Why are the oceans and seas always salty. Why is the sea salty and some lakes even saltier

Why is ocean water salty and fresh water in rivers? The answer to this question is ambiguous. There are different points of view that reveal the essence of the problem. According to scientists, it all comes down to the ability of water to break down rock and leach easily soluble components out of it, which end up in the ocean. This process is ongoing. Salts saturate sea water, giving it a bitter-salty taste.

Everything seems to be clear, but at the same time, there are two diametrically opposed opinions on this issue. The first boils down to the fact that all the salts dissolved in water are carried by rivers into the ocean, saturating sea water. There are 70 times less salts in river water, therefore it is impossible to determine their presence in it without special analyzes. We think that river water is fresh. In fact, this is not entirely true. Saturation of sea water with salts occurs constantly. This is facilitated by the evaporation process, as a result of which the amount of salts is constantly increasing. This process is endless, and lasts about two billion years. There is enough time to make the water salty.

The composition of sea water is quite complex. It contains almost the entire periodic table. But most of all, it contains sodium chloride, which makes it salty. By the way, in closed lakes the water is also salty, which confirms the correctness of this hypothesis.

Everything seems to be correct, but there is one but! Sea water contains salts of hydrochloric acid, and in the river - coal. That is why scientists put forward an alternative hypothesis. They believe that sea water was originally salty, and rivers have nothing to do with it. This is due to volcanic activity, the peak of which occurred at the time of the formation of the earth's crust. Volcanoes ejected into the atmosphere great amount steam saturated with acids, which condensed and fell to the ground in the form of acid rain. Sediments saturated seawater with acid, which reacted with solid basaltic rocks. As a result, a huge amount of alkali was released, including sodium, potassium and calcium. The salt thus obtained neutralized the acid in the sea water.

Over time, volcanic activity decreased, the atmosphere was cleared of vapors, and less and less acid rain fell. About 500 million years ago, the composition of sea water stabilized and became what we know it today. But the carbonates that enter the ocean with river water serve as an ideal building material for marine organisms. They build coral islands, shells, their skeletons out of it.

Which hypothesis to prefer is a purely personal matter. In our opinion, they both have a right to exist.

Have you ever thought about what you would do if you were on a deserted island in the open ocean? You would first like 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 the sea beach know that sea water is not suitable for drinking.

Why not? Because . But why is sea water salty and not drinkable?

Ocean water is salty because it contains a large number of dissolved minerals. These minerals are often referred to as "salts". Depending on where you are in the world, sea water contains approximately 3.5% salts. The water near 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 the natural currents of the ocean. As the movement of water and waves breaks the ocean floor, minerals dissolve into the water and salts increase. So the ocean constantly replenishes its salinity.

The 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 less than in the oceans, so their water seems to be 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 it.

On the other hand, it is an example of a body of water without an outlet. Minerals that drain into the Dead Sea cannot be released into the open ocean because there is no runoff. As a result, the Dead Sea contains some of the saltiest waters 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 deadly to most living creatures, so you won't find fish or sea creatures there. Only a few types of bacteria and algae can survive in the harsh conditions of the Dead Sea. That's why it's called Dead!

Although you certainly don't want to drink 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 keep 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, the water makes swimmers so buoyant that it is very difficult for them to reach the bottom or swim underwater.

Ocean! This word sounds loud and menacing. This is a one-of-a-kind huge accumulation of water that surrounds the continents and islands. It is the boundless sea that surrounds the universe. But, I wonder what kind of water is in the ocean, what is its chemical composition?

The chemical composition of ocean water

Ordinary residents often deal with fresh water, in which there are almost no impurities. However, it also contains dissolved salts, although in small concentrations. What about the ocean then? What is the water in the ocean? Judging by the composition, the ocean can hardly be called water. It is very similar to strong salty brine. Each kilogram contains about 35 grams of various salts. Scientists have found that dissolved in the ocean chemical compounds all elements.

Salt in the ocean

The fact that the ocean has salt water is an undeniable fact. But in different parts oceans, the concentration of salt is different. The most salty of all oceans is the Atlantic, although some scientists consider the Indian Ocean to be the most salty. And the least salty is the water of the Gulf of Finland. Despite the fact that the salinity in different parts of the oceans is different, the ratio of different salts in the water is the same. Such amazing constancy is explained by the mixing of water by waves and currents.

Is there a fresh water ocean

Fresh water in the ocean? It's impossible! Although there are hypotheses in science, but this is just an assumption. This freshening is explained by the influence of powerful rivers flowing into the ocean and abundant precipitation in temperate latitudes. However, the rivers that tend to the ocean do not have clean fresh water in their composition. Rivers wash away rocks and, washing away salts, carry them to the ocean. And let's not forget the water cycle. After evaporation, ocean water falls as rain or snow, collects in rivers, and returns to the ocean. Thus, salinization of the ocean continues to this day.

Water is one of the strongest solvents. It is able to dissolve and destroy any rock on the surface of the earth. Water flows, streams and drops gradually destroy granite and stones, while leaching of easily soluble minerals from them occurs. constituent parts. No strong rock can withstand the destructive effects of water. This is a long but inevitable process. The salts that are washed out of the rocks give the sea water a bitter-salty taste.

But why is the water in the sea salty, and fresh in the rivers?

There are two hypotheses for this.

Hypothesis one

All impurities dissolved in water are carried by streams and rivers to the seas and oceans. River water is also salty, only salts in it are 70 times less than in sea water. Water from the oceans evaporates and returns to the earth in the form of precipitation, while dissolved salts remain in the seas and oceans. The process of "delivery" of salts to the seas by rivers has been going on for more than 2 billion years - a time sufficient to "salt" the entire World Ocean.

Sea water contains almost all the elements that exist in nature. It contains magnesium, calcium, sulfur, bromine, iodine, fluorine, copper, nickel, tin, uranium, cobalt, silver and gold are contained in small amounts. 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 do not have a runoff 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 originally salty, and the reason for this was not rivers at all, but 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 chlorine, bromine and fluorine vapors poured acid rain. Thus, the first seas on Earth were... acidic. Entering into chemical reaction with solid rocks (basalt, granite), the acidic water of the oceans extracted alkaline elements from 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 about 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 chlorides, which prevail in sea water, they avoid.

At present, scientists have agreed that both of these hypotheses have the right to exist, and do not refute, but complement each other.

The phenomena of the world around us raise a lot of questions among the curious. For example, when you find yourself on the shore of an endless reservoir, you begin to wonder: what kind of water in the ocean is fresh or salty? How can you explain the chemical composition of ocean water and is it drinkable?

The composition of water in the seas and oceans has been surprising people since ancient times. In Germany, there are legends that claim that there is a magical salt mill at the bottom of every sea, and in Hungary - that this is all because of the tears of an unfortunate girl grieving under the water column.

Finding out if the water in the ocean is salty is actually as easy as shelling pears - just refer to the materials contemporary research. Indeed, sea and ocean water is very salty, and sometimes the concentration of salts is excessively high: one glass of a “drink” from the Dead Sea is enough to not regain consciousness at all.

The most saline expanses of water in the world are:

• Atlantic Ocean: southern part (salt concentration is 37.9 ppm) and northern part (37.6);
• Pacific Ocean: southern (36.9) and northern (35.9);
• The entire Indian Ocean (36.4 ppm).

Why is ocean water salty

Oddly enough, but to such a simple question - why is the water in the ocean salty - even modern scientists have not found a definite answer. Some researchers believe that this is due to volcanic activity, while others believe that salt enters the oceans through rivers and seas.

About the amount of salt and fresh water on earth.

Two theories

The first group of scientists claims that a very long time ago, when Earth's crust only formed, volcanoes on Earth were extremely active. Their eruptions led to the occurrence of acid rain - but the oceans themselves consisted of acids. As a result, various complex substances“collided” with each other, and as a result of the reaction, the ocean waters became safe for life, which had yet to be born. But very salty.

As for the "earthen" theory, it says that salts are contained in all water bodies of the world. And this is true - fresh water is not devoid of salts, there are just very few of them. Flowing into the oceans, rivers and seas bring with them salt washed out of the soil. They, in turn, remain in place - and where else can they go? Yes, during the natural cycle, water also evaporates from the surface of the oceans, but salts are too heavy to go after it.

As you can see for yourself, these theories are quite logical. Or maybe both groups of researchers are right at once, and at first salts arose thanks to volcanoes, and numerous currents brought them even more?

Can a fresh ocean arise

What determines the salinity of ocean water? Many factors play a role here, including underwater currents, the presence of glaciers, the intensity of their melting, the activity of evaporation, etc. In addition, in the depths, under the very bottom of the ocean, there are deposits of the purest fresh water.

But even if we imagine that a crystal clear body of water will appear on Earth, it is obvious that fresh water in the ocean would not linger for a long time. After all, no one doubts that rivers constantly add salt washed out of the soil to ocean waters - scientists are skeptical only that this could cause the appearance of vast salt reservoirs as such.

Can you drink sea water

So, we figured out why the water in the seas and oceans is salty, and found out that drinking it is not recommended. But why is there such a limitation?

In fact, ocean water is contraindicated for humans due to the structural features of the body. The kidneys are responsible for removing salts and other “heavy” substances from food, which may simply not be able to cope with the excess load. A liter of sea water contains more than 30 grams of salt! That is why the unfortunate, shipwrecked and managed to escape in boats, often die of thirst in the middle of the water.

Why is the sea salty: Video