Park Passes. Technical Announcements. Employees in the News. Emergency Management. Survey Manual. The oceans cover about 70 percent of the Earth's surface, and that about 97 percent of all water on and in the Earth is saline—there's a lot of salty water on our planet. Find out here how the water in the seas became salty. Why is the ocean salty? Rivers discharge mineral-rich water to the oceans. One way minerals and salts are deposited into the oceans is from outflow from rivers, which drain the landscape, thus causing the oceans to be salty.
You may know that the oceans cover about 70 percent of the of Earth's surface, and that 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 feet meters thick, about the height of a story office building Source: NOAA.
But, where did all this salt come from? If you get into folk stories and mythology you will see that almost every culture has a story explaining how the oceans became salty. The answer is really very simple. Salt in the ocean comes from rocks on land.
Here's how it works 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. This is natural. But these differences in salinity might get bigger in the future, because of climate change. Warmer climates may lead to more rain and melting ice in the northern hemisphere, and more evaporation in the southern hemisphere, which could change the saltiness of our seas.
The saltier that water is, the more dense or heavier it becomes. Along with warmer temperatures, this could affect how water moves around in the oceans, which could affect all life on our planet — not just the creatures living in the sea. This article has been updated to reflect the fact that sodium and chloride ions separate out when dissolved in water. You can:. Here are some more Curious Kids articles, written by academic experts:. Why does the light turn on?
Why do I have boogies and why does my nose keep replicating them? Can we live on Kepler b? The leftover minerals have built up in concentration over millions of years. Underwater volcanoes and hydrothermal vents on the seabed can also release salts into the ocean. Isolated bodies of water can become extra salty, or hypersaline, through evaporation. The Dead Sea is an example of this. Its high salt content increases the water's density, which is why people float in the Dead Sea more easily than in the ocean.
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