Why is the ocean salty?

https://oceanservice.noaa.gov/facts/whysalty.html

by tosh • 9 years ago

234 89 9 years ago

oceanservice.noaa.gov

bcaulfield• 9 years ago

Love any science article that provides a clear, scientifically accurate answer to any question my 6 year old asks me.

That's a lot of salt, though: "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 500 feet thick."

al2o3cr• 9 years ago

That sounds huge until you ponder that the water that salt is dissolved in is a layer many hundreds of feet thick covering 70% of the surface. :)

samstave• 9 years ago

What if you took all the water out of the oceans and layered it over the land? how thick would that water be?

combatentropy3• 9 years ago

I came here too just to remark how well-written it is.

Simple writing isn't easy. It doesn't just flow out. Garbage flows out. Well-chosen words in just the right order lie in the tenth rewrite, by the person who has studied writing for ten years.

everdev• 9 years ago

"We don't have a water problem, we have a salt problem." - Joe Rogan

b34r• 9 years ago

It’s completely breathtaking how massive our planet is in every measure that matters. And then we find out how big Jupiter is, VY Canis Majoris... The universe is a wonderful place!

outworlder• 9 years ago

At the same time, on average the universe contains nothing. It is so vast, that even if all stars were VY Canis Majoris, it would be still pretty much devoid of anything.

jameslevy• 9 years ago

Dark matter would like to have a word with you.

If there is one thing we have learned through the history of science, it's to be careful about statements like "X contains nothing".

usrusr• 9 years ago

And also at the same time, even the occasional mass concentrations in between are, in all likelihood, mostly rather bland and boring compared to earth, with its magnificent abundance of self-organizing and self-replicating patterns. Even the more interesting aspects of geology tend to be direct or indirect traces of life.

Or maybe not, and there actually is every imaginable wonder out there, including a planet where mattresses naturally occur, but my money would be on earth being pretty much as amazing as it gets.

Splines• 9 years ago

I've often wondered what living on a earth-like planet as large as Jupiter would be like. People on the other side of this "planet" would be aliens to you.

ekianjo• 9 years ago

Nice thought but earth like planets can never get that big because of gravity.

javajosh2• 9 years ago

I had to check if this was true. So, Jupiter is about 10x the diameter of Earth, which means it has 100x the surface area. So while it would still be possible to travel anywhere by jet, it would be impossible to travel everywhere in one human lifetime (e.g. there would be 100x the number of cities, nations, etc, and it's already unlikely that any human has visited every major city). So yeah, tentatively I think it's true.

telchar• 9 years ago

You may enjoy reading Ringworld - it involves life on the inside of a Dyson ring totalling 3*10^6 the surface area of Earth.

__s• 9 years ago

This made me wonder towards if the ocean is therefore becoming saltier & if so, at what pace? Found: https://www.seeker.com/are-the-oceans-getting-saltier-176509...

cryptonector• 9 years ago

The oceans are not saturated with salt, and there aren't many processes that extract salt from the ocean, but the process that made the oceans salty to begin with continues.

Also, the Earth is slowly losing its atmosphere, and with it -presumably- some water.

Of course, there's still a lot of water in rocks, so it's possible that the oceans could gain water and thus less salty.

But my guess is it's getting saltier.

nabla92• 9 years ago

O2 and H2O are both too heavy to escape earth.

Earth loses few kilograms of hydrogen and tens of grams helium per second to space.

ijidak• 9 years ago

Any idea about this line from the seeker article above?

"Salt ions themselves aren't added or removed from the ocean, but water molecules are freely gained or lost through the processes of evaporation and precipitation, or freezing and melting of ice," said Ruth Curry, a senior research specialist at the Woods Hole Oceanographic Institution.

"Salt ions aren't added". That doesn't seem right...

cperciva3• 9 years ago

Interesting historical fact: The salinity of the Earth's oceans was proposed as a clock for measuring the Earth's age by Halley in 1715. This method ultimately arrived at ages around 50 million years (it didn't account for salt losses due to tectonic activity) and was one of the major stepping stones towards establishing public confidence in the idea of an "old" Earth.

toephu2• 9 years ago

But Earth is about 4.54 billion years old [1].

[1] https://www.space.com/24854-how-old-is-earth.html

ccleve• 9 years ago

I wonder why lakes aren't salty?

It's clear why rivers and lakes that eventually empty into the ocean are fresh. Rainwater washes the salt downstream to its ultimate destination.

But many lakes do not have an outlet that leads to the sea. Water flows in and evaporates. Where does the salt go in that case?

Or is it possible that the article doesn't tell the full story, and that salty rocks are confined to a limited number of areas?

Retric• 9 years ago

Most lakes have an outlet. The US great lakes for example all share a river that's also the source of Niagara Falls.

On top of that, some lakes do get salty. Such as the 'salt lake' near Salt Lake City.

lobster_johnson• 9 years ago

...which is named the Great Salt Lake, by the way.

nordsieck• 9 years ago

Normally, water that has accrued in a drainage basin eventually flows out through rivers or streams on the Earth's surface or by underground diffusion through permeable rock, ultimately ending up in the oceans. However, in an endorheic basin, rain (or other precipitation) that falls within it does not flow out but may only leave the drainage system by evaporation and seepage. The bottom of such a basin is typically occupied by a salt lake or salt pan.

https://en.wikipedia.org/wiki/Endorheic_basin

It turns out that they are salty. They are often not as salty as the ocean though because oceans have been getting saltier for millions of years.

ajross2• 9 years ago

Time scale. Lakes are static bodies of water for a few thousand to a million years at a time before some flood or glacier or whatnot flushes them out to the ocean. The ocean stores the accumulated salts of 4.7 billion years of surface rocks.

javajosh2• 9 years ago

"Time scale" is actually a wonderful, pithy, accurate explanation for a lot of things!

coolso2• 9 years ago

The ocean stores the accumulated salts of 4.7 billion years of surface rocks.

I've always wondered. Were the rocks really there for 4.7 billion years, or did God create the rocks in such a way to trick scientists into believing they've been there for 4.7 billion years?

mythrwy• 9 years ago

Salt gets left when oceans get landlocked and die. (Thus the big layers of salt and salt mines). So it isn't really the accumulation of the age of the earth, it's a lot less because much gets redeposited.

But more generally yes, timescale.

cperciva3• 9 years ago

Some lakes are salty. The Dead Sea and the Caspian, for example.

But many lakes do not have an outlet that leads to the sea. Water flows in and evaporates. Where does the salt go in that case?

It sticks around. The terminal lakes which aren't salty are generally ones which only formed recently (e.g., after the most recent glaciation) or ones which are not fed by rivers (e.g., Oregon's Crater Lake).

ajross2• 9 years ago

FWIW, the Dead and Caspian seas are actually dismembered bits of ocean. They're salty because their water was originally salty. The only salty lake I can think of that didn't begin with ocean water is the Great Salt Lake, which is an evaporated basin from a much larger lake that just happened to sit on salty bedrock.

BurningFrog• 9 years ago

Most lakes actually do have an outlet to the sea.

Because they normally fill up whatever basin they're in and pour over some edge.

gumby• 9 years ago

The situation you describe is rare, so you don’t see it often. But the Dead Sea, and Great Salt Lake are examples of what you describe.

Plus, as another commenter says, it takes time and lakes are typically transient structures on a geological timescale.

cordite• 9 years ago

Supposing a terraforming species (like humans) never arose, will the ocean get saltier and saltier over the eons and eventually be inhospitable to all but the hardiest of microbes?

QAPereo• 9 years ago

Salinity levels will vary, but there is no trend to increasing salinity globally. Remember that water is still being “added” to the surface through volcanic activity, and the water cycle dominates, while the current rate of loss to space is quite low. I’m not sure whether volcanic activity is likely to slow before Sol starts to seriously cook off our water, but one of those would eventually lead to a reduction of surface water. That in turn, as with the Dead Sea, will lead to a higher concentration of dissolved solids in seawater.

The current (meaning billion+ years) homeostasis goes like this: https://science.nasa.gov/earth-science/oceanography/physical...

labster• 9 years ago

IANAG, but you're not accounting for processes that remove salt from the ocean. All of our salt mines come from somewhere -- crust that's been elevated to make an inland sea, that gradually evaporates and leaves a salt deposit. This can then get buried.

Possibly when the tectonic processes stop on Earth, the oceans will continue to get salty from weathering of rocks. And you won't have much addition of water from volcanism, only a little bit from space. But life gets generally hard without active tectonics anyway.

hansthehorse• 9 years ago

Posing this question to a young earth, christian, literal bible believer will generate interesting conversations.

PhasmaFelis• 9 years ago

I strongly suspect that it won't.

foota• 9 years ago

Is ocean salt equilibrium?

Steuard• 9 years ago

The US Geological Survey gives a slightly more nuanced answer (https://water.usgs.gov/edu/whyoceansalty.html), based (as I understand it) on comparatively recent progress in understanding this question.

It turns out that in addition to the "standard" explanation that the oceans' salt comes from rain dissolving rocks on land, another quite important contributing factor is the activity of hydrothermal vents on the ocean floor. As I understand it, the high temperature of the water emerging there helps it to carry very large amounts of dissolved minerals from deep in the crust back into the sea (and that our models of ocean salinity wouldn't work without this contribution).

qwerty456127• 9 years ago

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 500 feet thick, about the height of a 40-story office building.

Needless to say [almost] every land plant and creature on Earth would die in such an event. I just wonder (out of pure bizarre curiosity) what would happen if the salt in the ocean could be removed and put somewhere in the outer space - what part of the ocean life would survive and how much impact would it have on the land life.

sdrothrock• 9 years ago

how much impact would it have on the land life.

Sounds like oceans would be significantly lower, for one!

baddox• 9 years ago

I’d be curious to know how much energy would be required to separate all that salt from that water, especially in terms of the total solar energy Earth receives. If, hypothetically, all that solar energy were devoted to desalinization, how long would it take?

dzhiurgis2• 9 years ago

What I find fascinating is how in fact we are dependent on Natrium (https://www.youtube.com/watch?v=J3HivpHP-5I), presumably because our organisms originated from oceans to begin with.

Yet still, if dominating salt were Lithium or Potassium, we'd still probably happen to evolve, yet with slightly different cellular features.

Someone• 9 years ago

Interesting that you say Natrium (as opposed to Sodium), but Potassium, not Kalium. I thought use of the two variant names for those elements was 100% correlated. Are there regions of the world where that is not the case?

dzhiurgis2• 9 years ago

I just screwed up at being smartass :)

It is Kalium here too, but I did heard Potash before when referring to a mineral or fertiliser.

gus_massa• 9 years ago

Life is even more strange, because plants use very little sodium, so the relation is not straightforward ...

From https://en.wikipedia.org/wiki/Sodium_in_biology

In C4 plants, sodium is a micronutrient that aids in metabolism, specifically in regeneration of phosphoenolpyruvate (...) and synthesis of chlorophyll. In others, it substitutes for potassium in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata. [Note: most plants are C3] [...]
Since only some plants need sodium and those in small quantities, a completely plant-based diet will generally be very low in sodium. This requires some herbivores to obtain their sodium from salt licks and other mineral sources.

sundarurfriend• 9 years ago

I like that the article begins with a tl;dr summary of

Ocean salt primarily comes from rocks on land

Not many articles do that, but it only made reading the rest of the article more appealing to me, not less.

danaliv• 9 years ago

It’s been a while since I’ve read Slate but I recall their “Explainer” series always made a point of putting the answer in the first sentence, with the rest of the article serving as amplification. I really liked that, for the same reason you mentioned.

combatentropy3• 9 years ago

It's called the Inverted Pyramid structure, and it's how articles are supposed to be written. I learned it in junior high [https://en.wikipedia.org/wiki/Inverted_pyramid_(journalism)]. But yeah, it's not how many articles come today:

1. Clickbait headline that tells you nothing. (Unfortunately this article retains that flaw)

2. Introduction by the author of --- the author! He had been thinking about this topic for a long time. He had this conversation with his colleagues about it (reproduced here). Then his editor finally challenged him to have a go at it. So here it is!

3. Encyclopedic history of the topic (question still unanswered).

4. Compendium of assorted controversy and minority opinion (majority opinion still left to be stated).

5. The information.

6. Return to the author, his life, what he's doing afterwards, what he has eaten for breakfast, his favorite color, etc.

7. Request for comments, subscribe, like, share, etc.

ghaff• 9 years ago

it's how articles are supposed to be written

It's how traditional straight news articles have historically been written in large part for practical reasons. Those reasons were particularly evident for wire service copy where the newspaper using the copy could pretty much cut off the article at any arbitrary point to fit it into whatever hole they had in their layout.

For feature articles and many magazine articles, there's no hard and fast journalism rule to use inverted pyramid and never has been.

You may prefer that everything be written with inverted pyramid and that is certainly your right--and there are often good reasons--but it's not the "right" way to do things.

Sylos2• 9 years ago

Also helps that the remaining article isn't just filler-text to hide that one actually interesting fact under and instead consists of interesting facts in every sentence.

based2• 9 years ago

https://science.nasa.gov/earth-science/oceanography/physical...

https://en.wikipedia.org/wiki/Soil_Moisture_and_Ocean_Salini...

fauigerzigerk4• 9 years ago

What I'm wondering is why humans can't drink the water from the most ubuquitous reservoir on earth.

wickawic• 9 years ago

The vast majority of humans don’t live within walking distance of the ocean, it probably wasn’t a big evolutionary pressure to be able to drink seawater.

jacquesm3• 9 years ago

Actually, the vast majority of the humans live on the land within a very short distance of the oceans.

The thing is that we need a fairly careful balance between salt and fluid in our bodies, too much salt and our nervous system gets upset.

lists• 9 years ago

Because we come from the middle of Africa

fauigerzigerk4• 9 years ago

That was hundereds of thousands of years ago and we (well, many of us) have adapted to drinking milk (as adults) during that time.

So even though much of the planet is covered with sea water very few mammals have developed the ability to use sea water for hydration. I just find that surprising.

del_operator• 9 years ago

I'd be salty too if I had such a rocky interaction with the world.

Why is the ocean salty?

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