Physiography of India

Physiography of India

Physiography means the description of the physical relief features of a country. India has a well defined physiographical entity. The present physiography of India have evolved in the course of a long chequered geological history. The remains of flora and fauna preserved in different layers of the rocks help to determine their age. To understand the varied physical features of India, let us have a glance on geological history of India.

Geologists believe that it was the shrinking action of the Tethys Sea that created the Himalayan Mountains. The Himalayas gave birth to agents of gradation such as the rivers and the glaciers. The Himalayan Mountains extend from Pamirknot in the north-west to Kasi Jaintia Hills in the east. The lofty mountains acted as gigantic physical boundary and prevented invaders to enter India during the Medieval Period. The glaciers such as Gangotri and Yamunotri have become religiously significant for they are the sources of the holy rivers, the Ganga and the Yamuna. The pilgrim centers such as Kedarnath and Badrinath, and hill resorts such as Gulmarg and Nainital are also located in the Himalayas. The lower ranges of the Himalayas have valleys such as Dehradun.

The agents of gradation such as rivers and glaciers carried huge amount of silt and deposited into the Tethys Sea. This erosion process led to the formation of Northern Great Plain. The vast area of the Great Plains has a great agricultural significance. The plains support the cultivation of rice and wheat in large quantities and hence they are called the granary of our country. The Himalayas, the Northern Great Plains, the Peninsular Plateau and the coastal lines became important political divisions of India. The Himalayas became not only active climatic barriers but also the birth place for hundreds of rivers. The river basins of these rivers are responsible for the growth of civilizations.

The Western Ghats and the Eastern Ghats the twin system of mountains, that lie in the Peninsular India are part of Gondwana landmass. The Western Ghats is famous for its thick lush evergreen forests. The Eastern Ghats is a series of hills located mainly in the south-eastern regions of India. India's coastline is the largest of its kind in the world. The coastal plain that extends from the Rann of Kutch in the west to the West Bengal in the east passes through Kanyakumari in the south. The fertile deltaic soil found in the deltas created by the rivers has made the coastal plain an area of intense agricultural activity. The Andaman and Nicobar Islands in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea are the two main Island groups in India.

Major physiographic divisions

The land of India is characterised by a great diversity in its physical features. Based on the structure, India may be divided into five physiographical units. They are,

- The Himalayan Mountains

- The Northern Great Plains

- The Peninsular Plateau

- The Coastal Plains

- The Islands

I. The Himalayan Mountains

The Himalayas in the Northern India, consists of series of parallel mountain ranges with bold relief and complex topography. 

The Himalayas are further subdivided into 3 parts. They are,

- The Western Himalayas

- The Central Himalayas

- The Eastern Himalayas

II. The Northern Great Plains

The great plains lie between the mountains of the north and the peninsular plateau of the south. It extends over a length of 2400 km. It has a width of 2400 km in Bihar to 500 km in Punjab.

The Great plains is a flat low lying land made up of Alluvium – the fine silt brought down by the rivers. The plain in the past was a huge depression where the rivers have deposited layers of alluvial sediments.

The three big rivers draining this region are Indus, Ganga and Brahmaputra. They collect their water from Himalayan glaciers. The rivers cross the lofty Himalayan range through narrow deep gorges or deep canyons and enter the plains. Geologists consider that these three rivers were older than the Himalayas that as the Himalayas lifted themselves up, the rivers have eroded their valleys. The northern plains are the youngest as they are made up of sediments laid down by the denudation of the Himalayas.

The surface relief of great plains are classified into four types based on the structure of soil.

i. The Bhabar lies all along the foot hills of siwalik. It is a pebble – studded zone of porous beds. It is a narrow belt with 8 to 16 kms 2

ii. The Terai belt is marked by excessive dampness with the growth of thick forest and a variety of wild life.

ii. The Bhangar is the older alluvium of the plain.

iv. The Khadar is the new alluvium of the plain. They form a continuous belt of alluvium. These plains may be subdivided into the following basins.

• The Indus basin

• The Ganga basin

• The Brahmaputra basin

• The Ganga - Brahmaputra Delta

i) The Indus basin

The Indus river has its source in the Kailash range to the north of Manasarovar lake. It was the cradle of ancient Indus valley civilization. It flows in a north westerly direction. It takes a turn to the south through Ladakh range I enters Pakistan through Kashmir. It receives water Women Ravi, Beas and Sutlej. All the rivers except Sutlej rise in the Himalayas. The Sutlej originates in the Manasarovar region in Tibet and enter the plain through deep narrow gorges. The Indus then flows across the desert plains of Sind and drains into the Arabian sea.

ii) The Ganga basin

iii) Brahmaputra basin

The river Brahmaputra originates from a glacier, south east of manasarovar region. It flows through deep gorges and enters into the lowlands of Assam. The valley slopes from east to west. It is frequently flooded and takes away a heavy toll of life during the monsoon. It joins the lower course of Ganga and flows into Bay of Bengal.

iv. The Ganga Brahmaputra Delta

It is the largest and fastest growing delta of the world. The Brahmaputra after joining the Ganga splits into numerous distributaries. Due to the gentle slope, the river becomes sluggish, and enormous amount of silt is deposited. The lower part of delta becomes marshy where fresh water and sea water gets mingled owing to high and low tides.

Significance of Plains :

1. These vast plains are called granaries of our country, growing rice and wheat in large quantities.

2. The climatic conditions favour cultivation of a wide variety of crops namely cotton, Jute, Sugarcane, pulses and oilseeds.

3. Numerous perennial rivers enable irrigation in areas of erratic rainfall.

4. Dams have been constructed across these rivers which help in generating hydro electric power.

5. This in turn leads to the development of industries.

6. The flat nature of the plains facilitate construction of roads and railway lines.

7. A large number of towns have come up in the plains as industrial, pilgrimage, commercial and educational centres.

8. All these factors have favoured a high concentration of population in the great plains.

III. The Peninsular Plateau .

The peninsular plateau lies to the south of the Great plains. It is triangular in shape with its broad base in the north. The plateau features a series of mountain ranges that rise abruptly from the adjoining plains. It has a senile topography dominated by erosional surface and broken by striking ridges and trough valleys. When the Gondwana land was subjected to earth movements there occurred a number of fissures in the northwestern parts. Through the fissures lava flowed out and deposited on the peninsular plateau. Thus, thi lava plateau underwent several geological changes.

The peninsular plateau is subdivided into 2 parts. They are :

1. The Central Highlands

2. The Deccan Plateau.

IV. The Peninsular Plateau .

The peninsular plateau lies to the south of the Great plains. It is triangular in shape with its broad base in the north. The plateau features a series of mountain ranges that rise abruptly from the adjoining plains. It has a senile topography dominated by erosional surface and broken by striking ridges and trough valleys. When the Gondwana land was subjected to earth movements there occurred a number of fissures in the northwestern parts. Through the fissures lava flowed out and deposited on the peninsular plateau. Thus, thi lava plateau underwent several geological changes.

The peninsular plateau is subdivided into 2 parts. They are :

1. The Central Highlands

2. The Deccan Plateau.

V. The Islands

Besides the mainland, Indian territory also extends into the Arabian and the Bay of Bengal in the form of the Lakshadweeps and the Andaman and Nicobar Islands respectively. The Lakshadweeps are small Coral Islands. The Andamans and Nicobars are cluster of Islands stretches almost in a line. There are as many as 200 islands in the Andamans Group extending for 350 kms. There are 19 islands in the Nicobar group. Some of the islands are of volcanic origin. ‘Barren island' is an active volcano. This is the only active volcano of India.

The physical features of India, though different from each other, they are complementary to one another. It influences the climatic conditions and favours man's varied activities.