Even children know that sea water is salty, but do you know why sea water is salty? Is the salinity of the sea water constant all the time? Where did the salt in the sea come from? We should start from the origin of the ocean.

Long, long ago, when the original sun was formed in the central part of the solar nebula, the residual material began to form the star cloud disk. It is said that the earth was formed from these residues. At the earliest stage of the formation of the earth, the temperature was very high, and the earth's core and mantle also began to form. This is the most active period of geological activities on the earth. Volcanic eruptions are very frequent. It is the gas of volcanic eruptions that formed the primitive atmosphere of the earth in the early stage.

In the earliest times, water was in the earth's primitive atmosphere, but it existed in the form of gas. As the earth's temperature began to drop, water vapor conditionally condensed into water, and finally turned into rainfall, which fell to the ground. The original concave and convex areas of the earth's surface became lakes, rivers, and oceans.

The rain in the sky is fresh water, so the primitive ocean is basically composed of fresh water. The salinity is very low, but the organic matter is very rich. Although many scientists now believe that life is generated from the hot spring mouth of the primitive ocean, the most primitive ocean is not suitable for biological survival. There are a large number of sulfides and sulfates in the ocean, which are harmful to organisms.

Where does the salt in the ocean come from? The salt in the sea comes from the land. When the water falls to the ground, the slight acidity of the water will damage the rocks and soil. The sodium ions and chloride ions in the rocks and soil are taken away by the water. These ions finally form the familiar salt and are washed into the ocean.

With the evaporation of ocean water, salt is constantly washed into the ocean, and the salt concentration in the ocean is greatly increased. At present, the concentration of salt in the sea is about 3.5%, which means that there is a very rich salt layer in the sea, which is why salt now comes from the sea.