When Earth Turned Bad: New Evidence Supports Terrestrial Cause Of End-Permian Mass Extinction

Two hundred and fifty million years ago, ninety percent of marine species disappeared and life on land suffered greatly during the world's largest mass extinction. The cause of this great dying has baffled scientists for decades, and recent speculations invoke asteroid impacts as a kill mechanism. Yet a new study published in the December issue of Geology provides strong indications that the extinction cause did not come from the heavens but from Earth itself.

An international team of scientists led by Christian Koeberl from the University of Vienna studied rock samples taken from deep in the Carnic Alps of southern Austria and the western Dolomites in northeast Italy. Their findings promise to fuel what is already one of the hottest debates in earth science.

"Our geochemical analyses of these two famous end-Permian sections in Austria and Italy reveal no tangible evidence of extraterrestrial impact," said Koeberl. "This suggests the mass extinction must have been home-grown."

Layers of rocks contain a chemical testimony of environmental change though time. Asteroids and comets are chemically different from the Earth and when these objects arrive they leave a tell-tale chemical fingerprint in the rocks.

With the help of colleagues from the USA and UK, Koeberl confirmed the presence of the element iridium in the samples. Iridium is abundant in asteroids, comets, and other extraterrestrial material.

However, the amounts found were very small compared to those associated with the asteroid impact that many scientists believe killed off the dinosaurs 65 million years ago. At the same time, the team found no traces of the extraterrestrial isotopes helium-3 and osmium-187, commonly associated with impact events.

What the team did find, however, was evidence of purely terrestrial processes at work. According to Koeberl, "The slight concentrations of iridium may have been deposited by sluggish oceans when atmospheric carbon dioxide levels were high and seawater oxygen levels were low. The source of the carbon dioxide was probably volcanic activity."

Large areas of Earth's crust can be split by volcanic activity to create space in which oceans form. When it comes to cracking continents, however, breaking up is very hard to do. At the close of the Permian, one such failed attempt at ocean forming led to massive volcanic activity in the heart of present day Siberia. Emissions flooded the atmosphere leading to changes in climate and patterns of oceanic circulation.

"Our findings support the view that evidence for an extraterrestrial impact event during this time period is weak and inconsistent," said Koeberl. "At the same time, they suggest that widespread volcanic activity may have been the 'smoking gun,' quite literally, that wiped out much of life on Earth."

"Geochemistry of the end-Permian extinction event in Austria and Italy: No evidence for an extraterrestrial component," GEOLOGY, December 2004, v. 32, no. 12, p. 1053-1056.

*Christian Koeberl, Dept. of Geological Sciences, University of Vienna, Vienna, Austria

*Kenneth A. Farley, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA

*Bernhard Peucker-Ehrenbrink, Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Wood Hole, MA, USA

*Mark A. Sephton, Planetary and Space Sciences Research Institute, Open University, Milton Keynes, UK

Also:

New evidence supports terrestrial cause of end-Permian mass extinction

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When Earth turned bad December 2, 2004

New evidence supports terrestrial cause of end-Permian mass extinction

Dwain Eldred writes: Two hundred and fifty million years ago, ninety percent of marine species disappeared and life on land suffered greatly during the world's largest mass extinction. The cause of this great dying has baffled scientists for decades, and recent speculations invoke asteroid impacts as a kill mechanism. Yet a new study published in the December issue of Geology provides strong indications that the extinction cause did not come from the heavens but from Earth itself.

Asteroids and comets are chemically different from the Earth and when these objects arrive they leave a tell-tale chemical fingerprint in the rocks – for example, the famous iridium-rich layer at the K/T boundary that suggests strongly that extraterrestrial impact or impacts were involved in the late Cretaceous extinction.

With the help of colleagues from the USA and UK, Koeberl confirmed the presence of the element iridium in the samples. Iridium is abundant in asteroids, comets, and other extraterrestrial material. However, the amounts found were very small compared to those associated with the asteroid impact that many scientists believe killed off the dinosaurs 65 million years ago. At the same time, the team found no traces of the extraterrestrial isotopes helium-3 and osmium-187, commonly associated with impact events.

Large areas of Earth's crust can be split by volcanic activity to create space in which oceans form. When it comes to cracking continents, however, in the words of the song breaking up is very hard to do. At the close of the Permian, one such failed attempt at ocean forming led to massive volcanic activity in the heart of present day Siberia. Emissions flooded the atmosphere leading to changes in climate and patterns of oceanic circulation.

"Our findings support the view that evidence for an extraterrestrial impact event during this time period is weak and inconsistent" said Koeberl. "At the same time, they suggest that widespread volcanic activity may have been the 'smoking gun,' quite literally, that wiped out much of life on Earth."

Reading material on that :

End Permian Volcanism

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How could the Siberian Traps cause global mass destruction?

The immediate area would be affected by such things as lava and pyrocastic flows but how does this affect the other side of the world? The real power of the Siberian Traps was the climate altering potential by the emission of ash and gases. The Siberian Traps is recognised as having a large proportion of pyroclastic deposits relative to other flood basalts. This indicates an explosive nature with much ash and gases being pumped into the atmosphere. All of this ash and gas has two main effects that, even though they are opposite to each other, act on differing timescales.

Initially sulfur aerosols and volcanic ash envelop the earths atmosphere blocking out sunlight and sending surface temperatures plunging . Ash and sulphur aerosols can remain in the upper atmosphere for 100's to 1000's of years which would be enough to cause a significant glaciation. At the end of the Permian period the biggest ever drop in sea level in history occurred. Two scientists named Holser and Magaritz in 1987 proposed that such a marine regression could be caused by a large scale glaciation.

The second major effect is the emission of greenhouse gases such as CO2, methane and also water vapour. Green house gases warm the climate by allowing sunlight to pass through, heat reflected by the Earth itself cannot penetrate the atmosphere so is retained. Greenhouse gases stay in the atmosphere much longer so their climate changing effects can last for millions of years.

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Another minor effect is the destruction of the ozone layer caused by gas emissions. Chlorine and fluorine gases are erupted from almost all volcanic eruptions and these destroy the ozone layer. Without the ozone layer, harmful UV rays can kill organisms therefore contributing to a mass extinction.

There is a recent report that tracking satellites as they pass over Antarctica reveals reduced gravity at one locality. This is evidence that below the icecap is a crater. The ice filling the crater masses less than bedrock would have.

This crater would have been formed by an impact much larger than the one that got the dinosaurs. THAT impact was antipodal to the Deccan traps of India. The shock of the impact went right through the earth and was focused on the other side, blowing out a large region of the crust in India. Hence, the lava flows there.

Now, Siberia is antipodal to Antarctica, or near enough when we consider that continents drift. So wouldn't it make sense that the Siberian traps were the result of a similar shock wave from that larger impact that formed the Antarctic hidden crater?

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