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Siberian lava flow led to early extinction
WASHINGTON. July 12: A lava eruption that covered more than 100.000 square miles of Siberia could have caused climate changes that contributed to the near-total extinction of animal life on earth some 250 million years ago. researchers say. reports AP.
In a study to be published Friday. Apish R Basu of the University of Rochester and Paul R Renne of the Institute of Human Origins in Berkeley. California, said that laboratory dating of rock samples from the Siberian lava flow show the eruption was about the same time that fossil deposits record the extinction of up to 95 per cent of all animal species.
"We proved that the timing of the eruption was coincident with the extinction.' said Basu in an interview.
'Our work suggests a strong lipk between the two. but we can't step nut and say the eruption caused the extinction."
Steven Stanley, a John Hopkins University paleobiologist. said the study adds strength to the idea that a volcanic eruption could have caused or contributed to the early extinction, but the exact mechanism of death for millions of animals over thousands of years is still unclear.
"1 think their bringing to light this approximate coincident is every important." said Stanley. “They pointed out that people need to look at this volcanic event as a candidate for causation."
Experts, such as Stanley, have shown that there have been a long series of major and minor extinctions in the earth's history. The most famous is
the event 65 million years ago that killed off the dinosaurs. but the extinction 250 million years ago was even more widespread.
"It probably was the most severe global extinction on record of the past 600 million years." said Stanley. Marine animals were the most severely affected, but the event also killed off most of the mammal-like reptile species that then walked thf earth, he said.
Between 75 per cent and 95 per cent of all animal species died in the extinction. he said.
Basu and Renne determined when the Siberian eruption occurred by age-dating a number of rock samples taken from the site by Soviet scientists. The rocks all came from a major formation called the Siberian Lava Traps.
The specimens, said Basu, were in pristine condition with almost no alteration or weathering since they . were laid down as molten lava
To date the rocks. Basu and Renne used a technique called argon-argon aging. The technique is based on the fact that potassium decays at a known rate into argon. By measuring the ratio, the age of the rocks can be established.
Basu said the rocks consistently measured at ages of between 248.3 and 247.5 million years old which is within the margin of error for the estimated time of the major extinction.
Lava from the massive flow covered about 130.000 square miles (338.000 square kilometres) in successive waves that were up to a half mile (0.8 kilometres) thick, said Basu. The eruption continued in spurts over a period of
perhaps 200.000 years and produced about 1.5 million cubic kilometres of lava rock.
'If that volume of lava rock were to be spread uniformly on the surface of the earth, it would have created a 10-foot (3-metre) thick layer all over the globe." said Basu.
Eruptions of this size would have sent millions of tons of ash, dust and gas into the atmosphere, almost certainly affecting the weather, said Basu.
Stanley said chemical droplets from volcanic eruptions can stay aloft for long periods of time and if there are many such events close together "you probably are going to lower temperatures throughout the world."
Though it still is not certain What causal the extinction 250 million years ago. Stanley said that climate changes caused by volcanic eruptions is considered a likely candidate. Other causes could include a drop in sea level and the break up of the earth's land mass into separate continents, an event that could also affect the weather.
No evidence has been found, said Stanley, to suggest that an asteroid smashing into earth from outer space could have played a role. A climate-Altering collision with an extraterrestrial boulder, however, is considered by many scientists to have been the most llke|y cause of the dinosaur extinction 65 million years agp.
The study by Basu and Renne was to be published Friday in Science, the journal of the American Association for the Advancement of Science.