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WONDERS OF NATURE
Tsunami. Nature miracle
What are sea waves? Everyone can easily answer: these are vibrations of the sea surface, sometimes barely noticeable, and sometimes rising by four or five, or even ten meters, shaking and overturning ships and washing away the coast. The reason for them is also well known: the wind. Therefore, they rush at the speed of the wind - twenty to thirty kilometers per hour, although during a hurricane they can accelerate to a hundred. But there are completely different, huge and terrible waves in the ocean. They capture the entire mass of sea water, to the very bottom, and rush at the speed of an airplane: eight hundred kilometers per hour! In Japan, where the sad experience of meeting them is greater than in other countries, the monstrous waves were called the short word tsunami. It means "big wave in the harbor" in Japanese. The wavelength, that is, the distance between the crests, for ordinary wind waves is ten to forty, a maximum of three hundred meters. And a tsunami has a wavelength of three hundred kilometers - a thousand times longer!
There are several reasons for such huge waves. Most often, these are underwater earthquakes that "shake" the entire thickness of the ocean in the area of the epicenter of the cataclysm and send waves in all directions from it. Sometimes tsunamis result from a volcanic eruption, as was the case with the explosion of the Krakatoa volcano in Indonesia. And, finally, a huge wave can hit the shore under the influence of a tropical cyclone or typhoon. In the open sea, tsunamis are almost invisible. The giant wave is so great that the ship, raised on its crest, only after a few minutes will slowly begin to sink. In this case, the lifting height will not exceed one or two meters. Another thing is the coast. Coming out with all its huge mass in shallow water, the tsunami reaches a height of thirty or forty, and sometimes hundreds of meters in narrow bays, washing people and buildings off the coast, throwing ships and boats several kilometers deep into the coast. In 1930, on the island of Madeira, due to an earthquake, a large piece of rock fell into the water from a height of two hundred meters. A wave of fifteen meters high hit the shore, demolishing everything in its path. Four years later, in one of the fjords of Norway, a whole mountain weighing three million tons collapsed into the sea from a half-kilometer height. The tsunami, almost forty meters high, caused by this collapse, threw many fishing boats hundreds of meters from the coast and destroyed the village and the port in the bay. A quarter of a century passed, and a powerful earthquake hit Alaska. In Lituya Bay, about three hundred million cubic meters of rock fell into the water from a height of nine hundred meters. A splash of water, reaching a height of half a kilometer, uprooted all the trees in its path with roots, exposing the shores of the bay to a height of sixty meters. Volcanic eruptions at the bottom of the ocean or on islands can also cause a strong wave. So it was when, at the end of the 1933th century, the volcano island of Krakatoa exploded in the Sunda Strait. The tsunami that arose then claimed the lives of thirty-six thousand people on the islands of Sumatra and Java. A large military vessel - a gunboat - was thrown by a wave into a thicket of a tropical forest three kilometers from the coast. And the volcanic eruption on the Kuril Islands in January XNUMX caused large tsunami waves that flooded the shores with huge blocks of ice. No less trouble is caused by tsunamis formed without the participation of the internal forces of the Earth, for purely meteorological reasons. Huge waves caused by the movement of cyclones and typhoons from sea to land regularly cause widespread destruction and loss of life in the southern states of the United States, the Hindustan Peninsula and the Pacific Islands. Twice in the past half century, such a tsunami hit the city of Indianapolis in the US state of Texas. Each time, they washed away three-quarters of the city, throwing debris from destroyed buildings, and sometimes entire buildings, far inland. And in 1960, in the densely populated country of Bangladesh, located on the shores of the Bay of Bengal, a catastrophic wave formed under the influence of a tropical cyclone destroyed about two hundred cities and villages, destroyed hundreds of ships and brought death to more than fifteen thousand people. It often happens that before the arrival of the tsunami, the sea level drops, the bottom is far exposed and the calm is disturbed only by a small wave, and then suddenly a giant wave comes. At the same time, tsunamis sometimes come one after another, and each next one is higher and stronger than the previous one. There was a time when they came twenty-five times in a row! Sometimes strong flashes of light are seen at a distance of several kilometers, approaching the shore along with the wave. It is the smallest marine organisms that glow with a sharp mixing of water. Over the past two and a half thousand years, more than four hundred tsunamis have been recorded. In reality, there were probably several thousand of them during this time, but information about this has not been preserved. Most often, catastrophic waves were noted in Japan (85 cases), in Indonesia and the Philippines (60 cases), on the Pacific coast of South America (more than fifty cases) and on the Hawaiian Islands (about forty times). In the Atlantic Ocean and, in particular, off the coast of Europe, tsunamis occur less frequently. Devastating tsunamis off the Japanese Islands occur on average every seven years. Waves wash away entire cities, tens of thousands of people die, thousands of ships sink. The last time a major natural disaster hit Japan was in 1964. Then, after the largest earthquake, three consecutive tsunami waves came to the Japanese coast. They washed ashore several large ships, destroyed twenty thousand buildings and washed away more than fifty bridges. Hundreds of people died or were injured. Earthquakes in the South American Andes or off the coast of South America are also accompanied by catastrophic tsunamis. The most significant disaster was noted here in 1960. Then a strong earthquake broke out in the southern part of the continent and lasted ten days. A giant wave devastated the Pacific coast of North and South America, crossed the Pacific Ocean, hit the Hawaiian and Philippine Islands, Australia and New Zealand. Tsunamis were also recorded in Kamchatka and the Kuril Islands - sixteen thousand kilometers from the epicenter of the earthquake! The wave took four days to reach here, but it was still five meters high. Fortunately, the population was warned in advance, and there were no human casualties. In October 1966, a new earthquake in Peru again responded to the Kuril Islands with the arrival of a tsunami. This time, its height was three meters on the islands of Iturup and Kunashir. In fact, these places often suffer from tsunamis. As early as the beginning of the 1923th century, such natural disasters in Kamchatka and the Northern Kuriles were described by the first scientist who visited here - Stepan Krasheninnikov. In the 1927th century alone, these eastern borders of Russia were hit by tsunamis four times: in 1940, 1952, 1952 and XNUMX. At the same time, the height of the waves reached up to fifteen meters. Especially terrible were the consequences of the tsunami in XNUMX, when a formidable wave almost completely destroyed the city of Severe-Kurilsk, causing numerous casualties. In Europe, tsunamis are rare, but still, gigantic destructive waves associated with earthquakes or volcanic eruptions in North Africa, the island of Sicily, Cyprus and Madeira have been repeatedly noted here. At the same time, waves often devastated entire coastal areas. A huge tsunami wave was formed, for example, during the famous Lisbon earthquake in 1775. The sea at first receded far from the coast, and then, in a monstrous shaft, twenty-six meters high, rushed to the coast, penetrating fifteen kilometers deep into the country! The onset of the wave was repeated three times, each time bringing death and destruction. Tens of thousands of people died, and the city of Lisbon, then one of the richest in Europe, turned into a heap of ruins. The tsunami wave was recorded in the south of England, where it reached six meters, and a little later it reached the coast of America and the Antilles. Sometimes washed ashore ships rise for decades on the hills or just in the forest a few kilometers from the coast, reminding residents of the past disaster. An absolutely incredible incident occurred with the English cargo steamer Avenger. In January 1904, this ship was thrown by a tsunami on the island of Chandeleur in the Gulf of Mexico. The steamer stood on dry land for twelve years. Dragging him back into the sea was completely unthinkable. But in July 1916, the island where the ship was standing among the trees was hit by an even stronger tsunami, and the waves carried the ship back to the sea. After that, the Avenger, as if nothing had happened, set sail again. For many centuries, people have been trying to learn how to predict the appearance of a tsunami. But only in the XNUMXth century did science achieve the first successes in this direction. A tsunami warning service now exists in Japan and on the US Pacific coast, in New Zealand and in Russia. To predict a catastrophic wave on the coast, two instruments are used: a seismograph, which signals that tremors have occurred somewhere, and a tide gauge, which records a decrease or rise in sea level. If an earthquake occurred under water and it is known how far from the coast its epicenter is, then it is possible to approximately calculate the time of arrival of the tsunami to the coast of the island or mainland. And tide gauges mounted on floating buoys far from the coast will note the change in water level long before the disaster and transmit a warning radio signal to land. It happens, however, that tremors are recorded, but the tsunami never occurred. Time after time, alarmed people, after two or three false alarms, stop responding to danger warnings. It is here that a formidable wave falls upon the careless inhabitants. It also happens that an earthquake disables tide gauges and the alarm signal does not come ashore. In short, the tsunami warning system is still far from perfect. And more than once, a giant ferocious wave, caused by a mighty natural cataclysm, will sweep along the defenseless shores, sowing death and destruction. Alas, before the complete curbing of the destructive forces of nature, humanity still has a long and difficult way to go. Author: B.Wagner
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