Ch 2: Structure and Physiography

This section covers the geological evolution of India, dividing it into the Peninsular Block, the Himalayas and other Peninsular Mountains, and the Indo-Ganga-Brahmaputra Plain. UPSC tests the spatial extension of the Peninsular block, highlighting that the Karbi Anglong and Meghalaya plateaus are structural extensions of the Peninsula, separated by the Malda fault, not part of the Himalayas. Focus on the rift valleys of Narmada, Tapi, and Mahanadi. Avoid deep geomorphic timeline technicalities but understand the tectonic boundaries. Watch out for traps asserting that the Aravalis are young fold mountains when they are ancient, highly relict blocks.

Contains crucial details on the subdivisions of the Himalayas. Focus on Kashmir Himalayas (Karewas, saffron, Jhelum meanders, salt lakes like Pangong Tso), Himachal and Uttarakhand Himalayas (passes, dun formations), Darjiling and Sikkim Himalayas (absence of Shiwaliks, Duar formations), Arunachal Himalayas (Kameng, Subansiri, Dihang rivers), and Purvachal (Patkai Bum, Naga Hills, Mizo Hills). UPSC repeatedly tests relative locations of glaciers like Siachen (north of Nubra Valley), major passes like Zoji La, Shipki La, Lipulekh, Nathu La, Jelep La, and the tectonic syntaxial bends. Skip local folk-tale details of tribal regions, but memorize the specific tribal names associated with different hills.

Explains the geomorphological divisions of the Indo-Gangetic plains. You must know the exact spatial sequence and hydraulic characteristics of Bhabar (porous pebble belt, disappearing rivers), Tarai (marshy re-emergence, dense forests), Bhangar (older, less fertile alluvium with calcareous kankar deposits), and Khadar (newer, highly fertile floodplains). UPSC tests the difference in agricultural productivity and physical properties of these soils. Skip local terminology of regional distributaries, but pay attention to the geomorphic differences in deltaic regions (like the Bengal delta's char and bil formations).

Covers the Deccan Plateau, Central Highlands, and Northeastern Plateau. Pay careful attention to the structural differences between Western Ghats (continuous, source of major rivers, higher elevation with Anamudi at 2,695m) and Eastern Ghats (discontinuous, highly denuded by rivers, lower elevation with Mahendragiri). Focus on the relict mountains like Aravali, Javadi, Shevaroy, and Nallamala Hills. UPSC frequently frames map-based questions on the north-to-south arrangement of these hill ranges. Avoid memorizing every single local plateau name but retain the major volcanic trap boundaries and rift valley formations.

Deals with the Thar Desert (Marusthali). Focus on key features like Barchans (crescent-shaped sand dunes), the ephemeral nature of the Luni River, and the saline lakes or playas (like Sambhar, Kuchaman, Didwana) which are crucial for salt extraction. UPSC tests the hydrological character of the desert, particularly inland drainage systems and the absence of perennial surface rivers. Skip detailed sand-dune dynamics and wind velocity data.

Contrasts the western and eastern coastal plains. Understand that the Western coast is a submerged coast (making it ideal for natural ports and harbors, featuring estuaries and backwaters/kayals of Kerala) while the Eastern coast is an emergent coast (characterized by broad deltas of Mahanadi, Godavari, Krishna, Cauvery, and offshore bars/spits). UPSC tests this distinction to ask why western ports are natural while eastern ports require dredging. Memorize the regional names like Konkan, Goan, Malabar, and Coromandel.

Covers the Andaman & Nicobar and Lakshadweep island groups. Understand the critical distinction: Andaman and Nicobar are elevated portions of submarine mountains (volcanic/tectonic origin, containing Barren Island, the only active volcano), while Lakshadweep is of coral origin. Memorize the major channels: Ten Degree Channel (separates Andaman from Nicobar), Eleven Degree Channel (separates Amindivi and Cannanore islands of Lakshadweep), and Duncan Passage. UPSC regularly frames questions on these channels and ecological assets like coral reefs. Skip detailed population census data of these islands.