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Here is a compilation of essays on ‘Plateaus’ for class 6, 7, 8, 9, 10. Find paragraphs, long and short essays on ‘Plateaus’ especially written for school students.
Essay on Plateaus
Essay # 1. Origin of Plateaus:
Plateaux are originated in a number of ways as follows:
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(1) Due to down-warping of surrounding areas. For example, if the southern part of the Ganga plain is down-warped by a few hundred metres but the northern part remains stable, then the remaining plain area associated with the Himalaya would become a plateau.
(2) Due to upwarping of some portion of an extensive land mass by a few hundred metres in relation to surrounding ground surface e.g. Western Patlands of Ranchi and Palamau.
(3) Due to deposition of thick covers of basaltic lavas e.g. Columbian plateau (USA), Mahabaleshwar plateau, Panchgani plateau etc.
(4) Sometimes, the adjoining areas of mountains are not folded but are raised during the process of mountain building. Such unfolded but upwarped regions become plateau e.g. Cumberland Plateau to the west of Applachian Mountains. It may be pointed out that perfect horizontal of coal beds has been preserved in Cumberland Plateau.
(5) The marginal sediments of geosynclines are folded into parallel marginal ranges and the middle portion of the geosynclines remains unaffected by compressive forces. Such unfolded middle portion of geosynclines bordered by marginal mountain ranges becomes median mass which may assume the form of a plateau (it may also be a plain) e.g. Tibetan plateau between Kunlun-Tienshan and the Himalayas, Iranian plateau between Zagros and Elburz mountains, Anatolian plateau (in Turkey) between Pantic and Taurus mountains etc.
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(6)Some plateaux are also formed when extensive mountains are transformed into low uplands having extensive rugged surfaces due to prolonged denudation. Several examples of such mountain-cum-plateau may be seen in the Applachian Mountain.
(7) Thick deposits of loose materials by wind also form plateaux e.g. Loess plateau of China.
Essay # 2. Meaning of Plateaus:
Plateaux are significant relief features of the second order as these cover about 33 per cent of the surface area of the globe (plains, hills and mountains cover about 41, 14 and 12 per cent of the total surface area of the globe respectively). According to Finch and Trewartha “tabular uplands having a relief of more than 500 feet may be arbitrarily defined as plateau”.
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Plateau may be defined as that upland which has atleast one side of very steep slope standing well above the neighbouring surface and the upper part is extensive and almost flat, examples, Ranchi plateau, Hazaribagh plateau, Shillong plateau etc. There is wide range of variation in the heights of plateaux, e.g. Applachian plateau rises for 1000 m AMSL, Colorado plateau has a mean height of 2500 m AMSL and Tibetan plateau is the highest (5,000 m AMSL) plateau in the world.
Essay # 3. Characteristics of Plateaus:
On an average, plateaux are extensive upland areas characterized by flat and rough top surface, steep side walls which rise above the neighbouring ground surface at least for 300 m. “The surfaces of plateau may be plain like in quality, very flat, rolling or hilly, or they may be so dissected by streams and glaciers that it is difficult to recognise their original plateau characteristics”.
From locational point of view plateaux vary from one place to another place. Some plateaux are surrounded by hills and mountains (e.g. Tibetan plateau), some plateaux are bordered by hills and mountains on one side while they are bordered by plains or coastal areas on the other side e.g., piedmont plateau of the USA (it is bordered by middle Applachian mountains in the west and Atlantic coastal plains in the east), Cumberland and Alleghany plateaux in the USA (surround by Applachian mountains in the east and Mississippi plains in the west), Iranian and Anatolian plateaux and Colorado plateau of the USA are also bordered by mountain ranges.
Some plateaux are very extensive in areal context e.g. Deccan plateau of India, Siberian plateau, Arabian plateau etc. The most characteristic features of plateaux are their flat and rolling top surfaces. Generally, the slopes of the side walls are very steep but the top surfaces, except minor reliefs, are more or less flat. Ranchi plateau abruptly rises from the Damodar valley and the northern side-walls are about 300m high from the Damodar plain (300m AMSL).
The flat top surface of the Ranchi plateau is characterized by scattered hills and batholithic granite-gneissic domes which rise upto 50 to 100m from the ground surface. Plateau surface is also dotted with hill ranges and river valleys. The rivers while descending from the plateau form long, narrow and deep valleys (e.g., gorges and canyons).
For example, all the major rivers while descending through Rawa plateau (in Madhya Pradesh) and draining northward to meet the Yamuna or the Ganga rivers have entrenched deep valleys e.g. Chachai gorge of Bihar river (127 m deep). Kevati gorge of Mahana river (98m deep), Odda gorge (145m deep) on Odda river (in Rewa district, M.P.) etc. The Colorado plateau in Arizona State (USA) attains the height of 2100 m AMSL. Its top surface has been deeply entrenched by Colorado River. The world famous Colorado gorge and canyon is 1000m deep.
From the stand point of surficial materials plateaux also register wide range of variations. Some plateaux have thick covers of basaltic lavas e.g. Deccan plateaux in an area of 7,74,000 km2 (e.g. Mahabaleshwar plateau and Panchagani plateau in Maharashtra have thick covers of basaltic lavas topped by massive laterite covers).
Some plateaux are composed entirely of sedimentary rocks e.g. Rewa plateau (composed of sandstones, shales and limestones), Bhander plateau having sandstone capping, Rohtas plateau (Bihar) having sandstone capping etc. Some plateaux are so dissected by the network of streams that they are segmented into numerous parts e.g. patlands of Ranchi and Palamau uplands (in Jharkhand) have been segmented by the North Koel river and its tributaries into several flat-topped mesas and buttes having steep side slopes from all sides. Such lava-capped mesas are locally called ‘Patlands’, examples, Netarhat Pat, Jamira Pat, Khamar Pat, Rudni Pat, Raldami Pat, Bagru Pat (having bauxite capping) etc.
Essay # 4. Classification of Plateaus:
1. According to mode of origin:
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(A) Simple Plateaux:
(1) Plateaux formed by exogenetic processes.
(i) Glacial plateau e.g. Garhwal plateau.
(ii) Aeolian plateau e.g. Potawar plateau, Loess plateau.
(B) Compound Plateaux:
(2) Plateaux formed by endogenetic processes.
(i) Intermontane plateau e.g. Tibetan plateau.
(ii) Piedmont plateau e.g. Applachian Piedmont Plateau.
(iii) Dome plateau e.g. Ozark Massif (USA), Chotanagpur plateau (Jharkhand, India).
(iv) Lava plateaux, examples, Columbia plateau (USA), Mahabaleshwar plateau, Panchagni tableland etc.
2. Classification according to geographical situation:
(1) Intermontane plateaux, examples: Tibetan plateau, Bolivian plateau, Peru plateau, Columbian plateau, Mexican plateau, Iranian plateau, Anatolian plateau etc.
(2) Piedmont plateaux, examples: Applachian Piedmont plateau, Patagonian plateau etc.
(3) Continental plateaux, examples: Deccan plateau of India, Ranchi plateau, Shillong plateau, Columbian plateau (USA), Mexican plateau, Tibetan plateau etc.
(4) Coastal plateaux, example: Coromandal Coastal upland of India.
3. Classification on the basis of size and shape:
(i) Dome-shaped plateau, example: Chotangpur plateau (in Jharkhand).
(ii) Dissected plateau, example: Deccan plateau of India.
(iii) Step-like plateau, example: Kaimur plateau consisting of (from west to east, height decreases eastward) Panna plateau, Bhander plateau, Rewa plateau and Rohtas plateau.
(iv) Flat-topped plateau, examples: Tibet plateau, Bhander plateau (M.P.), Rewa plateau etc.
(v) Rejuvenated peneplain plateau, example: Missouri plateau of USA, Patlands of Ranchi and Palamau (Jharkhand).
4. Classification on the basis of surface configuration:
(1) Uneven plateau, example: Applachian plateau
(2) Tableland plateau, example: Mahabaleshwar plateau, Panchgani tableland (Maharashtra)
5. Classification on the basis of climate:
(1) Desert or arid plateau, example: Arabian plateau
(2) Humid plateau, example: Shillong plateau, Mahabaleshwar plateau, Assam plateau etc.
(3) Ice-capped plateau, example: Greenland plateau
6. Classification on the basis of stage of erosion:
(1) Young plateau, examples: Idaho plateau (USA), Colorado plateau (USA), Mahabaleshwar plateau, Khandala upland (Maharashtra).
(2) Mature plateau, examples: Ranchi plateau, Hazaribagh plateau (all in Jharkhand): Applachian plateau.
(3) Old plateau.
(4) Rejuvenated plateau, example: Missouri plateau (USA).
7. On the basis of mode of origin:
(1) Glacial Plateau:
It may be pointed out that glacial plateau does not mean a plateau formed by the glaciers rather it means a plateau modified and transformed by glacial actions because all the plateaux, in one way or the other, are the result of endogenetic forces and related tectonic events.
When mountains are greatly modified and transformed by glacial erosion, they are lowered in height and their sharp reliefs are rounded to such an extent that they become the example of a plateau. Glaciers have formed numerous plateaux through their erosional work on Greenland and Antarctica.
According to Chhibber Garhwal plateau of India has been formed due to glacial actions. The deposition of glacial moraines also forms low plateaux. Such plateaux have been formed in Germany because of morainic deposits during Pleistocene Ice Age. ‘Marg’ of Kashmir is supposed to have been formed of glacial moraines.
(2) Fluvial Plateaux:
Fluvial plateaux are formed due to continuous deposits of fluvial sediments brought by the rivers. The sediments are gradually consolidated and stratified into sedimentary rocks of great thickness. These sedimentaries are raised upward due to earth movements relative to surrounding regions and thus upland plateau with extensive flat top surface is formed.
Extensive Kaimur plateau consisting of Panna plateau, Bhander plateau, Rewa plateau, Rohtas plateau etc. is the best example of fluvial plateau. This extensive plateau region consists of a series of descending plateaux beginning from Panna plateau in the west (M.P.) and ending into Rohtas plateau (Bihar) in the east.
These plateaux consist of sedimentary rocks (sandstones, shales and limestones) which were deposited in Vindhyan Sea during pre-Cambrian period and were subsequently raised by earth movements. The rocks of these plateaux belong to Vindhyan formations.
(3) Aeolian Plateau:
Aeolian plateau is formed because of deposition of fine sediments brought by winds. Enormous volumes of sediments are consolidated in due course of time and plateau is formed. Potawar plateau of Pakistan and Loess plateau of China are considered to have been formed due to deposition of fine sediments by wind.
Most extensive, highest and most complex plateaux are originated through endogenetic forces coming from deep within the earth. The plateaux formed by horizontal and vertical movements caused by endogenetic forces are called diastrophic plateau which include intemontane plateaux, piedmont plateau, continental plateaux and dome-shaped plateau. Diastrophic plateaux, in fact, are true plateaux. They are also called tectonic plateaux.
(4) Internontane Plateaux:
Internontane plateaux are, in fact, the highest and most extensive plateaux of the globe. These are called intermontane because they are surrounded by hills and mountains almost from all sides. Intermontane plateaux are originated together with the origin of folded mountains.
Generally, intermontane plateaux are formed due to upwarping of middle portion of the geosynclines known as median mass, after the formation of mountain ranges along both the margins of the geosynclines. Tibetan plateau is the best example of intermontane plateaux. Bolivian plateau, Peruvian plateau, Columbian plateau, Mexican plateau etc. are other significant examples of intermontane plateaux.
Tibetan plateau, having an average height of 5,000 m (16,000 feet), is the highest plateau of the world. At some places the plateau rises upto 6,000 m AMSL. As regards areal extent, Tibetan plateau is also the most extensive plateau of the world as it covers an area of about 20,64,000 km2 (8,00,000 square miles).
Tibetan plateau, surrounded by Kunlun Mountains in the north, the Himalayas in the south, Kunlun-Himalayas in the west and Chinese mountains in the east, is the best example of a median mass (unfolded upland).
From the stand point of reliefs, Tibetan plateau is divided into 4 regions e.g.:
(i) The northern region is a mixture of low hill ranges, valleys and plains with an average height of 4,800 m (16,000 feet). There are several enclosed salt lakes which are spread over an area of 2,580 km2,
(ii) The southern plateau region is the source area of the Indus and the Brahmaputra rivers,
(iii) The eastern plateau region is comparatively lower than the northern and the southern plateau regions. This region has the sources of Yellow river (Hwang Ho), Yangtze river, Salween river, Meeking river etc.
(iv) North-eastern plateau region consists of several enclosed basins, playa lakes and saline lakes (salt lakes). Tsaidan Swamps are the characteristic features of this region.
Mexican plateau, another fine example of an intermontane plateau, is surrounded by Sierra Madre Occidental range in the west and Sierra Madre Oriental mountain range in the east. The plateau slopes northward as its average height near Mexico City is about 2250m (7410 feet) while it decreases to 1216m (4000 feet) near its international border with the USA.
The whole plateau is covered with valleys, low hills, playa lakes, salt lakes etc. The southern part of the plateau is characterized by several volcanic mountains. Tectonically and seismically the plateau is very much sensitive and unstable. The devastating Mexico earthquake of September, 1985 proves the validity of this concept.
The plateaux of Bolivia and Peru (South America) are also surrounded by mountain ranges of tertiary period. The Peruvian-Bolivian plateuax are surrounded by Cordillera Central Ranges and Cordillera Occidental Ranges in the east and west respectively. These plateaux, exhibiting an example of median mass, were originated together with the origin of the Andes Mountains during tertiary period.
The average height of these plateaux from sea-level is 3,648 m (12,000 feet). Some parts of the plateaux are plains while some parts are hilly regions. Lake Titicaca is fresh water lake which is 264 km long and 96 km wide and 12,370 feet (3761 m) high (AMSL).
(5) Piedmont Plateau:
Plateau formed at the foothill zone of extensive mountains is called piedmont plateau, which is surrounded by mountain range on one side while by plain topography or coastal plain on the other side. The side of the plateau facing the plains is of steep slope and thus forms an escarprment.
Piedmont plateaux are also formed due to upliftment during the origin of mountains. The piedmont plateau representating the eastern margins of the Applachian Mountains (USA) and Patagonian plateau of South America are the representatives of piedmont plateaux.
The Applachian piedmont plateau abruptly terminates into Atlantic coastal plains. The sudden break in slope along the junction of the piedmont and the coastal plains makes sudden decrease in the channel gradients of the Atlantic-bound rivers of the Applachians, with the result all the rivers which originate in the Applachians and descend through the escarpment of the piedmont plateau and enter the coastal plains to drain into the Atlantic Ocean, make stupendous waterfalls of varying magnitudes.
There is a world famous fall line along the eastern margin of the piedmont plateau from Alabama in the south-west to New England in the northeast. This fall-line is associated with numerous waterfalls, the most of which have been tapped for the generation of hydroelectricity which has accelerated the place of industrial development along the fall- line.
(6) Dome Shaped Plateaux:
Dome shaped plateaux are formed when the landmass is uplifted in such a manner that the middle portion is upwarped and the sides are rounded. Dome- shaped plateaux are generally formed due to endogenetic forces mainly during volcanic activities. In fact, the hatholithic and laccolithic intrusions of magmas beneath the crustal rocks cause large-scale doming of the ground surface which rises upto several hundred metres from the surrounding neighbouring ground surface.
Chotanagpur plateau of Bihar is quoted as a typical example of domal plateau because it is studded with numerous batholithic domes which were intruded in the Dharwarian sedimentaries during Archaean period. Prolonged denudation has removed the superincumbent Dharwarian covers and these batholithic domes have been exposed on the surface.
Ozark plateau (USA) is considered to be the best example of dome-shaped plateau. Ozark was formed due to upliftment of ground surface caused by Applachian Revolution (Applachain mountain building) during Permain period. This plateau was vigorously denuded and hence it was transformed into a peneplain before Tertiary period. It was again uplifted and was again transformed into second peneplain due to prolonged denudation by the end of Tertiary period.
It is apparent that Ozark plateau has passed through two phases of cycle of erosion and peneplanation.
Presently, Ozark Plateau consists of three separated plateaux e.g.:
(i) Salem plateau,
(ii) Springfield plateau and
(iii) Boston plateau.
The Ozark Plateau, has given birth to radial drainage pattern. The sides of the plateau have been deeply entrenched by the radiating streams.
(7) Continental Plateaux:
Continental plateaux are very extensive plateaux and are generally away from mountainous areas but are surrounded by coastal plains. Sometimes, these plateaux are bordered by mountains on one or two sides. Deccan plateau of Peninsular India is a typical example of such plateau.
Deccan plateau, covering an area of hundreds of thousands of square kilometres, is one of the oldest plateaux of the world. The plateau composed of different rocks of Dharwar, Cuddapah, Vindhyan and Gondwana formations has been widely dissected and is characterized by elongated hill ranges. The plateau is bordered by the Western Ghats in the west and by the Eastern Ghats in the east.
The plateau is surrounded by the hill ranges of the Aravallis, Vindhyachal, Parasnath and Rajmahal, Mahadeo, Maikal, Kaimurs,Sahyadri, Ajanta, Nilgiri.Nallamalai, Nimgiri etc. Hill ranges are the prominent reliefs of the plateau. Rivers have dissected and segmented the plateau into several independent plateaux. Arabian plateau, Australian plateau, South African plateau etc. are other examples of continental plateaux. Antarctica and Greenland may be considered as the examples of new continental plateaux.
(8) Volcanic Plateaux:
Volcanic plateaux are those plateaux which are formed due to accumulation of thick layers of basaltic lavas. Lava plateau was formed over an area of 7,74,000 km2 (3,00,000 square miles) in the Peninsular India due to accumulation of enormous volume of basaltic lavas erupted during Cretaceous period.
The examples of volcanic plateaux formed due to deposition of basaltic lavas coming up through fissure flows are also found in New Zealand, South Africa, northern and southern Argentina, Brazil, western USA (Columbian plateau), France, Siberia etc. The Columbian plateau of the USA is the best example of lava plateaux in the world. This plateau is surrounded by the Rockies in the east, by Cascade mountains in the west, by Basin and Range Province in the south and by the plateau of British Columbia (Canada) in the north.
Columbian plateau may also be accommodated in the group of intermontane plateaux because it is surrounded by mountains from three sides. The plateau covers an area of 258,000 km2 (1,00,000 square miles) wherein the thickness of basaltic lavas ranges between 608m to 1520m (200 to 5000 feet).
Columbia River and its tributaries have dissected the plateau to great extent. It is believed that about 300m thick basaltic lavas have already been eroded away by fluvial processes. The presence of 20 layers of lava in the Columbian plateau denotes the fact that there were 20 episodes of lava eruptions.
8. Classification on the basis of cycle of erosion:
A.K. Lobeck has divided the plateaux on the basis of stages of cycle of erosion into 3 types e.g.:
(i) Young plateau,
(ii) Mature plateau and
(iii) Old plateau.
A fourth type, rejuvenated plateau, may also be added to this group.
Young plateaux are characterized by almost horizontal beds of rocks. Though the rivers are few but they form deep and narrow valleys through vertical erosion. Such young plateaux are generally bordered by escarpments. Colorado plateau is a fine example of young plateaux where Colarado River has dug out a stupendous world-famous canyon, known as Grand Canyon, which stretches for a distance of 200 km with remarkable depth of 1600m (1.6 km).
Mature plateaux are formed when they are so greatly dissected that their surfaces become highly corrugated, undulating and uneven and the surface is dominated by pointed peaks. It may be pointed out that these pointed, sharp and angular peaks are maintained only in arid and semi-arid regions. These are greatly rounded in the warm and moist regions.
Old plateaux are formed due to prolonged erosion of mature plateau. The peaks are so denuded that they are eliminated and the plateaux are transformed into peneplains. The mesas and buttes scattered over the plateau surface are the characteristic relief features. Rejuvenated plateaus are formed due to upliftment of an old plateau. Missouri plateau of the USA is an example of rejuvenated plateau.