# How much of the Earth's surface was covered with water during the Mesozoic?

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?

• 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.
– John
Oct 25 '20 at 2:39

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