An asteroid impact did not cause the "Great Dying", when most of Earth's species became extinct 250 million years ago, scientists say.

Two new studies suggest high temperatures, toxic gases and low oxygen levels caused by volcanic activity were to blame.

The Great Dying, the Permian-Triassic extinction, is considered the biggest catastrophe in the history of life on Earth, with 90 per cent of all marine life and almost three quarters of land-based life becoming extinct. Many more species were wiped out than disappeared in the mass extinction at the end of the Cretaceous period, 65 million years ago, that saw off the dinosaurs.

Evidence has been building that the impact of a comet or asteroid triggered the extinction. But two teams point to an alternative culprit - global warming triggered by greenhouse gases from volcanoes.

"The marine extinction and the land extinction appear to be simultaneous, based on the geochemical evidence we found," says Peter Ward of the University of Washington, Seattle, the head of one team. "Animals and plants on land and in the sea died at the same time, apparently from the same causes - too much heat and too little oxygen."

The researchers used chemical, biological and magnetic evidence to correlate sediments in the Karoo Basin of South Africa to similar layers in China.

Karoo fossils disclosed two patterns, one showing gradual extinction over 10 million years leading to a sharp increase in extinction rate that lasted another five million years. Evidence from the marine extinction is "eerily similar" to what researchers found in Karoo, Dr Ward said. But the team found nothing in the Karoo to indicate an asteroid collision.




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I've written an article about this a few years ago. The shifting of the tectonic plates creates(among other things) the volcanic activity that causes the greenhouse effect.
One only has to look at the layers of earth from about 65 million years ago to layers a few million years ealier to determine that species were already dying off.

I've always viewed the asteroid vs. volcanos debate as slighty humorous. Considering that the Earth's crust consists of plates floating on molten rock, a powerful blow like an asteroid strike could easily create enough pressure to increase volcanic activity. I don't believe we're looking at an either-or scenario.

The theory I've found most interesting is that the fossil record shows the diversity of life was already declining before the asteroid strike/volcanic outburst and this only exacerbated the situation, whether part of a natural cycle or natural disaster.

Gee Homer you beat me to it!

I'm quick for an old man

I agree with you, and that I don't think it's an either-or scenario.
I actually believe the asteroid sped up the mass extinction, but didn't cause it.

Sort of like you're dying of an incurable disease, getting weaker with each passing hour, and someone shoots you dead. All it did was quicken the inevitable. I could be wrong, but that has been the theory I believed in for years.

This is indeed very interesting and I always thought that the asteroid was the sole cause of the mass extinction and not just another factor that sped up the dying off which had already started!

I always thought the combination of these.

A asteroid hits earth causing more volcanic eruptions and that combined caused extinction.
Like PinkPhantom said.

I've heard the same... that it was a combination. The asteroid hits the Earth and then causes some funky weather and volcanos to errupt and such.

Although I had always subscribed to asteroid theory it lack some substance. If an asteroid was large enough to cause global damage (like blotting out sun) etc etc then it is also possible it would throw Earth out of Orbit or some other reaction that would not only destroy life but planet itself. Now an asteroid strike that cause a chain reaction like mentioned makes more sense. I have now changed my belief and subscribe to both as one causeing the other. Asteroid strikes Earth and cause massive volcanic reactions which in turn cause greenhouse effect that destroys a good portion of life on planet at that time.

I have a theory

It was the NWO, putting its plan into motion by enabling ape to evolve into human, thus allowing the NWO a chance to conquer our world!

But that isn't the case. If you look at the fossile records, as I and PinkPhantom mentioned, the asteroid didn't cause the volcanic chain reaction, as the species were already dying off. The asteroid sped up the extinction, but didn't cause it or didn't cause the chain reaction.