Killer asteroids and volcanic eruptions
A study led by scientists at the University of California suggests that the impact occurred 60 million years ago off the Yucatan peninsula might have triggered the massive eruptions of lava of the Deccan, India.
The asteroid that crashed into the ocean off the coast of Mexico 66 million years ago causing the extinction of the dinosaurs, according to the assertions of a team of geophysicists from the University of California, could have caused volcanic eruptions can contribute significantly to destruction of life on Earth.
In particular, the researchers argue that the impact could have triggered most of the lava eruptions that occurred in India, which gave birth to the geological formation known as the Deccan Traps. The new theory would explain in a simple coincidence between the eruptions and the impact that has always created doubts about the hypothesis that sees the asteroid as the sole cause of mass extinction Cretaceous.
“If you try to explain why the greatest impact we know of in the last few billion years is successful in less than 100,000 years by these massive lava flows in Deccan … the probability that these two events to occur so close randomly is minimal, “said Mark Richards, professor of Earth and Planetary Sciences at the University of California. “It is not a coincidence very credible.”
Credit: Mark Richards
Richards and his colleagues bring evidence in support of their theory, that the impact would have rekindled the lava flows of the Deccan, in an article published last April 30 on The Geological Society of America Bulletin.
The Deccan lava flows began before impact and were then continued for several hundred thousand years, releasing into the atmosphere huge amounts of carbon dioxide and other harmful gases that can change the climate. It is not yet clear whether this has contributed to the disappearance of most of life on Earth to the end of the dinosaur, said Richards.
“The connection between the impact and the lava flows of the Deccan is a great idea and it might even be true, but not us closer still to fully understand what really killed the dinosaurs and foraminifera,” said Richards, referring to small sea creatures called foraminifera, many of which have disappeared from the fossil record almost in the blink of an eye, in a time interval to the boundary between the Cretaceous and Tertiary, called KT boundary. It is now widely accepted that the disappearance of the dinosaurs in the landscape has ushered in the era of terrestrial mammals, including in the last part even the appearance of man.
Richards points out that its proposal differs from the previous hypothesis, with which it was suggested that the impact energy will be concentrated around the Earth at a point directly opposite to the impact, triggering the eruption of the Deccan. The theory of “focusing antipodes” was discarded when the Chicxulub crater was found off the coast of Yucatan, Mexico, which is about 5,000 km from the antipodal point of the Deccan Traps.
Richards had already proposed in 1989 that the plumes of hot rock, called “plumes”, go up through the Earth’s mantle every 20-30 million years, generating huge flows of lava as the Deccan Traps. It had struck me that the last four mass extinctions had occurred six to coincide with one of these massive eruptions.
“The group of Paul Renne at Berkeley has demonstrated years ago that the Central Atlantic Magmatic Province is associated with the mass extinction of Triassic / Jurassic, dating back 200 million years, while the Siberian Traps is associated with the end of the Permian, which occurred 250 million years ago. Now we also know that the result of a major volcanic eruption in China called Trappi of Mount Emei is associated with the extinction of the late Guadalupiano, 260 million years ago,” said Richards. “Then there are eruptions of the Deccan, one of the largest lava flows that can be observed on Earth, which occurred 66 million years ago, coinciding with the mass extinction of the dinosaurs. So we ask: what really happened during the KT boundary?”
Credit: Mark Richards
Richards has worked with experts in many areas to try to find flaws in his theory that links the asteroid impact eruptions of the Deccan, but more trying to find flaws discovered more evidence in its favor. Renne, a professor in the Department of Earth and Planetary Sciences at Berkeley Geochronology Center and director of the University of California, got a couple of years ago a new dating of the asteroid impact and the mass extinction and them He has found essentially simultaneous, and also within a range of about one hundred thousand years from the Deccan eruptions that produced about 70 percent of the lava that now extend across the Indian subcontinent from Mumbai to Calcutta.
Michael Manga, a professor in the same department, in the last decade has shown that the great earthquakes of magnitude equal to the one that occurred in Japan in 2011, can trigger volcanic eruptions nearby. Richards has calculated that the asteroid that triggered the Chicxulub crater may have generated the equivalent of an earthquake of magnitude 9 or higher anywhere on Earth. An earthquake of this magnitude would be enough to trigger the Deccan basalts eruptions and perhaps in many other places around the world, even in mid-ocean ridges.
“It is unthinkable that the impact could have such a large amount of molten rock at great distances from the crash site, but if you consider a system that already contained magma just imagine to give him a little push to trigger a major eruption,” he said Manga.
Similarly, the lava of the Deccan before the impact is chemically different from that after the impact, and this indicates a rapid ascent to the surface, while the pattern of the banks from which lava flowed – “like cracks in a soufflé” said Renne – they are oriented in a more random, as a result of the impact.
“There is a profound change in the type of eruptions, the volume and composition of eruptions,” said Renne. “The question is that discontinuity is synchronous with the impact? ‘.”
Richards, Renne and student Courtney Sprain, together with the experts of Volcanology and Loÿc Vanderkluysen Deccan Steven Self, visited India in April 2014 resulting in lava samples for dating. The data will have noticed that there are large areas of weather, or terraces, marking the beginning of the large subgroup of flows Wai. The geological data suggest that these terraces may signal a period of quiescence in the Deccan volcanism before the impact of Chicxulub. Apparently no one before he had noticed that these terraces are part of the Western Ghats, a mountain range named after the Hindi word meaning “steps”.
“This was a huge volcanic system, existed probably several million years, and the impact gave him a kick, setting in motion a large amount of magma in a short amount of time,” said Richards. “The beauty of this theory is that it is very simple to test it, because it is expected that it should have the impact and the beginning of extinction, and within plus or minus 100,000 years, the time necessary to the magma to reach the surface, is They should have these large eruptions. ”
From the moment the article was accepted for publication, a group of Princeton University has published new data on radioisotope lavas of the Deccan Traps, consistent with these predictions. Renne and Sprain University of Califorina also preliminary and unpublished Deccan lava that could help consolidate the theory of Richards.