A groundbreaking new study into the Chicxulub asteroid impact 66 million years ago proves the space rock created a world too inhospitable for dinosaurs to survive in. The asteroid, which struck the Earth off the coast of Mexico at the end of the Cretaceous era, has long been suspected to be the cause of the demise of all dinosaur species except those that evolved into birds.
However, some researchers had suggested tens of thousands of years of large volcanic eruptions may have been the real cause of the extinction event, calculated to have killed almost 75 percent of life on Earth.
Essentially, it produces a blue screen of death for dinosaurs
Dr Philip Mannion
Now, a research team from Imperial College London, the University of Bristol and University College London has confirmed only the asteroid impact could have created the brutal climate unfavourable for dinosaurs across the globe.
They also reveal the massive volcanism could also have helped life recover from the asteroid strike in the long-term.
Lead researcher Dr Alessandro Chiarenza, of the Department of Earth Science and Engineering at Imperial, said: “We show that the asteroid caused an impact winter for decades, and that these environmental effects decimated suitable environments for dinosaurs.
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“In contrast, the effects of the intense volcanic eruptions were not strong enough to substantially disrupt global ecosystems.
“Our study confirms, for the first time quantitatively, that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide.”
The asteroid strike would have released particles and gases high into the atmosphere, blocking out the Sun for years, triggering permanent winters.
But volcanic eruptions also produce particles and gases with Sun-blocking effects, and around the time of the mass extinction, there were tens of thousands of years of eruptions at the Deccan Traps, in present-day India.
To determine which factor, the asteroid or the volcanism, had more climate-changing power, researchers have traditionally used geological markers of climate and powerful mathematical models.
The new study combined these methods with information about what kinds of environmental factors, such as rainfall and temperature, each species of dinosaur needed to thrive.
They were then able to map where these conditions would still exist in a world after either an asteroid strike or massive volcanism.
The science discovered only the asteroid strike wiped-out all potential dinosaur habitats, while volcanism left some viable regions around the equator.
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Dr Alex Farnsworth, from the University of Bristol and co-lead author of the study, said: “Instead of only using the geologic record to model the effect on climate that the asteroid or volcanism might have caused worldwide, we pushed this approach a step forward, adding an ecological dimension to the study to reveal how these climatic fluctuations severely affected ecosystems.”
Dr Philip Mannion, from University College London and another co-author, added: “In this study we add a modelling approach to key geological and climate data that shows the devastating effect of the asteroid impact on global habitats.
“Essentially, it produces a blue screen of death for dinosaurs.”
Although volcanoes release Sun-blocking gases and particles, they also release carbon dioxide, a greenhouse gas.
In the immediate aftermath of an eruption, the Sun-blockers have a larger effect, causing a ‘volcanic winter’.
However, in the longer-term these particles and gases fall from the atmosphere, while carbon dioxide remains and builds up, warming the planet.
After the initial cataclysmic global winter caused by the asteroid impact, the team’s model suggests volcanic warming could have helped restore many habitats in the longer term.
This would have helped new life that evolved after the disaster to thrive.
Dr Chiarenza said: “We provide new evidence to suggest that the volcanic eruptions happening around the same time might have reduced the effects on the environment caused by the impact, particularly in quickening the rise of temperatures after the impact winter.
“This volcanic-induced warming helped boost the survival and recovery of the animals and plants that made through the extinction, with many groups expanding in its immediate aftermath, including birds and mammals.”
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