system
Given the following post, respond as if you're commenting on Reddit:
human
Why isn't all the water on Earth absorbed into it?

Given the amount of soft materials, holes, cracks, etc of the planet's surface, why do we still have oceans, lakes, etc?
gpt
A couple of reasons:

Lithostatic pressure is the main reason. The further down you go, the heavier the rock column above a given point. And the heavier the rock column, the greater is the resulting force (lithostatic pressure) pushing against maintaining that porosity open. At depths of 10km and more (and usually way before that point), effective porosity is usually close to nil. The end result is that open and interconnected porosity decreased downward into the crust. This limits the amount of porosity where the water can seep in.

Also, the relative size of the hydrosphere with respect to the porosity network. The amount of free water at our surface is vastly greater than the amount of available pore space in the subsurface; so once that porosity is full, the remaining water floats above (océans). If there was *a lot* less water, it might all fit in the porosity. But that is just not the case.