1st Step: In the area we know as the eastern Mediterranean Sea, salt was deposited between
5 and 6 million years ago, at the end of the Miocene geologic period. At that time the sea in this region was so shallow that it eventually dried up.
2nd Step: As the water evaporated, the salts that had been dissolved in the water were left behind. That was a huge amount of salt—each cubic meter of seawater contains about a kilogram (more than 2 pounds) of salt.
3rd Step: The salt deposits, called evaporites, hardened like rock. (Try our evaporite activity.) Then the area flooded with seawater from the Atlantic Ocean to the west. But again, over thousands of years, the sea shrank and dried up, depositing another layer of salt.
4th Step: This flooding and drying took place as many as 70 times before the final flooding, about 5 million years ago, which created the Mediterranean Sea. By then the evaporites were up to 10 kilometers (6.2 miles) thick! Over time, the evaporites became covered by oceanic sediments of clay, sand, and organic matter. Currently this “coat” of sediment is 100 to 200 meters (109 to 218 yards) thick.