I can see where the opening of heavens is a metaphor for rain but how in the world "all the fountains of the great deep were broken up" is a metaphor for rain is beyond me and further why the need for 2 metaphors in the same sentence is even more troublesome. No, the verse is describing separate things.
I'm sorry some wish to maintain ignorance in order to keep their view of a bible verse in accordance with their personal belief system rather than admit they are wrong.
OK fine. I will explain my thinking. I think that the phrase "the same day were all the fountains of the great deep broken up" means absolutely nothing more than "there was a big damn flood." Period. That's it. That's what I think the author meant by it. Nothing more. I think he was using extravagant language as authors are wont to do, and as authors who are trying to be dramatic and eloquent are especially wont to do.
Moreover, I think that not only would the author not have cared about the utterly ridiculous, downright imbecile modern exercise of trying to fabricate enough water to cause a global six-mile flood, but that the notion this could even be an issue would be absolutely incomprehensible to him.
However, if for the sake of argument one accepts that massive suboceanic geysers caused the floodwaters to burst from the ether underneath the oceans, then what I think is that this is no more cause for 96% of marine life to go extinct than a 40 day rainstorm would be. In short, no matter where you get the water - from the sky, from the ground, or from Mars - it's no more of an explanation for why 96% of marine life went extinct.
And finally, what annoys me most is that I even put myself into a ridiculous debate on Noah's Flood.