Monday, October 19, 2009

Getting rid of the Dinos

Have a dinosaur infestation?, need the problem solved quickly. What is the answer?. Well one option is to drop an enormous rock on the little blighters from orbit. And in fact there is a star candidate for this in the Chicxulub impact event. This would have hit with the force of 100,000,000 megatons of TNT on impact, unleashing mega tsunamis and dousing the earth in acid rain. That should deal with them shouldn’t it?. Well no, not according to Gerta Keller of Princeton University in New Jersey, and Thierry Adatte of the University of Lausanne, Switzerland. In a recent analysis they used evidence from Mexico to suggest that the Chicxulub impact predates the K-T boundary extension event by as much as 300,000 years and that it wasn’t a significant enough blow to species diversity.

Also at El Peñon, the researchers found 52 species present in sediments below the impact layer and counted all 52 still present in the layer above it, indicating that the impact has not had the devasting biotic effect on species diversity as has been suggested. "Not a single species went extinct as a result of the Chicxulub impact," Keller said. In contrast, she noted, at a nearby site known as La Sierrita where the K-T boundary, iridium anomaly and mass extinction are recorded, 31 out of 44 species disappeared from the fossil record at the K-T boundary.

Instead, Gerta Keller argues, the dinosaurs must have been taken out by killer volcanos. She speculates that massive volcanic eruptions at the Deccan Traps in India may be responsible for the extinction, releasing huge amounts of dust and gases that could have blocked out sunlight and brought about a significant greenhouse effect. The volcanos would have resulted in half a million cubic miles of lava flooding the western part of India in a short amount of time.

But there’s another solution. How about an even more enormous rock lobbed at the unsuspecting dinos,which would put paid to them once and for all. That is the theory of Paleontologist Sankar Chatterjee of Texas Tech University who argues that a basin called Shiva in India, is really an enormous impact crater. The rock in question would have been 40 kms wide (three times the size of KT) and hurtled towards Earth at 58,000 miles per hour. This would have had 10,000 times more force than the detonation of the world’s entire nuclear arsenal and placed the world into perpetual night for more than a year. Seems like a prime candidate, however the volcanoeists are not happy. Keller remarks:

"We have worked extensively throughout India and investigated a number of the localities where Sankar Chatterjee claims to have evidence of a large impact he calls Shiva crater," Keller wrote in an e-mail along with colleague Thierry Adatte of Switzerland's Universite de Neuchâtel. "Unfortunately, we have found no evidence to support his claims... Sorry to say, this is all nonsense."

What would have happened if the asteroid had missed. Well, contrary to popular belief, these mass extinction events tend to speed up evolution rather than alter its overall course. The first period of evolutionary expansion among the mammals was an event 100-85 million years ago when the extant orders first appeared. Modern placental lineages were therefore present at the time of the dinosaurs. Does that mean that even without dinosaur extinction they would have carried on evolving into the types of large mammals that we see around today?. At first sight seems unlikely but recent research – that of Paul Barrett in the Proceedings of the Royal Society – is showing:

‘for the first time that the number of different types of dinosaur was declining well before their final extinction, in spite of the fact the amount of rock available for preserving dinosaurs was at its peak.

'The impact may have been the coup de grace that helped to finish off a group that was already in trouble for another reason.'

The mammals were on their way up, the Dinos were on their way down. Giant rocks from the sky don’t help though.

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