Ocean why salty

When rain falls, it weathers rocks, releasing mineral salts that separate into ions. These ions are carried with runoff water and ultimately reach the ocean. Around 3. Some mineral ions are used by marine animals and plants, removing them from the water. 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. Many of the dissolved ions are used by organisms in the ocean and are removed from the water. Others are not removed, so their concentrations increase over time.

Another source of salts in the ocean is hydrothermal fluids, which come from vents in the seafloor. The heat causes a series of chemical reactions. The water tends to lose oxygen, magnesium, and sulfates, and pick up metals such as iron, zinc, and copper from surrounding rocks. The heated water is released through vents in the seafloor, carrying the metals with it. Some ocean salts come from underwater volcanic eruptions, which directly release minerals into the ocean.

Salt domes also contribute to the ocean's saltiness. Sodium and chloride also make up most salt in the ocean, but they're not the only minerals contributing to the sea's salinity. Morgan Raven , an organic geochemist and geobiologist and assistant professor of earth science at the University of California Santa Barbara, tells Mental Floss.

Most of the ocean's salt comes from rocks. The dissolved carbon dioxide in rainwater makes it slightly acidic, and when rain falls, it erodes rocks on land. Minerals from these rocks leach into rivers and streams, which then carry the salts into the ocean.

About 85 percent of the ocean's ions are sodium and chloride, while magnesium and sulfate make up around 10 percent. Not all salt that ends up in the ocean stays there. Salt is a life-sustaining substance , and a lot of the ocean's salt is consumed by animals.

But thanks to a steady supply of runoff from the surface, salinity levels are able to remain fairly constant. The ocean can count on one more source for its salt content: hydrothermal fluids.

Deep sea vents are heated by magma from beneath the Earth's crust, and they get hot enough to cause chemical reactions between seawater and minerals from the surrounding rocks.