How Much Salt Is in the Ocean?

If you consider that about 70 percent of the Earth’s surface is covered with water, and 97 percent of that water is saline, you quickly realize that our planet has a lot of salt water. Where does all that salt come from? Over time, dissolved carbon dioxide from rain, in the form of carbonic acid, erodes rock and ultimately carries salts and minerals into the sea. The National Oceanic and Atmospheric Administration estimates that if all of the salt from the oceans could be spread evenly across the Earth's surface, it would form a 500-foot (166-m) layer. That’s the height of a 40-story office building.

Keeping an "ion" the ocean:

  • Chloride and sodium make up more than 90 percent of all dissolved ions in the ocean. Some are used by organisms, but most just build up over time, increasing the overall saline concentration.
  • In a cubic mile of seawater, the weight of the salt comes to about 120 million tons.
  • To a lesser extent, salt also finds its way into oceans from hydrothermal vents and from the eruption of underwater volcanoes.
More Info: US Geological Survey

Discussion Comments


Why not also tell us the percentage of the concentration of salt vs the human fluids? The info given requires too much math to convert the cubic mile of water volume to weight to figure percent. Good job, though.


This brings another question to mind. Is ocean salinity consistent throughout the depths? As the ocean gets deeper, the pressure increases. It would seem at great pressure, the minerals would be squeezed out of the water. What does the extreme cold at depth do to this proposition?

Post your comments
Forgot password?