why is sea water salty ?
Salt can normally be found as chemical component of rocks and soil mostly in very low concentrations. But it dissolves by rainwater and the original idea about the salty sea was that the hydrological cycle carries salt and other minerals into the sea by rivers, after having been leached out of the ground by rainfall runoff.
Today we know that the processes are a bit more complicated. Other process like volcano eruptions produce salty components (chlorine acid gases) that directly influence the salt concentration in the oceans
Water evaporates at the ocean surface, without salt to become rain again. As the salt stays behind would seem that salt only goes one way. But the salt content of the sea has been rather constant for many million years, suggesting that there is also a salt cycle.
It is assumed that salt reacts chemically with rocks and that tectonic processes slowly move those rocks to landmasses again in the subduction zones, where it is again slowly leaching to the surface or it gets airborne again with volcanic eruptions.
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