The Ural Mountains are the main orographic system of Russia. Running from north to south, they form the natural boundary between Europe and Asia. This mountain range is 2,365 km (1,470 miles) long and it extends from the Arctic to Kazakhstan, east of the Caspian Sea. The highest peak is Mt Narodnaya, which is 1,895 m (6,216 feet) high. The Urals harbor the richest mineral deposits on Earth as it varies in width from 40 km (24.8 miles) to 150 km (93 miles). Meanwhile, the rivers that originate in the Urals drain either into the Arctic Ocean or into the Caspian Sea. The Pechora and Usa on the western slope and the Tobol, Iset, Tura, Lozva, and Severnaia Sosva rivers (all part of the Ob system) on the eastern slope flow into the Arctic, while the Kama River and the Ural River drain into the Caspian Sea.
The Ural Mountains are divided into the Polar, Subpolar, Northern-Central, and Southern Urals. The Polar Urals have average elevations of 1,000 and 1,200 m, rising to 1,499 m on Mount Paier, with ridges having rounded summits. The Subpolar Urals have the highest peaks, Mount Narodnaya (1,895 m) and Mount Karpinskii (1,878 m), and attain a maximum of 150 km. Many of their ranges, among them the Issledovatel’skii and Sablia, have serrated ridges and are deeply and densely dissected by river valleys. Traces of Pleistocene mountain and valley glaciation in the Polar and Subpolar Urals include cirques, U-shaped valleys, and moraines. Modern glaciation is also extensive; the largest of the 143 glaciers that cover the Polar and Subpolar Urals are the IGAN, MGU, and Dolgushin glaciers. Intergelisols are common.
Stretching from north to south, the Northern-Central Urals consist of a series of parallel ranges rising to 1,000–1,200 m and longitudinal depressions. They typically have flat summits, although the upper parts of the higher mountains, notably Tel’posiz (1,617 m) and Konzhakovskii Kamen’ (1,569 m), have a more rugged topography. The greatly worn down Central Urals are the lowest mountains in the system, rising to 994 m on Mount Srednii Baseg. The topography of the Southern Urals is more complex. The numerous ranges of different elevations, trending southwest or north-south, are dissected by deep longitudinal and transverse depressions and valleys. The highest peak is Mount Iamantau (1,640 m).
Karst topography (area of limestone) is extensively developed on the western slope of the Urals and in the Ural Region, particularly in the basin of the Sylva River, a tributary of the Chusovaia. There are many caves (Div’ia, Kungur, Kapova), basins, sinks, and underground streams. The eastern slope has fewer karst formations. Rocky outliers such as the Sem’ Brat’ev, Chertovo Gorodishche, and Kamennye Palatki rise above its flattened or gently rolling surface. Wide foothills, reduced to peneplain, adjoin the Central and Southern Urals on the east, broadening the Southern Urals to 250 km.
Minerals
The Ural region holds many useful and valuable minerals used by the industry. Forty-eight of the 55 most important minerals processed and used in Russia are found in the Urals. The eastern Urals are noted for their deposits of copper pyrite (Gai, Sibai, and Degtiarsk deposits and the Kirovgrad and Krasnoural’sk groups of deposits), skarn-magnetite (deposits of Mount Vysokaia, Mount Blagodat’, and Mount Magnitnaia), titanomagnetite (Kachkanar and Pervoural’sk), nickel ironstone (Orsk-Khalilove group of deposits), and chromite ores (deposits of the Kempirsai massif), mostly confined to the greenstone belt.
The eastern slope also has coal seams (Cheliabinsk coal basin) and placer and native deposits of gold (Kochkar’, Berezovo) and platinum (Isovka). The Severoural’sk Bauxite Region and the vast Bazhenov asbestos deposits are on the eastern slope. On the western slope of the Urals and in the Ural Region there are deposits of hard coal (Pechora and Kizel coal basins), petroleum (Volga-Ural Oil-Gas Region, Orenburg gas condensate deposit), and potassium salts (upper Kama basin). The Urals are especially famous for their precious, semiprecious, and ornamental stones, including emeralds, amethysts, aquamarine, jasper, rhodonite, and malachite. The best jeweler’s diamonds in Russia come from the Urals.
Geological Structure
The Ural Mountains are a late Paleozoic (Hercynian) folded region lying within the Ural-Mongolian folded geosynclinal belt. Deformed and frequently metamorphosed rocks, chiefly Paleozoic, crop out on the surface in the Urals. The region’s sedimentary and volcanic strata are highly folded and broken by fractures, but in general they form north-south bands, which account for the linear and zonal structure of the Urals.
Six geological zones may be distinguished from west to east: (1) the Cis-Ural Foredeep, with a comparatively gentle bedding of sedimentary layers on the west and a more complex bedding on the east; (2) the Western Slope Zone, whose Lower and Middle Paleozoic sedimentary layers are intensively folded and dislocated by thrusts; (3) the Central Ural Uplift, where the more ancient crystalline rocks of the margin of the East European Platform crop out in places among Paleozoic and Upper Precambrian sedimentary strata; (4) the “greenstone belt,” a system of troughs and synclinoria on the eastern slope (of which the largest are the Magnitogorsk and Tagil’ synclinoria), filled chiefly with Middle Paleozoic volcanic strata and marine (often deep-sea) sediments intruded by plutonic igneous rocks (gabbroids, granitoids, and sometimes alkaline intrusives); (5) the Ural-Tobol’ Anticlinorium, with outcrops of more ancient metamorphic rocks and extensively developed granitoids; and (6) the Eastern Ural Synclinorium, in many ways similar to the Tagil’-Magnitogorsk synclinorium.
Using geophysical data, Soviet geologists had established that the first three geological zones rest on an ancient Precambrian basement composed chiefly of metamorphic and magmatic rocks and formed in the course of several epochs of folding. The most ancient rock, believed to be Archean, crops out at the Taratash protrusion on the western slope of the Southern Urals. Pre-Ordovician rocks are unknown in the basement of the synclinoria of the eastern slope of the Urals. It is thought that the thick plates of ultrabasites and gabbroids that crop out in places in the Platinonosnyi and analogous belts serve as the basement of the Paleozoic volcanic strata of the synclinoria. These plates may possibly be broken-off remnants of the ancient sea floor of the Ural geosyncline. Some ancient outcrops in the Ural-Tobol’ Anticlinorium in the east are perhaps Precambrian.
The Paleozoic beds of the western slope of the Urals are composed of limestones, dolomites, and sandstones that were formed for the most part in shallow seas. To the east lies a discontinuous strip of deep-sea continental slope sediments. Still further to the east, on the eastern slope of the Urals, the Paleozoic (Ordovician and Silurian) cross-section begins with altered basaltic volcanites and jaspers that are comparable to the rocks of the present-day ocean floor. Thick spilite-natroliparite strata, also altered and containing deposits of copper pyrite ore, occur in places higher up in the cross section.
0 Comments