Almost all ancient peoples believed that terrible cataclysms hit our planet, which destroyed all life on the planet. In our time, with the advent of the twenty-first century, every day natural disasters claim millions of lives. Maybe these are the harbingers of a global catastrophe that is coming upon us with all the power and strength?

Be that as it may, our nature has four elements that rage more and more every year.

Throughout the earth, there are more than five hundred volcanoes. The largest fiery belt covers the coasts of the Pacific Ocean. It is worth noting that 328 of them have already erupted with terrible force in those days that our ancestors can remember.

Everyone knows from an early age that it is fires that can cause the economy of our country and the earth as a whole, the greatest destruction and sad consequences. At the same time, it does not matter at all in which area a fire breaks out, because it can take the lives of people. According to the World Health Organization, every year thousands of people die, if not in the fires themselves, then from the acrid smoke that is released from fires in peat bogs. The acrid smoke that spreads along the roads can also cause fatal car accidents.

Earth

Every year across the planet, tectonic plates shift. These vibrations and shocks can in turn turn out to be very strong earthquakes that can completely destroy any city in a matter of seconds. Every two weeks on the planet, there is one very strong earthquake. And it's good if it does not affect people's lives.

Despite the mind of man, he simply cannot compete with the power and tremendous force of nature. Every year, all over the Earth, various landslides and avalanches occur. This terrible phenomenon can completely demolish everything in its path that it meets. Even a concrete structure will not become an obstacle to him. But the worst thing is that all this power with the debris will be eliminated on people.

This is the worst nightmare of all people who live on the coast of the oceans. Earthquakes can provoke the formation of huge waves that will rapidly demolish everything in its path. Their speed can reach fifteen thousand kilometers, and the destructive force is capable of destroying any structure.

Flood

The stream of rising water is swift, it can leave even the largest city under its thickness. This most often happens after heavy rains.

Everyone loves the warm rays of the sun that awaken the world from hibernation. But its excessive interaction with nature can completely destroy the crop, or cause severe drought, which will subsequently provoke fires.

Typhoon or hurricane

The air currents of the earth constantly meet each other. And in those frequent moments when a warm and cold cyclone meets, a strong wind flow can form. Its speed can reach several thousand kilometers. He is able to uproot trees and carry away houses. The air moves along a certain trajectory, which starts at the corners of the spiral, and rapidly moves towards its center. It is at this point that the most terrible destruction and irreparable consequences occur.

Tornado or tornado

This is a kind of air funnel, which literally draws into itself everything that can be torn off the ground. His strength is so great that he is able to circle the largest objects in himself. Cars and houses can fall into it, and literally shatter to pieces.

Due to constant changes in climate, the whole cycle can change. Thus, in countries where winter has never come, it can snow.

An avalanche is a huge mass of snow that periodically falls in the form of landslides and avalanches from steep ridges and slopes of high snowy mountains. Avalanches usually move along the weathering ruts existing on the slopes of the mountains, and in the place where their movement stops, in river valleys and at the foot of the mountains, they deposit snow piles, known as avalanche cones.

In addition to occasional glaciers and hail avalanches, periodic winter and spring avalanches are distinguished. Winter avalanches occur due to the fact that freshly fallen loose snow, leaning on the icy surface of old snow, slides over it and rolls down in masses on steep slopes from insignificant causes, often from a shot, a scream, a gust of wind, etc.

The gusts of wind caused by the rapid movement of the snow mass are so strong that they break trees, rip off roofs and even destroy buildings. Spring avalanches are caused by melting water breaking the bond between soil and snow cover. The snow mass on steeper slopes breaks off and rolls down, capturing in its movement stones, trees and buildings encountered on the way, which is accompanied by a strong rumble and crackling.

The place from which such an avalanche rolled down is in the form of a bare black clearing, and where the avalanche stops moving, an avalanche cone is formed, which has a loose surface at first. In Switzerland, avalanches are a common occurrence and have been the subject of repeated observations. The mass of snow delivered by individual avalanches sometimes reaches 1 million or even more m³.

Avalanches, except for the Alps, were observed in the Himalayan mountains, Tien Shan, in the Caucasus, in Scandinavia, where avalanches breaking down from mountain peaks sometimes they reach fiords, in the Cordillera and other mountains.

Sel (from the Arabic "sail" - "stormy stream") is a water, stone or mud stream that occurs in the mountains when rivers overflow, snow melts or after a large amount of precipitation. Similar conditions are typical for most mountainous regions.

According to the composition of the mudflow mass, mudflows are divided into mud-stone, mud, water-stone and water-dressing, and according to physical types - disconnected and connected. In non-cohesive mudflows, the transport medium for solid inclusions is water, and in coherent mudflows, a water-ground mixture. Mudflows move along the slopes at a speed of up to 10 m/s or more, and the mass volume reaches hundreds of thousands, and sometimes millions of cubic meters, and the mass is 100-200 tons.

Mudflows sweep away everything in their path: they destroy roads, buildings, etc. To combat mudflows on the most dangerous slopes, special structures are installed and a vegetation cover is created that holds the soil layer on the mountain slopes.

In ancient times, the inhabitants of the Earth could not find the true cause of this event, therefore, they associated the volcanic eruption with the disfavor of the gods. Eruptions often caused the death of entire cities. So, at the very beginning of our era, during the eruption of Mount Vesuvius, one of the greatest cities of the Roman Empire, Pompeii, was wiped off the face of the earth. The ancient Romans called the god of fire a volcano.

Volcanic eruption is often preceded by an earthquake. In time, in addition to lava, hot stones, gases, water vapor, and ash fly out of the crater, the height of which can reach 5 km. But the greatest danger to people is precisely the eruption of lava, which melts even stones and destroys all life in its path. During one eruption, up to several km³ of lava is ejected from the volcano. But a volcanic eruption is not always accompanied by a lava flow. Volcanoes can be dormant for many years, and the eruption lasts from several days to several months.

Volcanoes are divided into active and extinct. Active volcanoes are those whose last eruption is known. Some volcanoes last erupted so long ago that no one remembers it. Such volcanoes are called extinct. Volcanoes that erupt every few thousand years are called potentially active. If in total there are about 4 thousand volcanoes on Earth, of which 1340 are potentially active.

In the earth's crust, which is under the cover of the sea or ocean, the same processes take place as on the mainland. Lithospheric plates collide, causing tremors in the earth's crust. There are active volcanoes at the bottom of the seas and oceans. It is as a result of underwater earthquakes and volcanic eruptions that huge waves are formed, which are called tsunamis. This word, translated from Japanese, means "giant wave in the harbor."

As a result of the shaking of the ocean floor, a huge column of water sets in motion. The farther from the epicenter of the earthquake the wave moves, the higher it becomes. As the wave approaches land, the lower layers of water hit the bottom, further increasing the power of the tsunami.

The height of a tsunami is usually 10-30 meters. When such a huge mass of water, moving at speeds up to 800 km/h, hits the shore, nothing living is able to survive. The wave sweeps away everything in its path, after which it picks up fragments of destroyed objects and throws them deep into the island or mainland. Usually, the first won is followed by several more (from 3 to 10). Waves 3 and 4 are usually the strongest.

One of the most destructive tsunamis hit the Commander Islands in 1737. According to experts, the wave height was more than 50 meters. Only a tsunami of such power could throw so far on the island the inhabitants of the ocean, whose remains were found by scientists.

Another major tsunami occurred in 1883 after the eruption of the Krakatau volcano. Because of this, a small uninhabited island, on which Krakatoa was located, fell into the water to a depth of 200 meters. The wave that reached the islands of Java and Sumatra reached 40 meters in height. As a result of this tsunami, about 35 thousand people died.

Tsunamis do not always have such dire consequences. Sometimes giant waves do not reach the shores of continents or islands inhabited by people and go almost unnoticed. In the open ocean, before the collision with the coast, the height of the tsunami does not exceed one meter, so for ships far from the coast it does not

An earthquake is a strong vibration of the earth's surface caused by processes occurring in the lithosphere. Most earthquakes occur in the vicinity of high mountains, as these areas still continue to form and Earth's crust especially mobile here.

Earthquakes are of several types: tectonic, volcanic and landslide. Tectonic earthquakes occur when mountain plates are displaced or as a result of collisions between oceanic and continental platforms. During such collisions, mountains or depressions are formed and the surface oscillates.

Volcanic earthquakes occur when flows of hot lava and gases press down on the surface of the Earth. Volcanic earthquakes are usually not too strong, but can last up to several weeks. In addition, volcanic earthquakes are usually the forerunners of a volcanic eruption, which threatens with more serious consequences.

Landslide earthquakes are associated with the formation of underground voids that occur under the influence of ground water or underground rivers. At the same time, the top layer of the earth's surface collapses down, causing small shaking.

The place where an earthquake occurs (collision of plates) is called its source or hypocenter. The area of ​​the earth's surface where an earthquake occurs is called the epicenter. It is here that the most severe destruction occurs.

The strength of earthquakes is determined on a ten-point Richter scale, depending on the amplitude of the wave that occurs during the vibration of the surface. The larger the amplitude, the stronger the earthquake. The weakest earthquakes (1-4 points on the Richter scale) are recorded only by special sensitive instruments and do not cause damage. Sometimes they manifest themselves in the form of glass trembling or moving objects, and sometimes they are completely invisible. Earthquakes of 5-7 on the Richter scale cause minor damage, and stronger ones can cause complete destruction of buildings.

Seismologists study earthquakes. According to them, about 500,000 earthquakes occur on our planet every year. different strength. About 100 thousand of them are felt by people, and 1000 cause damage.

Floods are one of the most common natural disasters. They make up 19% of the total number of natural disasters. Flooding is the flooding of land that occurs as a result of a strong rise in the water level in a river, lake or sea (spill), due to the melting of snow or ice, as well as heavy and prolonged rains.

Depending on the cause of the flood, they are divided into 5 types:

High water - a flood that occurs as a result of melting snow and the release of a reservoir from its natural banks

Flood - a flood associated with heavy rains

Flooding caused by large accumulations of ice that clog the riverbed and prevent water from flowing downstream

Floods due to strong wind, which drives water in one direction, most often against the current

Floods resulting from a dam or reservoir failure.

Floods and floods occur every year wherever there are full-flowing rivers and lakes. They are usually expected, flood a relatively small area and do not lead to the death of a large number of people, although they cause destruction. If these types of floods are accompanied by heavy rains, then a much larger area is already flooded. Usually, as a result of such floods, only small buildings are destroyed without a reinforced foundation, communication and power supply are disrupted. The main inconvenience is the flooding of the lower floors of buildings and roads, as a result of which the inhabitants of the flooded areas remain cut off from land.

In some areas where floods are most frequent, houses are even raised on special piles. Floods resulting from the destruction of dams have a great destructive power, especially since they occur unexpectedly.

One of the most severe floods occurred in 2000 in Australia. Heavy rain did not stop there for two weeks, as a result of which 12 rivers immediately overflowed their banks and flooded an area of ​​200 thousand km².

To prevent floods and their consequences during the floods, the ice on the rivers is blown up, breaking it into small ice floes that do not prevent the flow of water. If a large amount of snow falls during the winter, which threatens with a strong flood of the river, residents from dangerous areas are evacuated in advance.

Hurricane and tornado are atmospheric vortices. However, these two natural phenomena are formed and manifest themselves in different ways. A hurricane is accompanied by a strong wind, and a tornado occurs in thunderclouds and is an air funnel that sweeps away everything in its path.

The speed of a hurricane wind on Earth is 200 km/h near the earth. This is one of the most destructive phenomena of nature: passing over the surface of the earth, it uproots trees, rips off the roofs of houses, and brings down the supports of power lines and communications. A hurricane can exist for several days, weakening and then gaining strength again. The danger of a hurricane is assessed on a special five-point scale, which was adopted in the last century. The degree of danger depends on the speed of the wind and on the destruction that the hurricane produces. But terrestrial hurricanes are far from the strongest. On the giant planets (Jupiter, Saturn, Uranus, Neptune), hurricane wind speeds reach 2000 km/h.

A tornado is formed when moving unevenly heated layers of air. It spreads in the form of a dark sleeve towards the land (funnel). The height of the funnel can reach 1500 meters. The funnel of the tornado twists from the bottom up counterclockwise, sucking in everything that is next to it. It is because of the dust and water captured from the ground that the tornado acquires dark color and becomes visible from afar.

The speed of the tornado can reach 20 m/s, and the diameter can be up to several hundred meters. Its strength allows uprooted trees, cars and even small buildings to be lifted into the air. A tornado can occur not only over land, but also over the water surface.

The height of a spinning air column can reach a kilometer and even one and a half kilometers, it moves at a speed of 10-20 m / s. Its diameter can be from 10 meters (if the tornado passes over the ocean) to several hundred meters (if it passes over the ground). Often a tornado is accompanied by a thunderstorm, rain or even hail. It exists much less than a hurricane (only 1.5-2 hours) and is able to travel only 40-60 km.
The most frequent and strong tornadoes originate on the west coast of America. Americans even assign human names to the largest natural disasters (Katrina, Denis). A tornado in America is called a tornado.

Today, the attention of the whole world is drawn to Chile, where a large-scale eruption of the Calbuco volcano began. The time has come to remember 7 biggest natural disasters recent years to know what the future may hold. Nature steps on people, as people used to step on nature.

Calbuco volcano eruption. Chile

Mount Calbuco in Chile is a fairly active volcano. However, its last eruption took place more than forty years ago - in 1972, and even then it lasted only one hour. But on April 22, 2015, everything changed for the worse. Calbuco literally exploded, starting the ejection of volcanic ash to a height of several kilometers.

On the Internet you can find a huge number of videos about this amazingly beautiful sight. However, it is pleasant to enjoy the view only through a computer, being thousands of kilometers from the scene. In reality, being near Calbuco is scary and deadly.

The Chilean government decided to resettle all people within a radius of 20 kilometers from the volcano. And this is only the first step. It is not yet known how long the eruption will last and what real damage it will bring. But it will definitely be a sum of several billion dollars.

Earthquake in Haiti

On January 12, 2010, Haiti suffered a catastrophe of unprecedented proportions. There were several tremors, the main of which had a magnitude of 7. As a result, almost the entire country was in ruins. Even the presidential palace, one of the most majestic and capital buildings in Haiti, was destroyed.

According to official figures, more than 222,000 people died during and after the earthquake, and 311,000 were injured to varying degrees. At the same time, millions of Haitians were left homeless.

This is not to say that magnitude 7 is something unprecedented in the history of seismic observations. The scale of destruction turned out to be so huge due to the high deterioration of the infrastructure in Haiti, and also because of the extremely low quality of absolutely all buildings. In addition, the local population itself was in no hurry to provide first aid to the victims, as well as to participate in the removal of rubble and the restoration of the country.

As a result, an international military contingent was sent to Haiti, which took over the government in the first time after the earthquake, when the traditional authorities were paralyzed and extremely corrupt.

Tsunami in the Pacific Ocean

Until December 26, 2004, the vast majority of the inhabitants of the Earth knew about the tsunami exclusively from textbooks and disaster films. However, that day will forever remain in the memory of Mankind because of the huge wave that covered the coast of dozens of states in the Indian Ocean.

It all started with a major earthquake with a magnitude of 9.1-9.3 that occurred just north of the island of Sumatra. It caused a giant wave up to 15 meters high, which spread in all directions of the ocean and meaning from the face of the Earth hundreds of settlements, as well as world-famous seaside resorts.

The tsunami covered coastal areas in Indonesia, India, Sri Lanka, Australia, Myanmar, South Africa, Madagascar, Kenya, Maldives, Seychelles, Oman and other states on the coast indian ocean. Statisticians counted more than 300 thousand dead in this disaster. At the same time, the bodies of many could not be found - the wave carried them into the open ocean.

The consequences of this disaster are enormous. In many places infrastructure was never fully restored after the 2004 tsunami.

Eyjafjallajökull volcano eruption

The hard-to-pronounce Icelandic name Eyjafjallajokull became one of the most popular words in 2010. And all thanks to the volcanic eruption in the mountain range with this name.

Paradoxically, not a single person died during this eruption. But this natural disaster seriously disrupted business life throughout the world, primarily in Europe. After all, a huge amount of volcanic ash thrown into the sky from the Eyjafjallajökull vent completely paralyzed air traffic in the Old World. The natural disaster destabilized the lives of millions of people in Europe itself, as well as in North America.

Thousands of flights, both passenger and cargo, were cancelled. The daily losses of airlines during that period amounted to more than $200 million.

Earthquake in China's Sichuan province

As in the case of the earthquake in Haiti, a huge number of victims after a similar disaster in the Chinese province of Sichuan, which occurred there on May 12, 2008, is due to the low level of capital buildings.

As a result of the main earthquake of magnitude 8, as well as smaller concussions that followed it, more than 69,000 people died in Sichuan, 18,000 were missing, and 288,000 were injured.

At the same time, the government of the People's Republic of China severely limited international assistance in the disaster zone, it tried to solve the problem with my own hands. According to experts, the Chinese thus wanted to hide the real extent of what happened.

For publishing real data about the dead and destruction, as well as for articles about corruption, which led to such huge numbers of losses, the PRC authorities even imprisoned the most famous contemporary Chinese artist, Ai Weiwei, for several months.

Hurricane Katrina

However, the scale of the consequences of a natural disaster does not always directly depend on the quality of construction in a particular region, as well as on the presence or absence of corruption there. An example of this is Hurricane Katrina, which hit the Southeast coast of the United States in the Gulf of Mexico in late August 2005.

The main impact of Hurricane Katrina fell on the city of New Orleans and the state of Louisiana. The rising water level in several places broke through the dam protecting New Orleans, and about 80 percent of the city was under water. At that moment, entire areas were destroyed, infrastructure facilities, transport interchanges and communications were destroyed.

The population who refused or did not have time to evacuate fled on the roofs of houses. The famous Superdom stadium became the main gathering place for people. But it turned into a trap at the same time, because it was already impossible to get out of it.

During the hurricane, 1,836 people died and more than a million were made homeless. The damage from this natural disaster is estimated at 125 billion dollars. At the same time, New Orleans has not been able to return to a full-fledged normal life in ten years - the city's population is still about a third less than in 2005.

March 11, 2011 in the Pacific Ocean east of the island of Honshu, shocks with a magnitude of 9-9.1 occurred, which led to the appearance of a huge tsunami wave up to 7 meters high. She hit Japan, washing away many coastal objects and going deep into the tens of kilometers.

In different parts of Japan, after the earthquake and tsunami, fires broke out, infrastructure, including industrial ones, was destroyed. In total, almost 16 thousand people died as a result of this disaster, and economic losses amounted to about 309 billion dollars.

But this turned out to be not the worst. The world knows about the 2011 disaster in Japan, primarily because of the accident at the Fukushima nuclear power plant, which occurred as a result of the collapse of a tsunami wave on it.

More than four years have passed since this accident, but the operation at the nuclear power plant is still ongoing. And the settlements closest to it were permanently settled. So Japan got its own.

A large-scale natural disaster is one of the options for the death of our Civilization. We have collected .

Every year, various human activities and natural phenomena cause disasters. environment and economic losses around the world. But beyond the dark side, there is something admirable about the destructive power of nature.

This article will present you the most interesting natural phenomena and cataclysms that happened in 2011 and 2012, and at the same time remained not very well known to the public.

10. Sea smoke on the Black Sea, Romania.

Sea smoke is the evaporation of sea water, which is formed when the air is cold enough and the water is heated by the sun. Because of the temperature difference, the water begins to evaporate.

it beautiful photo was made a few months ago in Romania by Dan Mihailescu.

9. Strange sounds coming from the frozen Black Sea, Ukraine.

If you've ever wondered what a frozen sea sounds like, here's the answer! Reminds me of scratching wood with nails.

The video was filmed on the coast of Odessa in Ukraine.

8. Trees in the web, Pakistan.

Unexpected side effect of the great flood that flooded one-fifth of the land of Pakistan is that millions of spiders, escaping from the water, climbed trees and formed cocoons and huge webs of cobwebs there.

7. Fire tornado - Brazil.

A rare phenomenon called "fire tornado" was caught on camera in Aracatuba, Brazil. A deadly cocktail of high temperatures, strong winds and fires formed a whirlwind of fire.

6. Cappuccino Coast, UK.

In December 2011, the seaside resort of Cleveleys, Lancashire was covered in cappuccino-colored sea foam (first photo). The second and third photos were taken in Cape Town, South Africa.

According to experts, sea foam is formed from molecules of fat and proteins created as a result of the decomposition of tiny sea creatures (Phaeocystis).

5. Snow in the desert, Namibia.

As you know, the Namibian Desert is the oldest desert on earth, and it would seem that, apart from sand and eternal heat, there can be nothing unusual here. However, judging by the statistics, it snows here almost every ten years.

The last time this happened was in June 2011, when snow fell between 11 am and 12 noon. On this day, the most low temperature in Namibia -7 degrees Celsius.

4. Huge whirlpool, Japan.

An incredibly large whirlpool formed off the east coast of Japan after the sensational tsunami last year. Whirlpools are common in tsunamis, but such large ones are rare.

3. Waterspouts, Australia.

In May 2011, four tornado-like tornadoes formed off the coast of Australia, one of which reached a height of 600 meters.

Waterspouts usually start as tornadoes - above the ground, and then move to a body of water. Their size in height starts from a few meters, and the width varies up to a hundred meters.

It is noteworthy that local residents in this region have not seen such phenomena for more than 45 years.

2. Massive sandstorms, USA.

This incredible video shows the huge sandstorm that engulfed Phoenix in 2011. The cloud of dust grew up to 50 km wide and reached 3 km in height.

Sandstorms are a common meteorological event in Arizona, but researchers and locals unanimously declared that this storm was the largest in the history of the state.

1. Volcanic ash from Lake Nahuel Huapi - Argentina.

The massive eruption of the Puyehue volcano - near the city of Osorno, in southern Chile, has created an incredible spectacle in Argentina.

Northeast winds blew some of the ash onto Lake Nahuel Huapi. And its surface was covered with a thick layer of volcanic debris, which is very abrasive and does not dissolve in water.

By the way, Nahuel Huapi is the deepest and cleanest lake in Argentina. The lake stretches for 100 km along the Chilean border.

The depth reaches 400 meters, and its area is 529 square meters. km.

Disaster- a catastrophic natural phenomenon (or process) that can cause numerous casualties, significant material damage and other severe consequences.

Natural disasters- these are dangerous natural processes or phenomena that are not amenable to human influence, which are the result of the action of the forces of nature. Natural disasters are catastrophic situations that usually occur suddenly, leading to disruption of the daily way of life of large groups of people, often accompanied by loss of life and destruction of property.

Natural disasters include earthquakes, volcanic eruptions, mudflows, landslides, landslides, floods, droughts, cyclones, hurricanes, tornadoes, snowdrifts and avalanches, prolonged heavy rains, severe persistent frosts, extensive forest and peat fires. Epidemics, epizootics, epiphytoties, and the mass spread of pests in forestry and agriculture are also classified as natural disasters.

Natural disasters can be caused by:

rapid movement of matter (earthquakes, landslides);

release of intraterrestrial energy (volcanic activity, earthquakes);

rising water levels in rivers, lakes and seas (floods, tsunamis);

exposure to unusually strong winds (hurricanes, tornadoes, cyclones);

Some natural disasters (fires, landslides, landslides) can be caused by human activities, but more often natural disasters are the root cause of natural disasters.

The consequences of natural disasters are very severe. The greatest harm is caused by floods (40% of the total damage), hurricanes (20%), earthquakes and droughts (15% each), 10% of the total damage falls on other types of natural disasters.

Regardless of the source of occurrence, natural disasters are characterized by significant scale and varying duration - from a few seconds and minutes (earthquakes, avalanches) to several hours (mudflows), days (landslides) and months (floods).

earthquakes- the most dangerous and destructive natural disasters. The area of ​​occurrence of an underground shock is the focus of an earthquake, within which the process of releasing the accumulated energy takes place. In the center of the focus, a point is conventionally distinguished, called the hypocenter. The projection of this point on the earth's surface is called the epicenter. During an earthquake, elastic seismic waves, longitudinal and transverse, propagate in all directions from the hypocenter. On the surface of the earth in all directions from the epicenter, surface seismic waves diverge. As a rule, they cover vast territories. The integrity of the soil is often violated, buildings and structures are destroyed, water supply, sewerage, communication lines, electricity and gas supply fail, there are casualties. This is one of the most devastating natural disasters. According to UNESCO, earthquakes are ranked first in terms of economic damage and loss of life. They arise unexpectedly, and although the duration of the main shock does not exceed a few seconds, their consequences are tragic.

Some earthquakes were accompanied by destructive waves that devastated the coast - tsunami. Now it is an accepted international scientific term, it comes from the Japanese word, which means "a large wave that floods the bay." The exact definition of a tsunami sounds like this - these are long waves of a catastrophic nature, arising mainly as a result of tectonic movements on the ocean floor. Tsunami waves are so long that they are not perceived as waves: their length is from 150 to 300 km. In the open sea, tsunamis are not very noticeable: their height is several tens of centimeters or a maximum of several meters. Having reached the shallow shelf, the wave becomes higher, rises and turns into a moving wall. Entering shallow bays or funnel-shaped mouths of rivers, the wave becomes even higher. At the same time, it slows down and, like a giant shaft, rolls onto land. The speed of the tsunami is the higher, the greater the depth of the ocean. The speed of most tsunami waves fluctuates between 400 and 500 km/h, but there were cases when they reached 1000 km/h. Tsunamis are most often caused by underwater earthquakes. Volcanic eruptions can serve as another source.

Flood- temporary flooding of a significant part of the land with water as a result of the actions of the forces of nature. Floods can be caused by:

heavy precipitation or intense melting of snow (glaciers), combined action of flood waters and ice jams; surge wind; underwater earthquakes. Floods can be predicted: determine the time, nature, expected size and timely organize preventive measures that significantly reduce damage, create favorable conditions for rescue and urgent emergency recovery work. Land can be flooded by rivers or by the sea - this is how river and sea floods differ. Floods threaten almost 3/4 of the earth's surface. According to UNESCO statistics, about 200,000 people died from river floods in 1947-1967. According to some hydrologists, this figure is even underestimated. Secondary damage from floods is even greater than from other natural disasters. These are destroyed settlements, drowned cattle, mud-covered lands. As a result of heavy rains that took place in Transbaikalia in early July 1990, floods unprecedented in these places arose. More than 400 bridges have been demolished. According to the data of the Regional Emergency Flood Commission, the national economy of the Chita Region has been damaged in the amount of 400 million rubles. Thousands of people were left homeless. There were no human casualties either. Floods can be accompanied by fires due to cliffs and short circuit electric cables and wires, as well as breaks in water and sewer pipes, electric, television and telegraph cables located in the ground, due to the subsequent uneven settlement of the soil.

Mudflows and landslides. Mudflow is a temporary stream that suddenly forms in the channels of mountain rivers, characterized by a sharp rise in the water level and a high content of solid material in it. It occurs as a result of intense and prolonged showers, rapid melting of glaciers or snow cover, and the collapse of a large amount of loose clastic material into the channel. Having a large mass and speed of movement, mudflows destroy buildings, structures, roads and everything else in the path of movement. Mudflows within the basin can be local, general and structural. The first ones arise in the channels of tributaries of rivers and large beams, the second ones pass along the main channel of the river. The danger of mudflows is not only in their destructive power, but also in the suddenness of their appearance. Mudflows affect approximately 10% of the territory of our country. In total, about 6,000 mudflows have been registered, of which more than half are in Central Asia and Kazakhstan. According to the composition of the transported solid material, mudflows can be mudflows (a mixture of water with fine earth at a low concentration of stones), mudflows (a mixture of water, pebbles, gravel, small stones) and waterstones (a mixture of water with predominantly large stones). The mudflow flow velocity is usually 2.5-4.0 m/s, but when the blockage breaks, it can reach 8-10 m/s or more.

Hurricanes- these are winds with a force of 12 on the Beaufort scale, i.e. winds whose speed exceeds 32.6 m / s (117.3 km / h). Tropical cyclones that occur in the Pacific Ocean off the coast of Central America are also called hurricanes; on the Far East and in areas of the Indian Ocean hurricanes ( cyclones) are called typhoons. 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 ship.

Tornado- these are catastrophic atmospheric vortices having the shape of a funnel with a diameter of 10 to 1 km. In this vortex, the wind speed can reach an incredible value - 300 m / s (which is more than 1000 km / h). Such a speed cannot be measured by any instruments, it is estimated experimentally and by the degree of impact of a tornado. For example, it was noted that during a tornado, a chip stuck into a pine trunk. This corresponds to wind speeds above 200 m/s. The origin of a tornado is not completely understood. Obviously, they are formed at moments of unstable air stratification, when the heating of the earth's surface leads to heating of the lower layer of air as well. Above this layer there is a layer of colder air, this situation is unstable. Warm air rushes up, while cold air in a whirlwind, like a trunk, descends down to the earth's surface. Often this occurs over small, elevated areas within flat terrain.

dust storms- these are atmospheric perturbations, in which a huge amount of dust and sand rises into the air, transferred over considerable distances. Compared to earthquakes or tropical cyclones, dust storms are not, in fact, such catastrophic phenomena, but their impact can be very unpleasant, and sometimes fatal.

fires- the spontaneous spread of burning, manifested in the destructive effect of fire that has gone out of human control. Fires occur, as a rule, when fire safety measures are violated, as a result of lightning discharges, spontaneous combustion and other causes.

Forest fires - uncontrolled burning of vegetation spreading over the forest area. Depending on the elements of the forest in which the fire spreads, fires are divided into ground fires, crown fires and underground (soil), and fires can be weak, medium and strong depending on the speed of the fire edge and the height of the flame. Most often, fires are ground fires.

Peat fires most often occur in places where peat is mined, they usually arise due to improper handling of fire, from lightning discharges or spontaneous combustion. Peat burns slowly to the full depth of its occurrence. Peat fires cover large areas and are difficult to extinguish.

Fires in cities and towns arise when fire safety rules are violated, due to a malfunction of the electrical wiring, the spread of fire during forest, peat and steppe fires, when the electrical wiring is closed during earthquakes.

Landslides are the sliding displacements of the masses rocks down the slope, arising due to 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 activities, etc.). Landslides differ not only in the rate of displacement of rocks (slow, medium and fast), but also in their scale. The speed of slow displacements of rocks is several tens of centimeters per year, medium - several meters per hour or per day, and fast - tens of kilometers per hour or more. Rapid displacements include landslides-flows, when solid material mixes with water, as well as snow and snow-rock avalanches. It should be emphasized that only rapid landslides can cause catastrophes with human casualties. Landslides can destroy settlements, destroy agricultural land, pose a danger to the operation of quarries and mining, damage communications, tunnels, pipelines, telephone and Electricity of the net, water facilities, mainly dams. In addition, they can block the valley, form a dammed lake and contribute to floods.

Avalanches also apply to landslides. Large snow avalanches are catastrophes that claim dozens of lives. The speed of snow avalanches fluctuates in a wide range from 25 to 360 km/h. By size, avalanches are divided into large, medium and small. Large ones destroy everything in their path - dwellings and trees, medium ones are dangerous only for people, small ones are practically not dangerous.

Volcanic eruptions threaten approximately 1/10 of the number of inhabitants of the Earth who are threatened by earthquakes. Lava is a melt of rocks heated to a temperature of 900 - 1100 "C. Lava flows directly from cracks in the ground or the slope of a volcano, or overflows over the edge of the crater and flows to the foot. Lava flows can be dangerous for one person or a group of people who, underestimating their speed, they will find themselves between several lava tongues.The danger arises when the lava flow reaches settlements.Liquid lavas can flood large areas in a short period of time.