Geological Structure of India Geological Structure of India
Master the geological divisions of India — Peninsular Block, Himalayas, and Indo-Gangetic Plains — along with the Rock Systems (Archean to Aryan) for UPSC Prelims & Mains. Geological Structure of India पर UPSC सिविल सेवा परीक्षा अध्ययन गाइड।
Geological Structure of India
Master the geological divisions of India — Peninsular Block, Himalayas, and Indo-Gangetic Plains — along with the Rock Systems (Archean to Aryan) for UPSC Prelims & Mains.Geological Structure of India पर UPSC सिविल सेवा परीक्षा अध्ययन गाइड।
Core Concepts & Provisionsमुख्य अवधारणाएँ एवं संवैधानिक प्रावधान
1. Three Major Geological Divisions of India
Geologically, India is divided into three distinct regions with contrasting structures, rock types, and tectonic behaviors.
- Characteristics: The oldest, most rigid, and stable block of India. Primarily composed of ancient Archean gneisses and granites.
- Stability: Has stood as a rigid shield since the Cambrian period, only experiencing minor vertical adjustments and coastal submergences.
- Characteristics: Young, weak, and flexible geological structure. Formed by sedimentary deposits of the Tethys Sea squeezed between two colliding plates.
- Tectonics: Active plate collision means the mountains are still rising, characterized by folding, faulting, and high seismicity.
3. The Indo-Gangetic Plains: A deep geological depression (foredeep) formed between the rising Himalayas and the stable Peninsula. It is filled with Pleistocene-to-Recent alluvial deposits brought by the Indus, Ganga, and Brahmaputra river systems. Its alluvium thickness ranges from 1,000 to 2,000 meters, making it the youngest geological region of India.
2. Classification of Indian Rock Systems
The rock systems of India are categorized into four major eras, spanning from the oldest Precambrian base to recent sediments.
- Archean System: Gneisses and Schists forming the basement complex. **Dharwar System** is metamorphosed sedimentary rock containing India's major iron, manganese, copper, and gold deposits.
- Cuddapah System: Famous for slates, quartzites, and limestone. **Vindhyan System** contains sandstone and diamond mines (Panna, Golconda).
- Gondwana System: Formed in river basins; contains 98% of India's coal reserves. Highly fossiliferous (mainly plant fossils like Glossopteris).
- Deccan Traps: Basaltic lava flows over 500,000 sq km, formed by fissure eruptions when India passed over the Reunion hotspot. Weathered into fertile **Regur (Black Cotton) soil**.
Comparison of Indian Rock Systems:
| Rock System | Geological Era | Fossil Content | Economic Importance & Minerals |
|---|---|---|---|
| Archean / Dharwar | Precambrian (Archean) | Unfossiliferous | Metallic minerals (Iron, Manganese, Gold, Copper) |
| Cuddapah / Vindhyan | Precambrian (Proterozoic) | Unfossiliferous / Traces | Limestone, sandstone, ornamental stone, diamonds |
| Gondwana System | Carboniferous to Jurassic | Highly Fossiliferous (Plants) | Bituminous Coal (98% of India's reserves) |
| Deccan Traps | Upper Cretaceous | Rare / Intertrappean beds | Building stone, bauxite, fertile Black Cotton Soil |
Tectonic Cross-Section of Northern India:
Geological Section: Himalayas to Peninsula
3. Physiographic Divisions Linked to Geological History
The geological structure controls the physical features and soils of India, laying the foundation for its agricultural and economic zones.
- Khadar and Bhangar: Newer (Khadar) and older (Bhangar) alluvial belts dictate crop suitability.
- Karewas: Flat-topped terraces of lake deposits in Kashmir, highly valuable for saffron cultivation.
- Chotanagpur Plateau: The mineral heart of India, composed of Dharwar and Gondwana structures.
- Deccan Regur: Fertile black soil supporting the cotton textile hub of Western India.