Head Trimmer.

It's interesting that despite this article having a subtle inference to 'billions of years,' that you not only refer to this area as having been Eden, but point out that its age is in line with the Biblical account of a global catastrophe (flood) about 4400 years ago.

Big parts of Sahara are under sea level. I've always wondered what would happen if you'd put a sea there...
http://en.wikipedia.org/wiki/Qattara_Depression_Project

The Sahara is NOT the world's largest desert as stated in this article. It is the world's largest HOT desert, but only the third largest desert, the first two being the antarctic and the arctic.

If you took all the sand in North Africa and spread it out it would cover an area the size of the Sahara Desert.