Those of the
shallower northern half of the Caspian are similarly affected by
the Volga and the Ural, while, in the shallow bays of the
southern division, they become extremely saline in consequence
of the intense evaporation. The Aral Sea, though supplied by the
Jaxartes and the Oxus, has brackish water. There is evidence
that, in the pliocene and pleistocene periods, to go no farther
back, the strait of the Dardanelles did not exist, and that the
vast area, from the valley of the Danube to that of the
Jaxartes, was covered by brackish or, in some parts, fresh water
to a height of at least 200 feet above the level of the
Mediterranean. At the present time, the water-parting which
separates the northern part of the basin of the Caspian from the
vast plains traversed by the Tobol and the Obi, in their course
to the Arctic Ocean, appears to be less than 200 feet above the
latter. It would seem, therefore, to be very probable that,
under the climatal conditions of part of the pleistocene period,
the valley of the Obi played the same part in relation to the
Ponto-Aralian sea, as that of the Kishon may have done to the
great mere of the Jordan valley; and that the outflow formed the
channel by which the well-known Arctic elements of the fauna of
the Caspian entered it.
Pages:
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56