A volcanic cause for the extinction of the dinosaurs?
New research from Princeton University, New Jersey, has produced the most accurate estimate so far for the age of the Deccan Traps in India. These enormous outpourings of lava, now preserved as basalt, are thought to have occurred near the end of the Cretaceous, coinciding with the extinction of the dinosaurs but this has long been disputed. These new findings narrow the date of these eruptions, revealing them to have been far more abrupt and potentially more devastating than previously realised.
The most widely accepted theory, based on a wealth of scientific evidence, is that a gigantic asteroid impacted the Earth around 66 million years ago. This event is thought to have triggering catastrophic climate change, thereby bringing about the extinction of 70% of all life on Earth.
However, not all scientists have accepted this explanation and those that disagree have often looked to volcanism as an alternative. At their largest extent it’s estimated that the Deccan Traps covered an area three times the size of France although erosion has long since reduced them to around 500,000km2. Until now it wasn’t clear exactly when these floods erupted, or how long the eruption lasted. The team from Princeton used a method called uranium-lead dating which measures the ratios of these elements in a sample. Since it is known how long it takes for uranium to decay into lead and this rate is constant, it is possible to calculate how old a sample is based on the current ratio. The results were compelling and showed that the Deccan Traps first started erupting around 250,000 years before the end-Cretaceous event and continued for the next 750,000 years, releasing 1.1 million cubic kilometres of lava.
This eruption would have been constantly pumping carbon dioxide and sulphur dioxide into the atmosphere, with potentially catastrophic consequences for climate and life on Earth. Previous work had suggested a timeline two to three times longer for these eruptions which would have reduced the impact of these volcanic gases on climate and ocean acidity. These new results suggest that the Deccan Traps could have been radically altering the climate at exactly the time that we see the extinction the dinosaurs.
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