Purvanchal Mountain Range of North East India | UPSC, APSC

The Purvanchal Range or Eastern Mountain is a sub-mountain range of Himalaya. “Purvanchal” as the name itself suggests, it is the eastern frontier region of India is surrounded by Bangladesh in the south-west, Myanmar in the south-east and china in the north-east. Its north-western limit, for a major part, follows the boundaries of Meghalaya-Mikir region, Assam valley and Eastern Himalaya and the plain areas of Tripura and Cachar are the continuations of Surma valley.

Geography of Purvanchal Range

Purvanchal Range covering an area of about 94,800 km2 with a population of over 4 million incorporates Nagaland, Manipur, Tripura and Mizoram Hills and Chachar Districts along with the fifth of Haflong tahsil of Assam State and District of Tripa and part of Lohit in Arunachal Pradesh. Its length from north to south is about 755 km and the maximum width from east to west is about 615 km.

The range is an eastern extension of the Himalayan Range System, in northeastern India. It bends sharply to the south beyond the Dihang River gorge and spreads along the eastern boundary of India with Myanmar. The Purvanchal Range has five important hills viz., Patkai Hills, Manipur Hills, Naga Hills, Lushai Hills and Jampui Hills.

Physiography of Purvanchal Range

The very fact that the Purvanchal chiefly comprises of Eastern Mountain gives a sufficient indication regarding its topographic characteristic. The ranges of Assam Himalaya running east-south take a Hair-pin bend where they cross the Lohit and thence extend southwards across the region beyond which they are known as the Arakan Yoma. The region is tightly packed with North- south aligned ranges defined by narrow and parallel valleys towards the west.

Except for Tripura and Cachar plains the altitude does not fall below 150 m. In the Mizo hills, the major portion of the area is confined between 150 m and 900 m through the peak of over 1500 m elevation is not rare. 

A narrow belt of the same level also runs along the upper portion of the North-western boundary of the region denoting a transition between the Assam valley in the west and the hills and mountains in the east. Another important region belonging to this class is Imphal valley where 900 m contour is taken as the outer limit.

It is roughly oval in shape at least 32 km from north to south and at least 32 km east-west. It may be compared with an oblong shallow saucer, the lowest part of which is formed by the Loktak Lake.

The general elevation of Purvanchal increase towards the northeast and altitudinal range of 900 m to 2100 m covers a large part of the Manipur hills and Nagaland. Beyond this, the height again decreases to less than 900 m in the western part of the Tirap and Lohit District of Arunachal Pradesh.

Starting from the north, Dapha Bum is the highest range of not only the Lohit district but of the Ranges of the region as a whole, with a maximum altitude of 4579 m and is highly dissected by rivulets and streams. In Nagaland the Barail range piercing from the south-west via North Cachar runs up to Kohima with a height peak Japavo (2970 m).

Further east is the Kohima hills and the Naga range. The eastern frontier of Nagaland and functions as the water – shade between the rivers of India and Myanmar but is cut across by the Tixu river drainage eastward into the Chindwin. 

This range has several peaks of more than 3000 m with Saramati (3926 m) the highest. The hills of Manipur are found to make an oval rim eclosing the Imphal Valley. The region ends in the south with Lushai hills which exhibit a typical alternate arrangement of parallel ridges and valleys.

The Tripura-Cachar region represents a low-lying plain pierced by series of long-drawn sharp spurs projecting from the Lushai or Mizo hills. (Singh R. L.,2006)

Hills of Purvanchal Range

1. Patkai Bum Hills: It is situated on India's North-Eastern border with Burma. The word "Patkai" means "to cut chicken" in Tai-Ahom language. It is originated by the same tectonic processes that resulted in the formation of the Himalayas in the Mesozoic. These hills are crammed with conical peaks, steep slopes and deep valleys but they are not as rough as the Himalayas. The whole region is surrounded by forests comprising of sandstone.
2. Naga Hills: It is located in India extending into Myanmar which forms a divide between India and Myanmar.
3. Manipur Hills: It is located in the north of Nagaland, Mizoram in the south, upper Myanmar in the east and Assam in the westbound Manipur Hills.
4. Mizo Hills or Lushai hills: It is formerly called Lushai Hills. It is located in south-eastern Mizoram state, north-eastern India, forming part of the north Arakan Yoma system.
5. Tripura Hills or Jampui Hills:  These hills are a series of parallel north-south folds, decreasing in elevation to the south until they merge into the greater Ganges-Brahmaputra lowlands (also called the Eastern Plains). Each successive ridge of hills to the east rises higher than the one before; the low Deotamura Range is followed by the Artharamura, Langtarai, and Sakhan Tlang ranges.

The Climate of Purvanchal Range

The region has a typical monsoonal climate with variants ranging from tropical to temperate conditions. The rapid change in topography resulting in a change in climate within short distances. The climate of Purvanchal exhibits a strong seasonal rhythm, the year being divisible into four characteristic seasons:

Winter (December- February): 

The beginning of winter is marked by a steep fall (5⁰ c) in temperature during the first month. January is the coldest month. In February the temperature gradually starts rising.

Pre-monsoon (March-April): 

The commencement of the pre-monsoon period is felt in the very first week of March through a sudden increase of temperature. With the advance of the season, the amount and frequency of rain increase.

Monsoon (May-September): 

The monsoon period lasting for about five months. The tendency of the rise in temperature which remains a characteristic of the pre-monsoon period is brought to almost a standstill by the long spells of rain. June is the wettest month followed by July and May.

Retreating Monsoon (October- November):

Toward the end of September the south-eastern winds become feeble and the following two month experiences their retreat. The rain gradually stops and the temperature moves downward and the sky becomes clear. The season is the most pleasant of the year. (Singh R. L.,2006)

Natural Vegetation of Purvanchal Range

The Purvanchal may still be considered as a treasure land of natural vegetation through its forest have suffered a lot due to century-old Jhuming practices. The variation in altitude, latitude, climate, and soil have given rise to a diversity of forest types ranging from tropical evergreen to temperate evergreen and the coniferous.

Photiki and Photkola grow in deep ravines and assume the form of small tree. The bamboo jungle is extensive everywhere. Apart from these, Mesua ferrea, Careya arbotrea, Ficus electica, etc are some other plants that are commonly found under the tropical evergreen group. The important tree comprising the temperate evergreen type forest are oak, chestnut, birch, Mongolia, chery, maple, laurel, fig, and moly. (Singh R. L.,2006)