Why are lakes freshwater and oceans saltwater? (Smithsonian.com)
Why are lakes freshwater and oceans saltwater?
Lexile

Rain falls as fresh water. As this water flows downward, it ever so slightly erodes the rocks and soil. This causes a very slight amount of salt and minerals to dissolve in the water. Then they continue downstream. Eventually, all the dissolved minerals get dumped into the ocean.

Meanwhile, water on the ocean's surface evaporates. That means it goes into the air. It ditches all those salts and minerals. Then it falls back on land as fresh. In lakes and rivers, theres enough turnover that the water stays fresh. But in the oceans, the salts pretty much stay there.

Rivers dump about 4 billion tons of salts into the oceans each year. Even with all that new salt, the oceans are just so big. Their salinity stays fairly constant, at about 3.5%.


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COMMENTS (2)
  • Ashley0207-yyca
    6/23/2014 - 06:01 p.m.

    Wow really!? Maybe it is weird but I never knew that was possible. I felt very weird because rivers dump about 4,000 billion salt water!

  • Brandon1231-YYCA
    7/16/2014 - 01:25 p.m.

    REBUTTLE
    I think hat you are wrong a again. Actually, the evaporation of the ocean makes rivers and pond for salty because they don't move as much as a ocean. For correction it is 4,000 tons of salt not salt water. So you got that wrong about your fact. And I don't think that you know that evaporation is because just by reading your comment, you are wrong about the fact.

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