294 PHYSIOGRAPHY OF CENTRAL-ASIAN. DESERTS AND OASES. 
Pliocene sea contemporaneous with the peneplain stage of its peripheral mountains, 
and the very shrunken early-Quaternary sea with the following high-uplifted 
stage of those mountains, still preglacial, the phenomena fall into organic accord; 
for the surface area of a landlocked sea is a direct function of the climate of its 
basin—the climate of its basin varies with the general continental geography 
and all mundane climatic change. Of the geographical factor, most important 
is variation in the shape of the basin; and, as shown in preceding sections, this 
shape changed through a series of erosion cycles with uplifts giving its periphery 
alternately low and high reliefs. 
Assuming, then, that the great Pliocene Aralo-Caspian Sea belonged to the 
peneplain stage at the end of our first erosion cycle, and that the early Quaternary, 
low Aral, and Caspian shrunken survivals of that sea belonged to the high-relief 
stage of its uplifted periphery of mature mountains dissected during our second 
erosion cycle, we are next confronted by the later wide-expanded Aralo-Caspian 
Sea. Knowing that during the third and fourth erosion cycles this basin suffered 
a great mundane change of climate in the glacial period, it is natural to correlate 
phases of its high Quaternary sea with assumed increases of precipitation belonging 
to the glacial epochs. Although we do not, as yet, know how many phases there 
were to the high Quaternary sea, it might roughly be called a glacial sea, leaving 
the epochs to future exploration. It may be that Konshin’s next lower Aralo- 
Caspian shores, when the Gulf of Kara Kum had dried out and only a strait running 
south of Ust-Urt connected the Aral and Caspian, were postglacial. This brings 
us into the third erosion cycle of its high eastern drainage; and the following 
uplift, ushering in our fourth erosion cycle, might account, in part at least, for 
the last historic shrinkage, severing the Aral and Caspian from their recent Usboi 
overflow connection to the two low seas of to-day—withered survivals of a 
glacial mediterranean. 
RECENT DEVELOPMENTS IN THE ALLUVIAL AND FLYING-SANDS ZONES. 
Turning to the other three lowland zones of deposition, we find additional 
data, especially on the more recent developments of this great basin. Glancing 
at a large-scale map we see most of that area from the Caspian to the high eastern 
peripheral ranges covered by dune-sand. Russian geologists have ascribed that 
of the Kara Kum to deflation of its Quaternary sea deposits. But, as we have 
shown, vast nuclei of flying sands inevitably accumulate from wind-work over the 
silted flood-plains of a desert basin, and all areas of its plains in the neighborhood 
of alluviation, whether or not far removed from ancient sea deposits, are charac- 
terized by them. We, therefore, differ by attributing much, if not most, of the 
Kara Kum sands to wind-work over the flood-plains of late Quaternary time. 
Some of it was undoubtedly derived from deflation of marine deposits, but those 
deposits are much more resistant than fresh-dried alluvium, especially than the 
sandspits of its distributary channels. In either case all the sand is ultimately 
of alluvial origin. 
The wide-expanded zone of flying sands we find surrounded by an alluvial 
zone, narrow between it and the southern peripheral ranges, but widening east- 
