Does Mass Volcanism Equal Mass Extinction?

It is now generally accepted that the meteorite that caused the Chicxulub crater in Mexico 66 million years ago was responsible for the extinction of the dinosaurs; indeed half of the species that were alive at the time. What is by no means clear, however, is if it was just this or if the impact caused an increase in volcanism that contributed to the hardships of the planet’s populous.

New research published in Science has tried to shed some light on this. They tested multiple rock samples from India’s Deccan Traps, a region known to be of highly significant volcanic activity at approximately the same time as the meteorite impact. It was already known that eruptions in the area had begun several millions years before the impact, but there is evidence that the rate doubled contemporaneously. What is needed, then, is an accurate measure of exactly when this happened. A previous analysis had shown that the two occurred within 100,000 years of each other, the new paper narrows that to 50,000 years and they now plan to do future work with an aim to showing that they happened within 5,000 years of each other – if indeed that is what happened.

Something to bear in mind is that, even if they were able to show that the meteorite strike and the doubling in eruptions happened on the very same Tuesday afternoon, it wouldn’t necessarily mean that the former caused the latter nor that the vulcanism was significant enough to have contributed to a worldwide extinction event. Also, if they were found to have occurred simultaneously, how would you test the proportion to which they both contributed? The one throws up huge amounts of dust and gas into the air which causes the sun to be blotted out resulting in less light and cooler temperatures, and the other causes exactly the same conditions; it’s an inherently untestable hypothesis. This doesn’t mean that we shouldn’t try; we may never be able to prove cause and effect but an ever tighter correlation would certainly be interesting and give us a richer understanding of the conditions prevalent at the time.

Image by Don Davis, used with permission
Image by Don Davis, used with permission

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