The content of the article

Ebb and flow, periodic fluctuations in the water level (ups and downs) in the water areas on the Earth, which are due to the gravitational attraction of the Moon and the Sun, acting on the rotating Earth. All large water areas, including oceans, seas and lakes, are subject to tides to one degree or another, although they are small on lakes.

Reversible waterfall

(reversing direction) is another phenomenon associated with tides on rivers. A typical example is a waterfall on the St. John River (New Brunswick, Canada). Here, along a narrow gorge, water at high tide penetrates into a basin located above the low water level, but somewhat below the high water level in the same gorge. Thus, a barrier arises, flowing through which water forms a waterfall. At low tide, the flow of water rushes downstream through a narrowed passage and, overcoming an underwater ledge, forms an ordinary waterfall. At high tide, a steep wave that has penetrated the gorge falls like a waterfall into the overlying basin. The reverse current continues until the water levels on both sides of the threshold are equal and the tide begins to ebb. Then the waterfall is restored again, facing downstream. The average water level difference in the gorge is approx. 2.7 m, however, at the highest tides, the height of a direct waterfall can exceed 4.8 m, and a reverse one - 3.7 m.

The greatest amplitudes of the tides.

The world's highest tide is formed by strong currents in Minas Bay in the Bay of Fundy. Tidal fluctuations here are characterized by a normal course with a semidiurnal period. The water level at high tide often rises by more than 12 m in six hours, and then drops by the same amount over the next six hours. When the action of the spring tide, the position of the Moon at perigee, and the maximum declination of the Moon occur in one day, the tide level can reach 15 m. the top of the bay.

wind and weather.

Wind has a significant effect on tidal phenomena. The wind from the sea drives the water towards the shore, the height of the tide rises above normal, and at low tide the water level also exceeds the average. On the contrary, when the wind blows from the land, the water is driven away from the coast, and the sea level drops.

Due to the increase in atmospheric pressure over a vast area of ​​water, the water level decreases, as the superimposed weight of the atmosphere is added. When atmospheric pressure increases by 25 mm Hg. Art., the water level drops by about 33 cm. A decrease in atmospheric pressure causes a corresponding increase in the water level. Therefore, a sharp drop in atmospheric pressure, combined with hurricane-force winds, can cause a noticeable rise in the water level. Such waves, although they are called tidal waves, are in fact not associated with the influence of tidal forces and do not have the periodicity characteristic of tidal phenomena. The formation of these waves can be associated either with hurricane-force winds or with underwater earthquakes (in the latter case they are called seismic sea waves, or tsunamis).

The use of tidal energy.

Four methods have been developed to harness the energy of the tides, but the most practical of these is the creation of a system of tidal pools. At the same time, water level fluctuations associated with tidal phenomena are used in the lock system in such a way that the level difference is constantly maintained, which makes it possible to obtain energy. The power of tidal power plants directly depends on the area of ​​the trap pools and the potential level difference. The latter factor, in turn, is a function of the amplitude of the tidal fluctuations. The achievable level difference is by far the most important for power generation, although the cost of facilities depends on the size of the pools. At present, large tidal power plants operate in Russia on the Kola Peninsula and in Primorye, in France in the estuary of the Rance River, in China near Shanghai, and also in other regions of the globe.

Table: Information about tides in some ports of the world

TIDE INFORMATION FOR SOME PORTS IN THE WORLD
Port	Interval between tides		Average tide height, m	Spring tide height, m
	h	min
Cape Morris Jesep, Greenland, Denmark	10	49	0,12	0,18
Reykjavik, Iceland	4	50	2,77	3,66
R. Coxoak, Hudson Strait, Canada	8	56	7,65	10,19
St. John's, Newfoundland, Canada	7	12	0,76	1,04
Barntcoe, Bay of Fundy, Canada	0	09	12,02	13,51
Portland Maine, USA	11	10	2,71	3,11
Boston Massachusetts, USA	11	16	2,90	3,35
New York, pc. New York, USA	8	15	1,34	1,62
Baltimore, pc. Maryland, USA	6	29	0,33	0,40
Miami Beach Florida, USA	7	37	0,76	0,91
Galveston, pc. Texas, USA	5	07	0,30	0,43*
about. Maraca, Brazil	6	00	6,98	9,15
Rio de Janeiro, Brazil	2	23	0,76	1,07
Callao, Peru	5	36	0,55	0,73
Balboa, Panama	3	05	3,84	5,00
San Francisco, pc. California, USA	11	40	1,19	1,74*
Seattle, Washington, USA	4	29	2,32	3,45*
Nanaimo, British Columbia, Canada	5	00	...	3,42*
Sitka, Alaska, USA	0	07	2,35	3,02*
Sunrise, Cook Inlet, pc. Alaska, USA	6	15	9,24	10,16
Honolulu Hawaii, USA	3	41	0,37	0,58*
Papeete, oh Tahiti, French Polynesia	...	...	0,24	0,33
Darwin, Australia	5	00	4,39	6,19
Melbourne, Australia	2	10	0,52	0,58
Rangoon, Myanmar	4	26	3,90	4,97
Zanzibar, Tanzania	3	28	2,47	3,63
Cape Town, South Africa	2	55	0,98	1,31
Gibraltar, Vlad. Great Britain	1	27	0,70	0,94
Granville, France	5	45	8,69	12,26
Leith, UK	2	08	3,72	4,91
London, Great Britain	1	18	5,67	6,56
Dover, UK	11	06	4,42	5,67
Avonmouth, UK	6	39	9,48	12,32
Ramsey, oh Maine, UK	10	55	5,25	7,17
Oslo, Norway	5	26	0,30	0,33
Hamburg, Germany	4	40	2,23	2,38
* Daily tide amplitude.

Literature:

Shuleikin V.V. Physics of the sea. M., 1968
Harvey J. atmosphere and ocean. M., 1982
Drake C., Imbri J., Knaus J., Turekian K. The ocean itself and for us. M., 1982



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How to quickly and easily install a window sill

A truly revolutionary invention at the end of the 20th century was windows with sealed double-glazed windows. According to their performance characteristics, they are several times superior to conventional wooden structures with inset glass. But such windows need proper installation, and one of the stages of this installation is the installation of ebbs. In this article we will talk about what ebbs are, and I will also tell you how to fix this simple structure with your own hands.

What ebbs are currently produced

To begin with, let's understand what a low tide in plastic windows is. Simply put, the ebb is called the outer or outer window sill. It gives a finished look to the window opening and protects the part of the facade located under the window from atmospheric precipitation. But the most important purpose of the ebb is to remove moisture and protect the joint between the wall and the window frame.

It is difficult to call the dimensions of the window tide clearly fixed, in fact, now every serious manufacturer produces products according to its own internal specifications (TU). But it is believed that the width of factory ebbs ranges from 90 to 400 mm, and the length does not exceed 3 m. Everything that falls outside these limits must be made to order.

galvanized flashings

Standard galvanized metal sheet for the manufacture of ebbs has been used for more than a dozen years. In Soviet times, such external window sills were made in accordance with GOST 30971, now this standard also exists, but the section specifically related to external window sills is advisory in nature and is not mandatory.

Such window sills are made of cold-rolled steel with a thickness of at least 0.55 mm. Galvanized steel is strong and durable. One of the main advantages of these products is the affordable price.

Opponents and competitors point out that zinc coating is afraid of an acidic environment. And in modern cities, acid rain can allegedly destroy such low tides in a few years.

So, more than once I had to dismantle old galvanized ebbs and I can assure you that a zinc-coated metal window sill will last at least 15-20 years. And if you also paint it at least once every 5 years, then these ebbs will delight the owners for as long as you like.

Zinc coating is a fairly powerful and reliable protection. But all such products have one weak point, these are cuts and holes. There is no spraying, and it is from there that the steel begins to actively rust. So I always recommend to paint such ebbs with some kind of exterior paint.

Polyester outdoor window sills

Behind the tricky name are ordinary galvanized ebbs, only in this case they are additionally covered with polyester or plastisol. In construction supermarkets, consultants call such a coating powder or enamel.

The appearance and quality of such window sills is an order of magnitude higher than that of ordinary galvanized steel. Powder coating can be either matte or glossy. The price of such window sills is slightly higher, but people love them for their decent appearance and almost unlimited color range.

Again, envious people say that powder coating can be scratched and then the metal will begin to rust, this is really true. But I can assure you that birds, no matter how hard they try, are not able to cause any harm to the polyester coating, and if you do not plan to walk on the windowsill with a marching step, then you do not have to worry about scratches.

Castings from non-ferrous metals

The leader in this niche, of course, is aluminum. Such window sills, in fact, combine all the positive qualities of the previous options. As you know, aluminum is not afraid of corrosion, and even if it is not protected by anything, nothing will happen with such a low tide.

Although as far as I have seen, all aluminum window sills come with powder coating. Naturally, there is a huge selection. The only serious drawback of absolutely all window sills made of non-ferrous metals is the high price.

Copper window sills are much less common. Such ebbs are more typical for European countries. Our consumer considers copper sills to be unreasonably expensive, plus copper is not suitable for every design, and most importantly, copper window sills are not mass-produced, they must be ordered and installed individually.

Plastic ebbs

Plastic tint for windows is often made of polyvinyl chloride, that is, from the same material as the windows themselves. Naturally, when it comes to PVC windows, this combination can be considered close to ideal.

Brochures vying with each other promise consumers to make a PVC window tint in any color they like. Although as far as I have seen, all plastic comes in white, just if you order laminated windows, for example, under natural wood, then the window sill is also covered with a laminating film, that's all the wisdom.

But this is not the only advantage of plastic outdoor window sills. Such low tides are deservedly considered the quietest. Even with a very heavy downpour, you do not have to fall asleep under the drumming outside the window.

Under such window sills, separate fittings are produced. For example, side plastic moldings and plugs significantly improve the appearance of both the window itself and the outer window sill.

But the most important advantage, of course, is the price. Having a fairly respectable appearance, plastic window tint is cheaper than any of the competitors described above.

But to be honest, before installing external plastic ebbs, you need to think twice. The fact is that plastic can be easily scratched, and even birds can do it. Of course, the plastic window sill will not rust, but the view is not the same.

There is another potential danger: now plastic window sills, roughly speaking, are made by everyone and sundry. While the products are new, they all seem to look “smart”, but after a year the plastic begins to turn yellow, and in some cases even crack.

The reason is simple, your window sill is molded from low-quality plastic or PVC designed purely for interior decoration. There is only one way to save yourself from such a scourge. Order windows from a well-known, trusted manufacturer, and most importantly, take all related fittings, including external ebbs, in the same place.

Naturally, in addition to the above listed types of outdoor window sills, there are still granite, marble and other similar natural stone sills. But I don’t see the point in talking about them in detail within the framework of this article, since, firstly, they cost sky-high money. And secondly, the installation of such low tides requires serious professional training.

Subtleties of selection and installation of low tide

Do not be afraid, it is not difficult to choose and install a low tide with your own hands. From the tool it is desirable to have a screwdriver, it will be inconvenient to mount with a simple screwdriver. For a pattern of metal ebbs, you will need scissors for metal. Plastic is cut with a hacksaw.

A few words about choice

• We have already talked about the features of the material for outdoor window sills. But the first selection criterion for most people is always cost. So aluminum ebbs with colored powder coating will cost about 400 - 500 rubles per linear meter. Galvanized steel with the same color coating will cost 300 - 400 rubles / m.p. The price of an ordinary galvanized window sill is rarely understood to be higher than 300 rubles / m.p. A decent, factory-made PVC tint for windows usually costs around 200 - 300 rubles / m.p.;

• The choice of window sill color is, of course, a purely individual matter.. With white windows, everything seems to be clear, it’s stupid to put dark window sills on them. If the frames are colored, then, as a rule, ebbs are mounted, at least a tone darker than the frame;
• The width of the outer window sill directly depends on the size of the ledge, that is, the distance between the edge of the wall and the window frame. Plus, do not forget to add here 30 - 40 mm to the visor and take into account the angle of inclination of the ebb relative to the horizon;
• With the length of the outer window sill, the same is not so simple. To calculate it, you need to take the distance between the outer sections of the window opening. That is, we consider not along the length of the frame, but along the edges of the opening on the street. But that's not all. According to the rules, the ebb should go to the side walls by about 30 - 40 mm on each side. So in its purest form, the length of the ebb is the distance between the outer sections of the window opening, plus 60 - 80 mm for tolerances along the edges;

• The configuration of the ebb itself may be different. It is selected depending on the material from which the house is built. So the ebbs in a frame house or in a house with a ventilated facade will be radically different from the ebbs in a traditional brick or panel building. But no matter what shape the outer window sills have, they conditionally consist of three parts. This is a shelf on top, which is actually attached to the frame, the drainage itself and the drip. To make it clearer to you, the general scheme of the ebb is below.

Since we are talking about the cost of materials, it will not be superfluous to quote the average prices in Russia for such work from professionals. To give you a general idea, below I have compiled a small table. Perhaps, having familiarized yourself with it, you decide not to fool yourself and call specialists.

In general, installing a low tide on an average window in the budget version costs about 1150 rubles. Although if you add dismantling and various kinds of services that are not provided here, then the price can rise to 2500 rubles.

Subtleties of installation of an external window sill

Any such work begins with stripping the foundation. There is nothing complicated here, just remove all the debris and cut off the excess mounting foam, if any.

When installing windows, the masters do not always foam the perimeter of the frame with high quality. If you find such a marriage, do not be lazy and additionally blow out “weak” areas in your opinion with foam. After drying, of course, you need to cut off the excess.

Mounting foam is a very useful and convenient invention, but if it is not protected from the weather, it will quickly collapse. Under the window sill, the sun's rays will not reach the foam, but the top layer will pull moisture on itself, and when frost hits, the structure of this very top layer will simply tear.

If you do not take action, then the seal from the bottom of the frame will become unusable in 3 to 4 years. Protecting the mounting foam from moisture, frost and other troubles is quite simple. You need to close the opening with a vapor barrier membrane. It should be fixed at 2 points, on the frame itself or under the window sill and on the wall.

Note that any vapor barrier allows steam to pass only in one direction, there is an indication of this on the membrane itself. According to the laws of physics, steam always moves from indoors to outdoors, and when you attach the tape, this should be remembered.

Modern metal-plastic frames have the so-called passive ventilation. These are small holes around the perimeter of the frame. We will not now understand why it is needed, just remember. It is strictly forbidden to cover these openings with a window sill, slope, vapor barrier or anything else.

Now you can move on to one of the most important stages of work, the window sill pattern. Professionals, as a rule, cut out the ebb after the first measurement. For amateurs, I always recommend drawing a drawing, or rather, not even a drawing as such, but a light sketch.

There is one important nuance here. Metal window sills are cut out in such a way that on the lines of contact with the side slopes and the wall, the ebb comes to the vertical surface of the slope by at least 10 mm. In plastic ebbs, the side lining plays the role of this side.

Such a side is needed so that water does not flow under the windowsill, and also to protect the ebb from excess dampness.

At the final stage, the direct installation of the ebb is performed. To tell the truth, if the window sill is correctly cut out, then even an amateur will cope with the installation. The angle of inclination of the ebb must be at least 10º.

On some frames there is a special groove for installing a window sill, if it is not there, then we choose a place arbitrarily. The main thing here is not to accidentally close the ventilation holes in the frame and observe the angle of the ebb.

The ebb is attached to the frame with metal screws with a pitch of about 300 mm. In places where the ebb comes into contact with the frame, that is, under the mounting shelf, as well as on the slopes, it is desirable to apply a layer of sealant.

For soundproofing, so that the rain does not drum too loudly on the windowsill, mounting foam is usually blown under the tide. But until it hardens at low tide, it is advisable to put some kind of weighting. Instead of foam, some craftsmen stick a strip of foam plastic about 1 cm thick under the windowsill. The effect is almost the same.

Conclusion

I hope the instructions above will help you install window tides yourself. But even if you decide to hire people, this instruction will make it possible to control them. The photo and video in this article contains additional information on the topic. If you have any questions, write them in the comments, I will try to help.

September 18, 2016

If you want to express gratitude, add a clarification or objection, ask the author something - add a comment or say thanks!

Ebb and flow is the periodic rise and fall of the water level in the oceans and seas.

Twice during the day, with an interval of about 12 hours and 25 minutes, the water near the coast of the ocean or the open sea rises and, if there are no barriers, sometimes floods large spaces - this is a tide. Then the water goes down and recedes, exposing the bottom - this is the ebb. Why is this happening? Even ancient people thought about this, they noticed that these phenomena are associated with the moon. The main cause of the tides was first pointed out by I. Newton - this is the attraction of the Earth by the Moon, or rather, the difference between the attraction of the Moon of the entire Earth as a whole and its water shell.

Ebb and flow explained by Newton's theory

The attraction of the Earth by the Moon is made up of the attraction of the individual particles of the Earth by the Moon. Particles that are currently closer to the Moon are attracted by it more strongly, and more distant ones are weaker. If the Earth were absolutely solid, then this difference in the force of attraction would not play any role. But the Earth is not an absolutely solid body, therefore the difference in the attractive forces of particles located near the surface of the Earth and near its center (this difference is called the tide-forming force) displaces the particles relative to each other, and the Earth, primarily its water shell, is deformed.

As a result, on the side that faces the Moon, and on its opposite side, the water rises, forming tidal protrusions, and excess water accumulates there. Due to this, the water level in other opposite points of the Earth at this time decreases - there is a low tide here.

If the Earth did not rotate, and the Moon remained motionless, then the Earth, together with its water shell, would always retain the same elongated shape. But the Earth rotates, and the Moon moves around the Earth in about 24 hours and 50 minutes. With the same period, tidal protrusions follow the Moon and move along the surface of the oceans and seas from east to west. Since there are two such protrusions, a tidal wave passes over each point in the ocean twice a day with an interval of about 12 hours and 25 minutes.

Why is the height of the tidal wave different

In the open ocean, the water rises slightly during the passage of a tidal wave: about 1 m or less, which remains almost imperceptible to sailors. But off the coast, even such a rise in the water level is noticeable. In bays and narrow bays, the water level rises much higher during high tides, since the coast prevents the movement of the tidal wave and water accumulates here during the entire time between low tide and high tide.

The largest tide (about 18 m) is observed in one of the bays on the coast in Canada. In Russia, the highest tides (13 m) occur in the Gizhiginskaya and Penzhinskaya bays of the Sea of ​​Okhotsk. In inland seas (for example, in the Baltic or Black), the tides are almost imperceptible, because masses of water moving along with the ocean tidal wave do not have time to penetrate into such seas. But all the same, in every sea or even lake, independent tidal waves arise with a small mass of water. For example, the height of the tides in the Black Sea reaches only 10 cm.

In the same area, the height of the tide varies, since the distance from the Moon to the Earth and the greatest height of the Moon above the horizon change over time, and this leads to a change in the magnitude of tide-forming forces.

Tides and Sun

The sun also influences the tides. But the tidal forces of the Sun are 2.2 times less than the tidal forces of the Moon.

During the new moon and full moon, the tidal forces of the sun and moon act in the same direction - then the highest tides are obtained. But during the first and third quarters of the moon, the tidal forces of the sun and moon counteract, so the tides are smaller.

Tides in the air shell of the Earth and in its solid body

Tidal phenomena occur not only in the water, but also in the air shell of the Earth. They are called atmospheric tides. Tides also occur in the solid body of the Earth, since the Earth is not absolutely solid. Vertical oscillations of the Earth's surface due to tides reach several tens of centimeters.

The practical use of ebb and flow

A tidal power plant is a special type of hydroelectric power plant that uses the energy of the tides, but in fact the kinetic energy of the rotation of the Earth. Tidal power plants are built on the shores of the seas, where the gravitational forces of the Moon and the Sun change the water level twice a day. Water level fluctuations near the coast can reach 18 meters.

In 1967, a tidal power station was built in France at the mouth of the Rance River.

In Russia, since 1968, an experimental TPP has been operating in Kislaya Bay on the coast of the Barents Sea.

There are PES and abroad - in France, Great Britain, Canada, China, India, the USA and other countries.

Ebb and flow are natural phenomena that many people have heard and observed, especially those living on the coast of the sea or ocean. What are ebbs and flows, what power lies in them, why they arise, read in the article.

The meaning of the word "tide"

According to the explanatory dictionary of Efremova, the tide is a natural phenomenon when the level of the open sea rises, that is, it rises, and this is periodically repeated. What does tide mean? According to Ozhegov's explanatory dictionary, a tide is a tributary, an accumulation of a moving one.

Tide - what is it?

This is a natural phenomenon when the water level in the ocean, sea or other body of water regularly rises and falls. What is a tide? This is a response to the influence of gravitational forces, that is, the forces of attraction possessed by the Sun, Moon and other tidal forces.

What is a tide? This is the rise of water in the ocean to its highest level, which occurs every 13 hours. Low tide is the reverse phenomenon in which the water in the ocean falls to its lowest level.

Ebb and flow - what is it? This is a fluctuation in the water level that occurs periodically vertically. This natural phenomenon, ebbs and flows, occurs because the position of the Sun and Moon relative to the Earth changes along with the rotational effects of the Earth and the features of the relief.

Where do the tides and tides occur?

These natural phenomena are observed in almost all seas. They are expressed in a periodic increase and decrease in the water level. There are tides on opposite sides of the Earth, which lie next to the line directed towards the Sun and Moon. The formation of a hump on one side of the Earth is influenced by the direct attraction of celestial bodies, and on the other - their least attraction. Since the Earth rotates, two high tides and the same number of low tides are observed at each point near the seashore in one day.

The tides are not the same. The movement of water masses and the level to which water rises in the sea depend on many factors. This is the latitude of the area, the outline of the land, atmospheric pressure, wind strength and much more.

Varieties

High and low tides are classified according to the duration of the cycle. They are:

• Semi-daily, when two high tides and two low tides occur per day, that is, the transformation of the space of water in the ocean or on the sea consists in full and incomplete waters. The parameters of the amplitudes, which alternate with each other, practically do not differ. They look like a curved sinusoidal line and are localized in the waters of such a sea as the Barents Sea, off the coast of the White Sea, and are distributed almost throughout the entire territory of the Atlantic Ocean.
• per diem- characterized by one high tide and the same number of low tides during the day. Such natural phenomena are also observed in the Pacific Ocean, but very rarely. So, if the Earth's satellite passes through the equatorial zone, standing water is observed. But if there is a declination of the Moon with the smallest indicator, tides of low power are observed, which have an equatorial character. If the numbers are higher, tropical tides are formed, accompanied by significant force.
• mixed when semidiurnal or diurnal tides with an irregular configuration predominate in height. For example, in semidiurnal changes in the level of the hydrosphere, there is a similarity with semidiurnal tides in many ways, and in diurnal changes with tides of the same time, that is, diurnal, which depend on the degree with which the Moon inclines in a given period of time. Mixed tides are more common in the Pacific Ocean.

• Abnormal tides- are characterized by rises and falls of water that do not fit any description on various grounds. The anomaly has a direct connection with shallow water, as a result of which the cycle itself of both the rise and fall of water changes. This process especially affects the mouth of rivers. Here the tides are shorter than the tides. Similar cataclysms characterize certain sections of the English Channel, as well as the currents of the White Sea.

However, the tides are practically not noticeable in the seas, which are called inland, that is, separated from the ocean by straits, narrow in width.

What generates tides?

If the forces of gravity and inertia are violated, tides arise on the Earth. The natural phenomenon of tides is more pronounced near the ocean shores. Here, twice a day, to varying degrees, the water level rises and falls the same number of times. This happens because humps form on the surface of two opposite areas of the ocean. Their position is determined depending on the position of the Moon and the Sun.

Moon influence

The moon has a greater influence on the occurrence of tides than the sun. As a result of numerous studies, it was found that the point on the earth's surface closest to the moon is affected by external factors by 6% more than the most distant one. In this regard, scientists have concluded that due to this delimitation of forces, the Earth is moving apart in the direction of such a trajectory as the Moon-Earth.

Taking into account the fact that the Earth rotates around its axis in one day, a double tidal wave during this time passes along the created extension, more precisely, its perimeter, twice. As a result of this process, double "valleys" are created. Their height in the World Ocean reaches a two-meter mark, and on land - 40-43 centimeters, so for the inhabitants of the planet this phenomenon goes unnoticed. We do not feel the power of the tides, no matter where we are: on land or on water. Although a person is familiar with a similar phenomenon, observing it on the coastline. Sea or ocean waters sometimes gain a sufficiently large height by inertia, then we see waves rolling ashore - this is a tide. When they roll back, the tide is out.

Influence of the Sun

The main star of the solar system is located far from the Earth. For this reason, its impact on our planet is little noticeable. The sun is more massive than the moon, if we consider these celestial bodies as sources of energy. But a large distance between the luminary and the Earth affects the amplitude of solar tides, it is two times less than similar processes on the Moon. When there is a full moon and the moon is growing, the celestial bodies - the Sun, Earth and Moon - have the same location, as a result of which the solar and lunar tides add up. The sun has little influence on the tides during the period when the gravitational forces from the Earth go in two directions: towards the Moon and the Sun. At this time, the tide rises and the tide falls.

Land on the planet covers 30% of the surface. The rest is covered by oceans and seas, which are associated with many mysteries and natural phenomena. One of them is the so-called red tide. This phenomenon is amazing in its beauty. It is observed off the coast of the Gulf of Florida and is considered the largest, especially in such summer months as June or July. How often a red tide can be observed depends on a banal reason - human pollution of coastal waters. The waves have a rich bright red or orange hue. This is an amazing sight, but admiring it for a long time is dangerous to health.

The fact is that algae give color to the water during flowering. This period is very intensive, plants release a large amount of toxins and chemicals. They do not completely dissolve in water, some of them are released into the air. These substances are very harmful to plants, animals, seabirds. Often people suffer from them. Especially dangerous for humans are molluscs, which were caught from the "red tide" zone. A person, using them, gets severe poisoning, often leading to death. The fact is that the level of oxygen during the tide goes down, ammonia and hydrogen sulfide appear in the water. They are the cause of poisoning.

What are the highest tides in the world?

If the shape of the bay is funnel-shaped, when a tidal wave enters it, the shores are compressed. Because of this, the height of the tide increases. Thus, the height of the tidal wave off the eastern coast of North America, namely in the Bay of Fundy, reaches approximately 18 meters. In Europe, Brittany, near Saint-Malo, has the highest tides (13.5 meters).

How do high and low tides affect the inhabitants of the planet?

Marine inhabitants are especially susceptible to these natural phenomena. The tides have the greatest influence on the inhabitants of the waters in the coastal strip. As the level of the earth's water changes, organisms with a sedentary lifestyle develop. These are mollusks, oysters, which the change in the structure of the water element does not prevent from multiplying. This process is much more active during high tides.

But for many organisms, periodic fluctuations in the water level bring suffering. It is especially difficult for animals of small size, many of them completely change their habitat during high tides. Some move closer to the shore, while others, on the contrary, are carried away by the wave deep into the ocean. Nature, of course, coordinates all changes on the planet, but living organisms adapt to the conditions presented by the activity of the Moon, as well as the Sun.

What role do tides play?

What are the ebb and flow, we have dismantled. What is their role in human life? These natural phenomena have a titanic power, which, unfortunately, is currently little used. Although the first attempts in this direction were made in the middle of the last century. In different countries of the world, they began to build hydroelectric power plants using the power of a tidal wave, but so far there are very few of them.

The significance of the tides is also enormous for navigation. It is during their formation that ships enter the river for many kilometers upstream to unload goods. Therefore, it is very important to know when these phenomena will occur, for which special tables are compiled. Ship captains use them to determine the exact time of the onset of tides and their height.

What is ebb and flow

On many sea coasts, one can observe how the water level drops evenly at regular intervals and only viscous soil remains. This process is called reflux. However, after a few hours the water level rises again and the soil on the shore is again covered with water. This process is called tide. The water level changes regularly twice a day.

When the tides turn to ebbs

High tide and low tide regularly replace each other: the low tide is followed by the high tide, followed by the next low tide. The highest water level in the sea or ocean at high tide is called high water, and the lowest at low tide is called low water, respectively. The cycle "high tide - low tide - low tide - high tide - high tide" is 12 hours and 25 minutes. This means that high and low tides can be observed twice a day.

How ebbs and flows happen

The force of gravity of the Moon causes the formation of the first tidal crest in the sea on the side of the Earth facing it. Due to the laws of physics associated with the rotation of the Earth and the emergence of centrifugal force, a second tidal crest is formed on the opposite side of the Earth, even more powerful than the first. Therefore, here the water level rises.

Between these two ridges, it sinks, and the tide is out! And the Sun, by the force of its attraction, influences the Earth, as well as the ebbs and flows. But the impact force of the Sun is much less than that of the Moon, although the mass of the Sun is 30 million times the mass of the Moon. The reason for this lies in the fact that the Sun is 390 times farther from the Earth than the Moon is from the Earth.

First tidal hydroelectric plant

Thanks to the ebb and flow, that is, the rise and fall of the sea level, a lot of energy is generated. It can be used to generate electricity. The first and currently largest tidal hydroelectric power plant in the world was built in the estuary (narrow bay of the mouth) of the Rane River (Saint-Malo, France) and was put into operation in 1966. There, the difference between low tide and high tide is very large (amplitude 8.5 meters).

What other factors affect the tides

In addition to the forces of gravity, cosmic bodies, the Moon and the Sun, other factors affect the tides: the rotation of the Earth slows down the tides, the banks do not allow water to rise. In addition, high and low tides are affected by strong storms, in which the outflow of sea water from the coast is difficult. Therefore, its level in such places is much higher than during normal high tide. The tides are also affected by the strength of the wind: if it blows from the shore, the water level drops significantly below normal.

Are the ebbs and flows always visible?

They say that in some seas, for example, in the Mediterranean or the Baltic, there are no ebbs and flows. Of course, this is not so, because they are found in all seas. However, in the Mediterranean and Baltic Seas, the difference between high and low water (high and low tide amplitude) is so insignificant that it is practically imperceptible. In the North Sea, on the contrary, the ebbs and flows are very clearly distinguished.

Tidal waves originate in the oceans and move into the marginal seas. If the marginal sea is connected to the ocean only by a narrow strait, as, for example, the Mediterranean Sea, the tidal waves either do not reach it or are very weakened. The North Sea is connected to the Atlantic Ocean by a wide strait, so tidal waves easily reach the coast and the tide is clearly visible in this place.

What is a spring tide

Especially strong ebbs and flows can be observed for 14 days, when the Moon and the Sun during the full moon and new moon (syzygy) are in line with the Earth. At this time, the tide-forming forces of both celestial bodies, acting in the same direction, are summed up and increase the tide. The so-called spring tide begins, when full water rises the highest. Accordingly, at low tide, the water drops to the lowest level.

What is the amplitude of the ebb and flow

The difference between high and low tide at high and low tide is called amplitude. At the same time, the forces of attraction of the Sun and the Moon play their role: when they reinforce each other, the amplitude increases (syzygy tide), and when the forces of attraction weaken, the amplitude, on the contrary, decreases (quadrature tide). In the open sea, the amplitude of the tide does not exceed 50 centimeters. On the banks, on the contrary, it is much larger.

So, on the coast of the North Sea of ​​Germany, for example, it is 2-3 meters, on the English coast of the North Sea - up to 8 meters, and in the bay of Saint-Malo (France) in the English Channel - up to 11 meters. This can be explained by the fact that in shallow waters, tidal waves, like all others, lose speed and slow down, as a result of which the water level rises.

What is quadrature tide

For seven days after the full moon and new moon, the Sun, Earth and Moon are no longer in a straight line. When the tidal forces of the Moon and the Sun interact at right angles to each other, a quadrature tide begins: high water rises slightly, and the level of low water practically does not fall.

What are tidal currents

Tides not only cause the water level to rise and fall. While the sea rises and falls, the water moves back and forth. In the open sea, this is hardly noticeable, but in the straits and bays, where the movement of water is limited, one can observe tidal and ebb currents. In the first case (tidal current) it is directed towards the shore, in the second case (ebb current) it is directed in the opposite direction. A change in tidal currents is usually referred to by experts as a turn. At the moment of turning, the water is in a calm state, and this phenomenon is called the "dead center" of the tide.

Where are the highest amplitudes of ebbs and flows observed?

In the Bay of Fundy on the east coast of Canada, you can observe the largest tide amplitudes on our planet. This means that the difference between high and low water during high and low tide is the maximum here. At spring tide, it reaches 21 meters. In the past, fishermen set up nets at high tide and fished from them at low tide: an unusual way of fishing!

How does a storm surge occur?

A storm tide is a tide when water rolls especially high on the coast. It occurs due to strong winds that blow towards the land and come along with the spring tide. Recall: during it, high water rises especially high, and low water falls especially low. This happens during the periods of full moon and new moon.

The strength of the winds and their duration lead to the occurrence of a storm tide, when the water rises more than a meter above the midpoint of the tide. There is a strong storm tide, in which the water rises 2.5 meters, and super-strong - when the water rises more than 3 meters.

How fast can tidal currents reach

In the depths of the oceans, tidal currents reach speeds of about a kilometer per hour. In narrow straits, it can range from 15 to 20 kilometers per hour.