Why do oceans have salt

The colour of the water also depends on other factors, such as what particles are floating in it. Coastal areas can sometimes look murky and brown as they contain sand from the seabed that has been churned up by waves. Living things influence the colour, too. Phytoplankton are tiny organisms that act a bit like plants, using chlorophyll to absorb sunlight and grow. They absorb red and blue light, reflecting green light and giving the sea a greener look.

Generally speaking, the more phytoplankton there are in the water, the greener it is. Have you ever wondered why the sea is blue, or whether dolphins sleep? The concentration of salt in seawater salinity varies with temperature, evaporation, and precipitation. Salinity is generally low at the equator and at the poles, and high at mid-latitudes. The average salinity is about 35 parts per thousand. Stated in another way, about 3. What is a hydrothermal vent?

NASA: Measuring salinity via satellite. 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. 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?