|
|
|
|
Geomorphology
Geological history indicates that the landform of Majuli is of depositional in origin that is recent times. The largest island was formed by the diversion of the Kherkutia channel from the main stream of the Brahmaputra. This channel subsequently receives the waters of the Subansiri, in it self a large river and is then known as the Luhit to the point where it rejoins the present stream opposite the mouth of Dhansiri. The alignment of the island is mostly in the north-east to south-west direction. Majuli is situated between the two distinct channels of the Borluit or the Louhitya. The southern channel of the Louhitya is known as the Brahmaputra. Majuli is fully covered by these two broad cannels of the river for which it is called as the riverine island. From Geomorphological point of view, the landform of Majuli is as old as the landform of the upper Brahmaputra valley. About 300 years ago Majuli was not an island. This whole Majuli area was well attached to the southern side of the greater upper Assam valley. The phenomenon of conversion of Majuli into Riverine Island is not more than 300 years old. A good number of tributaries from North and South usually brought flashy floods with heavy load of fine silt and clayey sediments. They has also very steep slopes, shallow braided shifting channels and had course of sandy beds. This process helped in lateral severe erosion in south side of the Brahmaputra River. In fact though the Brahmaputra performed the works of transportation, deposition and erosion in its course maintaining the balance of the volume of water from time immemorial, the work of deposition and erosion were more active. Basically for this reason, the south bank erosion process of the Brahmaputra is more than the north bank. This fact was almost established that such type of natural condition was prevailed in this area during thirteenth century A.D. Thus, while the Brahmaputra shifting towards south either due to recurrent flood and flood and bank erosion captured the lower course of the Burhi-Dihing so as to form the biggest river island called Majuli.