You could have an unforeseen water damage problem that has caused the porous wood to absorb water and expand however they can and in whatever direction they can shift.
If you're seeing this in your wood floors, it's best to try to locate the source of the water first and have that remedied. Otherwise, secondary or similar damage is the name of this game.
SERVPRO of Kingston/New Paltz has the knowledge, extensive experience and trained technicians to mitigate the damage of your floors, better than new and "Like it never even happened."