Perhaps the cause of the “Great Flood”?
The theory goes that a medium sized ocean impact would put so much water in the air that it would rain for a long time, on top of waves hundreds of feet high. It would be cloudy for a very long time, too.
http://www.freerepublic.com/focus/f-news/1738251/posts
God warned Noah that this was coming and had him prepare for it, which is a good thing for us.