Model Answer
0 min readIntroduction
The Deccan Volcanic Province (DVP), a large igneous province, represents one of the largest volcanic features on Earth. Formed during the late Cretaceous and early Paleogene periods, approximately 66 million years ago, it covers a vast area of western and central India. The DVP is primarily composed of basaltic lava flows, and its formation is closely linked to the Cretaceous-Paleogene (K-Pg) extinction event, though the exact nature of this link remains a subject of ongoing research. Understanding the DVP is crucial for comprehending the geological evolution of the Indian subcontinent and its impact on the environment.
Geological Setting
The DVP is situated on the Indian tectonic plate, which was then part of the supercontinent Gondwana. During the late Cretaceous, India was undergoing rifting as it separated from Madagascar. This rifting created pathways for magma to ascend from the mantle. The region was characterized by a shallow marine environment and a pre-existing continental crust. The formation of the DVP is attributed to the Reunion hotspot, a mantle plume that initiated extensive volcanism.
Volcanic Activity & Chronology
The volcanic activity occurred in three distinct phases:
- Early Phase (66-65 Ma): Characterized by relatively small-volume eruptions and the formation of initial basalt flows.
- Main Phase (65-63 Ma): This phase witnessed the most voluminous eruptions, resulting in the formation of the majority of the basalt flows. The eruption rate was exceptionally high, with estimates suggesting lava flows covering areas equivalent to several states in India.
- Late Phase (63-60 Ma): Marked by a decrease in eruption volume and the development of associated intrusive features like dykes and sills.
The eruptions were predominantly fissure eruptions, leading to the formation of extensive lava plateaus rather than steep volcanic cones. The total volume of lava erupted is estimated to be around 1.5 million cubic kilometers, making it one of the largest volcanic provinces in the world.
Petrology & Composition
The DVP is predominantly composed of basaltic lava flows, with minor amounts of andesite and rhyolite. The basalt is typically tholeiitic in composition, characterized by low alkali and high magnesium content. The lava flows exhibit varying textures, including vesicular, porphyritic, and aphanitic, reflecting different cooling rates and gas content. Chemical analysis reveals that the magma originated from a deep mantle source, with minimal contamination from the continental crust.
Associated Features
Besides the extensive basalt flows, the DVP is associated with several other geological features:
- Dykes and Sills: Intrusive features formed by the injection of magma into pre-existing fractures and layers.
- Columnar Jointing: A characteristic feature of basaltic lava flows, formed due to contraction during cooling.
- Laterite Formation: Intense weathering of the basaltic rocks has led to the formation of thick laterite deposits, rich in iron and aluminum.
- Intertrappean Sediments: Sedimentary layers deposited between successive lava flows, containing fossils of plants and animals, providing insights into the paleoenvironment.
Geological Significance
The DVP holds significant geological importance:
- K-Pg Extinction Event: The massive volcanic eruptions released large amounts of greenhouse gases (CO2, SO2) and aerosols into the atmosphere, potentially contributing to climate change and the K-Pg extinction event, which wiped out the dinosaurs. However, the extent of its contribution is still debated.
- Continental Breakup: The volcanism is linked to the breakup of Gondwana and the initiation of the Indian Ocean.
- Fertile Soils: Weathering of the basaltic rocks has resulted in the formation of fertile black cotton soils (Regur soils), which are ideal for agriculture.
- Groundwater Resources: The porous nature of the basaltic rocks allows for the accumulation of groundwater, providing a vital water resource for the region.
Recent studies using high-precision geochronology have refined the timing of the DVP eruptions, suggesting a more rapid and concentrated period of volcanic activity than previously thought. This has implications for understanding the relationship between the DVP and the K-Pg extinction event.
Conclusion
The Deccan Volcanic Province stands as a remarkable geological feature, offering a window into the Earth’s dynamic past. Its formation, linked to mantle plume activity and continental breakup, profoundly impacted the Indian subcontinent’s geological evolution, climate, and biodiversity. Ongoing research continues to unravel the complexities of the DVP, particularly its role in the K-Pg extinction event, and its legacy continues to shape the landscape and resources of western and central India.
Answer Length
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