Russia Morphological Structure Part 3

By | February 21, 2022

Corrugated and displaced it is likewise the slender (approximately 50 km. Wide over less than 200 long, from Sevastopol to Caffa) mountainous fringe that rises on the south-eastern side of Crimea: asymmetrical anticline, mainly limestone (consisting of Cenomesozoic assizes ranging from the Miocene to the Jurassic), on whose steeper side, facing the sea, the fracture lines are highlighted by the emergence of volcanic pillars (in the section between Balaklava and Alušta). Mass, this, isolated as a pillar between the Caucasus and the Balkans and therefore included in the large Mediterranean area of ​​recent folding, although in relation to a compression prior to that which determined the emergence of the first two systems: the western continuation must be sought in the embossed spur of Dobruja. In most cases, the maximum heights go beyond 1500 m. (Roman-Koš 1544, Demir-Kapu 1541, Zeitun-Koš 1538, Čatyr Dag 1528 m.); however the mountain is far from presenting a harsh and decisive aspect, except in correspondence to the SE side, where collapses and rejections capriciously bump the coastal contour. The same local name (Jajla), under which the system is known, is used to indicate the meager summer pastures that stretch out on the steep limestone slopes of the culmination zone. The peninsula, as wide as Sicily (25,727 sq. Km.), However, remains 3/4 in the domain of the circumpontic steppe: the transition between this and the mountain mass is marked by a triple inclined plane, corresponding to the succession of three levels (titonic, Cretaceous, Pontic) divided bycuestas more or less sharply carved.

All the wide selvedge of low lands that borders from N. Euxino and expands between it and the Caspian, to assume the maximum width between the lower Volga and the last slopes of the Urals, corresponds to the accumulation of Neogenic deposits (coastal or lacustrine) and recent (alluvial), which have gradually reduced the dominance of Cenozoic transgressions in this depressed Eurasian sector. The region is gradually degrading towards the E. until it touches negative values ​​around the Caspian (the level of this is −26 below the marine municipality); in the same sense we pass little by little from the steppe to the desert, and to the salty desert, which becomes the rule on the right of the lower Volga. The only emergence, in this plain, is the modest hilly alignment of the Ergeni, which continues that of the heights of the Volga: the river itself once lapped its steepest eastern flank. The Ergeni fall precipitated on the depression of the two Manyč, through which the Caspian communicated with the Euxine; depression partly occupied by small salt lakes (il ′ men ′) and active only at its western end, which ends at the Don near Rostov.

According to Travelationary, the line of the two Manyč is usually assumed as a natural limit between Europe and Asia in this sector: a no less conventional limit is that represented by the course of the Ural; it is also true that the same orographic continuation of the Urals, the M. Mugodžar (discontinuous series of granite-schistose ridges, with volcanic intrusions, which rise a little over 650 m. at most), merges with S. in the undulation barely noticeable of the Kyrgyz steppe.

The limit marked by the Urals is more evident at all times, extending without interruption from 48 ° to 70 ° N. (therefore approximately for 2500 km., And even more if we take into account the offshoots that they push into the islands Vajgač and Novaya Zemlya), and as such represent the longest mountain barrier in all of Europe. A barrier, however, whose effectiveness is greatly reduced by its almost meridian direction, by its modest width (the maximum is around 180 km.), And above all by the low intensity of the relief and its morphology. The system results from a very varied plexus of archaeozoic and paleozoic rocks (crystalline schists, limestones, eruptive rocks), corrugated before the end of the Carboniferous, eroded until late maturity and raised in recent geological times, so as to present the steeper side towards the Siberian plain (towards European Russia one descends almost insensibly). The orogenic thrust, coming from E., came up against the resistance of the so-called block of Ufa (Permico), which is responsible for the characteristic flexion that the mountain axis draws around 55 ° N. The maximum elevations are located in the section north where Narodnaja Gora reaches 1885 m. (slightly lower is the Jaman-Tau, in the southern section), but generally the culmination line is not marked by crests, but by rounded bumps. slightly wavy, except in correspondence with the most resistant strands of quartzite. The height remains on average significantly below 1000 m., And also for this reason the system has never exercised a real isolating function, neither climatic nor,

The Urals are usually divided into three strips, in which the length decreases, and on the other hand increases the width, from N. to S. the most inaccessible and compact area of ​​the system, and the one where glacial erosion appears to have been most intense, but it is also the least known (the existence of a glacier in the M. Sablja group, on 64 ° N. all ‘about). It ends around 62 ° N. The middle Urals, or metalliferous ones, which reach approximately 55 ° N., correspond to the most depressed section (less than 600m on average) and to the one where settlement and transit were easier: the first for the variety and abundance of mineral wealth, the second for the frequency of the steps that interrupt the continuity of the mass, and for the externally softened forms of this, which allow the development of rolling stock up to the highest areas. In the southern section (wild Urals) the system’s keystrokes become more numerous, separated as they are by numerous longitudinal valleys, while the heights become considerable again: and this, better than the still well camouflaged forest mantle, explains why only one road (followed from a railway) can cross it.

The limit reached by the glacial cover in its maximum expansion towards S. is marked wholesale by the transversal Kiev-Rjazan′-Nižnij Novgorod (Gor′kij) -Perm ′, beyond which two more advanced limbs curve, pushing along the course of the Dnieper up to the elbow of Dnepropetrovsk and along that of the Don up to the confluence with the Choper. The traces that remained, however, differ from the N. to the South.: with the most varied morainic-lacustrine topography of the region of the great lakes and of northern Russia, it contrasts that, more uniform and poor, of the middle areas, to which they extended, d on the other hand, only the apparatuses of the penultimate largest glacial expansion. Later most of the extreme northern Russia was covered with deposits of a marine transgression that reached the Baltic from the free Ocean;

Essentially, these glacial and post-glacial events are related to the diversity of surface soils, the distribution of which so clearly and profoundly influences the facts of a geographical nature. At the arctic tundra, which extends up to the wholesale polar circle, and is characterized, as is known, by a subsoil continuously weak ice cream depth, follows in S. wide band of land in podzol, with what name s’ denotes a dusty soil, mostly silica, very poor in mineral elements, resting on impermeable banks and covered with a thin layer of humus ; land covering approximately the 2 / of the whole of Russia and correspond to strips that are completely unsuitable or unsuitable for crops. In the most intense areas the forest, which usually covers them, is replaced by moors and peat bogs; towards S., on the other hand, as humification gradually increases, we pass to the gray soils proper, forming a fairly wide and continuous strip that from Ukraine to the Moscow basin diagonally crosses central Russia up to the upper Volga and Kama.

Beyond the line of maximum glacial expansion, the rocky base is surmounted by a mantle of löss, more recent than the glacial depositions, which in fact covers it in correspondence with the two extreme edges mentioned above. The soil here assumes the characteristic brown coloration which owes its name (is ernozem, or black earth), determined by the slow decay of a thick vegetation of grasses within a subsoil formed by fine sand clay or marl. These soils embrace almost all of southern and eastern Russia, from the Black Sea to the Middle Volga up to Saratov and the central Urals, beyond which they pass into the properly steppe soils and from here to the more or less saline ones of the Circumcaspian desert.

Russia Morphological Structure 3