Why are the seas and oceans salty? Why is the sea salty? All oceans are salty.
Since childhood, we have become accustomed to the fact that the water in the sea, unlike rivers, is salty. Even though we had never been to the sea, we already knew about it, because our parents, friends told us about it, we read about it in books.
Today we take this fact for granted, and don’t really think about why the seas and oceans are salty. However, the time has come to consider this issue within the framework of articles on our website so that it no longer bothers you in the future.
Why is the water in the seas and oceans salty?
As you know, water has enormous potential and power. This is most eloquently demonstrated by all kinds of natural disasters, which were caused by various tsunamis and hurricanes. Water can easily destroy many things, but it takes time, sometimes even a very long time.
This same destructive effect of water does not stop at all kinds of mountains, rocks and other natural structures that store many different chemical elements, including those containing salt. During the existence of the earth, all kinds of bodies of water present in the world's oceans destroyed and dissolved many objects that were capable of saturating the water with salts. However, the question arises as to why oceans and seas are always salty, but rivers, in contrast, are not.
And here it is necessary to remember such a concept as the water cycle in nature. We remember from school that water continuously moves through the biosphere of our planet. However, now, using the example of this phenomenon, it is necessary to trace the movement of salts, which, according to the most plausible and rational theories, has occurred since ancient times as follows:
- Rivers along their path sharpened stones, rocks, dissolved all possible minerals and other substances, absorbing salt from them.
- Water from the rivers flowed along its bed to the point where it flowed into the seas.
- The seas and oceans were saturated with salt water from rivers.
Of course, the water cycle also has a further effect - evaporation, which occurs both in rivers and in seas, as well as oceans. However, it is important to understand that during the process of evaporation, water goes into the clouds, and the salt with which it was saturated remains in the seas and oceans. The cyclical repetition of this process, which took place over several millennia, has led to the fact that today the seas and oceans consist of salt water.
As for the rivers, they continue to destroy all kinds of minerals and carry salt into the world's oceans, but the salt content in fresh water is so low that it is almost impossible for humans to feel it.
Geography
Natural science
Why is the sea salty?
“Why is the sea salty?” - one of children's favorite summer questions. In our new column “Why” we will regularly answer the most interesting questions of preschoolers and schoolchildren in clear and simple language, as well as hold exclusive competitions!Why is the sea salty? Why does a hedgehog need needles? Why did they add “-s” to many words in the last century? Why do cats purr and what do they do? Is it possible to create a time machine according to the laws of physics? As a parent or teacher of primary and secondary schools, you will hear these questions more than once. We will be happy to answer them.
Why is the sea salty?
The answer to this question must begin with an explanation of where the water in the sea and ocean comes from. In rivers we find springs and springs - underground springs, but where does the water, and salty one, come from in the sea?
The reserves of both the Black Sea and the Atlantic Ocean are replenished with fresh water from rivers and precipitation in the form of snow or rain. Both consist of fresh water(actually also salty, just in a very small concentration). But unlike rivers, water from oceans and seas does not flow anywhere, but only evaporates when exposed to the sun’s rays. When evaporation occurs, the salts remain.
Another factor in the salinity of the sea is the movement of the rivers themselves flowing into it. On the way to the seas and oceans, river flows wash the salts that make up the stone out of the rocks and bring them with them to the sea, albeit in small quantities.
It turns out that the sea has become salty? Was it fresh before? No, that's not true. The main reason, which modern scientists agree with, is the process of formation of the sea itself, which was just as salty millions of years ago. The fault for this is not the rivers, which did not exist then, but the volcanoes that covered our planet.
The water of the primary ocean was formed from volcanic gases, the composition of which is approximately the following: 75% of water accounts for 15% carbon dioxide and about 10% of various chemical compounds. These compounds include methane, ammonia, sulfur, chlorine and bromine, as well as various gases. So when the products of the eruption fell to the ground in the form of acid rain, they reacted with the bottom of the future sea, and as a result we got a salty solution.
How much salt is there in the sea?
In one liter of sea water about 35 grams of salt.
How much water is there in the sea?
If we take average depth world ocean for 3703 meters, and the average surface area is taken equal to 361.3 million square kilometers, we get 1.338 billion km 3Which seas are the freshest and saltiest?
Let's start with another record holder - the largest sea. The absolute champion in this category is the Sargasso Sea, which is located inside the Atlantic Ocean. Its area reaches 8.5 million square kilometers.
But the freshest sea is in Russia, and this sea is the Baltic. Compared to the waters of the Atlantic, its sunshine is 5 times lower. Why? About 250 rivers flow into the Baltic Sea, which “desalinize” the waters.
What about the saltiest sea?
The record holder for the percentage of salts is the Red Sea. Its salinity is about 41 grams per liter of water! This phenomenal content explains the unique properties of the sea: it is very easy to float in it, and being in it itself is quite beneficial for health.
Why is the Red Sea so salty? The point is the fumes, which we wrote about at the very beginning. Water evaporates from this sea at a tremendous speed due to high temperature and low humidity, so that rains simply do not have time to “desalinate” it, and besides, very little of it falls.
Question - competition
Using the data above, calculate how much TOTAL salt is dissolved in ALL the seawater on our planet?
Send your answers in private messages to our communities at
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. Rivers constantly bring huge amounts of water along with small impurities 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
During times when the earth's crust was in a state of constant formation, there were frequent emissions of magma with incredible amounts of different 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 higher than its replenishment, which is facilitated by its location in the 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 whole 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, we can highlight 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 the active development of 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.
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 table 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, different sources of the appearance of salts in the World Ocean are considered.
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. When rainwater gets into the soil, it washes away small amounts 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 most saline lakes: Bolshoye 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.
Moreover, the characteristics of water in the oceans are not stable and are constantly changing. Another important point— in different parts of the same ocean, water can vary quite significantly in composition.
Where does salt come from in the oceans? The source of salts entering the ocean are the rivers flowing into it. Salt is washed out of rocks and soil by rivers and then enters the ocean. But the water in rivers should also be salty? This is true.
It’s just that if the salt content in water is below one ppm, it is considered fresh. Over many thousands of years, fresh water accumulated in the ocean, and when the water evaporated, the salt remained in it, so it reached such values that the salinity level reached several tens of ppm.
Climatic conditions have the greatest influence on the level and distribution of salinity, and this parameter is directly dependent on ocean currents.Surface ocean waters in areas where there is no direct influence from land can range from 32 to 37.9 ppm (3.2-3.79%).
In the ocean, the amount of water moving in and out of land, as well as precipitation, evaporation and condensation, have a direct impact on salinity levels. The balance of fresh and salt water in the ocean can be positive or negative.
The greatest decrease in salinity is observed near the equator, because this zone receives a significant amount of precipitation and evaporation is not very intense.
Towards the north and south of the equator, the salinity of water gradually increases.
Winds, precipitation, pressure - all these factors influence the level of salinity in the ocean. Warm ocean currents increase salinity, while cold ocean currents decrease it. On average, it is considered the saltiest Atlantic Ocean- 35.3 ppm. The Arctic Ocean is the freshest of all.
The most salty areas of the oceans:
- Atlantic Ocean, southern part - 37.9 ppm
- Atlantic Ocean, northern part - 37.6 ppm
- Indian Ocean - 36.4 ppm
- Pacific Ocean, northern part - 35.9 ppm
- Pacific Ocean, southern part - 36.9 ppm
Is fresh water found in the ocean? Level ocean waters was not always the same. Many thousands of years ago, the level of the world's seas was much lower than it is now. After the glaciers melted, it increased, but in the depths, under the ocean floor, quite large deposits of fresh water remained.
The world's oceans and fresh water are interconnected things. In which ocean can fresh water be found? There are quite a lot of such places, but extracting fresh water from ocean depths requires sophisticated equipment. Essentially similar to mining.
The only difference between ocean fresh water and ordinary water is that ocean water still contains a certain amount of salts (about 10 ppm).
Therefore, in conditions of a deteriorating environmental situation and a lack of fresh water, the ocean can become a source of valuable water reserves.
