IIIF Color HighRes
National Institute of Informatics - Digital Silk Road Project
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| IIIF Color HighRes |
| Overland to India : vol.2 |
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Citation Information
ii
L CLIMATIC CHANGES IN PERSIA 231
(2) the intensity of evaporation ; (3) the absorption of water
4 in the ground ; (4) the amount of sediment carried to the
41 lake ; (5) the salinity of the water. As, now, the amount
111 of precipitation diminished during the Post-Glacial period,
'MI the Kevir lake disappeared, or at any rate it entered on a
LIt stage in which it was on the verge of annihilation. The
i; volume of water which is now contributed to the basin,
either directly by rain or indirectly by rivers, is not
hi sufficient to cover the sedimentary deposits, which therefore
iI are exposed to view. The large salt crusts we find in the
II interior of the desert indicate a period of abundant pre-
it; cipitation during the most recent period. When larger
it surface lakes than usual were formed during such moist inter-
Q vals, the salt was deposited in their beds, and then another
it; dry period caused the lakes to disappear. Undoubtedly,
I such accumulations have taken place during a very long
isi space of time. Consequently if a crowbar be thrust in
i' certain places in the Kevir through the surface clay, it comes
b upon a stony salt layer at a depth of a couple of feet. This
salt layer has evidently been precipitated in a very considerable lake, and it has afterwards been covered in the
P~ course of time by fresh silt. A bore-hole in the Kevir
would no doubt reveal a whole series of alternate layers of silt and salt, the latter marking the conclusion of a period
is of humidity, the former a period of the same character in
uu the main as the present one.
Walther calls the transporting work of the wind
t deflation, and considers this power as the principal cause
of the desert relief. This force has, however, no marked validity in a kevir desert : The horizontal surface form itself shows that the wind is powerless in the long-run. We miss the deeply carved-out wind furrows so characteristic of the Lop country and Seistan, where the tremendously
1 violent winds impress on the clay beds such a fantastic
e relief. And that there is no lack of wind any one will
soon be convinced who travels along the southern margin
of the Kevir. On some of the detritus slopes are found quantities of particularly fine specimens of wind-worn
! stones in bowl-shaped and tetrahedral forms. The winds
which have been able to grind down these stones have
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