544 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



Large areas of the sea-bed are covered with sand. The whole southern shore 

 of tne Sea is an alluvial plain, receiving a large number of rivers which flow 

 down from the El'burz range. 



The structure of the eastern shore of the Sea is also peculiar. There is no 

 river inflow, and the deserts border immediately upon the Sea. The contour 

 of this shore is uneven. Abrasion ledges, formed of Neogene carbonate rock, 

 alternate here with low-lying areas with coastal bars and long shoal-heads. The 

 eastern coast alluvium consists mainly of shell gravel and oolitic grains (a 

 variety of granular calcite). 



Large coastal bars and shoal-heads have been formed in many places on 

 this coast by marine sediments thrown up by the Sea. Among them the follow- 

 ing may be noted : the bar of the Kara-Kul lagoon, the bars and shoal-heads 

 of Krasnovodsk Bay and of Kara-Bogaz-Gol Bay, and likewise Ogurchinsky 

 Island and the submarine bank which continues it far to the south (V. Zen- 

 kevitch, 1957). 



In the area of Krasnovodsk and Turkmensk Inlets, with its peculiar struc- 

 ture, the coast has retained its uneven outline. The estuary of the ancient Oxus 

 (Amu-Darya) was situated here. Farther south, and right up to the frontier 

 of Iran, the sand desert of southwestern Kara-Kum borders the Sea. 



Water balance 



The huge area — 3-7 million km 2 — of the Caspian Sea basin receives annually 

 about 355 km 3 of river water (Table 224) : 



This mass of river water flowing into the Caspian Sea, comprising about 

 1/250 of its whole volume, is increased by rainfall to 451 km 3 or to 1/176 of 

 the whole volume. Without evaporation this quantity of water might have 

 raised the level of the Caspian Sea by 123 to 125 cm* in one year. The climatic 

 conditions determining the quantity of river inflow, of rainfall and evapora- 

 tion would, with such a water balance, evidently have a considerable effect 

 on the sea-level, and by influencing the salinity of the upper layers of the Sea 



* V. Prishletzov (1940) determines the average annual evaporation from the whole 

 Caspian Sea as 86-6 cm. 



