Y: The end-Cretaceous extinction is Earth’s greatest murder mystery. Sixty-six million years ago, something killed about seventy-five percent of all animals, including the dinosaurs. About that time, the Earth was struck by an asteroid that blasted the ninety-three mile diameter Chicxulub crater. Remnants of the crater were found in the Gulf of Mexico. Most scientists think environmental effects of this impact caused the mass extinction event.
D: Yes, Yaël, but there’s also another suspect. Around the same time as the impact, there were huge volcanic eruptions in what is now India, producing vast lava flows the size of France called the Deccan Traps. They released sulfate gases which may have caused short-term cooling and acidification of the oceans and greenhouse gases which, some scientists argue, might have killed the dinosaurs through long-term catastrophic global warming. There is strong evidence linking other mass extinctions to volcanoes. Volcanic activity may be a serial killer.
Y: Maybe not, Don. In 2020 two teams of geoscientists published new studies that may exonerate the Deccan Traps eruptions. The researchers combined data on the occurrence of dinosaur fossils with climate and ecological modeling. They conclude that the Chicxulub impact would have propelled gigatons of sulfates into the stratosphere, causing subfreezing global temperatures for years or decades. This would account for observed extinctions in a vast array of different ecologies. The researchers conclude that the volcanic eruptions couldn’t have done this deed, on the short timescale of the extinction. By warming the climate on a longer timescale, they may have actually helped life on Earth recover from the catastrophe.
D: Although there are still unknowns, I’ll admit that, probably, the asteroid did it.