Deccan Traps and Dinosaur Extinction
Monday, 27. March 2006, 15:02:25
In December 2005 I reported on the Mass Extinctions at the end of Permian (about 250 million years ago) and how some scientists believe that it was caused by an extraterrestrial event (impact) while others think it was caused by volcanic eruptions.
I said then that I would probably come back to the Mass extinction at the end of the Cretaceous later, which might as well be now.
The discussion is more or less the same. Around 65 million years ago a large extraterrestrial body hit the Yucatan peninsula, and the Dinosaurs died out together with a gigantic mass of other organisms. For some people a clear-cut case, and any way the version most people would give you. Those in favour of a volcanic scenario will mention the Deccan Traps (see map). The Deccan Traps extend by the way far into the Indian Ocean). They are about 65 million years old. What is left after millions of years of erosion still cover about 520,000 km2 and at places the basalt cover is more than 2 km thick. The eruptions that created the Deccan Traps would have released huge quantities of particulates and heat-trapping greenhouse gases—carbon dioxide, sulphur dioxide, and water vapour—that could have caused catastrophic global climate changes. There is no doubt that the mass extinction was caused by climate and environmental changes. Changes in the composition of the atmosphere, changes of the composition of seawater, loss of habitats. I may add that there was an enormous sea level rise in the cretaceous, caused by plate tectonic changes, it is thought. Are they also the sort of changes we risk in a society where well-fead people shoot birds just for the fun of it with no eye for biodiversity? Or where governments do far too little to decrease our emissions of greenhouse gasses and waste of energy and other non-renewable resources? Research in these matters is important for our future – if any.
And now to the news bit.
About 50,000 years ago, a huge meteorite (The Lonar Crater) made a deep hole in the Deccan Traps. This created an excellent site to study the basalts in more detail, and that is what Adam Soule has been doing in January 2006. He looked for clues to learn how the Deccan Traps formed. The key scientific debate, Soule said, is whether the Deccan Trap lava flows erupted too fast for the Earth to absorb the excess gases, or whether they erupted much more slowly as lava does today on a much smaller scale in Hawaii, for example.
He returned to Woods Hole with about 100 pounds of rock samples, which he’ll slice and examine under a microscope. By looking at variations in their textures, Soule hopes to determine if they erupted gradually, or more quickly to hasten the dinosaurs’ extinction.
Oceanus at http://www.whoi.edu/oceanus/viewArticle.do?id=10606§ionid=1021
Some geologists think that Large Igneous Provinces (LIPs) like the Deccan Traps and the late Permian LIP in Siberia were created by so called super plumes (coming from the deepest part of the mantle), but this is another controversial issue that I may come back to later.
I said then that I would probably come back to the Mass extinction at the end of the Cretaceous later, which might as well be now.
The discussion is more or less the same. Around 65 million years ago a large extraterrestrial body hit the Yucatan peninsula, and the Dinosaurs died out together with a gigantic mass of other organisms. For some people a clear-cut case, and any way the version most people would give you. Those in favour of a volcanic scenario will mention the Deccan Traps (see map). The Deccan Traps extend by the way far into the Indian Ocean). They are about 65 million years old. What is left after millions of years of erosion still cover about 520,000 km2 and at places the basalt cover is more than 2 km thick. The eruptions that created the Deccan Traps would have released huge quantities of particulates and heat-trapping greenhouse gases—carbon dioxide, sulphur dioxide, and water vapour—that could have caused catastrophic global climate changes. There is no doubt that the mass extinction was caused by climate and environmental changes. Changes in the composition of the atmosphere, changes of the composition of seawater, loss of habitats. I may add that there was an enormous sea level rise in the cretaceous, caused by plate tectonic changes, it is thought. Are they also the sort of changes we risk in a society where well-fead people shoot birds just for the fun of it with no eye for biodiversity? Or where governments do far too little to decrease our emissions of greenhouse gasses and waste of energy and other non-renewable resources? Research in these matters is important for our future – if any.And now to the news bit.
About 50,000 years ago, a huge meteorite (The Lonar Crater) made a deep hole in the Deccan Traps. This created an excellent site to study the basalts in more detail, and that is what Adam Soule has been doing in January 2006. He looked for clues to learn how the Deccan Traps formed. The key scientific debate, Soule said, is whether the Deccan Trap lava flows erupted too fast for the Earth to absorb the excess gases, or whether they erupted much more slowly as lava does today on a much smaller scale in Hawaii, for example.
He returned to Woods Hole with about 100 pounds of rock samples, which he’ll slice and examine under a microscope. By looking at variations in their textures, Soule hopes to determine if they erupted gradually, or more quickly to hasten the dinosaurs’ extinction.
Oceanus at http://www.whoi.edu/oceanus/viewArticle.do?id=10606§ionid=1021
Some geologists think that Large Igneous Provinces (LIPs) like the Deccan Traps and the late Permian LIP in Siberia were created by so called super plumes (coming from the deepest part of the mantle), but this is another controversial issue that I may come back to later.
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