Assam Geography GK

assam geography gk

   Assam, the heart of North-East, is located in the tropical latitudes (24.3°N and 28°N) and easterm longitudes (89.5°E and 96.1°E) and is the most populous state in North-East India. It has an area of 78,438 sq km representing 2.39 percent of the total area of the country and a population of 31,205,576 (2011) accounting for 2.59 percent of the total national population. Assam has a total of 33 districts (Table 1), which supports a large number of populations. It is surrounded by hills and mountains on its three sides of north, east and south and to the west it merges with West Bengal and Bangladesh plains. 

    The major rivers of assam  Brahmaputra and Barak, in the North and South, form deep valleys, which represent the major part of the state. In between the two river valleys there lies a region of folded structure and plateaus of North Cachar Hills and Karbi Plateau. The two major plains form the easternmost part of North Indian Plains and the Brahmaputra Plain is connected with the mainland by a narrow corridor of foothill land in North Bengal. The width of the corridor is about 33 km on the eastern side and 21 km on the western side, and the link is subjected to occasional disruptions due to heavy rain and flood. Iti geographically a composite state consisting partly of the Pre-Cambrian Deccan Plateau, partly of the late Tertiary sedimentary formations, and partly of the sub-recent and recent alluvial deposits. 

   The Brahmaputra plain in the north lies at the southern foot of the steeply rising Arunachal Himalaya and Bhutan Himalaya. To the east of the plains lie the Patkai Range and the hills of Nagaland and Manipur. Although the state is surrounded by hills and mountains on three sides, it is not entirely cut off from Tibet and South-East Asia beyond these hills and mountains, as there are a large number of mountains passes across both the Himalayas and Eastern Hills. As there is a linkage, there has been movement of people and other materials along with trade, either directly or indirectly, between Assam with Tibet and other South-East Asian countries. Assam, along with the rest of North-East India, is a transitional zone between South Asia and South-East Asia. The transition is reflected not only in the region's flora and fauna, but also in human types, languages and cultures. Assam is politically surrounded by seven states (Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya and West Bengal) and two foreign countries (Bhutan and Bangladesh). There are very few states in India having such a location and which became the reason for Assam to be strategically very important.

Assam District name and area

Assam District Map

Geography Profile of Assam

Geologically, Assam is a very complicated region since it exists on the dynamic frontal part of the Indian Plate and the relatively stable Asian or Chinese Plate. The geologic formations occurring in Assam belong to the Achaean, Pre-Cambrian, Tertiary and Quaternary periods. Based on its geologic history, the formations in Assam may be broadly classified into five. 

  This includes: 

      (a) The Archaen group of rocks, 

      (b) The Pre-Cambrian rocks, 

      (c) The lower Tertiary sediments, 

      (d) The upper Tertiary sediments and 

      (e) Quaternary alluvial sediments.


    The present physiographic configuration of Assam has taken its shape only during the geologically recent times. The geologic and tectonic base of the state has given rise to a variety of landforms under varying climatic conditions and geomorphic processes. However, Assam's physiography may be described in terms of the physiographic elements like plains, floodplains, hills, foothills, plateaus andr valleys. Thus, the broad physiographic divisions of Assam can be delineated as 

(1) The Alluvial plains of the 

       (a) Brahmaputra Valley and 

       (b) Barak Valley,

(2) The Plateau Region and 

(3) Tertiary folded hills of the North Cachar Hills.

    1. The Plains: There are two major alluvial plain regions in Assam. Of the two, Brahmaputra plain is the larger, in fact,

the largest plain in NE India and occupies an area of 58,315 sq km. The second important plain, i.e., the Barak Plain is the second largest one in north-east India and has an area of 6,962 sq km.

  (a) The Brahmaputra Plain: 

       The Brahmaputra Plain is the major physiographic unit of Assam. It is a narrow valley with an approximate east-west extension from Lohit Plain in the east to Sadiya up to the Sonkosh river in the west about 720 km and an average width of 80 km. The plain has the Arunachal and Bhutan Himalayas to its north, the Patkai Range and Arunachal Hills to its east and Naga Hills, Karbi Plateau and Meghalaya Plateau to its south. To the west, it is open to the Ganga Plain. Thus, it is recognized as the easternmost part of the vast Indus-Ganga-Brahmaputra Plain. There are 32 major north and south bank tributaries drain the valley which covers about 72 percent of the total area of Assam. Although the plain is of depositional origin, it has attained its present shape and size to some extent due to the result of both

gradational and degradational activities of the Brahmaputra and its numerous tributaries.

    The Brahmaputra plain is relatively wide in its upper part where it about 90 km between the Himalayas and Naga hills. In the middle part, the Karbi Plateau projects the plain northward restricting the width to about 40 km to 50 km near Burhapahar between Numaligarh and Jakhalabandha. Farther west near Guwahati the plain becomes narrow and about 70 km as the Meghalaya Plateau projects northward. At Kokrajhar-Goalpara-Dhubri area the plain is about 90 km again.

     The Meghalaya and Karbi Plateau have their outcrops projected towards north-eastward and northward has given rise to some isolated hillocks on both the banks of Brahmaputra. Some of them are

Dirgheswari (329 m), Agiathuri (205 m), Rakshasini (93 m), Hatimura (228 m), Hillocks of Jogighopa, Mahadeo (110 m), Chakrashila (216 m), Bhairab Pahar (498 m), Biswakarma (320 m), Dudhnath

(210 m) and Tokrabandha (258 m).

  The mighty Brahmaputra has a large number of tributaries both in its North bank and South.

Important of them are:

 To the north of the plain, along the foothill of the Siwalik range, is narrow (hardly 4 km to 5 km wide). Here the ground seems to be steeply developed from the foothill to the plain. This strip of land is known as
Bhabar Zone. This zone mainly consists of boulders and pebbles, where water flows down its surface and the small streams disappear.To the south of the Bhabar zone is known as Tarai Zone that lies along the north bank of the plain. The water in this region reappears after flowing down the surface in the Bhabar region. Hence, this zone forms marshy and swampy areas and supports tall grasses and some trees.

   Along the southern border of the Tarai region, there is the region of built-up zone, which merge towards the south with the Brahmaputra flood plain zone. This is the active flood plain and is made up of the recent alluvial deposits carried by the river Brahmaputra and its territories from the surrounding highlands. This is the zone of immense human significance with high population density, rich agricultural fields and a good network of roads and railways. The north bank plain is relatively wider in the lower Brahmaputra valley while it narrows down in the upper Brahmaputra valley. The south bank plain, on the other hand, is narrower near the districts of Kamrup, Goalpara and Dhubri because of the Meghalaya plateau, which is projecting towards the north. 

    Although the river Brahmaputra flows all throughout the year, after the month of September the water level recedes and forms a braided channel. The braided channel gives rise to the riverine islands locally known as chars and chaparis. Some of them are tempOrary and some are permanent ne pernmanent ones are often inhabited by the immigrant settlers and carry out different agricultural crop cultivation.

  The eastern part of the plain, there is the largest riverine island Majuli (352 sq km) which is claimed to be the largest riverine island of the world. The island has been suffering from bank erosion since the great earthquake of 1950 and since then it has lost almost more than half of its area.  

     The north-bank and south-bank plains together form extensive low-lying areas with swamps. ox-bow lakes and grasslands, where many National Parks and Wildlife Sanctuaries are located,

Unlike the north-bank, the southern foothill zone does not have distinct Bhabar and Tarai belt, but in the eastern part of the valley near the foothill region having higher grounds supports many tea gardens.

     (b) The Barak Plain

The Barak plain in the southern part of Assam forms one of the important physiographic units of Assam. lt is bordered by North Cachar hills (Barail range) on the north, Manipur hills on the east, Lushai or Mizo hills on the south, and the plain merges with the Sylhet plain of Bangladesh towards west. The shape of the plain is of a horse-shoe type that extends for 85 km from east to west. The width of the plain is 80 km. Total area of the Barak plain is 6,962 sq km.

     The Barak river originating from Japvo Peak (Nagaland) also has a large number of tributaries. Some of the important ones are as follows:

   This plain also gradually rises to the north and south and merges with the foothills, which provide ideal sites for tea gardens.

2. The Karbi Plateau Region: The Karbi Plateau is the extended part of Meghalaya Plateau, which is again an extension of the Chotanagpur Plateau. The Karbi Plateau is found in two divisions, and they are separated by the river Kapili and its tributaries. The south-western part is known as Hamren Plateau, which is the continuation of Jaintia Plateau. The other one is the Central Karbi Plateau.

(a) The Central Karbi Plateau: The Central Karbi Plateau is the easternmost part of the plateau region. It resembles the shape of guava with an area of 7,400 km2. This part is separated from the Hamren division by the river Kapili and its tributaries and the river Dhansiri makes it isolated from the Naga Hills. The base of this plateau is towards north up to the bank of the Brahmaputra near Kaziranga. The Dhansiri plain is towards its east and Kalong-Kapili plain towards west. The North Cachar Hills forms the southern boundary. The hard crystalline rocks in the plateau form the Rengma Range with a height of 1,363 m at Dambuksu and 1,359 m at Singhason. The Central Karbi Plateau slopes down on all sides and thus the streams also flow in all directions and develop the radial drainage pattern. The main east-flowing rivers are Hariahjan, Deopani, Nambar, Daturang, Kaliani and Diphalu. The major west-flowing rivers include Deopani, Chapanala, Diju, Na-Noi, Dikharu and Jamuna. River Langit and Patradisa slope down to south. Jamuna is the major tributary of Kapili (largest south-bank tributary of Brahmaputra).

(b) The Hamren Plateau: The Hamren Plateau is the continuous part of the Jaintia Hills in Meghalaya. The plateau has a general slope from south-west to south-east. The streams that flow in this plateau are the tributaries of Kapili and all of them flow south-west to north-east and join the Brahmaputra. 

3. The Tertiary Folded Hills of North Cachar Hills: The Tertiary Folded Hills are the southern extension or the offshoots of Himalayas. The various ranges are found in the North Cachar Hill district. The ranges in the district are known as Barail Ranges. The central or the middle part is the highest region of the N.C. Hills district. The successive parallel ranges become lower in both the northern end up to Brahmaputra plain and to the southern end up to Barak plain. The Barail Range acts as the common watershed of the Brahmaputra river basin and the Barak river basin. The highest peaks of the Barail Range are Theipibung (1,866 m), Mahadeo (1,739 m) and Kaukaha (1,736 m) are the main. The weathering and erosion are more active in the region because it falls under hot and humid climatic conditions that lead to the development of deep valleys, gorges and steep slopes.

Assam physical map