IN Japanese The hieroglyph “tsu” is a bay or bay, “nami” is a wave. Together, both hieroglyphs translate as “wave flooding the bay.” The catastrophic consequences of two tsunamis that hit the Indian Ocean in 2004 and Japan in 2011 clearly demonstrated that reliable protection nothing has been found from this formidable natural phenomenon to this day...
Tsunami - what is it?
Contrary to popular belief, a tsunami is not one gigantic wave that suddenly hits the shore and sweeps away everything in its path. In fact, a tsunami is a series of marine gravity waves of very long length, resulting from the displacement of extended sections of the bottom during strong underwater earthquakes or, occasionally, for other reasons - as a result of volcanic eruptions, giant landslides, asteroid falls, underwater nuclear explosions.
How does a tsunami occur?
The most common cause of a tsunami is vertical movement of the bottom during underwater earthquakes. When part of the bottom sinks and part rises, the mass of water begins to oscillate. In this case, the water surface tends to return to original level- the average level of the ocean - and thus generates a series of waves.
The speed of tsunami propagation at a sea depth of 4.5 km exceeds 800 km/h. But the wave height in the open sea is usually small - less than a meter, and the distance between the crests is several hundred kilometers, so it is not so easy to notice a tsunami from the deck of a ship or from an airplane. In the vast oceans, encountering a tsunami is not dangerous for any ship. But when waves enter shallow water, their speed and length decrease, and their height increases sharply. Near the shore, the wave height often exceeds 10 m, and in exceptional cases reaches 30-40 m. Then the impact of the elements causes colossal damage to coastal cities.
However, tsunami waves of relatively low height often cause enormous destruction. At first glance, this seems strange: why do the seemingly more formidable waves that arise during a storm not lead to similar casualties? The fact is that the kinetic energy of a tsunami is much higher than that of wind waves: in the first case, the entire thickness of the water moves, and in the second, only the surface layer. As a result, the pressure of water splashing onto land during a tsunami is many times higher than during a storm.
One more factor should not be discounted. During a storm, the excitement increases gradually, and people usually manage to move to a safe distance before they begin to face danger. A tsunami always comes suddenly.
Today, about 1000 cases of tsunamis are known, of which more than a hundred had catastrophic consequences. Geographically, the periphery of the Pacific Ocean is considered the most dangerous region - approximately 80% of all tsunamis occur there.
It is impossible to completely protect the coast from a tsunami, although some countries, especially Japan, have tried to build breakwaters and breakwaters in order to reduce the force of the waves. However, there are cases when these structures played a negative role: tsunamis destroyed them, and pieces of concrete picked up by water flows only aggravated the damage on the shore. Hopes for protection from trees planted along the shore were also not realized. To dampen the energy of waves, too large an area of forest plantations is needed, and most coastal cities simply do not have that. Well and narrow strip trees along the embankment cannot provide any resistance to the tsunami.
One of the important measures to protect the population of dangerous regions from destructive waves was the international tsunami warning system created in the Pacific region. 25 states, including Russia, take part in its work. Scientists different countries Based on a comprehensive analysis of strong earthquake zones, they try to determine whether they caused tsunamis in the past, and what the likelihood of tsunamis occurring in the future is. Main Research Center The system, located on the Hawaiian Islands in Honolulu, continuously monitors seismic conditions and surface levels of the Pacific Ocean.
Our country has a tsunami warning service Far East consists of three regional services: Kamchatka, Sakhalin regions and Primorsky Krai. In the Kamchatka region, in particular, there is a tsunami station of the territorial administration for hydrometeorology and monitoring environment and a seismic station of the Institute of Earth Physics of the Russian Academy of Sciences.
The most destructive tsunamis of the past
It is possible that the most catastrophic tsunami event in human history occurred in ancient times, although it has come down to us in the form of myths and legends. Around 1450 BC. An entire civilization perished from a giant wave triggered by the Santorini volcano. 120 km from the volcano is Crete, which at that time was one of the most powerful powers in the Mediterranean. But the tsunami at one point caused colossal damage to the island of Crete, from which the previously prosperous state was never able to recover. It collapsed, and many of its cities were abandoned for two and a half thousand years.
Giant tsunami waves followed the devastating earthquake in Lisbon on November 1, 1755. The source of the earthquake was obviously at the bottom of the ocean. The total number of victims from the waves and earthquake is estimated at approximately 60 thousand people.
In 1883, as a result of a series of eruptions of the Krakatoa volcano in Indonesia, a powerful tsunami was formed, from which the islands of Java and Sumatra suffered the most. Waves up to 40 m high wiped out about 300 villages from the face of the earth, killing more than 36 thousand people. Near the city of Teluk Betung, a Dutch warship, the gunboat Berouw, was thrown 3 km inland and ended up on a mountainside at an altitude of 9 m above sea level. Seismic waves passed two or three times around the Earth, and unusual red dawns were observed for a long time in Europe from the ash thrown into the atmosphere.
The most destructive tsunami of the 20th century hit the coast of Chile on May 22, 1960. The tsunami and the powerful earthquake that generated it, measuring 9.5 on the Richter scale, killed 2,000 people, injured 3,000, left two million homeless, and caused $550 million in damage. The same tsunami killed 61 people in Hawaii, 20 in the Philippines, 3 in Okinawa and more than 100 in Japan. The wave height on Pitcairn Island reached 13 m, on Hawaii - 12 m.
The most unusual tsunami
In 1958, a tsunami was generated in Lituya Bay, Alaska, caused by a giant landslide - about 81 million tons of ice and solid rock fell into the sea as a result of the earthquake. The waves reached an incredible height of 350-500 m - these are the largest waves ever recorded in history! The tsunami washed away all vegetation from the mountain slopes. Fortunately, the shores of the bay were uninhabited, and human casualties were minimal - only two fishermen died.
Tsunami in the Russian Far East
On April 4, 1923, a strong earthquake occurred in the Kamchatka Bay. 15-20 minutes later a wave approached the top of the bay. Two fish factories on the coast were completely destroyed, and the village of Ust-Kamchatsk was severely damaged. The ice on the Kamchatka River was broken over a distance of 7 km. 50 km southwest of the village, the maximum height of water rise on the coast was observed - up to 30 m.
In Russia, the most catastrophic tsunami occurred on the night of November 4–5, 1952 on the Far Eastern island of Paramushir, where the city of Severo-Kurilsk is located. At about 4 a.m., strong tremors began. Half an hour later the earthquake stopped, and the people who had left their homes returned to their homes. Only a few remained outside and noticed the approaching wave. They managed to take refuge in the hills, but when they went down to inspect the destruction and look for relatives, a second, even more powerful wave of water about 15 m high fell on the city. The captain of one tug stationed in the roadstead of Severo-Kurilsk said that that night the sailors did nothing They didn’t notice, but early in the morning they were surprised by the large amount of garbage and various objects floating around. When the morning fog cleared, they saw that there was no city on the shore.
On the same day, the tsunami reached the shores of Kamchatka and caused serious damage to a number of villages. In total, more than 2,000 people died, but in the USSR, until the early 1990s, almost no one knew about the events of that tragic night.
The tsunami that occurred on May 23, 1960, off the coast of Chile, reached the shores of the Kuril Islands and Kamchatka about a day later. The highest level of water rise was 6-7 m, and on the territory of the Khalaktyrsky beach near Petropavlovsk-Kamchatsky - 15 m. In Vilyuchinskaya and Russkaya bays, houses were destroyed and outbuildings were washed into the sea.
Tsunami propagation in Pacific Ocean(the most destructive waves are black and red) after the 1960 earthquake. Map prepared by the US National Oceanic and Atmospheric Administration (NOAA)
Indian Ocean disaster (2004)
After an earthquake measuring about 9 on the Richter scale with an epicenter in the northern part of the island of Sumatra in Indonesia, which occurred on the night of December 26, 2004, a powerful tsunami covered the Indian Ocean. More than 1000 km of fault line resulting from the movement of large strata earth's crust at the bottom of the ocean, generated a huge release of energy. Waves hit Indonesia, Sri Lanka, India, Malaysia, Thailand, Bangladesh, Myanmar, Maldives and Seychelles and reached Somalia, located 5 thousand km from the epicenter of the earthquake. More than 300 thousand people became victims of the tsunami, including foreign tourists from many countries who were vacationing in Indonesia and Thailand in those days. Most of the dead were in Indonesia (more than 180 thousand) and Sri Lanka (about 39 thousand).
Such numerous casualties are largely explained by the lack of basic knowledge among the local population about the impending danger. So, when the sea retreated from the shore, many locals and tourists remained on the shore - out of curiosity or out of a desire to collect the fish remaining in the puddles. In addition, after the first wave, many returned to their homes to assess the damage or try to find loved ones, not knowing that others would follow the first wave.
Tsunami in Japan (2011)
The tsunami was caused by a strong earthquake of magnitude 9.0-9.1 that occurred on March 11, 2011 at 14:46 local time (8:46 Moscow time). The center of the earthquake was at a depth of 32 km, at a point with coordinates 38.322° N. 142.369°E east of the island of Honshu, 130 km east of the city of Sendai and 373 km northeast of Tokyo. In Japan, the tsunami caused widespread destruction on the east coast. The maximum wave height was observed in Miyagi Prefecture - 10 m. The tsunami flooded Sendai airport, washed away one passenger train, damaged serious damage Fukushima I Nuclear Power Plant. In Sendai alone, the tsunami caused the death of approximately 300 people. The total damage caused to the country's economy amounts to hundreds of billions of dollars.
According to official data, the death toll from the earthquake and tsunami was 15,892 people, with another 2,576 people listed as missing. 6,152 people were seriously injured. According to unofficial data, the number of victims is much higher. According to media reports, 9,500 people are missing in the city of Minamisanriku alone.
Numerous photographic documents paint a truly apocalyptic picture of destruction:
The tsunami was observed along the entire Pacific coast - from Alaska to Chile, but outside Japan it looked much weaker. Hawaii's tourism infrastructure was hit the hardest—about 200 private yachts and boats were wrecked and sunk in Honolulu alone. On the island of Guam, waves tore two US Navy nuclear submarines from their moorings. In Crescent City, California, more than 30 boats were damaged and one person was killed.
According to the Russian Ministry of Emergency Situations, due to the threat of a tsunami on the Kuril Islands, 11 thousand residents were evacuated from coastal areas. The highest wave height - about 3 m - was recorded in the area of the village of Malokurilskoye.
Tsunami in cinema
In the popular genre of disaster films, tsunamis have repeatedly attracted the attention of screenwriters and directors. An example is the feature film “Tsunami” ( South Korea, 2009), frames from which are given below.
In December 2004, a photo of the largest wave in the world spread across all publications around the world. On December 26, an earthquake occurred in Asia, which resulted in a tsunami wave that killed more than 235 thousand people.
The media published photos of the destruction, assuring readers and television viewers that there had never been a big wave in the world. But the journalists were lying... Indeed, in terms of its destructive power, the 2004 tsunami is one of the deadliest. But the magnitude (height) of this wave is quite modest: it did not much exceed 15 meters. The stories are better known high waves, about which you can say: “Yes, this is the biggest wave in the world!”
Record breaking waves
Where are the biggest waves?
Scientists are confident that the highest waves are not caused by earthquakes (they often cause tsunamis), but by ground collapses. This is why high waves are most common:
... And other rogue waves
It's not just giant waves that are dangerous. There is a scarier variety: single rogue waves. They come out of nowhere, their height rarely exceeds 15 meters. But the pressure they exert on all objects encountered exceeds 100 tons per centimeter (ordinary waves “press” with a force of only 12 tons). These waves are practically not studied. We only know that it crushes oil rigs and ships like a sheet of ordinary paper.
Tsunami(Japanese 津波 IPA: where 津 - “port, bay”, 波 - “wave”). Translated from Japanese it means “big wave in the harbor” or simply “wave in the harbor”. Tsunamis are long waves generated by a powerful impact on the entire thickness of water in the ocean or other body of water.
They have spatial scales from several hundred meters to several hundred kilometers. Tsunami wave propagation speed (c) described by the formula Lagrange:
с=√gh,
Where h- depth of the ocean;
g- acceleration of gravity.
Causes of tsunamis.
Tsunamis are not always generated by any one phenomenon; they can be caused by a combination of them. For example, an earthquake and a landslide, a volcanic eruption accompanied by an earthquake and a landslide, and so on.
Most tsunamis are caused by underwater earthquakes(today it is believed that this is the reason that accounts for about 85 % all tsunamis), during which a sharp displacement (raising or lowering) of a section of the seabed occurs. Not every underwater earthquake is accompanied by a tsunami. The tsunami wave that generates is usually an earthquake with a shallow source. The only problem is the lack of ability to 100% recognize such earthquakes, because warning services focus only on magnitude indicators.
Second reason are landslides(near 7% all tsunamis). Once a landslide occurs, it immediately generates a wave. An earthquake can cause a landslide. Underwater landslides most often occur in river deltas.
The third reason are volcanic eruptions (near 5% all tsunamis). Large underwater eruptions have the same effect as earthquakes. Classic example- tsunami generated after the eruption of Krakatoa in 1883. Huge tsunamis from the Krakatoa volcano were observed in harbors around the world and destroyed a total of 5,000 ships and, as a result, killed about 36,000 people.
In the age of use atomic energy A person now has in his hands a means to independently induce tremors, previously available only to nature. Therefore, it should be understood that fourth reason is human activity . Here it should be remembered that in 1946, the United States carried out an underwater atomic explosion with a TNT equivalent of 20 thousand tons in a sea lagoon 60 m deep. The resulting wave at a distance of 300 m from the explosion rose to a height of 28.6 m, and 6.5 km from the epicenter still reached 1.8 m. And, although international treaties currently prohibit underwater testing of atomic weapons, but, as practice shows, such agreements are formal in nature and serve only to personally reassure citizens of adjacent territories in their imaginary safety and comfort.
A small, but not so safe percentage falls on meteorological reasons(such as the fall of a large celestial body) and others potential causes, called in scientific circles as “unknown” (but very dangerous). Meteorological reasons today are a rather poorly understood phenomenon. They are recorded mainly in the Pacific, Atlantic and Indian oceans.
Features of tsunami propagation
Far from the coast, the height of a tsunami is no more than 2-2.5 m, and its length can reach several hundred kilometers. These tsunamis are very gentle and almost imperceptible to ships passing over them.
The speed of a tsunami depends entirely on its depth and can reach speeds of up to 800 km/h. The most interesting thing is that in open ocean tsunamis are invisible, although they move at a speed of 700-800 km/h, but when approaching the shore, the speed noticeably decreases with a significant increase in the height of the approaching wave.
If a tsunami moves towards the shore, then its height, reaching shallow water, begins to increase to 20-30 m, and in some cases can reach 30-60 m. Near the shore itself, the tsunami becomes steeper and higher, reaching its peak point along the entire path of its journey.
This leads to enormous destruction and numerous casualties. Examples of this phenomenon were the coasts of Thailand, Indonesia, India and Sri Lanka during the tsunami of December 26, 2004. in the Indian Ocean, as well as the northeastern part of Japan on March 11, 2011 (the magnitude of the earthquake that generated the tsunami was 9.0 points).
From the point of view of the development of science today, we can say that the height of the tsunami on the coast and the features of movement inland depend on the size of the initial disturbance of sea level, bottom slopes, configuration coastline terrain.
Tsunamis are most dangerous in narrowing bays and straits, as well as in the mouth areas of rivers flowing into the sea. Tsunamis penetrate furthest along river valleys. Examples of such areas are: the Second Kuril Strait, Tuharka Bay on the island of Paramushir, Crab Bay on the island of Shikotan, the mouth of the Kamchatka River and others.
The tsunami threat at any point during the day can rise or fall sharply depending on fluctuations in the tidal level.
The very first harbingers are animals and birds, which, sensing danger, leave their habitats in the period from several hours to several days, or even weeks before the impending disaster. It’s as if our Mother Earth herself is taking care of warning living things about danger through various energy waves captured by animals and birds.
For example, residents of earthquake-prone Japan have been determining the risk of earthquakes by their behavior for hundreds of years. aquarium fish. Thus, on the eve of a tsunami, Japanese catfish literally try to jump out of the aquarium and constantly rush from wall to wall. Repeated observations, including those carried out by scientists from the experimental oceanological laboratory of the Russian Hydrometeorological University, also confirmed that ocean fish also leave coastal waters several hours before the tsunami. Studies have shown that stingrays, carp fish, catfish and crayfish are especially sensitive to changes in electromagnetic fields before natural disasters.
It is no coincidence that biochemist H. Tributsch notes that, shortly before the onset of earthquakes and the subsequent occurrence of tsunamis, a powerful stream of charged particles or ions rushes from the soil surface into the atmosphere, which saturate the air with electricity to the limit, causing increased excitability, nausea, and headaches in people. It is these electrostatic fields that force animals to leave dangerous areas. And a group of German researchers from Tübingen, led by Professor W. Ernst, also discovered a change in the color of leaves of flowers, shrubs and trees several weeks before earthquakes. Such changes can be recorded using space satellites, which will allow people to be warned about danger in advance.
Signs of a tsunami may also include:
- A sudden rapid withdrawal of water from the shore over a considerable distance and drying out of the bottom.
- The occurrence of an earthquake. 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, in order to thus prepare in advance for the arrival of the wave.
- During a storm, only the surface layer of water moves. During a tsunami - the entire thickness of water, from the bottom to the surface.
- A tsunami, as a rule, generates not one, but several waves. The first wave, not necessarily the largest, "wets the surface", reducing resistance for subsequent waves.
- The speed of tsunami waves, even near the shore, exceeds the speed of wind waves. The kinetic energy of tsunami waves is also thousands of times greater.
Consequences of the tsunami.
The consequences of the tsunami are huge human casualties. Human life alone is a priceless gift and gift.
As the first of the seven foundations of AllatRa states, the highest value in this world is human life. And it is very important to protect the life of any person as your own, because although it is fleeting, it gives everyone a chance to increase their main value - their inner spiritual wealth, the only thing that opens the Personality to true spiritual immortality.
The most terrible consequence A tsunami means losing at least one priceless human life.
But, in addition to the loss of life, tsunamis also cause flooding of large coastal areas, salinization and erosion of soils, destruction of buildings and structures, and damage to ships moored near the coast. A tsunami deals a huge blow to the economy of the country in which such a disaster occurs. The economic losses from the tsunami are colossal and amount to truly astronomical sums of money, aimed at eliminating the consequences and restoring the destroyed infrastructure of the region.
An example of this is an event in Japan. According to experts, a year after the earthquake and the resulting tsunami, the damage to Japan is estimated at 210.00 billion US dollars. This tsunami not only became the most expensive natural disaster in history. But it also destroyed 128,582 and partially destroyed 243,914 buildings. About 320,000 people lost their homes and 15,848 lost their lives. Another 3,305 people are considered missing.
What to do if a tsunami occurs?
Care must be taken to ensure that the documents minimum required things and products were always at hand.
You should discuss with family members a meeting place after a disaster, consider evacuation routes from a dangerous coastal area, or identify places for rescue if evacuation is not possible. These may be local hills or high capital buildings. You need to move to them by the shortest route, avoiding low-lying places. A distance of 2-3 km is considered safe. from the shore.
It is important to understand that when tsunami warning signs, tremors are observed, or local tsunami warnings are issued, the time to rescue can be measured in minutes. Therefore, it is necessary to act instantly, remaining collected and as calm as possible.
The occurrence of distant tsunamis is detected by warning systems and the forecast is communicated by radio and television. Such messages are preceded by the sound of sirens.
The number, height of waves, as well as the interval between them is impossible to predict. Therefore, after each wave it is dangerous to approach the shore for 2-3 hours. It is advisable to use the gap between waves to find the safest place.
Any earthquake felt on the seashore should be considered a tsunami hazard.
You cannot go close to the shore to watch the tsunami. It is believed that if you see a wave and are in a low-lying place, it is too late to save yourself.
Compliance with these simple rules of behavior and knowledge of tsunami precursors could reduce the number of victims of the Indian Ocean tsunami in 2004. After all, according to eyewitnesses (this can also be seen in the recorded videos), many people used such a harbinger of a tsunami as the low tide before the arrival of the wave to walk along the seabed and collect sea animals, shells, as well as various things left after the rapid “leaving” of the water during low tide
With the right behavior, the number of saved people could reach tens of thousands.
It is necessary to pay attention to the development of science in the field of observation of animals, birds, fish and the entire surrounding world, so that, together with these harbingers of upcoming changes, we are fully armed and informed as much as possible about the impending future.
It is important to understand that in order to reduce damage from the consequences of a tsunami, it is necessary to take great responsibility for construction, which should be carried out outside the tsunami impact zone. If this is not possible, build buildings so that they absorb impacts on their short side, and/or place them on strong columns. In this case, the wave will freely pass under the building without causing damage to it.
If there is a threat of a tsunami, ships moored near the shore must be taken out to the open sea.
You should pay attention and your understanding that there are no state territories on planet Earth.
It is people themselves, by desire and choice, who share one indivisible planet, one whole and the only one, dividing them all possible ways- whatever imagination and greed is enough for. All this division is just an appearance for the mind and an outlet for the ego, especially the imaginary owners of artificially created territories in distant and not so distant history. We are all Earthlings. We are all inhabitants of the Earth. And it doesn’t really matter what complexion each of us has, where we live or what we believe.
It is important to support each other, lend a helping hand to your neighbor, and take care of the people around you in every possible way. And then no disaster will become an obstacle in the life of every person, but will only be a temporary task, overcoming which with joint efforts will be easy and least painful for the people “affected” by the disaster.
At the end of December 2004, one of the most powerful 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 lithospheric plates a huge rift formed, and with ocean floor rose a large number of water, which, at a speed reaching one kilometer per hour, began to rapidly move 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 were killed or missing. This disaster turned out to be the worst in human history.
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 that appear as a result of the impact of a strong wind on the water surface (for example, a storm), a tsunami wave affects water from the bottom to the surface of the ocean, which is why even low-level water can often lead to disasters.
It is interesting that for ships located in the ocean at this time, these waves are not dangerous: most of agitated water is located in its depths, the depth of which is several kilometers - and therefore the height of the waves above the surface of the water ranges 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 swell) and a crest appears on it.
It should be taken into account that the approaching 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 there have been cases when they accelerated to speeds of up to a thousand kilometers (the speed usually increases after the wave passes over a deep-sea trench).
Before hitting the coast, the water suddenly and quickly moves away from the shoreline, exposing the bottom (the further it recedes, the higher the wave will be). If people do not know about the approaching disaster, instead of going as far from the shore as possible, they instead run to collect shells or pick up fish that did not have time to go to sea. And just a few minutes later, a wave that arrived here at enormous speed does not leave them the slightest chance of salvation.
It must be taken into account that if a wave rolls onto the coast from the opposite side of the ocean, the water does not always recede.
Ultimately, a huge mass of water floods the entire coastline 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 the water, there is always an air shock wave, which literally explodes 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 following waves, which often do not arrive immediately, and at intervals of two to three hours. The fatal mistake of people is their return to the shore after the first attack of the elements has left.
Reasons for education
One of the main reasons for the displacement of lithospheric plates (in 85% of cases) is underwater earthquakes, during which one part of the bottom rises and the other sinks. As a result, the ocean surface begins to oscillate vertically, trying to return to entry 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 a short 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 capable of covering enormous 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 be caused by huge objects falling into the water - rocks or blocks of ice. Thus, the largest tsunami in the world, the height of which exceeded five hundred meters, was recorded in Alaska, in the state of Lituya, when, as a result of a strong earthquake, a landslide came down from the mountains - and 30 million cubic meters stones and ice.
The main causes of tsunamis also include volcanic eruptions (about 5%). During strong volcanic explosions, waves are formed, and water instantly fills the vacated 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 in late XIX Art. "rogue wave" destroyed about 5 thousand sea vessels and caused the death of 36 thousand people.
In addition to the above, experts identify two more possible reasons occurrence of a tsunami. First of all, this is human activity. For example, in the middle of the last century, the Americans carried out an underwater atomic explosion at a depth of sixty meters, causing a wave about 29 meters high, although it did not last long and fell, having covered a maximum of 300 meters.
Another reason for the formation of a tsunami is the fall of meteorites with a diameter of more than 1 km into the ocean (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 became the causes of the largest climate disasters in the history of our planet.
Classification
When classifying tsunamis, scientists take into account a sufficient number of factors of their occurrence, including meteorological disasters, explosions and even ebbs and flows, and low wave surges with a height of about 10 cm are included in the list.
By 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, there are 15 categories, from -5 to +10 (the more victims, the higher the category).
By intensity
According to intensity, “rogue waves” are divided into six points, which make it possible to characterize the consequences of the disaster:
- Waves with a category of one point are so small that they are recorded only by instruments (most people do not even know about their presence).
- Two-point waves are capable of slightly flooding the shore, so only specialists can distinguish them from the fluctuations of ordinary waves.
- The waves, which are classified as force three, are strong enough to throw small boats onto the coast.
- Force four waves can not only wash large sea vessels ashore, but also throw them onto the coast.
- Point five waves are already acquiring catastrophe proportions. They are capable of destroying low buildings, wooden buildings, and causing casualties.
- As for force six waves, the waves that wash up on the coast completely devastate it along with the adjacent lands.
By number of victims
By number deaths There are five groups of this dangerous phenomenon. The first includes situations where no deaths were recorded. 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 “rogue waves,” which killed from one 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 typical for the waters of the deepest ocean in the world, the Pacific, but they often occur in other parts of the planet. This applies to the disasters of 2004 near Indonesia and 2011 in Japan (25 thousand dead). “Rogue waves” have also been recorded in history in Europe, for example, in mid-18th century 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 American 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 relate to the country’s social expenses).
Economists distinguish five groups based on the size of losses. The first category includes waves that did not cause special harm, to the second - with losses of up to 1 million dollars, to the third - up to 5 million dollars, to the fourth - up to 25 million dollars.
Damage from waves, classified as group five, exceeds 25 million. For example, losses from two major natural disasters, which occurred in 2004 near Indonesia and in 2011 in Japan, amounted to about 250 billion dollars. It is worth considering environmental factor, as waves that killed 25 thousand people damaged Japan nuclear power plant, causing an accident.
Disaster recognition systems
Unfortunately, rogue waves often appear so unexpectedly and move at such high speeds that it is extremely difficult to determine their appearance, and therefore seismologists often fail to cope with the task assigned to them.
Mainly warning systems natural disaster are based on the processing of seismic data: if there is a suspicion that an earthquake will have a magnitude of more than seven, and its source will be on the ocean (sea) floor, then all countries that are at risk receive warnings about the approach of huge waves.
Unfortunately, the 2004 disaster occurred because almost all surrounding 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 of the approaching disaster.
To determine the presence of dangerous waves in the open ocean, scientists use special hydrostatic pressure sensors that transmit data to a satellite, which allows them to quite accurately determine the time of their arrival at a particular point.
How to survive during a disaster
If it so happens that you find yourself in an area where there is a high probability of deadly waves occurring, you must remember to follow the forecasts of seismologists and remember all the warning signals of an approaching disaster. It is also necessary to find out the boundaries of the most dangerous zones and the shortest roads along which you can leave the dangerous territory.
When 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 to evacuate: it could be a couple of minutes or several hours. If you do not have time to leave the area and live in a multi-story building, then you need to go up to the top floors, closing all the windows and doors.
But if you are in a one- or two-story house, you need to immediately leave it and run to tall building or climb some hill (in as a last resort, you can climb a tree and cling tightly to it). If it so happens that you did not have time to leave a dangerous place and found yourself 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 the walls and ceilings for cracks, gas leaks and electrical conditions.
Once upon a time in 1960 a very powerful earthquake of 9.5 points was recorded, the waves rose 25 meters. As a result, it claimed the lives of about 1,263 people.
Recently in 2004 In the month of December there was another very terrible earthquake. It happened in Indian Ocean, and its magnitude was equal to nine points. It provoked waves of insane strength and their height reached more than 50 meters.
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This tsunami, if we count the victims, became the most global and destructive. It involved Asian countries such as Indonesia, southern India and many others. The number of dead people is shocking because it is equal to 227,898 people. This is only factual information, but many scientists estimate that the tsunami claimed more than 300,000 lives. Because many people were never found, perhaps they were swallowed up by the ocean.
But why did so many people die? This is due to the fact that people simply were not warned about the impending disaster. Well, most of them returned back to their homes, believing that the worst was over. But each time the ocean presented the city residents with more and more huge waves.
Two years ago there was an earthquake in Japan that reached 9 points. Then the waves were 40.5 meters high. On year 2014 it was one of the most large tsunami in terms of the scale of destruction, since 62 towns and several villages fell under it. This tsunami refuted all scientific calculations; it turned out to be much larger than predicted.
The Philippine earthquake plunged into the abyss of darkness around 4,456 people. It was about 8.1 points, and the height was 8.5 meters.
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In 1992 there was another very terrible earthquake that occurred in Indonesia, in the Flores Sea. On that day, it claimed 2,500 lives, its magnitude was 7.8, and the waves reached 26.2 meters.
In 1998 The tsunami killed 2,183 people and occurred in Papua New Guinea. Then it reached 7 points and had waves of 15 meters.
When did the landslide happen? in Alaska in 1958, there was a very powerful tsunami. When great amount ice and earth rocks fell into the water, this provoked a tsunami, the waves of which near the shore reached 500 meters. This wave is considered by everyone to be the largest in the world!
Now it’s already 2016, but nature and its phenomena are still beyond the control of people. And therefore it is necessary to develop science in every possible way and predict the coming catastrophe.
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