Model Answer
0 min readIntroduction
The Deccan Volcanic Province (DVP) represents one of the largest volcanic features on Earth, a massive igneous province formed by extensive basalt eruptions. Located in India, it covers a substantial portion of the western and central Indian plateau. The formation of the DVP is closely linked to the Reunion hotspot and the passage of the Indian plate over it during the late Cretaceous and early Paleogene periods (approximately 66 to 62 million years ago). This volcanic activity had a profound impact on the regional and global climate, potentially contributing to the Cretaceous-Paleogene extinction event.
Formation and Geological Setting
The DVP’s formation is primarily attributed to the Reunion hotspot, a mantle plume located beneath Réunion Island in the Indian Ocean. As the Indian plate drifted northeastward, it passed over this hotspot, leading to decompression melting in the mantle. This resulted in the generation of voluminous basaltic magma. The initial phase involved fissure eruptions, followed by the development of shield volcanoes and flood basalts.
Extent and Stratigraphy
The DVP originally covered an area of approximately 1.5 million square kilometers, though erosion has reduced its present-day extent to around 500,000 square kilometers. The basalt flows are layered, forming a staircase-like topography known as ‘traps’ (from the Swedish word for stairs). The stratigraphy is characterized by multiple basaltic lava flows, interbedded with sedimentary layers (red bole beds) representing periods of quiescence and weathering. The total thickness of the basalt pile reaches up to 2,000 meters in some areas.
Composition of the Basalts
The basalts of the DVP are predominantly tholeiitic in composition, meaning they are relatively low in silica and rich in iron and magnesium. They are characterized by a relatively uniform chemical composition, indicating a common source in the mantle. Minor elements and isotopic ratios provide further evidence for the mantle plume origin. The presence of intertrappean beds, consisting of weathered volcanic ash and sediments, provides valuable insights into the paleoclimate and environment during the volcanic episodes.
Geological Features and Associated Structures
- Dykes and Sills: Numerous dykes and sills intrude the surrounding sedimentary rocks, representing pathways for magma to reach the surface.
- Columnar Jointing: Cooling of the thick basalt flows resulted in the development of characteristic columnar jointing patterns.
- Laterite Formation: Intense weathering of the basalt in tropical conditions led to the formation of thick laterite deposits.
- Associated Mineralization: The DVP is associated with certain mineral deposits, including chromite and manganese.
The DVP also influenced the development of drainage patterns in the region, creating rift valleys and contributing to the formation of the Western Ghats. The weathering of the basalt has enriched the soils, making them fertile for agriculture.
Conclusion
The Deccan Volcanic Province stands as a remarkable geological feature, providing crucial insights into mantle plume volcanism and plate tectonics. Its formation had significant environmental consequences, potentially contributing to a major extinction event. The DVP continues to be a subject of intense research, with ongoing studies aimed at understanding its formation, evolution, and impact on the Earth system. Its unique geological characteristics and fertile soils continue to shape the landscape and economy of India.
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.