Page:Encyclopædia Britannica, Ninth Edition, v. 21.djvu/90

Rh 74 K U S S I A [GEOLOGY, shallow estuary, which receives the "West Bug (450 miles) and the Ingut (220 miles). The traffic of the Dnieper and its tributaries reached in 1882 an aggregate of 12 '9 million cwts. shipped and 67 discharged, the principal items being corn, salt, and timber. (19) The Don (1125 miles), with a basin of about 120,000 square miles, and navigable for 880 miles, rises in south-eastern Tula and enters the Sea of Azoff at Rostoff by thirty mouths, after ibing a great curve to the east at Tsaritsyn, approaching the Volga, with which it is connected by a railway (40 miles). Its navigation is of great importance (5 '4 million cwts. shipped, and 6'1 discharged), especially for goods brought from the Volga, and its fisheries are extensive. The chief tributaries are the Sosna (175 miles) and North Donetz (615 miles) on the right, and the Voronezh (305 miles), Khoper (565 miles), Medvyeditsa(410 miles), and Manytch (295 miles), on the left. (20) The Ylya (192 miles), (21) the Kuban (510 miles), and (22) the Rion belong to Caucasia. D. The Caspian Basin. (23) The Volga, the chief river of Russia, has a length of 2110 miles, and its basin, about 648,000 square miles in area, contains a population of more than 40,000,000. It is connected with the Baltic by three systems of canals (see VOLGA). (24) The Great and the Little Uzen no longer reach the Caspian but lose themselves in the Babinskoyc Lakes. (25) The Ural (1475 miles), in its lower part, constitutes the frontier between European Russia and the Kirghiz Steppe ; it receives the Sakmara on the right and the Ilek on the left. (26) The East Manytch (175 miles) is on the Caucasian boundary. (27) The Kuma (405 miles), (28) the Terek (360 miles), and (29) the Kura (about 650 miles), with the Arax (about 650 miles), which receives the waters of Lake Goktcha, belong to Caucasia. 1 Geology. Almost every geological formation, from the oldest up to the most recent, is met with in Russia ; but, as they are almost horizontal, they for the most part cover one [another over immense spaces, BO that the lower ones appear only at the bottom of the deeper valleys, and the oldest are seen only on the borders of the great Russian plain. At the beginning of the Palaeozoic period only a very few portions of what is now Russia Finland, namely, and parts of Olonetz rose above the surface of the sea ; but, as the result of a gradual upheaval continued through Palaeozoic times, it;is supposed that at the end of this epoch Russia was a continent not greatly differ- ing from the present one. In Mesozoic times the sea began again to invade it, but, while in the preceding period the oscillations resolved themselves into a gradual upheaval extending from west to east, in Mesozoic times the upheaval went on from north-west to south-east. The Mesozoic sea, however, did not extend beyond what is now central Russia, and did not cover the "Devonian plateau" of western Russia, which remained a continent from the Carboniferous epoch. A gradual rising of the continent followed, and was continued through Neozoic times, with perhaps a limited subsidence in the Post-Glacial period, when the actual seas extended their narrow gulfs up the.valleys now occupied by the great rivers. During the first part of the Glacial period, Russia seems to have been covered by an immense ice-sheet, which extended also over central Germany, and .of which the eastern limits cannot yet be determined. Tho Archaean gneisses have a broad extension in Finland, northern Russia, the Ural Mountains, and the Caucasus ; they form also the back-bone of the ridge which extends from the Carpathians through southern Russia. They consist for the most part of red and grey gneisses and granulites, with subordinate layers of granite and granitite. Tho Finland rappa-kivi, the Serdobol gneiss, and the Pargas and Rustiala marble (with the so-called Eozoon cana- dense) yield good building stone ; while iron, copper, and zinc-ore are common in Finland and in the Urals. Rocks regarded as representing the Huronian system appear also in Finland, in north- western Russia, as a narrow strip on the Urals, and in the Dnieper ridge. They consist of a series of nnfossiliferous crystalline slates. The Cambrian is represented by blue clays, ungulite sandstones, and bituminous slates in Esthonia and St Petersburg. The Silurian system is widely developed, and it is most probable that, with the exception of the Areha3an continents of Finland and the Urals, the Silurian sea covered the whole of Russia. Being con- cealed by more recent deposits, Silurian rocks appear on the surface i llibliographij. The lengths of the rivers of European Russia as ascertained by accurate measurements are given by Tillo, in fzrettia of Geogr. Soc,, 1883. See also Srnckenbcrg, Jlydr. <le* R. lleichs ; ScrocnofT, Geogr. Statist. Dictionary (the most reliable source for all the geography of Russia). Strelbltzky, Svper- ftciei tie r Europe; H. Wagner, "Studlen im Geb. d. Areal-statistik," in the Slat. Monattfchrift, viii.; official Stod llateriqloff, with regard to Russian rivers, 1876; Statistical Sbornik of the Min. of Communications, vol. x. (freezing of Russian rivers, and navigation). Besides the military statistical descriptions of separate governments, a great variety of monographs dealing with separate rivers and basins are also available; e.g., Sidoroff, The 1'elchora lieijion. and North Rutsia; Ilehnersen, Olontlzer Dergrmier; Turbin, The Dnieper; 1'raso- lenko, " The Dniester," in Engin. Journ., 1881 ; Danilcvsky, " Kuban," in M,in. Gtogr. Soc., i.; Baer, Ctupitche Studifn ; Rapozin, Volga ; Peretyatkovitch, Volga; Mikhailoff, Kama; <tc. An oro-hydrograpliical map of Russia in four sheets was published in 1878; see also Tillo, Orogr. Map o/ Rustia ; the ordinance maps of Russia; and Tillo, "Magnetical Maps of Russia." in lit. of Geogr. Soc., 1884 and 1885. only in north-western Russia (Esthonia, Livonia, St Petersburg, and on the Volkho(l'), where all European subdivisions of the system have been found, in the Timan ridge, on the western slope of the Urals, in the Pai-kho riilgt 1, and in the islands of the Arctic Ocean. In Poland it i.s met with in the Kielce mountains, ami in Podolia in the deeper ravines. The Devonian dolomites, limestones, and red sandstones cover immense tracts and appear on the surface over a much wider area. From Esthonia these rocks extend north-east to Lake Onega, and south-east to Moghilefl'; they form the central plateau, a.s alsn the slopes of the Urals and the Pctchora region. In north-western and midtlle Russia they contain a special fauna, and it appears that the Lower Devonian series of western Europe, represented in Poland and in the Urals, is missing in north-western and central Russia, where only the Middle and Upper Devonian divisions are found. Carboniferous deposits cover nearly all eastern Russia, their west boundary being a line drawn from Archangel to the upper Dnieper, thence to the upper Don, and south to the mouth of the last-named river, with a long narrow gulf extending west to encircle the plateau of the Donetz. They are visible, however, only on the western borders of this region, being covered towards the cast by thick Permian and Triassic strata. Russia has three large coal-bearing regions the Moscow basin, the Donetz region, and the Urals. In the Valdai plateau there are only a few beds of mediocre coal. In the 'Moscow basin, which was a broad gulf of the Carboniferous sea, coal appears as isolated inconstant seams amidst littoral deposits, the formation of which was favoured by freijui nt minor subsidences of the sea-coast. The Donetz coal-measures, containing abundant remains of a rich land-flora, cover nearly 16,000 square miles, and comprise a valuable stock of excellent anthracite and coal, together with iron-mines. Several smaller coal-fields on the slopes of the Urals and on the Timan ridge may be added to the above. The Polish coal-fields belong to another Carboniferous area of deposit, which extended over Silesia. The Permian limestones and marls occupy a strip in eastern Russia of much less extent than that assigned to them on geological maps a few years ago. The variegated marls of eastern Russia, rich in salt-springs, but very poor in fossils, are now held by most Russian geologists to be Triassic. Indisputably Triassic deposits have been found only in the two Bogdo mountains in the Kirghiz Steppe (CampHcr-Schichtcn) and in south-western Poland. During the Jurassic period the sea began again to invade Russia from south-cast and north-west. The limits of the Russian Jurassic system may be represented by a line drawn from the double valley of the Sukhona and Vytchegda to that of the upper Volga, and thence to Kieff, with a wide gulf penetrating towards the north- west. "Within this space three depressions, all running south-west to north-east, are filled Tip with Upper Jurassic deposits. They are much denuded in the higher parts of this region, and appear but as isolated islands in central Russia. In the south-cast all the older subdivisions arc represented, the deposits having the characters of a deep-sea deposit iu the Aral-Caspian region aud on the Caucasus. The Cretaceous deposits sands, loose sandstones, marls, and white chalk cover the region south of a line drawn from the Niemen to the upper Oka and Don, and thence north-east to Simbirsk, with the exception of the Dnieper and Don ridge, the Yaita Mountains, and the upper Caucasus. They are rich in grind- ing stone, and especially in secondaiy layers of phosphorites. The Tertiary formations occupy large areas in southern Russia. The Eocene covers wide tracts from Lithuania to Tsaritsyn, and is represented in the Crimea and Caucasus by thick deposits belong- ing to the same ocean, which left its deposits on the Alps and the Himalayas. Oligocene, quite similar to that of North Germany, and containing brown coal and amber, has been met with only in Poland, Courland, and Lithuania. The Miocene (Sarmatian stage) occupies extensive tracts in southern Russia, south of a line drawn through Lublin to Ekatcrinoslaff and SaratofT. Not only the higher chains of Caucasus and Yaita, but also the Donetz ridge, rose above the level of the Miocene sea, which was very shallow to the north of this last ridge, while farther south it was connected both with the Vienna basin and with the Aral-Caspian. The Pliocene appears only in the coast region of the Black and Azoff Seas, but it is widely developed in the Aral-Caspian region, where, however, the Ust-Urt and the Obshchiy Syrt rose above the The thick Quaternary, or Post-Pliocene, deposits which cover nearly all Russia were for a long time a puzzle to geologists. They consist of a boulder clay in the north and of loess in the south. The former presents an intimate mixture of boulders brought from Finland and Olonetz (with an addition of local boulders) with small gravel, coarse sand, and the finest glacial mud, the whole bearing no trace of ever having been washed up and sorted by water in motion, except in subordinate layers of glacial sand and gravel ; the size of the boulders decreases on the whole from north to south, and the boulder clay, especially in northern and central Russia, often takes the shape of ridges parallel to the direction of the