Scientists are still debating to this day what actually happened to dinosaurs about 65 million years ago. A study published in the journal, Science, has put an end to this controversy by ruling out volcanism as the cause of extinction of most species at the end of the Cretaceous era. It wasn’t a major volcanic eruption in India but one single asteroid which brought the age of the dinosaur to an end 66 million years ago. The asteroid was about 10 km in diameter, that crashed into what is now the Yucatan Peninsula (Mexico), triggering the disappearance of 75% of existing species, including almost all dinosaurs.
Traps of the Deccan
The international team of researchers, led by geologist and geophysicist Pincelli Hull of Yale University (USA), are clear in their conclusions: the environmental impact of India's massive volcanic eruptions in the region known as the Deccan rips (or Deccan stairs) took place before the Cretaceous-Paleogene extinction, 66 million years ago, and therefore did not contribute to the mass extinction in that era.
In fact, the eruptions of the Deccan rhapsodies spewed out up to 500,000 cubic kilometres of lava over much of what is now western India. But the real killer of the dinosaurs would not have been lava, but volcanic gases - carbon dioxide that warms the planet or sulphur dioxide that acidifies the oceans.
"Volcanoes can cause mass extinctions because they release many gases, like SO2 and CO2, that can alter the climate and acidify the world, but the recent study has focused on the timing of lava eruption rather than the release of gases," said Hull, the study's leader. And it happened before the mass extinction event, so it didn't have a direct effect on their death.
Travelling to the past
Data on global ocean floor sediment temperatures and carbon isotopes combined with computer simulations of ocean carbon cycle change supported the hypothesis that an impact from a large asteroid, and not toxic gases emitted by massive eruptions, was primarily responsible for such mortality (about three-quarters of the Earth's plant and animal species disappeared).
"Volcanic activity in the late Cretaceous era led to a gradual global warming event of about two degrees, but not mass extinction," said former Yale researcher Michael Henehan, who compiled the temperature records for the study. "Several species moved to the North and South Poles but regressed long before the impact of the asteroid.
"Many have speculated that volcanoes are important to K-Pg, and we're saying, no, they weren't," Hull said.
Sediment deposits linked to the impact of a giant asteroid form a layer known as the "Kpg" boundary, as it marks the transition from the Cretaceous to the Paleogene period (beginning 66 million years ago and ending 23 million years ago).
We can now confirm that the asteroid was the sole driver of the extinction.
Reference: P.M. Hull et al. “On impact and volcanism across the Cretaceous-Paleogene boundary” Science 16 de enero de 2020