Re: [meteorite-list] Volcanic Gases, Not Meteors, May Have Caused Mass Extinctions
meteorite-list@meteoritecentral.com Sent: Monday, March 13, 2006 5:02 PM Subject: [meteorite-list] Volcanic Gases, Not Meteors,May Have Caused Mass Extinctions http://www.ens-newswire.com/ens/mar2006/2006-03-13-05.asp Volcanic Gases, Not Meteors, May Have Caused Mass Extinctions Environment News Service March 13, 2006 LEICESTER, UK, March 13, 2006 (ENS) - Earth's history has been punctuated by mass extinctions that have rapidly wiped out nearly all life forms on the planet. To determine what caused these events, British geologists are challenging the currently held theory that meteorite impacts are to blame for wiping out the dinosaurs 65 million years ago and other mass extinctions. Professor Andy Saunders and Dr. Marc Reichow are testing the theory that gases released by volcanic activity led to a prolonged volcanic winter brought on by sulphur-rich aerosols, followed by a period of warming induced by carbon dioxide in the atmosphere. Flood basalt eruptions correspond with all main mass extinctions, says Saunders, within error of the techniques used to determine the age of the volcanism. Flood basalt eruptions are vast outpourings of lava that covered large areas of the Earth's surface, creating what geologists call flood basalt provinces. Saunder says, these flood basalt events may have released enough greenhouse gases - sulfur dioxide (SO2) and carbon dioxide (CO2) - to dramatically change the climate. The largest flood basalt provinces on Earth, known as traps, coincide with the largest extinctions. The Siberian Traps correspond with the end of the Permian era some 251 million years ago when around 95 percent of all living species died out. The Deccan Traps in India correspond with the end of the Cretaceous era, some 65 million years ago when the dinosaurs disappeared, leaving only fossils. Saunders and Reichow at Leicester, in collaboration with Anthony Cohen, Steve Self, and Mike Widdowson at the Open University, have recently been awarded a Natural Environment Research Council grant to study the Siberian Traps and their environmental impact. The Siberian Traps are the largest known continental flood basalt province. Erupted about 250 million years ago at high latitude in the northern hemisphere. A scientific debate is underway concerning the origin of these provinces and their environmental impact that this research team hopes to clarify. Using radiometric dating techniques, they hope to constrain the age and, combined with geochemical analysis, the extent, of the Siberian Traps. Measuring how much gas was released during these eruptions 250 million years ago is a considerable challenge, Saunders says. The researchers will study microscopic inclusions trapped in minerals of the Siberian Traps rocks to estimate the original gas contents. Using these data they hope to be able to assess the amount of SO2 and CO2 released into the atmosphere 250 million years ago, and whether or not this caused climatic havoc, wiping out nearly all life on Earth. By studying the composition of sedimentary rocks laid down at the time of the mass extinction, they also hope to detect changes to seawater chemistry that resulted from major changes in climate. From these data Professor Saunders and his team hope to link the volcanism to the extinction event. If we can show, for example, that the full extent of the Siberian Traps was erupted at the same time, we can be confident that their environmental effects were powerful, said Saunders. Understanding the actual kill mechanism is the next stage. The idea that meteorite impacts caused mass extinctions has been in fashion over the last 25 years, since Louis Alverez's research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65 million year old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping out the dinosaurs and many other species, according to Alverez. Professor Saunders observed, Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid's dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on Earth? There is scant evidence of impacts at the time of other major extinctions such as at the end of the Permian, 251 million years ago, and at the end of the Triassic, 200 million years ago. Saunders says the evidence that has been found does not seem large enough to have triggered an extinction at these times. Dr. Michael Benton, a professor of paleontology at Bristol University, is also studying the extinctions of 251 million years ago. Over the past decade or so, new discoveries in the field and important progress in dating techniques have given us a more precise picture of this period, he wrote in April 2005. The suddenness and the scale of the event first suggested a collision
[meteorite-list] Volcanic Gases, Not Meteors, May Have Caused Mass Extinctions
http://www.ens-newswire.com/ens/mar2006/2006-03-13-05.asp Volcanic Gases, Not Meteors, May Have Caused Mass Extinctions Environment News Service March 13, 2006 LEICESTER, UK, March 13, 2006 (ENS) - Earth's history has been punctuated by mass extinctions that have rapidly wiped out nearly all life forms on the planet. To determine what caused these events, British geologists are challenging the currently held theory that meteorite impacts are to blame for wiping out the dinosaurs 65 million years ago and other mass extinctions. Professor Andy Saunders and Dr. Marc Reichow are testing the theory that gases released by volcanic activity led to a prolonged volcanic winter brought on by sulphur-rich aerosols, followed by a period of warming induced by carbon dioxide in the atmosphere. Flood basalt eruptions correspond with all main mass extinctions, says Saunders, within error of the techniques used to determine the age of the volcanism. Flood basalt eruptions are vast outpourings of lava that covered large areas of the Earth's surface, creating what geologists call flood basalt provinces. Saunder says, these flood basalt events may have released enough greenhouse gases - sulfur dioxide (SO2) and carbon dioxide (CO2) - to dramatically change the climate. The largest flood basalt provinces on Earth, known as traps, coincide with the largest extinctions. The Siberian Traps correspond with the end of the Permian era some 251 million years ago when around 95 percent of all living species died out. The Deccan Traps in India correspond with the end of the Cretaceous era, some 65 million years ago when the dinosaurs disappeared, leaving only fossils. Saunders and Reichow at Leicester, in collaboration with Anthony Cohen, Steve Self, and Mike Widdowson at the Open University, have recently been awarded a Natural Environment Research Council grant to study the Siberian Traps and their environmental impact. The Siberian Traps are the largest known continental flood basalt province. Erupted about 250 million years ago at high latitude in the northern hemisphere. A scientific debate is underway concerning the origin of these provinces and their environmental impact that this research team hopes to clarify. Using radiometric dating techniques, they hope to constrain the age and, combined with geochemical analysis, the extent, of the Siberian Traps. Measuring how much gas was released during these eruptions 250 million years ago is a considerable challenge, Saunders says. The researchers will study microscopic inclusions trapped in minerals of the Siberian Traps rocks to estimate the original gas contents. Using these data they hope to be able to assess the amount of SO2 and CO2 released into the atmosphere 250 million years ago, and whether or not this caused climatic havoc, wiping out nearly all life on Earth. By studying the composition of sedimentary rocks laid down at the time of the mass extinction, they also hope to detect changes to seawater chemistry that resulted from major changes in climate. From these data Professor Saunders and his team hope to link the volcanism to the extinction event. If we can show, for example, that the full extent of the Siberian Traps was erupted at the same time, we can be confident that their environmental effects were powerful, said Saunders. Understanding the actual kill mechanism is the next stage. The idea that meteorite impacts caused mass extinctions has been in fashion over the last 25 years, since Louis Alverez's research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65 million year old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping out the dinosaurs and many other species, according to Alverez. Professor Saunders observed, Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid's dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on Earth? There is scant evidence of impacts at the time of other major extinctions such as at the end of the Permian, 251 million years ago, and at the end of the Triassic, 200 million years ago. Saunders says the evidence that has been found does not seem large enough to have triggered an extinction at these times. Dr. Michael Benton, a professor of paleontology at Bristol University, is also studying the extinctions of 251 million years ago. Over the past decade or so, new discoveries in the field and important progress in dating techniques have given us a more precise picture of this period, he wrote in April 2005. The suddenness and the scale of the event first suggested a collision with an asteroid or other meteor. Recent paleontological data suggest a different cause, Benton wrote in RTD Info, a magazine on European research. Volcanic eruptions