Health Editor’s Note: Of course we know that the oceans are salty. It takes a small amount of sea water that gets into your mouth to know this fact. What I did not know is that the Great Lakes could be considered salty. While the Great Lakes have minerals they do not have sodium so they do not taste salty they are filled with minerals. The term “fresh water” must just mean no sodium but there are lots of other minerals involved. Also, an ion in water in the Great Lakes takes about 200 years before it is gone, but ions in the oceans are there for 100-200 million years. Whew! That is a long time!…..Carol
Why Is the Ocean Salty?
By Anne Marie Helmenstine, Ph.D./ThoughtCo
Have you ever wondered why the ocean is salty? Have you wondered why lakes might not be salty? Here’s a look at what makes the ocean salty and why other bodies of water have a different chemical composition.
- The oceans of the world have a fairly stable salinity of about 35 parts per thousand. The main salts include dissolved sodium chloride, magnesium sulfate, potassium nitrate, and sodium bicarbonate. In water, these are sodium, magnesium, and potassium cations, and chloride, sulfate, nitrate, and carbonate anions.
- The reason the sea is salty is because it is very old. Gases from volcanoes dissolved in the water, making it acidic. The acids dissolved minerals from lava, producing ions. More recently, ions from eroded rocks entered the ocean as rivers drained into the sea.
- While some lakes are very salty (high salinity), some do not taste salty because they contain low amounts of sodium and chloride (table salt) ions. Others are more dilute simply because the water drains toward the sea and is replaced by fresh rainwater or other precipitation.