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Why is the sea salty?





cshs
Okay this is the question and I don't know the answer? The text books tell me that it's part of the precipitation cycle - rain fails - gets washed into the water and carries minerals? Is this so? Another explanation is the constant rising and falling of the water in the sea - through heating and cooling - which has no place to go and therefore builds up concentrations of minerals such as salt.

My hypothesis or guess - and please you are invited to throw stones at this!

First: there is a word issue - of the top of my head I don't know a "Sea" which is not salty (if you do I'd like to know- equally does anyone know a lake which is salty?) therefore all seas are salty anyway and doesn't matter about the processes.
Second: Bodies of water operate differently when they have varying amounts in, including the type and amount of life it can support- a puddle is different from a pond, lake, sea etc.
Third: I think it is this amount of life in the water that creates the salt by decay and then the heating and cooling effect as mentioned above.

I'm sure somebody out there has some thoughts on the subject - that's thoughts! - not simply replying using stock answers from text books!

SO come on....throw some stones!

PS. what is the difference between a sea and an ocean?
hummer010
cshs wrote:
equally does anyone know a lake which is salty?


The famous one would be The Great Salt Lake in Utah. There a many salty lakes.

Salinity is usually a result of no outflows in a lake. If there is no outflow (like the seas or oceans) then the only water loss is through evaporation. Suspended sediments and dissolved compounds do not evaporate, which increases their concentration.
Bikerman
The least salty (saline) sea I can think of, off hand, would be the Black Sea.
From memory I think it has a salinity of about half the 'normal' found in seas/oceans. It is largely meromictic (the water at different depths does not mix) so you get an upper level with low salinity and deeper levels with much higher salinity.
It was Halley (more famous for the comet) who first proposed the mechanism for salinity - the one in your text books. It is mostly correct - salts are carried by rivers flowing into the various seas.
In addition, however, sodium ions were 'leached' from the ocean-floor/sea-bed when the first oceans formed, and chloride ions come from hydrothermal vents and undersea volcanoes.

The difference between a sea and an ocean is tricky. Generally oceans are larger than seas. In addition, seas are partially or completely enclosed by landmass.
cshs
Thank you for responding hummer and bikerman. You see both of these exist - no outflow, process of concentration and minerals coming from the land - that's not to mention the sea floor activity which I forgot to mention in the first post. Why do none of these consider life within the seas? For example, what are we in salt? 1% of 60-70% of our body weight? (is that correct) That's quite a lot - what happens to that if we're left to fester in water and become part of the food cycle of that water?

As regards the salty lake of Utah - thanks for that I didn't know - I honestly don't know many lakes that are salty and to be fair it's a half cop-out by calling it the great salt lake! (do you know of any others? - I know that lakes can be larger than seas but still be called lakes presumably because they are fresh water - such as the biggy in Russia). As for the black sea I've swam in that and I know it's salty but you're never quite sure if it's salt or industrial waste!

Many thanks for your posts again!!!!
Bikerman
cshs wrote:
Thank you for responding hummer and bikerman. You see both of these exist - no outflow, process of concentration and minerals coming from the land - that's not to mention the sea floor activity which I forgot to mention in the first post. Why do none of these consider life within the seas? For example, what are we in salt? 1% of 60-70% of our body weight? (is that correct) That's quite a lot - what happens to that if we're left to fester in water and become part of the food cycle of that water?
You are not thinking it through properly. The same mistake is often made with people who propose that animals breathing are net contributors to CO2 emissions.

Just think carefully for a while and you will see the error in logic.

(Here's a hint in the form of two simple questions...
What materials comprise the organisms in the oceans/seas? Now, where do you think those materials come from?)
cshs
Thank you bikerman for your response. I've actually asked many scientists about this so please let's not be so hasty with our responses. I'm very pleased that you've responded - please could you explain the error in my logic and what your responses are? Honestly, I'm not trying to be patronising in my reply and I really do appreciate the fact that you are giving thought to some "received knowledge" on a subject about our world. All the best and awaiting you response?
Bikerman
OK, I'll spell it out.
Life in the sea is 'grown' from the chemical elements and compounds contained in the sea.
The salt in ocean/sea creatures comes, originally, from the ocean/sea. When those creatures die all that happens is that the salt is then returned to where it originally came from.

Get it?
cshs
absolutely - there was no claim otherwise. The differences are in concentrations. Where does our salt come from?

Cheers
Bikerman
cshs wrote:
absolutely - there was no claim otherwise. The differences are in concentrations. Where does our salt come from?

Cheers

I really don't get what you are saying. Our (human) salt comes from the sea and from mines which were once sea. That part of our salt content which is leached back to the sea when we die is simply completing a cycle. Life is not a net producer of any chemical - it all comes from the environment. Life can change one chemical compound into another, but with simple compounds like salt there tends to be a closed cycle...
Arthur3009
i don't uderstand, but anyway it's a intersting question because all of us don't know the answer, if youknow you should post here, will take a lot of doubts! help us o//
imera
Interesting post, learned something I didn't know, like salty lakes, I thought lakes was fresh water or muddy, maybe it depends on where they are located, the lakes up here in Norway are usually higher up than the sea, and they run down to the sea.
Jinx
The Great Salt Lake is actually what is left of a vast Pleistocene era inland sea. Over the centuries it has evaporated as the land around it became desert. The Bonneville Salt Flats are an alkali desert, and the salt deposits there are from the evaporation of the same inland sea.
There are several rivers that empty into the Great Salt Lake, but none that flow out, so all the minerals that are washed into the basin stay there.
SBCBC33
Great question! Never really thought about why some bodies of water have salt and others do not...
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