Wave(Wave, surge, sea) - formed due to the adhesion of particles of liquid and air; sliding along the smooth surface of the water, at first the air creates ripples, and only then, acting on its inclined surfaces, gradually develops agitation of the water mass. Experience has shown that water particles do not have forward motion; moves only vertically. Sea waves are the movement of water on the sea surface that occurs at certain intervals.

The highest point of the wave is called comb or the top of the wave, and the lowest point is sole. Height of a wave is the distance from the crest to its base, and length this is the distance between two ridges or soles. The time between two crests or troughs is called period waves.

Main causes

On average, the height of a wave during a storm in the ocean reaches 7-8 meters, usually it can stretch in length - up to 150 meters and up to 250 meters during a storm.

In most cases, sea waves are formed by the wind. The strength and size of such waves depend on the strength of the wind, as well as its duration and “acceleration” - the length of the path along which the wind acts on the water surface. Sometimes the waves that hit the coast can originate thousands of kilometers from the coast. But there are many other factors in the occurrence of sea waves: these are the tidal forces of the Moon and the Sun, fluctuations in atmospheric pressure, eruptions of underwater volcanoes, underwater earthquakes, and the movement of sea vessels.

Waves observed in other water bodies can be of two types:

1) Wind created by the wind, taking on a steady character after the wind ceases to act and called established waves, or swell; Wind waves are created due to the action of wind (movement of air masses) on the surface of the water, that is, injection. The reason for the oscillatory movements of the waves becomes easy to understand if you notice the effect of the same wind on the surface of a wheat field. The inconstancy of wind flows, which create waves, is clearly visible.

2) Waves of movement, or standing waves, are formed as a result of strong tremors at the bottom during earthquakes or excited, for example, by a sharp change in atmospheric pressure. These waves are also called single waves.

Unlike tides and currents, waves do not move masses of water. The waves move, but the water remains in place. A boat that rocks on the waves does not float away with the wave. She will be able to move slightly along an inclined slope only thanks to the force of earth's gravity. Water particles in a wave move along rings. The further these rings are from the surface, the smaller they become and, finally, disappear completely. Being in a submarine at a depth of 70-80 meters, you will not feel the effect of sea waves even during the most severe storm on the surface.

Types of sea waves

Waves can travel vast distances without changing shape and losing virtually no energy, long after the wind that caused them has died down. Breaking on the shore, sea waves release enormous energy accumulated during the journey. The force of continuously breaking waves changes the shape of the shore in different ways. The spreading and rolling waves wash the shore and are therefore called constructive. Waves crashing onto the shore gradually destroy it and wash away the beaches that protect it. That's why they are called destructive.

Low, wide, rounded waves away from the shore are called swells. Waves cause water particles to describe circles and rings. The size of the rings decreases with depth. As the wave approaches the sloping shore, the water particles in it describe increasingly flattened ovals. Approaching the shore, the sea waves can no longer close their ovals, and the wave breaks. In shallow water, the water particles can no longer close their ovals, and the wave breaks. Headlands are formed from harder rock and erode more slowly than adjacent sections of the coast. Steep, high sea waves undermine the rocky cliffs at the base, creating niches. Cliffs sometimes collapse. The terrace, smoothed by the waves, is all that remains of the rocks destroyed by the sea. Sometimes water rises along vertical cracks in the rock to the top and breaks out to the surface, forming a funnel. The destructive force of the waves widens the cracks in the rock, forming caves. When the waves wear away at the rock on both sides until they meet at a break, arches are formed. When the top of the arch falls into the sea, stone pillars remain. Their foundations are undermined and the pillars collapse, forming boulders. The pebbles and sand on the beach are the result of erosion.

Destructive waves gradually erode the coast and carry away sand and pebbles from sea beaches. Bringing the full weight of their water and washed-away material onto slopes and cliffs, the waves destroy their surface. They squeeze water and air into every crack, every crevice, often with explosive energy, gradually separating and weakening the rocks. The broken rock fragments are used for further destruction. Even the hardest rocks are gradually destroyed, and the land on the shore changes under the influence of waves. Waves can destroy the seashore with amazing speed. In Lincolnshire, England, erosion (destruction) is advancing at a rate of 2 m per year. Since 1870, when the largest lighthouse in the United States was built at Cape Hatteras, the sea has washed away beaches 426 m inland.

Tsunami

Tsunami These are waves of enormous destructive power. They are caused by underwater earthquakes or volcanic eruptions and can cross oceans faster than a jet plane: 1000 km/h. In deep waters, they can be less than one meter, but, approaching the shore, they slow down and grow to 30-50 meters before collapsing, flooding the shore and sweeping away everything in their path. 90% of all recorded tsunamis occurred in the Pacific Ocean.

The most common reasons.

About 80% of tsunami generation cases are underwater earthquakes. During an earthquake under water, a mutual vertical displacement of the bottom occurs: part of the bottom sinks, and part rises. Oscillatory movements occur vertically on the surface of the water, tending to return to the original level - the average sea level - and generate a series of waves. Not every underwater earthquake is accompanied by a tsunami. Tsunamigenic (that is, generating a tsunami wave) is usually an earthquake with a shallow source. The problem of recognizing the tsunamigenicity of an earthquake has not yet been solved, and warning services are guided by the magnitude of the earthquake. The most powerful tsunamis are generated in subduction zones. Also, it is necessary for the underwater shock to resonate with the wave oscillations.

Landslides. Tsunamis of this type occur more frequently than estimated in the 20th century (about 7% of all tsunamis). Often an earthquake causes a landslide and it also generates a wave. On July 9, 1958, an earthquake in Alaska caused a landslide in Lituya Bay. A mass of ice and earth rocks collapsed from a height of 1100 m. A wave was formed that reached a height of more than 524 m on the opposite shore of the bay. Cases of this kind are quite rare and are not considered as a standard. But underwater landslides occur much more often in river deltas, which are no less dangerous. An earthquake can cause a landslide and, for example, in Indonesia, where shelf sedimentation is very large, landslide tsunamis are especially dangerous, as they occur regularly, causing local waves more than 20 meters high.

Volcanic eruptions account for approximately 5% of all tsunami events. Large underwater eruptions have the same effect as earthquakes. In large volcanic explosions, not only are waves generated from the explosion, but water also fills the cavities of the erupted material or even the caldera, resulting in a long wave. A classic example is the tsunami generated after the Krakatoa eruption in 1883. Huge tsunamis from the Krakatoa volcano were observed in harbors around the world and destroyed a total of more than 5,000 ships and killed about 36,000 people.

Signs of a tsunami.

• Sudden fast the withdrawal of water from the shore over a considerable distance and the drying of the bottom. The further the sea recedes, the higher the tsunami waves can be. People who are on the shore and do not know about dangers, may stay out of curiosity or to collect fish and shells. In this case, it is necessary to leave the shore as soon as possible and move as far away from it as possible - this rule should be followed when, for example, in Japan, on the Indian Ocean coast of Indonesia, or Kamchatka. In the case of a teletsunami, the wave usually approaches without the water receding.
• Earthquake. The epicenter of an earthquake is usually in the ocean. On the coast, the earthquake is usually much weaker, and often there is no earthquake at all. 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, thus preparing in advance for the arrival of the wave.
• Unusual drift ice and other floating objects, formation of cracks in fast ice.
• Huge reverse faults at the edges of stationary ice and reefs, the formation of crowds and currents.

rogue waves

rogue waves(Roaming waves, monster waves, freak waves - anomalous waves) - giant waves that arise in the ocean, more than 30 meters high, have behavior unusual for sea waves.

Just 10-15 years ago, scientists considered sailors’ stories about gigantic killer waves that appear out of nowhere and sink ships as just maritime folklore. For a long time wandering waves were considered fiction, since they did not fit into any mathematical model that existed at that time for calculating the occurrence and their behavior, because waves with a height of more than 21 meters cannot exist in the oceans of planet Earth.

One of the first descriptions of a monster wave dates back to 1826. Its height was more than 25 meters and it was noticed in the Atlantic Ocean near the Bay of Biscay. Nobody believed this message. And in 1840, the navigator Dumont d'Urville risked appearing at a meeting of the French Geographical Society and declaring that he had seen a 35-meter wave with his own eyes. Those present laughed at him. But there are stories about huge ghost waves that suddenly appeared in the middle of the ocean even with little storm, and their steepness resembled sheer walls of water, it became more and more.

Historical evidence of rogue waves

So, in 1933, the US Navy ship Ramapo was caught in a storm in the Pacific Ocean. For seven days the ship was tossed about by the waves. And on the morning of February 7, a shaft of incredible height suddenly crept up from behind. First, the ship was thrown into a deep abyss, and then lifted almost vertically onto a mountain of foaming water. The crew, who were lucky enough to survive, recorded a wave height of 34 meters. It moved at a speed of 23 m/sec, or 85 km/h. So far, this is considered the highest rogue wave ever measured.

During World War II, in 1942, the Queen Mary liner carried 16 thousand American military personnel from New York to the UK (by the way, a record for the number of people transported on one ship). Suddenly a 28-meter wave appeared. “The upper deck was at its usual height, and suddenly - suddenly! - it suddenly went down,” recalled Dr. Norval Carter, who was on board the ill-fated ship. The ship tilted at an angle of 53 degrees - if the angle had been even three degrees more, death would have been inevitable. The story of "Queen Mary" formed the basis of the Hollywood film "Poseidon".

However, on January 1, 1995, on the Dropner oil platform in the North Sea off the coast of Norway, a wave with a height of 25.6 meters, called the Dropner wave, was first recorded by instruments. The Maximum Wave project allowed us to take a fresh look at the causes of the death of dry cargo ships that transported containers and other important cargo. Further research recorded over three weeks around the globe more than 10 single giant waves, the height of which exceeded 20 meters. The new project is called Wave Atlas, which provides for the compilation of a worldwide map of observed monster waves and its subsequent processing and addition.

Causes

There are several hypotheses about the causes of extreme waves. Many of them lack common sense. The simplest explanations are based on the analysis of a simple superposition of waves of different lengths. Estimates, however, show that the probability of extreme waves in such a scheme is too small. Another noteworthy hypothesis suggests the possibility of focusing wave energy in some surface current structures. These structures, however, are too specific for an energy focusing mechanism to explain the systematic occurrence of extreme waves. The most reliable explanation for the occurrence of extreme waves should be based on the internal mechanisms of nonlinear surface waves without involving external factors.

Interestingly, such waves can be both crests and troughs, which is confirmed by eyewitnesses. Further research involves the effects of nonlinearity in wind waves, which can lead to the formation of small groups of waves (packets) or individual waves (solitons) that can travel long distances without significantly changing their structure. Similar packages have also been observed many times in practice. The characteristic features of such groups of waves, confirming this theory, are that they move independently of other waves and have a small width (less than 1 km), with heights decreasing sharply at the edges.

However, it has not yet been possible to completely clarify the nature of the anomalous waves.

The waves that we are used to seeing on the surface of the sea are formed mainly under the influence of wind. However, waves can also arise for other reasons, then they are called;

Tidal, formed under the influence of the tidal forces of the Moon and the Sun;

Baric pressure, which occurs during sudden changes in atmospheric pressure;

Seismic (tsunami) formed as a result of an earthquake or volcanic eruption;

Ship problems that arise when the ship is moving.

Wind waves are predominant on the surface of seas and oceans. Tidal, seismic, pressure and ship waves do not have a significant effect on the navigation of ships in the open ocean, so we will not dwell on their description. Wind waves are one of the main hydrometeorological factors that determine the safety and economic efficiency of navigation, since the wave, running onto the ship, hits it, rocks it, hits the side, floods the decks and superstructures, and reduces the speed. The motion creates dangerous lists, makes it difficult to determine the position of the vessel and greatly exhausts the crew. In addition to the loss of speed, waves cause the vessel to yaw and deviate from the given course, and to maintain it, constant shifting of the rudder is required.

Wind waves are the process of formation, development and propagation of wind-induced waves on the sea surface. Wind waves have two main features. The first feature is irregularity: disorder in the sizes and shapes of waves. One wave does not repeat another; a large one may be followed by a small one, or perhaps an even larger one; Each individual wave continuously changes its shape. Wave crests move not only in the direction of the wind, but also in other directions. Such a complex structure of the disturbed sea surface is explained by the vortex, turbulent nature of the wind that forms waves. The second feature of waves is the rapid variability of its elements in time and space and is also associated with the wind. However, the size of the waves depends not only on the wind speed; the duration of its action, the area and configuration of the water surface are of significant importance. From a practical point of view, there is no need to know the elements of each individual wave or each wave vibration. Therefore, the study of waves ultimately comes down to identifying statistical patterns that are numerically expressed by the dependencies between wave elements and the factors that determine them.

3.1.1. Wave elements

The common elements for waves are (Fig. 25):

Apex - the highest point of the wave crest;

The bottom is the lowest point of the wave trough;

Height (h) - exceeding the top of the wave;

Length (L) is the horizontal distance between the tops of two adjacent ridges on a wave profile drawn in the general direction of wave propagation;

Period (t) - the time interval between the passage of two adjacent wave peaks through a fixed vertical; in other words, it is the period of time during which the wave travels a distance equal to its length;

Slope (e) is the ratio of the height of a given wave to its length. The steepness of the wave at different points of the wave profile is different. The average wave steepness is determined by the ratio:

Rice. 25. Basic elements of waves.

Wave front is a line on the plan of a rough surface, passing along the vertices of the crest of a given wave, which are determined by a set of wave profiles drawn parallel to the general direction of wave propagation.

For navigation, wave elements such as height, period, length, steepness and general direction of wave movement are of greatest importance. All of them depend on the parameters of the wind flow (wind speed and direction), its length (acceleration) over the sea and the duration of its action.

Depending on the conditions of formation and propagation, wind waves can be divided into four types.

Wind - a system of waves that, at the moment of observation, is under the influence of the wind by which it is caused. The directions of propagation of wind waves and wind in deep water usually coincide or differ by no more than four points (45°).

Wind waves are characterized by the fact that their leeward slope is steeper than the windward one, so the tops of the crests usually collapse, forming foam, or are even torn off by strong winds. When waves enter shallow water and approach the shore, the directions of wave and wind propagation can differ by more than 45°.

Swell - wind-induced waves that propagate in the wave-forming area after the wind weakens and/or changes its direction, or wind-induced waves that come from the wave-forming area to another area where the wind is blowing at a different speed and/or a different direction. A special case of swell that propagates in the absence of wind is called a dead swell.

Mixed - waves formed as a result of the interaction of wind waves and swell.

Transformation of wind waves - changes in the structure of wind waves with changes in depth. In this case, the shape of the waves is distorted, they become steeper and shorter, and at a shallow depth, not exceeding the height of the wave, the crests of the latter overturn and the waves are destroyed.

In their appearance, wind waves are characterized by different shapes.

Ripple is the initial form of wind wave development that occurs under the influence of a weak wind; The crests of the waves resemble scales when they ripple.

Three-dimensional waves are a set of waves whose average crest length is several times greater than the average wavelength.

Regular waves are waves in which the shape and elements of all waves are the same.

Crowd is a chaotic disturbance that arises as a result of the interaction of waves traveling in different directions.

Waves breaking over banks, reefs or rocks are called breakers. Waves crashing in the coastal area are called surf. Near steep shores and near port facilities, the surf has the form of a reverse surge.

Waves on the surface of the sea are divided into free, when the force that caused them ceases to act and the waves move freely, and forced, when the force that caused the formation of the waves does not stop.

Based on the variability of wave elements over time, they are divided into steady waves, i.e., wind waves, in which the statistical characteristics of waves do not change over time, and developing or attenuating waves, which change their elements over time.

According to their shape, waves are divided into two-dimensional - a set of waves whose average crest length is many times greater than the average wavelength, three-dimensional - a set of waves whose average crest length is several times greater than the wave length, and solitary, having only a dome-shaped crest without a sole.

Depending on the ratio of the wavelength to the depth of the sea, waves are divided into short, the length of which is significantly less than the depth of the sea, and long, the length of which is greater than the depth of the sea.

According to the nature of the movement of the waveform, they can be translational, in which there is visible movement of the waveform, and standing - having no movement. Based on how the waves are located, they are divided into surface and internal. Internal waves are formed at one or another depth at the interface between layers of water of different densities.

3.1.2. Methods for calculating wave elements

The rotational motion of successively located water particles, shifted by a phase angle at the initial moment of movement, creates the appearance of translational motion: individual particles move in closed orbits, while the wave profile moves translationally in the direction of the wind. The trochoidal wave theory made it possible to mathematically substantiate the structure of individual waves and relate their elements to each other. Formulas were obtained that made it possible to calculate individual wave elements

It should be noted that the trochoidal wave theory is valid only for regular two-dimensional waves, which are observed in the case of free wind waves - swell. In three-dimensional wind waves, the orbital paths of particles are not closed circular orbits, since under the influence of wind, horizontal transfer of water occurs on the sea surface in the direction of wave propagation.

The trochoidal theory of sea waves does not reveal the process of their development and attenuation, as well as the mechanism of energy transfer from wind to wave. Meanwhile, solving precisely these issues is necessary in order to obtain reliable dependencies for calculating the elements of wind waves.

Therefore, the development of the theory of sea waves took the path of developing theoretical and empirical connections between wind and waves, taking into account the diversity of real sea wind waves and the non-stationary nature of the phenomenon, i.e., taking into account their development and attenuation.

In general, formulas for calculating wind wave elements can be expressed as a function of several variables

H, t, L,C=f(W , D t, H),

Where W is wind speed; D - acceleration, t - duration of wind action; H - depth of the sea.

For shallow sea areas, the dependences can be used to calculate wave height and length

A = 0.0151H 0.342; z = 0.104H 0.573 .

For open sea areas, the elements of waves, the probability of heights of which is 5%, and the average wavelengths are calculated according to the dependencies:

H = 0.45 W 0.56 D 0.54 A,

L = 0.3lW 0.66 D 0.64 A.

Coefficient A is calculated using the formula

At the State Oceanographic Institute, based on the spectral statistical theory of waves, graphical connections were obtained between wave elements and wind speed, duration of its action and acceleration length. These dependencies should be considered the most reliable, giving acceptable results, on the basis of which nomograms for calculating wave heights were constructed at the Hydrometeorological Center of the USSR (V.S. Krasyuk). The nomogram (Fig. 26) is divided into four quadrants (I-IV) and consists of a series of graphs arranged in a certain sequence.

In quadrant I (counting from the lower right corner) of the nomogram, a degree grid is given, each division of which (horizontally) corresponds to 1° of the meridian at a given latitude (from 70 to 20° N) for maps at a scale of 1:15 000000 polar stereographic projections. The degree grid is necessary to convert the distance between the isobars n and the radius of curvature of the isobars R, measured on maps of a different scale, to a scale of 1:15 000000. In this case, we determine the distance between the isobars n and the radius of curvature of the isobars R in meridian degrees at a given latitude. The radius of curvature of isobars R is the radius of the circle with which the section of the isobar passing through the point for which the calculation is being carried out, or near it, has the greatest contact. It is determined using a meter by selecting it in such a way that an arc drawn from the found center coincides with a given section of the isobar. Then, on a degree grid, we plot the measured values ​​at a given latitude, expressed in degrees of the meridian, and using a compass we determine the radius of curvature of the isobars and the distance between the isobars, corresponding to a scale of 1:15,000,000.

Rice. 26. Nomogram for calculating wave elements and wind speed from surface pressure field maps, where isobars are drawn at intervals of 5 mbar (a) and 8 mbar (b). 1 - winter, 2 - summer.

In quadrant IV there are curves that make it possible to determine the height of the so-called significant waves (h 3H), which have a probability of 12.5%, based on wind speed, acceleration or duration of wind action.

If it is possible, when determining wave height, to use not only data on wind speed, but also on the acceleration and duration of the wind, the calculation is performed using the acceleration and duration of the wind (in hours). To do this, from quadrant III of the nomogram we lower the perpendicular not to the acceleration curve, but to the wind duration curve (6 or 12 hours). From the results obtained (in terms of acceleration and duration), the smaller value of the wave height is taken.

Calculation using the proposed nomogram can be made only for areas of the “deep sea”, i.e. for areas where the sea depth is not less than half the wavelength. When acceleration exceeds 500 km or wind duration exceeds 12 hours, the dependence of wave heights on wind corresponding to ocean conditions is used (thickened curve in quadrant IV).

Thus, to determine the height of the waves at a given point, it is necessary to perform the following operations:

A) find the radius of curvature of the isobar R passing through a given point or near it (using a compass by selection). The radius of curvature of isobars is determined only in the case of cyclonic curvature (in cyclones and troughs) and is expressed in meridian degrees;

B) determine the pressure difference n by measuring the distance between adjacent isobars in the area of ​​the selected point;

C) using the found values ​​of R and n, depending on the time of year, we find the wind speed W;

D) knowing the wind speed W and acceleration D or the duration of the wind (6 or 12 hours), we find the height of significant waves (h 3H).

Acceleration is found as follows. From each point for which the wave height is calculated, a streamline is drawn in the direction against the wind until its direction changes relative to the initial one by an angle of 45° or reaches the shore or the ice edge. Approximately this will be the acceleration or path of the wind, along which waves should be formed, arriving at a given point.

The duration of wind action is defined as the time during which the wind direction remains unchanged or deviates from the original by no more than ±22.5°.

According to the nomogram in Fig. 26a, you can determine the wave height from a map of the surface pressure field, on which isobars are drawn through 5 mbar. If the isobars are drawn through 8 mbar, then the nomogram shown in Fig. 26 b.

The wave period and length can be calculated from wind speed and wave height data. An approximate calculation of the wave period can be made using the graph (Fig. 27), which shows the relationship between the periods and the height of wind waves at different wind speeds (W). The wave length is determined by its period and sea depth at a given point according to the graph (Fig. 28).

People take many natural phenomena for granted. We are accustomed to summer, autumn, winter, rain, snow, waves and do not think about the reasons. And yet, why do waves form in the sea? Why do ripples appear on the surface of the water even in complete calm?

Origin

There are several theories explaining the occurrence of sea and ocean waves. They are formed due to:

• changes in atmospheric pressure;
• ebbs and flows;
• underwater earthquakes and volcanic eruptions;
• ship movements;
• strong wind.

To understand the mechanism of formation, you need to remember that water is agitated and vibrates forcibly - as a result of physical impact. A pebble, a boat, or a hand touching it set the liquid mass in motion, creating vibrations of varying strengths.

Characteristics

Waves are also the movement of water on the surface of a reservoir. They are the result of the adhesion of air particles and liquid. At first, the water-air symbiosis causes ripples on the surface of the water, and then causes the water column to move.

Size, length and strength vary depending on the strength of the wind. During a storm, powerful pillars rise 8 meters and stretch almost a quarter of a kilometer in length.

Sometimes the force is so destructive that it hits the coastal strip, uproots umbrellas, showers and other beach buildings, and demolishes everything in its path. And this despite the fact that oscillations are formed several thousand kilometers from the coast.

All waves can be divided into 2 categories:

• wind;
• standing.

Wind

Wind ones, as the name suggests, are formed under the influence of wind. Its gusts sweep tangentially, pumping the water and forcing it to move. The wind pushes the liquid mass forward in front of it, but gravity slows down the process, pushing it back. Movements on the surface resulting from the influence of two forces resemble ascents and descents. Their peaks are called ridges, and their bases are called soles.

Having found out why waves form on the sea, the question remains open: why do they make oscillatory movements up and down? The explanation is simple - the variability of the wind. It flies in quickly and impetuously, then subsides. The height of the ridge and the frequency of oscillations directly depend on its strength and power. If the speed of movement and the strength of air currents exceed the norm, a storm arises. Another reason is renewable energy.

Renewable Energy

Sometimes the sea is completely calm, but waves form. Why? Oceanographers and geographers attribute this phenomenon to renewable energy. Water vibrations are its source and ways to maintain the potential for a long time.

In life it looks something like this. The wind creates a certain amount of vibrations in a body of water. The energy of these vibrations will last for several hours. During this time, liquid formations cover distances of tens of kilometers and “moor” in areas where it is sunny, there is no wind, and the body of water is calm.

standing

Standing or single waves arise due to tremors on the ocean floor, characteristic of earthquakes, volcanic eruptions, and also due to a sharp change in atmospheric pressure.

This phenomenon is called a seiche, which translates from French as “to swing.” Seiches are typical for bays, bays and some seas; they pose a danger to beaches, structures in the coastal strip, ships moored at the pier and people on board.

Constructive and destructive

Formations that travel long distances without changing shape or losing energy hit the shore and break. Moreover, each surge has a different effect on the coastal strip. If it washes the shore, it is classified as constructive.

The destructive surge of water hits the coast with its might, destroying it, gradually washing away sand and pebbles from the beach strip. In this case, the natural phenomenon is classified as destructive.

Destruction comes in different destructive powers. Sometimes it is so powerful that it collapses slopes, splits cliffs, and separates rocks. Over time, even the hardest rocks erode. America's largest lighthouse was built at Cape Hatteras in 1870. Since then, the sea has moved almost 430 meters into the coast, washing away the coastal strip and beaches. This is just one of dozens of facts.

Tsunami is a type of destructive water formations characterized by great destructive power. Their speed reaches up to 1000 km/h. This is higher than that of a jet plane. At depth, the height of the tsunami crest is small, but near the shore they slow down, but increase in height to 20 meters.

In 80% of cases, tsunamis are the result of underwater earthquakes, in the remaining 20% ​​- volcanic eruptions and landslides. As a result of earthquakes, the bottom shifts vertically: one part of it goes down, and the other part rises in parallel. Vibrations of varying strengths are formed on the surface of the reservoir.

Abnormal killers

They are also known as wanderers, monsters, anomalous and more common in the oceans.

Even 30-40 years ago, sailors’ stories about anomalous fluctuations in water were considered fables, because eyewitness accounts did not fit into existing scientific theories and calculations. A height of 21 meters was considered the limit for oceanic and sea fluctuations.

The main reason for the formation of waves is the wind blowing over the water. Therefore, the magnitude of the wave depends on the strength and time of its impact. Due to the wind, water particles rise upward, sometimes breaking away from the surface, but after some time, under the influence of natural gravity, they inevitably fall down. From a distance it may seem that the wave is moving forward, but in fact, if this wave, of course, is not a tsunami, (a tsunami has a different nature of occurrence) it only falls and rises. So, for example, a seabird that has landed on the surface of a rough sea will sway on the waves, but will not move from its place.

Only near the shore, where it is no longer deep, does the water move forward, rolling onto the shore. By the way, experienced sailors determine the degree of sea roughness by looking at the ridge of spray from broken drops forming a crest on a wave; if a ridge and foam on it have just begun to form, then the sea state is 3 points.

What kind of sea wave is called a surge?

Waves on the sea can exist even without wind; these are tsunamis caused by natural disasters like underwater volcanic eruptions, and a wave that sailors call a run-up. It is formed at sea after a strong storm, when the wind has died down, but due to the large mass of water set in motion by the wind and a phenomenon called resonance, the waves continue to sway. It should be noted that such waves are not much safer than a storm and can easily capsize a ship or boat with inexperienced sailors.

Waves are created by the wind. Storms create winds that impact the surface of the water, resulting in ripples, just like the ripples in your cup of coffee after surfing when you blow on it. The wind itself can be seen on weather forecast maps: these are low pressure zones. The greater their concentration, the stronger the wind will be. Small (capillary) waves initially move in the direction in which the wind is blowing. The stronger and longer the wind blows, the greater its impact on the surface of the water. Over time, the waves begin to increase in size. As the wind continues to blow and the waves it generates continue to be affected by it, the small waves begin to grow. The wind has a greater effect on them than on a calm water surface. The size of the wave depends on the speed of the wind that forms it. A wind blowing at a certain constant speed will be able to generate a wave of a certain size. And as soon as the wave reaches its maximum possible size for a given wind, it becomes “fully formed.” The generated waves have different speeds and wave periods. (See the section on wave terminology for more details.) Long period waves travel faster and travel longer distances than their slower counterparts. As they move away from the source of the wind (propagation), the waves form lines of surf (swells), which inevitably roll onto the shore. You are probably already familiar with the concept of “wave set”! Waves that are no longer affected by the wind that generated them are called groundwells. This is exactly what surfers are after! What affects the size of the surf (swell)? There are three main factors that influence the size of waves on the open sea: Wind speed - the higher it is, the larger the wave will be. The duration of the wind is similar to the previous one. Fetch (fetch, “coverage area”) - again, the larger the coverage area, the larger the wave is formed. As soon as the wind stops affecting them, the waves begin to lose their energy. They will move until the protrusions of the seabed or other obstacles in their path (a large island, for example) absorb all the energy. There are several factors that influence the size of the wave at a particular surf location. Among them: The direction of the surf (swell) - will it allow the swell to get to the place we need? Ocean bottom - a swell moving from the depths of the ocean to a reef, forms large waves with barrels inside. A shallow, long ledge extending toward the shore will slow down the waves and they will lose their energy. Tides - some sports are completely dependent on it. Find out more in the section on how the best waves appear