalanche or mudflow region, only the main types can be distinguished, for example, meteorological situations that cause avalanches and mudflows. To predict individual avalanches or mudflows, special observations are required in a given avalanche collection area or basin. This is too labor-intensive and, most importantly, does not completely solve the security problem. The main direction in the fight against natural destructive processes during the development of mountainous territories is the organization of reliable protection against them. The most acceptable methods of protection against avalanches and mudflows these days are related to their localization. But a fundamental solution to the problem of protecting and combating avalanches lies in a set of measures that influence the course of avalanche and mudflow formation processes. These measures include the complete construction of avalanche catchment areas with snow retention structures, terracing and planting of plantations in the area of ​​the mudflow basin, and the construction of dams in mudflow channels.

Natural phenomena are closely interconnected. For example, avalanches form in small catchment areas in winter, and mudflows in summer; avalanche snowfields, creating dams in the riverbed, cause the emergence of mudflows when these dams break through; landslides and landslides prepare material for mudflows, etc. That is why the need for an integrated approach when developing systems of measures to protect against avalanches and mudflows becomes obvious. These activities should be aimed at such basic natural components as runoff, geological processes, and vegetation cover.

A special role in this regard belongs to the preservation and restoration of vegetation cover, especially forests. Deforestation on mountain slopes leads to soil erosion, avalanches and mudflows. Forest restoration is not only protection from these processes, but also the involvement of lands in economic turnover.

Based on all of the above, I can speak with confidence about the prospects of my work and its significance not only for geographers, but also for the common population.

Among the natural destructive phenomena inherent in mountains, snow avalanches occupy a special place. In terms of breadth of distribution and frequency of occurrence, they are significantly superior to rockfalls, landslides, landslides and mudflows.

1. General concept of avalanches

Avalanches are one of the most widespread and dangerous natural phenomena in mountainous countries. Many avalanches in the Alps, which occur systematically in the same places, received their own names. Mentions of avalanches are found in the writings of ancient writers who lived more than 2000 years ago. The ancient Greek historian Polybius (201-120 BC) writes about losses from avalanches when Hannibal's troops crossed the Alps (218 BC). The ancient Roman geographer Strabo (63 BC - 20 AD) wrote about the avalanche danger that awaits a traveler in the Alps and the Caucasus.

An avalanche is a snowfall that occurs on steep mountain slopes. The masses of snow that have come into motion slide along the surface of the slope or fall down, passing part of the way in free fall. Avalanches are accompanied, depending on the state of the snow, by deafening noise and grinding sounds. Unlike collapses rocks snow falls usually increase significantly during movement due to the capture of new layers of snow lying lower down the slope. The speed of avalanches can reach 80-100 m/s, the volume of deposited snow masses of one avalanche is 2-6 million m3, and the thickness of snowfields is up to 20-50 m.

1.1 Example of avalanche disasters

Avalanche disasters occur as a result of meteorological situations, as well as during avalanches, when rarely operating avalanche apparatuses “come to life.”

In January 1951, the entire Alpine mountain range, about 700 km long and up to 150 km wide, was in the zone of avalanche disasters. Snowfall, accompanied by blizzards, continued in many areas for seven days and ended with a sharp warming. The amount of snow that fell in some places exceeded the annual precipitation norm by 2-3 times and reached 2-3 m. The slopes were overloaded with snow, and massive avalanches began. The entire transport network of the Alps was disrupted - roads and railways were in places destroyed or blocked and temporarily closed. Avalanches occurred in places where many generations of residents had not known them. Hotel buildings and protected forests were destroyed.

Sometimes the destruction of buildings or the destruction of forests is caused by an air wave formed in front of the front of a moving dust avalanche. This is how an observer conveys the picture of the impact of an air wave. “The large barracks, long before the snow core of the avalanche reached it, fell apart like a cardboard house. Beams and boards flew in an arc through the air and fell on the opposite slope, but the snow of the avalanche itself stopped before reaching the bottom of the valley.”

2. The nature of avalanches

The snow cover lying on the mountain slopes is in a state of unstable equilibrium. The adhesion forces inside the snow mass and at the boundary with the earth's surface counteract the force of gravity, which tends to throw the snow to the foot of the slope. The properties of the snow layer itself are constantly changing both due to changes in meteorological conditions and under the influence of processes occurring inside the snow layer. New snowfalls and blizzards increase the weight of snow masses, sharp changes in air temperature change the stress level of layers of solid snow, thaws give rise to intense melting, rain weakens the bonds between ice particles in the snow. Snow settlement and compaction increase the stability of the snow cover on the slope, while the migration of water vapor leads to the formation of loosening horizons.

IN last years Avalanche researchers have zoned areas by type of activity. This is important for understanding the nature of avalanches, as well as for organizing protection against them. In the scheme for zoning the territory of Russia according to the predominant types of avalanche formation, five groups of regions are identified:

1) Arctic regions with blizzard and inflation avalanches;

2) northern regions with avalanches from blizzard and freshly fallen snow;

3) inland continental regions with avalanches of sublimation diaphthoresis;

4) areas of the southern mountain belt with avalanches from freshly fallen snow, snow boards and advective avalanches;

5) Pacific and coastal areas with avalanches from wet, blowing and complexly stratified snow.

Groups of areas are divided into separate areas, which reflect the specifics of avalanche occurrence in a given mountainous country.

3. Causes of avalanches

The moment the avalanche occurs, i.e. the removal of snow masses from a slope means that gravity overcomes the adhesion forces inside or at the lower boundary of the snow cover.

Researchers identify four main causes of avalanches.

The first is the overload of the slope with snow during prolonged snowfalls and blizzards (when there is a rapid increase in snow mass). Mass avalanches are usually caused by this very reason.

The second is a decrease in the strength of snow during recrystallization. Snow, as a porous medium, is a good heat insulator. In temperate climates, the temperature in the ground layer of snow cover usually stays around 0°, while on the surface it fluctuates greatly. With significant negative temperatures on the surface of the snow cover inside the snow column, a temperature gradient arises and the migration of water vapor from the lower (warm) horizons to the upper (cold) horizons begins. The removal of part of the substance from the lower horizons leads to their loosening and the formation of a layer of deep frost, the adhesion forces in which are insignificant. Avalanches that occur mainly for this reason are relatively rare, but large in volume and destructiveness. They are sometimes called delayed-action avalanches, since the moment of their release is not related to weather conditions, as happens with avalanches that form when slopes are overloaded during snowfalls and blizzards.

The third is the temperature reduction of the snow layer. It occurs as a result of sharp fluctuations in air temperature. Snow is plastic at a temperature of about 0° and becomes brittle as the temperature decreases. If the snow cover lying on a slope is compacted, it may be in a stressed state, i.e. have compression and tension zones (it should be noted that the formation reacts to changes in external conditions as a single whole). In this case, due to sudden cooling, cracks appear in the snow. A rupture in a snow layer can cause an avalanche if the shear pressure exceeds the adhesion forces.

The fourth is the weakening of bonds during snow melting. With the appearance of water under the surface of the snow, the bonds between firn crystals or grains and between layers of snow are weakened or destroyed. Depending on the intensity of snow melting and the depth of wetting of the snow layer, different types of avalanches are formed. At radiation melting When snow covers a thin layer, small surface avalanches form on the southern slopes. During thaws (especially with warm wind or rain), wet avalanches of medium power form; in this case, the upper (wet) layer of snow slides over the lower one, which is not affected by water filtration processes. During prolonged thaws and rains, when the entire thickness of the snow is soaked, powerful ground avalanches occur, moving along the ground and capturing a mass of debris.

4. Avalanche classification

Studying the main causes of avalanches helps to approach the problem of dividing avalanches into main types, i.e. to their classification. There are several classifications of avalanches, which are based on different characteristics: type of snow (loose or dense), water content in the snow, nature of movement, sliding surface, morphology of the path. The division of avalanches into main types is given in table. 1.

However, the general classification of avalanches should reflect their most essential features and serve the practical purposes of organizing avalanche protection. These requirements are best met by two approaches to dividing avalanches into main types. The first genetic one is based on taking into account the causes of avalanches mentioned above; its value lies in the possibility of developing a forecast for the onset of avalanche danger. The second approach is based on taking into account the topography of the snow collection basin and the path of the avalanche. This principle of dividing avalanche devices allows one to calculate the volumes and ranges of avalanches, i.e., it is necessary when mapping avalanche-prone areas.

4.1 Genetic classification of avalanches

Genetic classification of avalanches, most fully developed by the Soviet researcher V.N. Akkuratov, includes the following classes and types of avalanches.

I. Class of dry (cold) avalanches. Such avalanches usually consist of dry snow; disappear mainly in winter; The escape routes are not strictly limited - they can descend along a flat slope and partially through the air. They have maximum speed and can form an air wave. The following types of avalanches belong to the dry class:

1. Avalanches from freshly fallen snow. Such avalanches occur due to overloading of slopes during prolonged snowfalls. For avalanches, 0.3-0.5 m of fresh snow is enough. In snowy areas of temperate climates, this type of avalanche is the main one.

2. Avalanches of blizzard snow. The reason for their occurrence is the high growth rate of the gravity component on the slope. This is the most typical type of avalanche for areas with a moderately cold climate and stormy wind conditions.

3. Avalanches associated with recrystallization of snow and the formation of layers of deep frost (the adhesion forces in which are weakened). Usually rare but powerful avalanches.

4. Avalanches of temperature reduction of snow cover. These avalanches occur as a result of a sharp drop in air temperature. Also a rare type of avalanche.

II. Class of wet (warm) avalanches. Such avalanches are formed from wet or wet snow; they disappear mainly in the spring; the escape paths are usually constant; movement is carried out along the lower horizons of snow or on the ground; the speed of movement is lower than that of dry avalanches; the impact is mainly due to the pressure of heavy (water-saturated) snow masses.

1. Avalanches resulting from radiation thaws. These are low-power avalanches of southern (sunny) slopes.

2. Avalanches associated with thaws and spring snowmelt usually consist of wet, less often wet snow. The sliding surface is usually the interface between snow layers, i.e. avalanches belong to the category of reservoir avalanches (Fig. 3 a, b, c).

3. Ground avalanches are formed in the spring from wet snow completely saturated with water, as a result of prolonged thaws and rains or during rapid snow melting during hair dryers. They always go along certain paths, therefore, as a rule, they have names. They transport significant amounts of debris. The inhabitants of the Alps call the roar of these avalanches “avalanche thunder.” The most destructive in the class of wet avalanches.

4.2 Morphological types of avalanches

The morphology of avalanche collection and the movement of avalanches is given great importance in the complex classification of avalanches developed by the Soviet glaciologist Professor G.K. Tushinsky. Taking into account morphology is necessary to study the movement of avalanches and analyze the regime of avalanche activity. IN natural conditions the morphology of avalanche apparatuses is quite diverse; Its change is associated with differences in the volumes of removal and the avalanche regime. Small avalanches form in small erosion cuts on mountain slopes, or in tectonic cracks. Filling of cracks with snow occurs quickly due to snowstorm transport of snow by winds blowing along the valley. Avalanches of this morphological type are quite frequent - they occur several times a year.

Avalanches that form in large avalanche catchments, which are denudation craters or destroyed craters, occur less frequently. However, they are very large and reach catastrophic proportions. It is precisely for avalanches of this morphological type (from dry snow) that a destructive air wave is characteristic. Under similar relief conditions, the most powerful ground avalanches are formed. Taking into account the morphology of the avalanche apparatus allows us to get an idea of ​​the volume of avalanches and the regime of avalanche activity.

We can distinguish three most characteristic categories of relief forms on which significantly different morphological types of avalanches are formed.

4.3.1 Level slopes

On them, snow slides off in a wide front; The boundaries of an avalanche are not clearly defined and can vary greatly from year to year. These are wasps that resemble surface landslides in soils. The volumes and range of wasp removal are, as a rule, small, but they are dangerous due to the disorder of their manifestation and the absence of clearly recognizable traces of avalanches.

4.3.2 Narrow denudation-tectonic and erosional incisions, usually developing on low slopes

The main feature of these forms is the small area of ​​avalanche collection, which means limited volumes of avalanches. In narrow incisions, sometimes ending in small drainage funnels, typical medium-power flume avalanches are formed. They are characterized by constant descent paths and the formation of an alluvial cone, which is clearly expressed in the relief.

4.3.3 Wide denudation logs

Wide denudation ravines ending in the upper zone of the slope with extensive drainage craters, dilapidated or active ravines with modern glaciers. These forms usually occupy the entire slope - from the watershed ridge to the bottom of the valley. The path of an avalanche and its deposition zone change from year to year. Specific avalanches change their descent paths and areas of accumulation due to the fact that the location of the avalanche and the volume of snow masses captured along the way varies from year to year. Avalanches that form under these terrain conditions are the most powerful and destructive.

These are the main genetic and morphological types of avalanches. However, in nature, a clear division of avalanches according to their genesis and morphology often turns out to be difficult. This is explained by the continuity of processes occurring in the snow layer and in the atmosphere, the altitudinal zonation of climate and landscapes in the mountains, and the gradual nature of the transition from one relief form to another. So, for example, an avalanche, which began as a dry avalanche from dense snow near a glacier, involves into movement masses of wet snow lying in an erosion ravine within the Alpine zone. A slight overload of the slope during snowfall or blizzards can cause a powerful avalanche if a horizon of deep frost has formed in the thickness of the snow by this time. Smooth, flat slopes in the mountains are rare; more often they have ledges, ridges, and hollows. In such hollows, small but dangerous avalanches form for winter tourists; they occupy an intermediate position between flat slope avalanches (osovs) and denudation incision avalanches (trough avalanches). Thus, there are many types of avalanches that are complex in genesis or transitional in morphology.

4.4 Relief as a factor in avalanche formation

Relief is one of the main components that determine avalanche danger. The presence and degree of avalanche danger when there is sufficient snow is largely determined by the characteristics of the terrain. The absolute and relative height, steepness and orientation of the slopes, the shape of the transverse profile of the valleys, the width of the bottoms and watersheds affect the shape, size and spatial distribution of avalanche foci, frequency, types, impact force and range of avalanches, i.e. on almost all aspects of avalanche activity.

Avalanche activity is influenced by the absolute height, steepness and orientation of the slopes, the depth and density of the relief, the shapes and sizes of relief elements, and surface roughness. The parameters of the avalanche source determine the destructive power of individual avalanches. The avalanche danger of a mountain area is determined by the morphological and morphometric spectra of avalanche foci and the nature of their location in space. When assessing avalanche danger, it is necessary to distinguish and differentiate between avalanche foci, avalanche basins and avalanche-prone areas.

4.4.1 Avalanche sources

An avalanche source is the smallest structural subdivision of an avalanche-prone area that must be considered as a whole.

Avalanche foci are the “atoms” that make up the whole variety of specific avalanche situations. The first definition of the concept of an avalanche source was made by S.M. Myagkov: “An avalanche source is a section of a slope and its foot within which avalanches arise, move and stop.” The literature used suggests the following formulation: “Avalanche source - area earth's surface, within which the avalanche moves.” In the class of sources of flume avalanches, chutes, funnels, valleys and cirques are distinguished based on the shape of the initiation zone. Origin zones various types can be approximated by the simplest geometric figures: a trench can be described as a part of a cylinder cut off by a plane parallel to its axis; The funnel is part of a cone, the valley is a prism, and the crater is a sphere. These types differ in the pattern of contour lines on topographic maps(Fig. 1).

Fig.1. Schemes of avalanche sources for flume avalanches of different types: b - funnel, c - valley, d - kar

4.4.2 Avalanche pools

Avalanche centers within an avalanche-prone area can be located separately or combined into avalanche basins. An avalanche basin is a collection of avalanche sources that have a common transit or accumulation zone. The difference between an avalanche basin and a complex avalanche source is that in it avalanches do not form a single avalanche flow, but only a single avalanche flow
snowfield in the stopping area.

An avalanche basin consists of avalanche centers connected to each other by overlapping transit or stopping zones. Depending on the complexity of the basin, there are areas in it that simultaneously belong to two or more avalanche centers.

4.4.3 Avalanche-prone areas

Territories within which avalanche centers occur are called avalanche dangerous. Territories located in the same high-altitude landscape belt, with the same type of distribution of avalanche-prone areas and the same depth of relief dissection, are characterized by stable values ​​of avalanche danger indicators. According to the nature of the spatial distribution of avalanche-prone areas, the following territories are distinguished:

with leveled terrain, avalanche-safe;

with a predominant distribution of leveled terrain and a local distribution of small avalanche sources that cannot be reflected on the map scale;

with a predominant distribution of steep avalanche-prone areas.

5. Avalanches and snow cover

Avalanches like a natural phenomenon due to the corresponding geographical situation. But, existing as a phenomenon, they themselves have a certain influence on this situation, in particular, acting as a factor in the development of the nature of the mountains. Let us dwell on the relationships between avalanches and snow cover, snowfields, and glaciers. Avalanches, like snowfields and glaciers, are one of the derivatives of snow cover.

Indeed, for an avalanche to form, first of all, stable snow cover is necessary. The more stable the snow cover, the longer the period of potential avalanche danger.

The second important indicator of snow cover is its depth; when it reaches 30 cm; the formation of an avalanche becomes possible.

The greater the depth of the snow cover and the faster it changes, the more favorable the conditions for the formation of avalanches. Avalanches can be thought of as a form of solid water runoff. Just as heavy rains cause river floods, heavy snowfalls lead to massive avalanches over large areas or to the formation of avalanches of catastrophic proportions.

Originating in places where snow accumulates in the upper belt of mountains, avalanches create similar accumulations in the lower belt at the foot of the slopes and at the bottom of gorges; such accumulations are called avalanche snowfields. Avalanche snowfields lying in erosional depressions, at the ends of avalanche vents, or at the bottom of gorges are a direct indicator of avalanche danger. The structure of the snow in avalanche snowfields (breccia-like or conglomerate-like) makes it possible to determine the type of snow from which the avalanche was formed.

Avalanches play a significant role in feeding glaciers. The share of avalanche feeding in valley glaciers averages 10% (up to 20%) of the total precipitation. On small glaciers (groups of embryonic and cirque glaciers) it increases to 40%, in some cases exceeding the amount of precipitation. Small glaciers are known that lie well below the snow line and are formed by the merger of several avalanche cones; the existence of such glaciers directly depends on avalanche activity. There is also a special type of large valley glaciers, the so-called Turkestan type, which do not have the usual feeding for glaciers in the firn region - it is provided mainly by avalanches.

6. Avalanches and terrain

Avalanches can occur on short and not very steep slopes, starting from a slope of 15°, with a slope length of 50–100 m. However, most avalanches are formed on slopes with a steepness of 25–60°; On steeper slopes the snow hardly lingers. The depth of the relief or the relative height of the mountains affects the length of the avalanche path and its power. In the case of great ruggedness, characteristic of eroded mountains, the area of ​​avalanche collections, and therefore the volumes of avalanche removal, are limited. Under conditions of glacial relief, the volume of avalanches increases significantly.

6.1 Landforms on slopes and valley floors

Systematically falling avalanches form specific forms of relief on the slopes and bottoms of valleys.

In the alluvial deposits of the valley floor, at the foot of the slopes, knockout pits sometimes form, which are usually filled with water. The rocks captured by the avalanche are deposited in the neighboring area, forming avalanche mounds up to 2-3 m high.

Wet avalanches leave parallel ridges of debris on slopes. The most characteristic element of avalanche relief is the alluvial cone, the surface of which is usually composed of rock fragments with the remains of woody vegetation and turf. Rock fragments, as a rule, are unrolled, angular, and some have completely fresh chips. Another feature of avalanche deposits is the unstable position of the debris. It occurs as a result of their melting from the snowfield.

All these features of avalanche relief when assessing the territory serve as a sign of avalanche danger.

Avalanches are one of the complex processes of mountain destruction. They capture the fragmentary material of the avalanche collection, prepared by weathering processes, tear off the soil and vegetation cover in the drainage channels and cover it all on the bottom of the valleys.

The size and composition of the demolished material varies depending on the altitude position of the avalanche apparatus. In the upper zone of the highlands - the zone of eternal snow and ice - avalanches are practically “clean”. Below, in the glacial zone, where the relief and cover deposits are most actively transformed, avalanches capture and carry out the largest amount of rock fragments. In the belt alpine meadows and in the forest belt the relief is more stable; avalanches are “enriched” here mainly with plant remains, pieces of turf, and soil.

Dry and wet avalanches differ significantly in their destructive effects. Dry avalanches falling for the most part on the surface of old snow, much cleaner than wet ones. In the wet class, ground avalanches are especially abundantly saturated with fragmentary material, which are often colored dirty yellow and gray by the soil and torn soil. Differences in the degree of contamination of different types of avalanches are clearly visible from the analysis of samples taken from the Terskey-Alatau ridge; The weight of the material as a percentage of the weight of the avalanche was 0.01 for dry avalanches, 0.05 for wet avalanches, and 0.61 for wet avalanches.

7. Avalanches and vegetation cover

Dense forest provides natural protection against avalanches. It prevents the redistribution of snow by the wind and divides the snow cover into separate areas.

Although the forest resists only local avalanches and cannot protect against large transit avalanches that originate near glaciers, mountain residents have long realized its role. In Switzerland, a law prohibiting logging on mountain slopes has existed since the 14th century. Destruction of forests on mountain slopes always stimulates avalanche activity.

The impact of avalanches on forest vegetation is manifested, first of all, in the formation of so-called combs - strips of deciduous forest among coniferous or mixed ones. Coniferous species do not produce regrowth after damage to the main trunk and are not capable of restoration in areas systematically exposed to avalanches. These areas are usually overgrown with deciduous trees - birch, aspen, alder, poplar. Avalanche sweeps tear the forest belt into separate tracts and make the line of the upper forest boundary uneven.

The outer boundary of the impact of an avalanche or its air wave is marked by characteristic forms of oppression of woody vegetation: tree trunks are inclined or bent, the crown is developed primarily in the direction of the avalanche movement, the bark and tissue of the tree on the side of the avalanche movement are stripped. The combs and alluvial cones of systematically descending avalanches are overgrown with sparse young deciduous forest or shrubs and lush herbs; Moreover, the trunks of the bushes are often stripped, and the crown is developed one-sidedly. The typical shape of the trunks is saber-shaped.

Traces of the impact of avalanches on forest vegetation serve as a good sign for delineating areas exposed to systematic avalanches (very rare catastrophic avalanches destroy even mature protected forests). The age of undeformed deciduous trees makes it possible to determine the years of the last large avalanches.

8. Avalanche protection

The problem of protection against avalanches is especially acute, since they cause enormous damage to the economy of areas subject to the destructive effects of avalanches; people die under them. Avalanches are extremely widespread.

Avalanches pose a threat to human life, destroy or temporarily disable various structures, railways and highways, and destroy forests. The impact of avalanches is associated with the movement of large masses of snow on high speed. The speed of movement of wet avalanches reaches 10-20 m/s, dry avalanches - 80-100 m/s. In addition to the great impact force of a mass of snow falling from a slope, an avalanche sometimes forms an air wave in front of it. air wave occurs before the front of large dry (dust) avalanches, part of the path of which is in free fall; she expands danger zone at a distance of up to 1 km.

Protection against avalanches has been provided, apparently, since the founding of settlements in the mountains. At first, it boiled down to the use of natural protection (rock ledges, etc.) and the preservation of forests on mountain slopes; Later, buildings began to be placed with their end facing the slope, building this end into the slope and strengthening it.

Nowadays, many countries have accumulated significant experience in avalanche protection.

8.1 Complex of anti-avalanche measures

consists of two main categories - preventive and engineering.

Preventive measures come down to warning about avalanche danger and its elimination by artificial dumping. To prevent avalanche danger, maps of avalanche zones and avalanche time forecasts are compiled.

Preventive measures also include warning the population about the onset of avalanche periods.

Artificial avalanches are carried out by mortars or by detonating the avalanche catchment area with explosives. Avalanche collections are also fired for control purposes, to check the stability of the snow on the slope.

Engineering measures are usually used to protect populated areas and capital structures from avalanches. For this purpose, tunnels, galleries, and canopies are built. Typically, these structures are used to cover certain areas on railways and highways passing through the mountains.

For many years, structures have been erected that change the path of an avalanche, reducing the speed and range of the release - avalanche cutters, wedges, guide walls, wallpaper dams, etc.

They partially extinguish the avalanche energy or divert it away from the protected object. Engineering methods such as terracing and building slopes with snow-retaining shields are also often practiced. They prevent snow from sliding out of avalanche catchment areas. It's expensive, but effective method avalanche control. The protection and restoration of forests on mountain slopes is still considered one of the most important measures in avalanche-prone areas. In the Alps, a forest destroyed by an avalanche is immediately restored. Forest planting is usually combined with the construction of slopes with snow-retaining structures.

Conclusion

Snow avalanches significantly complicate economic activity in the mountains of Kazakhstan and Central Asia often being the cause of significant disasters.

Almost all sectors of the national economy associated with the development natural resources mountains, to one degree or another, need information about snow cover and avalanche danger. This information is necessary for the design, construction and operation of engineering structures, recreational development of mountain areas, for accounting and regulation water resources, improving methods of hydrological forecasts, solving environmental problems.

Thus, the identification of spatio-temporal patterns of snow cover in the mountains and territorial and temporal changes in the activity of avalanche formation, as well as the development of methods for calculating the quantitative characteristics of snow cover and avalanche danger are a necessary condition for the successful solution of issues related to the development of mountain areas, and in general represent a problem of national economic importance.

Bibliography

1. Moskalev Yu.D. "Origin and movement of avalanches."

2. Perov V.F. “Naturally destructive processes in the mountains”

3. Nefedeva E.A. "The influence of snow cover on landscape connections."

4. Nefedeva E.A. "The role of snow cover in the differentiation of the landscape sphere."

5. Richter G.D. "The role of snow cover in the physiographic process."

1. Adventive avalanches - occur when snow cover melts due to the influx of moist warm air.

2. Ground avalanches - avalanches whose sliding surface is directly the surface of the slope.

3. Insolation avalanches - occur as a result of heating of the surface layer of snow by the sun's rays.

4. Wet avalanches - avalanches made of wet or wet snow.

5. Direct avalanches - avalanches that occur during or immediately after heavy snowfalls and blizzards.

6. Avalanches from complexly stratified snow - occur under conditions of sudden changes in weather types - low temperatures give way to thaws, which leads to the formation of a complex structure of snow cover.

7. Avalanches of sublimation diaphthoresis - arise as a result of the weakening of bonds within the snow layer, due to the migration of water vapor and the formation of a loosening horizon.

8. Avalanche sweep 3 strip of deciduous forest among coniferous forests, formed by systematic avalanches.

9. Avalanche snowfields - accumulation of snow at the foot of the slopes, formed by avalanches and existing during part or all of the warm season.

*** Avalanches of rare recurrence that extend far beyond the mineral cone of a given avalanche source, as well as avalanches that cause significant material damage and human casualties, are considered catastrophic.

A complete inventory of avalanche disasters has not yet been created, but chronicles, manuscripts, books and human memory have preserved for us descriptions of many cases of death due to avalanches.

The longest record of avalanche disasters is in the Alps. The first authentic medieval document reported the death in an avalanche of part of the retinue of Bishop Rudolf, who on Christmas Day 1129 was heading to Rome through the Great St. Bernard Pass. Since the 15th century, chronicles increasingly mention avalanche disasters in the Alps.

The historian Titus Livius (59 BC - 17 AD) mentions avalanches in his descriptions of Alexander the Great’s campaigns in the mountains of Central Asia and through the Hindu Kush to India. The first mention of avalanches in the Himalayas in Indian literature is found in the poem “Megahdut” (“Cloud Messenger”), written by Kalidasa (c. 5th century): “The Himalayas, which have enormous advantages, including precious minerals, have one drawback - avalanches . But this flaw is invisible among other values, just as spots on the Moon do not diminish the light that emanates from it."

In his “History,” the Roman historian Polybius (2nd century BC) wrote about the Carthaginian campaign through the Alps: “But when Hannibal’s troops reached one bottleneck, where neither elephants nor pack animals could pass, an avalanche fell, and the spirit of the army fell." Hannibal had no idea what a terrible and invincible enemy his army would meet in the Alps. Huge avalanches buried here at once as many of his warriors as he did not lose in any of the bloodiest battles. Hannibal almost lost the war to the Romans because of this!

In Europe, avalanche disasters are by no means exclusive to the Alps. For a long time now, a record of victims has been kept in Iceland. Even in the sagas, it was reported that 5 people died in 1118, and on December 24, 1613, 50 inhabitants died on the island at once. Since 1800, the number of avalanche victims has reached almost 500 people, 470 buildings have been destroyed, and 3,500 heads of livestock have been destroyed.

IN Norway in 1679, up to 500 people died in avalanches, and in 1755 - about 200. A major avalanche disaster occurred in 1886, when the white death, as avalanches in the Alps are called, killed 161 people. In one of the last disasters, in the winter of 1955/56, 30 people died. Avalanche disasters that occurred in the last century are repeatedly mentioned in monastic manuscripts Bulgaria.

And yet the Alps remain the main place of rampant white death.

1799
I had to deal with avalanches in the Alps and Russians. In the fall of 1799, an army led by A.V. Suvorov marched from Italy to Switzerland. At the avalanche-prone St. Gotthard Pass and in the narrow mountain valley on the way to the Devil's Bridge, the army suffered minor losses from avalanches. Not far from the Devil's Bridge, in a niche carved into a steep mountain slope, there is a monument to Suvorov soldiers. In winter, it is annually blocked by avalanches.

In 1885, one of the largest avalanches occurred in the Italian Alps - with a volume of 3.5 million cubic meters.

In our century, the greatest human losses from avalanches occurred in the Tyrolean Alps, during the First World War of 1915-1918, on the Austro-Italian front. According to approximate data, from 40,000 to 80,000 people died from them. Set in motion by explosions, the roar of technology and other sounds of war, avalanches descended one after another along the slopes of the Alps. Villages like Marmolada were buried under them, where on one day about 235 people were buried in their homes. December 16, 1916 remains in memory as “Black Thursday.” On this day, more than 6 thousand soldiers were buried in avalanches. In total, during the difficult winter of 1916/17, more than 10 thousand people became victims of avalanches.

Ernest Hemingway, who was an excellent skier and first world war was on the Austro-Italian front in the Alps, he wrote about avalanches: “Winter avalanches have no nicknames. They are sudden, terrible and deadly."

Subsequently, in the Alps more than once - in 1917, 1919, 1923, 1925, 1931, 1935, 1945, 1951, 1954, 1968, 1975 - there were winters with heavy snowfalls, blizzards and avalanches, but not a single winter claimed so many victims, How long is "Black Thursday" December 16, 1916?

1951
More than 50 years ago, the Alps in Switzerland and Austria were damaged by a terrible avalanche. The mass of snow came down in a matter of seconds, literally sweeping away everything possible in its path. This avalanche was included in the list of the 5 worst avalanches in the world. The winter of that year is now known as the "winter of terror."

245 people died and over 45,000 were cut off from the outside world on January 20, 1951, as a result of a series of avalanches in the Swiss, Austrian and Italian Alps caused by the combined effects of hurricane winds and snowfalls, when wet snow lay on top of loose snow.

It was the worst natural disaster since 1915, when snow avalanches killed hundreds of Italian and Austrian soldiers. Now 245 people were killed, many villages were destroyed, and 45,000 people were cut off from the outside world for several weeks.

Even luxury resorts such as Davos, Zermatt, Arosa and Saint-Mortz could not avoid the tragedy. But perhaps the heaviest blow fell on the Swiss village of Vals, located at an altitude of 1200 meters above sea level in the most picturesque corner Swiss Alps. The village disappeared almost completely, 19 residents died.

The Gotthard railway line, which links Switzerland with central Europe, was out of service for a week after being blocked by incredible blocks of snow, rocks and ice. Communication lines were cut, contacts with the outside world were disrupted.

1954
The largest funeral in history (as a percentage of the local population) took place after two avalanches thundered into the small Austrian village of Blons, near the Alberga Pass, on January 11, 1954. At the same time, 111 people out of 376 village residents were buried, 29 out of 90 houses were destroyed, 300 out of approximately 600 miners who were in the Liduk mine were buried alive.

A record number of victims was caused by a double avalanche. The first descended at 9.36, the second at 19.00 on January 11.

Such catastrophic losses occurred despite the constant readiness of villagers to face avalanches. Indeed, every December the village meeting decided to move the crucifix, which stood close to the gorge. The crucifix was moved so that it would not be carried away into the gorge during bad weather or by an avalanche.

One more detail. When residents crossed the bridge over the gorge, they involuntarily stretched out into a long and sparse chain and stopped talking. They believed that if their voices or any other vibrations caused an avalanche, then the large distance between pedestrians could save their lives.

But there was no salvation. Of those trapped under the snow, 33 got out on their own, 31 were dug up by rescuers alive, and 47 were taken out dead. Eight survivors of the disaster died later. A man who had been under the snow for 17 hours was pulled out by rescuers, but died of shock when he learned that he had been under the avalanche for such a long time. One woman suffered severe burns while under the snow. She was baking bread when an avalanche hit the house. The snow flow carried the woman, and the coals that fell from the oven burned her body. The two residents were never found. Among the survivors were people who spent up to 62 hours in snow captivity.

1968
On the morning of January 27, 1968, in a place known back in the Middle Ages for its exceptional avalanche danger In the Montafon area in Switzerland, an avalanche carrying a spruce trunk with a diameter of 50 centimeters hit the wall of the second floor of the building. The outer wall, made of brick, was 43 centimeters thick. Having broken through it, the barrel crossed the children's room, rammed a 20-centimeter thick partition and, flying past the parents' bedroom, pierced the second outer wall. A log got stuck in it, sticking out two meters. It was more like the actions of an armor-piercing shell than being hit by a log.

In Switzerland, avalanches annually destroy up to twenty residential buildings and about a hundred farmsteads and mountain huts.

1970
One of the worst disasters occurred in French Alps just recently: in 1970, an avalanche that hit a hotel in Val d'Isere killed about two hundred tourists, and another demolished a children's sanatorium near Saint-Gervais, burying 80 people - children and staff.

1999
February 23, 1999 at cozy village In the Alps, an avalanche came down from the mountains, which will forever remain in history as one of the worst disasters in this region. In a few minutes, more than 100 thousand tons of snow moved towards a tiny settlement. At breakneck speed, the snow demolished 5 houses in its path, damaging 26. 31 people died in less than three minutes. The disaster attracted international attention.

A few days before the disaster, there was heavy snowfall of up to 30 cm per day. After which strong northwest winds blew up to 120 km/h in the mountains. The reason for the accumulation and fixation of a large mass of snow was a change in temperature from −20 degrees to +4, and then a cold snap that fixed the snow. On February 23, a mass of snow of 170 thousand tons fell on the town (normally it should not exceed 70 thousand tons). Where the avalanche broke off the mountain, it was 4.5 meters thick at its widest point. It was a so-called powder avalanche, which is 20 times denser than air. Upper layer snow reaches speeds of up to 417 km/h. During its descent, the avalanche, like a snowball, captured the layer of snow over which it passed (the so-called “entrainment”).

USA
According to statistics, about one hundred thousand avalanches occur in the United States every year. For some regions of this country, avalanches are commonplace.

1874
In the United States, avalanche disasters became more frequent during the “gold rush,” when masses of people poured into the Rocky Mountains in search of gold and silver. In 1874, near the town of Alta, a prospector’s camp was buried in which 60 people died. The list of camps and villages destroyed by avalanches is sufficient great, but the largest avalanche disaster in the United States was associated with the construction of the transcontinental railroad through the Rocky Mountains.

1910
The most destructive avalanche in the history of the United States occurred in the Cascade Mountains of Washington state in March 1910, following heavy snowfalls. Here, at the small Wellington stop, which was located just between two snow protection galleries, there had never been avalanches before, since the steep mountain slope above the stop was covered with dense forest. But in the summer preceding this terrible winter, a forest fire destroyed the forest - a natural defense against avalanches. Nobody paid attention to this.

At the end of February, heavy snow kept three passenger trains at Wellington station for 9 days. On February 28, the snowfall was replaced by a warm wind and rain. March 1 At 1.20 a gigantic snow bank 8 meters high, 500 meters wide and 600 meters long fell from the bare mountainside and rushed towards railway station. An avalanche struck trains and a water tower. Passenger and mail trains were carried away into a deep gorge, a train with a snowplow and seven locomotives turned into a pile of iron. Miraculously, a small station hotel survived, the inhabitants of which, grabbing shovels, with heroic efforts were able to save 22 people from the ill-fated train from under the snow and debris; the remaining passengers, of whom there were 100, died.

In the same year, but much further north, in Canada, avalanches killed 62 workers who arrived at Roger Pass in British Columbia to rescue a Trans-Canada Railway train from snow captivity, blocked by skids and avalanches.

And in our time, roads, mountain villages and mining towns in the Rocky Mountains of the USA and Canada have more than once become victims of avalanches: Twin Lakes in Colorado on January 21, 1962, Grand Duke Mine in British Columbia on February 18, 1965, the village of Terrace in the same British Columbia on January 22, 1974 and many others.

One of the most avalanche-prone towns is the town of Juno in Alaska, which is located near seven avalanche-prone slopes. Sometimes it seems that this is a fairy-tale country where snowy silence reigns, but in fact it is only the calm before a terrible storm.

The worst snow melting still lives in memory local residents. The disaster happened in 1962, when a giant slab of snow demolished 35 houses.

CANADA

1965
There is an amazingly beautiful place in British Columbia - the Cordillera. The largest mountain system on the globe, with beautiful plateaus and hundreds of deep valleys, has killed many people.

The most terrible event happened in 1965. A huge avalanche occurred over the Granduc mine, killing 26 people and injuring 22. Another 40 people could not be found in the snow.

ASIA
In most Asian countries, records of avalanche disasters are not kept. Only from time to time newspapers report about victims of avalanches on the mountain roads of Turkey and Iran, Afghanistan and Nepal, about demolished towns and villages. Most of the climbers who died while climbing Everest were torn from its slopes and buried by avalanches.

JAPAN
Avalanche disasters are very common in Japan, where in 1938 in Shiaidani an avalanche tore off the second floor of a house and smashed it into the rocks along with the 73 workers in it. In the low mountains of Japan, avalanche disasters occur almost every year.

SOUTH AMERICA
There are dwarf avalanches and giant avalanches - in terms of volume and travel distance. The biggest disasters of all time are associated with one of the picturesque areas of Peru in South America. Above the valley of the Saita River in the Andes chain rises Mount Huascaran, crowned with a cap of glaciers.

1962
At 6.13 am on January 10, 1962, a telephone operator in one of the remote villages suddenly saw something falling from the top extinct volcano Huascaran white swirling cloud. About 2 million cubic meters of snow and ice fell from the glacier covering the top of the mountain. This mass fell from an almost vertical cliff a kilometer high onto a glacier lying in the bowl of a deep circus. Having torn off the snow from it and capturing fragments of stones, sand and pebbles along the way, the avalanche rushed towards the village of Ranrairka. Emitting a deafening roar, 13 million cubic meters of rock and ice weighing 20 million tons traveled the 18-kilometer canyon in seven minutes, burying the village of Ranrahirca along the way. Only 98 of the 2,456 inhabitants survived. Below, the avalanche destroyed 5 more small villages with all their inhabitants. In total, more than 4,000 people and 10,000 animals died. Million dollars worth of food was destroyed.

1970
On May 31, 1970, Mount Huascaran again reminded itself. This time, after the earthquake, huge masses of snow and ice again fell onto the underlying glacier, broke off part of the ice from it, and this mass rushed along the old bed to the valley of the Saita River, drawing into movement loose rocks and the water of a small lake that lay on the way.

Already 80 million cubic meters of snow, ice, boulders, sand and clay have fallen on the town of Jungau, located on the Huascaran spur. The front shaft of the collapse rose almost 90 meters above the valley level - the height of a thirty-story building. If the 1962 avalanche stopped in front of a small hill, this time the hill could not protect the city of Jungau: none of the 25,000 inhabitants of the village survived. The rebuilt village of Ranrairka was again wiped off the face of the earth. The avalanche reached the bed of the Saita River and, turning sharply, passed down the river another hundreds of meters.

Starting out like snow avalanche, it then became a snow and ice avalanche, and ended its path as a mudflow. This allows both avalanche workers and mudflow rescuers to consider it “theirs.” The Huascaran avalanche traveled 16.5 kilometers - this is a world record for the ejection distance.

RUSSIA (EMPIRE AND FEDERATION)

CAUCASUS
Stranabon wrote about avalanches on the territory of our country 2000 years ago in his “Geography”: “... and in the Caucasus, avalanches lie in wait for travelers and claim many victims.” The largest disaster of antiquity on the territory of our country was literally “excavated” by the famous avalanche specialist G.K. Tushinsky.

In the upper reaches of the Bolshoy Zelenchuk River in the Arkhyz tract at the foot of the Abishira-Akhuvba ridge, he discovered a large Alan village, which was destroyed by avalanches in the 13th century and therefore abandoned by the population. G.K. Tushinsky proved that in the 13th-14th centuries, as a result of increasingly frequent harsh and snowy winters, avalanches in the Caucasus destroyed many high-mountain villages and roads; settlements since then they have been located much lower on the slopes. According to Tushinsky, it was the intensification of avalanche activity that was one of the reasons for the fall of the Alan state.

The arrival of the Russians in the Caucasus could not help but confront them with white death. There is information about the death of a Russian military detachment under an avalanche in 1817 while trying to penetrate Elbrus.

The history of avalanche disasters on the Georgian Military Road is especially rich in oral and written traditions. Many avalanches have received their own names. Here, for example, is the avalanche “Majorsha”: the majorsha was driving along the road in a carriage, and her maid, who did not please her in some way, forced her to walk. The girl passed easily dangerous place, and the thundering, heavy carriage caused an avalanche, which buried him and the major’s wife.

The “Persian” avalanche was named in memory of the delegation that died under it, which traveled to St. Petersburg to apologize for the murder of Alexander Sergeevich Griboyedov, the Russian ambassador to Persia.

Already in our time, in 1932, a huge avalanche wiped out the village of Arashend in South Ossetia.

In the winter of 1942/43, Soviet soldiers defending the main passes of the Caucasus from the Nazis had to come face to face with avalanches. The soldiers were trained for combat in the mountains by famous climbers. This made it possible to avoid such losses from avalanches, which were noted on the Austrian-Italian front during the First World War. But still, individual groups of soldiers did not escape death. Fascist mountain rangers also died. A participant in the battles in the passes of the Caucasus, A. Gusev, now a professor, personally observed how a platoon of rangers crossing an avalanche-prone slope was completely swept away by an avalanche. Our climbers, who knew the mountains well, artificially caused avalanches, thus destroying enemy soldiers.

KHIBINS
One of the most famous avalanche disasters in our country occurred not in the Caucasus, but in the low, but very snowy Khibiny Mountains in Kola Peninsula. Here, back in 1912, from the words of local Sami residents, a legend was written about how foreigners attacked them and they were forced to hide on the top of the mountain, where they climbed up a safe slope. The enemies began to climb the avalanche slope, onto which the wise old Sami woman threw dry sedge stems to create the impression that it was here that the Sami climbed the mountain. The snow fell and the enemies died in an avalanche.

In the early 30s, the development of rich apatite deposits began in the Khibiny Mountains. Mines, roads, communication lines and a residential village were built here. The builders were still little familiar with the nature of avalanches in these places. The most famous avalanche disaster in Russia occurred on December 5, 1935 in the Khibiny Mountains.

After a strong blizzard and snowfall, two avalanches descended one after another on the village of Kukisvumchorr, which destroyed several one- and two-story houses and covered railway, demolished the communication lines and the high-voltage line, threw the locomotive off the tracks and dragged it 150 meters down the slope. 88 people died under the rubble of buildings. This event became the impetus for the start of systematic scientific research into avalanches in our country.

The energetic measures taken made it possible to avoid similar disasters at the Apatit plant in the future. Only the foundations of demolished houses that are still preserved in the village of Kukisvumchorr remind of the past tragedy. In the Khibiny, avalanches with a volume of about 500 thousand cubic meters were observed with a release range of about 2 kilometers.

The champion in ejection range in our country was an avalanche with a volume of about 1 million cubic meters, which traveled 6.5 kilometers in the valley of the Kzylcha River in the Western Tien Shan.

SAKHALIN
The largest avalanche in the mountains of Sakhalin Island came down from Chekhov Peak in the winter of 1969/70. Its volume was 200 thousand cubic meters, and its path was at least 1.6 kilometers.

TIEN SHAN and PAMIR
One thousand three hundred years ago, the Buddhist monk Xuan Tsang, while crossing the Tien Shan and Pamirs, lost many of his companions to avalanches. In his book “Notes on the Countries of the West,” completed in 648, he called avalanches “snow dragons.” And now “snow dragons” prowl the Tien Shan and Pamir mountains.

There is a description of an avalanche disaster in January 1956 in the Western Tien Shan, on the northern slopes of the Kurama Range. The avalanche shot out like a cannon from a relatively small depression on a bare slope. It destroyed the middle part of a long barracks built at the foot of the slope. The avalanche, only 30 meters wide and with a volume of about 1000 cubic meters, carefully cut out the middle part of the structure, without even moving the asbestos-cement tiles on the roof at the cut points. A similar case occurred on Sakhalin Island. Here, a modern sanatorium was on the path of the avalanche. Fortunately, no one was hurt purely by accident.

In both cases, the civil engineers cannot be blamed. It was the mid-50s; There were only a few professional avalanche climbers actively working in our country. In textbooks for construction universities, several lines were devoted to avalanches. general information, which the student might not remember a few days after the exam. Did not have sufficient experience construction in mountain conditions. Soviet avalanche experts in those years could not even say exactly in which mountain regions of our country avalanches regularly fall.

***This article is a compilation of information found on the Internet and does not pretend to be a scientific work.