Landslide formation, how to avoid landslides, external signs of a landslide slope. Consequences of landslides What are landslides and landslides

The soil mass, especially its near-surface layers on the slope, experiences deformation even without the active development of the landslide process. This is due to freezing and thawing of the upper horizons of the massif in the winter-spring period, watering and drying them out in warm weather. summer time, with a force effect on the soil skeleton of filtering groundwater, with a change in the stress state in the massif due to an increase - decrease in the weight of soils during their wetting - drying, the manifestation of the weighing effect of groundwater, the influence of local movements, the manifestation of individual cracks and man-made changes in the relief.

All of these factors can cause deformation of the surface cover in the direction of slope decline. This deformation can occur in the form of slow creep of soils (the phenomenon “ secular creep") with possible activations under abnormal influences of factors.

Occurrence of a landslide caused by an imbalance of the massif and deformation of the soil massif at a qualitatively different level. The landslide process is understood as an imbalance of the soil mass, its deformation under the influence of unbalanced forces, the separation of part of the mass by a tensile crack (potential or actual “failure wall”) and the movement of the formed landslide body along the sliding surface without loss of contact with the non-displaceable bed.

According to the nature of the imbalance of the soil massif, the characteristics of deformation, which are largely determined by the prevailing force influence and deformation mechanism, landslides can be divided into four main types.

The first type is block relatively deep compression landslides(according to other classifications - landslides of extrusion, crushing, subsidence, bulging). The imbalance of the massif and deformation during the formation of a landslide occur according to the compression pattern. Under compressive vertical pressure from the weight of the overlying layers, the horizon is deformed (crushed), the structural strength of the soils of which is less than the specified domestic pressure. Due to the deformation of the soils of the crushed horizon towards the slope, subsidence and deflection of the overlying massif occurs with the formation in the bending zone, first of a concentration of tensile stresses, and then of a pin crack (a lowered tensile crack). Further, along this crack, the landslide block separates and settles along a steep curved sliding surface. The sliding surface flattens out towards the slope and can be close to horizontal.

The most common are block compression landslides, the sliding surfaces of which are formed in clay soils (Fig. 1. a, b). Landslides of this type affect the banks of rivers, seas, lakes, and form on the slopes of excavations, embankments, and on the sides of quarries. According to research results, deep block landslides also developed on the right bank of the Kama, in the area where the river crosses the Uzhgorod gas pipeline corridor.

Rice. 1. Schemes of landslide deformations based on the compression mechanism. a, b – compression landslide in clayey soils; c – subsidence and spreading of blocks of semi-rocky and rocky rocks; d – uplift of the valley bottom; e – gravitational folds: deep creep with S-shaped bending of layers; e – gravitational deformations of ridges.

Landslides of this type in semi-rocky and rocky soils are less known. They are found in mountainous and foothill regions. They are characterized by a slow development of deformation in the stage of preparation for displacement, lasting up to several hundred years (Fig. 1c-f).

IN The second type is shear landslides(according to other classifications - sliding landslides, shearing landslides, sliding landslides). In the pre-limit state, concentration of tangential shear stresses occurs in the corresponding zones of the soil mass: preparation of soil shears on steep sections of the slope during the formation of the angle of repose; creep of weathered near-surface slope deposits (cover landslides) with movement along an endless slope pattern; shift along a weakening zone predetermined by the geological structure (along contact with the roof of stronger rocks, along the bedding plane). Deformation of a slope (slope) occurs in the form of a progressive shear with a drop in resistance as deformation occurs, a decrease in strength from the peak value to the residual value, and the gradual formation of a sliding surface (plane).

Rice. 2. Schemes of landslide deformations according to the shear mechanism. a – shear-cut; b – shift along bedding; c – shear-sliding of cover masses; d – shift (slide) of the soil (soil-vegetation) layer; d – bending of the heads of steeply dipping layers.

On steep ledges, the shift (sliding) of the sliding part of the massif occurs, as a rule, along a curved sliding surface extending to the bottom of the ledge or above it (Fig. 2a). Thus, a profile of an equally strong or equally stable slope is formed with displacement (often collapse) of softened soils. The sliding surface can be confined to inclined geological boundaries between layers. In this case, significant units of rocks can shift (Fig. 2b). The shear pattern along broken flat sliding surfaces is characteristic of the sliding of deluvial-eluvial slope accumulations along the inclined roof of bedrock (Fig. 2c). A frequent form of landslide manifestations is a shift (slide) of the soil and vegetation cover (Fig. 2d), revealed by a series of relatively short landslide cracks. Slow creep of the surface layer in the form of shear can be observed on relatively stable slopes with steeply dipping layers of strong rocks (Fig. 2e).

The third type is liquefaction landslides.(according to other classifications - flow landslides, drifts, slides, plastic, visco-plastic). Disturbance of the equilibrium of slope massifs in the form of liquefaction occurs due to the predominant force action of underground (ground) waters. The main mechanism of liquefaction, considered in soil mechanics as filtration deformation of the soil, is an increase in pore pressure (water pressure in the pores of the soil) and, as a consequence, a decrease in effective stresses. In a water-saturated soil mass, pore water, to one degree or another, can exert hydrostatic weighing and filtration pressure of different directions on the mineral skeleton of the soil, caused by filtration volumetric forces. The intensity and direction of these forces depend on external influences: static and dynamic loads on the slope, the speed of filtration flows and level fluctuations groundwater, level regime in reservoirs and surface watercourses, intensity atmospheric precipitation etc.

This mechanism of landslide formation is especially characteristic of dispersed soils with a weak structural skeleton and low filtration capacity. These include modern silts, water-saturated young clays and loams, quicksand, soils, peats, as well as clayey soils of various ages that have lost strength as a result of decompaction, weathering and hydration.

The action of the liquefaction mechanism is associated with the sliding of slopes of poorly cohesive soil during watering due to a change in the angle of repose from  =  to  = /2 (where  is the angle of internal friction of non-watered soil). At the point where groundwater emerges (discharges) to the surface of the slope, a landslide circus with a narrowed neck often forms (Fig. 3a). Liquefied soil masses (the product of the collapse of the stall wall and sides) in the form of a visco-plastic flow move from the neck to the slope with the formation of an alluvial cone at the foot. Resulting heavy downpours, abundant snow melting, an increase in the groundwater level and, accordingly, ascending filtration forces can reduce internal friction in the soil to zero, and decompaction under low loads (surface layers) can lead to a loss of cohesion between mineral particles. In this case, liquefaction of sandy-clayey soil can occur even with small surface slopes (1:10 or less) (Fig. 3b). Often there are violations of the local stability of a slope section in places of excessive soil moisture and deformation in the form of sloughs (Fig. 3c).

Rice. 3. Schemes of landslide deformations based on the liquefaction mechanism. a – landslide circus with a narrow neck (groundwater unloading); b – landslide-flow; c – sludge.

Fourth type – tensile landslides with the separation of part of the rock mass (other names: landslides, collapse, complex landslide). Disequilibrium and predominant destruction occur under the influence of normal tensile stresses with separation of the mass along the fracture surface. Monolithic rocks can withstand significant tensile stresses (up to 30 MPa), as evidenced by the high steep slopes of the sides of many mountain valleys. When tensile stresses exceed the soil strength limit, unbalanced rock blocks separate from the rest of the massif, slide, and collapse (Fig. 4a). The separation of the massif can occur along discontinuous seismotectonic cracks with subsequent movement along the shear surface (Fig. 4b) or subsidence of the separated massif with deformation of the underlying stratum of clayey rocks (Fig. 4c). The presence of a steep prepared shear surface also promotes the formation of rupture cracks in the zone of tensile stress concentration (Fig. 4d).

Of all the types considered, deep block landslides pose the greatest danger to main gas pipelines in the conditions of the Russian Platform (see Fig. 1). Combating deep block landslides is very difficult, especially when the landslide process gains momentum and becomes catastrophic, causing dangerous deformation and destructive accidents of gas pipelines.

In this section, 9 lines of the main gas pipeline are located in an old landslide circus formed by deep block landslides. Monitoring of the landslide process should be aimed at identifying deep movements and monitoring the state of a deep landslide.

Rice. 4. Schemes of landslide deformations according to the tensile mechanism with separation of part of the rock mass. a – separation and sliding with the collapse of rock blocks; b – rupture along a tectonic crack and sliding along the formed surface in a mountain massif; c – separation of the massif along a fault and subsidence of the rock block with deformation of the clayey strata; d – detachment at the place of concentration of tensile stresses and shear along a steep bedding surface.

Employees of the American aerospace agency NASA have made the DRIP-SLIP software package freely available, which makes it possible to monitor landslides around the world. The system scans satellite images and determines where a disaster could occur in the near future. /website/

The system is a collection of location maps updated every 24, 48 or 72 hours. This allows you to monitor the situation in real time. The capabilities of the complex are demonstrated using the example of a map of landslides that were recorded from 2007 to 2013.

“We are interested in quickly and accurately identifying unreported landslides to better understand the nature of their occurrence. This information will make it possible to clarify maps that depict the regions most prone to landslides and take measures to prevent them,” NASA experts noted.

Landslides often go unnoticed and unreported, resulting in a large number of casualties. “We know that a large number of landslides occur during this period of time in Nepal. Documenting them is very important to better understand why these events occur and what impact they have,” experts say.

Risk area - Nepal

Scientists pay special attention to Nepal, since landslides in this country are very current problem. Landslides occur here during the monsoon season and lead to the death of dozens and sometimes hundreds of people. One of the most destructive landslides occurred in this country last year after a strong earthquake.

Due to the vibrations of the earth's crust, mountain slopes collapsed and avalanches of mud rushed from the slopes of mountains and hills. The largest landslide occurred in the Miagdi region, about 140 kilometers from Nepal's capital Kathmandu. Landslides also occurred in other regions. People who survived devastating earthquake, died under layers of sliding earth.

Landslide record holder

Landslides occur quite frequently around the world. Largest landslide in modern history occurred on February 18, 1911 in the Pamirs in Tajikistan. After a strong earthquake, 2.2 billion cubic meters of loose material slid from the Muzkol ridge from a height of 5 thousand meters. The force of the impact of the collapsed mass caused a seismic wave that circled the entire globe several times.

The landslide covered the village of Usoy with all its residents, property and livestock, resulting in the death of 54 people. In addition, the descending mass blocked the Mugrab River, which is why Lake Sarez, 4–5 kilometers wide, was formed. Over time, the lake grew, flooding the villages of Sarez, Nisor-Dasht and Irkht. Currently, the lake still exists, its length and width are already 75 kilometers.

The lake still poses a danger to nearby settlements. This area is located in a seismically active zone, and weak tremors can trigger a breakthrough of Lake Sarez. In the event of a tragedy, a huge mass of water will flow like a mudflow almost to the Aral Sea. About 6 million people live in the potentially dangerous zone.

The most destructive landslide

The most tragic in terms of the number of victims was a landslide that occurred in the Chinese province of Gansu in 1920. Most of the territory of this province is occupied by a loess plateau, which is a homogeneous soil mixed with lime, clay and sand. The soil here is fertile, so the area was densely populated. After the earthquake, the cohesion of the loess was disrupted, and the earthen mass rolled down in entire hills. She destroyed everything within a radius of 50 thousand square kilometers.

The situation was aggravated by the fact that everything happened on a winter night, when all the people were in their houses. “The shocks followed one after another with an interval of several seconds and merged with the deafening roar of collapsing houses, the screams of people and the roar of animals that came from under the rubble of buildings,” recalled the miraculously surviving missionary.

One of the houses, moved by a mass of rocks, was moved almost a kilometer. However, the house remained undamaged. The man and child who were there were also not injured. Because of the darkness and noise, they did not even understand what had happened. Along with the house, the section of the road also moved. Now this place is called “Death Valley”. More than 200 thousand people are buried there.

Landslides in Russia

Scientists consider landslides to be the most dangerous natural disaster. The danger is that they can occur absolutely anywhere where there is a slope. Landslides are not associated with geographical location and can get off in any country, including Russia. Most often with this natural phenomenon residents of the North Caucasus, Volga region, Primorye have to deal with, Eastern Siberia and the Urals.

For example, in 2006, heavy snowfalls and continuous rains in the mountains caused severe landslides in Chechnya. The upper layers of rocks up to two meters thick rolled down the slopes, burying residential buildings in the villages of Shuani, Benoi, Zandak and others. In the village of Shuani alone, a landslide destroyed about 60 houses in one day. Residents left their homes, taking with them only documents.

The Russian Black Sea coast is also a risk zone. Mountain slopes built up with many infrastructure facilities create favorable conditions for landslides. The danger increases especially in autumn-winter period when the mountain slopes are washed away by rain. Active human activity, including construction and landscape impacts, are also additional risk factors.

Slowly and gradually or abruptly sliding along the inclined plane of separation, while often maintaining its coherence and solidity and not tipping over. Landslides occur on the slopes of valleys or river banks, in the mountains, on the shores of the seas, and the largest ones occur at the bottom of the seas. Most often, landslides occur on slopes composed of alternating water-resistant and aquiferous rocks. The displacement of large masses of earth or rock along a slope or cliff is caused in most cases by wetting the soil with rainwater so that the soil mass becomes heavier and more mobile. It can also be caused by earthquakes or sea erosion. The frictional forces that provide adhesion to soils or rocks on slopes are less than gravity, and the entire mass of rock begins to move.

Consequences of a landslide

Underwater landslides

Underwater landslides remained unexplored for a long time. Only their consequences - the tsunami - make themselves felt. They are formed when large masses of sedimentary rocks are removed at the edge of the shelf. Underwater landslides are much larger than above-water ones. For example, the volume of the Sturegga landslide on the slope of Norway has an area of the whole country and is about 3900 km, and the range of movement of material in it reaches 500 km. The volume of just one such landslide is more than 300 times greater than the annual supply of sedimentary material to the World Ocean by all the rivers of the Earth. In Scotland, traces of the tsunami that followed the landslide were discovered at a distance of 80 km from the coast.

Causes

The reason for the formation of landslides is an imbalance between the shearing force of gravity and the holding forces. It is called:

• increasing slope steepness as a result of erosion by water;
• weakening of the strength of rocks due to weathering or waterlogging by precipitation and groundwater;
• exposure to seismic shocks;
• construction and economic activities.

Characteristic

As a result of its activity, a landslide creates a “landslide body”, which in plan basically has the shape of a semicircle, forming a depression in the middle. As noted above, landslides occur on slopes composed of alternating water-resistant (clayey) and aquiferous rocks. Displacement of rock blocks with a volume of tens of cubic meters or more on steep slopes as a result of wetting of the separation surfaces with groundwater.

Such natural disasters harm agricultural land, enterprises, settlements. To combat landslides, bank protection structures and planting of vegetation are used.

Classification

According to the power of the landslide process, that is, the involvement of rock masses in the movement, landslides are divided into small - up to 10 thousand cubic meters, medium - 10-100 thousand cubic meters, large - 100-1000 thousand cubic meters, very large - over 1000 thousand cubic meters.

The surface along which the landslide breaks off and moves down is called the sliding or displacement surface; based on its steepness, they are distinguished:

b) flat (5°-15°);

c) steep (15°-45°).

Based on the depth of the sliding surface, landslides are distinguished: surface - no deeper than 1 m - mudslides, alloys; small - up to 5 m; deep - up to 20 m; very deep - deeper than 20 m.

Classification of landslides (according to Savarensky) according to the position of the displacement surface and the composition of the landslide body:

a) asequential (in some sources they are indicated as sequential) - occur in homogeneous non-layered rock strata; the position of the curved sliding surface depends on friction and soil displacement;

b) consequential (sliding) - occur with heterogeneous slope composition; displacement occurs along the interface between layers or crack;

c) incessant - also arise when the slope is not uniformly composed, but the displacement surface intersects layers of different composition; a landslide cuts into horizontal or inclined layers.

Security measures

Preventive measures

Explore information about possible places and approximate boundaries of landslides, remember the warning signals about the threat of a landslide, as well as the procedure for giving this signal. Signs of an impending landslide include jammed doors and windows of buildings and seepage of water on landslide-prone slopes. If you see signs of an approaching landslide, report this to the nearest landslide station, wait for information from there, and act depending on the situation.

What to do in case of a landslide

When receiving signals about the threat of a landslide, turn off electrical appliances, gas appliances and the water supply network, and prepare for immediate evacuation according to pre-developed plans. Depending on the speed of landslide displacement detected by the landslide station, act in accordance with the threat. If the displacement rate is low (meters per month), act according to your capabilities (move buildings to a predetermined location, remove furniture, belongings, etc.). If the landslide displacement rate is more than 0.5-1.0 m per day, evacuate in accordance with a pre-worked plan. When evacuating, take with you documents, valuables, and, depending on the situation and instructions from the administration, warm clothes and food. Urgently evacuate to a safe place and, if necessary, help rescuers dig out, extract victims from the collapse and provide assistance to them.

Actions after landslide displacement

After the landslide has moved, the condition of the walls and ceilings in the surviving buildings and structures is checked, and damage to the electricity, gas, and water supply lines is identified. If you are not injured, then together with the rescuers, remove the victims from the rubble and provide first aid.

Literature

• Landslides. Research and strengthening. M., 1981
• Petrov N. F. Landslide systems. Simple landslides: Aspects of classification. Chisinau: Shtiintsa, 1987. - 161 p.
• Petrov N. F. Landslide systems. Complex landslides: Aspects of classification. Chisinau: Shtiintsa, 1988. - 226 p.

Links

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See what “Landslide” is in other dictionaries:

landslide- Movement of rock masses, especially when they are saturated with water on a slope under the influence of the soil’s own mass and vibration (from passing trains), seismic and other loads. Source: SP 119.13330.2012: 1520 mm gauge railways 3.6 landslide... Dictionary-reference book of terms of normative and technical documentation

Sliding, avalanche, displacement, layer Dictionary of Russian synonyms. landslide noun, number of synonyms: 4 avalanche (31) layer ... Synonym dictionary

landslide- Separation and movement of masses of rocks down a slope under the influence of gravity [Terminological dictionary of construction in 12 languages ​​(VNIIIS Gosstroy USSR)] landslide Separation of earth masses or weakly cemented layered rocks and ... ... Technical Translator's Guide

Sliding displacement of earth masses under the influence of its own weight. In insurance practice, O. is considered as a risk circumstance or an insured event, as a result of which damage was caused to the insurance object. Dictionary of business terms... ... Dictionary of business terms

The movement of earth masses along a slope under the influence of gravity, associated in many cases with the activity of surface and groundwater. The slid mass is called a landslide body, and the surface along which it moves down... ... Geological terms

LANDSlide, a fairly rapid movement of rocks or soils sliding down a slope. Landslides can be caused by an earthquake, but more often they occur after heavy rainfall that leaves the ground wet. The intensity of landslides increases if... ... Scientific and technical encyclopedic dictionary

LANDSLAND, landslide, husband. (geol.). Shift, subsidence, downward movement of parts earth's surface due to erosion by soil water. Landslides often occur on high river banks. Dictionary Ushakova. D.N. Ushakov. 1935 1940 … Ushakov's Explanatory Dictionary

LANDSLAND, znya, husband. Sliding down a slope of a large layer of earth under the influence of water, moisture, as well as such a layer itself. Coastal landslides. | adj. landslide, oh, oh. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

The largest known landslide is located in the Heart Mountains in Wyoming (USA). It covers an area of ​​two thousand square kilometers and, judging by the remaining traces, in some places it spread at a speed of one hundred kilometers per hour. This catastrophe happened in the very distant past - about thirty million years ago.

In Europe, the first place belongs to the Flim landslide, which occurred in the Alps. Scientists suggest that it occurred before ice age and before humans appeared here (about a million years ago).

Twelve cubic kilometers of loose material moved into the Rhine River valley. This happened on the territory of what is now Switzerland near the city of Chur - where the village of Flim (canton of Grisons) is now located. The landslide fell into the Rhine, and the river valley was buried to a height of about six hundred meters. At first a lake two hundred meters deep formed, but it did not last long. The Rhine found another way, and the lake was drained.

And the largest landslide of historical time is considered to be the event that occurred on February 18, 1911 in the Pamirs. The landslide was caused by a strong earthquake, after which a fantastic amount of loose material—2.2 billion cubic meters—slipped from the slopes of the Muzkol ridge, from a height of five thousand meters above sea level. The village of Usoy with all its inhabitants, their property and livestock was overwhelmed. Rock formations blocked the valley of the Mugrab River. A huge dam with a diameter of four to five kilometers and a height of more than seven hundred meters stopped the flow of the river for four years. A new lake in the Pamirs appeared - Sarez, which began to grow rapidly and in turn flooded the villages of Sarez, Nisor-Dasht and Irkht.

In 1913, the length of Lake Sarez reached 28 kilometers, and its depth was almost 130 meters. Then the waters of Mugrab made their way through the stone blockage, but the lake still continued to grow. Today its length is already 75 kilometers, and its depth is about five hundred meters.

The force of the impact of the mass of earth and stones falling from a great height was so great that it generated a powerful seismic wave. It was recorded by seismic stations around the world, as it circled the globe several times.

The mystery of the Usoi landslide is its exclusively big sizes. Until now, scientists cannot say for sure whether there has ever been such a landslide on the globe (in historical times). Traces of a more gigantic one have not yet been found.

The roar of collapsing rocks (some scientists attribute this landslide to landslides) was heard by residents of Tajik villages located twenty kilometers from the village of Usoy. People called this place “Death Valley” and walked around it for a long time.

And the most tragic in terms of the number of victims was a landslide that occurred in the Chinese province of Gansu in 1920. Most of the territory of this province is occupied by a loess plateau, which suffered a terrible earthquake. Not only the strength of the earthquake, but also the specific soil conditions of Central China played a fatal role here. The affected area was in the center of the “land of loess” - fertile dust blown by winds from the Gobi Desert in the early Quaternary period. The fertility of the soil was the main reason that this area was densely populated.

Loess is very porous, but at the same time it has quite significant strength. Therefore, canyons and valleys with steep slopes are formed in loess areas. When the cohesion of the loess was disrupted by the earthquake, the slopes became unstable. Loess strata moved literally in entire hills. These hills buried tens of thousands of people who lived in caves dug in the loess. In one cave lived the Muslim prophet Ma the Blessed with his community of three hundred of his followers. They were cut off from the whole world and doomed to a slow and painful death. For a whole month afterwards, relatives and fellow believers of the victims dug up the loess cover that closed over their cave, but they could not find anything.

The tragedy was made even worse by the fact that it happened on a winter night. The ensuing darkness and cold forced almost the entire population to take refuge in their homes. At 7.30 pm a dull noise was heard from the north, “as if huge, heavily loaded vehicles were rushing at breakneck speed along the bad pavement.”

One missionary, who miraculously survived, later said:

“When I heard the noise, I thought it was an earthquake and ran outside. But as soon as I found myself on the street, I felt as if something had hit me in the back with terrible force.

With my legs spread wide, like a drunkard trying to stay on his feet, I felt a strong rotational movement of the earth beneath me...

This first and longest shock lasted two minutes. He was followed by five or six others, and so quickly that it was almost impossible to separate them from one another...

The shocks followed one after another with an interval of several seconds and merged with the deafening roar of collapsing houses, the screams of people and the roar of animals that came from under the rubble of buildings.”

The resulting landslides reached enormous proportions. The seven most gigantic of them cut off the slopes of the mountains, and thousands of cubic meters of loess filled up the valleys and covered cities and villages. One of the houses, captured by loess, was carried on a moving mass of rocks and simply miraculously remained on the surface. There was a man and a child in this house, but in the pitch darkness and deafening noise they didn’t even really understand what had happened. In the morning, a truly apocalyptic picture opened before them - “the mountains moved,” and they did not even recognize their native places.

The section of road that moved along with their house (about four hundred meters long) moved down one and a half kilometers. Having stopped, it subsequently almost retained its former appearance, and the tall poplars on both sides of the road continued, as before, to sway their branches. The house made a path of almost one kilometer, and then two other landslides caused the avalanche to change direction.

This place is also called “Death Valley” because 200,000 people were buried here.

In our country, landslides occur very often in the area Nizhny Novgorod. This was even reported in ancient chronicles. For example, in the 15th century, a landslide descended from Gremyachaya Mountain, which destroyed a large settlement. This is how this event is recorded in the chronicle: “And by God’s will, sin for our sakes, the mountain crawled from above the settlement, and one hundred and fifty households with people and all kinds of livestock fell asleep in the settlement.”

A large landslide also occurred on the night of June 17, 1839, near the village of Fedorovka on the left bank of the Volga between Saratov and Ulyanovsk. The earth moved underfoot, houses cracked and shook, there was noise and roar in the air.

Nobody understood what happened. People did not know where to run and how to save their lives. Women and children screamed and cried loudly. Dawn came, but it did not bring peace - everything around remained the same, and the earth even began to shake even more. In places it swelled, and in place of lowlands, hills grew, and in place of hills, gaps and cracks gaped.

The vibrations of the earth's surface (sometimes strong, sometimes weak) lasted for three whole days. And all this time the population was in constant anxiety and excitement. And when everything calmed down, it turned out (to the great amazement of the residents!) that the village of Fedorovka had “moved” closer to the Volga by several tens of meters.

LANDSlide, separation and sliding movement of a mass of rock down a slope; the sheer mass of displaced rock. O. are common in areas where weak plastic and impermeable rocks are covered by relatively strong permeable ones. The weakening of the strength of rocks is caused by natural causes (increasing the steepness of the slope, washing away its bases by waves and as a result of river erosion, waterlogging of soils with melt and rainwater, infiltration pressure in the rock mass caused by fluctuations in sea level, reservoir or river water, seismic tremors, etc. ) or human intervention (destruction of slopes by mountain and road excavations, excessive grazing or watering, deforestation, improper agricultural practices of slope agricultural lands, construction load on the edge or upper part of the slope, etc.). The emergence and activation of water is facilitated by the technogenic rise in groundwater levels on the banks of reservoirs. O. shift along the slope by several meters, often by tens and hundreds of meters. The volume of displaced rocks ranges from several tens of m3 to 1 billion m3. Large lakes form on steep slopes. 15° at a distance from watersheds, often occur on the sides of valleys, high shores of seas, lakes and reservoirs. They retain a certain coherence and solidity inside the landslide body, the thickness reaches 10–20 m or more. Small lakes transform the sides of ravines everywhere. Often O. are located on a slope in several tiers (for example, in the valley of the Moscow River).

In plan, landslides often have the shape of a crescent, forming a depression in the slope (the so-called landslide circus). Shallow cirque-shaped dents on the steep slopes of valleys and ravines - osovy - appear as a result of surface displacements of highly moistened loamy masses, especially with the slow melting of snow on shady slopes. After the rock is torn off and disappears, a bare surface or niche remains on a steep slope—a landslide ledge. Landslide breccia accumulates at the foot of the slope. A pressure landslide shaft may appear in front of the moving lake front. The tongue of the lake often extends into the waters of a watercourse or reservoir, changing the configuration of the coastline. The basis of the slide is the base of the slope or a separate flattened section of the slope, where the movement of landslide masses stops. Free sliding of a landslide body occurs if the shifting blocks are developed above the base of the slide; in the case when the thickness of plastic rocks lies below, these rocks are squeezed out, accompanied by their movement against the general slope (O. squeezing out I). Rocks that have not lost the natural composition of rocks in their blocks are classified as structural rocks. In “cutting” rocks, the sliding surface cuts off different layers of rocks. When fine particles of fine earth are washed out from the base of the lake by spring waters, weakening the stability of the overlying rocks, it is classified as a type suffosion O. (widely distributed on slopes with a steepness of 10–18°). Possible landslides-flows with a fluid consistency of soil, their volume can reach millions of m3. Small surface water-saturated lakes—slides (width up to several meters, depth from 0.3 to 1.5 m) are formed under conditions of excessive moisture to a plastic (mud-like) or fluid state.

Slopes susceptible to landslide processes are characterized by pseudo-terraces (often with a reverse slope), mounds, swampy closed or poorly drained semi-closed depressions and other forms of landslide relief, as well as a specific appearance of vegetation (for example, the so-called drunken forest). In O.'s body, rupture cracks are observed. In the European part of Russia, lakes are distributed along the sides of the valleys of large rivers (especially the Volga and its tributaries), reservoirs, and along the Black Sea coast. The coasts of the Black Sea are marked by powerful landslide activity - in Crimea, near Odessa (Ukraine) and in Adjara (Georgia). A wide strip of water stretches for hundreds of kilometers along the coasts of the Mangyshlak Peninsula (Kazakhstan). Landslide danger is observed in most mountainous countries (the eastern periphery of Tibet, the Himalayas, etc.). Lakes that come down from the sides of mountain valleys often form temporary dams that dam the river, forming a landslide lake. The catastrophic consequences of a flood wave resulting from the destruction of such a dam many times exceed the negative consequences of the displacement of the reservoir itself. Great damage to the reservoir is caused to agriculture. lands, industrial enterprises, populated areas, etc. To combat them, bank protection and drainage work, forest planting, and securing slopes with piles are carried out.

On relatively steeply inclined areas of the bottom of oceans, seas, and deep lakes in seismically and volcanically active zones, as well as on the frontal slopes of underwater deltas (as a result of sharp differences in sedimentation rates), underwater oceans are found; one of the largest is the Sturegga landslide in the Norwegian Sea (length approximately 800 km, width 290 km). Underwater oxygen can cause the rupture of submarine cables, which has happened repeatedly, in particular, at the bottom of the Atlantic Ocean.

Table. Catastrophic landslides*

*The table shows landslides that led to large-scale destruction (including seabed), either to numerous human casualties, or to a fundamental negative change in the natural landscape.