How Much Salt is in the Ocean?

June 8, 2021

Level of salt in the ocean as compared to the Washington Monument.

We all know that the ocean is salty, but have you ever wondered how much salt is in there?

About 97 percent of all the water on Earth is found in the ocean. According to NOAA’s National Geophysical Data Center, there is an estimated 321,003,271 cubic miles of water in the ocean. In one cubic mile of seawater, the weight of the salt in that seawater is estimated to be about 120 million tons since approximately 3.5 percent of the weight of seawater is salt. This means there are roughly 38.5 quadrillion tons of salt in the oceans.

The heaviest object ever physically weighed on Earth is NASA’s Revolving Service Station at Kennedy Space Center. It weighs 2,423 tons. It would take 15.9 trillion Revolving Service Stations to equal the weight of the salt in the oceans.

There is so much salt that if it were somehow removed from the ocean and spread across the entire surface of the Earth evenly, it would make a layer more than 500 feet thick. That is the equivalent of around the height of the Washington Monument in Washington DC or about the height of a forty-story building.

Why Are the Oceans Salty?

There’s a simple answer to why the oceans are salty. They’re salty because of rocks from the land. Rain that falls over land contains carbon dioxide making it slightly acidic due to the formation of carbonic acid.

The rain then erodes rock physically and chemically, and the dissolved minerals are broken down into ions. These ions eventually find their way to the oceans. Those ions not used by organisms remain in the ocean and increase in concentration. The two ions that are in the highest concentration in the ocean are sodium and chloride. They make up 90 percent of the ions in seawater. Sodium chloride is the compound that is formed, which is salt.

Two other processes occur that contribute to the salinity of the ocean — hydrothermal vents and underwater volcanoes. Minerals are dissolved from the crust and flow into the ocean when seawater reacts with hot rock.

Sources: NOAA (1), NOAA (2), Guinness Book of Records, USGS

About the author 

Daniel Ganninger - The writer, editor, and chief lackey of Knowledge Stew, the author of the Knowledge Stew line of trivia books, and editor of Fact World and the Knowledge Stew sister site on Medium, our ad-free subscription sites. I hope you learn many new things here that add to your knowledge.

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