•As per the estimation, the earth is approximately 460 million years old.
•The endogenic and exogenic forces played a significant role in giving shape to the various surface and subsurface features of the earth.
•The theory of Plate Tectonics defines the formation of physical aspects of the earth.
•The northern part of the ancient supercontinent Pangea was named ‘Angara Land’ or Laurasia and the southern part was named ‘Gondwana Land.
•The Gondwana Land includes India, Australia, South Africa, South America, and Antarctica.
•Based on geological history, India is divided into three regions. The regions are:
- The Peninsular Block;
- The Himalayas & other Peninsular Mountains; and
- Indo-Ganga-Brahmaputra Plain.
•The Peninsular Block is formed essentially by a great complex of very ancient gneisses and granites.
•The Peninsular Block mostly consists of relics and residual mountains like the Aravali hills, the Nallamala hills, the Javadi hills, the Veliconda hills, the Palkonda range, the Mahendragiri hills, etc.
•the rigid and stable Peninsular Block, the Himalayan Mountains are young, weak, and flexible in their geological structure.
•Indo-Ganga-Brahmaputra Plain comprises the plains formed by the river Indus, the Ganga, and the Brahmaputra.
•In fact, Indo-Ganga-Brahmaputra Plain is a geo-synclinal depression, which attained its maximum development during the third phase of the Himalayan mountain formation, approximately about 64 million years ago.
India’s physiography is divided into six following regions:
- The Northern and Northeastern Mountains
- The Northern Plain
- The Peninsular Plateau
- The Indian Desert
- The Coastal Plains
- The Islands.
Northern and NortheasternMountains
•The Northern and the Northeastern Mountains consist of the Himalayas and the Northeastern hills.
•The Himalayan Ranges include the Greater Himalaya, Lesser/Middle Himalaya, and the Siwalik Range.
•Based on relief, alignment of ranges, and other geomorphological features, the Himalayas can be divided into the following sub-divisions:
- Kashmir or Northwestern Himalayas
- Himachal and Uttaranchal Himalayas
- Darjeeling and Sikkim Himalayas
- Arunachal Himalayas
- Eastern Hills and Mountains.
Kashmir or Northwestern Himalayas
• Kashmir or Northwestern Himalayas consist of a series of ranges such as the Karakoram, Ladakh, Zanskar, and Pir Panjal.
• Important glaciers of South Asia, i.e., the Baltoro and Siachen are found in the Northwestern Himalayan region.
• The Kashmir Himalayas are also popular for the Karewa formations, which are useful for the cultivation of Zafran, a local variety of saffron.
• Kare was are the thick deposits of glacial clay and other materials embedded with moraines.
• Important passes of the Northwestern Himalayas are Zoji La on the Great Himalayas, Banihal on the Pir Panjal, and Khardung La on the Ladakh range.
• Important fresh lakes are Dal and Wular and saltwater lakes are Pangong Tso and Tso Moriri.
• The southernmost part of the Northwestern Himalayas consists of longitudinal valleys locally known as duns.
Himachal and Uttaranchal Himalayas
• The Himachal and Uttarakhand Himalayas are located approximately between the rivers Ravi in the west and the Kali (a tributary of Ghaghara) in the east.
Darjeeling and Sikkim Himalayas
• The Darjeeling and Sikkim Himalayas are flanked by the Nepal Himalayas in the west and the Bhutan Himalayas in the east.