Formation & Division of Plains UPSC Notes | EduRev

Geography for UPSC CSE

UPSC : Formation & Division of Plains UPSC Notes | EduRev

The document Formation & Division of Plains UPSC Notes | EduRev is a part of the UPSC Course Geography for UPSC CSE.
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The Great North Indian Plain

The Indo-Gangetic- Brahmputra Plain, also known as the Indus-Ganga Plain and the North Indian River Plain, is a 2.5-million km(630-million-acre) fertile plain encompassing northern regions of the Indian subcontinent, including most of northern and eastern India.

Formation & Division of Plains UPSC Notes | EduRev

  • It also encompasses the eastern parts of Pakistan, virtually all of Bangladesh, and the southern plains of Nepal
  • The Great North Indian plains are a homogeneous surface with an invisible slope.
  • These are alluvial fertile plains formed by the deposition process of the Himalayan Rivers. 
  • Along with the Himalayan Rivers, the Vindhyan Rivers are also having a prominent role in making the land fertile. 
  • It deposits a large number of sediments along the foothills. The sedimentary deposition makes this area fertile and the breadbasket of the country and it plays a crucial role in socio-economic-cultural spheres.

Formation of Indo – Gangetic – Brahmaputra Plain

  • The formation of the Indo-Gangetic plain is closely related to the formation of Himalayas.

Trough Formation

  • The rivers which were previously flowing into Tethys sea (Before Indian Plate collided with Eurasian Plate – continental drift, plate tectonics) deposited huge amount of sediments in the Tethys Geosyncline. [Geosyncline – a massive depression]
  • The Himalayas are formed out of these sediments, which were uplifted, folded, and compressed due to the northern Indian Plate movement.
  • The northern movement of the Indian Plate also created a trough to the south of Himalayas.

Formation & Division of Plains UPSC Notes | EduRev

Depositional Activity

  • During the initial stages of upliftment of sediments, the already existing rivers changed their course several times, and they were rejuvenated each time (perpetual youth stage of rivers {Fluvial Landforms}).
  • The rejuvenation is associated with intense headward and vertical downcutting of the soft strata overlying the harder rock stratum.
  • Headward erosion and vertical erosion of the river valley in the initial stages, lateral erosion in later stages contributed a massive amount of conglomerates (detritus)(rock debris, silt, clay etc.) which were carried downslope.
  • [Head ward erosion == Erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the streamflow, and so causes the stream channel to lengthen]
  • These conglomerates were deposited in the depression (Indo-Gangetic Trough or Indo-Gangetic syncline) (the base of the geosyncline is hard crystalline rock) between peninsular India and the convergent boundary (the region of present day Himalayas).
    Try yourself:A Geosyncline is a
    View Solution

New Rivers and more Alluvium

  • The raising of the Himalayas and the subsequent formation of glaciers gave rise to many new rivers. These rivers, along with glacial erosion {Glacial Landforms}, supplied more alluvium which intensified the filling of the depression.
  • With the accumulation of more and more sediments (conglomerates), the Tethys sea started receding.
  • With the passage of time, the depression was filled with alluvium, gravel, rock debris (conglomerates) and the Tethys completely disappeared, leaving behind a monotonous aggradational plain.
  • monotonous = featureless topography; 
  • aggradational plain =plain formed due to depositional activity. 
  • Indo-Gangetic plain is a monotonous aggradational plain formed due to fluvial depositions.
  • Upper peninsular rivers have also contributed to the formation of plains, but a minimal extent.
  • During recent times (since a few million years), depositional work of three major river systems viz., the Indus, the Ganga, and the Brahmaputra have become predominant.
  • Hence this arcuate (curved) plain is also known as Indo-Gangetic-Brahmaputra Plain.

Formation & Division of Plains UPSC Notes | EduRev

Features of Indo – Gangetic – Brahmaputra Plain

  • Indo-Gangetic-Brahmaputra Plain is the largest alluvial tract of the world.
  • It stretches for about 3,200 km from the mouth of the Indus to the mouth of the Ganga. Indian sector of the plain accounts for 2,400 km.
  • The Shiwaliks well marks the northern boundary, and the southern boundary is a wavy irregular line along the north edge of Peninsular India.
  • Sulaiman and Kirthar ranges mark the western border. On the eastern side, the plains are bordered by Purvanchal hills.
  • The width of the plain varies from region to region. It is widest in the west where it stretches for about 500 km. Its width decreases in the east.
  • The thickness of the alluvium deposits also varies from place to place. The maximum depth of the alluvium up to the basement rocks is about 6,100 m (not uniform and varies significantly from place to place).
  • The cones or alluvial fans of Kosi in the north and those of Son in the south exhibit greater alluvial thickness while the intra-cone areas have relatively shallower deposits.
  • Extreme horizontality of this monotonous plain is its chief characteristic.
  • Its average elevation is about 200 m above mean sea level. The highest peak is 291 m above indicate sea level near Ambala (This elevation forms the drainage divide or watershed between the Indus system and Ganga system).
  • Its average gradient from Saharanpur to Kolkata is only 20 cm per km, and it decreases to 15 cm per km from Varanasi to the Ganga delta.

Try yourself:Eastern Side of the Indo - Gangetic- Brahmaputra plain is bordered by
View Solution

Geomorphological Features

The Great North Indian plain is divided into the following subdivisions based on relief features:

  1. The Bhabar Plains
  2. The Terai Tract
  3. The Bhangar
  4. The Khadar
  5. Reh or Kollar

Formation & Division of Plains UPSC Notes | EduRev

1. The Bhabar Plains

  • It is a narrow, porous, northernmost stretch of Indo-Gangetic plain.
  • It is about 8-16 km wide running in an east-west direction along the foothills (alluvial fans) of the Shivalik.
  • They show a remarkable continuity from the Indus to the Tista.
  • Rivers descending from the Himalayas deposit their load along the foothills in the form of alluvial fans.
  • These alluvial fans have merged to build up the bhabar belt.
  • The porosity of bhabar is a unique feature.
  • The porosity is due to the deposition of many pebbles and rock debris across the alluvial fans.
  • The streams disappear once they reach the bhabar region because of this porosity.
  • Therefore, the area is marked by dry river courses except in the rainy season.
  • The Bhabar belt is comparatively narrow in the east and extensive in the western and north-western hilly regions.
  • The area is not suitable for agriculture, and only big trees with large roots thrive in this belt.

2. The Terai Tract

  • Terai is an ill-drained, damp (marshy) and thickly forested narrow tract to the south of Bhabar running parallel to it.
  • The Terai is about15-30 km wide.
  • The underground streams of the Bhabar belt re-emerge in this belt.
  • This thickly forested region provides shelter to a variety of wildlife. [Jim Corbett National Park in Uttarakhand and Kaziranga National Park in Assam lie in Terai region]
  • The Terai is more marked in the eastern part than in the west because the eastern parts receive a comparatively higher amount of rainfall.
  • Most of the Terai land, especially in Punjab, Uttar Pradesh and Uttarakhand, has been turned into agricultural land that gives good sugarcane, rice, and wheat crops.

3. The Bhangar

  • The Bhangar is the older alluvium along the river beds forming terraces higher than the flood plain.
  • The terraces are often impregnated with calcareous concretions known as ‘KANKAR’.
  • The Barind plains’ in the deltaic region of Bengal and the ‘bhur formations’ in the middle Ganga and Yamuna doab are regional variations of Bhangar.
  • [Bhur denotes an elevated piece of land situated along the Ganga river banks, especially in the upper Ganga-Yamuna Doab. This has been formed due to the accumulation of wind-blown sands during the hot, dry months of the year]
  • Bhangar contains fossils of animals like rhinoceros, hippopotamus, elephants, etc.

4. The Khadar

  • The Khadar is composed of newer alluvium and forms the flood plains along the river banks.
  • A new layer of alluvium is deposited by river floods almost every year.
  • This makes them the most fertile soils of the Ganges.

5. Reh or Kollar

  • Reh or Kollar comprises saline efflorescences of drier areas in Haryana.
  • Reh areas have spread in recent times with an increase in irrigation (capillary action brings salts to the surface).



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