Where does water come from in the sea? Why is there salty water in the sea? How is water salinity determined?

Anyone who was on the beach could see that the water in the sea tasted salty. But where does salt come from if fresh water enters the ocean through rains, rivers, etc.? Why is the sea salty and has it always been like this - time to figure it out!

How is water salinity determined?

Salinity refers to the salt content in water. Most often, salinity is measured in " ppm » (‰). Permille is one thousandth of a number. Let's give an example: a water salinity of 27 ‰ will mean that one liter of water (this is approximately 1000 grams) contains 27 grams of salt.

Water with an average salinity of 0.146 ‰ is considered fresh.

Average The salinity of the World Ocean is 35 ‰. What makes water salty is sodium chloride, also known as salt. Among other salts, its share in sea water is the highest.

The saltiest sea is the Red Sea. Its salinity is 41‰.

Where does salt come from in the seas and oceans?

Scientists still disagree about whether seawater was originally salty or acquired such properties over time. Depending on the versions, they are considered and different sources the appearance of salts in the World Ocean.

Rains and rivers

Fresh water always has no a large number of salts, and rainwater is no exception. It always contains traces of dissolved substances that were captured during its passage through the atmosphere. Getting into the soil, rainwater washes away a small amount of salts and eventually carries them to lakes and seas. From the surface of the latter, water intensively evaporates, falls again in the form of rain and brings new minerals from the land. The sea is salty because all the salts remain in it.

The same principle applies to rivers. Each of them is not completely fresh, but contains small amounts of salts captured on land.

Confirmation of the theory - salt lakes

Proof that salt comes through rivers are the saltiest lakes: the Great Salt Lake and the Dead Sea. Both are about 10 times saltier than seawater. Why are these lakes salty?, while most of the world's lakes are not?

Lakes are usually temporary storage areas for water. Rivers and streams bring water to lakes, and other rivers carry it away from these lakes. That is, water comes in from one end and leaves from the other.

The Great Salt Lake, the Dead Sea and other salt lakes have no outlets. All the water that flows into these lakes leaves only through evaporation. When water evaporates, dissolved salts remain in bodies of water. Thus, some lakes are salty because:

• the rivers carried salt to them;
• the water in the lakes evaporated;
• the salt remained.

Over many years, salt in the lake water has accumulated to its current level.

Interesting fact: The density of salt water in the Dead Sea is so high that it practically pushes a person out, preventing him from sinking.

The same process made the seas salty. Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and replenish rivers, but the salts remain in the ocean.

Hydrothermal processes

Rivers and rain are not the only source of dissolved salts. Not long ago, they were discovered on the ocean floor hydrothermal vents. They represent places where seawater has seeped into the rocks of the Earth's crust, become hotter, and is now flowing back into the ocean. Along with it comes a large amount of dissolved minerals.

Submarine volcanism

Another source of salts in the oceans is underwater volcanism - volcanic eruption underwater. It is similar to the previous process in that seawater reacts with hot volcanic products and dissolves some of the mineral components.

Will the seas be saltier?

Most likely no. In fact, the sea has had roughly the same salt content for hundreds of millions, if not billions of years. The salt content has reached a steady state. The fact is that part of the salts goes to the formation of mineral rocks at the bottom - this compensates for the influx of new salts.

Summary

There is no mystery in the answer to the question: “Why is the sea salty?” Salt is deposited by rain and rivers, hydrothermal and volcanic processes on the ocean floor.

Having visited the beach for the first time, the child asks his parents: why is the water in the sea salty? This simple question baffles adults. After all, everyone knows that a bitter aftertaste will definitely remain on the lips and the whole body. Why is the sea salty? We begin to reason: fresh rivers flow into this part of the World Ocean. So it can't taste that bad! But you can’t go against the facts: the water is not fresh. Let's figure out at what stage the initial composition of H2O changes.

Why is the salinity increased?

There are several theories about this. Some scientists believe that salt remains from the evaporated water of flowing rivers, others - that it is washed out of rocks and stones, others associate this compositional feature with the action of volcanoes... Let's begin to consider each version in order:

The reservoir becomes salty from the water of the rivers that flow into it. Strange pattern? Not at all! Although river moisture is considered fresh, it still contains salt. Its content is very small: seventy times less than in the vast depths of the World Ocean. Therefore, falling into great body of water, rivers desalinate its composition. But the river water gradually evaporates, but the salt remains. The volumes of impurities in the river are small, but over billions of years a lot of them accumulate in sea water.

Salts flowing from rivers into the sea settle on its bottom. From them, huge blocks of stone and rocks are formed on the ocean floor over thousands of years. Year after year, the current destroys any stones, leaching easily soluble constituent substances from them. Including salt. Of course, this process is long, but inevitable. Particles washed out of rocks and rocks give the ocean an unpleasant, bitter taste.

Underwater volcanoes eject into environment many substances, including salts. During the formation of the earth's crust, volcanic activity was very high. They released acidic substances into the atmosphere. Frequent acid rain formed seas. Accordingly, first the water in components the ocean was acidic. But the alkaline elements of the soil - potassium, magnesium, calcium, etc. - reacted with acids and formed salts. Thus, water in various places of the ocean acquired the characteristics that are now familiar.

Other assumptions known today are related

• with the winds bringing salt into the water;
• with soils, passing through which fresh liquid is enriched with salts and enters the ocean;
• with salt-forming minerals located under the ocean floor and supplied through hydrothermal vents.

It is probably correct to combine all the hypotheses in order to understand the ongoing process. Nature gradually built all its ecosystems, closely intertwining things that were incompatible at first glance.

Where is the highest concentration of salt?

Sea water- a liquid that is most common on earth. It’s not for nothing that many people associate vacations primarily with the beach and coastal waves. Surprisingly, the mineral composition of the liquid in different bodies of water never coincides. There are many reasons for this. For example, salinity depends on the intensity of evaporation fresh water, on the number of rivers, types of inhabitants and other factors. Which sea is the saltiest?

The answer is given by statistics: the Red Sea is rightfully called the saltiest. One liter of its water contains 41 grams of salts. If we compare with other reservoirs, then in a liter of liquid from the Black there are 18 grams of various salts, in the Baltic this figure is even lower - 5 grams. The chemical composition of Mediterranean is 39 grams, which is still lower than the above characteristics of Red. In ocean water - 34 grams.

Reasons for the unique feature of the Red Sea:

On average, about 100 mm of precipitation falls above the surface per year. This is very little, considering that about 2000 mm of water evaporates per year.

No rivers flow into this reservoir; it is replenished only by precipitation and waters from the Gulf of Aden. And its water is also salty.

The reason is also the intensive mixing of water. In winter and summer, the layers of liquid change. Evaporation occurs in the upper layer of water. The remaining salts fall down. Therefore, the salinity of water in this part of the water expanse increases significantly.

The Dead Sea is sometimes called the saltiest. Its waters contain 340 grams of salt per liter of water. That’s why it’s dead: the fish die in it. But some features of this body of water do not allow it to be considered a sea: it does not have access to the ocean. Therefore, it is more correct to call this body of water a lake.

Since ancient times, people have been looking for an answer to the question of why the sea is salty. In fact, the water of all seas and oceans has this taste, only the level of salinity is different for everyone. The biological diversity of a particular sea largely depends on this indicator.

But first, about salt. Where does it come from? Both soils and rocks contain particles of various salts, and rainwater dissolves them. Rain streams flow into rivers, which carry salt particles to the sea. And then everything is as in the school textbook: under the influence sun rays the process of evaporation occurs (water evaporates and salt accumulates in sea ​​depths), and in the form of precipitation it returns to the earth again, washing away salt particles from the soil...

But this is only part of the answer to the question “why is the sea salty?” The other part must be looked for at the bottom of the sea. The salinity of the sea largely depends on the composition of the seabed, or more precisely on the rocks that form it. The chemical composition practically does not change, and since each sea or ocean has its own, they are able to survive, as a rule, only on their own territory. They cannot be moved from one sea to another. The intensity of evaporation is also of great importance - the higher it is, the more salt is concentrated in sea water.

In general, there are many other reasons that influence the level of sea salinity. For example, the salinity of the Black Sea is influenced by the remoteness of the ocean, as well as the fact that many European deep rivers They carry their waters here. The huge flow significantly reduces the salinity level, which leads to a decrease biological diversity Black Sea. In comparison with the Mediterranean, the number of inhabitants of the Black Sea depths is much more modest, and the diversity leaves much to be desired: here you will not find starfish and urchins, cuttlefish and octopuses, and squid. Vegetable world The Black Sea is also much poorer.

Why is the sea salty? There is one more point, the presence of which cannot be ignored when answering this question - areas of land washed by the sea or ocean. As you can see, the answer is not as simple as it might seem at first glance.

Comparing the Black and Mediterranean seas, their water worlds, the latter was in a more favorable position, due to more high level salinity. What is the saltiest sea in the world? The answer to this question is simple - Red. If in the Black Sea the salt content is 17 grams per liter of water (in the Baltic - only five grams), then in the Red Sea this figure is more than twice as high - 35-41 grams per liter (depending on the coast).

This is due, first of all, to the absence of rivers flowing into the Red Sea, and they are known to carry water, which in some way dilutes the sea, reducing the concentration of salts. Here the concentration is slowly but invariably growing. At the same time, denser layers of water sink lower, cooler water is forced into the upper layers, carrying out natural mixing. In addition, the absence of rivers allows sea water to maintain its transparency and purity. And wealth largely depends on this underwater world: The diversity and beauty of the inhabitants of the Red Sea is simply amazing.

Answering questions about why the sea is salty, and which one cannot help but remember the Dead Sea, which, being drainless, is also called a lake. Extremely high concentration salts in its water are constantly maintained by mineral springs, which make the water not only the saltiest, but also simply unique in its composition, it is inimitable. It is the water, as well as the famous silt mud, which, by the way, also has a high content of mineral salts, that attracts hundreds of thousands of tourists to the shores, coming from all over the world to improve their health.

Why is the sea salty, and where does the salt come from? This is a question that has interested people for a long time. There is even a folk tale about this.

As folklore explains

Whose legend this is, and who exactly came up with it, is no longer known. But among the peoples of Norway and the Philippines it is very similar, and the essence of the question of why the sea is salty is conveyed in the fairy tale as follows.

There were two brothers - one rich, and the other, as usual, poor. And no, to go and earn bread for his family - the poor man goes for alms to his stingy rich brother. Having received a half-dried ham as a “gift”, the poor man, in the course of some events, falls into the hands of evil spirits and exchanges this very ham for a stone millstone, modestly standing outside the door. And the millstone is not simple, but magical, and can grind whatever your heart desires. Naturally, the poor man could not live quietly, in abundance, and not talk about his miraculous find. In one version, he immediately built a palace for himself on one day, in another, he threw a feast for the whole world. Since everyone around him knew that just yesterday he had lived poorly, those around him began to ask questions about where and why. The poor man did not consider it necessary to hide the fact that he had a magic millstone, and therefore many hunters appeared to steal it. The last person to do so was the salt merchant. Having stolen the millstone, he did not ask to grind money, gold, or overseas delicacies for him, because having such a “device”, he could no longer engage in the salt trade. He asked to grind salt for him so that he would not have to swim across the seas and oceans for it. A miracle millstone started up and ground so much salt that it sank the unfortunate merchant’s ship, and the millstone fell to the bottom of the sea, continuing to grind salt. This is how people explained why the sea is salty.

Scientific explanations of the fact

The main source of salts in the seas and oceans are rivers.

Yes, those rivers that are considered fresh (more correctly, less salty, because only the distillate is fresh, that is, devoid of salt impurities), in which the salt value does not exceed one ppm, make the seas salty. This explanation can be found in Edmund Halley, a man known for the comet named after him. In addition to space, he studied more mundane issues, and it was he who first put forward this theory. The rivers constantly bring great amount waters along with small admixtures of salts into the depths of the sea. There the water evaporates, but the salts remain. Perhaps earlier, many hundreds of thousands of years ago, ocean waters were completely different. But they add another factor that may explain why the seas and oceans are salty - volcanic eruptions.

Chemicals from volcanoes bringing salt to the sea

At a time when Earth's crust was in a state of constant formation, there were frequent ejections of magma with incredible amounts various elements to the surface - both on land and under water. Gases, indispensable companions of eruptions, mixed with moisture and turned into acids. And they, in turn, reacted with the alkali of the soil, forming salts.

This process is still happening now, because seismological activity, although much lower than it was millions of years ago, is still present.

In principle, other facts explaining why the water in the sea is salty have already been studied: salts enter the seas from the soil through movement by precipitation and winds. Moreover, in every open body of water chemical composition The main earth's liquid is individual. To the question of why the sea is salty, Wikipedia answers in the same way, only emphasizing the harm of sea water for the human body as drinking water, and its benefits when taking baths, inhaling, and the like. It’s not for nothing that sea salt is so popular, which is even added to food instead of table salt.

Unique mineral composition

We have already mentioned that the mineral composition is unique in each body of water. Why the sea is salty and how salty it is is determined by the intensity of evaporation, that is, the wind temperature on the reservoir, the number of rivers that flow into the reservoir, the richness of flora and fauna. So, everyone knows what kind of sea is the Dead Sea, and why it is called that.

Let's start with the fact that it is incorrect to call this body of water a sea. It is a lake because it has no connection with the ocean. It was called dead because of the huge proportion of salts - 340 grams per liter of water. For this reason, no fish can survive in a body of water. But as a health resort, the Dead Sea is very, very popular.

Which sea is the saltiest?

But the right to be called the saltiest belongs to the Red Sea.

There are 41 grams of salts in a liter of water. Why is the Red Sea so salty? Firstly, its waters are replenished only by precipitation and the Gulf of Aden. The second one is also salty. Secondly, the evaporation of water here is twenty times greater than its replenishment, which is facilitated by placement in tropical zone. If it were a little further south, closer to the equator, and the amount of precipitation characteristic of this zone would dramatically change its content. Due to its location (the Red Sea is located between Africa and the Arabian Peninsula), it is also the warmest sea among all those on planet Earth. His average temperature- 34 degrees Celsius. The entire system of possible climatic and geographical factors made the sea what it is now. And this applies to any body of salt water.

The Black Sea is one of the unique compositions

For the same reasons, one can single out the Black Sea, whose composition is also unique.

Its salt content is 17 ppm, and these are not entirely suitable indicators for marine inhabitants. If the fauna of the Red Sea amazes any visitor with its diversity of colors and life forms, then do not expect the same from the Black Sea. Most of the “settlers” of the seas cannot tolerate water with less than 20 ppm salts, so the diversity of life is somewhat reduced. But it contains many useful substances that contribute to active development single- and multicellular algae. Why is the Black Sea half as salty as the ocean? This is primarily due to the fact that the size of the territory from which river water flows into it exceeds the sea area itself by five times. At the same time, the Black Sea is very closed - it is connected to the Mediterranean only by a thin strait, but otherwise it is surrounded by land. The salt concentration cannot become very high due to intensive desalination by river waters - the first and most important factor.

Conclusion: we see a complex system

So why is the water in the sea salty? This depends on many factors - river waters and their saturation with substances, winds, volcanoes, the amount of precipitation, the intensity of evaporation, and this, in turn, affects the level and diversity of living organisms in it, both representatives of flora and fauna. This is a huge system with a large number of parameters that ultimately make up an individual picture.

The salinity of water in the oceans is almost everywhere close to 35 ‰, but the water in the seas has an unevenly distributed salinity.

The least saline is the water of the Gulf of Finland and the northern part of the Gulf of Bothnia, which are included in the water area Baltic Sea. The most saline water is the Red Sea and East End Mediterranean Sea. Salt lakes such as the Dead Sea can have significant higher level salt content.

Sea water is slightly alkaline, pH varies from 7.5 to 8.4. The relatively high pH stability is associated with the presence of a carbonate buffer system. The borate system is somewhat less important for maintaining pH. The pH value is highest at the sea surface; with depth it decreases slightly. In desalinated areas, the pH value can drop to neutral and even slightly acidic.

Where does the salt in the sea come from?

The fact is that rivers wash the mineral salts contained in the soil out of the soil and carry them grain by grain into the sea. Over the years and millennia, there is more and more salt in the sea. She never leaves the sea. While the water evaporates, it turns into clouds. Then it pours onto the earth again in the form of rain, filling the rivers and returning to the sea again, adding a little more salt to it.

It turns out that the water in the World Ocean was initially fresh, but gradually the rivers “salted” it. Fresh water in the ocean could have come from... comets. At the very beginning of its existence, our Earth was subjected to real bombardment by comets. And, as you know, most comets have an icy core. As a result of the massive melting of this ice, the first ocean could have appeared. This is one of the hypotheses.

But many scientists believe that the water in the seas and oceans was originally salty. The first ocean was filling acid rain, which spilled onto the earth as a result of massive volcanic eruptions at the very beginning of the life of our planet. These acids corroded rocks, entering chemical compounds with their constituent substances. As a result of these chemical reactions and that one was formed salty water, which fills the modern oceans.