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 each open body of water the chemical composition of the earth’s main 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, inhalations, 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. Its average temperature is 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, 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 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.
Water is one of the most powerful solvents. It is capable of dissolving and destroying any rock on the surface of the earth. Streams of water, streams and drops gradually destroy granite and stones, and leaching of easily soluble components occurs from them. No strong rock can withstand the destructive effects of water. This is a long process, but inevitable. Salts that are washed out of rocks give sea water a bitter-salty taste.
But why is the water in the sea salty and the water in rivers fresh?
There are two hypotheses about this.
Hypothesis one
All impurities dissolved in water are carried by streams and rivers into the seas and oceans. River water is also salty, but it contains 70 times less salts than sea water. Water from the oceans evaporates and returns to the earth in the form of precipitation, and dissolved salts remain in the seas and oceans. The process of “supplying” salts to the seas by rivers has been going on for more than 2 billion years - time sufficient to “salt” the entire World Ocean.
Clutha River Delta in New Zealand.
Here Clutha is divided into two parts: Matau and Koau,
each of which flows into the Pacific Ocean.
Sea water contains almost all the elements that exist in nature. It contains magnesium, calcium, sulfur, bromine, iodine, fluorine, and small amounts of copper, nickel, tin, uranium, cobalt, silver and gold. Chemists have found about 60 elements in sea water. But most of all sea water contains sodium chloride, or table salt, which is why it is salty.
This hypothesis is supported by the fact that lakes that have no drainage are also salty.
Thus, it turns out that initially the water in the oceans was less salty than it is now.
But this hypothesis does not explain the differences in the chemical composition of sea and river water: chlorides (salts of hydrochloric acid) predominate in the sea, and carbonates (salts of carbonic acid) predominate in rivers.
Hypothesis two
According to this hypothesis, the water in the ocean was initially salty, and it was not the rivers that were to blame, but the volcanoes. Proponents of the second hypothesis believe that during the formation of the earth's crust, when volcanic activity was very high, volcanic gases containing vapors of chlorine, bromine and fluorine rained down as acid rain. Thus, the first seas on Earth were... acidic. By entering into a chemical reaction with hard rocks (basalt, granite), the acidic water of the oceans extracted alkaline elements from the rocks - magnesium, potassium, calcium, sodium. Salts were formed that neutralized sea water - it became less acidic.
As volcanic activity decreased, the atmosphere was cleared of volcanic gases. The composition of ocean water stabilized approximately 500 million years ago - it became salty.
But where do carbonates disappear from river water when they enter the World Ocean? They are used by living organisms - to build shells, skeletons, etc. But they avoid chlorides, which predominate in sea water.
Currently, scientists have agreed that both of these hypotheses have a right to exist, and do not refute, but complement each other.
Often, sailors of ships that were wrecked or lost in sea waters died of thirst. But few people know why this is so, because there is a lot of water around.
The thing is that sea water is saturated with such a composition that it is not suitable for the human body and does not quench thirst. In addition, sea water has a specific taste, bitter and salty, and is not suitable for drinking. This is all due to the salts dissolved in it. Let's figure out how they got there.
What gives water its salty taste?
Salt has a crystalline appearance. Ocean waters contain almost all elements of the periodic table. Hydrogen and oxygen combine to form water molecules. It also contains impurities of fluorine, iodine, calcium, sulfur and bromine. The mineral base of sea water is dominated by chlorine and sodium (ordinary salt). This is why the water in the sea is salty. It remains to be seen how the salts get into this water.
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How sea water was formed
Scientists have been conducting experiments for a long time and trying to figure out why sea water is salty and river water is fresh. There are several theories about the formation of salty seawater.
It turns out that rivers and lakes also have salty water. But the salt content in them is so small that it is almost unnoticeable. According to the first theory, river waters entering the seas and oceans evaporate, but salts and minerals remain. Because of this, their concentration increases all the time and the water in the sea and ocean becomes salty.
According to scientists, the process of salinization of the seas has been going on for a billion years. But contrary to the first theory, it has been proven that the waters in the world's oceans have not changed their chemical composition for a long time. And those elements that come with river water only maintain the oceanic composition, but do not change it in any way. This leads to another theory. Salt has a crystalline consistency. Waves hitting the shore wash the stones. Lures form in them. When the water evaporates, salt crystals remain in these holes. When the rock breaks down, the salt gets back into the water and it becomes salty.
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The warmest seas in the world
Consequence of volcanic activity
Scientists have concluded that the water in the seas was salty back in the days when humanity did not exist on the planet. And the reason for this was volcanoes. The earth's crust was formed over many years by the emission of magma. And volcanic gases contain chemical combinations of chlorine, fluorine and bromine. They entered the ocean waters in the form of acid rain, and initially the water in the ocean was acidic. This water broke up the crystalline rocks of the earth's crust, and extracted magnesium, potassium and calcium. These acids began to form salts as a result of reaction with hard earth rocks. Few people know that the salt we are used to is formed as a result of the reaction of perchloric acid from the ocean and sodium ions from volcanic rocks.
Have you ever wondered what you would do if you were stranded on a desert island in the open ocean? You would first want to find food, make fire, make shelter and find water. Water? That's right, and although you may be surrounded by an endless ocean, those of you who have been to a sea beach know that sea water is not suitable for drinking.
Why not? Because . But why is sea water salty and not suitable for drinking?
Ocean water is salty because it contains large amounts of dissolved minerals. These minerals are often called "salts". Depending on where you are in the world, seawater contains approximately 3.5% salts. The water around it has a high salinity, while the northern waters contain less salts.
At the bottom there is a huge amount of minerals that are destroyed and rise to the surface by natural ocean currents. As the movement of water and waves erodes the ocean floor, minerals dissolve in the water and the amount of salts increases. This is how the ocean constantly replenishes its salinity.
Oceans and seas also get some of their salt from streams, rivers and lakes. While this may seem counterintuitive since these bodies of water contain fresh water, you may be surprised to learn that all lakes, rivers and streams contain some amount of dissolved salts. However, the concentration of salts in these bodies of water is much lower than in the oceans, so their water appears less salty than ocean water.
Salts cannot accumulate in most lakes because they have outlets such as rivers and streams. These outlets allow water to flow to the oceans, carrying minerals with the flow.
On the other hand, it is an example of a reservoir without an outlet. Minerals that flow into the Dead Sea cannot be released into the open ocean because there is no runoff. Because of this, the Dead Sea contains some of the saltiest water on Earth.
In fact, up to 35% of the salts are found in the waters of the Dead Sea! This is almost ten times more than the concentration of salt in the oceans. The salty water of the Dead Sea is lethal to most living things, which is why you won't find any fish or sea creatures there. Only a few species of bacteria and algae can survive the harsh conditions of the Dead Sea. That's why it's called Dead!
While you certainly wouldn't want to drink the water from this sea, you can swim in it. Due to the high concentration of salt, the density of water in the Dead Sea is much greater than in fresh water. This allows the swimmer to stay well on the surface of the water. Diving into the Dead Sea is a bit like dropping a plastic lid into a bowl of water. The dense water makes it easy to swim, even without much effort. In fact, water makes swimmers so buoyant that it is very difficult for them to reach the bottom or swim underwater.
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 a small amount 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.
