• Assam is an important geographic location of North-East India. Situated between 89 – 96 East Longitude and 24 -27North Latitude, Assam is bordered in the North and East by the Kingdom of Bhutan and Arunachal Pradesh.
• Along the South lie Nagaland, Manipur and Mizoram.
• Meghalaya lies to her South-West, Bengal and Bangladesh to her West. Although hills and mountains in its three sides surround Assam, there has been always a relation with Tibet of China and South East Asia.
• Assam and the entire North East India is a transitional zone between South Asia and South East Asia. The area of Assam is 78,433 square km.

Physiography:

• The structure of Assam can be divided into three units, they are Karbi Plateau , which is the inner most part of the Meghalaya plateau
• The Tertiary depositional zone which includes hills of North Cachar Hill Districts and Barali range, and Plain of Brahmaputra Valley and Barak Valley.

• Assam is the frontier province of on the North-East. Modern Assam has 22 districts which are akin to counties in the US or the UK. Except for the districts of KarbiAnglong and North Cachar Hills, Assam is generally composed of plains and river valleys. It can be divided into three principal geographical regions: the Brahmaputra Valley in the north; the Barak Plain in the south; and the Mikir (KarbiAnglong) and Cachar Hills that divide the two regions.
• The mighty Himalaya covers three sides of the province. The state shares international boundaries with Bangladesh and Bhutan. Assam serves as a gateway to the South East Asia with its capital city of Guwahati.Whereas at one time Assam had extensive international borders with China/Tibet and Burma, modern Assam’s international borders are limited to those with the small country of Bhutan in the northwest and with Bangladesh to the southwest. Assam is bordered on the north by the Indian state of Arunachal Pradesh that used to be an administrative part of Assam till the 1970s.
• The northern part of Assam is wholly occupied by the elongated valley of the mighty river Brahmaputra. Most of Assam’s population lives in this valley. The Brahmaputra valley is bounded by the foothills of the Himalayas to the north and another lower range of hills and mountains to the south. In the center part of Assam, to the south of the hills is the Barak Valley which is contiguous with the densely populated country of Bangladesh.
• The Karbi Plateau is of the pre-Cambrian origin (5 billion to 570 millions years ago). It contains very old metamorphic rocks, which are highly compressed, hard and crystalline. Other parts of Assam made up of early Tertiary sedimentary deposits (65 million to 2 million years ago) and Quaternary (about 2 million years ago to the present) alluvial deposits.
• Geomorphic studies also conclude that the Brahmaputra, the life-line of Assam is older than the Himalayas. The river with steep gorges and rapids in Arunachal Pradesh entering Assam becomes a braided river (at times 10 mi/16 km wide) and with tributaries, creates a flood plain known as the Brahmaputra Valley (50-60 mi/80-100 km wide, 600 mi/1000 km long). In the south, the Barak, flows through the Cachar district with a 25-30 miles (40-50 km) wide valley and enters Bangladesh with the name Surma.
• Barak Valley is situated in the south Assam. In the north there is North Cachar Hills, in the east there is Manipur Hills and in the south there is Mizoram hills. The area is 6962 sq. km. Assam is full of streams, rivulets, and rivers which receives water from Himalaya and hills and plateaus. The water falls into to basins; they are the Brahmaputra Basin and the Barak-Surma basin.

Geologic and geomorphic origin:

• Geologically, as per the plate tectonics, Assam is in the eastern most projection of the Indian Plate, where it thrusts underneath the Eurasian Plate creating a subduction zone.
• It is postulated that due to the northeasterly movement of the Indian plate, the sedimentary layers of an ancient geocyncline called the Tethys (in between Indian and Eurasian Plates) were pushed upward to form the Himalayas.
• It is estimated that the height of the Himalayas is increasing by 4 cm each year. Therefore, Assam possesses a special geomorphic environment, with large plains and dissected hills of the South Indian Plateau system abutting the Himalayas to the north, north-east and east.
• Geomorphic studies also conclude that the Brahmaputra is an antecedent river, older than the Himalayas, which often crosses higher altitudes in the Himalayas eroding at a greater pace than the increase in the height of the mountain range to sustain its flow.
• The height of the surrounding regions still increasing forming steep gorges in Arunachal.

The Brahmaputra valley:

• The northern part of Assam is wholly occupied by the elongated valley of the mighty river Brahmaputra.
• Most of Assam’s population lives in this valley.
• The Brahmaputra valley is bounded by the foothills of the Himalayas to the north and another lower range of hills and mountains to the south.
• The Brahmaputra Valley is the dominant physical feature of Assam.
• The Brahmaputra enters Assam near Sadiya at the extreme northeast corner and runs westward for nearly 450 miles before turning south to enter the plains of Bangladesh.
• The river valley, rarely more than 50 miles wide, is studded with numerous low, isolated hills and ridges that abruptly rise from the plain.
• The valley surrounded on all sides, except the west, by mountains and is intersected by many streams and rivulets that flow from the neighboring hills to empty into the Brahmaputra.

Barak Valley:

• The KarbiAnglong and North Cachar Hills from the Brahmaputra Valley in Assam separate the Barak Valley.
• The Barak originates from the Barail Range in the border areas of Assam, Nagaland and Manipur and flowing through the district of Cachar, it confluences with the
  Brahmaputra in Bangladesh.
• Barak Valley in Assam is a small valley with an average width and length of approximately 40 to 50 km.