What are the disasters. Types and characteristics of natural disasters. Forest and peat fires

Natural disasters include:

geophysical emergencies (earthquakes, volcanic eruptions);

Emergencies of a geological nature (landslides, avalanches, mudflows);

Meteorological emergencies (hurricanes, cyclones, showers, tornadoes, snowfalls);

Hydrological emergencies (floods, a sharp decrease in groundwater levels (drought), tsunamis);

natural fires.

earthquakes

earthquake are called tremors and shifts in the earth's crust and upper mantle, transmitted over long distances in the form of elastic vibrations.

The main criteria of an earthquake are the depth of the source and the intensity of the energy output to the earth's surface.

An earthquake is a natural phenomenon associated with geological processes occurring in the Earth's lithosphere. An earthquake manifests itself in the form of tremors and vibrations of the earth's surface, resulting from sudden displacements and ruptures in the earth's crust or in the upper part of the mantle. These displacements and ruptures are due to deep processes occurring in the lithosphere and associated with the movement of lithospheric plates. In the mountain belts and near them, the intra-earth stress grows and grows until it exceeds the resistance of the rocks, as a result, the rocks break and they are displaced. Intraterrestrial tension drops abruptly. Potential strain energy is converted into kinetic energy, which is dissipated in different directions from the rupture site in the form of seismic waves. Seismic waves shake the earth.

The magnitude of an earthquake is a value that characterizes the energy released during an earthquake in the form of seismic waves.

Intensity is a qualitative characteristic of an earthquake and indicates the nature and scale of the impact of earthquakes on the earth's surface, on people, animals, as well as on natural and artificial structures in the earthquake area.

Accordingly, to assess earthquakes, there are two types of scales - magnitude scales and intensity scales.

Magnitude scales designed to assess the magnitude of an earthquake, i.e. energy released during an earthquake. These scales have no upper limit. The magnitude scales are the Richter scale and the Kanamori scale.

Richter scale. Charles Richter in 1935 proposed to estimate the strength of an earthquake (at its epicenter) the decimal logarithm of the displacement (in micrometers) of the needle of a standard Wood-Anderson seismograph located at a distance of no more than 600 km from the epicenter: M L= log A+f, where f is a correction function calculated from the table depending on the distance to the epicenter. The energy of an earthquake is roughly proportional to A 3 / 2 , that is, an increase in magnitude by 1.0 corresponds to an increase in the amplitude of oscillations by 10 times and an increase in energy by about 32 times.

The Richter scale and derivatives of the Richter scale do not work well for the largest earthquakes - at a magnitude of M ~ 8, the scale saturates.

Kanamori scale. In 1977, Kanamori proposed a fundamentally different estimate of the magnitude of earthquakes, based on the concept of seismic moment. The Kanamori scale agrees well with the Richter scale at magnitude 3< М < 7 и лучше подходит для оценки крупных землетрясений.

The magnitude characterizes an earthquake as an integral, global event and is not a measure of the intensity of an earthquake felt at a specific point on the surface of the Earth. The intensity of an earthquake, measured in points, not only strongly depends on the distance to the source; depending on the depth of the center and the type of rocks, the strength of earthquakes with the same magnitude can differ by 2-3 points.

Magnitude is a dimensionless quantity, it is not measured in points.

Correct use: « earthquake with magnitude 6.0», « earthquake measuring 5 magnitude on the Richter scale»

Misuse: « magnitude 6 earthquake», « earthquake measuring 6 on the Richter scale».

The strongest recorded earthquake occurred in Chile in 1960 - according to later estimates, the Kanamori magnitude was 9.5. It is believed that earthquakes on Earth cannot have a magnitude significantly higher than 9.5, since rocks cannot store more energy without breaking. Seismic events with higher energy can be caused by a meteorite impact.

Intensity scales

Several intensity scales are used in the world: in the USA - the Modified Mercalli scale (MM), in Russia and the CIS countries - MSK-64 (Medvedev-Sponheuer-Karnik scale), in Europe - the European macroseismic scale (EMS), in Japan - the Shindo scale (Shindo).

The 12-point Medvedev-Sponheuer-Karnik scale was developed in 1964 and became widespread in Europe and the USSR. Since 1996, the more modern European Macroseismic Scale (EMS) has been used in the countries of the European Union. MSK-64 is the basis of SNiP II-7-81 "Construction in seismic areas" and continues to be used in Russia and the CIS countries.

Earthquake characteristics according to the MSK-64 scale

score	The strength of the earthquake	A brief description of
	Not felt.	It is noted only by seismic instruments.
	Very weak kicks	marked by seismic instruments. It is felt only by individuals who are in a state of complete rest in the upper floors of buildings, and by very sensitive pets.
		Only felt inside some buildings, like a jolt from a truck.
	Moderate	It is recognized by the slight rattling and vibration of objects, dishes and window panes, the creaking of doors and walls. Inside a building, shaking is felt by most people.
	Pretty strong	In the open air it is felt by many, inside the houses - by everyone. General shaking of the building, furniture swaying. The pendulums of the clock stop. Cracks in window panes and plaster. The awakening of the sleepers. It is felt by people outside buildings, thin branches of trees sway. Doors slam.
		Felt by everyone. Many run out into the street in fear. Pictures fall from the walls. Separate pieces of plaster break off.
	Very strong	Damage (cracks) in the walls of stone houses. Anti-seismic, as well as wooden and wicker buildings remain unscathed.
	destructive	Cracks on steep slopes and on damp soil. Monuments move or topple over. Houses are badly damaged.
	devastating	Severe damage and destruction of stone houses. Old wooden houses are crooked.
	Destroying	Cracks in the soil are sometimes up to a meter wide. Landslides and landslides from the slopes. Destruction of stone buildings. Curvature of railroad tracks.
	Catastrophe	Wide cracks in the surface layers of the earth. Numerous landslides and collapses. Stone houses are almost completely destroyed. Severe bending and buckling of railway rails.
	Strong disaster	Changes in the soil reach enormous proportions. Numerous cracks, collapses, landslides. The emergence of waterfalls, ponding on lakes, deviation of the flow of rivers. None of the buildings survive.

Detection and registration of all types of seismic waves is carried out using a special measuring device - a seismograph. In most cases, a seismograph has a load with a spring attachment, which remains stationary during an earthquake, while the rest of the instrument (body, support) moves and shifts relative to the load.

Harbingers, signs of an approaching earthquake there may be the following phenomena: deformation of the earth's surface, changes in the regime and composition of groundwater and gases, unusual behavior of animals, the faint glow of switched off fluorescent lamps, sparking of closely spaced (but not touching) electrical wires, lightning, the smell of gas in areas where it was not previously noted.

Flashes of lightning, the glow of fluorescent lamps and the sparking of wires are associated with the disturbance of the geoelectric field over the future epicenter of the earthquake. Such optical phenomena were observed before some large earthquakes.

Tsunami

Tsunamis are waves of great length, resulting from a powerful impact on the entire water column.

In most cases, the source of tsunamis are earthquakes occurring under the ocean floor or near its coast. However, tsunamis occur only after those earthquakes that are associated with the rapid formation of faults, collapses and landslides at the bottom of the ocean. Fault is a rapid displacement of blocks of bottom rocks of the earth's crust.

In Russia, the eastern coast of Kamchatka and the Kuril Islands, Sakhalin Island and the Pacific coast are most affected by tsunamis. Having a high speed of movement and a huge mass of water, a tsunami has tremendous destructive power. Running into oncoming coastal obstacles, the wave brings down all its energy on them, rising above them as a huge water wall, crushes, destroys and destroys everything that comes in its way.

The height of the waves formed by the wind is usually no more than 4 - 6 m, the largest is about 30 m. The length of the wind waves is 100 - 250 m, extremely rarely - up to 500 m.

In the open Ocean, the wavelength of a tsunami is measured in hundreds of kilometers (200 - 300) at a height of about 1 m. Therefore, in the open Ocean, they are usually invisible to ships. Tsunami waves propagate in all directions from the place of origin at a speed of 700 - 800 km / h. Near the coast, the tsunami speed decreases, and the height increases (up to 30 m and more).

floods

Flood- this is a temporary flooding of a significant part of the land, causing significant material damage, leading to the death of plants, animals, people.

When a flood occurs, the water rises rapidly and the surrounding area is flooded. The consequences of this are: damage to buildings, structures and communications; disruption of agricultural activities and loss of crops; landscape change; death of people, domestic and wild animals; loss of material and cultural values; flushing and flooding of fertile soils.

Flood types:

1. Floods caused by snowmelt (high water), heavy rains (floods).

2. Storm surge floods - surge floods.

3. Floods caused by traffic jams in sections of rivers (usually mountainous), ice dams (accumulation of intra-water ice in the river before freeze-up). These are congestion and zazhorny floods.

4. Floods caused by the destruction of hydraulic structures.

5. Floods caused by tsunamis.

Flooding called the penetration of water into the basements of buildings through the sewer network (when the sewer is connected to the river), through ditches and trenches, and also due to significant groundwater backwater.

Flooding- this is a covering of the surrounding area with a layer of water flooding courtyards, streets of settlements and the lower floors of buildings.

According to the Ministry of Emergency Situations of Russia, floods in terms of frequency, distribution area, and total average annual damage rank first in Russia among known natural disasters. In terms of the number of human victims, they rank second after earthquakes.

On the territory of Russia, floods threaten almost 40 cities and several thousand other settlements. The frequency of floods on average ranges from once every 5-10 years to once every 15-20 years. But there are cities where floods are observed once every 2-3 years (Ufa, Orsk, Kursk and a number of others).

Hurricanes, storms and tornadoes

Hurricane(on the sea - typhoon) - this is a wind of great destructive power. Speed ​​over 35 m/s (130 km/h). Lasts from several hours to several days.

Hurricane wind damages strong and demolishes light buildings, breaks wires of power lines, breaks and uproots trees. People caught in the hurricane zone may die or be injured of varying severity.

Long-term meteorological observations show that the wind speed during hurricanes reached 30–50 m/s in most regions of the European part of Russia, and 60–90 m/s or more in the Far East.

The destructive power of a hurricane lies in the combined action of wind and water: the propelling action of the high-speed wind pressure, powerful waves that crash on the coast, catastrophic downpours and floods.

Storm- this is a strong wind, the speed of which is less than the speed of a hurricane, it reaches 15 - 20 m / s. (Note that a short-term wind increase to a speed of 20 - 30 m / s is called a squall.)

The main indicator that determines the destructive effect of these natural disasters is the velocity pressure of air masses. The kinetic energy contained in the moving air determines its velocity head and destructive force.

The Beaufort scale is used to determine the strength of the wind at the Earth's surface.

Francis Beaufort (1774 - 1857), an English military hydrographer and cartographer, rear admiral, in 1806 proposed to estimate the strength of the wind by its effect on ground objects and by the waves of the sea; for this, he developed a conditional 12-point scale.

Tornado is an atmospheric vortex that arises in a thundercloud and propagates downward, often to the very surface of the Earth. Movement in a tornado counterclockwise. Diameter from several meters to several tens of meters. The rotation speed reaches 100 - 200 m/s. The average travel speed is 50 - 60 km / h. The duration of existence is from several minutes to several hours.

A tornado is sometimes called a thrombus (provided it passes over land), a typhoon (over the sea), and in North America it is called a tornado.

The total length of a tornado's path can be hundreds of meters and reach hundreds of kilometers. The average width of the destruction zone is 300-500 m.

The destruction produced by the tornado is due to the high velocity pressure of air rotating inside the funnel with a large pressure difference between the periphery and the inside of the funnel due to the huge centrifugal force.

On the territory of Russia, tornadoes most often occur in the central regions, the Volga region, in the Urals, in Siberia, on the coasts and in the waters of the Black, Azov, Caspian and Baltic Seas.

The most dangerous areas in terms of the risk of tornadoes are the Black Sea coast and the Central Economic Region, including the Moscow region.

natural fires

Natural fires:

steppe;

Underground.

Forest fires: top and bottom.

Horse fire. With strong winds, the propagation speed is up to 50 km / day. The crown fire does not go down, it spreads through the tops of the trees.

Ground fire is a solid fire. The propagation speed is 3-4 km / day. The undergrowth burns out completely.

underground fires can occur in layers of peat or coal. Peat fires are typical for Russia. Peat burns without access to oxygen - this is the danger. Peat fires can only be localized.

steppe fire dangerous by the rapid combustion of the upper sod layer of the soil. The speed depends on the wind speed and ranges from 5 to 20 km/day. Accompanied by strong smoke.

The consequences of natural fires are: destruction of trees and vegetation by fire; violation of planned forest management and use of forest resources; destruction by fire of residential and public buildings in settlements; destruction of communication and power transmission line supports, elements of pipeline transport; damage to people, domestic and wild animals; disruption of human economic activity in large areas.

sat down

sel (from Arabic - a stormy stream) is a temporary mud-stone stream that suddenly forms in the beds of mountain rivers. This mixture of water, mud, stones weighing up to 10 tons, trees and other objects rushes at a speed of up to 15 km / h, sweeping away, flooding or carrying away bridges, buildings, destroying dams, dams, flooding villages. The duration of mudflows reaches 10 hours with a wave height of up to 15 m. Mudflows are formed as a result of prolonged downpours, intense melting of snow (glaciers), dam breaks, illiterate blasting, earthquakes, volcanic eruptions.

The main areas of manifestation of mudflows in Russia are in Transbaikalia (the frequency of powerful mudflows is 6 ... 12 years), in the BAM zone (once every 20 years), in the Far East and the Urals, in the Caucasus.

In most cases, the population about the danger of a mudflow can be warned in just tens of minutes and less often in 1-2 hours or more. The approach of such a stream can be heard by the characteristic sound of boulders and stone fragments rolling and colliding with each other, resembling the roar of a train approaching at high speed.

In case of notification of the population about an approaching mudflow or a landslide that has begun, as well as at the first signs of their manifestation, it is necessary to leave the premises as soon as possible, warn others about the danger, and go to a safe place. When leaving the premises, turn off the stoves, turn off the gas taps, turn off the lights and electrical appliances. This will help prevent fires.

Mudflows and landslides pose a serious danger when they appear suddenly. In this case, the worst thing is panic. In case of capture of someone by a moving stream of mudflow, it is necessary to provide assistance to the victim by all available means. Such means may be poles, ropes or ropes supplied to the rescued. It is necessary to take the rescued out of the stream in the direction of the stream with a gradual approach to its edge, otherwise the stones of the rushing stream will cripple the rescued. During landslides, it is possible for people to fall under the ground, to strike and injure them with falling objects, building structures, and trees. In these cases, it is necessary to quickly provide assistance to the victims, if necessary, give them artificial respiration.

Landslides- detachment and sliding displacement of the upper layers of the soil along the slope under the influence of gravity. Most often, landslides occur due to an increase in the steepness of the slopes of mountains, river valleys, high shores of the seas, lakes, reservoirs and rivers when they are washed away by water.

The initial sign of landslide movements that have begun is the appearance of cracks in buildings, gaps in roads, coastal fortifications and embankments, bulging of the earth, displacement of the base of various high-rise structures and even trees in the lower part relative to the upper one.

Anti-landslide measures, in which the population should take part, are the diversion of surface water, tree planting, the installation of various supporting engineering structures, the excavation of trenches in order to drain the soil of the landslide massif, the unloading and leveling of the landslide slope. In addition, the population living in landslide hazardous areas should not allow abundant leakage of water from taps, damaged water pipes or standpipes; it is necessary to arrange drainage drains in a timely manner in case of accumulation of surface water (with the formation of puddles).

collapse- detachment and fall of masses of rocks down from the slopes of mountains under the influence of gravity. Landslides occur on the slopes of river banks and valleys, in the mountains, on the shores of the seas. Earthquakes are the main cause of large collapses.

Rockfall- the collapse of stones in the mountains.

Avalanche- fast, sudden movement of snow and (or) ice down the steep slopes of mountains.

The main damaging factors of landslides, mudflows, landslides and snow avalanches are: impacts of moving masses of rocks; blockage or flooding by moving masses of rocks of a certain space.

Consequences of landslides, mudflows, landslides and snow avalanches: death of people and animals; blocking river channels and changing the landscape; destruction of buildings and structures; concealment by rock masses of settlements, objects of the national economy, agricultural and forest lands.

Snowfalls, snowdrifts

With the announcement of a storm warning - about possible snow drifts - it is necessary to limit movement, especially in rural areas, to create at home the necessary supply of food, water and fuel. In some areas, with the onset of the winter period, it is necessary to stretch ropes along the streets, between houses, helping pedestrians navigate in a strong snowstorm and overcome strong winds. Snowdrifts are especially dangerous for people caught on the way far from human habitation. Snow-covered roads, loss of visibility cause complete disorientation on the ground.

When driving a car, you should not try to overcome snow drifts, you must stop, completely close the blinds of the car, cover the engine from the side of the radiator. If possible, install the car with the engine downwind. Periodically, you need to get out of the car, shovel the snow so as not to be buried under it. In addition, a car not covered with snow is a good guide for the search party. The car engine must be periodically warmed up to avoid its “defrosting”. When warming up the car, it is important to prevent exhaust gases from flowing into the cab (body, interior), for this purpose, it is necessary to ensure that the exhaust pipe does not fill up with snow.

If there are several people on the road (in several cars), it is advisable to get everyone together and use one car as a shelter; water must be drained from the engines of other vehicles. In no case should you leave the shelter - the car. In a heavy snowfall (blizzard), landmarks that seem reliable at first glance can be lost after a few tens of meters.

Under natural disasters understand natural phenomena that cause an emergency situation, characterized by a sudden disruption of the normal life of large groups of the population, a threat to life

people and destruction of property.

Natural disasters can occur both independently of each other and in interconnection, one of them can lead to another. Regardless of the source of natural disasters, they are characterized by significant scale and varying duration - from a few minutes and seconds (earthquakes, snow avalanches) to several hours (mudflows), days (later) and months (floods).

Natural disasters include:

· geological and geophysical phenomena (earthquakes, landslides, mudflows, subsidence of the earth's surface);

· hydrological and hydrogeological phenomena (floods, floods);

Meteorological phenomena:

a) aerodynamic (hurricanes, storms, storms, tornadoes, cyclones, etc.);

b) agrometeorological (hail, rain, frost, drought);

c) natural fires (forest, steppe, peat, etc.);

space (falling meteorites, comet remnants).

earthquakes- these are strong fluctuations of the earth's crust caused by tectonic or volcanic causes and leading to the destruction of buildings, structures, fires and human casualties.

The main characteristics of earthquakes are: the depth of the focus, magnitude and intensity of energy on the earth's surface.

The depth of the earthquake source is usually in the range from 10 to 30 km, in some cases it can be much greater.

The magnitude characterizes the total energy of an earthquake. The Richter magnitude varies from 0 to 9 (the strongest earthquake). Increasing it by one means a tenfold increase in the amplitude of vibrations in the soil (or soil displacement) and an increase in the earthquake energy by a factor of 30.

The intensity of energy on the surface of the earth is measured in points. It depends on the depth of the source, magnitude, distance from the epicenter, the geological structure of soils, and other factors. To measure the intensity of earthquake energy in our country, a 12-point Richter scale is adopted.

Earthquakes cause great material damage and claim thousands of human lives. They also cause other natural disasters, such as landslides, avalanches, mudflows, tsunamis, floods (due to dam failure), fires (in case of damage to oil storage facilities and rupture of gas pipelines), damage to communications, power-water supply and sewage lines, accidents at chemical enterprises with the expiration (spill) of SDYAV, as well as at nuclear power plants with a leak (emission) of radioactive substances into the atmosphere, etc.

Currently, there are no sufficiently reliable methods for predicting earthquakes and their consequences. However, by changing the characteristic properties of the earth, as well as the unusual behavior of living organisms before an earthquake (they are called precursors), scientists often manage to make predictions. The harbingers of earthquakes are: a rapid increase in the frequency of weak shocks (fortok); deformation of the earth's crust, determined by observation from satellites from space or shooting on the earth's surface using laser light sources: a change in the ratio of the propagation velocities of longitudinal and transverse waves on the eve of an earthquake; change in the electrical resistance of rocks, the level of groundwater in wells, the content of radon in water, etc.

The unusual behavior of animals on the eve of the earthquake is expressed in the fact that, for example, cats leave the villages and carry kittens to the meadows, and birds in cages in 10-15 minutes. before the earthquake begin to fly; before the shock, unusual cries of birds are heard; pets in barns panic, etc. The most likely reason for this behavior of animals is anomalies in the electromagnetic field before the earthquake.

To protect against earthquakes, seismically dangerous zones are identified in advance in various regions of the country, i.e. the so-called seismic zoning. Seismic zoning maps usually highlight areas that are threatened by earthquakes with an intensity higher than 7-8 on the Richter scale. In seismically hazardous areas, various protection measures are provided, starting with strict compliance with the requirements of norms and rules during the construction of reconstructions of buildings, structures and other facilities to the suspension of hazardous industries (chemical plants, nuclear power plants, etc.).

Landslides- these are sliding displacements of rock masses down the slope, arising from an imbalance caused by various reasons (washing out of rocks with water, weakening of their strength due to weathering or waterlogging by precipitation and groundwater, systematic shocks, unreasonable human economic activity, etc.).

Landslides can occur on slopes with a steepness of 20º or more and at any time of the year. It differs not only in the rate of rock displacement, but also in its scale. The speed of slow displacements of rocks is several tens of centimeters per year, medium displacements are several meters per hour or a day, and fast displacements are tens of kilometers per hour. Rapid displacements include landslides-flows, when solid material mixes with water, as well as snow and snow-rock avalanches. The volume of rocks displaced during landslides ranges from several hundred to many millions and even billions of cubic meters.

Landslides can destroy settlements, destroy agricultural land, pose a danger to the operation of quarries and mining, damage communications, tunnels, pipelines, telephone and electrical networks, water facilities, mainly dams. In addition, they can block valleys, form dammed lakes, and contribute to floods. Thus, the economic damage they cause can be very significant. The most effective protection against landslides is their prevention. From the complex of preventive measures, it should be noted the collection and diversion of surface water, the artificial transformation of the relief, the fixation of slopes with the help of piles and the construction of retaining walls.

snow avalanches also often referred to as landslides. They occur in the same way as other landslide displacements. The adhesion forces of snow cross a certain boundary and gravity causes the displacement of snow masses along the slope. An avalanche is a mixture of snow and air crystals. Large avalanches occur on slopes of 25-60º. Smooth grassy slopes are the most prone to avalanches. Bushes, large rocks and other obstacles keep avalanches at bay.

Snow avalanches cause enormous material damage and are often accompanied by loss of life. So, on July 13, 1990, on Lenin Peak in the Pamirs, as a result of an earthquake and a large snow avalanche, a climbers' camp was demolished at an altitude of 5300 m. 40 people died. There has never been such a tragedy in the history of Russian mountaineering.

Avalanche protection can be passive or active. With passive protection, the use of avalanche-prone slopes is avoided or barrage shields are placed on them. With active protection, avalanche-prone slopes are shelled, causing the descent of small non-hazardous avalanches, and thus preventing the accumulation of critical masses of snow.

sat down- these are floods with a very high concentration of mineral particles, stones and rock fragments (from 10-15 to 75% of the flow volume), arising in the basins of small mountain rivers and dry ravines and caused, as a rule, by heavy rainfall, less often by intense snowmelt, as well as a breakthrough of moraine and dammed lakes, a collapse, a landslide, an earthquake.

The danger of mudflows is not only in their destructive power, but also in the suddenness of their appearance. The consequences of mudflows are catastrophic.

Ways to deal with mudflows are very diverse. This is the construction of various dams to delay solid runoff and pass a mixture of water and fine fractions of rocks, cascades of dams to destroy the mudflow and release it from solid material, retaining walls to strengthen slopes, etc.

floods- these are significant flooding of the area as a result of a rise in the water level in a river, lake, reservoir, caused by various reasons (spring snowmelt, heavy rainfall and rainfall, ice jams on rivers, breakthrough of dams, dammed lakes and enclosing dams, wind surge of water, etc. .P.). Floods cause enormous material damage and lead to human casualties.

Direct material damage from floods consists in damage and destruction of residential and industrial buildings, roads and railways, power lines and communications, land reclamation systems, death of livestock and crops, damage and destruction of raw materials, fuel, food, feed, fertilizers, etc. .P.

Floods can be accompanied by fires due to breaks and short circuits of electrical cables and wires, as well as ruptures of water and sewer pipes, electrical, television and telegraph cables located in the ground, due to the subsequent uneven settlement of the soil.

The main direction of flood control is to reduce the maximum flow of water in the river by redistributing the runoff over time (planting shelterbelts, plowing the land across the slopes, preserving coastal water protection belts of vegetation, terracing slopes, etc.).

A certain effect is also given by the arrangement of ponds, sumps and other containers in logs, gullies and ravines to intercept melt and rain water. For medium and large rivers, the only radical remedy is the regulation of flood flow with the help of reservoirs.

In addition, a well-known method is widely used for flood protection - the construction of dams. To eliminate the risk of blockage formation, certain sections of the riverbed are straightened, cleared and deepened, as well as ice is destroyed by explosions 10-15 days before it is opened.

Hurricanes- these are winds with a force of 12 on the Beaufort scale, i.e. winds exceeding 32.6 m/s (117.3 km/h). Also called hurricanes tropical cyclones arising in the Pacific Ocean off the coast of Central America; in the Far East and in the regions of the Indian Ocean, hurricanes (cyclones) are called typhoons , in Japan - a tsunami. During tropical cyclones, wind speeds often exceed 50 m/s. Cyclones and typhoons are usually accompanied by heavy rain showers.

A hurricane on land destroys buildings, communication and power lines, damages transport communications and bridges, breaks and uproots trees; when propagating over the sea, it causes huge waves with a height of 10-12 m or more, damages or even leads to the death of the vessel.

Hurricanes and storm winds (their speed on the Beaufort scale is from 20.8 to 32.6 m/s) in winter can lift huge masses of snow into the air and cause snowstorms, which leads to drifts, stoppage of road and rail transport, disruption of water systems. -, gas, electricity and communications.

Modern methods of weather forecasting allow several hours or even days to warn the population of cities or entire coastal areas about an impending hurricane (storm), and civil defense services (GO) and ministries of emergency situations (MES) can provide the necessary information about the possible situation and required actions in the prevailing conditions.

Over the billions of years of existence of our planet, certain mechanisms have been formed on it by which nature works. Many of these mechanisms are subtle and harmless, while others are large-scale and bring great destruction with them. In this rating, we will talk about the 11 most destructive natural disasters on our planet, some of which can destroy thousands of people and an entire city in a few minutes.

11

A mudflow is a mud or mud-stone stream that suddenly forms in the beds of mountain rivers as a result of heavy rains, rapid melting of glaciers or seasonal snow cover. Deforestation in mountainous areas can be a decisive factor in the occurrence - the roots of trees hold the upper part of the soil, which prevents the occurrence of a mudflow. This phenomenon is short-term and usually lasts from 1 to 3 hours, typical for small streams up to 25-30 kilometers long. On their way, the streams cut deep channels, which are usually dry or contain small streams. The consequences of mudflows are catastrophic.

Imagine that a mass of earth, silt, stones, snow, sand, driven by a strong stream of water, fell on the city from the side of the mountains. This stream will be demolished at the foot of the city buildings along with people, and orchards. All this stream will break into the city, turn its streets into raging rivers with steep banks of destroyed houses. Houses break off their foundations and along with people they are carried away by a stormy stream.

10

A landslide is the sliding of masses of rocks down a slope under the influence of gravity, often while maintaining their connectedness and solidity. Landslides occur on the slopes of valleys or river banks, in the mountains, on the shores of the seas, the most grandiose at the bottom of the seas. The displacement of large masses of earth or rock along a slope is caused in most cases by wetting the soil with rainwater so that the mass of soil becomes heavy and more mobile. Such large landslides harm agricultural land, enterprises, and settlements. To combat landslides, bank protection structures and planting of vegetation are used.

Only fast landslides, the speed of which is several tens of kilometers, can cause real natural disasters with hundreds of casualties, when there is no time for evacuation. Imagine that huge pieces of soil are quickly moving down from the mountain directly onto a village or city, and buildings are destroyed under tons of this earth and people who have not had time to leave the place of the landslide are dying.

9

A sandstorm is an atmospheric phenomenon in the form of the transport of large amounts of dust, soil particles and grains of sand by wind several meters from the ground with a noticeable deterioration in horizontal visibility. At the same time, dust and sand rise into the air and at the same time dust settles over a large area. Depending on the color of the soil in a given region, distant objects take on a grayish, yellowish, or reddish hue. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.

Most often, these catastrophic phenomena occur in the desert. A sure sign that a sandstorm is about to begin is a sudden silence. Rustles and sounds disappear with the wind. The desert literally freezes. A small cloud appears on the horizon, which quickly grows and turns into a black-purple cloud. The lost wind rises and very quickly reaches speeds of up to 150-200 km / h. A sandstorm can cover streets within a radius of several kilometers with sand and dust, but the main danger of sandstorms is wind and poor visibility, which causes car accidents in which dozens of people are injured, and some even die.

8

An avalanche is a mass of snow that falls or slides off a mountain slope. Snow avalanches pose a considerable danger, causing casualties among climbers, lovers of mountain skiing and snowboarding and causing significant damage to property. Sometimes snow avalanches have catastrophic consequences, destroying entire villages and causing the death of dozens of people. Snow avalanches, to one degree or another, are common in all mountainous regions. In winter, they are the main natural danger of the mountains.

Tones of snow are held on the tops of the mountains due to the force of friction. Large avalanches descend at the moment when the pressure force of the snow mass begins to exceed the force of friction. An avalanche is usually triggered by climatic causes: a sudden change in weather, rain, heavy snowfalls, as well as mechanical effects on the snow mass, including the impact of rockfalls, earthquakes, etc. Sometimes an avalanche can start due to a slight push like a gunshot or pressure on the snow of a man. The volume of snow in an avalanche can reach up to several million cubic meters. However, even avalanches with a volume of about 5 m³ can be life-threatening.

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A volcanic eruption is the process of ejection by a volcano onto the earth's surface of incandescent fragments, ash, an outpouring of magma, which, having poured onto the surface, becomes lava. The strongest volcanic eruption can have a time period from several hours to many years. Incandescent clouds of ash and gases capable of moving at speeds of hundreds of kilometers per hour and rising hundreds of meters into the air. The volcano ejects gases, liquids and solids with high temperature. This often causes the destruction of buildings and the death of people. Lava and other red-hot eruptive substances flow down the slopes of the mountain and burn out everything they meet on their way, bringing innumerable victims and material losses that stagger the imagination. The only protection against volcanoes is a general evacuation, so the population must be familiar with the evacuation plan and unquestioningly obey the authorities if necessary.

It is worth noting that the danger from a volcanic eruption exists not only for the region around the mountain. Potentially, volcanoes threaten the life of all life on Earth, so you should not treat these hot guys with condescension. Almost all manifestations of volcanic activity are dangerous. It goes without saying that the danger of boiling lava is understandable. But no less terrible is the ash that literally penetrates everywhere in the form of a continuous gray-black snowfall that fills up streets, ponds, entire cities. Geophysicists claim to be capable of eruptions hundreds of times more powerful than have ever been observed. The largest volcanic eruptions, however, have already occurred on Earth - long before the advent of civilization.

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A tornado or tornado is an atmospheric vortex that occurs in a thundercloud and spreads down, often to the very surface of the earth, in the form of a cloud sleeve or trunk with a diameter of tens and hundreds of meters. Typically, the diameter of a tornado funnel on the ground is 300-400 meters, but if a tornado originated on the surface of the water, this value can be only 20-30 meters, and when the funnel passes over land, it can reach 1-3 kilometers. The largest number of tornadoes is recorded on the North American continent, especially in the central states of the United States. Every year, about a thousand tornadoes occur in the United States. The strongest tornado can last up to an hour or more. But most of them exist for no more than ten minutes.

On average, about 60 people die each year from tornadoes, mostly from flying or falling debris. However, it happens that huge tornadoes rush at a speed of about 100 kilometers per hour, destroying all buildings in their path. The maximum recorded wind speed in the largest tornado is about 500 kilometers per hour. During such tornadoes, the death toll can go into the hundreds, and the victims into the thousands, not to mention the material damage. The reasons for the formation of tornadoes have not been fully studied so far.

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A hurricane or tropical cyclone is a type of low-pressure weather system that occurs over a warm sea surface and is accompanied by severe thunderstorms, heavy rainfall, and gale-force winds. The term "tropical" refers to both the geographical area and the formation of these cyclones in tropical air masses. It is generally accepted, according to the Beaufort scale, that a storm turns into a hurricane at a wind speed of more than 117 km / h. The strongest hurricanes can cause not only extreme downpours, but also large waves on the surface of the sea, storm surges and tornadoes. Tropical cyclones can form and maintain their strength only over the surface of large bodies of water, while over land they quickly lose strength.

A hurricane can cause downpours, tornadoes, small tsunamis and floods. A direct effect of tropical cyclones on land is storm winds that can destroy buildings, bridges, and other man-made structures. The strongest permanent winds within the cyclone exceed 70 meters per second. The worst effect of tropical cyclones in terms of casualties has historically been storm surge, that is, the rise in sea level due to the action of the cyclone, which on average results in about 90% of casualties. Over the past two centuries, tropical cyclones have killed 1.9 million people worldwide. In addition to the direct effect on residential buildings and economic facilities, tropical cyclones destroy infrastructure, including roads, bridges, power lines, causing enormous economic damage to the affected areas.

The most destructive and terrible hurricane in the history of the United States - Katrina, occurred at the end of August 2005. The most severe damage was caused to New Orleans in Louisiana, where about 80% of the city's area was under water. As a result of the natural disaster, 1,836 residents were killed and the economic damage amounted to $125 billion.

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Flooding - flooding of the area as a result of rising water levels in rivers, lakes, seas due to rain, rapid snowmelt, wind surge of water on the coast and other causes, which damages people's health and even leads to their death, and also causes material damage . For example, in mid-January 2009 there was the largest flood in Brazil. More than 60 cities were affected then. About 13 thousand people left their homes, more than 800 people died. Floods and numerous landslides are caused by heavy rains.

Heavy monsoon rains have continued in Southeast Asia since mid-July 2001, causing landslides and flooding in the Mekong River region. As a result, Thailand experienced the worst floods in over half a century. Streams of water flooded villages, ancient temples, farms and factories. At least 280 people have died in Thailand, and another 200 in neighboring Cambodia. About 8.2 million people in 60 of Thailand's 77 provinces were affected by the floods, and economic losses are currently estimated to exceed $2 billion.

Drought is a long period of stable weather with high air temperatures and low rainfall, resulting in a decrease in soil moisture reserves and oppression and death of crops. The onset of a severe drought is usually associated with the establishment of an inactive high anticyclone. The abundance of solar heat and gradually decreasing air humidity create increased evaporation, and therefore soil moisture reserves are depleted without being replenished by rains. Gradually, as soil drought intensifies, ponds, rivers, lakes, springs dry up, and a hydrological drought begins.

For example, in Thailand, almost every year, severe floods alternate with severe droughts, when a state of emergency is declared in dozens of provinces, and several million people somehow feel the effects of the drought. As for the victims of this natural phenomenon, only in Africa from 1970 to 2010 the death toll from droughts is 1 million people.

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Tsunamis are long waves generated by a powerful impact on the entire water column in the ocean or other body of water. Most tsunamis are caused by underwater earthquakes, during which there is a sharp displacement of the seabed. Tsunamis are formed during an earthquake of any magnitude, but those that arise due to strong earthquakes with a magnitude of more than 7 on the Richter scale reach a large force. As a result of an earthquake, several waves propagate. More than 80% of tsunamis occur on the periphery of the Pacific Ocean. The first scientific description of the phenomenon was given by Jose de Acosta in 1586 in Lima, Peru, after a powerful earthquake, then a strong tsunami 25 meters high burst onto land at a distance of 10 km.

The largest tsunamis in the world occurred in 2004 and 2011. So, on December 26, 2004 at 00:58 there was a powerful earthquake with a magnitude of 9.3 - the second most powerful of all recorded, which caused the deadliest of all known tsunamis. The tsunami affected the countries of Asia and African Somalia. The total number of deaths exceeded 235 thousand people. The second tsunami happened on March 11, 2011 in Japan after a strong earthquake of magnitude 9.0 with an epicenter caused a tsunami with a wave height exceeding 40 meters. In addition, the earthquake and the ensuing tsunami caused the Fukushima I nuclear accident. injured.

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An earthquake is the tremors and vibrations of the Earth's surface caused by natural causes. Small shocks can also be caused by the rise of lava during volcanic eruptions. About a million earthquakes occur every year all over the Earth, but most of them are so small that they go unnoticed. The most powerful earthquakes, capable of causing widespread destruction, occur on the planet about once every two weeks. Most of them fall on the bottom of the oceans, and therefore are not accompanied by catastrophic consequences if the earthquake does without a tsunami.

Earthquakes are best known for the devastation they can cause. The destruction of buildings and structures is caused by ground vibrations or giant tidal waves (tsunamis) that occur during seismic displacements on the seabed. A powerful earthquake begins with the rupture and movement of rocks in some place deep in the Earth. This place is called the earthquake focus or hypocenter. Its depth is usually no more than 100 km, but sometimes it reaches up to 700 km. Sometimes the focus of an earthquake can be near the surface of the Earth. In such cases, if the earthquake is strong, bridges, roads, houses and other structures are torn and destroyed.

The largest natural disaster is considered to be an earthquake of magnitude 8.2 on July 28, 1976 in the Chinese city of Tangshan, Hebei province. According to official figures from the PRC authorities, the death toll was 242,419 people, however, according to some estimates, the death toll reaches 800,000 people. At 3:42 local time, the city was destroyed by a strong earthquake. Destruction also took place in Tianjin and in Beijing, located just 140 km to the west. As a result of the earthquake, about 5.3 million houses were destroyed or damaged so much that it was impossible to live in them. Several aftershocks, the strongest of which had a magnitude of 7.1, led to even more casualties. The Tangshan earthquake is the second largest earthquake in history after the most devastating Shaanxi earthquake in 1556. Then about 830 thousand people died.

During the tsunami that devastated the coasts of nine Asian countries in December 2004, against the background of enormous human losses (300 thousand people died), very few animals were affected. How can this be explained? The hypotheses are many. The interest of both the public and scientists is enormous. And this is despite the fact that the pre-emptive reaction of living beings to an impending natural disaster has been noticed by people for a very long time.

The first documented example has a solid age - it refers to the year 2000 BC. It says that on the island of Crete, before the strongest earthquake, weasels left human settlements.

In China, catastrophe has long been foreshadowed by the appearance of snake balls on the surface of the earth. This sign was guided by the Chinese seers when in November 1920 they predicted a strong earthquake. Despite the fact that many knew about the tragedy in advance, the number of human casualties was still significant. The force of the tremors was 8.6 on the Richter scale.

Already after the first earthquake, the fragile dwellings of the Chinese were swept off the face of the earth. In one minute, 10 ancient cities disappeared. More than 180,000 people died that day. Another 20,000 people died later from the cold, as all the houses were destroyed and there was nowhere for people to hide from the frost. The situation caused by a strong earthquake was complicated by the ensuing landslide.

History repeated itself in 1975, when China experienced the strongest Hainan earthquake with an amplitude of 7.3 points. On the eve of the disaster, snakes again crawled out of their holes to the surface of the soil, which looked very strange in winter conditions, because it was winter outside, that is, the time when reptiles are supposed to be in deep hibernation. This phenomenon was accompanied by a number of minor underground vibrations. During January 1975, reports of strange animal behavior increased. Now even the cattle refused to go to the stalls. And then an unprecedented decision was made to evacuate the city of Hainan, which in February of the same year was completely wiped off the face of the earth by a catastrophic eight-magnitude earthquake.

In the history of seismology, this is practically the only earthquake that was predicted in advance and saved the lives of 400,000 citizens. The uniqueness of this forecast lies in the fact that it was made on the basis of observations of bioprecursors.

Japanese scientists observing the behavior of crocodiles in a nursery on the island of Honshu noted that before a strong earthquake in the middle part of the island, which occurred on December 17, 1987, crocodiles unexpectedly staged a real "concert". Dozens of individuals growled anxiously and, bending in an arc, performed an intricate dance.

It is quite difficult to study the behavior of animals before an earthquake in order to understand the reasons for the described behavior: large earthquakes are quite rare, and seismologists predict them with varying success. However, in one case, luck still smiled at the researchers. We are talking about the earthquake in L'Aquila (Italy), which occurred in 2009. Shortly before this, the local toads, one and all, left the reservoirs. This led scientists to the idea that before an earthquake, the composition of groundwater and soil water changes, which, first of all, can be felt by those who live in holes and in water.

Scientists explain this phenomenon in this way. An earthquake has a certain period of preparation, during which the layers of the earth's rock can experience deformation, collapse due to increasing pressure, etc. This is not yet a full-fledged earthquake, but the destruction and deformation of rocks lead to the release of certain chemically active substances. Once released, they react with the air and cause the appearance of positively charged ions in it. These ions themselves can affect the state of living organisms.

If scientists have figured out the behavior of reptiles, then the situation is more complicated with the premonition of a catastrophe by other animals. After the Spitak earthquake in Armenia, which occurred in 1988, the story of the laika Alisa and her owner Gharibyan from Leninakan became widely known. On the morning of December 7, two hours before the earthquake, the owner took the dog out for a walk, but Alice refused to return to the house, howling terribly and barking. The frightened owner called the police, the city council, the radio, and everywhere he was ridiculed. Just in case, Gharibyan decided to take his family out of the house and offered to do the same to the neighbors. And not in vain, since it was at this time that the elements hit the city.

In general, the history of the 20th century shows that animals are able to foresee not only earthquakes and tsunamis. There are cases when animals left the valleys, anticipating an avalanche, and during the Second World War, when death could fall from the sky at any moment, cats often saved their owners. A black-and-white cat named Sally, who lived near the London docks, developed a sophisticated warning system that got her owner and neighbors into a bomb shelter before the bombs started to fall. Sensing that the raid was close, Sally ran to the counter in the hall where the gas mask hung, and began to beat him persistently with her front paws, after which she returned to her mistress and began to scratch her. Then she rushed into the yard and began to scratch at the door of the bomb shelter. Once, when the mistress entered the shelter, Sally jumped over the fence, ran into the yard to the neighbors and began to meow loudly, attracting their attention. It wasn't until everyone was inside the bomb shelter that Sally relaxed, curled up in a ball, and fell asleep peacefully.

Here are some more examples of the amazing "geosensitivity" of our smaller brothers.

After the events of December 2004, a lighthouse keeper in South India described how, hours before the tsunami, an entire herd of antelope fled in panic from the coast to the nearby hills. Anticipating the tsunami, in Thailand, elephants screamed, broke their chains and ran away to higher ground, flamingos left the lowlands where they traditionally live and eat, and flew away to higher ground. A few hours before the tsunami in the Malaysian zoo, all the animals behaved very strangely, most of them huddled in their homes and refused to come out. In Sri Lanka, more than 30 thousand people died during the tsunami, while almost all elephants, deer and other wild animals survived. Of the 2,000 inhabitants of one of the Indian reserves during the tsunami in December 2004, only one wild boar died.

American biologists testify that 12 hours before the arrival of Hurricane Charley in Florida, 14 sharks, which had been monitored for several years, left their habitat, which they had never left in their lives, into deeper waters and returned only through two weeks after the danger had passed. A similar shark reaction was observed prior to Storm Gabrielle.

What do animals know that we don't? The 2004 tsunami made us think about this issue more seriously. Studies have shown that a variety of animal species around the world have the ability to anticipate natural disasters.

“Wild animals are able to perceive much more information about the environment than humans. They hear perfectly, pick up dangerous vibrations at a great distance and feel the most insignificant changes in atmospheric pressure. The main ability of animals is the ability to "read" nature's warnings, which helps them to go to safe places in time, emphasizes biologist Dr. Mike Highthouse. “It is impossible to learn, but knowing about the habits of animals, the ability to correctly interpret their behavior, could bring people a lot of benefits.”

Is it possible for us, ordinary citizens, to predict a possible approaching earthquake at home? It turns out you can. For example, ordinary aquarium fish - macrognatus three to four hours before an earthquake line up in a vertical chain. They can also rush around the aquarium and even try to jump out of it. The day before the earthquake, another aquarium fish begins to behave restlessly - neon. In particular, the teachers of the Almaty eco-center "Best", noticing the unusual behavior of the macrognatus, 20 minutes before the shock in Almaty at 4.5 points (the epicenter of Kyrgyzstan) took the children outside.

There are cases when many animals save their owners at the household level. For example, a Cocker named Jersey grabbed his master's trousers when he was heading to a friend to fly on his private jet. Usually the quietest dog whined and growled menacingly. And when the owner was still about to leave, he bit him on the leg and disrupted the event, which caused the serious anger of the whole family. The next morning it became known that a friend crashed on a plane, crashing into a rock.

And in a nursing home in the US state of Rhode Island, there lives a cat who can smell death. The rare gift of a cat named Oscar was described in his book by Professor of Brown University in the USA David Dosa. The cat very rarely makes mistakes and sometimes even predicts the onset of death better than the doctors themselves. Oscar is no different from other cats living in the hospital, except for one unusual property. He rarely spends time with patients, except for those who are about to die. If he is not allowed into the ward where the dying person is, he begins to scratch the door and ask to see him.

In a word, scientists have something to think about ...

“Interesting paper. The world of the unknown "No. 14 2012