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Volcanic activity, not asteroids caused mass extinction
Publish Date : 12/1/2004 12:39:00 PM   Source : Health News Onlypunjab.com

Contradictory to the popular belief that  an
asteroid impact was the cause of the end-Permian mass  extinction
in  which  ninety percent of marine species disappeared and  life
on land suffered greatly, scientists have now found the cause  to
have emanated from Earth itself.

Led  by Christian Koeberl of the University of Vienna, a team  of
international scientists 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," Koeberl was quoted as saying.

"This suggests the mass extinction must have been home-grown," he
added.

With  the  help  of  colleagues from  the  USA  and  UK,  Koeberl
confirmed  the  presence  of  the element  iridium  in  the  rock
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.

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," Koeberl said.

"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," he added. (ANI)