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.
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.
> 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%.
> 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.
I don't think it's "hydrogen and oxygen ions"; that doesn't really meet the definition of water. I'd assume it's more like ebsom salts, where H2O is a part of the crystalline structure of the chemical compound. If you heat up epsom salts enough then the bonds are broken and steam is released.
When I see these infographics I think of non-technical audiences like policy makers and politicians consuming the same information, and I avoid making these fine distinctions. In this case, I would not mention the water in the mantle at all.
In a separate, private graphic, I’d show the available water next to the number of 1 GW reactors, the pile of annual uranium mining output to feed those reactors, and annual calendars it would take to assemble all that to extract the water and dispose of the waste in a way that won’t harm our ecosystem further to express, “if you want this water in a form you colloquially understand, the species possibly can’t afford it”. In case some wise ass decides to bring up that mantle water. But that additional detail would even help technically inclined audiences reading the infographic.
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.
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.
The article has a strong focus on "available to humans" and "that humans depend on". Many of the water beneath the crust is exactly that, pumping it up is an important source of drinking water. (In my country, the Netherlands, it's the primary, almost only, source of drinking water)
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.
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.
I long assumed that the Earth is a "water planet" because water is mostly what you see from a distance. It wasn't until I did the math that I realized that is really about wet rocks in space vs dry rocks in space.
Earth isn't made of water, it's just a damp rock. Or a bowling ball that you squirted a dozen times with a spray bottle.
The ballpark math is easy to do in your head too. The diameter of Earth is 8,000 miles, and the deepest point in the ocean, the Mariana Trench, is only 7 miles deep. It's immediately apparent that the oceans are tiny by comparison to the rest of the mass that is Earth.
I don't buy it. Even allowing counting iron as separate from what rocks can be composed of (and using mass instead of volume) you still have 30.1%+15.1%=45.2% of the Earth as oxygen and silicon (which are most certainly part of what makes a rock) at which point you've already disproved the claim Earth is more a ball of iron than a ball of rock.
A ball of iron covered with a ball of rocks is a more fair statement though, and I'd agree with that. It's just that center ball isn't most of what makes up the Earth (by any measure).
The volume of all water is 1,386,000,000 km^3, which is then 1.386e+21 liters, or right about the same number of kilograms.
The mass of Earth is about 5.972e+24 kg. So the percent fraction by mass is 0.0232%.
A "drop" is typically estimated at 1/20th of one mL, which is then 0.05 grams. We can estimate the mass of a small-ish bowling ball at 5kg, or 5000 grams. 0.05 / 5000 * 100 = 0.001%.
So it's an order of magnitude shy, but that's still closer than I expected! It's about 1 ml of beer on a bowling ball - a small splash. Or maybe a very large drop.
Oceanus's ocean tosses with slow, tall waves, beneath a pale blue sky. The colonists live in tall cities of steel and concrete with buildings sealed against the planet's harsh environment, on platforms floating on the planet-wide ocean. They spend their time pursuing art, leisure, and spiritual fulfilment, while automatic machines take care of their material needs.
> Earth isn't made of water, it's just a damp rock. Or a bowling ball that you squirted a dozen times with a spray bottle.
Yeah, the image with the oceans being dry is wow-inducing... On further thought, of course it'd be very close a sphere, because gravity forces it to be. A sphere where e.g. a slice of it is water (imagine a clementine with one of its segments being water) would be very wobbly if even possible at all..
Yup, the mere fact that we can have oceans and continents on a planet means we can only have so much water, lest we become a water world or something more like mars.
I do wonder if the OP includes water locked away in rocks though, to my understanding the majority of the water is in the mantle and not even the oceans, but my source is my butt for that one
I don't really follow a lot of comments questioning the choice of shape, methodology, exclusion of water in the mantle etc.
I believe the purpose of the image is to evoke sense of preciousness and responsibility towards the water we have - maybe how much for granted we take our "blue planet".
To me, this is an amazingly effective and visually poignant way of doing just that.
> This sphere includes all of the water in the oceans, ice caps, lakes, rivers, groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.
The USGS detail pages are based on 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).
Yep, it's quite misleading since the region where they looked for water at all is an incredibly thin layer on the outside of the planet, but they show it all as if it applied to all of the volume.
No, it doesn't. It includes all of the water in the oceans, ice caps, lakes, rivers, groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.
But would this sphere of water have enough mass to hold itself together as a sphere in space? Put aside it freezing into a ball of ice as a thought exercise.
Largest ocean in our solar system isn't even on Earth, apparently:
> ... Ganymede’s ocean is even bigger than Europa’s—and might be the largest in the entire solar system. “The Ganymede ocean is believed to contain more water than the Europan one,” he says. “Six times more water in Ganymede’s ocean than in Earth's ocean, and three times more than Europa.”
The largest ocean in the solar system actually is on Jupiter [1]. The gas planet has an absolute massive amount of liquid hydrogen on its "surface". But yeah, liquid hydrogen isn't water, so it might be the biggest ocean, but not the biggest ocean made out of water in our solar system :).
It would make Mars warmer. It would melt all the ice and CO2. It would give Mars an ocean. Of liquid rock. This is assuming that it doesn't destroy Mars completely. There might be enough fragments to make Solar System dangerous place and destroy life on Earth.
Europa is the size of our Moon. Colliding it with Mars would be similar to the collision that formed our Moon.
If you could squeeze the Earth's atmosphere into a ball of similar density it would be more or less of size of the middle sphere (all the oceans only weigh 270 times as much as the atmosphere [1]).
So there you have it: the key ingredients all life depends on are but a tiny boundary layer of water and air, stretched thinly between solid rock and the hostile emptiness of outer space.
The grand challenge of our sustainability is, indeed, how much can we (humans) perturb this extraordinary complex boundary layer without inducing runaway dynamics that we (or rather, future generations of us) will not particularly like.
Turn Randall Munroe loose on this idea and be prepared for unspeakable devastation as a tsunami of Lovecraftian proportions wreaks havoc on the planet...
Literally just posted today: the video version of his What If? analysis of what would happen if you took that ball of water and dropped it on Mars: https://www.youtube.com/watch?v=FkUNHhVbQ1Q
He already did it with a 1km diameter ball (https://what-if.xkcd.com/12/) and the destruction was terrifying. Please keep him away from these other bigger water balls.
Just a few quick calculations to make it more relatable...
They say the smallest sphere of freshwater lakes and rivers amounts to 93,113 cu km. There are 1 bil cu m per cu km. With a global population of 8.2 bil people, that comes to 11,355 cu m per person. That's a 22.5 meter wide/deep/tall cube (or about 7 or 8 stories tall building).
If we use the sphere that includes groundwater, 10,633,450 cu km. Then we end up with 1,296,762 cu m or a 109m wide cube per person.
> The largest sphere represents all of Earth's water. Its diameter is about 860 miles
Should be a radius of 430 miles, no?
The image is very non-intuitive, IMO, because it's making the water appear so small compared to the entire planet (which, duh, obviously the water is only part of earth), but also drawing the planet that small really hides how friggin big the earth is!
I thought the border with space is generally (and arbitrarily) said to be the Kármán Line, at 100 km / 62.1 mi. I'm not nitpicking, just curious about other definitions.
Also, I thought LEO typically begins around 180 km / 112 mi.
It's interesting to consider that there's about 26,000,000 km^3 of ice in the Antarctic ice sheet, which would give you a much larger ~150 m^3 cube of ice per person. That's not including the Greenland ice sheet or any sea ice.
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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-...>
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.
Specifically: given that the volume of a sphere is 4/3πR^3, doubling the volume is equivalent to increasing the radius by ~26%.
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...
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.
In a separate, private graphic, I’d show the available water next to the number of 1 GW reactors, the pile of annual uranium mining output to feed those reactors, and annual calendars it would take to assemble all that to extract the water and dispose of the waste in a way that won’t harm our ecosystem further to express, “if you want this water in a form you colloquially understand, the species possibly can’t afford it”. In case some wise ass decides to bring up that mantle water. But that additional detail would even help technically inclined audiences reading the infographic.
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.
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.
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.
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.
Radius of said sphere would only increase by ∛2. ;)
Earth isn't made of water, it's just a damp rock. Or a bowling ball that you squirted a dozen times with a spray bottle.
https://en.wikipedia.org/wiki/Origin_of_water_on_Earth#Aster...
The problem with that was, 1. there are better sources of water (the oort cloud) and 2. they aren't stuck in an gravity well.
It's a ball of iron covered with rocks (i.e. metal oxides) cover with water (i.e. hydrogen oxide).
A ball of iron covered with a ball of rocks is a more fair statement though, and I'd agree with that. It's just that center ball isn't most of what makes up the Earth (by any measure).
The volume of all water is 1,386,000,000 km^3, which is then 1.386e+21 liters, or right about the same number of kilograms.
The mass of Earth is about 5.972e+24 kg. So the percent fraction by mass is 0.0232%.
A "drop" is typically estimated at 1/20th of one mL, which is then 0.05 grams. We can estimate the mass of a small-ish bowling ball at 5kg, or 5000 grams. 0.05 / 5000 * 100 = 0.001%.
So it's an order of magnitude shy, but that's still closer than I expected! It's about 1 ml of beer on a bowling ball - a small splash. Or maybe a very large drop.
Understandably, since, in this case, surface area is more intuitively captured by our brains than volume.
Also because we are very small. The amount of water, from our perspective, makes it look like a water planet.
Yeah, the image with the oceans being dry is wow-inducing... On further thought, of course it'd be very close a sphere, because gravity forces it to be. A sphere where e.g. a slice of it is water (imagine a clementine with one of its segments being water) would be very wobbly if even possible at all..
I do wonder if the OP includes water locked away in rocks though, to my understanding the majority of the water is in the mantle and not even the oceans, but my source is my butt for that one
Dead Comment
lol it's funny when you put it that way
I believe the purpose of the image is to evoke sense of preciousness and responsibility towards the water we have - maybe how much for granted we take our "blue planet".
To me, this is an amazingly effective and visually poignant way of doing just that.
Does it include water in the mantle? (https://www.bnl.gov/newsroom/news.php?a=111648)
or other non-liquid water for that matter like hydrates (ebsom salts, etc)
The mantle-water research is fairly new, with this report from 2017:
"There’s as much water in Earth’s mantle as in all the oceans"
<https://www.newscientist.com/article/2133963-theres-as-much-...>
The USGS detail pages are based on 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).
<https://www.usgs.gov/special-topics/water-science-school/sci...> and <https://www.usgs.gov/special-topics/water-science-school/sci...>
https://lightsinthedark.com/wp-content/uploads/2013/06/ceres...
Dead Comment
> ... Ganymede’s ocean is even bigger than Europa’s—and might be the largest in the entire solar system. “The Ganymede ocean is believed to contain more water than the Europan one,” he says. “Six times more water in Ganymede’s ocean than in Earth's ocean, and three times more than Europa.”
https://www.scientificamerican.com/article/overlooked-ocean-...
Ganymede vs. Earth is indeed very surprising!
[1]: https://science.nasa.gov/jupiter/jupiter-facts/ (Under "Structure")
Europa Clipper launches in October [1]. I've seen talk of crashing it into Ganymede to give JUICE novel data [2].
[1] https://en.wikipedia.org/wiki/Europa_Clipper
[2] https://www.space.com/europa-clipper-might-crash-into-ganyme...
Europa is the size of our Moon. Colliding it with Mars would be similar to the collision that formed our Moon.
So there you have it: the key ingredients all life depends on are but a tiny boundary layer of water and air, stretched thinly between solid rock and the hostile emptiness of outer space.
The grand challenge of our sustainability is, indeed, how much can we (humans) perturb this extraordinary complex boundary layer without inducing runaway dynamics that we (or rather, future generations of us) will not particularly like.
[1] https://www.sciencefocus.com/science/how-much-does-earths-at...
Deleted Comment
They say the smallest sphere of freshwater lakes and rivers amounts to 93,113 cu km. There are 1 bil cu m per cu km. With a global population of 8.2 bil people, that comes to 11,355 cu m per person. That's a 22.5 meter wide/deep/tall cube (or about 7 or 8 stories tall building).
If we use the sphere that includes groundwater, 10,633,450 cu km. Then we end up with 1,296,762 cu m or a 109m wide cube per person.
Should be a radius of 430 miles, no?
The image is very non-intuitive, IMO, because it's making the water appear so small compared to the entire planet (which, duh, obviously the water is only part of earth), but also drawing the planet that small really hides how friggin big the earth is!
Also, I thought LEO typically begins around 180 km / 112 mi.
Deleted Comment