Friday, December 02, 2005

Permian Extinction Caused by Vulcanism

The world's largest mass extinction was probably caused by poisonous volcanic gas, according to research published today.

The research, published in the journal Geology, reveals vital clues about the mass extinction at the end of the Permian period, 250 million years ago, when mammal-like reptiles known as synapsids roamed the earth.

Many scientists had previously thought that an asteroid hitting the earth or a deep-sea methane release had caused the extinction, which obliterated more than two-thirds of reptile and amphibian families.

However, analysis of a unique set of molecules found in rocks taken from the Dolomites in Italy has enabled scientists to build up a picture of what actually happened. The molecules are the remains of polysaccharides, large sugar-based structures common in plants and soil, and they tell the story of the extinction.

The molecules date from the same time as a major volcanic eruption that caused the greatest ever outpouring of basalt lava over vast swathes of land in present day Siberia.

The researchers believe that the volcanic gases from the eruption, which would have depleted earth's protective ozone layer and acidified the land and sea, killed rooted vegetation. This meant that soil was no longer retained and it washed into the surrounding oceans.

Read the rest here.

What I have always found interesting when people study extinctions is that there is always an attempt to find a single reason for all of the extinctions rather than studying each individually. Perhaps that is just because the asteroid killer guys were one of the first ones I was exposed to with the related hypothesis of 'Nemesis' or the other extinction theorists were reacting to affore mentioned group, I don't know. Or I am just really misunderstanding the whole debate (always possible, it's not my area of expertise).

What's interesting is that in one case, the KT Event that ended the Age of Dinosaurs, might have only been a good case of bad timing. There is some evidence that the dinos were suffering a bit at the end of the Cretaceous. The numbers and variety of dinosaurians had been dropping according to some of the paleontological sites. Some people have put forward that the dinosaurs were already going extinct. What seems more likely to me was that the dinos were in the midst of not going extinct so much as going through of their 'minor' extinction events. They had some during the Cretaceous, a whopper in the end of the Jurassic, and another couple whoppers in the Triassic. The timing of the asteroid might have just been 'right' to kill them off.

If it had come when the dinos were more vibrant, it might not have had the same impact...


No pun intended.

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