Volcanic eruptions triggered mass extinctions, climate change

June 5th, 2009 - 1:41 pm ICT by IANS  

Sydney, June 5 (IANS) Massive volcanic eruptions in ancient times triggered rapid climate change and mass extinctions, by ejecting colossal volumes of greenhouse gases into the atmosphere.
“We have carefully dated minerals contained in the volcanic rocks and shown that only the fastest sequences of eruptions caused significant species extinctions,” said Fred Jourdan of Curtin University, Australia.

“To understand the long-term climatic and biological effects of the massive injections of greenhouse gas in the atmosphere by modern society we have to understand how climate was affected in the past.”

For years, a controversy has raged about whether mass extinctions over the last 550 million years were caused by the impact of giant asteroids or by huge volcanic eruptions.

“Both mechanisms can release a colossal amount of greenhouse gases. The key to discriminate between these two possibilities is to see if there is a link between the timing of mass extinctions and geological events.”

Using radioactive dating techniques, Jourdan and his colleagues determined the age, duration and rate of volcanic activity of three major volcanic provinces.

“We studied massive eruptions, each covering an area the size of Western Australia, in Africa, Australia and the continents now surrounding the Atlantic Ocean.

“Our results demonstrate that volcanism in the Australian and Circum-Atlantic provinces occurred very quickly, over a period of one or two million years, at the same time as a major mass extinction. This implies that volcanic gases had strongly affected the climate and life at that time.”

“This work suggests that most species can withstand climatic changes produced by volcanic eruptions provided they have time to adapt,” Jourdan said, according to a Curtin release.

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