Why do oceans and seas have higher salt content than inland lakes, which are mostly “fresh water”?
Inland lake waters are deposited by rivers and then that water flows into other rivers which later flow into the ocean. The salt and other minerals comes from the lakes and rivers and is then deposited into the ocean. However, the amount of salt in rivers and lakes is very low and this takes a very long time. It is a theory that the oceans were once freshwater also and that the salt was built up over time. Inland seas and salt water lakes were once a part of the ocean and the reason that their salt content is so high (such as in the Great Salt Lake) is because there are no rivers flowing into it and the water is evaporating leaving the salt behind.
