Why is sea water salty, and not lake water?

Question

Why is sea water salty, and not lake water?

Answer 1

Many lakes are salty but few are as salty as the seas.  SOme reservoirs, planned for drinking and agricultural use have become too salty for the intended uses and become only recreational lakes(in shallow, slow moving lakes with salty water entering)

.But lakes are constantly draining and filling so the salt tends to move with the lake discharge and not concentrate.  In the oceans and seas there is no discharge (see below).  When the water evaporates it leaves its salt behind.  Since water is always going in and always being evaporated and with no other discharge the salt concentration goes up.

THe salinity in the ocean has 2 main limiting factors, which explain why the salinity is, overall, unchanging.  First, undersea vents take in huge amounts of sea water and somehow return the water to the ocean with most of the salt filtered out.  Second, if the salt content gets too high (in shallow, hot seas) the salt will be precipitated out of solution as new salt is added.

Answer 2

Most water in rivers has tiny amounts of salt in it, which it picks up as it flows across salty rocks. This flows into the lakes, but out again, so the lake does not get any saltier.

When the river gets to the sea, the salt is added to the sea. The water then evaporates and goes back into clouds, leaving the salt behind. So the oceans get saltier and saltier.

This is the standard explanation. But it's not the whole story, because eventually the oceans reach a stable point, and they don't get any saltier than that. The oceans have been a more-or-less constant level of saltiness for millions of years, and I don't know what the mechanism is that keeps them that way.

Answer 3

i heard its because of whale sperm... but im not to sure on the acuracy of that!!

Answer 4

lake water comes from mountains when the ice bergs melt. they're made up of fresh water. sea water is always on sand and stuff, which makes it salty i think.

Answer 5

Good morning Skycat,

It is thought that the salt in the seas and oceans stems from erosion of bedrock near ocean basins. Lake water comes largely from rainfall and melting snow. The water enters a a lake basin through streams, underground springs and ground water.

Since evaporated water can't "take the salt with it", even big lakes are generally made of freshwater, whereas the oceans are made of saltwater.

(I think that it much nicer to swim in lake water rather than sea water!)

Answer 6

Salt water is generally lower than most supplies of runoff, from mountains, upland lakes, rivers and so on. Salt water areas cover huge areas of the Earth's surface from which minerals, such as salt, spread into and throughout the water.  Upland water bodies are fed by rain (fresh water) and are therefore fresh. They are only salty if they are in contact with deposits of salt, thus some inland water reservoirs can be salty, like the Dead Sea and the Great Salt Lake.

Answer 7

lake water is not salty like sea water coz it came from accumulated rain water..

sea water is salty because it came from land, from rivers that carry salt minerals from land and after millenas of that process, salt minerals just accumulate in the sea

Answer 8

It is thought that the salt in the oceans stems from erosion of bedrock near ocean basins; big lakes and rivers are formed by evaporation and subsequent precipitation/runoff of ocean water, and by melting of freshwater ice. Since evaporated water can't "take the salt with it", even big lakes are generally made of freshwater, whereas the oceans are made of saltwater.

People don't really know what happens to the salt concentration (or salinity) of the oceans over time; Accurate salinity maps of oceans are hard to produce since oceans are so big. As the Earth's temperature rises in the future (both from natural and human effects) - two things will happen to the salinity. First, increased evaporation over oceans will tend to make the salinity rise. Second, increased melting at the poles will bring more freshwater into the oceans, which will decrease the salinity. Which of these two effects dominates the water cycle in the future will determine the change in salt concentration.