Global Geological And Climatic Events

Evidence of High Rainfall during Deccan Traps Volcanism


From UPSC perspective, the following things are important :

Prelims level: NanoSIMS

Mains level: Not Much


Central Idea

  • A team of scientists from IIT Kharagpur has discovered evidence of exceptionally high annual rainfall during the volcanic activity that formed the Deccan Traps in India around 66 million years ago.
  • Using a new technique called Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS), the researchers analyzed the isotopic composition of fossil trees from the Cretaceous period.
  • They determined the isotopic composition of the rainfall-derived lake water.

Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS)

  • NanoSIMS is an advanced analytical technique to determine the composition and distribution of elements and isotopes at a microscopic scale.
  • It allows for high-resolution imaging and quantitative analysis of samples.
  • The technique involves bombarding the sample surface with a focused beam of primary ions.
  • This causes the ejection of secondary ions from the sample surface.
  • The secondary ions are collected and analyzed using a mass spectrometer.
  • The mass spectrometer separates the ions based on their mass-to-charge ratio and measures their abundance.

Analysis and Findings

  • New Technique: The team used Nanoscale Secondary Ion Mass Spectrometry to analyze oxygen isotopes in fossil trees and measure the isotopic composition of the lake water derived from rainfall.
  • Depleted Oxygen Isotopes: The analysis revealed depleted oxygen isotope values, indicating higher tropical rainfall in India during the terminal Cretaceous period.
  • Link to Paleoclimatic Changes: The increase in rainfall closely corresponded to changes in paleo-atmospheric carbon dioxide levels, suggesting a potential underlying link between the two.

Implications and Comparison

  • Atmospheric Carbon Dioxide Concentration: The eruption of Deccan Trap lavas released a significant amount of carbon dioxide, raising atmospheric levels to as high as 1,000 ppm.
  • Comparison to Modern Rainfall: The data from fossil trees indicated an annual rainfall of 1,800-1,900 mm, exceeding the average modern rainfall of 1,000-1,200 mm in most parts of peninsular India.
  • Climate Change Predictions: The findings align with predictions made by the Intergovernmental Panel on Climate Change (IPCC) for extreme warming scenarios, suggesting a correlation between high carbon dioxide levels and increased rainfall.

Climate Models and Future Projections

  • Rising Carbon Dioxide Levels: Fossil fuel emissions have raised carbon dioxide levels from 280 ppm to about 420 ppm in 2023.
  • Impact on Rainfall: Climate models indicate that doubling carbon dioxide levels will intensify atmospheric circulation and subsequently increase rainfall.
  • IPCC AR6 Report: The report warns of a significant increase in the wettest day precipitation and tropical cyclone-associated rainfall if carbon dioxide emissions continue to rise unabated.


  • The study provides evidence of high rainfall during the volcanic activity that formed the Deccan Traps in India millions of years ago.
  • The findings suggest a correlation between elevated carbon dioxide levels and increased rainfall, supporting predictions made by climate models for future climate change scenarios.


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