I was sitting in history class yesterday, and my professor alluded to the fact that the many Great Flood stories of ancient civilizations could be attributed to a time when sea levels rose, causing the Atlantic to spill over the Straights of Gibraltar, filling up the Mediterranean. Could the fact that so many civilizations have stories of Great Floods be attributed to this event?
That sounds like The Zanclean Flood, but that was over 5 million years ago.
More frequently the Black Sea Flood is hypothesized as a possible historical source for Mediterranean flood myths, though that hypothesis has come under criticism from geologists who say that the Black Sea flood was much more gradual and less dramatic than the hypothesis supposes.
You might be interested in this: http://www.reddit.com/r/AskHistorians/wiki/faq/religion#wiki_flood_myths_around_the_world