[meteorite-list] Doubt Cast on Global Firestorm Generated by Dino-Killing Asteroid

[Ron Baalke]

http://www.exeter.ac.uk/news/featurednews/title_430274_en.html

Doubt cast on global firestorm generated by dino-killing asteroid
University of Exeter
January 22, 2015

Pioneering new research has debunked the theory that the asteroid that 
is thought to have led to the extinction of dinosaurs also caused vast 
global firestorms that ravaged planet Earth.

A team of 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.

Dr Claire Belcher from the Earth System Science group in Geography at 
the University of Exeter said: "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. 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."  

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.

Dr Rory Hadden from the University of Edinburgh said: "This is a truly 
exciting piece of inter-disciplinary research. By working together engineers 
and geoscientists have tackled a complex, long-standing problem in a novel 
way. This has allowed a step forward in the debate surrounding the end 
Cretaceous impact and will help geoscientists interpret the fossil record 
and evaluate potential future impacts. In addition, the methods we developed 
in the laboratory for this research have driven new developments in our 
current understanding of how materials behave in fires particularly at 
the wildland-urban-interface,  meaning that we have been able to answer 
questions relating to both ancient mass extinctions at the same time as 
developing understanding of the impact of wildfires in urban areas today."

The results of the study are published in the Journal of the Geological 
Society.

The research was supported by a European Research Council Starter Grant, 
a Marie Curie Career Integration Grant, the Leverhulme Trust, the EPSRC 
and the Austrian Science Fund.


[Video]
Flaming ignition of dry plant material.


The researchers found that close to the impact site, the heat pulse was 
too short to ignite live plant material.