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Mountain Building Mountains are significant relief features of the second order on the earth’s surface. A mountain may have several forms: 1. Mountain ridge- system of long, narrow & high hills. Slope of one side of ridge is steep other side slope is moderate 2. Mountain range- system of mountains & hills having several ridges, peaks, summits and valleys 3. Mountain system- It consists of different mountain ranges of the same period. 4. Cordillera- It consists of several mountain groups and systems. Classification of mountains Based on height Low mountains Rough mountains Rugged mountains High mountains Based on location Continental mountains Oceanic mountains Based on mode of origin Relict mountains Tectonic mountains On the basis of height On the basis of location 1. Continental mountains1. Low mountainsexamples- Applachians, height ranges western & eastern Ghats of between 700- 1000 m. India. 2. Rough mountainsheight- 1000- 1500 m. 3. Rugged mountainsheight- 1500- 2000 m. 4. High mountainsheight- above 2000m. 2. Oceanic mountainsmountains below the water surface are oceanic mountains. On the basis of mode of origin 1. Tectonic mountainscaused due to tectonic forces like tensile and compressional forces 2. Relict mountainsexamples- Vindhayachal, Aravallis, Satpura etc. Plateaus - Plateaus are significant relief features of the second order. - They cover around 33 % of the surface area of the globe. - Plateau may be defined as that upland which has atleast one side of very steep slope and the upper part is extensively and almost flat. - Examples- Ranchi plateau, Shillong plateau etc. Characteristics of a plateau • From locational point of view, plateaux vary from one place to another place. Some plateaux are surrounded by hills & mountains, some are bordered by hills & mountains on one side while they are bordered by plains or coastal areas on the other side. • Some plateaux are very extensive in areal context. • • Plateaux have flat and rolling top surfaces. • Generally, the slopes of the side walls are very steep but the top surfaces are more or less flat. Origin and evolution of Plateaux Plateaux are originated in a number of ways:• Due to downwarping of surrounded areas. • Due to upwarping of some portion of an extensive landmass by a few hundred metres in relation to surrounding ground surface. • Due to deposition of thick covers of basaltic lavas. • Due to the transformation of extensive mountains into low uplands having extensive rugged surfaces due to prolonged denudation. Classification of Plateaux On the basis of mode of origin According to geographical situation coastal Piedmont Intermontane Continental According to size & shape Dome shaped Dissected Step like Flat topped Rejuvinated Fluvial Glacial Aeolian Intermontane Piedmont Continental According to stage volcanic of erosion Young Mature Old Plains • Plains are flat areas with low height. • Plains may be above or below sea level but they cannot be higher than the surrounding regions. • They are characterized by almost flat surface but it also becomes undulating because of erosion. • Plains are dominated by level to gentle slopes. Origin and development of plains • Most of the plains have been originated due to upliftment of submerged landmasses due to diastrophic movements. • Plains are formed due to filling of depressions with sediments, which are created in front of the mountains during the process of orogenesis. • Extensive plateaux after prolonged denudation become plains. • Deposition of enormous volume of lavas over extensive area gives birth to volcanic plains. Classification of Plains According to structural characteristics According to mode of origin Diastrophic Flat volcanic Undulating Rolling Erosional Dissected Depositional According to location Inland Coastal