and Maly Iremel) and Nurgush. The Southern Urals extend some up to the sharp westward bend of the river Ural and terminate in the Guberlin Mountains and finally in the wide Mughalzhar Hills. Geology 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 formed during the Uralian orogeny due to the collision of the eastern edge of the supercontinent Laurasia 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. 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. East and south of the Urals much of the orogen is buried beneath later Mesozoic and Cenozoic sediments. The adjacent Pay-Khoy Ridge to the north and Novaya Zemlya are not a part of the Uralian orogen and formed later. Many deformed and metamorphosed rocks, mostly of Paleozoic age, surface within the Urals. The sedimentary and volcanic layers are folded and faulted. The sediments to the west of the Ural Mountains are formed of limestone, dolomite and sandstone left from ancient shallow seas. The eastern side is dominated by basalts. The western slope of the Ural Mountains has predominantly karst topography, especially in the Sylva basin, which is a tributary of the Chusovaya. It is composed of severely eroded sedimentary rocks (sandstones and limestones) that are about 350 million years old. There are many caves, sinkholes and underground streams. The karst topography is much less developed on the eastern slopes. The eastern slopes are relatively flat, with some hills and rocky outcrops and contain alternating volcanic and sedimentary layers dated to the middle Paleozoic Era. Most high mountains consist of weather-resistant rocks such as quartzite, schist and gabbro that are between 395 and 570 million years old. The river valleys are underlain by limestone. 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