Huge waves, reaching a height of tens of meters and falling with terrible force on the coast, are called tsunami. The name comes from a Japanese phrase. It is denoted by two hieroglyphs and means in translation: "a big wave flooding the bay." In reality, the wave is not just big, it is gigantic. Its height can reach up to 30-40 meters, and it can cover the land for many kilometers. At the same time, the element sweeps away everything in its path. People and animals are dying, houses are being destroyed, utility networks are being mutilated and destroyed, and the fertile layer of soil is being washed away.

Human casualties can reach tens of thousands of people, since such catastrophes do not know pity, while material losses are incalculable. But no less terrible is the grief of those who lost their loved ones in this terrible natural disaster. The consequences of the tsunami are so terrible that they tremble the entire planet, and another disaster is entered into the historical annals of the world's greatest tragedies.

Causes of a tsunami

There are several reasons for the occurrence of huge waves.. The most basic, which causes up to 85% of all tsunamis - underwater earthquakes, during which there are sharp fluctuations in the seabed. The huge energy released in this case is transferred to the water column. The oceanic masses begin to revolt and scatter in waves from the epicenter of the earthquake.

Killer Wave Behavior

In the vast expanses of the sea, such waves are almost imperceptible. They have a flat shape, with a height not exceeding one meter and a length reaching hundreds of kilometers. The energy in such a wave is dispersed over a huge area, and even a fragile boat will not feel all the strength and power that will pass under it.

These fluctuations in the aquatic environment propagate at great speed. It can be equal to 500, and 700, and even 1000 km / h - it all depends on the thickness of the sea water. When approaching the shore, the depth decreases, the speed decreases accordingly and the wavelength shortens. Its height begins to grow rapidly. It turns into a huge water shaft, which with a roar falls on the coastal zone. These thousands and thousands of tons of raging elements sweep away everything in their path.

Tsunami near the coast

Having done its terrible job and wasting all its energy, the ocean exhaustedly crawls away from the land, calms down, accumulates strength - this can last for 20, and 40, and 60 minutes. But here the coastal water begins to slowly recede from the shore, exposing an uneven muddy bottom. The surrounding tormented world anxiously freezes in anticipation of something terrible and bad. Silence thickens, the air is filled with anxiety, turning into horror.

In the sea distance, a second, even larger wave of water begins to grow. It expands before our eyes, closes the horizon, breaking the silence with a terrible roar, collapses onto the earth's firmament, finishing the terrible deed begun by the first wave. Deadly energy destroys everything that is still alive, kills everything that is still alive. Plenty of fun with their impunity and permissiveness, the elements are leaving, but the end of this horror is still far away.

An hour or so passes, and the long-suffering earth takes the third terrible blow. The nightmare can go on for five or six hours. Only after this time has passed, having fully satisfied its basest instincts, does the ocean calm down. Having spent all the negativity, the marine environment before our eyes turns into a quiet, gentle, gentle and obedient blue expanse of water. Only the mutilated land reminds of the horror experienced, on which uprooted trees are scattered in disarray, the remains of houses are scattered, roads and flowering gardens are destroyed.

After the tsunami

Tsunami in the Pacific Ocean

This is the picture of this terrible natural phenomenon, which appeared when the World Ocean arose. In general, a terrible cataclysm occurs in different coastal zones 6-7 times a century. But these are large tsunamis. Small ones are ten times more common. Most of all, the waters of the Pacific Ocean gravitate towards the terrible killer waves, since the bottom of this huge reservoir is cut by numerous gutters and faults, like deep wounds.

It is in these places that the various tectonic plates come into contact. Geological processes are going on here continuously, and hence the increased seismic activity. The western peripheral zone of the Pacific Ocean poses a great danger. The untrustworthy Kuril-Kamchatka Trench and the Japanese Trench are located here. To the north is the Aleutian Trench, whose behavior also leaves much to be desired.

In the east of the Great Ocean, the Peruvian-Chile Trench sets the tone, simply terrorizing the waters of South America. In the southern part of a huge body of water, north of New Zealand, the Kermadec trough stretched out straight as an arrow, bursting with seismically active processes. Well, off the eastern coast of North America, exactly along cloudy California, there are as many as five faults. Completes this far from optimistic picture of the Central American Trench, which can be considered native to Mexico, Guatemala and El Salvador.

The earth's crust in places of faults and trenches is constantly shaking, so earthquakes are frequent guests in these areas. But not every one of them is capable of generating a tsunami. To move huge masses of water, titanic energy is needed. This can only be provided by very strong uplifts and subsidences of the seabed. On a twelve-point Richter scale, this is a magnitude of 7 or more. It can only be higher than 9 points, there are no large magnitudes on Earth, so shocks of such strength are quite rare.

Otherwise, huge killer waves would have been in a fever of the coastal zone as often as a change in wind direction or seasonal temperature fluctuations. True, small tsunamis often appear along various coasts. But the supply of their energy is so negligible that they cannot cause serious harm with all their desire. It is in their power to really spoil the nerves, upset someone because of the loss of a fishing boat or boat, but such situations, as a rule, arise due to absent-mindedness or inattention of the people themselves.

Tsunami in Japan

The height of the terrible waves largely depends on the shape and topography of the coastline. The wave comes in a wide front and in those places where a steep coast or a bay deeply cutting into the land, the roaring shaft reaches its maximum height. If you are in a closed bay, then you can not even guess that just a few kilometers from this place everything collapses and dies.

Landslides and underwater eruptions

Another reason for the occurrence of killer waves is such a geological process as landslides.. In terrestrial conditions, this is a common thing when a large mass of rocks slides down the slope of a valley or river bank. Such a movement can last for decades, or it can start unexpectedly, take place rapidly and end in a short time. Piles of earth slide into a valley or into a river, causing some damage to the environment.

Similar processes take place on the seabed, since there are no less mountains and hills than on land. Sedimentary rocks accumulate on the slopes of underwater mountain ranges. Over time, their mass becomes critical, and they collapse down, creating vibrations in the surrounding aquatic environment. If there is enough energy, then a tsunami will arise, which in size may not be inferior to a similar wave formed by an earthquake.

Due to the fault of landslides, such waves appear on the sea surface much less frequently. Of the total number of tsunamis, this is only 7%. Even rarer (5%) tsunamis are caused by volcanic eruptions. It also releases a huge amount of energy that can disturb the thickness of the ocean waters. In these cases, the wave can be even more powerful than during earthquakes, since additional energy is absorbed when it comes into contact with magma.

Here are perhaps all the main reasons that give rise to terrible waves and tremble the huge masses of people who, by the will of fate, are forced to live in coastal zones. As for the opposition to this element, then the picture is very pessimistic. The determining factor here is timely notification of the population about an impending disaster. Forewarned is forearmed. This famous saying is universal, guided by it, you can save many, many lives.

Ships washed ashore by the tsunami

Preventive measures

Today it is known that killer waves are always the result of an earthquake. To fix powerful underwater tremors in time means with sufficient probability to predict the appearance of huge waves off the coast. True, the notification of areas inhabited by people should be instantaneous. After all, the perturbation of the aquatic environment spreads with great speed and in half an hour can move hundreds of kilometers away from the epicenter of the earthquake.

Given the causes of tsunamis, many states pay great attention to the creation of seismic stations in those places where active geological processes are taking place. The International Service for Warning the Population of an Imminent Catastrophe has been formed. Its centers are located on the island of Oahu in the suburbs of Honolulu and on six other islands of the Hawaiian archipelago. Employees are on duty here around the clock, processing information from dozens of seismic stations scattered across the Pacific Ocean.

In the event of a suspected tsunami, huge areas are immediately notified, plans to mobilize the population from dangerous zones come into force. Fortunately, in most of these cases, huge waves do not occur. Given the peculiarities of the human psyche, the medal also has a reverse side. Frequent unreasonable alarms lead to the fact that people gradually become discouraged, they begin to ignore messages about danger. The element is very insidious and is only waiting for a person to relax and lose caution.

How to behave during a disaster

In any case, no matter how frequent reports of an impending disaster are, it is better not to look at careless people, but to rely only on your common sense and sense of self-preservation. The first sign of tragedy is the disappearance of water near the shore. The ocean is slowly moving away from the coastal zone, preparing to deliver a powerful blow. If this happened - there is no doubt that the killer wave is already close. After that, there is nothing to think about and hope for a chance. Procrastination is like death.

You need to immediately pick up children, documents, money and leave or leave as far from the coast as possible. It is strictly forbidden to move inland along the riverbed - it is necessary to keep from it at the maximum possible distance. The best option is to climb to a distant hill. This will be the safest place in the coastal zone. The most optimal thing is to move away from the coastline for several kilometers: even very high waves are unlikely to reach the mark of five or more thousand meters from the ocean boundary.

But ships or yachts, peacefully dozing in the roadstead, when a tsunami approaches, have only one way out - they need to immediately weigh anchor and go into the open ocean. As paradoxical as it sounds, they must rush at full speed towards the terrible wave. In open sea spaces, it is almost imperceptible, and gains power, strength and height only near the coast.

All of the above are not empty words, but quite real guide to action. Tsunami is a terrible force. Only those who do not value their lives can underestimate it. Numerous historical facts serve as a clear confirmation of this.

History reference

Terrible waves crashed on the earth's firmament in all ages, but the first detailed description, with an attempt at scientific justification, of this catastrophe was given by the great Spanish historian and geographer, a member of the Jesuit order, José de Acosta (1539-1600). Just before leaving for Spain in 1586, fate gave him the opportunity to observe a killer wave in Peru. It was a terrible sight when, after a strong earthquake, a 25-meter-high water shaft hit the capital of Lima. He broke into the depths of the land for 10 km, having done trouble hundreds of times more than the most cruel invaders would have done.

Krakatoa volcano eruption

Volcano Krakatoa

Truly monstrous were the consequences caused by the tsunami that arose as a result of the eruption Krakatoa volcano in 1883. At that time, this name was not given to an active volcano on the island of Rakita, but to an island of quite decent size located in the Sunda Strait, between the islands of Sumatra and Java.

The volcanic eruption on this island began in May 1883. It lasted until the end of August and represented strong ejections of magma and gas from the bowels of the earth following one after another. Logically, over time, the intensity and strength of the emissions should have weakened. But in this case, events began to develop according to a different scenario.

The volcano became more and more inflamed, gradually falling into uncontrollable ecstasy. In the end, on a cloudy and gloomy morning on August 27, an explosion of terrible force occurred. A huge column of ash soared into the air to a crazy height of 30 km. After that, having apparently exhausted all its magmatic energy, the volcano subsided exhaustedly. One could breathe easy, but it was the calm before the storm.

The fact is that a void of enormous volume and area formed under the volcano, since all the rock deposited here was thrown into the atmosphere. Everything would be nothing, but this empty space was much lower than the level of the oceans. Innumerable tons of water began to press on the thin walls left without support. The problem was aggravated by the island's firmament, which now simply hung in the air.

The climax came the next day in August. The walls of the empty underground chamber of the volcano could not withstand the terrible loads. Cracks ran across the surface of the island: rocky rocks collapsed down. Sea water rushed into the openings, widening its passage, with a roar.

In fact, it turned out an open wound in the earth's crust. The red-hot magma, located deep below, entered into interaction with a cold liquid medium. The result was a terrible explosion, the shock wave from which spread over 300 km, breaking trees on the islands, demolishing roofs of houses, maiming animals and people. The roar of the explosion was heard at a distance of 4 thousand km.

Location of Krakatoa volcano on the map

Even worse than the shock wave was a huge tsunami, the height of which reached 30 meters. She hit the shores of Indonesia with frenzied fury, the coastline of Southeast Asia experienced her strength. The killer wave reached the western coast of Australia, with a roar hit the shores of the island of Ceylon and the eastern coast of the Hindustan peninsula. Its echoes have recognized the island of Madagascar and the entire east coast of Africa.

Due to the killer wave, 48 thousand people died. The vast coastal areas were mutilated beyond recognition. Tens of thousands of people were left homeless. The tragedy of the island of Krakatoa has written another bloody page in the history of world catastrophes.

Killer waves in the 20th century

The twentieth century tried to keep up with previous centuries in terms of the number of tsunamis. In November 1952, 150 km. an earthquake measuring 8.5 on the Richter scale occurred off the coast of Kamchatka. As a result, a perturbation of the aquatic environment arose. Giant waves, the height of which reached 20 meters, swept the city of Severo-Kurilsk off the face of the earth. Nearby settlements were also destroyed. According to the most conservative estimate, 3,000 people died.

Throughout the second half of the 20th century, Alaska fought off terrible waves. In total, there were about ten tsunamis here, while there were three large ones that caused human casualties and destruction. Became a victim of evil rock and New Guinea. In 1998, a huge wave caused the death of one and a half thousand people.

Killer waves in the 21st century

The beginning of the 21st century was marked by killer waves together with all of humanity. True, they were exactly 4 years late, but they compensated for this with human casualties. This tragedy happened at the end of December 2004. As a result of a strong earthquake (8.5 on the Richter scale), a giant wave arose that hit the shores of Thailand, Sri Lanka and Myanmar. The number of victims exceeded 200 thousand people.

In 2007, on the Solomon Islands, located east of New Guinea, a huge wave, the height of which reached 12 meters, destroyed many residential buildings, causing great damage to people. In this wave, 48 people found their death.

The terrible tragedies associated with the tsunami will apparently continue until the scientific and technological progress that is marching ahead will come up with effective ways to deal with them. It is clear that this is a matter of the distant future, but in our time only those who live in the depths of the continents can sleep peacefully, and do not appear on the coasts of the oceans at all or go there no more than once a year.

Taking into account the fact that 85% of the entire population of the planet have chosen the coastal zones of the oceans and seas, this problem is very acute for all mankind. In this situation, one can only hope for the composure, attentiveness and mobility of people, as well as the clear and well-functioning work of warning services.

By the way, when in January 2005 a powerful earthquake occurred dangerously close to the Izu Islands (Japan), the notified population managed to evacuate in time, not a single person was injured. Well, what can I say - the Japanese are again ahead of the rest.

The article was written by ridar-shakin

Based on materials from foreign and Russian publications

A is the depth of the ocean (the so-called shallow water approximation, when the wavelength is much greater than the depth). With an average depth of 4 km, the propagation velocity is 200 m/s or 720 km/h. In the open ocean, wave height rarely exceeds one meter, and the wave length (distance between crests) reaches hundreds of kilometers, and therefore the wave is not dangerous for navigation. When waves enter shallow water, near the coastline, their speed and length decrease, and their height increases. Near the coast, the height of a tsunami can reach several tens of meters. The highest waves, up to 30-40 meters, are formed near steep banks, in wedge-shaped bays and in all places where focusing can occur. Coastal areas with closed bays are less dangerous. A tsunami usually manifests itself as a series of waves, since the waves are long, more than an hour can pass between wave arrivals. That is why you should not return to the shore after the departure of the next wave, but you should wait a few hours.

The wave height in coastal shallow water (H shallow), which does not have protective structures, can be calculated using the following empirical formula:

H small = 1.3 H deep (B deep / B shallow) 1/4, m

where: H deep - initial wave height in a deep place;

B deep - depth of water in a deep place; B small - water depth in the coastal shallows;

Reasons for the formation of a tsunami

The most common reasons

Other possible causes

• Human activity. In our age of atomic energy, man has in his hands a means to cause concussions, previously available only to nature. In 1946, the United States carried out an underwater atomic explosion in a 60 m deep sea lagoon with a TNT equivalent of 20,000 tons. The wave that arose at a distance of 300 m from the explosion rose to a height of 28.6 m, and 6.5 km from the epicenter it still reached 1.8 m. landslides and explosions are always local. If several hydrogen bombs were simultaneously exploded on the ocean floor, along any line, then there would be no theoretical obstacles to the occurrence of a tsunami, such experiments were carried out, but did not lead to any significant results compared to more accessible types of weapons. At present, any underwater testing of atomic weapons is prohibited by a series of international treaties.

• The fall of a large celestial body can cause a huge tsunami, because, having a huge falling speed (tens of kilometers per second), these bodies have colossal kinetic energy, and their mass can be billions of tons or more. This energy is transferred to the water, resulting in a wave.

• Wind can cause large waves (up to about 20 m), but such waves are not tsunamis, as they are short-term and cannot cause flooding on the coast. However, the formation of a meteorological tsunami is possible with a sharp change in pressure or with a rapid movement of an atmospheric pressure anomaly. This phenomenon is observed in the Balearic Islands and is called rissaga (en: Rissaga).

Signs of a tsunami

• Sudden rapid withdrawal of water from the shore for a considerable distance and drying of the bottom. The further the sea recedes, the higher the tsunami waves can be. People who are on the shore and unaware of the danger may stay out of curiosity or to collect fish and shells. In this case, it is necessary to leave the coast as soon as possible and move away from it to the maximum distance - this rule should be followed, for example, while in Japan, on the Indian Ocean coast of Indonesia, Kamchatka. In the case of a teletsunami, the wave usually approaches without the water receding.
• Earthquake. The epicenter of an earthquake is usually in the ocean. On the coast, the earthquake is usually much weaker, and often there is none at all. In tsunami-prone regions, there is a rule that if an earthquake is felt, it is better to move further from the coast and at the same time climb a hill, thus preparing in advance for the arrival of a wave.
• Unusual drift of ice and other floating objects, formation of cracks in fast ice.
• Huge reverse faults at the edges of immovable ice and reefs, the formation of crowds, currents.

Tsunami danger

It may not be clear why a tsunami several meters high turned out to be catastrophic, while waves of the same (and even much higher) height that arose during a storm do not lead to casualties and destruction. There are several factors that lead to catastrophic consequences:

• The height of the wave near the coast in the case of a tsunami, generally speaking, is not a determining factor. Depending on the configuration of the bottom near the coast, the tsunami phenomenon can pass without a wave at all, in the usual sense, but as a series of rapid tides, which can also lead to casualties and destruction.

• During a storm, only the surface layer of water comes into motion. During a tsunami - the entire water column, from the bottom to the surface. At the same time, a volume of water splashes onto the shore during a tsunami, thousands of times greater than storm waves. It is also worth considering the fact that the length of the crest of storm waves does not exceed 100-200 meters, while in a tsunami the length of the crest extends along the entire coast, and this is more than one thousand kilometers.

• The speed of tsunami waves, even near the coast, exceeds the speed of wind waves. The kinetic energy of tsunami waves is also thousands of times greater.

• A tsunami, as a rule, generates not one, but several waves. The first wave, not necessarily the largest, wets the surface, reducing the resistance for subsequent waves.

• During a storm, the excitement builds up gradually, people usually have time to move to a safe distance before the arrival of large waves. The tsunami comes suddenly.

• Tsunami damage can increase in harbors, where wind waves are attenuated and, consequently, residential buildings can stand close to the shore.

• Lack of basic knowledge among the population about the possible danger. So, during the 2004 tsunami, when the sea receded from the shore, many local residents remained on the shore - out of curiosity or out of a desire to collect fish that did not have time to leave. In addition, after the first wave, many returned to their homes - to assess the damage or try to find loved ones, not knowing about subsequent waves.

• The tsunami warning system is not available everywhere and does not always work.

• The destruction of coastal infrastructure exacerbates the disaster, adding catastrophic man-made and social factors. Flooding of lowlands, river valleys leads to soil salinization.

Tsunami Warning Systems

Tsunami warning systems are built mainly on the processing of seismic information. If the earthquake has a magnitude of more than 7.0 (in the press this is called points on the Richter scale, although this is an error, since the magnitude is not measured in points. The point is measured in points, which characterizes the intensity of shaking the ground during an earthquake) and the center is located under water, then a tsunami warning is issued. Depending on the region and the population of the coast, the conditions for generating an alarm signal may be different.

The second possibility of a tsunami warning is a "post-warning" - a more reliable method, since there are practically no false alarms, but often such a warning can be generated too late. The warning is actually useful for teletsunamis - global tsunamis that affect the entire ocean and come to other ocean boundaries after a few hours. Thus, the Indonesian tsunami in December 2004 is a teletsunami for Africa. A classic case is the Aleutian tsunami - after a strong surge in the Aleuts, a significant surge can be expected in the Hawaiian Islands. To detect tsunami waves in the open ocean, near-bottom hydrostatic pressure sensors are used. A warning system based on such sensors with satellite communication from a near-surface buoy, developed in the USA, is called DART (en:Deep-ocean Assessment and Reporting of Tsunamis). Having detected a wave in one way or another, it is possible to accurately determine the time of its arrival in various settlements.

An essential point of the warning system is the timely dissemination of information among the population. It is very important that the population is aware of the threat that a tsunami brings with it. Japan has many natural disaster education programs, and in Indonesia the population is largely unfamiliar with the tsunami, which was the main reason for the large number of victims in 2004. Also important is the legislative framework for the development of the coastal zone.

The biggest tsunamis

20th century

• November 5, 1952 Severo-Kurilsk (USSR).

see also

Sources

• Pelinovsky EN Hydrodynamics of tsunami waves / IAP RAS. Nizhny Novgorod, 1996. 277 p.
• Local tsunamis: prevention and risk reduction, collection of articles. / Edited by Levin B.V., Nosov M.A. - M .: Janus-K, 2002
• Levin BV, Nosov MA Physics of tsunami and related phenomena in the ocean. M.: Janus-K, 2005
• Earthquakes and Tsunamis - Study Guide - (Contents)
• Kulikov E. A. "Physical foundations of tsunami modeling" (training course)

Tsunami in art

• "Attention, tsunami!" - feature film (Odessa Film Studio, 1969)
• "Tsunami" - song by V. S. Vysotsky, 1969
• "Tsunami" - the name of the album of the group "Night snipers" ().
• "Tsunami" - a novel by Gleb Shulpyakov
• "Tsunami" - Korean film, 2009
• "2012 (film)", 2009
• The film "Collision with the abyss", 1998
• Tsunami 3D - thriller 2012
• Catastrophic natural phenomena. An electronic version of the rescuer's textbook by a team of authors (Shoigu S.K., Kudinov S.M., Nezhivoi A.F., Nozhevoi S.A., edited by Vorobyov Yu.L.), published by the Russian Emergencies Ministry in 1997.

Notes

Links

	Tsunami in Wiktionary
	Tsunami at Wikimedia Commons
	Tsunami at Wikinews

• Tsunami Thailand (Koh Phi Phi) 2004 on YouTube (showing several phases of the arrival of the tsunami starting from calm water)

Tsunami- an incredibly dangerous phenomenon of nature. Terrifying consequences make you feel unimportant. But, as they say, you need to know your enemy by sight, so let's find out more about this evil joke of nature:

The most at risk from tsunamis are: California, Hawaii, Oregon and Washington. Hawaii is the most at risk and has about 1 tsunami per year and a dangerous tsunami about every 7 years.

On March 28, 1964, an extremely strong earthquake hit Alaska. This caused tsunami waves that were very destructive in southeast Alaska, Vancouver and Canada. Waves ranged in size from 6 to 21 feet. The tsunami killed more than 120 people and caused more than $106 million in damage. It was the most costly tsunami for the western United States and Canada.
The scientists concluded that the impact of a moderately large asteroid (about 5-6 km in diameter) in the middle of the Atlantic Ocean would generate a tsunami that would travel all the way to the upper two-thirds of the United States. Coastal cities will be destroyed by such a tsunami.
Nuclear explosions can create tsunamis, but there are no test results yet. In addition, such testing is currently prohibited by international treaties.

In an underwater earthquake or other major disturbance that causes sudden increases or decreases in the mass of water above the affected area. This sudden movement of water creates a series of powerful waves.
Underwater earthquakes, which cause significant changes to the ocean floor and the movement of large volumes of water, are the most common cause of tsunamis.
Tsunamis can also be triggered by other underwater events such as volcanic eruptions and landslides.
Tsunamis can also be associated with events above the ocean floor. These events may include meteorite impacts into the ocean, large landslides near coastlines, materials from an erupting volcano, or the formation of a landslide. The consequences of a tsunami caused by such factors are usually localized.
More than 75 percent of tsunamis are caused by underwater earthquakes.

Where do tsunamis occur?

Most tsunamis occur in the Indian and Pacific Oceans. The borders of the Pacific Ocean experience frequent earthquakes. This border is known as the "Ring of Fire". There are two major subduction zones in the Indian Ocean that can also generate tsunamis.
Earthquake subduction zones are the most common source of destructive tsunamis. These earthquakes are formed when two tectonic plates meet and one slides under the other. The sinking plate is pulled towards the top plate, resulting in a bend. The top plate is restored to its original position, displacing sea water.

In December 2004, an earthquake off the coast of Indonesia led to the fact that 10 minutes after the event, the sea surface was displaced in the direction from the epicenter, like a tsunami. In this figure, the red arrows indicate the direction in which the top plate deforms due to drag and releases the bottom plate.

• In the deep waters of the ocean, waves are created with long wavelengths, but usually no more than one meter high. Tsunami waves can be hundreds of kilometers long, and they travel at very high speeds and over long distances without losing much of their energy.
• You can see a mini tsunami if you throw a large object into the water.
• Tsunamis in the open ocean can move at a speed of 950 kilometers per hour (this is the speed of a passenger aircraft). A tsunami loses speed as it approaches the ground, but it doesn't lose much of its energy.

• In the open ocean, it can be difficult to spot tsunami waves. However, as the tsunami wave approaches and moves to a shallower depth, the leading edge of the wave slows down, while the waves at the rear still travel at their original speed. This causes the water to crumple into a heap and results in an increase in wave height. This process is known as "shallowing". When a wave hits the ground, it can behave like a series of surfs or just a big powerful wave.
• The huge energy of the wave can cause a large amount of water to rush inland, far beyond the coastal zone.
• Some of the largest tsunami waves were generated by the eruption of the Krakatau volcano in 1883. That tsunami reached a height of 37 m. In 1737, the tsunami had a wave height of 64 m and above (its impact fell on Cape Lopatka, in northeastern Russia).
• Tsunami waves are different from normal waves!Normal waves generated by wind and water moving near the surface. In a tsunami, all the water moves from the surface to the bottom of the ocean, and this movement is formed due to the displacement of water (as a rule, this is caused by earthquakes). In the open ocean, tsunamis create little traffic and a great threat to shipping.
• When a tsunami reaches the coast, its wavelength can be more than 100 km. A tsunami can last for hours or even days, depending on the location. This is quite different from the waves we are used to seeing on the beach. Typical ocean waves typically last less than a minute and are only 100 meters long.
• The energy from the tsunami is enough to de-sand the entire beach, uproot trees, and crush buildings.
• People and boats are powerless against the force of the tsunami. The amount of water involved in a tsunami is capable of flooding large areas of ordinary dry land.

The most famous tsunamis in recent times:

• Solomon Islands April 2, 2007

On April 2, 2007, an earthquake struck with a magnitude of 8.1 on the Richter scale. The earthquake struck in shallow water early in the morning and was quickly followed by a tsunami. The waves were up to 10 m high. More than 50 have been registered and thousands have been left homeless. Tsunami warnings were issued in Australia and Alaska 15 minutes after the quake.

• Samoa September 29, 2009

At 6:49 am, an 8.0 magnitude earthquake triggered this tsunami, which caused extensive damage to property and the natural environment, and resulted in over 100 deaths.

• Chile February 27, 2010

It was caused by an 8.8 magnitude earthquake. The epicenter of the earthquake was located 115 km from Concepción. The epicenter of the earthquake was 230 km. This earthquake was the result of plate movement in the eastern Pacific and the South American plate. The first waves hit about 34 minutes after the earthquake. Buildings were severely damaged and over 200 lives were lost.

• Papua New Guinea 17 July 1998

An earthquake measuring 7.0 on the Richter scale just off the northern coast triggered a devastating tsunami. Waves up to 10 meters passed through the villages in the Aitape region very quickly. More than 2,000 people were killed, and the tsunami caused severe damage to buildings and farmland.

• December 26, 2004 Indian Ocean Tsunami

This tsunami has become one of the most devastating natural disasters in recent years.. The earthquake that caused it occurred just west of the Indonesian island of Sumatra and measured 9.0 on the same Richter scale, making it largest earthquake worldwide in the last 40 years . The death toll in March 2005 was over 273,000, with many missing.

And now the turn of incredible video materials:

Tsunami Thailand - 2004

Japan 2011 tsunami video

Tsunami in Khao Lak

What kind of elements are not on Earth: tornadoes, tsunamis, earthquakes, volcanic eruptions, avalanches, floods, fires and so on. Many of them are destructive. We will talk more about the tsunami. What it is, many know firsthand. "Big wave in the harbor" - that's how the word "tsunami" is translated. We are talking about marine gravity waves that arise as a result of earthquakes (underwater, coastal) or the shift of individual sections of the seabed.

Many people really know about the destructive power of tsunamis. People are very afraid of this unbridled phenomenon. And this fear is passed on from generation to generation. Sometimes tsunamis are even called "killer waves" because they have already claimed millions of lives.

Tsunami has the following characteristics:< ul >

• wave height reaches 50 meters and above;
• its propagation speed is 50-1000 km/h;
• the number of waves coming ashore varies from 5 to 25;
• the distance between the waves can reach 10-100 or more kilometers.
• Do not confuse tsunamis and ship, storm waves. In the first case, the movement of the entire thickness of the wave occurs, in the second - only the surface layer.

Tsunami: what is it - causes and signs

Scientists have been studying the nature of such a phenomenon as a tsunami for more than a decade. Among the reasons that cause it are:

• underwater landslides;
• falling into the ocean or sea of ​​meteorites, comets or other celestial bodies;
• volcanic eruptions (under water);
• underwater earthquakes;
• tropical cyclones, typhoons;
• excessively strong wind;
• testing of military weapons.

As a result of any of the above causes occurring on the seabed, a force is released that forms the lightning movement of water. Most often, tsunamis are caused by underwater earthquakes.

Scientists can guess what the consequences of such a catastrophe will be. But it is extremely difficult for people to survive this, and more often it is impossible. No wonder why all the dinosaurs died at one time.

Is it possible to know in advance that a tsunami is coming? Of course, scientists have identified a number of signs that indicate that a tsunami will happen soon. The first sign of a tsunami is an earthquake. Therefore, having felt the first intense tremors, one can understand that the wave will be strong. The second sign is a sharp ebb. The more water goes deep into the ocean or sea, the higher the waves will be.

Tsunami: myths and truth

People live and do not know that not all those tales about the tsunami that go among people are true.
Myths:

1. Tsunamis can occur only in warm seas. This is not true. They happen everywhere. It's just that most tsunamis occur in the Pacific Ocean.
2. The power of a tsunami depends on how far the water has moved away from the coast before the elements. In fact, it is the wavelength that depends on the waste of water, and not its power. And the coast is not always shallow before the tsunami. Sometimes, on the contrary, water is in front of the tsunami.
3. A tsunami is always accompanied by a big wave. No, a tsunami is not just a wall of water that crashes onto the shore. In some cases, such a wall may not exist.
4. The arrival of a tsunami is always imperceptible. Yes, the element does not clearly warn of its onset. But attentive scientists always notice the approach of a tsunami.
5. The largest is the first wave of the tsunami. This is wrong again. Waves reach the coast after a certain period of time (from several minutes to an hour). And it is the waves following the first that often turn out to be more destructive, since they "fall" on the wet shore, when the resistance has already been reduced.

The truth is that animals always feel when a tsunami comes. They are trying to leave the dangerous area in advance. Therefore, after the tsunami, you may not find the corpses of animals at all. Fish at the same time try to hide in the corals. Perhaps it makes sense to listen to the "call" of pets for everyone who lives in seismically hazardous areas?!

How to escape from a tsunami?

The only thing that can save a life in such a catastrophic situation is an escape inland. People who have become hostages of the elements should leave as soon as possible, run away from the coastline. At the same time, you should lay your route away from the river bed, because there tsunami waves can overtake very quickly. Ideally, you should climb a mountain, to a height of more than thirty meters. Those who were caught by the elements at sea should sail away on a ship to the sea, since it is simply pointless to sail ashore - certain death awaits there.
By following the recommendations, remaining calm and vigilant, and also having good preparation, you can always escape from such a destructive element. But the best advice: if you are very afraid of dying during a tsunami, leave seismically dangerous areas. As you know, tsunamis are frequent guests of the coast, the Pacific Ocean (about 80% of all active volcanoes of the Earth are concentrated here), Sakhalin Island, the Maldives, the coast of Australia, Japan, India, Peru, Thailand, Madagascar.