For centuries, the Mediterranean Sea has been the focal point of western civilization. It is an area rich in history and has played critical roles in the development of shipping and trade, as a resource for feeding growing populations, and as an aid to the spread and mingling of races and cultures.

The Mediterranean began to form about 250 million years ago when the Eurasian and African continental plates began moving toward each other, pinching off the Tethys Sea, an extensive shallow sea that separated Europe and much of Asia from Africa and India. It now has only two outlets, the Straits of Gibraltar and the Bosporus, a narrow strait between the Mediterranean and Black Seas. While the central basin of the Mediterranean reaches depths of several thousand yards, there is a sill under the Straits of Gibraltar that is only 1,970 feet (600 m) below the surface. Through...