Model Answer
0 min readIntroduction
India's geological landscape is a complex mosaic shaped by millions of years of tectonic activity. The Indian landmass, once part of the Gondwana supercontinent, collided with the Eurasian plate, resulting in the formation of the Himalayas and the diverse geological formations found across the country. Understanding the tectonic subdivisions of India is crucial for comprehending its geological history, resource distribution, and vulnerability to natural disasters. These subdivisions are broadly categorized based on their structural features, age of rocks, and tectonic setting. This answer will delineate the tectonic map of India and discuss the salient features of each subdivision.
Tectonic Sub-division Map of India
(A map should be drawn here, clearly demarcating the following regions. Since I cannot draw, I will describe the regions and their boundaries. A student would physically draw this on their answer sheet.)
The map should show the following regions:
- The Himalayan Region: Northernmost part, extending from Jammu & Kashmir to Arunachal Pradesh.
- The Indo-Gangetic Plain: South of the Himalayas, a vast alluvial plain.
- The Peninsular Shield: The stable, ancient landmass forming the bulk of the Indian subcontinent.
- The Gondwana Land: Eastern and parts of central India, characterized by Gondwana sediments.
- The Deccan Trap: Large igneous province in western and central India.
- The Coastal Plains: Narrow strips along the eastern and western coasts.
- The Island Arcs: Andaman and Nicobar Islands.
Detailed Discussion of Each Sub-division
1. The Himalayan Region
Geological Characteristics: This region is characterized by young, folded and faulted sedimentary and metamorphic rocks. It's a product of the ongoing collision between the Indian and Eurasian plates. The Himalayas are composed of three parallel longitudinal zones: the Greater Himalayan Zone (highest peaks), the Lesser Himalayan Zone (lower ranges), and the Sub-Himalayan Zone (Siwalik range).
Rock Types: Predominantly sedimentary rocks like shale, sandstone, and limestone, along with metamorphic rocks like gneiss and schist. Granite intrusions are also common.
Tectonic History: Formed due to the convergence of the Indian and Eurasian plates starting around 50 million years ago. Continuous uplift and seismic activity are ongoing.
Associated Hazards: High seismic activity, landslides, glacial lake outburst floods (GLOFs).
2. The Indo-Gangetic Plain
Geological Characteristics: A vast alluvial plain formed by the deposition of sediments carried by the Indus, Ganga, and Brahmaputra rivers. It's a relatively flat and fertile region.
Rock Types: Primarily unconsolidated alluvium – sand, silt, and clay.
Tectonic History: A foreland basin formed due to the loading of the Himalayas. Subsidence and sedimentation have been dominant processes.
Associated Hazards: Flooding, riverbank erosion, groundwater depletion.
3. The Peninsular Shield
Geological Characteristics: The oldest and most stable part of India, composed of ancient crystalline and metamorphic rocks. It forms the core of the Indian subcontinent.
Rock Types: Predominantly Archaean and Proterozoic rocks – granite, gneiss, schist, and quartzite.
Tectonic History: Formed during the Precambrian era. Relatively stable tectonically, but experienced some rifting during the breakup of Gondwana.
Associated Hazards: Droughts, limited seismic activity in some areas.
4. The Gondwana Land
Geological Characteristics: Characterized by Gondwana sediments – coal-bearing formations, sandstones, and shales. Found in eastern and parts of central India.
Rock Types: Sandstone, shale, coal, and conglomerate.
Tectonic History: Formed during the Jurassic and Permian periods as part of the Gondwana supercontinent. Rifting and sedimentation occurred during the breakup of Gondwana.
Associated Hazards: Land subsidence due to coal mining.
5. The Deccan Trap
Geological Characteristics: A large igneous province formed by massive volcanic eruptions around 66 million years ago. Characterized by basaltic lava flows.
Rock Types: Basalt.
Tectonic History: Formed during the Deccan Volcanic Province event, associated with the Reunion hotspot. The eruption is linked to the Cretaceous-Paleogene extinction event.
Associated Hazards: Limited seismic activity, potential for groundwater contamination.
6. The Coastal Plains
Geological Characteristics: Narrow strips of land along the eastern and western coasts of India. Formed by marine deposition.
Rock Types: Alluvium, sand dunes, and laterite.
Tectonic History: Formed by the submergence of parts of the Peninsular Shield and deposition of sediments.
Associated Hazards: Coastal erosion, cyclones, tsunamis.
7. The Island Arcs
Geological Characteristics: Andaman and Nicobar Islands are part of the Indo-Burmese arc, formed by the subduction of the Indo-Australian plate under the Eurasian plate.
Rock Types: Volcanic rocks, sedimentary rocks, and metamorphic rocks.
Tectonic History: Formed due to the subduction process. High seismic activity and volcanic potential.
Associated Hazards: Earthquakes, tsunamis, volcanic eruptions.
Conclusion
In conclusion, India’s tectonic subdivisions represent a complex geological history spanning billions of years. Each region possesses unique characteristics, rock types, and associated hazards. Understanding these subdivisions is vital for resource management, disaster mitigation, and sustainable development. Continued research and monitoring of tectonic activity are crucial for ensuring the safety and well-being of the Indian population, especially in seismically active zones like the Himalayas and the Andaman and Nicobar Islands.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.