The geologic history of the Ukraine in the diluvian period was also decidedly different from that of the other districts of Eastern Europe. The Northern European inland ice covered the northwestern borderlands of the Ukraine only in the main ice period, for the boundary set for the glaciation of the north, on the basis of the investigations of Russian scholars, applies in great measure only to the limits of the distribution of northern glacial boulders, which were carried to their present site not by ice but by flowing water. The two indentations of the glaciation-boundary in the Don and Dnieper district merely mark the sphere of action of two glacial river systems.
The absence of a one-time inland-ice-cap differentiates the Ukrainian district very markedly from the other parts of Eastern Europe. As we perceive, even from this short description, the Ukraine has had an entirely different geologic history from the rest of Eastern Europe.
More plainly still, the independence of the Ukraine as a natural unit is revealed in its contour-line and surface-relief. [[7]]The Ukraine is the only portion of the Eastern European plain which has access to the mountainous region, for it rests upon the Carpathians, the Yaila Mountains and the Caucasus. Important individual districts of the Ukraine lie in these mountains and lessen the Eastern European uniformity of the country. The formation of the Yaila and the Caucasus began at the end of the Jurassic period—its completion and the building up of the Carpathians occur in the late tertiary period.
The plains and plateau of the Ukraine, while at first glance quite similar to those of Central Russia, are in reality very different from these as to structure and surface-relief. The nucleus of the Ukrainian plateau group, which is surrounded by the two plain districts of the Ukraine, consists of the so-called Azof Horst (so named by E. Suess), which stretches from the banks of the Sea of Azof in a northwesterly direction as far as Volhynia and Austrian Podolia. This primeval rock surface, composed of granite gneiss, is bounded by quarries and edged with declivities, which are hidden by more recent sediment deposits. Since this extended Horst stretches thru practically the whole length of the Ukraine, we shall call it “the Ukrainian Horst.”
This Ukrainian Horst is of great importance for the entire process of folding, all over the earth. To the west of this Horst is the immense fold-system of the Altai, folded far into North America toward the north and northeast, in direct opposition to the main parts of the enormous system which lie to the east of it. In the east of the Horst we see the straight line of the mountain system of the Caucasus; in the west the winding guide-lines of Central Europe.
The region of the Ukrainian Horst has influenced not only the formation of the plicated country. In connection with it we find, arranged on a grand scale, but not very [[8]]intensive, disintegrating lines, which traverse the entire Ukrainian country from N. W. to S. E. These tectonic disturbances have led to strong folding and dislocation of the more recent sedimentary layers which lie close to the Horst. This folding district can be observed only in the trunk range on the Donetz and in a few isolated places to the northwest; beyond this it is buried under the huge cover of the tertiary layers. The folding process took place in the Donetz Mountains, continuing with long interruptions from the end of the paleozoic era to the beginning of the tertiary period. As pre-tertiary disturbances of this kind we consider the disturbance of Isatchky, Trekhtimiriv, etc., as well as some dividing lines at the northwestern extremity of the Ukrainian Horst.
There is no doubt that the Ukrainian Horst was also the origin of more recent tectonic disturbances—tertiary and post-tertiary. The two main lines of Karpinsky (the northern—Volga, bend of the Don, source of the Donetz, delta of the Desna, South Polissye, Warsaw; the southern—delta of the Don, end of the Porohy of the Dnieper, source of the Boh, Western Podolia) for the most part go back to these more recent post-cretaceous disturbances. Besides, we are already able, despite our insufficient morphological data on the Ukraine, to establish the fact that the entire Ukrainian plateau-group is the scene of a significant post-glacial elevation. The strikingly parallel courses of the main streams, the Dniester, the Boh, the Dnieper as far as Katerinoslav, the Donetz and the Don, together with the precipices frequently accompanying them, lead us to infer the existence of tectonic influences. That the precipices of Podolia are very recent we may now confidently maintain, and that the precipitous bank of the Dnieper is quite as recent is shown by the familiar dislocation near Kaniv, where the tertiary is affected. Seismic movements of the most recent past [[9]]and morphological observations show us that the tectonic disturbances of the Ukraine are continuing into our own day.
From this tectonic characterization of the Ukraine we perceive that this country occupies an independent position in relation to the rest of Eastern Europe. The much more intensive tectonic disturbances of the Ukrainian region have produced a greater variety of plateau and plain country here than in White, Great or North Russia. The Ukrainian plateaus attain the contour-lines of 400 and even 500 meters and reveal precipices of tectonic origin, which for a long time were considered proof of Baer’s law and have recently been explained as Davis Cuestas. The extensive working out of valleys in the Ukrainian plateau regions, the characteristic cañon-like type of the valleys, the frequent occurrence of hills formed by erosion, lack of glacial formations and deposits, but evidences of great erosive and flattening action—these are the chief elements of difference between the plateau lands of the Ukraine and other Eastern European plateau lands. The plains of the Ukraine possess similarities to neighboring Central Europe only in the Northwest. Beyond this, they are all more or less decided steppes, the like of which are not met with in Central Europe, Hungary not excepted. At the same time the character of the steppes of the Ukraine is different from that of the steppe-region of Eastern Russia as well, chiefly because of the detail of the country and the peculiarities of vegetation, which are occasioned by differences of climate.
Hydrographically the Ukraine is distinguished by a web of rivers concentrating in the Pontus. The Ukraine embraces the river systems of the Dniester, Boh, Dnieper, Don and Kuban—not entirely, to be sure, yet by far the greater part, leaving only the sources of the two greatest rivers to the White and Great Russians. Only the most western borderlands of the Ukraine lie within the watersheds [[10]]of the Baltic Rivers (the Vistula district); only the most eastern mountain-spurs in the water-shed of the Caspian Sea (Terek and Kuma). We may therefore, without hesitation, conceive of the Ukraine hydrographically as the northern part of the Eastern European water-shed.
In respect to climate, the Ukraine occupies an independent position in Eastern Europe. In fact, de Martonne recently declared “the Ukrainian climate to be one of the main types of climate of the earth.” We shall not go so far as this, but we must emphasize the fact that the climate of the Ukraine differs no less from that of Poland, White Russia and Great Russia than does Germany’s climate from that of England or France. An important wind-partition crosses the Ukraine in winter from East to West, subjecting the entire southern part to the sway of the east wind. Winter in the Ukraine is strictly continental, with a coldness of 30 degrees, but not with the semi-polar character of the Russian or the Central European character of the Polish winter. The east and southeast winds by day prevent the snow-blankets, produced by the moist south winds of the Pontus, from ever becoming too heavy, especially in the Southern Ukraine, and cause them to disappear quickly in the spring. In the spring the temperature rises very rapidly. The summer of the Ukraine is the hot continental summer, and despite the predominant Atlantic west winds and the abundant precipitation, it is not sultry. Autumn is pleasant and dry.