Next let us assume that the diurnal-rotation velocity decreases. The flow of surface and subsurface water into the Aral-Caspian basin will then tend to shift poleward, and due to the geomorphological features of the locality this flow will become deviated toward the Aral basin. The level of the Caspian will drop, more in the southern part than in the northern part, and the level of the Aral will rise. Actually, as Berg has pointed out, such a behavior of the seas is observed: the fluctuations in the level of the Caspian Sea over the centuries are in general opposite to the fluctuations in the level of the Aral.
Thus the total volume of water in the Caspian depends not only on the precipitation and evaporation there and on possible tectonic movements, but also on the magnitude of the centrifugal forces associated with the Earth's rotation. All these factors are in turn related somehow or other to the fluctuations in climate.
The Kura. The alluvial plain of the Kura was created mainly during the upper Quaternary. Several large, independent deltas were formed, the river moving on and successively leaving each one behind. In addition to the present delta, five delta formations of the Kura exist. These formations are located alternately to the left and to the right of the river (Egorov, 1959).
This regularity in the evolution of the Kura deltas can be explained in the following way. The deltas located on the right bank of the river (the first, third, and fifth) were formed during periods of climatic cooling. At such times the diurnal velocity of the Earth was higher and the Kura deviated southward under the influence of the centrifugal forces, thus flowing to the south of its previous delta (Figure 9). The deltas on the left bank, on the other hand (the second, fourth, and sixth), were formed during periods of climatic warming, when the Earth's rotational velocity was reduced. At such times the centrifugal forces were less and the Kura deviated northward, thus flowing to the north of its previous delta.
Consequently, the regular distribution of the deltas of the Kura indicates the fluctuational character of the Earth's diurnal-rotation regime.. Unfortunately, however, due to the lack of data, it is impossible to relate the formation of any of the deltas except the last two to a specific climatic period. We only know that the sixth (last) delta began forming with the onset of the third (present) warm period, and that the fifth delta (the Sal'yany delta) formed during the third cold period (late Middle Ages).
Egorov (1951) notes that the fifth lobate delta of the Kura is about 150 years old. Previously the river discharged into Kirov Bay, and the traces of a vast delta are visible on the banks of the latter.
The Rioni. In general this river follows a westerly course. The Rioni used to divide its flow between two southwestward-flowing estuarine channels, one to the north and one to the south, and empty into the Black Sea near the town of Poti.
Then, with the onset of the third (present) warm period, the Rioni began to deviate to the right; as a result, the flow in the southern branch of the river diminished while the flow in the northern branch increased. In an attempt to check the northward shift of the river, a dam was erected along the right bank of the Rioni, from the Tsivido River to Poti. At the mouth itself, however, where the water rise. was especially high, the Poti levee was constructed, to protect the town from floods.
In order to prevent overflowing of the river within the town limits, it was decided to divert some of the water to an artificial channel situated to the north of the actual channels. However, even before the completion of the new channel (the Rionsbros), the river broke through the wall and streamed to the sea. At present up to 90% of the river flows out along the Rionsbros, whereas the mouth of the southern branch has been completely closed off. "The Rioni now occupies a more or less stable position, although there is some tendency toward a further shift to the north" (Motsereliya, 1954).
The Kuban'. In its lower reaches the Kuban' follows in general a westerly course and divides into two main branches: the Kuban' proper, to the south, about 120 km long, and the Protoka, to the north, about 130 km long (Figure 10). Simonov (1958) points out that in its lower reaches the southern branch has repeatedly changed from a southwesterly to a northerly course, thereby emptying into the Black Sea at times and into the Sea of Azov at other times. During the second cold period (antiquity) the river deviated to the left (equatorward) and emptied into the Black Sea. Therefore during the period of Greek colonization the Taman' Peninsula was "many-islanded", comprising the islands of Cimmeria, Phanagoria, Sintica, and others.