Volcanologists from The Open University have found evidence of repeated, persistent volcanic eruptions in India 65 million years ago that provide a plausible alternative explanation for global environmental deterioration at this time, and may have been a trigger for the associated mass extinction.
In a paper published in the prestigious US magazine Science titled: Sulfur and Chlorine in Late Cretaceous Deccan magmas ,and eruptive gas release, the OU team consisting of Stephen Self, Stephen Blake, Kirti Sharma, Mike Widdowson and Sarah Sephton found the volumes of eruptions in northwest India known as the Deccan Traps were so massive that the potential environmental pollution by the gases released were immense, and on a scale unparalleled by any historic basaltic eruptions. Data shows an annual flux of at least 300 – 500 million tonnes of sulphur dioxide into the ancient atmosphere and, they argue, that this would have persisted for years if not decades. Larger flows, erupted more rapidly, could have generated even greater amounts.
This delivery of gas is two to three times greater than the current global industrial output (about 150 million tones) and, because of its sustained nature and delivery into the high atmosphere, is likely to have had serious effects upon Late Cretaceous environments and climate.
The OU team gathered hundreds of samples from the Deccan Traps, and found that in just a few they could derive the ancient original gas content by cutting thin slices of rock to find pockets of glass. It was these tiny, rare glass inclusions that had ‘frozen in’ the original sulphur and chlorine contents of the lavas that the team have managed to measure.