Why Is the Ocean Salty?

Words to Know

Minerals

The tiny building blocks inside rocks

Rain washes minerals out of rocks and into rivers.

Evaporate

When water turns into invisible gas and floats away

When ocean water evaporates, the salt stays behind.

Acidic

Something that can slowly dissolve other things

Rain is slightly acidic, so it can dissolve salt from rocks.

Salinity

How salty water is

The Dead Sea has very high salinity — it's saltier than the ocean!

Check What You Learned

Fun Facts

• The ocean is salty primarily because rainwater, which is slightly acidic (carbonic acid from dissolved CO2), erodes rocks on land, dissolving mineral salts which are carried by rivers into the ocean.

  Source: NOAA National Ocean Service

• Rivers carry about 4 billion tons of dissolved salts into the ocean each year.

  Source: USGS Water Science School

• When water evaporates from the ocean surface, the salt remains behind. Over billions of years, this has concentrated salt to about 3.5% of ocean water by weight.

  Source: NASA

• There is enough salt in the ocean to cover all land on Earth in a layer approximately 500 feet (150 meters) deep.

  Source: NOAA National Ocean Service

• The Dead Sea is one of the saltiest bodies of water on Earth, with a salt concentration of about 34%, compared to the ocean's 3.5%. Its extreme salinity makes floating effortless.

  Source: Geological Survey of Israel

• Most lakes are not salty because they have outlets (rivers flowing out) that carry dissolved salts away. The ocean has no outlet, so salt accumulates.

  Source: USGS