The balka, like the yar, owes its existence to the erosive activity of flowing waters. On the Dniester we see, on both sides of its deep yars, great masses of old river boulders, which lie on the summit of the plateau beneath the thick cover of loam. They are boulder deposits of the pre-glacial Dniester. Later, when the recent raising of the Ukrainian plateau group began, and it occurred with particular force in the Podolian Plateau, the rivers cut in, and in the course of thousands of years formed their present picturesque defiles.
The entire surface of the Podolian Plateau is covered with a thick mantle of loess, which was formed in the desert and steppe period following the glacial age. In the manner in which the loess is heaped up, in the symmetry of the river valleys, whose western declivities are regularly steeper, in the general arrangement and formation of the valleys of Podolia, the great influence of winds may be distinctly recognized.
The uppermost loess layer has been transformed thruout Podolia into the famous black earth (Chomozem). Hence Podolia has for ages been famous for its fertility. "In Podolia," says an old Ukrainian proverb, "bread grows on the hedgeposts and the hedges are of plashed sausages." On the other hand, Podolia suffers greatly from lack of forests. The large areas of forest which still existed in the 16th and 17th Centuries have now divided to small woods. The effects of forest destruction were not slow. Many springs and brooks have dried up, the rivers have languished, so that in particularly dry summers there is often a dearth of water. On the other hand, after the cutting down of the forests, began the destructive activity of the gorges, which extend after every strong rain and are able in a short time to transform a rich agricultural district into a maze of ravines.
Between the Podolian Plateau and the hilly sub- Carpathian country lies the Pocutian-Bessarabian Plateau. The far-stretching narrow plateau section which lies between the valleys of the Dniester and the Prut is called Pokutye (land in the corner) in the west, while in the east the name Bessarabia (properly Bassarabia) is commonly used. In the west the plateau country reaches the valleys of the Bistritza and Vorona in the sub-Carpathian region; in the southeast it passes over into Pontian steppe-plain. On the Dniester one sees almost no difference between the character of Podolia on the left bank and of Pocutia or Bessarabia on the right. On both sides the same valley slopes, composed of the same rock layers — except that the one on the right bank is more compact, because the Dniester • receives only few and small tributaries on this side. Only at some distance from the course of the Dniester do the peculiarities of the Pokutian-Bessarabian Plateau appear to the view.
The western part of the plateau, which bears the name of Pokutye and extends to the east as far as the hill-group of Berdo-Horodishche, has a level, very flat, undulating surface, And yet it is a typical karstenite country, affected by the existence of great strata of gypsum. The region has a very great number of funnel-shaped depressions which are called Vertep and are altogether analogous to the Carso dolomites. They originated thru the dissolving action of the subterranean water in the gypsum strata. The funnel walls are always steep on one side, gray gypsum rocks rise like walls over the bottom of the funnel, which is often occupied by a small lake. Many brooks disappear in the karstenite funnels, to continue their course as subterranean streams. Nor does Pokutye lack other marks of a karstenite region. The action of the subterranean waters has, by dissolving the gypsum masses, formed large caves, which are famous for their beautiful stalactites of white alabaster. The best known are the cave of Lokitki, near Tovmach, and in the neighboring South Podolia, the caves of Bilche Zolote and the recently discovered magnificent caves of Crivche.
However, the karstenite country of the Pokutye cannot bear comparison with the karstenite regions of Krain, Istria and Croatia. Gypsum is not limestone, and its strength is insignificant as compared with strength of the lime-stone in genuine karstenite regions. A genuine karstenite formation therefore does not exist in Pokutye, and a thick cover of clay is only in exceptional cases broken by gypsum rocks.