What is a tsunami? How is this natural phenomenon formed? What are the reasons for these giant waves? By what signs can you determine that a tsunami is coming. Let's take a closer look at where they most often occur and give statistics on the most devastating natural disasters that have occurred due to tsunamis over the past 50-60 years.
The definition of the word tsunami when translated from Japanese means "wave in the harbor." i.e. tsunamis are large and long waves that are formed due to the impact on the entire water column. This is the difference between a simple large storm wave and a tsunami, since in a large storm wave the impact occurs only on the surface, while in a tsunami the entire water column is affected. Of course, the larger the body of water, the larger and longer the tsunami. Tsunamis can only form in the seas and oceans. When a tsunami most often forms not one wave, but several, which are thrown onto land with a time interval between them from 2 minutes to 2 hours.
Causes of a tsunami
Scientists share several reasons for the occurrence of such a natural phenomenon as a tsunami. A tsunami mainly comes from the impact on the bottom of the sea or ocean, as a result of which a force is released, which forms the movement of the entire water column - that is, a tsunami.
These are such natural phenomena as:
- - underwater earthquakes;
- - landslides;
- - underwater volcanic eruptions;
- - the fall of a large celestial body into the ocean or sea (for example, the Tunguska meteorite);
- - military tests (for example, tests of nuclear weapons in the ocean or sea).
How does a tsunami occur due to earthquakes?
Large waves are formed due to the displacement of lithospheric plates, while the plates themselves begin to move as a result of underwater earthquakes. The mechanism of wave formation as a result of the displacement of lithospheric plates is as follows: one plate begins to crawl under the other, as a result, a sufficiently large force is formed that lifts the second lithospheric plate upwards, and this effect also sets the water column in motion.
Other Causes of a Tsunami
The next cause of such waves as tsunamis is landslides. For example, a large landslide occurred off the coast of Alaska and a large amount of ice and earth rocks collapsed into the water from a great height, resulting in a large and long wave. Off the coast of Alaska, the wave reached a height of more than 500 meters.
Tsunamis as a result of the eruption of an underwater volcano are formed in much the same way as during an earthquake. Since as a result of a volcanic eruption, explosions occur, and when they have great power, they are also ways to cause large and long waves, i.e. tsunamis.
What are tsunamis?
Scientists divide different types of tsunamis depending on the strength and height of the waves, as well as on the catastrophic consequences that these waves cause. Waves from earthquakes can form both large ones from 10 meters in height, and very small ones - waves of 1-2 meters. The farther from the coast, the less destructive effect a tsunami has.
The most destructive tsunamis occur when the epicenter of an earthquake is close to the coast, with an earthquake magnitude of 6.5 on the Richter scale. And with a small earthquake somewhere in the center of the ocean, they can cause waves from 1 meter, which are not dangerous even for ships and liners that are nearby. This is because the tsunami gains its strength and power as it approaches the shore. That is why, being in seismically dangerous coastal zones, you need to know the main signs of a tsunami.
Signs of a tsunami:
- - earthquakes - the more intense the tremors, the stronger the wave will be;
- - a sharp ebb - the farther the sea and ocean coast go deeper, the higher and more powerful the wave will be.
What regions are seismically dangerous zones where a tsunami can form?
Most often, tsunamis form on the coasts of the Pacific Ocean, since more than 80% of the active volcanoes of our planet are located in its waters, and 80% of all earthquakes occur at the bottom of this ocean. Dangerous zones include the western coast of Japan, Sakhalin Island, the coast of Peru, India, Australia, Madagascar.
gender of nouns
6th grade
Verification work number 4.
Target:
- Reveal the skills to determine the classifying feature of a noun - gender.
- To check the skills of word analysis at the level of phonetic, morphemic, morphological.
- Punctuation skills.
Dictation.
"Tsunami"
Tsunami is a Japanese word. These ominous waves, which are often preceded by a sudden ebb, claim more human lives than all other maritime disasters.
A grandiose spectacle - a real tsunami, a single wave, born of a large earthquake.
At first this wave is very high, then it moves away from the place of birth and quickly becomes lower and lower, and in the open ocean it can hardly be distinguished from other waves.
Ships, having met a tsunami, often do not notice anything, but its peaceful appearance is deceptive: the wave carries colossal force.
Having reached the coastal shallows, it suddenly grows to a dizzying height. The sea emerges from the coast and moves towards the land like a huge wall.
At the top of the blue-gray wall, white breakers boil.
Then the wall collapses, pouring millions of tons of salt water into piers, port facilities, and houses, and entire villages.
Assignments to the text.
- Have you ever heard of a tsunami?
What is a tsunami?
Express your attitude to this phenomenon of nature. (3 p.)
- Determine the gender of the indeclinable word "tsunami".
How did you do this? (2 p.).
- Give an example of an indeclinable word.
What, in your opinion, is the reason for this phenomenon?
Explain. (3 p.).
- What do you know about common nouns?
Give an example, explain the reason for this grammatical phenomenon. (3p.),
- Which nouns do not have gender differences? (2 p.)
- Find a sentence with a dash and explain its statement. (3 p.).
- Underline the grammar in this sentence.
How is it expressed? (2 p.).
- Explain the spelling of the words:
Colossal, grows, millions, coastal, blue-gray, salty.
- Take the words apart:
Preceded by, earthquake, removed, dizzying, harbor.(3 p.).
Grammar assignment scale.
24 – 22 p…………………………………………”10”
21 – 20 p…………………………………………”9”
19 - 18 p……………………………………… "8"
17 - 16 p………………………………………. "7"
15 - 13 p………………………………………. "6"
12 - 11 p……………………………………….. "5"
10 - 8 p…………………………………………. "4"
7 - 6 p……………………………………………. "3"
5 - 4 p……………………………………………. "2"
3 - 1 p……………………………………………. "1"
Tsunami word
The word tsunami in English letters (transliteration) - tsunami
The word tsunami consists of 6 letters: a and m n u ts
Meanings of the word tsunami. What is a tsunami?
Tsunami (translated from Japanese means "high wave in the bay") - long waves generated by a powerful impact on the entire water column in the ocean or other body of water.
Encyclopedic Fund of Russia
Tsunamis, huge sea waves associated mainly with underwater earthquakes, but sometimes arising from volcanic eruptions on the ocean floor, which can cause the formation of several waves ...
Encyclopedia Around the World
Tsunami tsunamis are sea waves of very large length that occur during strong underwater and coastal earthquakes, as well as during volcanic eruptions or large rockfalls from a coastal cliff.
Geographic Encyclopedia
Tsunamis are giant waves generated by earthquakes, whose epicenter is under the ocean floor.
Near the coast, the height of a tsunami can reach 10–30 meters and move towards the coast at a tremendous speed.
Japan from A to Z. - 2009
"Tsunami 3D"
What is a tsunami
Bait is a thriller film directed by Kimble Randall. World premiere - September 6, 2012, premiere in Russia - September 27, 2012. The film takes place in a small town in Australia, located on the coast of the ocean.
en.wikipedia.org
TSUNAMI (TSUNAMI)
TSUNAMI (TSUNAMI) - huge, destructive wave forces that occur when a local change in the water level during underwater earthquakes.
Their propagation speed is 400-800 km/h. The height when approaching the coast reaches 15-30 m or more.
Geological dictionary. — 1978
Tsunami deposits
Tsunami deposits are accumulative deposits left on coasts after exposure to tsunami waves.
From the tsunami deposits, you can restore such wave parameters as height (runup) ...
en.wikipedia.org
Attention, tsunami!
"Attention, tsunami!" - Soviet adventure film of 1969. Seven sailors serve at a remote warning post located in the Pacific Ocean.
One day, a tsunami hits the island. A giant wave destroys the bunker.
en.wikipedia.org
ATTENTION, TSUNAMI!, USSR, Odessa Film Studio, 1969, b/w, 82 min. Heroic film story. Remote warning post in the Pacific Ocean. Seven sailors carry out their service, the peaceful course of which is interrupted by the tsunami that hit the island.
Film Encyclopedia. — 2010
Tsunami Strength Scale
The tsunami strength rating scale is a four-point scale for assessing the strength (intensity) of a tsunami by their impact on ground objects and by wave height (M).
Proposed by K. Iida and A. Imamura Moderate tsunami…
Dictionary of terms MChS. — 2010
Earthquake and Tsunami of Meiji Sanriku (1896)
The Meiji Sanriku earthquake and tsunami is one of the most devastating natural disasters in Japanese history. An earthquake of magnitude 7.2 on June 15, 1896 created a tsunami with a higher magnitude of 8.2…
en.wikipedia.org
Russian language
Tsunami station, -i.
Orthographic dictionary.
Tsunamis are very long sea waves that occur during strong underwater and coastal earthquakes, as well as during volcanic eruptions or large rockfalls from a coastal cliff.
Geographic Encyclopedia
Usage examples for tsunami
No tsunami warning was issued after the earthquake.
The declared threat of a tsunami on the sea coast of Sakhalin was subsequently removed.
developed a tsunami barrier system that automatically responds to wave impacts.
Information about the victims on the territory of the Russian Federation has not yet been received, as well as about the threat of a tsunami.
The first performances of the group took place in April 2011 in Japan, shocked by the earthquake and tsunami.
tsunami- an incredibly dangerous phenomenon of nature. Terrible consequences make you feel out of place. But as they say, you need to know your enemy personally, so learn more about this evil nature:
The most at risk from tsunamis are: California, Hawaii, Oregon and Washington. Hawaii is the highest risk and has about 1 tsunami per year and a dangerous tsunami every 7 years.
Alaska was hit by an extremely strong earthquake. This triggered a tsunami wave that was very destructive southeast of 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 expensive tsunami for the western United States and Canada.
Scientists have found that the impact of a moderately large asteroid (approximately 5-6 km in diameter) in the middle of the Atlantic Ocean will create a tsunami that will travel two-thirds of the United States. Coastal cities will destroy such a tsunami.
Nuclear explosions can create a tsunami, but so far no test results.
Tsunami is a catastrophic natural phenomenon
In addition, such tests are currently prohibited by international agreements.
What causes a tsunami?
An underwater earthquake or other severe disturbance that causes a sudden increase or decrease in the mass of water over the affected area.
This sudden flow of water creates a series of strong waves.
The most common causes of tsunamis are underwater earthquakes, which cause significant changes in the ocean floor and the movement of large amounts of water.
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 meteor impacts in the ocean, large landslides near coasts, materials from volcano eruptions, or the formation of landslides. The consequences of a tsunami caused by such factors are usually localized.
More than 75 percent of tsunamis are associated with underwater earthquakes.
Where do tsunamis occur??
Most tsunamis occur in the Indian and Pacific Oceans.
Areas of the Pacific Ocean are frequent earthquakes. This border is known as the "ring of fire". There are two main subduction zones in the Indian Ocean that can also create tsunamis.
Earthquakes in the subduction region are the most common source of destructive tsunamis. These earthquakes are formed when two tectonic plates meet, one under the other. The dip plate extends to the top plate, causing a bend.
The top plate returns to its original position, thereby moving the sea water.
In December 2004, an earthquake off the coast of Indonesia caused the sea surface, such as a tsunami, to move away from the epicenter 10 minutes after the event.
In this figure, the red arrows indicate the direction in which the top plate is deformed by pulling and lowering the bottom plate.
Tsunami can really move!
- In deep ocean waters, waves are created with long waves, but usually no more than one meter in height.
Tunisian waves can be hundreds of miles long and travel very fast and for long distances without losing much of their energy.
- You can see a mini tsunami if you throw a large object into the water.
- Tsunamis on the high seas can travel at a speed of 950 kilometers per hour (that is, the speed of a passenger plane).
The tsunami loses speed as it approaches the ground, but does not lose much of its energy.
What is the size of a tsunami?
- In the open ocean, tsunami waves are very difficult to see. However, as the tsunami wave approaches the ground and goes to a lower depth, the leading edge of the wave slows down and moves back in the waves at the initial speed.
This causes the water to crash into the pile and causes the wave height to increase. This process is known as "shallow water". When a wave hits the floor, it can behave like a series of surfs or just a powerful wave.
- The tremendous energy of the waves can cause a large amount of water to flow into the depths, far beyond the coastal zone.
- Some of the largest tsunami waves were generated by the Krakatoa volcano in 1883.
The tsunami reached a height of 37 m. The tsunami reached a height of 64 m or more in 1737 (its influence fell at Cape Lopatka, in northeastern Russia).
- Tsunami waves are different from ordinary waves! Normal waves caused by wind and water moving near the surface.
In a tsunami, all the water moves from the surface to the bottom of the ocean, which is caused by the movements of water (earthquakes are the cause of this). In the open ocean, tsunamis create little traffic and a great threat to shipping.
- When a tsunami reaches the coast, its wavelength is over 100 km.
A tsunami can last several hours or even days, depending on the location. This is fundamentally different from the waves we saw 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 strip the sand of an entire beach, knock down trees, and crush a building.
- People and boats are powerless against the power of the tsunami. The amount of water generated by a tsunami can flood vast areas of normal land.
The most famous tsunami in recent times:
- Solomon Islands April 2, 2007
The earthquake struck in shallow water early in the morning and was soon followed by a tsunami. The waves were up to 10 m high. More than 50 deaths were reported, while thousands of people were left homeless. There are tsunami warnings in Australia and Alaska 15 minutes after the earthquake.
At 6:49 a.m., the tsunami, which caused extensive damage to property and the natural environment, triggered a magnitude 8.0 earthquake and caused the deaths of more than 100 people.
The cause is an earthquake with a magnitude of 8.8.
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 movement between the plates in the eastern Pacific and the South American planks. The first waves broke about 34 minutes after the earthquake. Buildings were severely damaged and more than 200 people died.
- 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 were very fast through the villages in the Aitape region. Over 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 quake that caused it was just west of the Indonesian island of Sumatra and measured 9.0 on the same Richter scale, the world's largest quake in 40 years. The death toll in March 2005 was over 273,000, many of whom are missing.
And here is a series of incredible videos:
Tsunami Thailand 2004
Key words in 2017: Haip, Zashchvar and Eshkere!
Tsunami - what is it? Definition, i.e. translation
tsunami(emphasis on "a") it's a super heavy wave, which usually occurs as a result of a strong underwater earthquake or volcanic eruption.
What is a tsunami, photography and photography of a tsunami. Causes and symptoms of a tsunami
The word "tsunami" is Japanese, composed of "tsu" meaning "bay" and "nas" meaning "wave". With their destructive power, tsunamis can be compared to the impact of a nuclear explosion. Often the effects of an earthquake are much less obvious than the damage caused by a tsunami.
There are examples of the deaths of thousands of people caused by the tsunami, of which the last one came to Southeast Asia in 2004 and claimed the lives of 280,000 people.
fix / update
Do you know where this word comes from? tsunami in simple words, its translation and its meaning.
Please share the link "What is a tsunami?" With friends:
© 2018 Site of new and well-remembered words What is it-such.ru
Add word | | Help the project
In the depths of the bowels of the Earth, certain processes are constantly taking place, and they equally affect both the land areas and part of the crust under the bottom of the global ocean.
Tectonic plates shift, layers collide causing vibrations, underground volcanoes erupt. Underwater earthquakes do not go unnoticed: these phenomena cause huge waves, often reaching the continents. These waves are called tsunami- translated from Japanese, the term means "a giant wave that came into the harbor"
.
The water column, which comes into motion as a result of the vibrations of the seabed, is practically harmless away from land. But the closer the wave moves to the shore, the more power it acquires, and the higher its crest becomes. The lower layers of water, passing along the bottom and meeting resistance, increase the energy of the upper layers even more.
A tsunami can move at speeds up to 800 kilometers per hour, while the wave height is often ten, and twenty, and even thirty meters. This mass of water, falling on the shore, destroys everything in its path, throwing debris many kilometers deep into the mainland. The danger of a tsunami also lies in the fact that this is not a single wave: there can be up to a dozen waves in total, with the third and fourth being the most dangerous.
But a tsunami can also look not like waves, but like a series of strong ebb and flow rapidly replacing each other, which carries no less danger.
Causes of a tsunami
Up to 7% of all tsunamis are caused by landslides, when huge blocks of earth, rocks or ice fall into the water. In 1958, in Alaska, such a landslide led to the formation of a wave 524 meters high. 
Underwater landslides in river deltas are also dangerous. Landslide tsunamis occur regularly in Indonesia and lead to the appearance of a twenty-meter tsunami. Another 5% of cases occur in the eruptions of underwater volcanoes. Human activities can also lead to the appearance of a tsunami - for example, testing of deep weapons.
Up to 85% of all cases when tsunamis were recorded are associated with. At the same time, the ocean floor shifts vertically, and the surface of the water begins to move, trying to return to its previous level. Tsunamis are mainly generated by earthquakes with sources located close to the surface.
During earthquakes, surface waves, called local tsunamis, radiate from the vertical shift. The height of such waves can reach thirty meters. At the same time, underwater waves diverge from the epicenter, which pass through the entire water column, from the bottom to the surface, and move at a speed of 600 to 800 kilometers per hour.
With a decrease in the depth of the ocean, the energy of such a wave is concentrated closer and closer to the surface, as a result, such distant tsunamis fall on the coast. A remote tsunami can cross the Pacific Ocean from end to end in a day, reaching from the coast of Chile to the islands of Japan.
Moreover, it is almost impossible to notice such a wave in the ocean - with a length of 200-300 kilometers, it has a height of up to a meter. This is the main insidiousness of the tsunami.
How do you know when a tsunami is coming?
An earthquake in any case can become a tsunami harbinger for coastal regions. Sometimes, before the arrival of a large wave, a sharp ebb is observed near the coast and a wide strip of the seabed is exposed, which can last from several minutes to half an hour. 
Animals show increased anxiety before the arrival of the tsunami, trying to climb to elevated places.
What to do if you are in a tsunami area?
The most dangerous areas from this point of view are the coast, harbors, bays with a height of no more than 15-30 meters above sea level. If you are in such an area and expect a tsunami to come ashore soon, keep paperwork, a minimum supply of food and belongings packed in case of an emergency evacuation.
In advance, it is worth looking after the hills, tall buildings where one could climb in order to avoid danger. It is worth remembering that a distance of two to three kilometers from the coast can be considered relatively safe. Since it is impossible to predict the number or frequency of waves, it is better not to approach the coast for two to three hours after the last wave arrived.
Knowing these simple rules could have saved many lives during the 2004 Southeast Asian tsunami. Then dozens of people wandered the shallows after a sharp ebb, collecting shells and fish. Hundreds more after the first wave of the tsunami returned to the coast to check if their houses were intact, not suspecting that the first wave would come after the next.
The most terrible tsunami of our century
In 2004, trouble came to Southeast Asia. At the end of December, an earthquake of magnitude over 9 hit the Indian Ocean. The tsunami passed through Indonesia, Sri Lanka, Thailand and the coast of Africa. More than 235 thousand people died. The situation was aggravated by the fact that at this time of the year thousands of tourists come to Asian countries to celebrate the New Year on the warm sea. The tsunami destroyed a lot of resort regions in several countries. 
In March 2011, a powerful earthquake hit Japan, causing a 40-meter tsunami. The element brought the death of almost 16 thousand people, more than seven thousand are still considered missing. The tsunami and earthquake destroyed the Fukushima-1 nuclear power plant, and people are still dealing with the consequences of this accident.
18.07.2018 20:16
1673
A tsunami is a wave that reaches very large sizes. It appears far in the ocean and moves towards the shore at high speed. The word tsunami means "wave in the harbor" in Japanese. The Japanese name came from the fact that Japan is most often affected by this natural phenomenon.
There are several reasons for these terrible and dangerous waves. Most often, tsunamis occur as a result of underwater earthquakes. At the same time, the water level rises sharply due to the displacement of the seabed. Unlike ordinary waves, when a tsunami occurs, the entire water column is involved, and not just the surface of the sea.
In addition to underwater earthquakes, tsunamis can cause landslides and underwater volcano eruptions.
The incident that led to the occurrence of a tsunami due to a landslide occurred in Alaska in 1958. Huge masses of earth and ice fell into the water from a great height. As a result, a giant wave was formed, the height of which reached 500 meters near the shore!
When an underwater volcano erupts, an explosion occurs, which also contributes to the oscillation of the water and the formation of large waves.
If you guys lightly touch a glass or bucket filled with water, you will see how small ripples form on the water surface. The same effect occurs when a tsunami appears, only the strength of the wave is much greater.
A tsunami moves at a speed of 50 to 1000 km/h. Its height can reach 50 meters or more! The closer the wave approaches the shore, the larger it becomes. This is due to the fact that the coast is shallower. The consequences of this natural disaster are dire. Tsunami waves hit coastal areas with terrible force and demolish everything in their path.
To combat the elements in some countries, including Russia, tsunami warning services have been created. They study the situation of seismic activity (the danger of an earthquake) and, in the event of a tsunami, notify the population about this so that people can get away from the sea to a safe distance.
Most often, tsunamis occur in the waters of the Pacific Ocean. Many underwater volcanoes are concentrated at its bottom and earthquakes occur in these places.
At the end of December 2004, one of the strongest earthquakes in the last half century occurred near the island of Sumatra, located in the Indian Ocean. Its consequences turned out to be catastrophic: due to the displacement of the lithospheric plates, a huge fault was formed, and a large amount of water rose from the ocean floor, which, at a speed reaching one kilometer per hour, began to move rapidly throughout the Indian Ocean.
As a result, thirteen countries were affected, about a million people were left without a "roof over their heads", and more than two hundred thousand died or went missing. This disaster turned out to be the worst in the history of mankind.
Tsunamis are long and high waves that appear as a result of a sharp displacement of the lithospheric plates of the ocean floor during underwater or coastal earthquakes (the length of the shaft is from 150 to 300 km). Unlike ordinary waves, which appear as a result of a strong wind (for example, a storm) affecting the water surface, a tsunami wave affects water from the bottom to the surface of the ocean, which is why even low-lying water can often lead to disasters.
Interestingly, these waves are not dangerous for ships in the ocean at this time: most of the agitated water is in its bowels, the depth of which is several kilometers - and therefore the height of the waves above the water surface is from 0.1 to 5 meters. Approaching the coast, the back of the wave catches up with the front, which at this time slows down slightly, grows to a height of 10 to 50 meters (the deeper the ocean, the larger the shaft) and a crest appears on it.
It should be taken into account that the impending shaft develops the highest speed in the Pacific Ocean (it ranges from 650 to 800 km/h). As for the average speed of most waves, it ranges from 400 to 500 km / h, but cases have been recorded when they accelerated to a speed of a thousand kilometers (the speed usually increases after the wave passes over a deep trench).
Before crashing on the coast, the water suddenly and quickly moves away from the coastline, exposing the bottom (the further it retreated, the higher the wave will be). If people do not know about the approaching elements, instead of moving as far as possible from the coast, on the contrary, they run to collect shells or pick up fish that did not have time to go into the sea. And just a few minutes later, a wave that arrived here at great speed does not leave them the slightest chance of salvation.
It must be borne in mind that if a wave rolls on the coast from the opposite side of the ocean, then the water does not always recede.
Ultimately, a huge mass of water floods the entire coastal line and goes inland to a distance of 2 to 4 km, destroying buildings, roads, piers and leading to the death of people and animals. In front of the shaft, clearing the way for water, there is always an air shock wave, which literally blows up buildings and structures that are in its path.
It is interesting that this deadly natural phenomenon consists of several waves, and the first wave is far from the largest: it only wets the coast, reducing the resistance for the waves following it, which often do not come immediately, and at intervals of two to three hours. The fatal mistake of people is their return to the shore after the departure of the first attack of the elements.
Reasons for education
One of the main reasons for the displacement of lithospheric plates (in 85% of cases) are underwater earthquakes, during which one part of the bottom rises and the other falls. As a result, the ocean surface begins to oscillate vertically, trying to return to the initial level, forming waves. It is worth noting that underwater earthquakes do not always lead to the formation of a tsunami: only those where the source is located at a small distance from the ocean floor, and the shaking was at least seven points.
The reasons for the formation of a tsunami are quite different. The main ones include underwater landslides, which, depending on the steepness of the continental slope, are able to overcome huge distances - from 4 to 11 km strictly vertically (depending on the depth of the ocean or gorge) and up to 2.5 km - if the surface is slightly inclined.
Large waves can cause huge objects that have fallen into the water - rocks or blocks of ice. Thus, the largest tsunami in the world, whose height exceeded five hundred meters, was recorded in Alaska, in the state of Lituya, when, as a result of a strong earthquake, a landslide descended from the mountains - and 30 million cubic meters of stones and ice fell into the bay.
Volcanic eruptions (about 5%) can also be attributed to the main causes of tsunamis. During strong volcanic explosions, waves are formed, and water instantly fills the vacant space inside the volcano, as a result of which a huge shaft is formed and begins its journey.
For example, during the eruption of the Indonesian volcano Krakatoa at the end of the XIX century. "killer wave" destroyed about 5 thousand ships and caused the death of 36 thousand people.
In addition to the above, experts identify two more possible causes of a tsunami. First of all, it is a human activity. So, for example, in the middle of the last century, Americans made an underwater atomic explosion at a depth of sixty meters, causing a wave about 29 meters high, however, it did not last long and fell, breaking 300 meters as much as possible.
Another reason for the formation of a tsunami is the fall into the ocean of meteorites with a diameter of more than 1 km (the impact of which is strong enough to cause a natural disaster). According to one version of scientists, several thousand years ago, it was meteorites that caused the strongest waves that caused the largest climatic disasters in the history of our planet.
Classification
When classifying tsunamis, scientists take into account a sufficient number of factors of their occurrence, among which are meteorological disasters, explosions, and even ebb and flow, while the list includes low wave surges about 10 cm high.
Shaft strength
The strength of the shaft is measured, taking into account its maximum height, as well as how catastrophic the consequences it caused, and, according to the international IIDA scale, 15 categories are distinguished, from -5 to +10 (the more victims, the higher the category).
By intensity
According to the intensity of the “killer wave”, they are divided into six points, which make it possible to characterize the consequences of the elements:
- Waves with a category of one point are so small that they are recorded only by instruments (most do not even know about their presence).
- Double-point waves are capable of slightly flooding the coast, therefore only specialists can distinguish them from fluctuations of ordinary waves.
- The waves, which are classified as three-point, are strong enough to throw small boats onto the coast.
- Four-point waves can not only wash large sea vessels ashore, but also throw them ashore.
- Five-point waves are already acquiring the scale of a catastrophe. They are able to destroy low buildings, wooden buildings, and lead to human casualties.
- As for the six-point waves, the waves that have washed over the coast completely devastate it along with the adjacent lands.
By the number of victims
According to the number of deaths, five groups of this dangerous phenomenon are distinguished. The first includes situations where deaths were not recorded. To the second - waves that resulted in the death of up to fifty people. Shafts belonging to the third category cause the death of fifty to one hundred people. The fourth category includes "killer waves" that killed from a hundred to a thousand people.
The consequences of a tsunami belonging to the fifth category are catastrophic, since they entail the death of more than a thousand people. Typically, such disasters are characteristic of the deepest ocean in the world, the Pacific, but often occur in other parts of the planet. This applies to the disasters of 2004 near Indonesia and 2011 in Japan (25,000 deaths). “Killer waves” were also recorded in history in Europe, for example, in the middle of the 18th century, a thirty-meter shaft collapsed on the coast of Portugal (during this disaster, from 30 to 60 thousand people died).
Economic damage
As for the economic damage, it is measured in US dollars and calculated taking into account the costs that must be allocated for the restoration of the destroyed infrastructure (lost property and destroyed houses are not taken into account, because they are related to the country's social expenditures).
According to the size of losses, economists distinguish five groups. The first category includes waves that did not cause much harm, the second - with losses up to $ 1 million, the third - up to $ 5 million, the fourth - up to $ 25 million.
The damage from the waves, related to the fifth group, exceeds 25 million. For example, the losses from two major natural disasters in 2004 near Indonesia and in 2011 in Japan amounted to about $250 billion. The environmental factor should also be taken into account, since the waves that caused the death of 25 thousand people damaged a nuclear power plant in Japan, causing an accident.
Natural disaster identification systems
Unfortunately, "killer waves" often appear so unexpectedly and move at such a high speed that it is extremely difficult to determine their appearance, and therefore seismologists often fail to cope with the task assigned to them.
Basically, disaster warning systems are built on the processing of seismic data: if there is a suspicion that an earthquake will have a magnitude of more than seven points, and its source will be on the ocean (sea) floor, then all countries that are at risk receive warnings of the approach of huge waves.
Unfortunately, the disaster of 2004 happened because almost all the neighboring countries did not have an identification system. Despite the fact that about seven hours passed between the earthquake and the surging shaft, the population was not warned about the approaching disaster.
To determine the presence of dangerous waves in the open ocean, scientists use special hydrostatic pressure sensors that transmit data to the satellite, which allows you to fairly accurately determine the time of their arrival at a particular point.
How to survive during the elements
If it so happens that you find yourself in an area where there is a high probability of deadly waves, you must definitely remember to follow the forecasts of seismologists and remember all the warning signals of an approaching disaster. It is also necessary to know the boundaries of the most dangerous zones and the shortest roads by which you can leave the dangerous territory.
If you hear a signal warning of approaching water, you should immediately leave the danger area. Experts will not be able to say exactly how much time there is for evacuation: maybe a couple of minutes or several hours. If you do not have time to leave the area and live in a multi-storey building, then you need to go up to the top floors, closing all windows and doors.
But if you are in a one- or two-story house, you must immediately leave it and run to a tall building or climb any hill (in extreme cases, you can climb a tree and cling to it tightly). If it so happened that you did not have time to leave a dangerous place and ended up in the water, you need to try to free yourself from shoes and wet clothes and try to cling to floating objects.
When the first wave subsides, it is necessary to leave the dangerous area, since the next one will most likely come after it. You can return only when there are no waves for about three to four hours. Once at home, check walls and ceilings for cracks, gas leaks, and electrical conditions.
Fundamentals of life safety. Grade 7 Petrov Sergey Viktorovich
5.4. Consequences of the impact of the tsunami
Some facts
On July 17, 1998, a terrible roar shook the idyllic-looking beaches in the north of the island of New Guinea at dusk. This was the only, but, alas, too late warning of the impending cataclysm. In just a minute, the ocean reared up in a more than 10-meter wave, which rolled ashore for almost 50 km. A hitherto unseen ocean monster walked along the coast, as if cutting off everything in its path with a razor. 7 coastal villages were immediately washed clean. More than 2 thousand of their inhabitants were literally crushed by the waves.
Three giant tsunamis hit the coast at the same time, caused by an earthquake, the epicenter of which was in the ocean a few tens of kilometers north of the island. His strength reached 7 points on the Richter scale.
The people who survived the tsunami left the coast in a panic, went into the jungle and, perhaps, will never return to the sea - the shock of what they experienced was too terrible.
The main primary damaging factors of a tsunami are the impact of the wave, the hydrodynamic pressure of the water flow, the air wave that the water mass carries in front of it, flooding and flooding. The destructive power of a tsunami is directly proportional to the speed of the wave reaching the shore.
Secondary tsunami damage factors are very diverse, they cause enormous damage to coastal areas, and can lead to mass death and injury to people.
These include:
? flooding of the area;
? destruction of buildings and structures, roads, pipelines, power transmission and communication lines, other communications, bridges and moorings;
? the beaching of ships and their destruction;
? death of people and animals;
? soil flushing, destruction of agricultural crops;
? fires, soil pollution as a result of the destruction of storage facilities with hazardous substances and facilities where they are used;
? pollution or destruction of drinking water sources;
? the spread of infectious diseases, the emergence of epidemics.
A ship thrown by a tsunami on the roof of a house
In addition to the water flow, the air wave that goes in front of the water shaft also has a destructive effect. It demolishes roofs and houses, breaks doors and windows, injures people.
Tsunamis are especially dangerous for settlements, cities and structures located on low-lying areas of the ocean coast.
Tsunamis act in accordance with the Eastern proverb: "A good-natured whale swayed in the ocean, and a greedy tiger jumped ashore."
