Encyclopaedia Britannica > Volume 21, ROT-Siam

74
RUSSIA
[geology.
shallow estuary, which receives the West Bug (450 miles) and the
Ingut (220 miles). The traftic of the Dnieper and its tributaries
reached in 1882 an aggregate of 12-9 million cwts. shipped and
6 7 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
describing 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
5'1 discharged), es .cially 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 Babinskoye 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, so 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 ot 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. Ihe 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.
The 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. The 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
rnu ert ^le.y co.nsi‘st °f 3- series of unfossiliferous crystalline slates.
^ j Cumbrian is represented by blue clays, ungulite sandstones,
and bituminous slates in Esthonia and St Petersburg.
The Silurian sj'stem is widely developed, and it is most probable
that, with the exception of the Archaean 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
1 Bibliography. The lengths of the rivei s of European Russia as ascertained
by accurate measurements are given by Tillo, in Izvestia of Geogr. Soc., 1883.
See also Stuckenberg, Hydr. des R. Reichs ; Semenoff, Geogr. Statist. Dictionary
(the most reliable source for all the geography of Russia). Strelbitzky, Super-
H' ^a?n,eV Stud!en ira Geb- d- Areal-statistik,” in the Stat.
Monatsschrift, viii.; official Svod Materialoff, with regard to Russian rivers,
1876; Statistical Sbormk of the Min. of Communications, vol. x. (freezing of
and navigation). Besides the military statistical descriptions of
f°7er.nments> f great variety of monographs dealing with separate
w iare alS° a7llabIe; «•?•. Sidoroff, The Petchora Region, and
North Russia, Helmersen, Olonetzer Bergrevier; Turbin, The Dnieper; Praso-
c ’ D"leste^ m. E”Tn- Journ., 1881; Danilevsky, “ Kuban,” in Mem.
Miuwnuv’ ir 2amSKhe Rag°zln> Volga; Peretyatkovitch, Volga-.
Mikhailoff, Kama.; &c. An oro-hydrographical map of Russia in four sheets
^f we alSf-Tll|l0A0r°9r- Map 7 Russia; the ordinance maps
of Ras0s'a> and TlUo> Magnetical Maps of Russia,” in Izv. of Geogr. Soc., 1884
cllld looO. ° 7
only in north-western Russia (Esthonia, Livonia, St Petersburg
and on the Volkhoff), where all European subdivisions of the
system have been found, in the Tinian ridge, on the western slope
of the Urals, in the Pai-kho ridge, and in the islands of the Arctic
Ocean. In Poland it is met with in the Kielce mountains, and 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 Moghileff; they form the central plateau, as also the
slopes of the Urals and the Petchora region. In north-western and
middle 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 east 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 frequent
minor subsidences of the sea-coast. Ihe 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 (Campiler-Schichten) and in south-western Poland.
During the Jurassic period the sea began again to invade Russia
from south-east 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 up 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-east all
the older subdivisions are represented, the deposits having the
characters of a deep-sea deposit in the Aral-Caspian region and 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
i aita Mountains, and the upper Caucasus. They are rich in grind¬
ing stone, and especially in secondary 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 Ekaterinoslaff and Saratoff. 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
sea.
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