The salt of the ocean

Why is the ocean salty?

Maybe you’ve wondered.  Maybe you’ve heard folk tales about why the ocean is salty: magic salt mills, or perhaps tears.  Maybe you’ve just taken it for granted that it is, and always was and  will be.

Well, simply, the ocean is salty because science.


All water has minerals in it. Carbon dioxide in the atmosphere dissolves into water, and then helps to dissolve the minerals. When minerals dissolve, they form ions (chloride and sodium are most common in the ocean). The water is evaporated and recycled back into atmosphere (through the hydrological cycle), but the salt is left in the water.

Of course, some of the salt comes from the earth’s land. Salt is whisked off the earth’s surface by rivers and deposited in the ocean.

sea water
sea water

To put it less simply:

“Ocean water is indeed a complex solution of mineral salts and of decayed biologic matter that results from the teeming life in the seas. Most of the ocean’s salts were derived from gradual processes such the breaking up of the cooled igneous rocks of the Earth’s crust by weathering and erosion, the wearing down of mountains, and the dissolving action of rains and streams which transported their mineral washings to the sea.” Swenson, Why is the Ocean Salty? (US Geological Survey Publication)


Is the ocean getting saltier? No, not really. It manages to maintain its salty level at about 35 parts per thousand. What does that look like? If all the salt was removed from the ocean and spread out over the earth’s land evenly, it would be 500 feet deep (according to NOAA).

But back to it not getting saltier.  The rain keeps falling, the rivers keep depositing saline water, why isn’t the salt level increasing?

Perhaps that answer rests in the sea life itself. Organisms take some in, and new minerals are formed helping to take some in, and some reactions with the earth’s ocean crust absorb some of the saline back again.

So basically: the ocean is salty because the earth is salty. Rivers lick up the salt and deposit it in the ocean. Science helps break down the minerals naturally occurring in water to sodium ions in the ocean, and thus our ocean has salt in it.

salt on my skin,


PS where are the saltiest waters?





The Red Sea, and the Persian Gulf.

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