eli5 if deserts used to be wet where did all the water go?

Question

and why is there still a little bit in oases

In: 8

Answer 1

There are things called aquifers, underground stores of water that can’t sink any lower, because the rock below them won’t allow water through so you get an underground puddle, where the land dips low enough compared to the surrounding area the top of the “puddle” can break through to the surface again. https://youtu.be/xbUfVLxYVcE