The most destructive tsunamis. Data

In terms of the number of victims and destruction, tsunamis are far from the first place among natural disasters on our planet. But they happen quite often. According to statistics, small tsunamis occur four times a year, and the strongest ones, more than 8 meters high, occur once a decade. Photo above KPA/COLLECTION FOTO; ALAMY/PHOTAS

On Sunday morning, November 1, 1755, the residents of Lisbon were preparing to celebrate All Saints' Day. Many were already in the cathedrals, listening to sermons, others were just rushing there. Suddenly, a dull rumble was heard from somewhere underground. Houses began to shake, huge chandeliers in churches tore off from the ceilings and fell directly on parishioners, plaster and stones fell down. In search of salvation, people rushed into the street to look for open space: some rushed to the fields, but most - to the harbor to sail away on boats. A miraculously surviving eyewitness who found himself along with everyone else on the embankment, Reverend Charles Davy, later said that when the tremors subsided, there was complete calm and silence. A few minutes later, a wall of water appeared on the horizon from the ocean, instantly growing to the size of a mountain. It hit the embankment with enormous force, covering people. The monk grabbed hold of a large beam lying on the ground, and this saved his life, since the water receded as suddenly as it had come. Being completely wet, he returned to the city and from there saw a picture of monstrous destruction: the lower part of Lisbon was flooded, and in the harbor, ships were spinning like splinters, some with torn rigging or turned upside down.

It was one of the most destructive tsunamis in human memory, coupled with an earthquake that destroyed most beautiful city Europe, and what was spared by the water element was destroyed by the fire that started.

The danger of a tsunami for people lies in its suddenness, which is why in many cases the tragedy occurs according to a similar scenario. First, an earthquake destroys houses and drives townspeople out into the streets, then there is a lull and a tsunami follows. Those who were lucky enough to escape the first wave begin to return to their homes, thinking that the worst is over, and then the second, and then the third wave hits them. And these repeated tsunamis destroy many more lives, because the water quickly fills the coast, devastated after the first onslaught, and just as quickly recedes, carrying away defenseless people who have nothing to even grab onto.

The largest catastrophic tsunami recent years, caused by an earthquake, occurred on December 26, 2004. Its epicenter was in the Indian Ocean near the island of Sumatra. The earthquake triggered an ocean wave that hit the coasts of several countries South-East Asia, reaching 30 meters in height in places. Almost 300 thousand people have died or are still considered missing.

After this disaster, smaller tsunamis repeatedly disturbed oceanic islands and coasts in the Pacific and Indian oceans. On April 2, 2007, a ten-meter-high swell washed away two coastal villages and inundated the towns of Taro and Gizo in the Solomon Islands. The source of the earthquake was approximately 300 kilometers east of them at a ten-meter depth under the bottom of the Pacific Ocean.

A tsunami hits the shores of Sri Lanka in 2004. Satellite photography. Photo: FOTOBANK.COM/SIPA PRESS

The textbook example of a volcanic eruption causing a tsunami is the eruption of Krakatoa in Indonesia in 1883. A monstrous explosion that shook the ocean floor created a wave 40 meters high, the echoes of which were recorded by instruments in the English Channel between England and France. The tsunami completely destroyed the cities of Marak, Anyer, Tjaringan, and only a tiny part of their population survived the disaster.

Large waves that occur when large blocks of stone or ice fall into the water are also referred to as tsunamis. One of the most devastating events of this kind happened on July 9, 1958 in Alaska. After the earthquake (which in itself did not directly cause the tsunami), part of the glacier with a volume of about 300 million cubic meters fell into Lituya Bay from a height of 900 meters. On the opposite side of the bay, a wave splash 600 meters high appeared. A huge wave swept across the bay, tearing trees off the slopes. At this time, there were three ships in the bay, 10 kilometers from the center of the disaster. One of them was thrown by a wave over the island over the tops of twelve-meter trees and rocks.

Is it possible to find out in advance about the occurrence of a tsunami and warn people? For those caused by earthquakes, a forecast is possible because the speed of the seismic wave is much higher than the speed of the sea. And having recorded a strong shock with a magnitude above 7, seismologists are already raising the question of the possibility of a tsunami. But it will not come to the shore right away. The gain in time can be minutes or even hours - it all depends on the distance from the epicenter of the earthquake. If he ended up on land, then there is no need to fear a tsunami at all. Sometimes strong earthquakes at the bottom of water areas do not generate a tsunami. Only the actual recording of a wave, namely a local rise in ocean or sea level, serves as indisputable confirmation of a tsunami, but, unfortunately, most of the tide gauge points where such measurements are carried out are located near the coasts, which greatly reduces the time available to warn the population about the danger.

The Pacific Tsunami Warning Center was the first in the world to be established - in 1948 after the disaster that occurred two years earlier in the Hawaiian Islands.

The Japanese warning system has been in operation since 1952 and relies on a very dense network of seismic stations. Tsunamis arising on its western coasts and earthquakes in the Sea of Japan pose a particular danger to this country. So, in May 1983, several dozen people died there. The fact is that the warning signal time is 13 minutes, and the first waves approached the shore 9 minutes after the shock, in some areas - after 3 minutes. To avoid future casualties, Japan has created local systems where the possibility of a tsunami is assessed using seismic data at a single point. In the event of an unfavorable forecast in a tsunami-hazardous area, the supply of gas and electricity is automatically turned off, television and radio programs broadcast a warning text, street sirens are turned on and the evacuation of the population begins.

In the USSR, a warning service began to be created after the North Kuril tragedy of 1952. After all, the seismicity of this area is one of the highest in the world. Along the Kuril-Kamchatka island arc there is an extremely active belt earthquakes, as well as a chain active volcanoes about 2000 kilometers long. Unfortunately, this service was liquidated in the 1990s, and now the only advantage over the tsunami danger is the sparse population of the Far Eastern coast.

MINISTRY OF EDUCATION OF THE RUSSIAN FEDERATION

FAR EASTERN STATE ACADEMY

ECONOMY AND GOVERNMENT

DEPARTMENT OF GENERAL AND

HUMANITIES DISCIPLINES

on the topic of Tsunamis and their manifestation in the Pacific Ocean

Plan:

Causes of tsunamis

The distribution of tsunamis is usually associated with areas of strong earthquakes. It is subject to a clear geographical pattern, determined by the connection of seismic areas with areas of recent and modern mountain building processes.

It is known that most earthquakes are confined to those belts of the Earth within which the formation continues. mountain systems, especially young ones belonging to the modern geological era. The purest earthquakes occur in areas close to large mountain systems and depressions of seas and oceans.

In Fig. Figure 1 shows a diagram of folded mountain systems and areas of concentration of earthquake epicenters. This diagram clearly identifies two zones globe, most susceptible to earthquakes. One of them occupies a latitudinal position and includes the Apennines, Alps, Carpathians, Caucasus, Kopet-Dag, Tien Shan, Pamir and Himalayas. Within this zone, a tsunami is observed on the coasts of the Mediterranean, Adriatic, Aegean, Black and Caspian seas and the northern part of the Indian Ocean. The other zone is located in the meridional direction and runs along the shores of the Pacific Ocean. The latter is, as it were, surrounded by underwater mountain ranges, the peaks of which rise in the form of islands (Aleutian, Kuril, Japanese islands and others). Tsunami waves are generated here as a result of gaps between rising mountain ranges and deep-sea trenches descending parallel to the ridges, separating island chains from the sedentary area of the Pacific Ocean floor.

The direct cause of tsunami waves is most often changes in relief that occur during earthquakes ocean floor, leading to the formation of large faults, failures, etc.

The scale of such changes can be judged from the following example. During an earthquake in the Adriatic Sea off the coast of Greece on October 26, 1873, ruptures were noted in the telegraph cable laid at the bottom of the sea at a depth of four hundred meters. After the earthquake, one of the ends of the broken cable was discovered at a depth of more than 600 m. Consequently, the earthquake caused a sharp lowering of a part of the seabed to a depth of about 200 m. A few years later, as a result of another earthquake, a cable laid on a flat bottom was broken again, and its ends found themselves at a depth that differed from the previous one by several hundred meters. Finally, another year after the new tremors, the depth of the sea at the rupture site increased by 400 m.

Even greater disturbances of the bottom topography occur during earthquakes in the Pacific Ocean. Thus, during an underwater earthquake in Sagami Bay (Japan), about 22.5 cubic meters were displaced when a part of the ocean floor suddenly rose. km of water, which hit the shore in the form of tsunami waves.

In Fig. Figure 2a shows the mechanism of tsunami generation as a result of an earthquake. At the moment of a sharp subsidence of a part of the ocean floor and the appearance of a depression on the bottom of the sea, the pod rushes to the center, overflows the depression and forms a huge bulge on the surface. When a portion of the ocean floor rises sharply, significant masses of water are revealed. At the same time, tsunami waves arise on the surface of the ocean, quickly spreading in all directions. Usually they form a series of 3-9 waves, the distance between the crests of which is 100-300 km, the heights when the waves approach the shore reach 30 m or more.

Another reason that causes tsunamis is volcanic eruptions that rise above the sea surface in the form of islands or are located on the ocean floor (Fig. 2b). The most striking example in this regard is the formation of a tsunami during the eruption of the Krakatoa volcano in the Sunda Strait in August 1883. The eruption was accompanied by the release of volcanic ash to a height of 30 km. The menacing voice of the volcano was heard simultaneously in Australia and on the nearest islands of Southeast Asia. On August 27, at 10 a.m., a gigantic explosion destroyed the volcanic island. At this moment, tsunami waves arose, spreading across all oceans and devastating many islands of the Malay Archipelago. In the narrowest part of the Sunda Strait, wave heights reached 30-35 m. In some places, the waters penetrated deep into Indonesia and caused terrible destruction. Four villages were destroyed on Sebezi Island. The cities of Angers, Merak and Bentham were destroyed, forests and railways washed away, fishing vessels abandoned on land at a distance of several kilometers from the ocean shore. The shores of Sumatra and Java became unrecognizable - everything was covered with mud, ash, corpses of people and animals. This disaster brought the death of 36 inhabitants of the archipelago. Tsunami waves spread throughout Indian Ocean from the coast of India in the north to the Cape Good Hope on South. In the Atlantic Ocean they reached the Isthmus of Panama, in the Pacific Ocean they reached Alaska and San Francisco.

Cases of tsunamis during volcanic eruptions are also known in Japan. So, on September 23 and 24, 1952, there was a strong eruption of an underwater volcano on the Meijin Reef, several hundred kilometers from Tokyo. The resulting waves reached Hotidze Island, northeast of the volcano. During this disaster, the Japanese hydrographic vessel Kaiyo-Maru-5, from which observations were carried out, was lost.

The third reason for a tsunami is the fall of huge rock fragments into the sea, caused by the destruction of rocks groundwater. The height of such waves depends on the mass of material that has fallen into the sea and the height of its fall. So, in 1930, on the island of Madeira, a block fell from a height of 200 m, which caused the appearance of a single wave 15 m high.

Tsunami off the coast South America

The Pacific coast within Peru and Chile is prone to frequent earthquakes. Changes occurring in the bottom topography of the coastal part of the Pacific Ocean lead to the formation of large tsunamis. Greatest height(27 m) tsunami waves reached the Callao area during the Lima earthquake in 1746.

If usually the decrease in sea level that precedes the onset of tsunami waves on the shore lasts from 5 to 35 minutes, then during the earthquake in Pisco (Peru) the receding sea waters returned only after three hours, at Santa - even after a day.

Often the onset and retreat of tsunami waves occur here several times in a row. Thus, in Iquique (Peru) on May 9, 1877, the first wave hit the coast half an hour after the main shock of the earthquake, then within four hours the waves arrived five more times. During this earthquake, the epicenter of which was located 90 km from the Peruvian coast, tsunami waves reached the coasts of New Zealand and Japan.

On August 13, 1868, on the coast of Peru in Arica, 20 minutes after the earthquake began, a wave several meters high surged, but soon receded. With an interval of a quarter of an hour, it was followed by several more waves, smaller in size. After 12.5 hours, the first wave reached the Hawaiian Islands, and 19 hours later - the coast of New Zealand, where 25 people became victims. The average speed of tsunami waves between Arica and Valdivia at a depth of 2200 m was 145 m/sec, between Arica and Hawaii at a depth of 5200 m - 170-220 m/sec, between Arica and the Chatham Islands at a depth of 2700 m - 160 m/sec.

The most frequent and powerful earthquakes characterize the area of the Chilean coast from Cape Concepcion to the island of Chiloe. It is known that since the disaster of 1562, the city of Concepcion suffered 12 strong earthquakes, the city of Valdivia during the period from 1575 to 1907 - 7 earthquakes. During the earthquake of January 24, 1939, 1 person died and 7 people were left homeless in Concepción and its surroundings.

Tsunami off the coast of Japan

Tsunamis are usually accompanied by the most powerful, catastrophic earthquakes that occur on the Japanese Islands on average every seven years. Another reason that causes the formation of a tsunami off the coast of Japan is volcanic eruptions. It is known, for example, that as a result of a volcanic explosion on one of the Japanese islands in 1792, rocks with a volume of about 1 cubic meter were thrown into the sea. km. A sea wave about 9 m high, formed as a result of the fall of eruption products into the sea, demolished several coastal villages and killed more than 15 residents.

The tsunami was particularly powerful during the 1854 earthquake, which destroyed Largest cities countries - Tokyo and Kyoto. First, a nine-meter-high wave came ashore. However, it soon flowed away, drying up the coastal area at a great distance. Over the next 4-5 hours, five or six more large waves hit the shore. And after 12.5 hours, tsunami waves, moving at a speed of more than 600 km/h, reached the coast North America in the San Francisco area.

After this terrible disaster, stone walls were erected on some parts of the coast of Honshu to protect the coast from destructive waves. However, despite the precautions taken, during the earthquake of June 15, 1896, the island of Honshu was again severely damaged by devastating waves. An hour after the earthquake began, six to seven big waves, the maximum height of one of which was 30 m. The waves completely washed away the city of Minko, destroyed 1 building and caused the death of 27 people. And 10 years later, during the earthquake of 1906, on east coast country, when the tsunami struck again, about 3 people died.

During the famous catastrophic earthquake of 1923, which completely destroyed the Japanese capital, tsunami waves caused devastation on the coast, although they did not reach particularly large sizes, at least in Tokyo Bay. IN southern regions country, the consequences of the tsunami were even more significant: several villages in this part of the coast were completely washed away, located 12 km south of Yokohama naval base Japan's Yokosuka was destroyed. The city of Kamakura, located on the shores of Sagami Bay, was also severely damaged by sea waves.

On March 3, 1933, 10 years after the 1923 earthquake, a new strong earthquake occurred in Japan, little compared to the previous one. The tremors swept the entire eastern part Honshu Islands. The greatest disasters for the population during this earthquake were associated with the onset of tsunami waves, which engulfed the entire northeastern coast of Honshu 40 minutes after the earthquake began. The wave destroyed the port city of Komaishi, where 1,200 houses were destroyed. A large number of villages on the coast were demolished. Judging by newspaper reports, about 3 people were killed or missing during this disaster. In total, more than 4,500 houses were destroyed by the earthquake and washed away by the waves, and more than 6,600 houses were partially damaged. More than 5 people were left homeless.

Tsunami off the Pacific coast of Russia

The shores of Kamchatka and Kuril Islands. Initial information about catastrophic waves in these places dates back to 1737. The famous domestic traveler - geographer S.P. Krasheninnikov wrote: l... the shaking began and continued in waves for about a quarter of an hour, so strong that many Kamchadal yurts collapsed and the booths fell. Meanwhile, there was a terrible noise and excitement on the sea, and suddenly water surged onto the shore to a height of three fathoms, which, without standing still, ran into the sea and moved away from the shores at a considerable distance. Then the earth shook a second time, the water came in opposite to the previous one, but at low tide it ran so far that it was impossible to see the sea. At the same time, rocky mountains appeared on the bottom of the sea in the strait between the first and second Kuril Islands, which had never been visible before, although earthquakes and floods had occurred before.

A quarter of an hour after all this, the shocks of a terrible earthquake, incomparable in its strength, followed, then a wave thirty fathoms high rushed onto the shore, which still quickly ran back. Soon the water entered its banks, fluctuating at long intervals, sometimes covering the banks, sometimes escaping into the sea.

During this earthquake, massive rocks collapsed, and the incoming wave threw blocks of stone weighing several pounds onto the shore. The earthquake was accompanied by various optical phenomena in the atmosphere. In particular, Abbot Prevost, another traveler who observed this earthquake, wrote that fiery meteors could be seen on the sea, scattered over a wide area.

S.P. Krasheninnikov noticed all the most important features of a tsunami: an earthquake, a decrease in the level of the ocean preceding the flood, and, finally, the onset of huge destructive waves.

Enormous tsunamis on the coasts of Kamchatka and the Kuril Islands took place in 1792, 1841, 1843, 1918. A series of earthquakes during the winter of 1923 caused repeated onsets of catastrophic waves. There is a well-known description of the tsunami on February 4, 1923, when three waves rushed onto the land of the eastern coast of Kamchatka one after another, tore off the coastal ice (fast ice a fathom thick), threw it over the coastal spit, and flooded low places. The ice in a low place near Semyachik was thrown out almost 1 verst 400 fathoms from the shore; at higher elevations the ice remained at a height of three fathoms above the level of the sea. In the sparsely populated areas of the east coast, this unprecedented phenomenon caused some damage and destruction. The natural disaster affected a vast coastal zone with a length of 450 km.

On April 13, 1923, renewed tremors caused tsunami waves up to 11 m high, which completely destroyed the coastal buildings of fish canning factories, some of which were cut off by hummocky ice.

Strong tsunamis were reported on the coast of Kamchatka and the Kuril Islands in 1927, 1939 and 1940.

On November 5, 1952, an earthquake occurred on the eastern coast of Kamchatka and the Kuril Islands, reaching 10 points and accompanied by a tsunami of exceptional consequences, which caused severe destruction in Severo-Kurilsk. It began at 3:57 a.m. local time. At 4 hours 24 minutes, i.e. 26 minutes after the earthquake began, the level of the ocean quickly fell and in some places the water retreated from the shore by 500 m. Then, a section of the Kamchatka coast from Sarychev Island to the Kronotsky Peninsula was hit strong waves tsunami. Later they reached the Kuril Islands, capturing a strip of coast about 800 km long. The first wave was followed by a second, even stronger one. After her arrival on the island of Paramushir, all buildings located no higher than 10 m above the ocean level were destroyed.

Tsunami in Hawaii

The coasts of the Hawaiian Islands are often subject to tsunamis. Over the past half century alone, destructive waves have struck the archipelago 17 times. The tsunami in Hawaii in April 1946 was very powerful.

From the area of the earthquake's epicenter in the area of Nimak Island (Aleutian Islands), the waves moved at a speed of 749 km/h. The distance between the wave crests reached approximately 150 km. A famous American oceanographer who witnessed this natural disaster, F. Shepard noted a gradual increase in the height of the waves that hit the shore at intervals of 20 minutes. The tide gauge readings were successively 4, 5, 2 and 6.8 m above the tide level.

The damage caused by the sudden onset of the waves was very great. Much of the city of Hilo on the island of Hawaii was destroyed. Some houses collapsed, others were carried by water over a distance of more than 30 m. Faces and embankments were cluttered with debris, blocked by barricades of mangled cars; Here and there, abandoned by the waves, towered the macabre hulks of small ships. Bridges and railways were destroyed. On the coastal plain, among the crushed, uprooted vegetation, numerous blocks of coral were scattered, and the corpses of people and animals could be seen. The disaster claimed 150 human lives and caused a loss of 25 million dollars. This time, waves of prices reached the shores of North and South America, but the largest wave was noted near the epicenter - in the western part of the Aleutian Islands. The Skotu-Kap lighthouse, which stood at an altitude of 13.7 m above sea level, was destroyed, and the radio mast was also demolished.

Application

1. Babkov A., Koshechkin B. Tsunami. - Leningrad: 1964

2. Murthy T. Seismic sea waves at prices. - Leningrad: 1981

3. Ponyavin I. D. Waves in prices. - Leningrad: 1965

4. The tsunami problem. Digest of articles. - M.: 1968

5. Solovyov S. L., Go Ch. N. Catalog of tsunamis on the eastern coast of the Pacific Ocean. - M.: 1975

6. Solovyov S. L., Go Ch. N. Catalog of tsunamis on the western coast of the Pacific Ocean. - M.: 1974

A tide gauge is a device that records fluctuations in sea level

6. Sea waves.

The surface of the sea is always moving, even with complete calm. But then the wind blew, and ripples immediately appeared on the water, which turned into waves the faster the stronger the wind blew. But no matter how strong the wind is, it cannot cause waves larger than certain maximum sizes.

Waves generated by wind are considered short. Depending on the strength and duration of the wind, their length and height range from several millimeters to tens of meters (in a storm, the length of wind waves reaches 150-250 meters).

Observations of the sea surface show that waves become strong even at wind speeds of more than 10 m/s, while the waves rise to a height of 2.5-3.5 meters, crashing onto the shore with a roar.

But then the wind turns storm, and the waves reach enormous sizes. There are many places on the globe where very strong winds blow. For example, in the northeastern part of the Pacific Ocean east of the Kuril and Commander Islands, as well as east of the main Japanese island of Honshu in December-January maximum speeds winds are 47-48 m/s.

In the South Pacific, maximum wind speeds are observed in May in the area northeast of New Zealand (49 m/s) and near the Antarctic Circle in the area of Balleny and Scott Islands (46 m/s).

We perceive speeds expressed in kilometers per hour better. So the speed of 49 m/s is almost 180 km/h. Already at a wind speed of more than 25 m/s, waves 12-15 meters high rise. This degree of excitement is rated 9–10 points as a severe storm.

Measurements have established that the height of the storm wave in the Pacific Ocean reaches 25 meters. There are reports that waves up to 30 meters high have been observed. True, this assessment was made not on the basis of instrumental measurements, but approximately, by eye.

In the Atlantic Ocean, the maximum height of wind waves reaches 25 meters.

The length of storm waves does not exceed 250 meters.

But the storm stopped, the wind died down, but the sea still did not calm down. Like the echo of a storm on the sea arises swell. Swell waves (their length reaches 800 meters or more) move over enormous distances of 4-5 thousand km and approach the shore at a speed of 100 km/h, and sometimes higher. In the open sea, low and long swell waves are invisible. When approaching the shore, the speed of the wave decreases due to friction with the bottom, but the height increases, the front slope of the wave becomes steeper, foam appears at the top, and the crest of the wave crashes onto the shore with a roar - this is how the surf appears - a phenomenon equally colorful and majestic, as dangerous as it is. The force of the surf can be colossal.

When faced with an obstacle, the water rises to a great height and damages lighthouses, port cranes, breakwaters and other structures. Throwing stones from the bottom, the surf can damage even the highest and most distant parts of lighthouses and buildings. There was a case when the surf tore a bell from one of the English lighthouses from a height of 30.5 meters above sea level. The surf on our Lake Baikal sometimes in stormy weather throws rocks weighing up to a ton at a distance of 20-25 meters from the shore.

During storms in the Gagra region, the Black Sea eroded and swallowed up a 20-meter-wide coastal strip over 10 years. When approaching the shore, the waves begin their destructive work from a depth equal to half their length in the open sea. Thus, with a storm wave length of 50 meters, characteristic of seas such as the Black or Baltic, the impact of waves on the underwater coastal slope begins at a depth of 25 m, and with a wave length of 150 m, characteristic of the open ocean, such impact begins already at a depth of 75 m.

Current directions affect the size and strength of sea waves. With countercurrents, the waves are shorter but higher, and with countercurrents, on the contrary, the height of the waves decreases.

Near the boundaries of sea currents, waves of unusual shapes, resembling a pyramid, and dangerous whirlpools often appear, which suddenly appear and just as suddenly disappear. In such places, navigation becomes especially dangerous.

Modern ships have high seaworthiness. But it happens that, having traveled many miles across a stormy ocean, ships find themselves in even greater danger than at sea when they arrive in their home bay. The powerful surf, breaking the multi-ton reinforced concrete breakwaters of the dam, is capable of turning even a large ship into a pile of metal. In a storm, it is better to wait until entering the port.

To combat the surf, specialists in some ports tried to use air. A steel pipe with numerous small holes was laid on the seabed at the entrance to the bay. Air under high pressure was supplied into the pipe. Escaping from the holes, streams of air bubbles rose to the surface and destroyed the wave. This method has not yet found widespread use due to insufficient efficiency. Rain, hail, ice and thickets of marine plants are known to calm waves and surf.

Sailors have long noticed that fat poured overboard smoothes the waves and reduces their height. Animal fat, such as whale blubber, works best. The effect of vegetable and mineral oils is much weaker. Experience has shown that 50 cm 3 of oil is enough to reduce disturbances over an area of 15 thousand square meters, that is, 1.5 hectares. Even a thin layer of oil film noticeably absorbs the energy of vibrational movements of water particles.

Yes, that's all true. But, God forbid, we under no circumstances recommend that captains sea vessels Before the voyage, stock up on fish or whale oil in order to then pour these fats into the waves to calm the ocean. After all, things can reach such an absurdity that someone will start pouring oil, fuel oil, and diesel fuel into the sea in order to appease the waves.

It seems to us that the best way to combat waves lies in a well-established weather service, which notifies ships in advance about the expected place and time of the storm and its expected strength, in good navigation and pilotage training of sailors and shore personnel, as well as in the constant improvement of the design of ships for the purpose increasing their seaworthiness and technical reliability.

For scientific and practical purposes, you need to know the full characteristics of the waves: their height and length, the speed and range of their movement, the power of an individual water shaft and the wave energy in a particular area.

The first measurements of waves were made in 1725 by the Italian scientist Luigi Marsigli. At the end of the 18th – beginning of the 19th centuries, regular observations of waves and their measurements were carried out by Russian navigators I. Kruzenshtern, O. Kotzebue and V. Golovin during their voyages across the World Ocean. The technical basis for measurements in those days was very weak; of course, there were no special instruments for measuring waves on the sailing ships of that time.

Currently, for these purposes, there are very complex and precise instruments that are equipped with research vessels that carry out not only measurements of wave parameters in the ocean, but also much more complex scientific work. The ocean still holds many secrets, the disclosure of which could bring significant benefits to all of humanity.

When they talk about the speed of movement of waves, that waves run up and roll onto the shore, you need to understand that it is not the water mass itself that moves. The water particles that make up the wave practically do not move forward. Only the wave form moves in space, and water particles in the agitated sea perform oscillatory movements in the vertical and, to a lesser extent, in horizontal plane. The combination of both oscillatory movements leads to the fact that the water particles in the waves actually move in circular orbits, the diameter of which is equal to the height of the wave. The oscillatory movements of water particles quickly decrease with depth. Precise instruments show, for example, that with a wave height of 5 meters (storm wave) and a length of 100 meters, at a depth of 12 meters the diameter of the wave orbit of water particles is already 2.5 meters, and at a depth of 100 meters - only 2 centimeters.

Long waves, unlike short and steep ones, transmit their motion to great depths. In some photographs of the ocean floor down to a depth of 180 meters, researchers noted the presence of sand ripples formed under the influence of oscillatory movements of the bottom layer of water. This means that even at such a depth, the surface waves of the ocean make themselves felt.

Is it necessary to prove what danger a storm wave poses to ships?

In the history of navigation, there are countless tragic incidents at sea. Small longboats and high-speed sailing ships, along with their crews, perished. Modern ocean liners are not immune to the insidious elements.

On modern ocean ships among other devices and devices that provide safe swimming, pitch stabilizers are used to prevent the ship from getting an unacceptably large roll on board. In some cases, powerful gyroscopes are used for this, in others, retractable hydrofoils are used to level the position of the ship’s hull. Computer systems on ships are in constant communication with meteorological satellites and other spacecraft, telling navigators not only the location and strength of storms, but also the most favorable course in the ocean.

In addition to surface waves, there are also internal waves in the ocean. They form at the interface between two layers of water of different densities. These waves travel slower than surface waves, but can have greater amplitude. Internal waves are detected by rhythmic changes in temperature at different depths of the ocean. The phenomenon of internal waves has not yet been sufficiently studied. It has only been established that waves arise at the boundary between layers with lower and higher densities. The situation may look like this: there is complete calm on the surface of the ocean, but at some depth a storm is raging; along the length, internal waves are divided, like ordinary surface ones, into short and long. For short waves, the length is much less than the depth, while for long waves, on the contrary, the length exceeds the depth.

There are many reasons for the appearance of internal waves in the ocean. The interface between layers with different densities can be thrown out of balance by a moving large vessel, surface waves, or sea currents.

Long internal waves manifest themselves, for example, in this way: a layer of water, which is a watershed between more dense (“heavy”) and less dense (“light”) water, first rises slowly, for hours, and then suddenly falls by almost 100 meters. Such a wave is very dangerous for submarines. After all, if a submarine sank to a certain depth, it means it was balanced by a layer of water of a certain density. And suddenly, unexpectedly, a layer of less dense water appears under the hull of the boat! The boat immediately falls into this layer and sinks to the depth where the less dense water can balance it. But the depth may be such that the water pressure exceeds the strength of the hull of the submarine, and it will be crushed in a matter of minutes.

According to the conclusion of American experts who investigated the causes of the death of the nuclear submarine Thresher in 1963 in the Atlantic Ocean, this submarine found itself in exactly this situation and was crushed by enormous hydrostatic pressure. Naturally, there were no witnesses to the tragedy, but the version of the cause of the disaster is confirmed by the results of observations carried out by research ships in the area where the submarine sank. And these observations showed that internal waves with a height of more than 100 meters often arise here.

A special type are the waves that arise on the sea when there is a change atmospheric pressure. They're called seiches And microseiches. Oceanology studies them.

So, we talked about both short and long waves at sea, both surface and internal. Now let us remember that long waves arise in the ocean not only from winds and cyclones, but also from processes occurring in the earth’s crust and even in the deeper regions of the “interior” of our planet. The length of such waves is many times greater than the longest ocean swell waves. These waves are called tsunami. The height of tsunami waves is not much higher than large storm waves, but their length reaches hundreds of kilometers. The Japanese word "tsunami" roughly translates to "harbour wave" or "coastal wave" . To some extent, this name conveys the essence of the phenomenon. The point is that in open ocean a tsunami poses no danger. At a sufficient distance from the coast, the tsunami does not rage, does not cause destruction, and cannot even be noticed or felt. All tsunami disasters occur on the shore, in ports and harbors.

Tsunamis occur most often from earthquakes caused by the movement of tectonic plates earth's crust, as well as from strong volcanic eruptions.

The mechanism for the formation of a tsunami is most often as follows: as a result of the displacement or rupture of a section of the earth's crust, a sudden rise or fall of a significant section of the seabed occurs. As a result, a rapid change in the volume of the water space occurs, and elastic waves appear in the water, propagating at a speed of about one and a half kilometers per second. These powerful elastic waves generate tsunamis on the ocean surface.

Having arisen on the surface, tsunami waves scatter in circles from the epicenter. At the point of origin, the height of the tsunami wave is small: from 1 centimeter to two meters (sometimes up to 4-5 meters), but more often in the range from 0.3 to 0.5 meters, and the wave length is huge: 100-200 kilometers. Invisible in the ocean, these waves, approaching the shore, like wind waves, become steeper and higher, sometimes reaching a height of 10-30 and even 40 meters. Having hit the shore, tsunamis destroy and destroy everything in their path and, worst of all, bring death to thousands, and sometimes tens and even hundreds of thousands of people.

The speed of tsunami propagation can be from 50 to 1000 kilometers per hour. Measurements show that the speed of a tsunami wave varies in proportion to the square root of the sea depth. On average, a tsunami rushes across the open ocean at a speed of 700-800 kilometers per hour.

Tsunamis are not regular events, but they are no longer rare.

In Japan, tsunami waves have been recorded for more than 1,300 years. Average per Country rising sun destructive tsunamis struck every 15 years (small tsunamis that did not have serious consequences are not taken into account).

Most tsunamis occur in the Pacific Ocean. Tsunamis raged in the Kuril, Aleutian, Hawaiian, and Philippine islands. They attacked the coasts of India, Indonesia, North and South America, as well as European countries located on Atlantic coast and in the Mediterranean.

The last most destructive tsunami attack was the terrible flood of 2004 with enormous destruction and loss of life, which had seismic causes and originated in the center of the Indian Ocean.

In order to have an idea of the specific manifestations of a tsunami, you can refer to numerous materials that describe this phenomenon.

We will give just a few examples. This is how the results of the earthquake that occurred in the Atlantic Ocean not far from the Iberian Peninsula on November 1, 1755 were described in the press. It caused terrible destruction in the capital of Portugal, Lisbon. The ruins of the once majestic building still tower in the city center convent Karmo that was never restored. These ruins remind the people of Lisbon of the tragedy that struck the city on November 1, 1755. Shortly after the earthquake, the sea receded, and then a wave 26 meters high hit the city. Many residents, fleeing the falling debris of buildings, left the narrow streets of the city and gathered on the wide embankment. The surging wave washed away 60 thousand people into the sea. Lisbon was not completely flooded because it is located on several high hills, but in low-lying areas the sea flooded the land up to 15 kilometers from the coast.

On August 27, 1883, there was a powerful eruption of the Kratau volcano, located in the Sunda Strait of the Indonesian archipelago. Clouds of ash rose into the sky, a strong earthquake arose, generating a wave 30-40 meters high. In a few minutes, this wave washed away all the villages located on the low shores of western Java and southern Sumatra into the sea, killing 35 thousand people. At a speed of 560 kilometers per hour, tsunami waves swept through the Indian and Pacific Ocean s, reaching the shores of Africa, Australia and America. Even in the Atlantic Ocean, despite its isolation and remoteness, in some places (France, Panama) a certain rise in water was noted.

On June 15, 1896, the incoming tsunami waves destroyed the east coast Japanese island Honshu 10 thousand houses. As a result, 27 thousand inhabitants died.

It is impossible to fight a tsunami. But it is possible and necessary to minimize the damage they cause to people. Therefore, now in all seismically active areas where there is a threat of tsunami waves, special warning services have been created, equipped with the necessary equipment that receives from located in different places coast sensitive seismographs signals about changes in seismic conditions. The population of such areas is regularly instructed on the rules of behavior in the event of a threat of tsunami waves. Tsunami warning services in Japan and the Hawaiian Islands have repeatedly given timely warning signals about the approach of a tsunami, thereby saving more than one thousand human lives.

All types of currents and waves are characterized by the fact that they carry colossal energy - thermal and mechanical. But humanity is not able to use this energy, unless, of course, we count attempts to use the energy of ebbs and flows. One of the scientists, probably a lover of statistics, calculated that the power of sea tides exceeds 1000000000 kilowatts, and that of all the rivers of the globe - 850000000 kilowatts. The energy of one square kilometer of a stormy sea is estimated at billions of kilowatts. What does this mean for us? Only that a person cannot use even a millionth part of the energy of tides and storms. To some extent, people use wind energy to generate electricity and other purposes. But that, as they say, is another story.

Tsunami(as they were called in Japan) occur during underwater earthquakes and volcanic eruptions, when large masses of water begin to move, forming very long waves, almost imperceptible in the open ocean. With enormous speed - up to 800 km/h (the speed of a jet airliner) - they scatter in all directions from their point of origin. Off the coast, the speed and length of waves decrease sharply, however height increases many times. But even this reduced speed is enough to cause a lot of trouble. Tsunamis are a terrible natural phenomenon; they claim thousands of lives and cause enormous damage to coastal areas. Shipping also suffered heavily from the tsunami.

Tsunami. Chronicle of the most destructive cases.

So, in 1737, 20 thousand died in the Bay of Bengal. sailing ships and boats and about 300 thousand people. There was no war here. There was a wave 30 meters high. It was she who sank an entire armada of ships and took so many human lives.

In November 1755, the Portuguese capital of Lisbon was almost completely destroyed by a tsunami: First Atlantic Ocean retreated from the shores. 300 large warships and merchant ships found themselves on the exposed bottom of Lisbon harbor, in many cases overturned. Suddenly a rumble came from the direction of the ocean. It grew quickly. A moment later, a giant wave burst into the bay, destroying everything in its path. Vessels and ships caught by the tsunami, like matchboxes, were thrown far ashore.

The largest tsunamis occur during earthquakes in the Pacific Ocean. Thirty-eight times giant waves devastated Hawaii, fourteen times they raided the Kuril Islands and Kamchatka. In the summer of 1780, during an earthquake in the area of the northern part of the Kuril Islands and southern Kamchatka, the ship St. Natalia was torn from its anchors and thrown onto the island of Iturup at a distance of 350 m from the shore.

In 1889, during the eruption of the Krakatoa volcano in the Sunda Strait of the Indonesian archipelago, a giant tsunami 35 m high hit the shore and killed tens of thousands of people. And how many ships were broken! The waves lifted the Danish gunboat to a height of ten meters and threw it four kilometers from the shore.

A few years after this terrible event in the Gulf of Mexico, a tsunami was thrown onto Chandler Island big ship Ebenger. He stood on land for 12 years. A new tsunami took the ship off the island and returned it to the sea.

Perhaps the most notable event was the May 1960 tsunami during the Chilean earthquake. The disaster caused enormous loss of life, and the property damage caused is estimated at a billion dollars. Characteristic Chilean tsunamis - their wide advance in the Pacific Ocean while maintaining great destructive power. The distance to Petropavlovsk - over 16,000 km - they covered in 20 hours 30 minutes at an average speed of 750-800 km/h.

According to the height of the waves, reaching 25 m, and the length coastal strip devastated, the Chilean tsunami is particularly memorable. Newspapers in those days were full of headlines: “Thousands of dead,” “ Dead cities and villages”, “Many destroyed ships”.

The first manifestation of the tsunami was sea retreat. This is how this phenomenon is described in Chilean newspapers:

“The next moment, they suddenly noticed that the water began to move away from the shores, leaving the ocean bottom open more than at the highest low tide... After a short period of time - from 15 to 30 minutes - the sea returned, approaching the shore like a giant wave...”

According to the newspaper Libération, the tsunami waves that flooded the city of Corral carried away two large-tonnage vessels: Sant-Iago and Karl Gaserbek. The ships were carried along the city streets. The first of them reached the harbor of Valparaiso. Only by chance can one explain the fact that the ship did not crash during this “voyage.” As for Karl Gaverbeck, its fate was sad: it soon sank.

The tsunami that broke into the Australian port of Sydney created a whirlpool, causing great damage to ships docked in the harbor. Small ships were especially affected. Whirlpools in bays, accidents and shipwrecks were also caused by the Chilean tsunami in the ports of Mexico and on the Californian coast of the United States. Dozens of sea vessels found their grave here.

Off the coast of New Zealand, a wave capsized several large-capacity ships, including a large passenger ferry stationed in Auckland Harbour.

Japan- one of the countries most affected by the tsunami. The echoes of the Chilean earthquake also affected her. The Chilean tsunami devastated large parts of Hokkaido south of Kushiro and the northern coast of Honshu. The island of Okinawa was particularly affected - it was the worst disaster of its kind in its entire history. In the area of Shogama in northern Japan, the entire coastline was dotted with the remains of ships, barges, boats and fishing sailboats.

Tsunamis also occurred in subsequent years: in October 1963 they captured the Kuril Islands area. Then a three-meter wave approached the shore. Residents were warned and took refuge in high places, the ships weighed anchor and went to the open sea, where the tsunami no longer poses a serious danger to ships.

In June 1964, a strong earthquake and the resulting waves caused enormous damage to the Japanese city of Ningata. The ships in the harbor were thrown ashore.

In October 1966, powerful ocean waves that arose in southern hemisphere as a result of an earthquake off the Peruvian coast, they again crossed the entire Pacific Ocean, crossed into the northern hemisphere and on the night of October 13 reached the Kuril Islands. And again houses collapsed and ships perished.

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