STUDY NOTES for SSC and STATE LEVEL EXAMS Write Us : [email protected] Myshop
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STUDY NOTES FOR SSC AND STATE LEVEL EXAMS Write us : [email protected] www.mahendras.org www.mahendraguru.com myshop.mahendras.org STUDY NOTES FOR SSC AND STATE LEVEL EXAMS MOUNTAINS & RIVERS Mountains come under the second order of relief features. This is a portion of land surface rising considerably above the surrounding country, either as a single eminence or in a range or chain. A mountain may have several forms. • Mountain Ridge - a system of long, narrow and high hills. • Mountain Range - a system of mountain and hills having several ridges. • Mountain Chain - Consists of several parallel, long and narrow mountains of different periods • Mountain Group - Consists of several unsystematic patterns of different mountain system. • Mountain system - Consist of different mountain ranges of the same period. Types of Mountains 1. Folded Mountains (Geosynclines) • Most of the Fold Mountains are the youngest mountains in the world. • The main examples are the Himalayas, the Alps, Rockies, and the Andes. • The Fold Mountains are formed by compression when two hori zontal forces act towards a common point that compresses the intervening rock strata to produce fold mountains. • The fold consists of two inclined parts called limbs, the upper portion is called anticlines, while the lower portion is called synclines. On the basis of the period of origin folded mountains are divided into: (i) Old Folded Mountains: All the folded mountains originating before the tertiary period come under the category of old folded mountains, e.g., the old folded mountains of Calledonian and Write us : [email protected] www.mahendras.org www.mahendraguru.com myshop.mahendras.org STUDY NOTES FOR SSC AND STATE LEVEL EXAMS Hercynian periods, such as the Aravalis, Appalachians etc. (ii) New Folded Mountains: In this category come the Alpine folded mountains of the tertiary period, e.g. the Alps, Himalayas, Rockies, Andes etc. • These are gigantic mountains characterised by glacier-capped high peaks, intense erosion, complex folding and faulting, volcanism etc. 2. Volcanic Mountains: Volcanic mountains are formed by the extrusion of lavas and pyroclastic materials, which, if continued long enough, produces gigantic volcanic piles. • The Kilimanjaro (Africa), Cotapaxi (Andes), Mount Acancagua (the highest volcanic mountain) etc., are some of examples. 3. Block Mountains • These are the result of faulting caused by tensile and compressive forces. • Examples are Vosges and Black forest mountains bordering the Rhine Rift Valley, Salt Range of Pakistan, Siera Nevada (USA) etc. • Siera Neveda mountain of California is considered to be the most extensiveblock mountain of the world. 4. Relict Mountains • When mountains, plateau, or high plains take the form of mountains by continued erosion over a long period of time they are known as Relict mountains. Examples are Aravali, Satpura, Vindhyachal in India, mountains of Scotland and Penine range of Europe. Classification of mountains on the basis of mountain building period • Pre-Cambrican Mountain e.g. Lauratian Shields, Fennos Can dies (Europe), Angora Land (Asia) Gondwanaland (Asia) etc. • Caledonian Mountain: Mountains of Scandinavia, Mountains of North America, Brazil of South America, the Aravalis, Mahadeo and Satpura ranges. • Hercynian Mountains: Mountains formed during Permian and Permocarboniferous periods e.g. Iberian peninsula, Ireland, Spanish Messeta, Rhine Massif, Bohemian Plateau, Vosges, Black forest, Tienshan, Tarim Basin. Write us : [email protected] www.mahendras.org www.mahendraguru.com myshop.mahendras.org STUDY NOTES FOR SSC AND STATE LEVEL EXAMS • Alpine mountains : Formed during the tertiary period e.g., Andes (South America), Apline Mountain systems of Europe. Atlas Mountain of North-West Africa, the Himalayas and mountains coming out of Pamir knot. Other Important Facts • Nilgiri Hills of India are an example of Block Mountain. • Ojas Del Saldo, situated in the Andes, is the highest active volcanic mountain of the world. • The Western Ghats of India is not a true mountain range. I t is, in fact, a fault scarp whose western part has been displaced and has subsided to the west. • Andes, the folded mountains of South America, is the longest (7,000 km) range in the world. • Folded Mountains are made up chiefly of the sedimentary • rocks, but their core is characterised by massive granitic intrusions. • Folded Mountains are generally found in arc sphere and they extend for greater lengths but their widths are far smaller. • Great Dividing Range of Australia is an old folded mountain. • Folded mountains are generally found along the margins of the continents either in north- south direction, such as R ockies & Andes, or in east-west D irection such as the A lps inEurope, Atlas in A frica, H imalayas, etc. PLATEAU • Plateau is an elevated tract of relatively flat land, usually limited on at least one side by a steep slope falling abruptly to lower land. • This second order relief feature covers about 33 per cent of the land surface of the globe. Types of Plateau based on Mode of Origin 1. Plateau Formed by Exogenetic Processes: a) Glacial Plateau: Garhwal Plateau, Plateau of Greenland are formed by erosion, whereas, Plateau formed by deposition are the Russian Plateau, Marg of Kashmir. b) Fluvial Plateau: Bhander Plateau of central India, Brazilian plateau c) Aeolian Platea: Loess Plateau of China, Potwar Plateau of Pakistan 2. Tectonic Plateaus a) Intermontane Plateau: Tibetan Plateau is the largest and highest plateau situated between Mt Kunlun in the north and Himalayas in the South. Bolivian Plateau in the Andes mountain range, Mexican plateau between the eastern and western Sierra Madre mountain range, are other examples. b) Piedmont Plateau: Plateau formed at the foothill zone of extensive mountains e.g. Piedmont plateau at the eastern margin of Appalachian mountain range and Patagonian Plateau in the east of Andes. c) Dome Plateau: Ozark Plateau of USA, Chhotanagpur Plateau of Jharkhand. d) Lava Plateau: Deccan Plateau, Columbia Plateau (USA). Types of Plateaus according to Geographical Location Intermontane Plateau: Tibetan Plateau, Mexican Plateau, Iranian Plateau (between Zagros and Elburz), Anatolian Plateau (between Pontic and Taurus). Border Plateau: Piedmont Plateau (USA), Patagonian Plateau (Argentina) Continental Plateau: Arabian Plateau, Peninsular Indian Plateau, Australian Plateau, South African Plateau, Mexican Plateau, etc. Coastal Plateau: Coromandel coastal upland of India. Types of Plateaus Based on Stages of Erosion 1. Young Plateau: Colorado Plateau (USA), Idaho Plateau (USA), Khandala upland (India), etc. In these plateau rivers form deep and narrow valleys through vertical erosion. 2. Mature Plateau: Ranchi Plateau, Appalachian plateau Write us : [email protected] www.mahendras.org www.mahendraguru.com myshop.mahendras.org STUDY NOTES FOR SSC AND STATE LEVEL EXAMS 3. Old Plateau: Agents of denudation erode it to their base level and the plateau appears as a featureless plain, except for some Monadnocks which are steep-sided resistant rocks surviving the onslaught of erosion. Precise examples are difficult to find. 4. Rejuvenated Plateau: These are formed due to the upliftment of an old plateau, e.g. Missouri Plateau (USA). PLAINS Plain is an extensive tract of flat land or a gently undulating terrain without prominent hills or depressions. Plains are major centres of population concentration in the world. They are categorised as : 1. Diastrophic Plains Plains are seldom formed by a single process. Diastrophic forces have played a dominant role in the evolution of the Great Plains of USA; hence they are called diastrophic plains. 2. Erosional Plains (i) River Eroded Plains: Peneplains are regarded as the end-product of normal cycle of erosion (Fluvial cycle of erosion). (ii) Glaciated Plains: Plains of the northern part of North America and Western Europe are dominated by the imprints of glacial features. The Ladakh plain of India in the east of Shyok river is also a glacialeroded plain. (iii) Wind-Eroded Plain: Wind-eroded plains of Sahara (Africa) (iv) Karst Plains: Plains of Yugoslavia (Karst region), Chitrakoot (India). 3. Depositional Plains (i) River-Deposited Plains: These include the Piedmont Alluvial Plains formed in the foothill zones (e.g. Bhabar and Terai of Ganga – Yamuna plain), flood plains formed due to deposition of fine sediments in the flood affected areas and Delta plains at the end of the river course (e.g. Ganga- Brahmaputra delta). (ii) Lacustrine Plains: Formed by the filling up of lakes with sediments. Kashmir valley is regarded as a lacustrine plain. (iii) Lava Plains: Formed of thin sheets of lava coming through fissure eruption, e.g. lava plains of Iceland, Argentina, New Zealand, etc. (iv) Wind-Deposited Plains: They include sandy desert plains and loess plains, e.g. the Thar desert plain, Sahara desert, Loess plain of China. (v) Glacially-Deposited Plains: Plains of North Germany, N.W. Russia, etc. Imphal Basin is an Write us : [email protected] www.mahendras.org www.mahendraguru.com myshop.mahendras.org STUDY NOTES FOR SSC AND STATE LEVEL EXAMS example of Lacustrine plain. Uplifted Peneplains are found in the Applachian region (USA) and Chhotanagpur region of Jharkhand (India). Exogenetic or Geomorphic Processes Major geomorphic processes include weathering, mass wasting and erosion. Weathering Weathering is the decay or breaking down of rocks under the influence of surface processes that operate in situ