Consequences after landslides and landslides. What is a landslide and how dangerous is it? Nature of occurrence and classification of landslides, landslides, mudflows, snow avalanches

Unfortunately, even today, people sometimes find themselves powerless in the face of natural disasters, destroying houses, destroying property, and sometimes claiming human lives.

One of these disasters is a landslide - a phenomenon that is quite common in mountainous areas or uplands that are subject to erosion.

What is a landslide?

Landslides are called displacements of large masses of loose soil, which are separated from the slopes and rush down, sliding down an inclined plane into the valley. The soil can be dry or wet, in the latter case it is called mudflow or mudflow.

The speed of movement of landslides is different: sometimes a huge mass collapses in a matter of minutes, but often they move almost imperceptibly, at a speed not exceeding several centimeters per year. A slow landslide can accelerate at any time and turn into an unexpected and dangerous landslide.

The distance covered by a landslide depends on its mass and the height of the fall. Some of them cover an area of \u200b\u200bup to 400 hectares. The scale of the phenomenon is determined by the amount of sliding rock mass:

- up to 10,000 cubic meters m - small landslide;

- from 10,000 to 100,000 cubic meters m - medium landslide;

- from 100,000 to 1,000,000 cubic meters m - large landslide;

- more than a million cubic meters m - the largest landslide.

Fortunately, major landslides are rare, but sometimes dire. Entire villages can be buried under the mass of rock if the movement of the rock is not detected in time and people are not resettled.

How and where do landslides form?

These phenomena are most frequent in mountainous regions with a predominance of loose rocks, i.e. in geologically old mountains, where erosion has led to soil loosening. Landslides are also frequent on steep river banks, where they occur mainly due to the erosion of the coast by water.

A visor of sandy or clayey rock forms above the water, which once collapses or slides down under its own weight. If a river landslide is large enough, it can even slightly change the river bed, forming a new bend or island in it.

As a rule, mountain landslides form on slopes, the steepness of which reaches 19 degrees, and the height ranges from one to two thousand meters. If the soil consists mainly of clay and is highly moistened, then a slope of only 5 degrees is enough for the rock to move down.

As in the case of river banks, the main cause of mountain landslides is the erosion of rocks by sedimentary water flows or groundwater. Landslides usually occur after heavy or prolonged rains, when the soil becomes saturated with water, heavy and has lost its normal cohesion between solid particles. Water acts as a lubricant to facilitate downward movement by gravity.

Less often, but also quite often, landslides occur as a result of tremors. They are most dangerous under water, on the sea shelf. A breakaway large section of the seabed can cause a gigantic wave - a tsunami, dangerous both for the nearby coast and for ships encountered on its way.

In recent decades, landslides resulting from human activities have become more frequent. Rock collapse can cause ground vibration if a road is built near the slope and heavy trucks are constantly driving. Explosive development of minerals can also provoke a downward movement of a loose formation.

Sometimes the "trigger" for a landslide is construction, during which workers drive piles into the ground, thereby spreading a shock wave in its thickness. Thoughtless deforestation of deserted mountain slopes is also often subject to landslides, as tree roots no longer hold soil particles together.

The consequences of landslides

The most dangerous are landslides that occur in populated areas. Even a small rock collapse can lead to the death of a person caught in his path. A man covered with several tons of rock dies in a matter of minutes from compression and lack of air. But it is much worse if, as a result, houses, cars, tourist camps or industrial enterprises are buried under a layer of soil. The number of victims in such cases turns out to be quite large.

One of the largest landslides in recent decades was the resulting rock collapse in Tajikistan. Then the death toll exceeded two hundred people: about 50 houses in the village of Sharora were covered with rock. The width of the collapse was more than four hundred meters, and the wavelength was about four kilometers.

In order to avoid such accidents, it is necessary to carefully examine all slopes located in the immediate vicinity of housing, roads, businesses, and record even the smallest ground movements. The slow movement of the landslide mass can at any moment turn into a destructive wave falling down on a defenseless village.

Mudflows are streams of mud and stones that slide down mountain slopes and riverbeds, sweeping away any obstacle in their path. This natural phenomenon is one of the most dangerous for human life and the infrastructure of settlements.

Mudflows

During the rapid melting of glaciers in the mountains, as well as after heavy rains, storms, hurricanes, water accumulates in front of a natural obstacle. In some places, rather large lakes and reservoirs are formed. Such formations are called moraine lakes, it is they that, after some time, transform into landslides, mudflows, avalanches and avalanches. Moraines consist of:

Sand.
Boulders.
Ice and snow.
Hard rocks.
Crushed stones.
Clays.

At some point, a huge mass of mud, mixed with water and rocks, breaks through the dams, rushing down in a rapid stream. Developing a tremendous speed, emitting a loud roar, the stream picks up more and more stones and trees along the road, thereby increasing its destructive power.

Sit down at the beginning of their movement reach no more than 10 meters in height. After a natural disaster breaks out of the gorge and rushes down the mountain, it will spread over the flat surface. Its travel speed and height will be significantly reduced. Having reached any obstacle, he stops.

The consequences of the descent of rocks and water

In the event that a settlement is on the way of the mudflow, the consequences for its population can be catastrophic. deadly, and often leads to large material losses. Especially a lot of destruction is caused by the descent of rocks and water in the villages where people live in poorly fortified frame houses.

The consequences of landslides, mudflows and avalanches can be catastrophic. Thus, a major disaster took place in 1921 in the former capital of Kazakhstan - Alma-Ata. Late at night, a powerful mountain stream of about a million cubic meters hit the sleeping city. As a result of an emergency, right in the middle of the city, a strip of stones and mud 200 meters wide was formed. Buildings were destroyed, infrastructure was damaged, people died.

In Russia, mudflows are also often formed in mountainous areas, especially in places where there are heavy rains, for example, in the Caucasus and the Far East. In Tajikistan, mudflows happen every year in the spring. Especially often this phenomenon occurs in high mountains during snow melting.

Mudflow protection

To protect the population and tourists from sudden rock falls in especially dangerous mountain areas, where landslides, mudflows, avalanches and avalanches periodically occur, it is necessary to monitor them from the air. Experts monitor the formation of mountain lakes and can tell in advance about the danger of an emergency. Also, engineers are developing anti-mudflow artificial barriers and branch channels, which are several hundred kilometers long.

In 1966, near the city of Alma-Ata, a protective dam was built of earth and large cobblestones. The total weight of construction materials was about 2.5 million tons. 7 years later, it saved the lives of many citizens, blocking the city from unprecedented power.

Despite the fact that in most cases mudflows fall from the mountains suddenly, scientists have learned to predict their approach by some signs, for example, by a change in the color of the water in a mountain lake.

Survival during an emergency

Tourists who often travel in the mountains should be aware of the danger of landslides, mudflows, landslides, and life-saving. Safety rules may one day save your life!

To properly prepare for a difficult and long hike in the mountains, you should check the weather forecast before going out. If it is pouring rain in the mountains, the likelihood of mud flows going down significantly increases. For safety, it is better to keep to the inner part of the bend of the rivers, since mudflow rises much higher on the outside. Also, do not spend the night near mountain lakes and rivers, as well as in narrow gorges.

What are landslides

A landslide is a downslope displacement of a formed mass of rocks. The reason for their occurrence is most often heavy rains, as a result of which rocks are washed away.

Landslides can occur at any time of the year, and differ from each other in the scale of destruction. Slight rock displacement damages roads. Significant destruction and spalling of stones leads to the destruction of houses, as well as human casualties.

Division of landslides into species

Landslides are classified as slow, medium and fast. The first ones move at an insignificant speed (several centimeters per year). Average - several meters per day. Such displacements do not lead to disasters, but sometimes such natural phenomena lead to the destruction of houses and outbuildings.

Rapid landslides are considered the most dangerous, because in this case, streams of water with stones break down from the mountains and move down at a tremendous speed.

All movements of rocks and clay masses can be predicted by looking at the following signals:

new cracks and crevices have formed in the soil;
falling stones from the mountains.

How to avoid destruction and casualties

Against the backdrop of incessant downpours, the above signals should become harbingers of danger for the special services and the population. Timely detection of signs of an impending landslide will help to take measures to rescue and evacuate the population.

As a prophylaxis and protection against destruction near cities, protective nets, artificial tunnels are built, as well as a vegetation cover of trees. Bank protection structures and piles have also proven themselves well.

Where do they arise

Many people wonder about where avalanches, landslides, mudflows and avalanches occur most often. The displacement of rocks, huge masses of snow and water occurs in areas or slopes as a result of imbalance, which is caused by an increase in the steepness of the slope. This is mainly due to several reasons:

Heavy rains.
Weathering or waterlogging of rocks by groundwater.
Earthquakes.
Construction and economic activities of a person, in which the geological conditions of the area are not taken into account.

The landslide is intensified by the inclination of the earth towards the cliff, cracks on the top of the mountain, which are also directed towards the slope. In places where the soil is most wet with rain, landslides take the form of a stream. Such natural disasters cause enormous damage to agricultural land, businesses and settlements.

In the mountainous areas and northern regions of our country, the soil thickness is only a few centimeters, and therefore it is very easy to disturb it. An example is a place in the Eagle Sopka region (Vladivostok city), where uncontrolled deforestation began in the early 2000s. As a result of human intervention, vegetation on the hill disappeared. After each downpour, mud pours onto the streets of the city, which was previously blocked by trees.

Landslides are often found in areas where slope erosion processes are actively taking place. They occur when rock masses lose support as a result of imbalance. A massive landslide occurs in areas where:

mountain slopes, composed of alternating waterproof and aquifers;
man-made rock dumps near mines or quarries.

Landslides moving from the side of a mountain in the form of a pile of debris are called rockfalls. If a huge block of stone slides over the surface, then such a natural phenomenon is called a collapse.

Cases of large landslides

To learn more about the largest convergence of landslides, mudflows, landslides, avalanches and the consequences for people, you should refer to the historical literature. Witnesses of terrible disasters often describe the descent of large masses of rocks and avalanches from ancient times. Scientists believe that the largest stone gathering in the world occurred at the beginning of our era near the Saidmarreh River in southern Iran. The total mass of the landslide was approximately 50 billion tons, and its volume was 20 cubic kilometers. A mass, consisting of stones and water, fell from the Kabir-Bukh mountain, the height of which reached 900 meters. The landslide crossed the river 8 kilometers wide, then it crossed the ridge and stopped after 17 kilometers. As a result of the blocking of the river, a large lake 180 meters deep and 65 kilometers wide was formed.

In the ancient Russian annals there is information about huge landslides. The most famous of them dates back to the 15th century in the region of Nizhny Novgorod. Then 150 households suffered, many people and farm animals suffered.

The scale of destruction and the consequences of landslides and mudflows depend on the density of buildings and the number of people living in the disaster area. The most devastating landslide occurred in Gansu Province, China in 1920. Then more than 100 thousand people died. Another powerful landslide that killed 25 thousand people was registered in Peru (1970). As a result of the earthquake, a pile of stones and water hit the valley at a speed of 250 kilometers per hour. During the natural disaster, the cities of Ranrahirka and Yungai were partially destroyed.

Landslide forecast

To predict the occurrence of landslides and mudflows, scientists constantly conduct geological research and draw up maps of hazardous areas.

Aerial photography is carried out to identify areas of accumulation of landslide material. The images clearly show the places where rock debris is most likely to come down. Also, geologists determine the lithological features of the rock, the volume and nature of the flow of groundwater, vibration as a result of earthquakes, as well as the angles of slopes.

Landslide protection

If the likelihood of landslides and mudflows is high, then special services take measures to protect the population and buildings from such a natural phenomenon, namely, they strengthen the slopes of the coast of seas and rivers with a wall or beams. Soil slippage is prevented by driving piles in a checkerboard pattern, trees are planted, and the ground is artificially frozen. To prevent wet clay from coming off, it is dried by electroosmosis. Landslides and mudflows can be prevented by pre-building drainage structures that can block the path of groundwater and aboveground water, thereby preventing soil erosion. Surface water can be diverted by tearing out canals, underground water by means of wells. Such measures are quite expensive to implement, but such measures can prevent the destruction of buildings and avoid human casualties.

Public warning

The population is warned about the danger of earthquakes, landslides and mudflows in a few tens of minutes, at best a few hours. To alert a large populated area, the alarm is sounded with a siren, and announcers also announce the danger on television and radio.

The main damaging factors in landslides and mudflows are mountain boulders that collide with each other during their movement from the mountains. The approach of rocks can be identified by the characteristic loud sound of rolling stones.

The population living in a particularly dangerous mountainous area, where avalanches, mudflows and landslides are possible, should know from which side trouble may come, what the nature of the destruction will be. Also, residents should be well aware of the escape routes.

In such settlements, houses and territories on which they were built should be fortified. If the danger is known in advance, an urgent evacuation of the population, property and animals to safe areas is carried out. Before leaving home, you should take your most valuable items with you. Any other property that cannot be taken with you should be packed to protect it from dirt and water. Doors and windows should be closed. You also need to close the ventilation hole. It is imperative to shut off the water and gas, turn off the electricity. Poisonous and flammable substances must be removed from the house, they are placed in pits remote from housing.

If the population has not been warned in advance about landslides and mudflows, each resident must find shelter on his own. It is also necessary to help children and the elderly to hide.

After the end of the natural disaster, you should make sure that there is no danger, leave the shelter and start looking for victims, if necessary, you need to help them.

Lesson 5. Landslides, their consequences, protection of the population. Landslides and avalanches.

The purpose of the lesson.Provide students with a general understanding of landslides and the causes of their occurrence; to acquaint with the consequences of the landslide; to reveal the organizational basis for protecting the population from the consequences of landslides. To acquaint students with landslides and avalanches, the reasons for their occurrence; analyze the main measures taken to protect the population from the consequences of landslides and avalanches.

Issues under study

Landslides and their causes.

Possible consequences of a landslide.

Protection of the population from the consequences of landslides.

Landfalls, causes of their occurrence, possible consequences.

Snow avalanches, causes of their occurrence, possible consequences.

Protection of the population from the consequences of landslides and avalanches.

1 ... Give a definition of a landslide and reveal the causes of its occurrence (natural and artificial).

It is known that most of the Earth's surface is slopes.

Slopes include areas of the surface with inclination angles exceeding 1 °. Slopes occupy at least 3/4 of the land area.

Natural causes include: the magnitude of the steepness of the slopes; occurrence on the slope of clay rocks, especially if they are highly moistened; erosion of the foundations of slopes by sea and river waters, as well as seismic shocks (earthquakes).

Artificial reasons include: destruction of slopes during road construction; excessive ground outward; deforestation; unreasonable farming on the slopes.

Landslides come at any time of the year, but especially vigorously in the spring or during summer rains. On the shores of the seas, landslides develop after strong storms.

In Russia, landslides quite often occur in the Volga region - in the Saratov region, in the Volgograd region; on the banks of the Don, the Tsimlyansk reservoir, in the Kuban valley, in many regions of Siberia and the North Caucasus.

2. To draw the attention of the students to the possibility of emergencies when a significant mass of rock is displaced by landslides. Landslides can destroy individual objects and endanger entire settlements, destroy agricultural land, create o danger during the operation of quarries, damage communications, tunnels, pipelines, telephone and electrical networks, and lead to death.

What has been said can be supported by examples.

On January 23, 1984, as a result of an earthquake in the Gissar region of Tajikistan, a landslide occurred 400 m wide and 4.5 km long. Huge masses of land covered the village of Sharora. 50 houses were buried, 207 people died!

In 1989, landslides in Ingushetia led to destruction in 32 settlements, 2518 houses were damaged.

In the spring of 1994, after an unusually snowy winter in Kyrgyzstan, huge landslides occurred in many regions, destroying hundreds of houses and causing human casualties.

3. To acquaint students with the main activities carried out in the country to protect the population from the consequences of landslides: control over landslides and their forecast; holding
anti-landslide measures.

If a landslide cannot be prevented, then the population is notified of the threat, and an evacuation is organized.

At the end of the lesson, it is advisable to discuss with the students the recommendations of the EMERCOM of Russia specialists on actions in the event of a landslide threat: to know the warning signals about the threat of a landslide, as well as the procedure for receiving this signal (turn off electrical appliances, gas appliances and the water supply network, prepare for immediate evacuation).

The following landslide speeds are distinguished:

extremely fast - up to 3 m / s;

very fast - 0.3 m / min;

fast - 1.5 m / day;

moderate - 1.5 m / month;

very slow - 1.5 m / y;

extremely slow - 0.06 m / g.

After the displacement of the landslide in the surviving buildings and structures, check the condition of the walls, ceilings, identify damage to the lines of electricity, gas and water supply. If you are not injured, then together with the rescuers, remove the victims from the blockage and provide them with assistance.

4. Define the concept of "collapse", show the main causes and possible consequences of a collapse.

Landfalls are observed in the mountains, on the seashores and on the cliffs of river valleys.

In the mountains, landslides are more often formed in areas with a highly dissected relief, with steep, steep mountain slopes.

Landfalls on the sea shores and on the cliffs of river valleys occur due to the undermining and dissolution of rocks on the shores of seas and rivers.

Landslides can destroy and damage bridge piers, power lines, and threaten the safety of railway trains and other ground transport. For example, the Tuapse - Sukhumi railroad runs along the very coastal edge of the Black Sea. On the one hand, it is threatened by the occurrence of a rock collapse, eroded by the waters of the sea, on the other hand, mountain cliffs hang over the railway track.

5. Define the concept of "avalanche", analyze the causes of avalanches and their possible consequences, give examples of the tragic consequences of avalanches for tourists.

The occurrence of avalanches is possible in all mountainous areas where snow cover is established. Avalanche-prone areas in Russia are the Kola Peninsula, the Urals, the North Caucasus, Eastern and Western Siberia, and the Far East.

The impact force of a falling avalanche can reach from 5 to 50 tons per square meter. Falling snow avalanches can cause destruction of buildings, engineering structures, cover roads and mountain paths with snow. Residents of mountain villages, tourists, climbers, geological prospectors and other people trapped in the mountains and trapped by an avalanche can get injured and find themselves under a layer of snow.

6. Of great importance for the protection of the population from the consequences of landslides and avalanches is their forecasting (special observation system). Based on the forecasts received, preventive measures are planned and implemented.

In conditions of the threat of avalanches, they organize control over the accumulation of snow in avalanche-prone directions, and artificial descent of emerging avalanches is caused during the period of their least danger. Protective structures are being built in avalanche-prone areas, life-saving equipment is being prepared and rescue operations are planned. The population is being alerted about the danger of avalanches.

At the end of the lesson, the recommendations of the EMERCOM specialists for the population living in avalanche-prone areas should be discussed.

Control questions

What natural phenomena are called landslides and what are the reasons for its occurrence?

What are the consequences of landslides?

What measures are being taken to protect the population from the consequences of landslides?

What is a collapse and what are the reasons for it?

What is an avalanche and what are the causes of it?

What measures are being taken to protect the population from landslides and avalanches?

Why is it necessary to follow the rules of safe conduct in avalanche areas?

Homework

Study § 2.6, 2.7 of the textbook.

Mudflows, landslides, avalanches

Sel - a temporary mud and mud-stone flow suddenly forming in the channels of mountain rivers with a high content (up to 75%) of rocks, resulting from intense and prolonged heavy rains, rapid melting of glaciers or seasonal snow cover and other phenomena. Mudflow is characterized by a significant destructive force of the ground, which is approaching, arises suddenly, moves at a speed of over 10 m / s, and can reach over 15 meters in height. An avalanche is characterized by the rapid, sudden movement of mud flow down steep mountain slopes. The main danger of mudflows is manifested in the form of a direct shock effect on people and obstacles (structures, buildings, life support systems).

The consequences of mudflows:

· A significant number of injuries and human casualties;

· Filling up with mud-stone mass and destruction of houses and structures, potentially dangerous objects, roads, bridges, engineering structures, life support systems;

· Destruction of forests and significant losses to agriculture.

Landslides- sliding displacement of rock masses down the slope under the influence of gravity. They arise in any part of the slope or slope due to the imbalance of rocks caused by:

· Increased slope steepness as a result of water washout;

· Weakening of strength of rocks during weathering or waterlogging by precipitation and groundwater;

· The impact of seismic shocks;

· Construction and economic activities carried out without taking into account the geological conditions of the area (destruction of slopes by road excavations, excessive watering of gardens and vegetable gardens located on the slopes, etc.).

The main damaging factor of landslides is heavy masses of soil, filling or destroying everything in its path.

Landslides can destroy homes and endanger entire communities. They threaten agricultural land, destroy it and make it difficult to cultivate it. Landslides damage communications, tunnels, pipelines, telephone and electrical networks; threaten water facilities, mainly dams. In addition, they can block the valley, form temporary lakes and contribute to flooding, and generate disastrous waves in lakes and bays. As a result of landslides, river beds, roads can overlap, and the landscape changes. Landslides threaten the safety of road and rail transport. Destroy and damage bridge pillars, rails, road surfaces, oil pipelines, hydroelectric power plants, mines and other industrial enterprises.

In case of a landslide threat and in the presence of time, an early evacuation of the population, farm animals and property to safe areas is organized. Valuable property that cannot be taken with you should be protected from moisture and dirt. Doors and windows, ventilation and other openings are tightly closed. Electricity, gas, water supply are cut off. Flammable, poisonous and other hazardous substances are removed from the house and, as soon as possible, are buried in pits or cellars. In all other respects, citizens act in accordance with the procedure established for organized evacuation.

Snow avalanches -it is a concentrated movement of snow masses falling or sliding from mountain slopes in the form of a solid body (wet avalanches) or sprayed snow (dry avalanches). Avalanches occur as a result of snow accumulation on mountain peaks as a result of heavy snowfalls, severe blizzards, and a sharp drop in air temperature. Snow avalanches can also come from the loose horizon of deep rime formed in the thickness of the snow - in the Alps it was called quicksand snow.Avalanches especially fall from the slopes in the spring when the snow becomes wet and the bonds between individual snow crystals are weakened. Avalanches usually come down periodically on the same parts of the slope. By the nature of the movement, they are divided into:

· the main

· trough

· jumping

The most harmless the main is the sliding of snow masses from slopes outside certain channels. As a rule, the wasps are small. Most avalanches descend along specific avalanche troughs - narrow hollows on steep slopes. Along these hollows, 200-300, and sometimes 500 thousand tons of snow can simultaneously fall. Special jumping dangerous avalanches that meet on their way "trampolines" from which they "jump" into the valley, gaining very high speed and causing significant destruction. Quite often avalanches sneak up suddenly, sometimes even silently. There are times when an air wave moves in front of the falling snow masses, which brings even greater destruction.

When huge masses of rocks are toppled from the slopes under the influence of gravity, not everyone is able to escape. Especially when it comes to a landslide or a village that originated high in the mountains, when a huge amount of sedimentary rocks diluted by the waters of rivers, showers or melted snows rushes down at great speed.

A landslide is a mass of loose rocks separated from the slopes, which slides down an inclined plane without losing its connectivity and solidity. They can be either dry or moist to create a fluid flow.

Each landslide has its own speed, and therefore it often happens that the process of movement is completely invisible to the human eye, since it is only 0.06 meters per year. True, this is not always the case: landslides are quite capable of rushing at a stunning speed of 3 m / s.

In this case, if the relevant services do not have time to warn the population about landslides, the collapse often has catastrophic consequences. For example, one of the largest landslides that came down as a result of an earthquake in Tajikistan was four hundred meters wide and more than four kilometers long. After huge masses of rushing rock that day covered the village of Sharora, the consequences were dire: landslides buried 50 houses under them, as a result of which more than two hundred people died.

Landslides can move at different distances, up to four hundred hectares, and according to the amount of moving mass, landslides are:

small - collapse of loose mass up to 10 thousand m3;
medium - collapse of soil 100 thousand m3;
large - collapse of loose masses of 1000 m3;
the largest - a collapse of more than 1 thousand m 3.

Landslides

Most often, a landslide forms on the coast of rivers, water bodies and on the slopes of mountains: 90% of the shifts are recorded at an altitude of one to two kilometers. At the same time, a landslide is formed on slopes, the angle of which is nineteen degrees, and on clay soil, with strong moistening of rocks, landslides also descend with a slope of five degrees.

Despite the fact that the reasons for the occurrence of such a displacement of the land are different, landslides are formed mainly due to the undermining of rocks by water in combination with weathering and waterlogging. Also, a landslide can come off as a result of an earthquake, erosion of slopes by sea or river waters.

The collapse of the soil, caused by natural causes, occurs mainly after showers, which so much wet the soil that it becomes mobile. At this moment, the friction force that adheres it to the slopes is weaker than the force of gravity, which sets the rocks in motion.

One of the most dangerous and unexplored is an underwater landslide that forms during the movement of sedimentary rocks at the edge of the shelf (the consequences are dangerous because they raise a tsunami). According to statistics, about 80% of landslides are due to human activities - laying roads on slopes, deforestation, and unreasonable farming.

Mudflow

Despite the fact that mudflow is also a descending stream of loose masses, it differs from landslides in that it is a mountain river flowing downward, into which a huge amount of loose rock fell.

The reasons for their appearance are heavy rains, increased snow melting, the collapse of a large amount of loose soil into the river or the breakthrough of debris, due to which a sharp rise in water occurs.

After that, the river transforms into a large stream of destructive force, and in such a village there is a mixture of water, stones, loose soil (about 60%). The height of the front line of the mudflow is from 5 to 15 meters, and the wave can rise up to 25 meters.

The higher the mudflows originate, the more destructive the collapse. Alpine mudflows begin at an altitude exceeding 2.5 thousand km. Such mudflow from one square kilometer can take out about 26 thousand m3 of rocks. Whereas middle-mountain mudflows (from 1 to 2.5 thousand km) carry from 5 to 15 thousand m3 from an area of \u200b\u200bthis size, low-mountain ones - no more than 5 thousand m3.

Mudflows are formed in different ways:

If the collapse was caused by erosion processes, due to the washout and erosion of the nearby soil, clastic material first enters the stream, after which a mudflow wave is directly formed.
Mudflow can also appear due to blockage, when waves begin to accumulate in one place, eroding rocks. Since it cannot go on for so long, the mass in the village breaks the blockade and rushes down.
Another method of formation, when the maximum saturation of loose masses is found in the village, is due to a landslide collapse into river waters.

The mudflow does not flow continuously, but in waves, carrying out at a time hundreds, and in some cases - millions of cubic meters of viscous substance in the village (some lumps in the village can often weigh about 100 tons). The phenomenon can have different powers:

Small flow is a frequent phenomenon, it occurs annually, in this village there is no more than 10 thousand m3 of rock;
The flow of average power is formed once every two to three years; the village contains from 10 to 100 thousand m3 of soil.
A strong flow occurs once every five to ten years, and such a village contains at least 100 thousand m3 of loose rock.

Since mudflows are part of a mountain river, they are able to move at a speed of about 10 m / s, so they go down very quickly, in 20-30 minutes, and the phenomenon itself lasts from one to three hours (if a mudflow hits an obstacle, then, growing , the stream passes over it, increasing its energy).

Moreover, only the consequences of a small flow do not lead to disastrous results. A mudflow of medium power, gaining speed, is capable of demolishing baseless structures, while a powerful mudflow, carrying with it a huge amount of loose soil, boulders and other obstacles captured along the road, destroys buildings, roads, destroys trees, floods fields and kills all living things that on a way.

What to do during landslides

People living or staying in areas where landslides and mudflows are common should be well aware of the signs and characteristics of these dangerous landslides. For example, one of the first signs of impending disaster is water seepage on the slopes.

Therefore, as soon as the first signs of dangers appear (despite the rapid nature of the elements, modern equipment makes it possible to record their appearance in time), the inhabitants of the region are usually evacuated. Before leaving your homes, you must tightly close all ventilation ducts, window and door openings, turn off the electricity, gas, shut off the water.

If it so happened that landslides or mudslides appeared suddenly and move so fast that they did not have time to warn the population in time and people received information a few minutes before the appearance of a mud stream or even noticed it themselves, you need to immediately run away to a safe place. Usually these are hills or mountains that are away from the stream (it is desirable to rise to a height of at least 100 meters). During the ascent, you must not leave the valleys or gorges, as lateral mudflows may appear there.

If it happens that people and structures are on the moving part of the landslide, you need to leave the room, go up, and while the moving mass stops, beware of rolling boulders, stones and other objects. It must be borne in mind that a very strong shock may occur during the landslide stop, and be prepared for this.

When the landslide or mudflow stops, you need to return not immediately, but after a few hours, since there is a danger that a new landslide will occur. If there are no signs that the landslide or mudflow may repeat itself, you can return home, after which you can immediately start looking for and retrieving victims in the village, freeing cars and other vehicles blocked by mud.