Hi there, I have a geophysical question. I'm trying to understand what the dehydration embrittlement is and I've found a definition: "Dehydration of partly or completely serpentinized ultramafic rocks can increase the pore fluid pressure and induce brittle failure, a process referred to as dehydration embrittlement."

I don't understand why dehydration of a rock increases the pore fluid pressure... why less fluid causes more fluid pressure?
Anybody can explain that? Thank you!