How does salt get into the ocean?

Answer 1

The short short answer is that salt dispersed in the rocks and dirt all over the Earth has been dissolved and washed to the sea. But, the long answer is better.

The question of the salt in the oceans of the Earth can be broken into two parts. First, where has all the salt come from and second, why is there so little salt in the oceans?

The oceans formed about 4 billions years ago, shortly after the Earth itself formed (4.5 billion years). It is estimated that between 4.4 and 3.8 billion years ago, the earth had cooled enough that water could condense and begin the formation of the oceans. Because the sun was not as bright back then, it is possible that much of the early accumulation of water was in frozen form that melted as the atmosphere changed and the sun warmed the earth again. There are no fixed estimate on how long it took the oceans to form or what the salinity was during the first billion years or so.

The ocean has a lot of salt in it now, 3.5% by weight, but that is not just dissolved sodium chloride (Na+, Cl-).

The ocean contains calcium, magnesium, sodium and potassium with bicarbonate sulfate, chlorine and bromine. (If you remove the water, then what is left is, by weight, Cl− 55%, Na+ 30.6%, SO4--, 4 7.7%, Mg2+ 3.7%, Ca++ 1.2%, K+ 1.1%, Other 0.7%.)

There are some differences in how the different ions of salt get into the ocean, but generally the primary way is through rain falling on the earth and dissolving salts and the rivers carrying the dissolved salts to the ocean. In the early history of the ocean there was surely a significant contribution to salinity from salts being dissolved from the material at the bottom of the ocean. In addition, the Earth gives off various gasses and volcanoes and hydrothermal vents in the ocean have added salts, especially chlorine that enters as hydrochloric acid.

We have by these mechanisms a reasonable understanding of how salt has entered the oceans and how it continues to enter the ocean.

The remaining question is why the oceans do not get more salty and have, in fact, remained at a more-or-less stable salinity for billions of years. Water evaporates from the ocean and returns as rain and leaves the salt behind, so if the salinity is constant, salts must be being removed from the oceans. There are different mechanisms that can be operative for different ions of sea salt, but the major removal processes are thought to be salt left after evaporation and salt buried through tectonic processes. The great salt deposits of the world are due to the evaporation of primordial inland seas or ocean deposits where a portion of ocean was isolated and evaporated. The tectonic processes are those where the ions are captured in the sedimentary layers of the ocean bead are buried at the points where tectonic plates move together and subduction carries material from the surface down into the Earth's mantle.

That is the long answer of how salt got into the ocean and how it is now going out at more or less the same rate that it is going in.

· 1. The most important part of the sodium and chlorine are dissolved from the earth salts and transported by rivers in seas/oceans.

2. A small part of chlorine is originated from the eruptions of submarine volcanoes.

Answer 2

Salt is dissolved from the earth and transported by rivers in seas/oceans.