London: A pioneering new research has debunked the theory that the asteroid that is thought to have led to the extinction of dinosaurs 66 million years ago also caused vast global firestorms that ravaged planet Earth. Researchers from the University of Exeter, University of Edinburgh and Imperial College London recreated the immense energy released from an extra-terrestrial collision with Earth that occurred around the time that dinosaurs became extinct.
They found that the intense but short-lived heat near the impact site could not have ignited live plants, challenging the idea that the impact led to global firestorms.
These firestorms have previously been considered a major contender in the puzzle to find out what caused the mass extinction of life on Earth 65 million years ago. The researchers found that close to the impact site, a 200 km wide crater in Mexico, the heat pulse – that would have lasted for less than a minute – was too short to ignite live plant material. However, they discovered that the effects of the impact would have been felt as far away as New Zealand where the heat would have been less intense but longer lasting – heating the ground for about seven minutes – long enough to ignite live plant matter.
The experiments were carried out in the laboratory and showed that dry plant matter could ignite, but live plants including green pine branches, typically do not. “By combining computer simulations of the impact with methods from engineering we have been able to recreate the enormous heat of the impact in the laboratory,” Dr Claire Belcher from the Earth System Science group in Geography at the University of Exeter said. “This has shown us that the heat was more likely to severely affect ecosystems a long distance away, such that forests in New Zealand would have had more chance of suffering major wildfires than forests in North America that were close to the impact.
“This flips our understanding of the effects of the impact on its head and means that palaeontologists may need to look for new clues from fossils found a long way from the impact to better understand the mass extinction event,” said Belcher. Plants and animals are generally resistant to localised fire events – animals can hide or hibernate and plants can re-colonise from other areas, implying that wildfires are unlikely to be directly capable of leading to the extinctions.
If however some animal communities, particularly large animals, were unable to shelter from the heat, they may have suffered serious losses. It is unclear whether these would have been sufficient to lead to the extinction of species. The study was published in the Journal of the Geological Society.