Serial Killer Wanted
Tuesday, 25. March 2008, 15:29:18
As I mentioned yesterday Earth volcanic activity is one of the two leading scenarios proposed to explain the mass extinctions in the last 600 million years, while the other involves asteroid impacts. The most “popular” mass extinction took place at the end of the Cretaceous, when the Dinosaurs died out.
Are Volcanic Gases Serial Killers? Extremely large volumes of flood basalt erupted 67 to 65 million years ago, forming the Deccan Traps in India. The impact of these flood basalt eruptions on the global atmosphere and the coeval end-of-Cretaceous mass extinction is still not quite certain. The eruptions would have had a widespread environmental impact through the release of primarily sulphur and chlorine and possibly fluorine.
An analysis by Stephen Self of the Open University in Milton Keynes, England, and colleagues lends new support to the volcanism scenario. By looking at tiny bits of glass (glass inclusions) that formed inside the lava flows, they’ve been able to reconstruct how much sulphur and chlorine were released. The findings are reported in the journal Science of 21 march 2008 under the title "Sulphur and Chlorine in Late Cretaceous Deccan Magmas and Eruptive Gas Release”. The findings demonstrates unambiguously that the capacity of Deccan basalts to discharge sulphur into the atmosphere was similar to that of present-day erupting basalts. Although this may sound trivial, it means that comparisons with historic eruptions like Laki in 1783-1784 make sense.
Other volatiles (gasses) may also have altered the climate, however, in particular halogens (fluorine, chlorine, bromine, iodine). In addition to having regional devastating effects, halogens may dramatically affect both tropospheric and stratospheric chemistries, with severe impacts on the ozone layer.
It is however still too early to prove a causal link between mass extinction and volcanism either right or wrong, so the Chicxulub impact crater is still in the running.
• http://www.sciencemag.org/cgi/content/abstract/319/5870/1654
• http://www.nytimes.com/2008/03/25/science/25obexti.html
Are Volcanic Gases Serial Killers? Extremely large volumes of flood basalt erupted 67 to 65 million years ago, forming the Deccan Traps in India. The impact of these flood basalt eruptions on the global atmosphere and the coeval end-of-Cretaceous mass extinction is still not quite certain. The eruptions would have had a widespread environmental impact through the release of primarily sulphur and chlorine and possibly fluorine.An analysis by Stephen Self of the Open University in Milton Keynes, England, and colleagues lends new support to the volcanism scenario. By looking at tiny bits of glass (glass inclusions) that formed inside the lava flows, they’ve been able to reconstruct how much sulphur and chlorine were released. The findings are reported in the journal Science of 21 march 2008 under the title "Sulphur and Chlorine in Late Cretaceous Deccan Magmas and Eruptive Gas Release”. The findings demonstrates unambiguously that the capacity of Deccan basalts to discharge sulphur into the atmosphere was similar to that of present-day erupting basalts. Although this may sound trivial, it means that comparisons with historic eruptions like Laki in 1783-1784 make sense.
Other volatiles (gasses) may also have altered the climate, however, in particular halogens (fluorine, chlorine, bromine, iodine). In addition to having regional devastating effects, halogens may dramatically affect both tropospheric and stratospheric chemistries, with severe impacts on the ozone layer.
It is however still too early to prove a causal link between mass extinction and volcanism either right or wrong, so the Chicxulub impact crater is still in the running.
• http://www.sciencemag.org/cgi/content/abstract/319/5870/1654
• http://www.nytimes.com/2008/03/25/science/25obexti.html
