What do you think: Why is the water in the sea salty and fresh in the river? After all, everyone knows about the water cycle in nature. All the water that falls in the form of precipitation is fresh and it still then flows into the seas and oceans.
For a long time, it was believed that the seas salted rivers, which only seem insipid to human taste. In fact, they are also salty, only 70 times weaker than the ocean. Just on the way to the sea, river water washes out salts from the rocks along which its bed passes.
Once in the oceans, the rivers of the planet add one sixteen millionth share of salt to it every year. The water then evaporates, precipitating again on land in order to reintroduce a new pinch of salt into the ocean. This theory was fully confirmed by the salinity of the water in the closed lakes.
Thus, it turns out that initially the seas were as slightly saline as the rivers, and only over billions of years the water in them acquired a characteristic taste. But there is one big gap in this theory - the composition of salts in rivers and seas is fundamentally different: chlorides (salts of hydrochloric acid) prevail in the sea, and carbonates (salts of carbonic acid) in rivers.
However, today more and more scientists believe that the seas and oceans from the very beginning of their formation were as salty as they are now due to volcanic activity. It is assumed that the water of the primary ocean was a condensate of volcanic gases, which are 75% water, 15% carbon dioxide, and the remaining 10% are methane, ammonia, sulfur compounds, "acid fumes" containing chlorine, fluorine, bromine and inert gases. Most of the products of the eruption were poured onto the ground by acid rains and, reacting with the rocks of the future seabed, left behind a saline solution.
This theory is supported by the fact that the salt concentration in the open ocean water is always the same. The constancy of the salt composition is called Dietmar's law, after the English chemist who proved this important property of sea water in 1884. That is, no matter how much water evaporated from the ocean and returned there, the salt solution always remains unchanged.