Is there enough water in the oceans, ice caps, rivers and streams to cover a completely flattened earth, in proportional to land volume and water volume?

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    $\begingroup$ I assume when you say "a completely flat Earth" you are talking about a sphere or better a geoid in which flat means perpendicular to gravity. $\endgroup$
    – arkaia
    Commented Apr 14, 2017 at 2:18
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    $\begingroup$ @aretxabaleta provides an answer below, but I think a key part of the question here is "to what depth," because presumably only a few microns would do. If you ask me if there's enough peanut butter to turn a loaf of bread into sandwiches, I need to know not only the size of the loaf and the amount of peanut butter in the jar, but how thickly you think the peanut butter should cover the bread. $\endgroup$ Commented Apr 14, 2017 at 16:49
  • $\begingroup$ What do you mean by in proportional to land volume and water volume? $\endgroup$
    – gerrit
    Commented Apr 18, 2017 at 13:55

1 Answer 1


Here is a very simplistic approximation: The total volume of the oceans (no lakes, rivers, water vapor) is around $1.3\ 10^9$ cubic kilometers. The surface area of Earth is around $5\ 10^8$ square kilometers. Dividing the volume by the area, we get a depth of 2.5 kilometers. The fresh water contribution is about 3% of the volume of salt water.

In reality, other factors such as the fact that Earth is not spherical, density changes, and that the water will be acted upon by tidal forces and other interactions, will make the distribution uneven.

  • $\begingroup$ A cup of water is enough to cover a "completely flat earth"....which is a relatively meaningless answer, but answers the question. Perhaps a better question would be, "To what depth would the world's water cover a completely flat earth?", which may be the question that aretxabelata is answering. $\endgroup$ Commented Apr 17, 2017 at 3:29
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    $\begingroup$ @KnobScratcher I'm not so sure about that, because at some point surface tension will take over. $\endgroup$
    – Spencer
    Commented May 6, 2018 at 23:52
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    $\begingroup$ @KnobScratcher no its not, because there are not enough molecules, even at the thickness of a single molecules you can't a cup of water spread over even a continent. $\endgroup$
    – John
    Commented May 8, 2018 at 2:52

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