OPENING UP LAND FOR CULTIVATION I589 



the province of Astrakan or nearly 11 million acres. This pro\dnce is di- 

 vided into two almost equal parts by the lower Volga ; the western half 

 occupied almost entirely by the Kalmuks steppe, and the eastern side 

 which forms the Kirghiz steppe. On the western boundary is the Pla- 

 teau of Ergenia which constitutes the watershed between the basins of the 

 Don and the Volga and separates the Transdon steppe from the Kalmuks. 

 The north of the Kalmuks steppe and the whole of the Transdon steppe 

 (which covers an area of some 5 % million acres) are almost completely 

 free from shifting sand. Travelling south through the Kalmuks steppe, 

 patches of loose sand become more frequent and larger till finally they 

 form a continuous surface which also extends up the right bank of the 

 Volga. 



To the east of the Volga between the northern boundary of Astra- 

 kan and Khanskaia Stavka the soil is only occasionally loose and shifting, 

 but south and east of that district begins a vast sandy tract which gra- 

 dually merges into a true desert, where there is not a sign of vegetation 

 and where the surface has been blown up mto dunes which are continually 

 being remodelled by the wind, This sandy tract of eastern Astrakan 

 extends over about nine and half million acres and makes up 88 per cent 

 of the total desert steppe in the eastern provinces of Russia. 



Geological conditions. — Tlie whole of Astrakan including Ergenia has 

 a common geological origin, i. e. black, compact, impermeable clays of 

 the lower tertiary which hold up the underground water. In the Er- 

 genia area these are covered by oligocene sandstones readily disintegra- 

 ted and overlaid by clays and loams whose derivation is still obscure and 

 which gradually pass into loess at the surface. 



In the main Astrakan plain, which was once the bed of the Aral- 

 Caspian Sea, the changes in sea level have destroyed the sandstones and 

 these have been replaced by a series of deposits which are sandy at the 

 base and clay above. The most important of these sediments is a dark 

 shaly clay which often comes to the surface in ravines and gives rise to 

 agricultural soil. It varies in thickness from 2 % to 23 feet, is plastic 

 and heavily charged with mineral salts (gj-psum, sulphate of soda and 

 carbonates). Above the clay are two more recent deposits, /. e. a thin 

 layer of grey sand covered by an aeolian deposit of yellow sand. 



The actual surface of the steppe at present is one vast expanse of loose 

 sands, the products of the disintegration of the verj^ friable uppermost 

 layers. As these layers for the most part only varj^ in thickness from 2 

 to 10 inches, they could not possibly supply alone the enormous quan- 

 tities of sand on the Astrakan plain. The remainder is derived from 

 adjoining depressions in which cyclones sweep with such force that the 

 Caspian clays have been laid bare in places. 



The Astrakan sands consist of well rounded grains, 3'ellow in colour 

 owing to the presence of oxides of iron, and very fine (o.i to 0.2 mm in 

 chameter). The smoothness of the grains gives the sand a ver^^ unstable 

 character with no power to resist the force of the wind which piles them 

 up into shifting dunes. 



