The desiccation of the Aralo-Caspian basin,
which communicated with the Black Sea only by a comparatively
narrow and shallow strait along the present valley of Manytsch,
the bottom of which was less than 100 feet above the
Mediterranean, must have been vastly aided by the erosion of the
strait of the Dardanelles towards the end of the pleistocene
epoch, or perhaps later. For the result of thus opening a
passage for the waters of the Black Sea into the Mediterranean
must have been the gradual lowering of its level to that of the
latter sea. When this process had gone so far as to bring down
the Black Sea water to within less than a hundred feet of its
present level, the strait of Manytsch ceased to exist; and the
vast body of fresh water brought down by the Danube, the
Dnieper, the Don, and other South Russian rivers was cut off
from the Caspian, and eventually delivered into the
Mediterranean. Thus, there is as conclusive evidence as one can
well hope to obtain in these matters, that, north of the
Euphrates valley, the physical geography of an area as large as
all Central Europe has remained essentially unchanged, from the
miocene period down to our time; just as, to the west of the
Euphrates valley, Palestine has exhibited a similar persistence
of geographical type. To the south, the valley of the Nile tells
exactly the same story. The holes bored by miocene mollusks in
the cliffs east and west of Cairo bear witness that, in the
miocene epoch, it contained an arm of the sea, the bottom of
which has since been gradually filled up by the alluvium of the
Nile, and elevated to its present position.
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