What makes sea water salty?
One might wonder, why is the sea water salty. In reality, sea water is a very pure substance. Over ninety six percent of it is pure water. Almost three percent is common salt, and the remaining one percent is made up of small traces of lots of other elements.
All these elements are washed into the oceans by rivers and stay there. Water evaporates from the surface but the salt reminds dissolved. So the seas are gradually getting saltier. Some seas are much saltier than others, depending on how much water evaporates from them.
For instance, the Red sea, lying between Africa and Middle East, basks in hot sunshine all year round. It loses a lot of water through evaporation, which makes it six times saltier than the Baltic Sea high up in northern Europe. The Baltic sea does not get anything like as much sunshine. Therefore less water evaporates from it and the salt solution in the water is weaker.
