A huge library of salt
ocean is home to the planet’s water resources, but let the water thirsty discouraged, because it contains a lot of salt and a wide variety, taste bitter and astringent and salty.
Scientists have estimated that the total weight of all salt in the ocean has reached 500 million billion tons. An essential product in human kitchens-sodium chloride (the main component of table salt), is the most important kind of salt in sea water. The average content of sodium chloride in seawater is about 3.5%, but don’t underestimate the 3.5% in this area. If all the sodium chloride in the world’s seawater is extracted and spread on land, it will be more than 120 meters thick. In addition to sodium chloride, the ocean also contains magnesium chloride, magnesium carbonate, potassium chloride, calcium chloride and various other metal element salts. Their average content is only one-third of that of sodium chloride. It will be 40 meters thick when spread on land.
Therefore, the ocean is a veritable “great salt reservoir”.
Sources of salt
, then, is where the ocean’s salt come from? In fact, the ocean didn’t have much salt in the beginning. The seawater of the primitive earth originated from ice comets, and the water quality is quite “pure”, and its taste should be as delicious as Nongfu Spring.
However, the water on the earth is always in motion and circulation. Every day, a large amount of sea water evaporates into the air in the ocean. This water vapor rises to the sky, dissolves the carbon dioxide in the atmosphere, and turns into slightly acid raindrops and falls to every corner of the land. “Acid rain” likes to erode rocks and wash the soil, bringing dissolved minerals and metal ions (including chloride ions and sodium ions) into the rivers, and the water from the rivers eventually enters the sea. In this way, the evaporated water circled around and returned to his ocean home again, but it brought a lot of salt on the land. According to the National Oceanic and Atmospheric Administration of the United States, rainwater will inject approximately 225 million tons of salt into the ocean every year, and 90% of the ocean’s salt content is contributed by the “rainwater cycle”.
”Rain water cycle” is not the only source of ocean salt. Submarine volcanoes and deep-sea hot springs are also silently making “paying”. The seabed is not completely sealed. At the cracks in the earth’s crust, there will be volcanoes and hydrothermal vents on the seafloor. Seawater seeps down along the cracks, heated by the magma heat source, and then flows upwards, forming hot springs that erupt. When fresh lava gushes from the volcano on the sea floor, the hot rock reacts with the salty sea water to dissolve some of the minerals in it; the hydrothermal vents directly inject the salty hydrothermal fluid into the seawater.
Over the course of billions of years, over time, as the salt accumulates more and more in the ocean, the sea water becomes more and more salty. Since the sea water already contains so much salt, and the salt will continue to enter the ocean. So, will the sea water “salt” indefinitely?
if the ocean is not reducing their salt, the results will certainly be the case. But scientists have discovered that the ocean has a variety of wonderful ways to reduce the salt content of the sea, so that the sea is in a dynamic balance.
First, chemistry will play an important role. On the one hand, as the rain water injects salt into the ocean, the concentration of soluble substances in the sea will become higher and higher. When the salt concentration reaches saturation, we can know from chemical knowledge that the supersaturated salt will precipitate, crystallize or combine with each other into insoluble compounds, and then sink to the seabed and become rock. On the other hand, seafloor lava will react with dissolved salt ions (such as magnesium ions) to remove them from the water. Certain clays and hydrogen-containing minerals (such as iron-manganese nodules) on the seafloor are thermochemically generated by seabed salts. The reaction formed.
Second, marine organisms also help to remove salt from seawater. They ingest or otherwise extract salt from the water, and these salts can be combined with organic organisms. For example, the substances on which shell animals produce shells come from the silicon and calcium salts in seawater; after a large amount of animals eat salt, these salts will be excreted in the form of stool and fall to the bottom of the sea and become part of the bottom sediments. .
Third, we still need to mention the water cycle-this is also the most direct way to “return salt to the ground”. Although rainwater sends salt into the ocean through rivers, when the typhoon season comes, strong winds and waves will also roll the sea water onto the land, and the dissolved salt will also come ashore with the sea water and spread over the coastal land. Especially after a long history of changes, some bay areas have been cut off from the ocean due to the rise of the earth’s crust and become inland. As a result, this part of the seawater is gradually evaporated, leaving behind a large amount of salt.
In addition, the fresh water in rivers and melting glaciers also provide stable fresh water to the ocean, which helps reduce salinity. Nowadays, with global warming, polar glaciers are melting, and more and more fresh water is injected into the ocean. Therefore, compared with seawater becoming salty, “is the seawater becoming desalinated?” has become a more concern for scientists.
A huge library of salt