Geology Reference
In-Depth Information
strong bottom current, which then dragged their boats against the surface current. Hugging
the seafloor, a submerged river of salt water flowed into the Black Sea.
In 1993, oceanographers Bill Ryan and Walter Pitman led a joint Russian-American ex-
pedition to survey and sample the floor of the strategically important Black Sea. Scanning
the seabed with sonar, their team found evidence of ancient streambeds, river-cut canyons,
and submerged shorelines. In samples of the bottom sediments saltwater mussels replaced
freshwater mussels at the transition from the gray clay to the strange black mud above it.
When their carbon dates came back from the lab they were astounded to find that the first
marine creatures that invaded the freshwater lake were the same age no matter where and at
what depth they sampled. Oxygen depletion and saltwater intrusion started simultaneously
throughout the Black Sea, exactly what one would expect if a sudden flood of salt water
smothered a great freshwater lake.
High-resolution profiles of subsurface layers, mapped by setting off small explosions and
measuring the travel time of the resulting seismic waves, revealed a former land surface
buried in the seafloor sediments. The unconformity defined by the contact between the lay-
ers of sediment above and below this surface extended to depths well below the bedrock
sill at the Bosporus. Drill cores punched into and brought up from the seafloor contained
subaerial desiccation cracks and in-place roots of shrubs covered by marine mud. Changes
in the isotopic composition of different layers in the cores showed it took about a thousand
years for enough seawater to pour into the Black Sea basin from the Mediterranean to be-
gin supporting marine life on the seabed. A later expedition in 2000 discovered evidence
for a shoreline with a cobble beach hundreds of feet below the modern waves.
Ryan and Pitman knew that farming had been practiced in the region for at least a thou-
sand years before the Mediterranean spilled into the Black Sea. Anyone living in the fertile
valley would have been forced to flee with their livestock as their world disappeared be-
neath the rising waters. Archaeologists had found that this time coincided with the onset of
the initial migration of farming cultures into Europe and the floodplains of Mesopotamia.
Here was another candidate for a reasonable explanation of Noah's Flood.
Other scientists have challenged Ryan and Pitman's interpretation of a sudden influx
of salt water into the Black Sea. The assemblage of microscopic marine creatures (fo-
raminifera) recovered from cores drilled into the bed of the Marmara Sea, the water body
