The world's largest tsunami height. Tsunami

A tsunami is a giant wave generated by seismic activity and rapidly moving across the surface of the water. These waves have caused a lot of harm to people throughout history, especially for residents of island countries.

More about tsunamis

The greatest geological activity, contributing to the emergence of the strongest waves, is observed in the waters of the Pacific Ocean. Over the last thousand years there have been at least a thousand of them, that is, on average one tsunami per year. In other oceans the statistics are much more modest. The vast majority of tsunamis are caused by a sudden drop or rise of the ocean floor. However, not every such event is fraught with a giant wave; there are other factors, for example, the depth of the source.

In addition to destruction and loss of life, waves can cause other harm. In particular, this is erosion and severe salinization of coastal land areas. Usually, the approaching catastrophe is first felt by birds and animals, which may behave unusually during this period. Within a few hours or even days, they try to escape away from the shore, and pets try in every possible way to make their owners understand this. This is due to the electromagnetic field. Animals are much more sensitive to it than humans, although some people experience severe headaches.

The moored ships have no chance of salvation

Having noticed the approaching tsunami, you need to take documents with you, gather children and other helpless relatives and go away from the dangerous place, trying to avoid bodies of water - rivers, canals, reservoirs, as well as fragile buildings like bridges or towers. What was the largest tsunami in the world? Let us list the most famous cases.

July 1958, Alaska

On a summer day, a terrible natural disaster occurred in Lituya Bay. The bay protrudes into the land for about 11 kilometers, and, according to geologists, giant waves several hundred meters high have arisen here at least four times over the last hundred years. And in 1958, a powerful earthquake occurred in the northern part of the bay, from which houses collapsed, the coast collapsed, and many cracks formed. At the same time, a landslide that came down from the mountain swept across the bay and caused a wave of unprecedented height - 524 meters, which moved at a speed of 160 km/h.

The first to be affected were the people in the ships anchored in the bay. According to the stories, at first they were thrown out of their beds by a strong push. Having run out onto the deck, they could not immediately believe their eyes: the sea reared up, and even a powerful glacier, previously located far to the north, was carried along the sea and collapsed the bays into the water. It was like a nightmare. The water completely engulfed Cenotaph Island, spread over its highest point and, with its entire mass, crashed into the bay, causing another impressive wave. On the mountain slopes to the north, the largest tsunami in history tore away forests up to 600 meters in height.

The tsunami easily swept over the entire sandbank and tore off the forest cover from the nearby mountain slope

One of the longboats was picked up by the wave and thrown over the shallows into the ocean waters. The fishermen could see the trees below them. The ship crashed against rocks and trees, but the fishermen managed to survive and were later rescued. Another ship, by luck, remained in place, withstanding the tsunami, but the third sank; people from it are considered missing. Half an hour later, the surface of the water was completely calm, only strewn with uprooted trees, slowly floating towards the exit from the bay.

December 2004, Indian Ocean

On December 26, in the early morning, a powerful earthquake occurred near the island of Sumatra, part of Indonesia. Its power reached nine points. At the same time, a strong displacement of two tectonic plates occurred. In just an hour, 1,200 kilometers of rock moved fifteen meters, and with them the small islands located in the area. It was in connection with this displacement that the tsunami arose. Devastating consequences awaited the popular Thai resort of Phuket, although its residents and vacationers practically did not feel the initial tremors or did not pay attention to them.

What happened next was a complete surprise for the defenseless city. Warnings about the danger had not yet come from Indonesia, so people found themselves face to face with a huge tsunami completely unprepared. Everyone was minding their own business, when suddenly there was a sharp and strong low tide, leaving behind a lot of shells and other seafood. Residents were delighted with this catch, and tourists were delighted with the free souvenirs.

But very soon waves 30 meters high rolled up to the shore, sweeping away everything in their path. People desperately tried to escape, but the tsunami instantly swallowed many of them. Light bungalows are definitely lighter than houses of cards. Having retreated, the water left behind hundreds of human bodies and debris of buildings.

Almost 230,000 people became victims of the terrible disaster

On March 11, northeastern Japan was hit by a powerful earthquake measuring 9.0. According to scientists, an earthquake of this magnitude occurs once every six hundred years. It all started from a point 373 km from Tokyo and at a depth of 24,000 meters. The result of the shake-up was a devastating tsunami that almost completely covered 23 Japanese regions (in total, more than 62 settlements).

Due to a large tsunami, an accident occurred at the Fukushima-1 nuclear power plant, which had no protection from the waves. Water flooded the diesel generators responsible for the cooling system.

Thus, the power units overheated to a critical state, and a reaction began with a powerful release of hydrogen. This resulted in several explosions that destroyed buildings. A lot of radioactive substances were released into the environment.

The number of people killed in the disaster exceeded 20,000, and monetary damages exceeded $215 million. Six months after the incident, radiation continued to be found in food products, not only in the Fukushima area, but also far from it, although the volume of emissions was approximately 5 times less than Chernobyl.

The maximum wave height was 40 meters, which greatly exceeded the preliminary calculations of scientists

The largest earthquake in the history of mankind occurred in Chile on May 22 and resulted in three huge tsunamis. 5,000 people died and several fishing villages were completely wiped out. The waves also reached the coasts of the USA and Japan, from which these countries also suffered high losses. The earthquake occurred the day before, on May 21, and its continuation the next day had a huge force of 9.5 points and lasted at least ten minutes.

The resulting high wave caused irreparable damage - destruction, casualties, trees uprooted. It is not possible to provide exact numbers; all data is very approximate, since it was not possible to collect reliable statistics, except for eyewitness accounts. Some, for example, believe that there were not 5 thousand dead, but 10 thousand. One way or another, the disaster is simply stunning.

From the air, you can see the outlines of farms and villages underwater, stretching 100 kilometers from the former coastline

About ten thousand hectares of coastal lands were flooded, they are under water to this day. It was assumed that this was due to the fact that as a result of the shift of tectonic plates, sea levels rose. But it turned out that, on the contrary, the surface of the earth became lower.

A 7.8 magnitude earthquake hit the Philippines on August 16. A huge tsunami covered 700 kilometers of coastal territory, killing 5 thousand people and taking away another 2200. 9.5 thousand were injured, and almost one hundred thousand lost their homes.

The worst natural disaster in the history of the state completely destroyed several cities to the ground

On July 17, the northwestern part of the state was shaken by earthquakes with a magnitude of 7. For this reason, in the most remote part of the coast, a deadly wave rose high, the height of which reached 15 meters. More than 2 thousand people fell under it, and several thousand more were left homeless. Before the terrible tragedy, there was a small and very beautiful lagoon there, but due to the earthquake it was blocked by an underwater landslide. There have never been earthquakes of this magnitude in this area before, although smaller ones occur regularly.

As a result of the 1998 tragedy, a completely new large lagoon was formed

Another major tsunami also occurred in Alaska, just six years after the devastating 1958 wave. It all started with an earthquake measuring more than nine points. Already 120-150 people have died because of it. The resulting wave, almost 70 meters high, demolished three villages, taking 107 people with it. The wave then swept along the west coast of the United States, destroying several business offices in downtown Anchorage, as well as fish and crab processing plants on Kodiak Island. The ruins looked as if they had been bombed.

Then the tsunami moved to the city of Crescent City. Residents were warned and managed to evacuate, but later, deciding that there was no more danger, they returned to their homes. This was a big mistake. Strong waves flooded the streets of the city, overturning cars and filling all passages with debris from buildings. The events were truly terrible: the pier was practically twisted into a spiral, some houses moved from place to place.

Total damage was estimated at $400 million, and the President issued an executive order to reconstruct Alaska after the tragedy.

Powerful waves, as you can see, can be extremely dangerous. Like other natural disasters, terrible tsunamis often lead to devastating consequences and take lives. The only reassuring thing is that the residents of Russia do not have to worry in this regard; our regions are not too susceptible to such a disaster, except for certain regions, for example, the island of Sakhalin.

A tsunami is one of the most terrible manifestations of nature's wrath. It is generated by an earthquake, after which a huge wave of water rushes towards land and, as a rule, more than one. Thanks to our territorial location, we are not in danger of being washed away into the ocean, because even if underground vibrations occur somewhere, their echoes only reach us. Islands are the first to get in the way of huge waves, and sometimes people’s carelessness, as well as ignorance of banal safety rules, becomes the cause of their death. After all, it happened more than once that people returned to their homes from shelters immediately after the first wave, although there were always two or more of them. We have collected the top 10 largest tsunami waves in the world and combined them into one list.

10. Our list opens with an unpleasant incident in Japan that happened in 2004. Two earthquakes of 6.7 and 7.2 points created large waves, but due to the distance of 120 kilometers, only meter-long effects of vibrations reached the shore. The incident did not cause any deaths, because the coastal residents were almost unharmed, only escaping with fear.

9. Even though the photographs taken by the residents of the Solomon Islands are not photos of the largest tsunami, this did not in the least prevent two-meter waves from completely razing four large settlements to the ground in 2007. According to official data, the disaster claimed the lives of at least 52 people.

8. A magnitude of 8.8 led to significant earth faults in Chile and also caused a tsunami. Three-meter water flows destroyed the city of Compension, and also caused the death of about a hundred people.

7. The underwater terrain near the island of Papua New Guinea became fatal for its inhabitants. Powerful fluctuations with a magnitude of 7.1 did not easily generate waves, underwater they caused a huge landslide, which, when released, caused a large tsunami. Subsequently, it killed more than 2 thousand people.

6. This happened a long time ago, but the residents of the frosty region will remember it forever. In 1957, an earthquake occurred on the islands near Alaska. All readings taken indicated a magnitude of 9.1, one of the largest recorded. The waves rose up to 14 meters in height, and only due to the fact that the cold region was sparsely populated, the number of victims was only three hundred people.

5. Five years before the incident in Alaska, almost something similar happened near Kamchatka, but in scale it was still large. The height of the tsunami was 18 meters, which destroyed the city of Severo-Kurilsk, completely turning it into complete ruins. At the moment of its rage, the cataclysm took two thousand lives.

4. One of the few cases when it was possible to find out about the cataclysm in advance and save everyone who might have been hurt. Where was the largest tsunami in the world, which never managed to reach its goal - on the islands of Izu and Miyake. The magnitude of only 6.8 generated waves of about 40 meters on average, but fortunately the authorities managed to quickly evacuate local residents.

3. Due to the underground vibrations of 1958, Lituya Bay was visually completely changed. They caused the collapse of a huge part of the mountain slope, which went under water, and this in turn caused the emergence of a water giant measuring 52 meters in height, which met the land at a speed of 150 km/h, radically changing it.

2. Another incident in Alaska happened back in 1964, however, this time in Prince William Sound. Powerful vibrations caused a record 67-meter wave, which killed about one and a half hundred civilians.

1. What is the biggest tsunami in the world? What happened off the coast of Southeast Asia back in 2004. Its power and mercilessness did not easily terrify, the incredible masses of water took the lives of at least 235 thousand people. There were victims in Somalia, Sri Lanka, India, and even Thailand.

This is how eyewitness Howard J. Ulrich, who was there on his yacht Edri, described these events. She entered the waters of Lituya Bay at about eight in the evening and anchored at a depth of nine meters in a small cove on the southern coast. Howard says that suddenly the yacht began to rock violently. He ran out onto the deck and saw how in the northeastern part of the bay the rocks began to move due to the earthquake and a huge block of rock began to fall into the water. About two and a half minutes after the earthquake, he heard a deafening sound from the destruction of rock. “We definitely saw that the wave came from Gilbert Bay, just before the earthquake ended. But at first it was not a wave. At first it was more like an explosion, as if the glacier was splitting into pieces. The wave grew from the surface of the water, at first it was almost invisible, who would have thought that then the water would rise to a height of half a kilometer.” Ulrich said that he observed the entire process of development of the wave, which reached their yacht in a very short time - something like two and a half to three minutes, from the time it could first be noticed. Since we didn't want to lose the anchor, we pulled out the entire anchor chain (about 72 meters) and started the engine. Halfway between the northeastern edge of Lituya Bay and Cenotaf Island, a thirty-meter-high wall of water could be seen that stretched from one shore to the other. When the wave approached the northern part of the island, it split into two parts, but after passing the southern part of the island, the wave became one again. It was smooth, only there was a small ridge on top. When this mountain of water approached our yacht, its front was quite steep, and its height was from 15 to 20 meters. Before the wave arrived at the place where our yacht was located, we did not feel any drop in water or other changes, with the exception of a slight vibration that was transmitted through the water from tectonic processes that began to operate during the earthquake. As soon as the wave approached us and began to lift our yacht, the anchor chain crackled violently. The yacht was carried towards the southern shore and then, on the reverse course of the wave, towards the center of the bay. The top of the wave was not very wide, from 7 to 15 meters, and the trailing front was less steep than the leading one. As the giant wave swept past us, the surface of the water returned to its normal level, but we could see a lot of turbulence swirling around the yacht, as well as erratic waves six meters high, which moved from one birch bay to another. These waves did not create any noticeable movement of water from the mouth of the bay to its northeastern part and back. After 25...30 minutes the surface of the bay calmed down. Near the banks one could see many logs, branches and uprooted trees. All this rubbish slowly drifted towards the center of Lituya Bay and towards its mouth. In fact, during the entire incident, Ulrich did not lose control of the yacht. When the Edri approached the entrance to the bay at 11 pm, a normal current could be observed there, which is usually caused by the daily ebb of ocean water. Lucky man. There are simply no other words... Or the Guardian Angel saved him, advising him to take the right actions...

The most powerful tsunamis resulting from earthquakes can be listed in the following chronological order:

The oldest tsunami known to mankind occurred on July 21, 365 AD. in the Mediterranean Sea after a powerful earthquake, which Chinese chronicles preserved under the name "Hung Tao". A tsunami wave destroyed the city of Alexandria in Egypt and took the lives of thousands of people.

• November 1, 1775, Portugal, the capital of the country, Lisbon, was destroyed by a strong earthquake. The Atlantic Ocean surge, caused by the earthquake, hit the shores of Portugal, Spain and Morocco in 6-meter waves. Miroshnikov L.D. Man in the world of geological elements. St. Petersburg, 2013. P.43.
• 27 August 1883: Indonesia. The Krakatoa volcano erupted. A tsunami wave generated by a volcanic eruption hit the shores of Java and Sumatra with full force, killing 36,000 people. The volcanic eruption was so powerful that the skies were ablaze with the reflections of burning lava for several nights.
• December 17, 1896: USA, California - a tsunami destroyed a powerful sea wall in Santa Barbara and covered all the streets of the city.
• January 31, 1906: An ocean wave resulting from an earthquake in the Pacific Ocean hit the mainland, destroying the cities of Tumaco and Micay in Colombia, the city of Rioverde in Ecuador, destroying all houses. 1500 people died.
• April 1, 1946: US tsunami wave engulfs Alaskan lighthouse and personnel before hitting Hilo-Hawaii, killing 159 people
• May 22, 1960: An 11 meter high tsunami kills 1,000 people in Chile, 61 in Hawaii. The ocean wave was so powerful that it reached the other side of the Pacific Ocean and shook the Philippines and the Japanese island of Okinawa.
• March 28, 1964: USA, "Blessed Easter Friday" tsunami wiped out 3 villages on the country's maps: 107 people died in Oregon, 15 people died in California.
• August 16, 1976: The Pacific tsunami kills more than 5,000 people in Moro Bay in the Philippines.
• July 17, 1998: An earthquake in northern Papua New Guinea created an ocean wave that killed 2,313 people. 7 villages were razed to the ground, thousands of people were left homeless.

The most powerful known tsunami, later named Sanriku, occurred from an underwater earthquake 240 km from the coast of Japan on June 15, 1896. Then a huge wave 30 m high hit the island. Honshu. 27,122 people died. 19,617 houses were washed into the sea. The first “seaquake” in Russia was registered in Kamchatka in 1737. It was already mentioned above. According to an eyewitness, “waves of terrible and incomparable shaking followed, then water rose up onto the shore at a height of 30 fathoms, which, without standing at all, ran into the sea. From this flood, the local residents were completely ruined, and many died miserably.” Miroshnikov L .D. Man in the world of geological elements. St. Petersburg, 2013. P.46.

In 1979, a tsunami with a wave height of 5 m hit the Pacific coast of Colombia. 125 people died.

In 1994, a 15 m high tsunami in the Philippines destroyed 500 houses and 18 bridges. More than 60 people died.

In the case of the recent catastrophe, which began on the morning of December 26, 2004 at 7 hours 58 minutes 53 seconds local time in the Indian Ocean off the coast of Indonesia and Thailand, the epicenter of the first earthquake was located near the northern tip of the island of Sumatra, at a point with coordinates 3 ° 30 "North latitude and 95°87"E longitude. Geologically, in this area there is a boundary between two lithospheric plates - large blocks of the earth's crust. In this case, the oceanic Indian plate is immersed, pushed (subduction) under the more eastern continental plate. The deep-sea trench, which runs parallel to Sumatra, is a trace of such a dive. Danilova V.S., Kozhevnikov N.N. Basic concepts of natural science. M., 2014. P.145.

The tsunami that hit the shores of South Asia on December 26, 2004 was the most catastrophic in the last 40 years, and was caused by the 5th strongest earthquake since 1900, a magnitude 9 earthquake. The tsunami killed more than 225,000 people. The more than 1,000-kilometer fault line, resulting from the earthquake and the movement of large layers of the earth's crust on the ocean floor, generated a colossal release of energy in the ocean, which, combined with the equally colossal energy arising from the displacement of continents, generated the most destructive tsunami in history peace.

Tsunami waves hit the countries of South Asia: Indonesia, Sri Lanka, India, Malaysia, Thailand, Bangladesh, Myanmar, the Maldives and Seychelles, and reached the African continent, hitting the shores of Somalia, located 5,000 kilometers from the epicenter of the earthquake.

The hypocenter of the first shock of the earthquake was shallow, as they say, shallow-focus and was located at a depth of about 30 km. A sharp, almost instantaneous displacement of the ocean plate by tens of meters caused deformation in the surface of the ocean floor, which triggered the occurrence of a tsunami that immediately hit the islands of Sumatra and Java. After about 10-20 minutes, the wave reached the Andaman and Nicobar Islands, and then the western coast of Thailand and the resort island of Phuket. Right there.

It took the tsunami longer, almost two hours, to hit Sri Lanka (formerly the island of Ceylon), the east coast of India, Bangladesh and the Maldives. In the Maldives, the wave height did not exceed two meters, but the islands themselves rise above the ocean surface by no more than a meter and a half, so two-thirds of the territory of Male, the capital of the island state, was under water. However, in general, the Maldives did not suffer too much, since they are surrounded by coral reef structures, which absorbed the shock of the waves and absorbed their energy, thereby providing passive protection from the tsunami. Six hours later the wave reached the east coast of Africa. The tsunami caused the greatest number of casualties and destruction in Indonesia and Sri Lanka. The total death toll is estimated to be more than 280,000. Shchetnikov N. Tsunami. M., 2014. P.97,

According to seismic stations, the earthquake that caused the tsunami in the Indian Ocean, or rather, its first shock had a magnitude of 8.6-8.9 or even 9.1 on the Richter scale, that is, close to the maximum possible. Information has emerged that it contributed to a sharp shift in the Earth’s rotation axis by 3 cm, and the Earth’s day decreased by 3 microseconds. The second shock, the epicenter of which was slightly north of the first, had a magnitude of 7.3 and caused the formation of a second tsunami wave. After the first, strongest tremors on December 26, earthquakes occurred in this region almost every day for several weeks with a fairly high magnitude of about 5-6. Such earthquakes following the main seismic shock are called aftershocks. They indicate the resorption of tensions and their relaxation.

When a tsunami called the “Great Meiji” hit Japan with monstrous destructive force and killed 21,000 people.

Earthquakes of colossal power occur every 150-200 years. There is reliable historical information about this, including about tsunamis caused by earthquakes. When the Krakatoa volcano exploded in the Sunda Strait between the islands of Java and Sumatra in 1883, a giant wave swept more than 36,000 people into the sea; in 1896 in Japan, waves 15 m high led to the death of several thousand people; in 1933, off the coast of Sanriku in Japan, where the height of tsunami waves reached 24 m, 3,000 residents died. In 1952, an 18 m high tsunami destroyed the city of Severo-Kurilsk, located on the island of Paramushir, the northernmost island of the Kuril island arc, killing several thousand residents, as there were three waves. The list of such disasters can be continued. Avakyan A.B., Polyushkin A.A. Floods. M., 2014. P.75.

The question arises: is it possible to foresee a tsunami and warn residents of the regions about the impending wave? It is basically impossible to predict the day and hour of an earthquake, since this is a nonlinear process. But it is possible to identify areas where the risk of an earthquake is high and determine its probable strength, that is, to carry out seismic zoning of territories of varying detail.

The main places where tsunamis occur is the Pacific Ocean, the periphery of which accounts for more than 80% of tsunamis. The famous "ring of fire" of the Pacific Ocean is characterized not only by a large number of active volcanoes, but also by frequent strong earthquakes, mountainous terrain and a chain of deep-sea trenches. In these places, called active continental margins, heavy, cold oceanic plates are subducted under lighter, higher continental plates. The processes of interaction between plates lead to earthquakes, volcanic eruptions and tsunamis in the ocean.

Whether a huge wave will hit the shore after an earthquake in the ocean or not is unknown. Residents of coasts located in a dangerous seismic zone, having felt an earthquake, should immediately flee away from the coastal zone. This way you can escape from a tsunami that forms near the coast, when the arrival time of the wave is 15-30 minutes. If a tsunami occurs far away and the waves move along the surface of the ocean for several hours, then there is enough time to prepare for the impact of the elements and bring people to safe places. But for this, a huge amount of work needs to be done: install automatic seismographs in earthquake-prone areas of the oceans or seas, develop a public warning system so that the panic that is inevitable in such cases does not arise. It is necessary for tourists who come to relax in seismic zones to know about this and have a clear idea of ​​what to do in the event of an alarm, which can be announced by sirens, howlers, radio and any other means. Unfortunately, in the area of ​​the earthquake that occurred on December 26, 2004, the observation network simply did not exist, and the earthquake and tsunami warning system was not organized.

In Russia, back in the late 50s - early 60s of the last century, a tsunami warning service was created in the Far East, covering Kamchatka, the Kuril Islands, Sakhalin and Primorye. In the Hawaiian Islands, which have been repeatedly affected by tsunamis, there is a warning center named after Richard Hagimeier. Now in the Indian Ocean, near Indonesia, it is planned to organize an observation network, and in the future there are intentions to create a global tsunami warning network and equip it with the latest seismographs, special sensors and buoys on which recording equipment will be placed, and all this will be combined with a satellite system. Gorokhov V.G. The concept of modern natural science and technology. M., 2013. P.425.

It turned out, however, that in the history of the Caspian Sea there are known events that could be called “tsunamis”. The earliest of them dates back to 957, when the sea in the Derbent area receded by 150 meters during an earthquake.

Something like a tsunami, albeit in a weakened form, occurred in 1868, when the sea near Baku first rose and then dropped by almost half a meter, and the so-called Burnt Plate, located 90 kilometers south of Baku, rising 2 meters above sea level, sank into him.

Much more terrible waves arose during the 9-point Krasnovodsk earthquake of 1895. They covered the village of Uzun-Ada, the bay of its buildings and the pier with water, forming a quagmire. Two-meter-wide cracks appeared in the streets, from which water was gushing. And in 1933, 40 kilometers from the same Krasnovodsk, a one and a half meter rise in sea level lasting about 10 minutes was observed. Evidence of other phenomena of this kind has also been preserved. Gorokhov V.G. The concept of modern natural science and technology. M., 2013. P.431.

Possible zones for the generation of Caspian tsunamis would naturally include those areas of the sea where seismic activity is especially high. Today, seven local zones of increased seismicity are known in the Caspian Sea, and the largest of them coincides with the extreme eastern section of the Terek-Caspian deep fault. This is where strong earthquakes occur most frequently.

A smaller zone is located within the Absheron threshold - on the underwater section of the same trough. A comparison of areas that have ever experienced something like a tsunami and zones of increased seismicity proves that they certainly coincide. To analyze the reasons for such a local action of the tsunami, modeling was carried out, and it turned out that the relative shallow water and the structure of the bottom prevent it from spreading further.

On the pages of our website we have already talked about one of the most dangerous natural phenomena - earthquakes: .

These vibrations of the earth's crust often give rise to tsunamis, which mercilessly destroy buildings, roads, and piers, leading to the death of people and animals.

Let's take a closer look at what a tsunami is, what are the causes of its occurrence and the consequences it causes.

What is a tsunami

Tsunamis are high, long waves generated by a powerful impact on the entire thickness of ocean or sea water. The term “tsunami” itself is of Japanese origin. Its literal translation is “a big wave in the harbor” and this is not in vain, since in all their power they manifest themselves precisely on the coast.

Tsunamis are generated by a sharp vertical displacement of the lithospheric plates that make up the earth's crust. These gigantic vibrations vibrate the entire thickness of the water, creating a series of alternating ridges and depressions on its surface. Moreover in the open ocean these waves are quite harmless. Their height does not exceed one meter, since the bulk of the oscillating water extends below its surface. The distance between the ridges (wavelength) reaches hundreds of kilometers. The speed of their spread, depending on the depth, ranges from several hundred kilometers to 1000 km/h.

Approaching the shore, the speed and length of the wave begins to decrease. Due to braking in shallow water, each subsequent wave catches up with the previous one, transferring its energy to it and increasing its amplitude.

Sometimes their height reaches 40–50 meters. Such a huge mass of water, hitting the shore, completely devastates the coastal zone in a matter of seconds. The extent of the destruction area deep into the territory in some cases can reach 10 km!

Causes of tsunami

The connection between tsunamis and earthquakes is obvious. But do vibrations in the earth's crust always generate tsunamis? No, tsunami are generated only by underwater earthquakes with a shallow source and magnitude greater than 7. They account for about 85% of all tsunami waves.

Other reasons include:

• Landslides. Often a whole chain of natural disasters can be traced - a shift of lithospheric plates leads to an earthquake, which generates a landslide that generates a tsunami. This is precisely the picture that can be seen in Indonesia, where landslide tsunamis occur quite often.
• Volcanic eruptions cause up to 5% of all tsunamis. At the same time, gigantic masses of earth and stone, soaring into the sky, then plunge into the water. A huge mass of water is shifting. Ocean waters rush into the resulting funnel. This dislocation generates a tsunami wave. An example of a disaster of absolutely terrifying proportions is the tsunami from the Karatau volcano in 1883 (also in Indonesia). Then 30-meter waves led to the death of about 300 cities and villages on the neighboring islands, as well as 500 ships.

• Despite the presence of our planet’s atmosphere, which protects it from meteorites, the largest “guests” from the universe overcome its thickness. When approaching the Earth, their speed can reach tens of kilometers per second. If such meteorite has a large enough mass and falls into the ocean, it will inevitably cause a tsunami.

• Technological progress has brought not only comfort to our lives, but has also become a source of additional danger. Conducted underground nuclear weapons testing, this is another reason for the occurrence of tsunami waves. Realizing this, the powers possessing such weapons entered into a treaty prohibiting their testing in the atmosphere, space and water.

Who studies this phenomenon and how?

The destructive effect of the tsunami and its consequences are so enormous that humanity has become the problem is to find effective protection against this disaster.

The monstrous masses of water rolling onto the shore cannot be stopped by any artificial protective structures. The most effective defense in such a situation can only be the timely evacuation of people from the danger zone. For this a sufficiently long-term forecast of the upcoming disaster is necessary. Seismologists do this in collaboration with scientists from other specialties (physicists, mathematicians, etc.). Research methods include:

• data from seismographs recording tremors;
• information provided by sensors carried out into the open ocean;
• remote measurement of tsunamis from outer space using special satellites;

• development of models for the occurrence and propagation of tsunamis under various conditions.

If this message was useful to you, I would be glad to see you