National Institute of Informatics - Digital Silk Road Project
Digital Archive of Toyo Bunko Rare Books

practically closed around by high ranges of the Tian Shan, Pamir, Karakoram,
and Altin Tagh, and comes near to an ideal type. But the Western basin, the
one most studied by us, still lies open out over the low steppes of Siberia and
Southern Russia, with but little protection from the Ust-Urt, or low-domed ending
of the Urals. It is, therefore, a basin less isolated and less independent in its
variations of climate than Tarim and other divisions of the Gobi. We must
expect to find that it was more directly influenced by the Quaternary ice mantle
over Russia, as well as by the mundane change that brought about that ice. And,
as already hinted, the cyclical uplifting of mountains was by no means simple, but
took place in huge block-masses rising and tilting in various degrees and relations.
Other facts not brought out by our imaginary basin, but of marked importance
in all large ones, are the disturbances resulting from unequal loading of different
areas and the encroachment of mountains on plains by migration of the tilted
piedmont belt. This is especially well exampled in the western part of Tarim,
where the strata have been tilted up, forming long ridges several hundred feet
high with fault-scarps facing mountainwards and surmounted by gentle slopes
towards the center of the basin. There are sometimes several parallel to each
other and 30 or 40 miles apart, the innermost youngest in appearance as though
migrating from the mountains inwards, stage by stage, to follow the zone of maxi-
mum deposition-load as it moved inwards from cycle to cycle. Why this encroach-
ment took place we can only guess, but that guess must fit in perfectly with the
whole scheme.
I have spoken of the mountains rising by displacement, and there may have
been some doubt as to how that displacement took place. Was it flow in the
hard crust of the earth, which is thought to be miles deep? Or was it a displace-
ment in the supposed magma beneath? There has been a prevalent idea that
some ranges piled up from overriding folds supplied by horizontal thrusting from
both sides, and that others formed by simple folding on lines normal to horizontal
compression, thrust in either case arising from a general contraction of the earth
and wrinkling of its crust. That such was the primal origin of our Central-Asian
ranges may be assumed, as far as this report is concerned. Indeed, the structure
of their interior portions would lead to that conclusion. But without entering at
all into a discussion of their primal origin, a thing that lies back in one of the
earth's great mountain-building epochs, we are still confronted by that series of
peculiar secondary movements of a desert basin with its mountains.
Then, to explain the hypothesis of shifting-load displacement hitherto
assumed: The plains sank with their load of sediments; of that we have ample
proof both in the fault-scarps of high-uplifted blocks along their borders, and
in the Askhabad well-boring, 2,200 feet deep, which penetrated the plains to 1,400
feet below the sea-level, and even then remained in red alluvium and loess like
that laid down on them to-day. It is absurd to suppose they sank into a cavity;
we must assume that matter was displaced. The obvious corollary is that what-
ever displacement took place was to the nearest zone of weakness of the earth's
crust, and there is twofold reason for supposing that the mountains lay over