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Physiography- India

UPSC notes on Indian Physiography- Division of India based on its Geological Structure and Formations, Movement of Indian Plate, The Himalayas and other Peninsular Mountains, etc.

Introduction

‘Physiography’ of an area can be defined as geological structures, processes and the different stages of its development. The Earth and its landforms have evolved over a long period of time. According to current estimations, planet Earth is over 460 million years old. Over these years, it has undergone many changes caused primarily by endogenic and exogenic forces. These forces have brought significant changes to Earth’s physiography, including its various surfaces and subsurfaces. Consequently, Indian physiography has also witnessed several changes over the years. 

Movement of the Indian plate

  • Over a million years ago, the Indian and Australian plates were the same. They coexisted south of the equator. 
  • After their separation, the Indian plate moved towards the northern hemisphere and the Australian plate towards the southern hemisphere.

Division of India based on its geological structures and formations

  • The Peninsular Block
  • The Himalayas and other Peninsular Mountains
  • The Indo-Ganga-Brahmaputra Plain

The Peninsular Plateau Block

  • The Peninsular Plateau’s northern boundary may be understood as an irregular line running through Kachchh, the western flank of the Aravali Range to Delhi and then running roughly parallel to rivers Yamuna and Ganga, stretching as far as the Rajmahal hills and the Ganga delta.
  • Extension of the Peninsular Plateau Block: 
    • North Eastern extent: Karbi Anglong and Meghalaya Plateau
    • Western extent: Rajasthan
  • The Malda fault in West Bengal separates the North-Eastern parts from the Chotanagpur Plateau.
  • Rajasthan is characterised by the Thar desert and other desert-like features, creating the Indian desert ecosystem.
  • A significant part of the peninsular region is complex and consists of ancient gneisses and granite.
  • Since the Cambrian period, the Peninsular Plateau has stood like a rigid block.
    • The western coast is an exception, submerged beneath the sea.
    • Other parts changed due to tectonic activity.
  • Being a part of the Indo-Australian plate, the Peninsular Plateau Block of the Indian subcontinent has undergone multiple vertical movements over the years. The rift valleys that characterise Narmada and Tapi and the Mountain blocks of Satpura are prime examples of this phenomenon. 
  • Many ancient and residual mountains characterise the Peninsular Plateau, like the Aravali hills, the Javadi hills, the Palkonda range, the Veliconda hills, etc. River valleys tend to be shallow, with low gradient levels. 
  • Most of the rivers flow towards the east, forming deltas. Examples include rivers Krishna, Godavari and Mahanadi.

The Himalayas and other Peninsular Mountains

  • Unlike the rigid, residual and relict mountains of the peninsular block, the Himalayan block consists mainly of young, weaker mountains that are flexible to geological changes.
  • Owing to the endogenic and exogenic forces at play, the mountains in Himalayan mountain blocks are still changing. This results in the constant development of faults, folds and thrust plains.
  • These mountains are tectonic in origin, characterised by dissections with fast-flowing rivers, typical of mountains in their youthful stage. 
  • This youthfulness of the mountains is further evidenced by multiple landforms like V-shaped valleys and the many waterfalls and gorges that form a part of this region.

Indo-Ganga-Brahmaputra Plain: The Northern Plain 

  • The Northern Plain comprises plains formed by rivers Indus, Ganga and Brahmaputra.
  • Initially, it was a geo-synclinal depression that developed in the third phase of Himalayan formation 64 million years ago.
  • Since then, it has been gradually filled by sediments from the peninsular and Himalayan rivers.
  • The average depth of the alluvial deposits in this region is 1000- 2000 m. This makes it one of the most fertile lands within the Indian subcontinent. 

Physical features of India 

  • The Physical features of India are characterised by:
    • A rugged mountain topography in the North with various peaks, valleys and deep gorges. 
    • A “stable tableland” in the southern part, filled with highly dissected plateaus, developed over a series of scarps and denuded rocks. 
    • The Indo-Ganga-Brahmaputra plain is formed between and due to these two other physiographic features. 

Physiographic division of India

  • The Northern and North-Eastern Mountains
  • The Northern Plain
  • The Peninsular Plateau
  • The Indian Desert
  • The Coastal Plains
  • The Islands

Conclusion

India is a country that is rich in culture, topography and overall physiography. India is divided into six physiographic divisions on the basis of the varied physiographic features: units as follows: Northern and North-eastern Mountain; Northern Plain; Peninsular Plateau; Indian Desert; Coastal Plains; and Islands.