I’m not an expert, but here are a few thoughts. The second chapter of Genesis notes that no rain had as yet fallen on the earth, but a “mist,” used to rise and water the entire surface of the land.
At the conclusion of the Flood, it’s noted in Genesis 8 that both the “fountains of the deep,” and the “floodgates of the sky,” were “closed.” Iow, rain didn’t account for all the water. There was a geological cataclysm that included the bursting open of the “fountains of the deep.”
Additionally, some have interpreted the earlier allusion to mist as meaning it didn’t rain at all until the flood. Rather, a heavy cloud cover created a year-round tropical environment.
These are just some hopefully useful thoughts. I’m not a Flood aficionado. Maybe someone who knows more about it can give more specifics.
I realize that the “fountains of the earth” had erupted. That must have set off chains of earthquakes all over the world.
I think FW that you are pretty correct in the flood idea. I believe the flood story to be true, as well as the Creation story. Although I think the Creation story is much more difficult to understand, as the story was told by people as revealed to them by God (whereas the flood was witnessed).
I’m also in agreement with webheart - one volcano (or a million) doesn’t do much to “prove” the flood story, or a young-earth creation.