PHYSIOGRAPHY OF NORTH EAST INDIA

PHYSIOGRAPHY OF NORTH EAST INDIA

The North East India region is physiographically not a homogenous unit and the present configuration of this region has taken shape during geologically recent time. But the ultimate result of various geological events took place through the geological past. North East India consists of very ancient Archaean and Shillong series rocks exposed in several parts of the Garo, Khasi, Jaintia and Karbi Hills. These rocks are similar to rocks exposed in the rest of the peninsular in Bengal and Bihar of which this was a part at one geological time. All these old rocks form the basement for very much younger Tertiary sediments in upper Assam.

   A large part of this region was a landmass upto the formation of the Himalayas about 2,000 million years ago. Then the eastern part of the Khasi Hills, the Jaintia Hills and the Western pat of the Karbi Hills became a basin of sedimentation in which sandstone and shales of the Shillong series were deposited. Due to tectonic reasons these were later uplifted and became a landmass.

Thus the geomorphological evolution of the Noth-eastern region of India is one of uplift and sinking in various parts during the past 100 million years.

Richard E Murphy has divided the landforms of North East India on the basis of both genetic and empirical factors and his physiographic divisions and sub-divisions are given below:

1. The Plateaus: Meghalaya plateau, Karbi Plateau

2. The Hill and Mountains   Region: Himalayan Mountains Region, Inner Himalayan (Glacial and Periglacial) Lesser Himalayan Region, Easern Hills, Dibong-Lohit Knot, Patkai-Hrap-Nagaland-NothCadmr and Manipur Hills, Mizoram-Tripura Range and Valley country

3. The Plains :  Brahmaputra Plain, Bhabar-Tarai/Belt, Northern Built-Up strip, Brahmaputra Flood Plain, Southern Built-up Strip, Southern Foot-hill zone, Intermontane and Piedmont plains, Manipur Basin, Barak Plain, Tripura Plain.

But recent scholars have divided North East India into five physiographic units on the basis of lithology, age and mode of evolution. The physiographic divisions of the region are:

(1) Karbi-Meghalaya Plateau

(2) North-Eastem frontier mountain ranges or Arunachal Himalaya

(3) Brahamputra Valley

(4) Barak Plain or Cachar Plain

(5) South-Eastern Hill Ranges