The chalk and tertiary substratum appears only in very few places, the rest being covered everywhere by sand and loam, which include boulders and rubble of Finnic-Scandinavian origin. These are traces of the great (second) [[55]]glacial period of Northern Europe, which covered the entire region of the Pidlassye with glacial ice. The lakes are morain-lakes. The ice of the glacial period did not reach Pidlassye. At that time a broad primeval river valley formed here as an extension of the primeval Vistula river valley. In this valley the water from the melting glacier flowed off to the east toward the lowland of the Polissye.
The Polissye (woodland) is one of the most remarkable lands of Eastern Europe. Only a low (170 m.) and very flat divide, which is crossed without difficulty by the Dnieper-Buh ship canal, separates the Polissye from the Pidlassye. In the north the White Russian Plateau approaches, in the south the Volhynian, in the east the Polissye extends beyond the Dnieper to the spurs of the Central Russian Plateau. The region thus bounded forms an immense flat trough, in the vertical axis of which the Pripet River flows. The bottom of this trough is very flat and lies at a height of 120–150 m. Only in places do we find almost imperceptible rises of ground. The substratum of the Polissye is composed of chalk marl with numerous holes made by springs (vikno = window), while in the east oligocene formations also appear. But this substratum is seen very seldom, all the rest of the Polissye being covered with diluvial sands and great swamps. The sands take in all the elevated places and form wandering or wood-covered dunes. These sandy rises of ground, together with the elevated banks of some of the rivers, afford the only sites for human abodes. All the remaining land is marshy wood, genuine forest swamps, bog or moor. The Pripet with its tributaries, the Stokhod, Stir, Hornin, Ubort, Uz (on the right) and the Pina, Yassiolda, Sluch, and Ptich (on the left), comprises the water system of the Polissye. All these rivers flow very slowly and deposit the mud which they bring from the plateau regions surrounding the Polissye along their courses. By this means [[56]]they raise their beds and their banks more and more, so that all these Polissian rivers flow upon flat dams. At the time of high water the rivers overflow their banks and flood the entire lowland far and near. At the time of the melting of snows in the spring, or of the strong showers in the early summer, the entire Polissye is transformed into an immense lake, above whose surface only the flooded forests and the settled sandy elevations of ground are visible. The spring flood lasts from two to three months, the summer floods the same length of time, for the water flows off very slowly because of the slight decline. On the highways and railroads all traffic is blocked and certain places in the Polissye may be reached only by water. During the flood period the rivers have often sought new beds, and this explains the frequency of old river beds and river branches, which are peculiar to all the Polissian river courses. And, as reminders of the floods, innumerable pools and marsh lakes remain behind.
These periodic floods are the main cause of the continuance of the Polissian swamps. We can find two main types of marshes in the Polissye. In the west and north of the region, great peat moors, with pine woods, predominate; in the south and east treeless marsh meadows, overgrown with willow brush. These are called hala. Many fictions are told by the inhabitants of the Polissye about the swamps and small marsh lakes being bottomless. For a long time it was even believed that the swamps lay lower than the normal surface of the rivers. But exact measurements have proved these “fairy tales” to be false and have shown that the swamps of the Polissye are not deep and lie at a higher level than the rivers. Since 1873 the Russian government has been working to drain the swamps and reclaim them for civilization. Up to 1898, 6000 kilometers of canals are supposed to have been dug and 32,000 square kilometers of ground made usable.
The glacial period was of great importance for the [[57]]surface configuration of the Polissye. Apart from the traces of the main glacial period, which are met with frequently in southern Polissye, it was the third glacial period that was of marked significance. The water from the Baltic glacier flowed off thru the region of the present Polissye and formed a large lake with the Dnieper as its outlet. The deposits of this lake are to be found especially in the south of the Polissye basin. The lake was then gradually filled in, the northern and western tributaries bringing more sand, the southern ones mud. At the same time the Pripet River cut in more deeply, and was, therefore, constantly more able to carry the waters of the Polissye to the Dnieper River. Swamps have taken the place of the lake and have gradually covered the entire land. The many smaller lakes of the region (the largest of them are Vihonivske Ozero and Knias) are the only remains and proofs of the one-time great lake. Only at the time of high water does the Polissye recall the memory of former times.
Dreary is the Polissian landscape. The dark forest in the deep-bottomed swamps alternate with the open marsh-meadow covered with pools; with gliding flow the many-armed rivers traverse the gloomy country. On yellow-white sand-dunes stand a few log-houses amid wretched little fields and poor meadows, corduroy and brush roads stretching for miles connect small, very sparsely scattered human settlements.
The Polissye Plain also extends to the left bank of the Dnieper, and there imperceptibly passes over into a comparatively narrow lowland district which stretches along the main river of the Ukraine. This is the third member of the series of plains of the Ukraine—the Dnieper Plain. It extends toward the southeast as far as the region of the rapids (porohi) of the Dnieper and rises slowly toward the northeast, passing over into the Central [[58]]Russian Plateau. The transition takes place so imperceptibly that the difference in the nature of the country only becomes apparent at the furthest bounds of Ukrainian territory, which practically lie in the southern spurs of the Central Russian Plateau.
The Dnieper Plain is quite level only along the river itself. Every year a strip of the plain, in places 10 km. wide, is flooded by the Dnieper River, wherefore it is full of old river beds and swamps, on the Desna and near Cherkassy, where the lowland, too, enters upon the right Dnieper bank, and also of sand-dunes. Near Chernihiv and Uizin the landscape is quite Polissian and the name Polissye, too, is often used here to denote the region. Toward the southeast the Polissian character begins to gradually disappear. Black earth takes the place of the sandy soil, the forest mantle becomes constantly thinner, and the flat, undulating steppe-plain, with its innumerable barrows and plate-shaped depressions of ground, where, in springtime, small steppe lakes glisten in the sunlight, increases very rapidly.
The river valleys, along which the Dnieper Plain intrudes far into the Central Russian Plateau, are very wide valley slopes on the right, and flat slopes on the left side. Sand, swamps and forest terraces cover the flat valley bottoms, which are flooded every spring.
At the porohs of the Dnieper the country rises much higher than at Pereyaslav or Kreminchuk, where the Dnieper Plain rises barely 50 m. above sea-level. At the porohs the landscape on both sides is that of a low rock-plateau. The picturesque rocks of the Dnieper banks, the rapids and ledges of rock in the river bed, everywhere remind us that here the Ukrainian Horst is crossed by the main stream of the Ukraine. Not until we get down to the Zaporoze (land below the rapids) do we find the genuine lowland character again—in the Pontian Steppe-plain. [[59]]
The transition of the Dnieper Plain to the southern spurs of the Central Russian Plateau is marked only by the rising of the valley slopes of the tributaries of the Dnieper in this region. Beyond that, the surface of the high bog, lying between the rivers, remains as flat and level as on the Dnieper and below the 200 m. level. Moreover, the spurs of the Central Russian elevation nowhere within Ukrainian territory attain the level of 300 m. The spur between the Dnieper and the Desna barely reaches a height of 230–240 m.; near the high Desna bank, the spur between the Desna and the Sem barely 260 m. About the sources of the Sem, Psiol and Donetz, the country attains a summit height of 280 m.; between the upper Donetz and Don only 250–260 m. From these highest regions the country declines imperceptibly but steadily toward the southwest, south and southeast.