# Why is the ocean salty?

Oceans cover about 70 percent of the Earth's surface and about 97 percent of all water on and in the Earth is saline—there's a lot of salty water on our planet. By some estimates, if the salt in the ocean could be removed and spread evenly over the Earth’s land surface it would form a layer more than 500 feet (166 meters) thick, about the height of a 40-story office building (NOAA). But, where did all this salt come from? Salt in the ocean comes from rocks on land. Here's how it works:

From precipitation to the land to the rivers to the sea....

The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid. The rain physically erodes the rock and the acids chemically break down the rocks and carries salts and minerals along in a dissolved state as ions. The ions in the runoff are carried to the streams and rivers and then to the ocean. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not used up and are left for long periods of time where their concentrations increase over time.

The two ions that are present most often in seawater are chloride and sodium. These two make up over 90% of all dissolved ions in seawater. The concentration of salt in seawater (its salinity) is about 35 parts per thousand; in other words, about 3.5% of the weight of seawater comes from the dissolved salts. In a cubic mile of seawater, the weight of the salt (as sodium chloride) would be about 120 million tons. A cubic mile of seawater can also contain up to 25 pounds of gold and up to 45 pounds of silver! But before you go out and try alchemy on seawater, just think about how big a cubic mile is: 1 cubic mile contains 1,101,117,147,000 gallons of water!

## Related Content

Filter Total Items: 5

### Where can I find bathymetric data?

The USGS has made bathymetric surveys for many coastal areas and for selected rivers and lakes in the U.S., including Yellowstone Lake, Crater Lake, and Lake Tahoe. Information and data for those studies is on the USGS Maps of America's Submerged Lands website. NOAA (National Oceanic and Atmospheric Administration) is the primary source of...

### What is marine geology?

Geology is the study of the Earth. This includes how the Earth was formed, how the Earth has changed since it was formed, the materials that make up the Earth, and the processes that act on it. Marine Geology focuses on areas affected by our oceans including the deep ocean floor, the shallower slopes and shelves that surround the continents, and...

### Where can I get current sea-surface temperature data?

The USGS has studied sea-surface temperature in many areas around the globe; you can find publications from these studies i n the USGS Publications Warehouse and by searching on the Internet. World maps and data are available from other agencies, particularly at the JPL OurOcean portal , at NOAA's Sea Surface Temperature website , and at the JPL...

### What is the difference between a tsunami and a tidal wave?

Although both are sea waves, a tsunami and a tidal wave are two different and unrelated phenomena. A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth. ("Tidal wave" was used in earlier times to describe what we now call a tsunami.) A tsunamis is an ocean wave triggered by large...

### How is the salinity of Great Salt Lake measured?

The salinity of Great Salt Lake is measured by taking specific gravity and temperature measurements and comparing them to standardized values reported in a table. Specific gravity is measured in the field by testing a water sample with a device very similar to a battery or antifreeze tester.
Filter Total Items: 2
Date published: June 4, 2015

### Celebrate June as National Oceans Month

June marks National Oceans Month, a month dedicated to spreading awareness of Earth’s oceans and coastal ecosystems.

Date published: May 22, 2014

### Study Aids Water Managers Battle Saltwater Intrusion

Scientists are using a cadre of new weapons in the battle against an old nemesis – saltwater intrusion.

Filter Total Items: 9
July 16, 2019

### All of Earth's Water in a single sphere!

This image shows blue spheres representing relative amounts of Earth's water in comparison to the size of the Earth. Are you surprised that these water spheres look so small? They are only small in relation to the size of the Earth. These images attempt to show three dimensions, so each sphere represents "volume." They show that in comparison to the volume of the globe,

...
March 22, 2019

### Why is the ocean salty?

A short video on why the ocean is salty.

March 23, 2017

### Salt, Sodium, Chlorine

Mineral: Halite (NaCl)
Primary mineral Commodity: Salt
Commodity Uses: Highway deicing accounted for about 44% of total salt consumed in 2016. Salt is also used as feedstock for chlorine and caustic soda manufacture; these two inorganic chemicals are used to make many consumer-related end-use products, such as

...
November 8, 2016

April 27, 2016

### beach.png

December 31, 2015

### Sunrise over the Atlantic Ocean

Sunrise over the Atlantic Ocean

October 1, 2015

### Large wave crashing on the reef at Laysan Island

A large wave crashes on the reef at Laysan Island, located in the Northwestern Hawaiian Islands.

January 1, 2002

### Mountain of Salt

This photo shows a road salt storage stockpile that is awaiting use for pavement deicing, Port of Milwaukee, WI. The use of salt to deice pavement can be harmful to aquatic life in urban streams. The USGS is involved in studies that focus on the influence of winter runoff on aquatic ecosystems.

August 15, 1973

### Why is the ocean salty?

Why is the ocean salty? Rivers discharge mineral-rich water to the oceans is from outflow from rivers, which drain the landscape, thus causing the oceans to be salty.

(July-September 1973) --- A vertical view of the Montevideo, Uruguay area of South America is seen in this Skylab 3 Earth Resources Experiments Package S190-B (five-inch Earth terrain camera)

...