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The Urals are among the world's oldest extant mountain ranges. For its age of 250 to 300 million years, the elevation of the mountains is unusually high. They were formed during the Uralian orogeny due to the collision of the eastern edge of the supercontinent Laurussia with the young and rheologically weak continent of Kazakhstania, which now underlies much of Kazakhstan and West Siberia west of the Irtysh, and intervening island arcs. The collision lasted nearly 90 million years in the late Carboniferous – early Triassic.[1][2][3][4] Unlike the other major orogens of the Paleozoic (Appalachians, Caledonides, Variscides), the Urals have not undergone post-orogenic extensional collapse and are unusually well preserved for their age, being underlaid by a pronounced crustal root.[5][6] East and south of the Urals much of the orogen is buried beneath later Mesozoic and Cenozoic sediments.[1] The adjacent Pay-Khoy to the north is not a part of the Uralian orogen and formed later.

Many deformed and metamorphosed rocks, mostly of Paleozoic period, surface within the Urals. The sedimentary and volcanic layers are folded and broken, and form meridional bands. The sediments to the west of the Ural Mountains are formed by limestone, dolomite and sandstone left from ancient shallow seas. The eastern side is dominated by basalts similar to the rocks of the bottom of the modern oceans.[7]

The western slope of the Ural Mountains has predominantly karst topography, especially in the basin of the Sylva River, which is a tributary of the Chusovaya River. It is composed of severely eroded sedimentary rocks (sandstones and limestones) that are about 350 million years old. There are many caves, karst sinks and underground streams. The karst topography is much less developed on the eastern slopes. They are relatively flat, with some hills and rocky outcrops and contain alternating volcanic and sedimentary layers dated to the middle Paleozoic period.[7] Most high mountains consist of weather-resistant rocks such as quartzite, schist and gabbro that are between 570 and 395 million years old. The river valleys are laid with limestone.[8]

The Ural Mountains contain about 48 species of economically valuable ores and minerals. Eastern regions are rich in chalcopyrite, nickel oxide, gold, platinum, chromite and magnetite ores, as well as in coal (Chelyabinsk Oblast), bauxite, talc, fireclay and abrasives. The Western Urals contain deposits of coal, oil, natural gas (Ishimbay and Krasnokamsk areas) and potassium salts. Both slopes are rich in bituminous coal and lignite, and the largest deposit of bituminous coal is in the north (Pechora field). The specialty of the Urals is precious and semi-precious stones, such as emerald, amethyst, aquamarine, jasper, rhodonite, malachite and diamond. Some of the deposits, such as the magnetite ores at Magnitogorsk, are already nearly depleted.[8][7]

ReferencesEdit

  1. 1.0 1.1 D. Brown & H. Echtler. The Urals. In: R. C. Selley, L. R. M. Cocks & I. R. Plimer (eds.), Encyclopedia of Geology, Vol. 2. Elsevier, 2005. P 86-95.
  2. L. R. M. Cocks & T. H. Torsvik. European geography in a global context from the Vendian to the end of the Palaeozoic. In Gee, D. G. & Stephenson, R. A. (eds), European Lithosphere Dynamics. Geological Society, London, Memoirs, 32, 83–95.
  3. Victor N. Puchkov. The evolution of the Uralian orogen. Geological Society, London, Special Publications, 2009; v. 327; p. 161-195.
  4. D. Brown et al. Mountain building processes during continent–continent collision in the Uralides. Earth-Science Reviews, Volume 89, Issues 3–4, August 2008, Pages 177–195.
  5. Mary L. Leech. Arrested orogenic development: eclogitization, delamination, and tectonic collapse. Earth and Planetary Science Letters 185 (2001) 149–159.
  6. Jane H. Scarrow, Conxi Ayala & Geoffrey S. Kimbell. Insights into orogenesis: getting to the root of a continent–ocean–continent collision, Southern Urals, Russia. Journal of the Geological Society, London, Vol. 159, 2002, pp. 659–671.
  7. 7.0 7.1 7.2 Template:Cite web
  8. 8.0 8.1 Ural Mountains, Encyclopædia Britannica on-line