The Late Cretaceous period was not an easy time for life on Earth. It was marked by intense volcanic activity and ended with a cataclysmic asteroid impact. The eventual mass extinction that concluded the period, known as the K-Pg event, has been seen by some as a product of both these factors, but new research points at the space rock as the sole culprit.
The asteroid led to the demise of the dinosaurs as rulers of the Earth and the extinction of 75 percent of all plant and animal species on our planet, according to an international team. The work published in Science modeled changes in temperature and the carbon cycle providing evidence that major volcanic activity had already ended by the time the asteroid hit what is now Mexico.
“Most scientists acknowledge that the last, and best-known, mass extinction event occurred after a large asteroid slammed into Earth 66 million years ago, but some researchers suggested volcanic activity might have played a big role too and we’ve shown that is not the case,” co-author Professor Paul Bown, from University College London, said in a statement.
The team focused on the effects of the vast volcanic eruption in India that formed the Deccan Traps, one of the largest volcanic features on Earth. The dramatic event changed our planet. Sulfur dioxide and carbon dioxide altered the climate and helped acidify the world. The temperature rose by about 2°C (3.6°F).
This certainly would have affected organisms on land but fossil evidence shows that it did not affect the marine ecosystem dramatically. The climate went back to the cooler conditions that occurred long before the K-Pg event. The volcanic gas emissions were pinpointed by the team as having happened 200,000 years before the asteroid impact.
“A lot of people have speculated that volcanoes mattered to the K-Pg event, and we’re saying, ‘No, they didn’t,’” said lead author Dr Pincelli Hull from Yale University.
But the activity of the Deccan Traps was not just a prelude to the asteroid hitting Earth. Recent work suggests that the region experienced major eruptions once again after the impact, although no warming event was associated with them this time around.
The researchers have an explanation for that as well. The effect of the collision with the asteroid was so dramatic that it changed the global carbon cycle, allowing the oceans to become incredible carbon sinks. In their opinion, this hid the warming effects of volcanism and contributed to the cooling of our planet that eventually led to the evolution of life we see today.