When the Earth was at its warmest, and there were no ice caps at all, not even during the winter, and thermal expansion meant a certain amount of water took up more space, what ratio of Earth's surface was covered in water?

Also, how much more expansive was water back then? 5% or so?

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    $\begingroup$ keep in mind geologic effect can drastically change the amount of land covered without any change in sea level. There used to be a seaway through much of middle America that only drained do to tectonic uplift changing the actual height of the land. $\endgroup$
    – John
    Commented Oct 25, 2020 at 2:39

1 Answer 1


At that time there were large areas of shallow seas, so small differences in elevation could lead to large differences in water area. I doubt that the elevations are well enough known to estimate the area precisely.


The coefficient of expansion of water is only $207 \times 10^{-6}/K$. 15 degrees would give 0.3%.


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