For the last two decades many earth scientists have supported the notion that the Mediterranean was once a huge, dry desert, lying 3,000 meters below sea level.
This "death valley" was thought to have existed at the end of Miocene time, about 6 to 5.5 million years ago….
From a geological point of view, the Mediterranean is a tectonically mobile land-enclosed depression small (about 3,000,000 square kilometers) in comparison to the major world oceansImmediately obvious on all charts is the highly variable topography and relief of both the seafloor and adjacent borderland. The coastline is highly irregular and continental shelves, though generally narrow, are well developed off the major river deltas (Nile, Rhone, Po, and
Ebro). Moreover, the deep-sea basins and trenches have distinctive relief, with basin plains ranging in depth from less than 1,000 meters to more than 4,000
Observation that rocks dredged offshore are similar to those on land raised a fundamental concept the key to understanding Mediterranean history lies in the adjacent emerged land masses, and vice-versa.
Early paleographic reconstructions showed that the once-open communication with the Atlantic deteriorated during the upper Miocene. Water-mass exchange continued for a while in the Rif Strait, but then ceased completely prior to the beginning of the Pliocene.
High relief near what is now the Strait of Gibraltar served as a barrier to the exchange of waters with the Atlantic. Exposed to a hot and dry climate, water evaporated and the then-dry basin elicited comparison with a gigantic Death ValleyMicrofossil studies suggested that the depth of the Mediterranean basin at these times had been "deep." Estimates suggested a dry seafloor as far as 2,000 meters below ocean level… As a response to suddenly lowered sea level, rivers feeding the Mediterranean and canyons on the now-dry seafloor began a geologically dramatic phase of erosion. Deep, Grand Canyon-like gorges of the Nile and
Rhone rivers, presently buried on land, were apparently cut during a great drawdown of water when the Mediterranean floor lay exposed 1,000 meters or more below its present levelThe sudden flooding through a gigantic waterfall at Gibraltar drowned the exposed basin floor. These falls would have been 1,000 times bigger than Niagara FallsThis flooding event is recorded by the Miocene Pliocene boundary, a time when open marine faunal assemblages were suddenly reintroduced from the Atlantic.
Geological theories usually fall at a glacial pace into a sea of controversy, and this one is no exception. Today charging that proof for the theory is lacking many scientists believe that the Med always contained saltwater, with only the depth of the seafloor and the water being in question Some of the tenets on which the theory was formulated are, if not defective, very seriously in question. To interpret their findings, a respectable number of geologists studying the surrounding emerged borderland as well as subsea sections indicate that alternative, more comprehensive concepts must be envisioned.
It is not realistic to envision the Mediterranean seafloor of about 5 million years ago as a desert at 3,000 meters below present ocean level. Several years ago the Mediterranean [was compared] to a complex picture-puzzle that comprises numerous intricate pieces, many of which are already in place. A general image is emerging, although gaps in some areas of the picture remain fuzzy and indistinct.
According to the author, which of the following is the most likely theory concerning the formation of the Mediterranean?
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