The sea can make us contemplate the most beautiful summer scenes, with the sun’s rays illuminating its waves and the smell so characteristic of the coast. Although it also opens up innumerable questions about its constitution, it is so immense that the simple fact of observing it will be enough to open us to reflection. One of the most recurring questions is why the sea is salty and the answer is somewhat paradoxical.
a paradoxical explanation
The simplest explanation, and why we say that it is paradoxical, is that the seas obtain their salt thanks to the rivers. For millions of years, the rivers have been depositing different minerals from the erosion of the rocks. The cycle has repeated like a non-stop loop until the oceans turned salty. Although of course behind this simple explanation there is much more to say and to understand it, we must evoke the water cycle.
We could say that the water cycle refers to the presence and movement of vital liquid throughout the planet. In its different phases, water moves from one place to another and changes its physical state, giving rise to various phenomena. Among them, the salty water of the seas and oceans.
Halley and the question of why the sea is salty
the english scientist edmund halley, the same man who managed to describe mathematically the orbit of the comet that bears his name, was the first to manage to answer the question of why the sea is salty. According to his theory, which is now well accepted, rainwater becomes acidic because the mixture of carbon dioxide present in the atmosphere and water, form a substance known as carbonic acid.
When acid rain falls on the earth’s surface, it covers the rock formations, eroding them. In this way, the acid dissolves on the rocks and then becomes ions of different elements that will later end up being incorporated into the rivers. As the water cycle explains to us, rivers are freshwater but they are in constant motion and their ultimate destination is the seas.
This is how seawater gets its salinity. With the repetition of the water cycle and with rivers constantly flowing into the seas, it has caused oceanic waters to reach a medium salt concentration index. The average salinity concentration of the seas is 3.5%, that is, 35 grams of salt for each liter of water.
Where does sodium chloride come from?
Because rocks are not all made of the same minerals, it is to be expected that the salt concentration of the oceans also has diversity in its elements. The two main elements present in seawater are chlorine with 1.9% and sodium with 1%. Basic chemistry tells us that the combination of These two elements give us sodium chloride or what we commonly know as salt.
Although rivers are the main providers of salinity, melting ice, water evaporation and also volcanic eruptions contribute. Like everything on the planet, everything works meticulously to keep Earth running.
Not all seas have the same amount of salts, the concentration varies in different latitudes of the planet. For example, in tropical areas where temperatures rise more than elsewhere, evaporation is much higher. Consequently, the seas and oceans in these regions tend to have higher concentrations of salt compared to colder regions where the waters are less saline.
It might interest you