5 ms·

NB: The infographic and articles are based on a 1993 publication. More recent research, from about 2017, suggests that there's about as much water in Earth's

NB: The infographic and articles are based on a 1993 publication. More recent research, from about 2017, suggests that there's about as much water in Earth's mantle as in all the oceans, so we either need another drop roughly the volume of the first, or the second drop should be greatly expanded. See: "There’s as much water in Earth’s mantle as in all the oceans" (2017) <https://www.newscientist.com/article/2133963-theres-as-much-water-in-earths-mantle-as-in-all-the-oceans/ https://www.newscientist.com/article/2133963-theres-as-much-...> The USGS is citing a 1993 publication, Igor Shiklomanov's chapter "World fresh water resources" in Peter H. Gleick (editor), Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford University Press, New York) (see the detail links from the submitted article). That said, water remains a precious resource, and fresh surface water all the more so. Edit: /double the size/s/size/volume/ above, for clarity.

utopcell 2y ago
> More recent research, from about 2017, suggests that there's about as much water in Earth's mantle as in all the oceans, so we either need another drop roughly the size of the first, or the second drop should be greatly expanded. Specifically: given that the volume of a sphere is 4/3πR^3, doubling the volume is equivalent to increasing the radius by ~26%.
- dredmorbius 2y ago
  Good call, I've swapped "size" for "volume" to be clearer.
hn_throwaway_99 2y ago
Does any of that water, though, ever make it onto the Earth's surface? I'm guessing not, or only miniscule amounts over geologic time through volcanism. For all intents and purposes, I think only counting "surface" water is more useful and intuitive. It's essentially any water that can participate in the hydrologic cycle on Earth, and that water locked beneath the crust doesn't really "matter" for what I think the intended purpose of this graphic is.
- dredmorbius 2y ago
  The fundamental problem with complex phenomena is in defining the domain(s) of interest. If we want to talk about the total amount of H2O around, on, or in the Earth then inclusion makes sense. If we want to talk about water interacting with the surface environment (atmospheric, sea, ice cap, fresh, and subsurface aquifers and tectonic water), then splitting those into distinct categories probably also makes sense. In which case we can also show the subsurface water. How much mantle water does make it to the surface over time is a good question. I've no idea though I'd suspect that some does through geothermal and tectonic activity. The more interesting question might be how we'd determine this (all but certainly through isotopic composition), and if a net flux could be determined. Over geological time, additional reservoirs of water are significant simply because surface water boils off into space over time, with estimates I've seen of up to 25% of Earth's original allotment having done so over 4.5 billion years or so. As the Sun eventually grows warmer, this rate will increase. At the same time, tectonic activity will slow. Note that there's a fair bit of water transport through the lower crust / upper mantle as oceanic plates subduct under continental plates, with the water absorbed into the oceanic plates playing a major role in volcanism at those plate boundaries, e.g., along the "Rim of Fire" surrounding the Pacific basin.
  - Symmetry 2y ago
    Earth is lucky to have a strong magnetic field and ozone layer limiting the loss of hydrogen to the solar wind. Mars, for example, has lost much more of its allotment.
- card_zero 2y ago
  We don't have access to any part of the planet below a depth of 2.5 miles, so the image should compare the volume of accessible water to the volume of accessible Earth, except then it would fail in its dishonest mission to make people say "gosh that sphere looks relatively small compared to the other sphere, I must restrict myself to ten-second showers." Even if it was accessible water to accessible non-water I don't really see how the metric is relevant in any decision making. Is it warning against a half-baked plan to mix water with every available cubic meter of soil or rock? Because there wouldn't be enough water to do that crazy thing? Thanks, I'll bear that in mind.
xattt 2y ago
> second drop should be greatly expanded Radius of said sphere would only increase by ∛2. ;)
kijin 2y ago
> or the second drop should be greatly expanded. The second drop is called "liquid fresh water". I'm not sure if I would want to categorize the water in the mantle as either "liquid" or "fresh". Most of that stuff is way above the critical point, not to mention saturated with rocky salts.
vixen99 2y ago
Seems that Jules Verne (1867) in 'Journey to the Center of the Earth' was onto something when he invented his subterranean ocean.
rdsubhas 2y ago
> The water discovered in the mantle is not in a form familiar to us – it is not liquid, ice, or vapor. Instead, it is trapped inside the molecular structure of the minerals in the mantle rock. IMHO this is not a productive comparison. Hydrogen and oxygen ions inside minerals in rock is far too much of a stretch of imagination to call as water. https://www.earth.com/news/ringwoodite-mineral-confirms-vast-ocean-exists-400-miles-under-earths-crust/ https://www.earth.com/news/ringwoodite-mineral-confirms-vast...
- WarOnPrivacy 2y ago
  > Hydrogen and oxygen ions inside minerals in rock is far too much of a stretch of imagination to call as water. Agreed and to follow that thread to the end: We can't impact that water in a meaningful way. We can't pollute it in dozens of ecosystem-altering ways. We can't alter it's ability to host systems that sustain life. We can't bulk-melt the frozen part & in turn alter the salinity + elevation of a liquid part. We can't pump dry the parts that we desperately need to remain where they are.
  - abduhl 2y ago
    Are you sure we can’t do any of these things, or are you just not thinking big enough? Give me a couple million dollars of VC money and I bet I could have an MVP that could conceivably accomplish at least one of these. I’d obviously need to raise another round of funds to find a market for such a product before taking the necessary steps to fit my product into that particular market (after raising more funds again, obviously). This hypothetical startup could be a net benefit to investors and shareholders by 2035, and a net detriment to all others by 2028. “Disruptive” is an understatement for what we could do for the environment and society.
    - WarOnPrivacy 2y ago
      If you had the means to reach the mantle economically, there are a lot of other uses you'd be put to first. Magma geothermal comes to mind.
- 2y ago

utopcell 2y ago

> More recent research, from about 2017, suggests that there's about as much water in Earth's mantle as in all the oceans, so we either need another drop roughly the size of the first, or the second drop should be greatly expanded. Specifically: given that the volume of a sphere is 4/3πR^3, doubling the volume is equivalent to increasing the radius by ~26%.

dredmorbius 2y ago
Good call, I've swapped "size" for "volume" to be clearer.

hn_throwaway_99 2y ago

Does any of that water, though, ever make it onto the Earth's surface? I'm guessing not, or only miniscule amounts over geologic time through volcanism. For all intents and purposes, I think only counting "surface" water is more useful and intuitive. It's essentially any water that can participate in the hydrologic cycle on Earth, and that water locked beneath the crust doesn't really "matter" for what I think the intended purpose of this graphic is.

dredmorbius 2y ago
The fundamental problem with complex phenomena is in defining the domain(s) of interest. If we want to talk about the total amount of H2O around, on, or in the Earth then inclusion makes sense. If we want to talk about water interacting with the surface environment (atmospheric, sea, ice cap, fresh, and subsurface aquifers and tectonic water), then splitting those into distinct categories probably also makes sense. In which case we can also show the subsurface water. How much mantle water does make it to the surface over time is a good question. I've no idea though I'd suspect that some does through geothermal and tectonic activity. The more interesting question might be how we'd determine this (all but certainly through isotopic composition), and if a net flux could be determined. Over geological time, additional reservoirs of water are significant simply because surface water boils off into space over time, with estimates I've seen of up to 25% of Earth's original allotment having done so over 4.5 billion years or so. As the Sun eventually grows warmer, this rate will increase. At the same time, tectonic activity will slow. Note that there's a fair bit of water transport through the lower crust / upper mantle as oceanic plates subduct under continental plates, with the water absorbed into the oceanic plates playing a major role in volcanism at those plate boundaries, e.g., along the "Rim of Fire" surrounding the Pacific basin.
- Symmetry 2y ago
  Earth is lucky to have a strong magnetic field and ozone layer limiting the loss of hydrogen to the solar wind. Mars, for example, has lost much more of its allotment.
card_zero 2y ago
We don't have access to any part of the planet below a depth of 2.5 miles, so the image should compare the volume of accessible water to the volume of accessible Earth, except then it would fail in its dishonest mission to make people say "gosh that sphere looks relatively small compared to the other sphere, I must restrict myself to ten-second showers." Even if it was accessible water to accessible non-water I don't really see how the metric is relevant in any decision making. Is it warning against a half-baked plan to mix water with every available cubic meter of soil or rock? Because there wouldn't be enough water to do that crazy thing? Thanks, I'll bear that in mind.

xattt 2y ago

> second drop should be greatly expanded Radius of said sphere would only increase by ∛2. ;)

kijin 2y ago

> or the second drop should be greatly expanded. The second drop is called "liquid fresh water". I'm not sure if I would want to categorize the water in the mantle as either "liquid" or "fresh". Most of that stuff is way above the critical point, not to mention saturated with rocky salts.

vixen99 2y ago

Seems that Jules Verne (1867) in 'Journey to the Center of the Earth' was onto something when he invented his subterranean ocean.

rdsubhas 2y ago

> The water discovered in the mantle is not in a form familiar to us – it is not liquid, ice, or vapor. Instead, it is trapped inside the molecular structure of the minerals in the mantle rock. IMHO this is not a productive comparison. Hydrogen and oxygen ions inside minerals in rock is far too much of a stretch of imagination to call as water. https://www.earth.com/news/ringwoodite-mineral-confirms-vast-ocean-exists-400-miles-under-earths-crust/ https://www.earth.com/news/ringwoodite-mineral-confirms-vast...

WarOnPrivacy 2y ago
> Hydrogen and oxygen ions inside minerals in rock is far too much of a stretch of imagination to call as water. Agreed and to follow that thread to the end: We can't impact that water in a meaningful way. We can't pollute it in dozens of ecosystem-altering ways. We can't alter it's ability to host systems that sustain life. We can't bulk-melt the frozen part & in turn alter the salinity + elevation of a liquid part. We can't pump dry the parts that we desperately need to remain where they are.
- abduhl 2y ago
  Are you sure we can’t do any of these things, or are you just not thinking big enough? Give me a couple million dollars of VC money and I bet I could have an MVP that could conceivably accomplish at least one of these. I’d obviously need to raise another round of funds to find a market for such a product before taking the necessary steps to fit my product into that particular market (after raising more funds again, obviously). This hypothetical startup could be a net benefit to investors and shareholders by 2035, and a net detriment to all others by 2028. “Disruptive” is an understatement for what we could do for the environment and society.
  - WarOnPrivacy 2y ago
    If you had the means to reach the mantle economically, there are a lot of other uses you'd be put to first. Magma geothermal comes to mind.
2y ago