Tuesday, January 20, 2015

Did the mega volacano kill the dinosaurs ?

The Cretaceous-Paleogene/Tertiary extinction event (K-Pg or K-T as it is known by geologists) was previously thought to be the only mass extinction out of the “big five” not attributable to volcanism. Instead, the currently accepted theory linked a meteorite impact near present-day Chicxulub, Mexico as the lone cause (known as the Alvarez hypothesis), although there is growing support for volcanic activity as a second major factor. Now, new research led by Brian Schoene of Princeton University has added further evidence that non-avian dinosaurs were actually wiped out by volcanism rather than a meteorite collision some 66 million years ago, confirming what some geoscientists, such as Dewey McLean, long suspected.

The Deccan Traps, a massive flood basalt in India, has long been known as a series of volcanic events that occurred at around the time of extinction, but the majority believed that they erupted too early on to have had a significant effect. Scientists have now tightened the timeline of the main sequence of eruptions, which now appear to have happened very soon before - geologically speaking - the extinction, with new precision rock dating evidence (using U-Pb dating in zircons) showing that the main phase of eruptions occurred within 250,000 years of extinction, rather than millions.

This new timeline is very important, as the volcanic gases now believed to be responsible for dramatic, extinction-inducing climate change (particularly sulfur dioxide) would have been released very shortly before, and during (up to 750,000 years) the time of the K-Pg extinction. It adds weight to the idea that volcanism was the primary cause of extinction, with the meteor impact as the icing on the cake. During it's active phase, the Deccan Traps volcano released over 1.1 million km3 (264,000 cu mi) of lava, with layer upon layer of basalt culminating in a depth of 2,000 m (6,562 ft) thick. Since then, it has gradually been eroded down to 512,000 km3 (123,000 cu mi).

Scientists are now working on further constraining the timing of eruptions and using this data to refine computer-based environmental change models. This will enable researchers to better determine the individual as well as cumulative effects of Deccan Traps volcanism and Chicxulub meteorite impact on Earth.

Past articles:
Deccan Traps: http://on.fb.me/1ByYtnX &http://on.fb.me/1ByYtnX
Did a comet cause extinction?:http://on.fb.me/14FWelu
K-Pg event: http://on.fb.me/1xuvbk5 &http://on.fb.me/1uaQff9
end-Permian extinction event - http://tmblr.co/Zyv2Js18raAV1
Image credit: by Nichalp, 2007 (http://bit.ly/1B8kHyg) Used under CC licensing.

Further reading:
Deccan Traps - http://bit.ly/1BcXWcx &http://bit.ly/1sHvLzn
Did the Traps wipe out the dinosaurs?http://bit.ly/1G4hEKz & http://bit.ly/17QFBWo
Original paper by Schone et. al. - http://bit.ly/1C66iS8(paywalled)

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