Scientists were still debating to this day what happened to most 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 a trigger for the extinction of most species at the end of the Cretaceous. It was only an asteroid of about 10 km in diameter, which crashed in what is now the Yucatan Peninsula (Mexico), triggering the disappearance of 75% of existing species, including almost all dinosaurs.
Deccan Traps
The international team of researchers led by geologist and geophysicist Pincelli Hull from Yale University (USA) is clear in its conclusions: the environmental impact of massive volcanic eruptions in India in the region known as the traps of the Deccan (or Deccan stairs) took place before the Cretaceous-Paleogene extinction event 66 million years ago and therefore did not contribute to the mass extinction in that era.
In fact, eruptions from the Deccan traps dumped up to 500,000 cubic kilometers of lava across 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 sulfur dioxide that acidifies the oceans.
“Volcanoes can cause mass extinctions because they release many gases, such as SO2 and CO2, that can alter the climate and acidify the world, but the recent study has focused on the timing of the lava eruption rather than the release of gases. “, clarified Hull, leader of the study. And it happened before the mass extinction event, so it had no direct effect on his death.
Traveling to the past
Data on global temperatures of ocean floor sediments – spanning several hundred thousand years before, during and after the extinction event – and carbon isotopes (atoms with a higher or lower number of neutrons than normal), combined with computer simulations of the change of the carbon cycle in the ocean, they supported the hypothesis that an impact of a large asteroid and non-toxic gases emitted by massive eruptions, was the main responsible for such mortality (about three quarters of plant and animal species on Earth).
“Volcanic activity in the late Cretaceous led to a gradual global warming event of about two degrees, but not a mass extinction,” said former Yale researcher Michael Henehan, who compiled temperature records for the study. “Several species moved towards the North and South poles, but they retreated 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.
The 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).
Now we can say that the asteroid was the only driver of the extinction.
Referencia: P.M. Hull et al. “On impact and volcanism across the Cretaceous-Paleogene boundary” Science 16 de enero de 2020
