The largest landslides in history. NASA will begin tracking landslides around the world The largest landslides in history

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 a very pressing 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 the devastating earthquake died under layers of sliding earth.

Landslide record holder

Landslides occur quite frequently around the world. The 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 related to geographic location and can occur in any country, including Russia. Most often, residents of the North Caucasus, Volga region, Primorye, Eastern Siberia and the Urals have to deal with this natural phenomenon.

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 especially increases in the autumn-winter period, when the mountain slopes are washed away by rain. Active human activity, including construction and impact on the landscape, is also an additional risk factor.

Landslides most often occur when the underlying bedrock, composed of limestone or other carbonate rock, is eaten away by acidic groundwater, subsides after heavy rainfall, or is damaged by pipe ruptures. Such sudden collapses are especially dangerous, for obvious reasons, in cities, where entire houses can suddenly go underground. Below you will find photographs from the sites of the largest landslides in recent decades.

In May 1981, this giant hole appeared within the city of Winter Park (Florida). Local authorities decided, by strengthening the edges, to turn the resulting hole into a picturesque city lake (above in the photo).

In 1995, two houses in a fashionable area of ​​San Francisco fell into this hole (18 m deep, 60 m long and 45 m wide).

In 1998, after unusually heavy rainfall and a sewer pipe ruptured in San Diego, a giant crack appeared. Its length is about 250 meters, width – 12 meters and depth – more than 20 meters.

In 2003, rescuers had to pull out this bus with a crane after it suddenly fell into the ground on a street in Lisbon (Portugal).

This hole swallowed up several houses in the capital of Guatemala in February 2007. Three people are missing.

Bird's eye view.

In March 2007, in the Italian city of Gallipoli, a road collapsed into a network of underground caves underneath.

In September 2008, a car driving along one of the streets in the Chinese province of Guangdong suddenly found itself in a hole 5 meters deep and 15 meters wide.

This giant crater was formed in May 2010 in Guatemala City after Tropical Storm Agatha swept through it.

The same funnel from a closer distance.

In May 2012, as a result of a soil collapse on the roadway in the Chinese province of Shaanxi, this hole appeared 15 meters long, 10 meters wide and 6 meters deep.

And another landslide in Shaanxi (6 meters deep and 10 meters wide) damaged three gas pipes and one water pipe in December 2012.

This giant hole formed one December night in 2012 in southern Poland. Its depth is about 10 meters, width is about 50 meters.

In January 2013, part of a rice field in the Chinese province of Hainan fell into the ground. Over the previous four months, there were about 20 similar incidents in the district.

Landslides- This is a sliding displacement of rock masses down a slope under the influence of gravity.

They are formed in various rocks as a result of an imbalance or weakening of their strength. Caused by both natural and artificial (anthropogenic) reasons. Natural ones include: increasing the steepness of slopes, eroding their bases with sea and river waters, seismic tremors. Artificial causes include the destruction of slopes by road cuttings, excessive removal of soil, deforestation, and unwise farming on slopes. According to international statistics, up to 80% of modern landslides are associated with human activity. A significant number of landslides occur in mountains at altitudes from 1000 to 1700 m (90%).

Landslides can occur on all slopes, starting from a steepness of 19°. However, on clay soils they also occur at a slope steepness of 5-7°. For this, excessive moisture of the rocks is sufficient. They come at any time of the year, but mostly in the spring and summer.

Landslide classification

Landslides are classified: according to the scale of the phenomenon, speed of movement and activity, mechanism of the process, power and place of formation.

By scale Landslides are classified into large, medium and small scale.

Large ones are usually caused by natural causes and form along slopes for hundreds of meters. Their thickness reaches 10-20 meters or more. The landslide body often retains its solidity.

Medium and small-scale ones are smaller in size and are characteristic of anthropogenic processes.

Scale is often characterized by the area involved. In this case, they are divided into grandiose - 400 hectares or more, very large - 200-400 hectares, large - 100-200 hectares, medium - 50-100 hectares, small - 5-50 hectares and very small - up to 5 hectares.

By speed very diverse, as can be seen from table. 2.3.

By activity Landslides are divided into active and inactive. The main factors here are the rocks of the slopes and the presence of moisture. Depending on the amount of moisture, they are divided into dry, slightly wet, wet and very wet. For example, very wet ones contain such an amount of water that creates conditions for liquid flow.

According to the mechanism of the process are divided into: shear landslides, extrusion landslides, viscoplastic landslides, hydrodynamic landslides, and sudden liquefaction landslides. Often have signs of a combined mechanism.

By process power landslides are divided into small - up to 10 thousand m 3, medium - from 11 to 100 thousand m 3, large - from 101 to 1000 thousand m 3, very large - over 1000 thousand m - the mass of rock involved in the process.

By place of education they are divided into mountain, underwater, adjacent and artificial earthen structures (pits, canals, rock dumps).

Landslides cause significant damage to the national economy. They threaten the movement of trains, road transport, residential buildings and other buildings. When landslides occur, the process of land removal from agricultural use is intensive.

Table 2.3. Characteristics of landslides based on movement speed

They often lead to human casualties. Thus, on January 23, 1984, as a result of an earthquake in the Gissar region of Tajikistan, a landslide 400 m wide and 4.5 km long occurred. Huge masses of earth covered the village of Sharora. 50 houses were buried, 207 people died.

In 1989, landslides in Ingushetia led to destruction in 82 settlements. 2,518 houses, 44 schools, 4 kindergartens, 60 healthcare, cultural, trade and consumer services facilities were damaged.

A type of landslides are snow avalanches. They are a mixture of snow crystals and air. Large avalanches occur on slopes of 26-60°. They are capable of causing great damage, resulting in loss of life. So, on July 13, 1990, on Lenin Peak in the Pamirs, as a result of an earthquake, a large snow avalanche demolished the climbers’ camp, located at an altitude of 5300 m. 40 people died. It was the biggest tragedy in domestic mountaineering.

Mudflow

Mudflow (mudflow)- a rapid mud or mud-stone flow, consisting of a mixture of water and rock fragments, suddenly appearing in the basins of small mountain rivers.

It is characterized by a sharp rise in water level, wave movement, short duration of action (on average from one to six hours), and a significant erosion-accumulative destructive effect.

Mudflows pose a threat to populated areas, railways, roads and other structures located in their path.

The immediate causes of mudflows are showers, intense snow melting, breakthrough of reservoirs, less often earthquakes, volcanic eruptions.

Classification of mudflows

All ifs, according to the mechanism of nucleation, are divided into three types: erosive, breakthrough And landslide.

With erosion, the water flow is first saturated with debris due to the washout and erosion of the adjacent soil, and then a mudflow wave is formed.

Breakthrough is characterized by an intensive process of water accumulation, at the same time rocks are eroded, a limit is reached and a breakthrough of a reservoir (lake, intraglacial reservoir, reservoir) occurs. The mudflow mass rushes down the slope or river bed.

During a landslide, a mass of water-saturated rocks (including snow and ice) is torn away. The flow saturation in this case is close to maximum.

Each mountain region has its own causes of mudflows. For example, in the Caucasus they occur mainly as a result of rains and downpours (85%).

In recent years, natural causes of mudflow formation have been supplemented by technogenic factors, violation of the rules and regulations of mining enterprises, explosions during the construction of roads and the construction of other structures, logging, improper conduct of agricultural work and violation of soil and vegetation cover.

When moving, a mudflow is a continuous stream of mud, stones and water. The steep leading front of a mudflow wave with a height of 5 to 15 m forms the “head” of a mudflow. The maximum height of the water-mud flow shaft sometimes reaches 25 m.

The classification of mudflows based on the causes of occurrence is given in Table. 2.4.

In Russia, up to 20% of the territory is located in mudflow zones. Mudflows are especially active in Kabardino-Balkaria, North Ossetia, Dagestan, in the Novorossiysk region, Sayano-Baikal region, in the area of ​​the Baikal-Amur Mainline, in Kamchatka within the Stanovoy and Verkhoyansk ranges. They also occur in some areas of Primorye, the Kola Peninsula and the Urals. Back in 1966, more than 5 thousand mudflow basins were registered on the territory of the USSR. Currently, their number has increased.

Table 2.4. Classification of mudflows based on the root causes of occurrence

Based on the main factors of occurrence mudflows are classified as follows: zonal manifestation - the main formation factor is climatic conditions (precipitation). They are zonal in nature. The convergence occurs systematically. The paths of movement are relatively constant; regional manifestation (the main formation factor is geological processes). The descent occurs episodically, and the paths of movement are not constant; anthropogenic - this is the result of human economic activity. Occur where there is the greatest load on the mountain landscape. New mudflow basins are formed. The gathering is episodic.

Classification by power (based on transferred solid mass):

1. Powerful (strong power), with the removal of more than 100 thousand m 3 of materials. Happens once every 5-10 years.
2. Medium power, with removal from 10 to 100 thousand m 3 of materials. Happens once every 2-3 years.
3. Weak power (low-power), with the removal of less than 10 thousand m 3 of materials. They happen every year, sometimes several times a year.

The classification of mudflow basins by the frequency of mudflows characterizes the intensity of development or its mudflow activity. Based on the frequency of mudflows, three groups of mudflow basins can be distinguished:

• high mudflow activity (with recurrence once every 3-5 years or more);
• average mudflow activity (with recurrence once every 6-15 years);
• low mudflow activity (with a frequency of once every 16 years or less).

Mudflows are also classified according to their impact on structures:

• Low-power - small erosion, partial blocking of openings in culverts.
• Medium power - severe erosion, complete blocking of holes, damage and demolition of foundationless buildings.
• Powerful - great destructive force, demolition of bridge trusses, destruction of bridge supports, stone buildings, roads.
• Catastrophic - complete destruction of buildings, sections of roads along with the road surface and structures, burial of structures under sediments.

Sometimes a classification of basins is used based on the height of the sources of mudflows:

• alpine. The sources lie above 2500 m, the volume of removal from 1 km 2 is 15-25 thousand m 3 per mudflow;
• mid-mountain. The sources lie within the range of 1000-2500 m, the volume of removal from 1 km 2 is 5-15 thousand m 3 per mudflow;
• low mountain. The sources lie below 1000 m, the volume of removal from 1 km 2 is less than 5 thousand m 3 per mudflow.

Landslides (mountain collapse)- detachment and catastrophic fall of large masses of rocks, their overturning, crushing and rolling down on steep and steep slopes.

Landslides of natural origin are observed in the mountains, on sea shores and cliffs of river valleys. They occur as a result of a weakening of the cohesion of rocks under the influence of weathering processes, erosion, dissolution and the action of gravity. The formation of landslides is facilitated by: the geological structure of the area, the presence of cracks and zones of crushing rocks on the slopes. Most often (up to 80%) modern collapses are associated with the anthropogenic factor. They are formed mainly during improper work, during construction and mining.

Landslides are characterized by the power of the landslide process (volume of falling rock masses) and the scale of manifestation (involvement of area in the process).

According to the power of the landslide process, landslides are divided into large (rock detachment of 10 million m3), medium (up to 10 million m3) and small (rock detachment of less than 10 million m3).

According to the scale of manifestation, landslides are divided into huge (100-200 ha), medium (50-100 ha), small (5-50 ha) and small (less than 5 ha).

In addition, landslides can be characterized by the type of collapse, which is determined by the steepness of the slope of the rockfall masses.

Landslides, mudflows, and avalanches cause great damage to the national economy, the natural environment, and lead to casualties.

The main damaging factors of landslides, mudflows and landslides are impacts from moving masses of rocks, as well as the collapse and flooding of previously free space by these masses. As a result, buildings and other structures are destroyed, settlements, economic facilities, agricultural and forest lands are hidden by rock layers, river beds and overpasses are blocked, people and animals die, and the landscape changes.

Landslides, mudflows and landslides on the territory of the Russian Federation occur in the mountainous regions of the North Caucasus, the Urals, Eastern Siberia, Primorye, Sakhalin Island, the Kuril Islands, the Kola Peninsula, as well as along the banks of large rivers.

Landslides often lead to large-scale catastrophic consequences. Thus, a landslide in Italy in 1963 with a volume of 240 million m3 covered 5 cities, killing 3 thousand people.

In 1982, a mudflow 6 km long and up to 200 m wide hit the villages of Shiveya and Arenda in the Chita region. As a result, houses, road bridges, 28 estates were destroyed, 500 hectares of cropland were washed away and covered, and people and farm animals also died. The economic damage from this mudflow amounted to about 250 thousand rubles.

In 1989, landslides in Checheno-Ing Ushetia caused damage to 2,518 houses, 44 schools, 4 kindergartens, 60 healthcare, cultural and public service facilities in 82 settlements.

Consequences of mudflows and landslides

Sel is a temporary flow of water that suddenly forms in the beds of mountain rivers with a large content of stones, sand and other solid materials. The cause of mudflows is intense and prolonged rainfall, rapid melting of snow or glaciers. Mudflows can also form from the collapse of large amounts of loose soil in river beds.

Unlike ordinary flows, mudflows, as a rule, do not move continuously, but in separate waves. At the same time, hundreds of tons, and sometimes millions of cubic meters of viscous mass are carried out. The sizes of individual boulders and fragments reach 3-4 m in diameter. When encountering obstacles, the mudflow passes through them, continuing to increase its energy.

Possessing a large mass and high speed of movement, up to 15 km/h, mudflows destroy buildings, roads, hydraulic engineering and other structures, disable communication and power lines, destroy gardens, flood arable land, and lead to the death of people and animals. All this lasts 1-3 hours. The time from the occurrence of a mudflow in the mountains to the moment it reaches the foothills is often calculated as 20-30 minutes.

To combat mudflows, they fix the surface of the earth by planting forests, expand the vegetation cover on mountain slopes, especially in places where mudflows originate, periodically drain water from mountain reservoirs, build anti-mudflow dams, dams and other protective structures.

Active snow melting is reduced by arranging smoke screens using smoke bombs. 15-20 minutes after the smoke, the temperature of the surface layer of air decreases, and the water flow is reduced by half.

The level of water accumulated in moraines (mountain lakes) and mudflow reservoirs is reduced using pumping units. In addition, in the fight against mudflows, such simple structures as cotton wool, ditches and terraces with a wide base are widely used. Protective and retaining walls, semi-dams and dams are built along river beds.

For the timely adoption of measures and the organization of reliable protection of the population, a clearly organized warning and warning system is of paramount importance. In areas threatened by mudflows, an anti-mudflow service is created. Its tasks include forecasting mudflows and informing the population about the time of its occurrence. In this case, a route is provided in advance along which the population is evacuated to higher places. There, if time permits, livestock is driven away and equipment is brought out.

If a person is captured by a moving mud flow, it is necessary to provide assistance to him by all available means. Such means may be poles, ropes or ropes. It is necessary to remove rescued people from the stream in the direction of the stream, gradually approaching its edge.

Landslide- sliding mixing of earth masses under the influence of its own weight - occurs most often along the banks of rivers and reservoirs and on mountain slopes. The volume of rocks displaced during landslides ranges from several hundred to many millions and even billions of cubic meters. Landslides are caused by various reasons: erosion of rocks by water, weakening of their strength due to weathering or waterlogging by precipitation and groundwater, unreasonable human economic activity, etc.

Landslides can destroy populated areas, destroy agricultural land, create danger during the operation of quarries and mining, damage communications, tunnels, pipelines, telephone and electrical networks, water management structures, mainly dams. In addition, they can block the dam, form a dam lake and contribute to flooding. Thus, the economic damage they cause can be significant.

The most effective protection against landslides is their prevention. A landslide does not usually start suddenly. First, cracks appear in the ground, ruptures in roads and coastal fortifications, buildings, structures, telegraph poles are displaced, and underground communications are destroyed. At the same time, it is very important to notice these first signs in time and make a correct forecast about the further development of the landslide. It should also be taken into account that landslides move at maximum speed only in the initial period, then it gradually decreases.

In landslide areas, constant monitoring of soil movement, water levels in wells, drainage structures, wastewater disposal systems, boreholes, rivers, reservoirs, precipitation and precipitation is organized. Such observation is organized especially carefully in the spring-autumn periods, when the most precipitation falls.

If a landslide occurs, it is necessary, firstly, to warn the population, and secondly, as the situation worsens, organize the evacuation of the population to safe areas.

In the event of destruction of buildings and structures as a result of a mudflow or landslide, rescue operations are carried out, victims are removed from the rubble, and people are helped to leave the danger zone.

Protection of the population in case of threat and during landslides, mudflows and landslides

The population living in landslide-, mudflow- and landslide-hazardous zones should know the sources, possible directions and characteristics of these dangerous phenomena. Based on the forecast data, residents and enterprises are provided with advance information about the danger regarding identified landslide, mudflow, landslide sources and possible zones of their action, about the periods of passage of mudflows, as well as about the procedure for submitting signals about the threat of these phenomena. This early awareness of potential disasters reduces the stress and panic that may later arise when communicating emergency information about the immediate threat of these events.

The population of these dangerous mountainous areas is obliged to take measures to strengthen houses and the territory on which they are built, as well as to participate in the construction of protective hydraulic and other engineering structures that protect against landslides and mudflows.

Primary information about the threat of landslides, mudflows and avalanches comes from landslide and mudflow stations, parties and hydrometeorological service posts. It is important that this information is communicated to the destination in a timely manner. Warning of the population about these natural disasters is carried out in the prescribed manner through sirens, radio and television, as well as through local warning systems that directly connect hydrometeorological service units with populated areas located in threatened zones.

If there is a threat of a landslide, mudflow or landslide, and if there is time, advance evacuation of the population, farm animals and property from threatening zones to safe places is organized.

Before leaving a house or apartment for early evacuation, they are brought into a state that helps to weaken the damaging factors of a natural disaster, prevents the occurrence of secondary factors and facilitates subsequent possible excavations and restoration. Therefore, moved property from the yard or balcony must be removed into the house; the most valuable property that cannot be taken with you must be protected from moisture and dirt. Doors, windows, ventilation and other openings are tightly closed. Electricity, gas, and water supply are turned off. Flammable and toxic substances are removed from the house and, if possible, buried in remote pits or separate cellars. In all other respects, citizens act in accordance with the procedure established for organized evacuation.

If there was no advance warning of the danger and residents were warned about the threat immediately before the onset of a natural disaster or noticed its approach themselves, each of them, without worrying about property, makes an emergency independent exit to a safe place. At the same time, relatives, neighbors, and all people encountered along the way should be warned about the danger. For an emergency exit, you need to know the routes to the nearest safe places. These paths are determined and communicated to the population based on the forecast of the most likely directions of arrival of a landslide (mudflow) to a given settlement (object). Natural safe measures for emergency exit are the slopes of mountains and hills that are not prone to landslide processes or between which there is a mudflow-hazardous direction. When climbing to safe slopes, valleys, gorges and recesses should not be used, as side channels of the main mudflow may form in them. On the way, assistance should be provided to the sick, elderly, disabled, children, and the weak. For transportation, whenever possible, personal transport, mobile agricultural machinery, riding and pack animals are used.

In the event that people, buildings and other structures find themselves on the surface of a moving landslide area, they should, after leaving the premises, move upward as much as possible and, depending on the situation, beware when braking the landslide of blocks, stones, fragments of structures, earthenware rolling down from its back part. shaft, scree. It can also take over the thrust of immovable rocks. At high speeds, a strong shock is possible when stopping the landslide. Everything poses a great danger to people in the landslide.

After the end of a landslide, mudflow or landslide, people who had previously hastily left the disaster zone and waited out it in a nearby safe place, making sure that there is no repeated threat, should return to this zone in order to search for and provide assistance to the victims.

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 the Ice Age and before the appearance of humans 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 exceptionally large size. 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 at the beginning of the 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 Nizhny Novgorod region. 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.