The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal

30 November 2004 - The world’s largest mass extinction may have been caused by Earth’s own volcanoes, according to a study published in the December issue of Geology. New evidence contradicts the earlier view that an asteroid wiped out 90 percent of marine life at the end of the Permian period, 248 million years ago.

Christian Koeberl of the University of Vienna and an international team of scientists studied rock samples from the Dolomites and the Carnic Alps of Italy and Austria. They found that the elements and compounds deposited in these late-Permian rocks were more similar to Earth rocks than to extraterrestrial rocks.

“Our geochemical analyses [of late-Permian rocks] reveal no tangible evidence of extraterrestrial impact," said Koeberl.

Asteroids are chemically different from Earth rocks and leave a “fingerprint” when they land; for example, high levels of iridium are commonly associated with asteroid impacts. Koeberl and colleagues found very little iridium in their rock samples, and no traces of the isotopes helium-3 and osmium-187 that are also associated with asteroids.

The scientists did find evidence of high levels of carbon dioxide, likely caused by volcanic activity. Near the end of the Permian period, tension in the Earth’s crust in present day Siberia led to massive volcanic activity in the region. According to a Geological Society of America press release, emissions from those volcanoes could have caused changes in the atmosphere and ocean circulation, leading to mass extinction.

According to Koeberl, “Our findings . . . suggest that widespread volcanic activity may have been the 'smoking gun,' quite literally, that wiped out much of life on Earth.”

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