Hydrosphere Contents

4. Oceans

Water in the oceans has a very constant composition

As part of the hydrological cycle rivers flow into the sea and then the water is returned to the land via evaporation into the atmosphere. Although we call the rivers freshwater, they are actually very dilute solution of salts which come about principally by the weathering of rocks. The water evaporating from the sea is almost pure water containing none of these salts. Thus the salts build up in the oceans. However, although water comes into the ocean containing dissolved salts and leaves it as pure water, the oceans are not getting saltier and saltier.

Which two ions have the greatest concentration in sea water?