You may enjoy reading about the flood event that turned the Black Sea from fresh water lake (smack in the middle of emergent civilization) to a salt sea. https

You may enjoy reading about the flood event that turned the Black Sea from fresh water lake (smack in the middle of emergent civilization) to a salt sea. https://en.m.wikipedia.org/wiki/Black_Sea_deluge_hypothesis https://en.m.wikipedia.org/wiki/Black_Sea_deluge_hypothesis