Salty seawater surprises many people
Anyone who has ever been to the sea and tried a sip of the water knows that it tastes salty. But not all waters taste salty. Most of the world's rivers and lakes are considered freshwater reservoirs. So why is there such a high concentration of salt in the water, especially in our oceans?
This is the reason for salty sea water
The reason for salty seas lies on land, more precisely in the minerals there. Salts occur naturally in the rocks of the earth. Groundwater sources loosen them from rocks and stones and bring them to the surface. In the form of small rivulets, the water runs at high altitudes over rock formations towards the valley and thus crosses other rocks, it can even sometimes disappear into layers of rock and earth and reappear somewhere else. On its way down, the spring water picks up all sorts of minerals, which are collected from mainly different rivulets into a small stream.
Water flows down the slope from the spring, washing out minerals
Formed as a stream, it flows further down and can be fed by other springs on its way to become a smaller river. It is not uncommon for these rivers to be fed by several tributaries on their way, or they themselves form side arms that meander through the landscape. Rivers often travel hundreds, sometimes even thousands of kilometers before they finally flow into the sea. Other rivers first cross small or large lakes and thus ensure that even more different minerals can be transported in their currents. Almost all rivers carry salt with them, but the residence time of the salt ions there is usually too short and their occurrence too small for these processes, which are referred to as fresh water, to taste salty.
Exception: Salty rivers
The Ebro River, for example, is an exception. Located in the north-east of Spain, this and other tributaries often have significantly more salt than the concentration of the Mediterranean Sea. It rises in Fontibre, a small mountain town in Spain. At a length of 910 kilometers it runs through the north of the country and does not flow into the Atlantic Ocean, which is closer, but takes its way to the Mediterranean Sea. Scientists assume that the salinity cannot be attributed exclusively to natural causes. Although the washed-out salt comes from rocks, these in turn largely come from mining. Agriculture is also doing its part to make rivers around the world saltier. Fertilizers, but also road salt, can be a cause of a permanent increase in the salt content in rivers. As a result, these waters flow into the seas with even more salt. The consequences of this for the environment are still uncertain.
Rivers flow into the sea and thus increase the salinity of the oceans
The end of many rivers is the sea. The materials introduced in this way, including salts in particular, have been accumulating in all the world's oceans for billions of years. Rivers constantly flow back into the seas and contribute to the continuous increase in salinity. Chlorine and sodium are the components of sea salt dissolved in water. Even before antiquity, people recognized that salt could be extracted from the sea and used to flavor dishes. The salt can also be used for curing and thus to support the shelf life of food. The extraction of salt is carried out in large salt pans. They can be located in mountainous regions and extract the salt from the rocks there, or near the seashore. The salt that is mined in mountainous regions mostly comes from sea deposits.
Inflows transport the salt water
Where oceans existed millions of years ago, there are now often mountains that house the salt deposits of ancient oceans in rock layers and can thus be made usable. Such a salt is called sodium chloride. This salt is better known in the kitchen as table salt. It's cheap these days, but salt used to be considered a real store of value and was even used as currency. By the way, not every sea is equally salty. For example, the North Sea has a higher salt concentration than the Baltic Sea. This is because, unlike the North Sea, the Baltic Sea is only fed with salt water through a small strait, whereas the North Sea has a large inflow of salt water from the Atlantic.