The Flood
The oldest written copy of the Sumerian Flood Myth dates to 2150 BC, while the oldest written copy of the The Epic Of Gilgamesh dates to c. 2000 BC.
By way of comparison, Abraham is believed to have left Sumeria and entered Canaan c. 1850 BC, and Moses is believed, by both religious and some secular scholars, to have written Genesis (which includes the Hebrew version of the flood story) some time after 1300 BC, roughly 800 years after the oldest extant Sumerian versions.
This should remind us that both epics, like Gilgamesh, as well as religious compendiums, like the Bible, are compiled over a period of hundreds or even a thousand years, gaining and losing stories as they are shared.
Comparing Flood Stories: Sumerian-Babylonian and Hebrew:
Needless to say, once you've read both flood stories you will be struck by their similarities (see here for a direct comparison) and clearly both share a common source. Why?
The Source of Common Flood Mythology:
There are a couple different explanations for so many cultures, especially those in Europe and Asia, sharing similar flood stories.
1) Religious Explanation: it really happened, as described in Genesis.
2) Geographical Explanation: Even today, cultures build their cities on the banks
of rivers and in natural harbors, and floods are common, always, everywhere.
Within your own lifetime you have
witnessed a city vastly larger than any that existed in ancient times -- New
Orleans -- devastated by flooding, even though it was protected by billions of
dollars of modern technology (2005). More drastically, in your lifetime
millions of people have been wiped out by tsunamis, both in
Japan (2011)
and, more drastically, one that destroyed entire cities as distant as
Malaysia
and Africa (2004).
Mediterranean Tsunamis: At least two enormous volcanic events wiped out ancient Mediterranean cities via enormous tsunami. The first, c. 4000 BC, originating in Sicily, and the second, c 1600 BC, when the Greek island of Santorini exploded; scientist now believe this second wiped out Minoan culture, on Crete, and led to the rise of the Mycanean Greeks (Agamemnon, Achilles, Odysseus etc.). There's a great PBS Secrets Of The Dead documentary on this: Sinking Atlantis.
Santorini today:
Science and The Great Black Sea Flood:
Summary: Geologists/archeologists speculate that at the end of the last
ice age, c. 12,000 BC, melting glaciers created a great freshwater lake where
the Black Sea now stands:
We know that this "sea" consisted of fresh water because of fresh water mussel
fossils found there. Archeologists have also found evidence of human
habitation 300 feet below current levels.
Melting glaciers also caused sea and ocean levels to rise, and between 7,000-5,500 BC the Mediterranean breached the land mass at the Bosporus and flooded the fresh water lake, creating the Black Sea. Satellite Picture of The Bosporus (Istanbul):
Biblical scholars place the Great Flood/Noah at c. 6,000 years ago.
Many traditions hold that Noah landed on Mt. Ararat:
"The Search for Noah's Flood"
Robert Ballard's Search
"Undersea explorer finds new evidence of great flood"