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Indo Gangetic Brahmaputra Plain – northern plains of India
- Great Plains of India lies to the south of the Shissalik separated by the Himalayan Front Fault (HFF).
- It is a transitional zone between the Himalayas of the north and Peninsular India
- 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 western boarder is marked by Sulaiman and Kirthar ranges.
- On the eastern side, the plains are bordered by Purvanchal hills.
- Average elevation is about 200 m above mean sea level
Formation of the Plain
- The rivers which were previously flowing into Tethys sea deposited huge amount of sediments in the Tethys Geosyncline.
- Himalayas are formed out of these sediments which were uplifted, folded and compressed due to northern movement of Indian Plate.
- Northern movement of Indian Plate also created a trough to the south of Himalayas.
- During the initial stages of upliftment of sediments, the already existing rivers changed their course several times and they were rejuvenated each time
- Headward erosion and vertical erosion of the river valley contributed huge amount of conglomerates which were carried downslope.
- These conglomerates were deposited in the depression (Indo-Gangetic Trough or Indo-Gangetic syncline) between peninsular India and the convergent boundary
New rivers and more alluvium
- The raising of Himalayas and subsequent formation of glaciers gave rise to many new rivers.
- These rivers along with glacial erosion 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 passage of the time, the depression was completely filled with alluvium, gravel, rock debris (conglomerates) and the Tethys completely disappeared leaving behind a monotonous aggradation plain.
- Upper peninsula rivers have also contributed to the formation of plains, but to a very small extent.
- During the recent times (since few million years), depositional work of three major river systems viz., the Indus, the Ganga and the Brahmaputra have become predominant.
Division as per soil types
- It is a narrow, porous, northern most stretch of Indo-Gangetic plain.
- It is about 8-16 km wide along the foothills of the Shiwaliks.
- They show a remarkable continuity from the Indus to the Tista.
- Porosity of bhabar is unique feature, due to deposition of huge number of pebbles and rock
- The streams disappear once they reach the bhabar region because of this porosity.
- The area is not suitable for agriculture and only big trees with large roots thrive in this belt.
- 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 wild life.
- Terai is more marked in the eastern part because higher amount of rainfall.
- Most of the Terai land, especially in Punjab, Uttar Pradesh and Uttarakhand, has been turned into agricultural land which gives good crops of sugarcane, rice and wheat.
- The Bhangar is the older alluvium along the river beds forming terraces higher than the flood plain.
- It contains concretions and nodules of impure calcium carbonate known as ‘KANKAR’.
- Bhangar contains fossils of animals like rhinoceros, hippopotamus, elephants, etc.
- 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.
- It denotes an elevated piece of land situated along the banks of the Ganga river especially in the upper Ganga-Yamuna Doab.
- This has been formed due to accumulation of wind–blown sands during the hot dry months of the year
- 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 flood almost every year.
- This makes them the most fertile soils of Ganges.
- In Punjab, the Khadar rich flood plains are locally known as Betlands or Bets
Reh or Kollar
- Reh or Kollar comprises saline efflorescence of drier areas in Haryana.
- Reh areas have spread in recent times with increase in irrigation (capillary action brings salts to the surface).
West to East Division
- Sindh Plain
- Rajasthan Plain
- Punjab Plain
- Ganga Plain
- Upper Ganga plain
- Middle Ganga plain
- Lower Ganga plain
- Ganga – Brahmaputra Delta
- Brahmaputra Plain
- Mainly formed of Bhangar Plains by Indus and its tributaries
- Dhors is long narrow depressions which are the remnants of the course of former rivers.
- Dhand is alkaline lakes on some dhors.
- Occupied by Thar or the Great Indian Desert.
- This plain is an wave like plain whose average elevation is about 325 m
- The desert region is called Marusthali and forms a greater part of the Marwar plain.
- It has a few outcrops of gneisses, schists and granites which proves that geologically it is a part of the Peninsular Plateau. It is only at the surface that it looks like an aggradation plain.
- In general, the eastern part of the Marusthali is rocky while its western part is covered by shifting sand dunes
- Eastern part of the Thar Desert up to the Aravali Range is a semi-arid plain known as Rajasthan Bagar.
- It is drained by a number of short seasonal streams originating from the Aravali and supports agriculture in some patches of fertile tracts.
- Luni is an important seasonal stream
- The tract north of the Luni is known as thali or sandy plain.
- North of the Luni, there is inland drainage having several saline lakes. Sambhar, Didwana, Degana, Kuchaman, etc. are some of the important lakes.
- The largest is the Sambhar lake near Jaipur.
- This plain is formed by five important rivers of Indus system.
- The plain is primarily made up of ‘doabs’ —the land between two rivers.
- Punjab means “The Land of Five Rivers” referring to the following rivers: the Jhelum, Chenab, Ravi, Sutlej, and Beas.
- The eastern boundary of Punjab Haryana plain is marked by subsurface Delhi-Aravali ridge.
- Northern part of this plain near Shiwalik hills has been intensively eroded by numerous streams called Chos landform. This has led to enormous gullying (Hoshiarpur ,Punjub)
- The only river between the Yamuna and the Satluj is the Ghaggar which is considered to be the present day Successor of the legendary Saraswati River
- The Punjab-Haryana Plains may be divided into
- Bari Doab between the Beas and Ravi
- Bist Doab between the Beas and Satluj
- Malwa Plain the central part of the region
- Hariyana–Bhiwani Bagar in the southern and south-eastern parts of the region.
- Ganga PIain lie between the Yamuna catchment in the west to the Bangladesh border in the east
- The Ganga along with its large number of tributaries originating in the Himalayans
- Those rives have brought large quantities of alluvium from the mountains and deposited it here to build this extensive plain.
- The peninsular rivers such as Chambal, Betwa, Ken, Son, etc. joining the Ganga river system
- General slope of the entire plain is to the east and south east.
- Rivers flow sluggishly in the lower sections of Ganges as a result of which the area is marked by local prominences such as levees, bluffs, oxbow lakes, marshes, ravines, etc.
- Almost all the rivers keep on shifting their courses making this area prone to frequent floods.
- The Kosi river is very notorious in this respect. It has long been called the ‘Sorrow of Bihar’.
Upper Ganga Plain
- It includes the Ganga–Yatnuna doab, Rohilkhand Division and parts of the Agra Division.
- The catchment area of the Yamuna river makes its western boundary
- In addition to Ganga and the Yamuna, it is traversed by the Kali and Sharda rivers.
- A unique feature of the Upper Ganga Plain is the presence of Bhur
Middle Ganga Plain
- It includes central and eastern Uttar Pradesh, and the Bihar Plains up to Muzaffarpur and Patna.
- It has thick alluvial deposits with less Kankar formation.
Lower Ganga Plain
- It extends from Patna in the west, the foot of Darjeeling Himalaya in the north to the Bay of Bengal in the south
- It is bordered by Assam and Bangladesh in the cast and the Chotanagpur Plateau in the west.
- In the lower part of the Lower Ganga Plain is Sundarban Delta.
- The plain has a monotonous surface.
- The Lower Ganga Plain has been formed by the down warping of a part of the Peninsular India between Rajmahal Hills and the Meghalaya Plateau
- It formed by subsequent sedimentation by the Ganga and the Brahmaputra rivers
- It lying to the east of the Chotanagpur Plateau, it is a part of the Lower Gangetic Plains.
- Drained by the Damodar and Subarnarekha
- It covered by the lateritic-alluvium soils
- Soil erosion is the main problem of the Rahr plain
- Rice, maize and pulses are the main crops here
- This is the largest delta in the world.
- The Ganga river divides itself into several channels in the delta area.
- The seaward face of the delta is studded with a large number of estuaries, mud flats, mangrove swamps, sandbanks, islands and forelands.
- Large part of the coastal delta is covered by tidal forests
- The largest mangrove swamp in the world
- Sundarhans gets its name from the Sundari tree (Heritiera fomes) which grows well in marshland
- Mangrove forest covers an area of about 10,000 km2
- In West Bengal, they extend over 4,260 km2 across South 24 and North 24 Pargana district
- It is a UNESCO World Heritage site inscribed in 1987
- In 2019, it has been designated as a Ramsar site
- It is considered as a World Network of Biosphere Reserve from 2001.
- This is also known as Assam Valley as most of the Brahmaputra valley is situated in Assam.
- Its western boundary is formed by the Indo-Bangladesh border as well as the boundary of the lower Ganga Plain.
- Its eastern boundary is formed by Purvanchal hills.
- The innumerable tributaries of the Brahmaputra river coming from the north form a number of alluvial fans.
- Tributaries branch out in many channels giving birth to river meandering leading to formation of bill and ox-bow lakes.
- There are large marshy tracts in this area.
- Manas, Kaziranga, Orang National Parks are located in this area.
- The alluvial fans formed by the coarse alluvial debris have led to the formation of terai or semi-terai conditions with dense forest
- Brahmaputra have numerous islands.
- Majuli (area 930 sq km) is the largest river island of the world and country’s first river island district.
Significance of the Plain
- This one fourth of the land of the country hosts half of the Indian population.
- Fertile alluvial soils, flat surface, slow moving perennial rivers and favorable climate facilitate intense agricultural activity.
- The extensive use of irrigation has made Punjab, Haryana and western part of Uttar Pradesh the granary of India (Prairies are called the granaries of the world).
- The entire plain except the Thar Desert, has a close network of roads and railways
- It has led to large scale industrialization and urbanization.
- There are many religious places along the banks of the sacred rivers like the Ganga and the Yamuna
- Those are very dear to Hindus.
- Here flourished the religions of Budha and Mahavira and movements of Bhakti and Sufism