The asteroid that fell into the ocean off Mexico 66 million years ago and killed the dinosaurs also triggered volcanic eruptions all over the world including the triggering of the Deccan Traps in India, suggests a US team of geophysicists.
The asteroid explained the “uncomfortably close” coincidence between the Deccan Traps eruptions and the impact. The Deccan eruptions are among the largest mapped lava flows on the Earth occurring 66 million years ago.
“If you try to explain why the largest impact we know of in the last billion years happened within 100,000 years of these massive lava flows at the Deccan Traps, the chances of that occurring at random are minuscule,” said team leader Mark Richards from University of California, Berkeley.
The disappearance of the landscape-dominating dinosaurs is widely credited with ushering in the age of mammals, eventually including humans.
Richards calculates that the asteroid that created the Chicxulub crater might have generated the equivalent of a magnitude 9 or larger earthquake everywhere on Earth, sufficient to ignite the Deccan flood basalts and perhaps eruptions many places around the globe, including at mid-ocean ridges.
Richards and his team along with Deccan volcanology experts Steven Self and Loÿc Vanderkluysen, visited India in April 2014 to obtain lava samples for dating, and noticed that there are pronounced weathering surfaces, or terraces, marking the onset of the huge Wai subgroup flows.
Geological evidence suggests that these terraces may signal a period of quiescence in Deccan volcanism prior to the Chicxulub impact. Apparently never before noticed, these terraces are part of the western Ghats, a mountain chain named after the Sanskrit word for steps.
“This was an existing massive volcanic system that had been there probably several million years, and the impact gave this thing a shake and it mobilized a huge amount of magma over a short amount of time,” Richards said.
“The beauty of this theory is that it is very testable, because it predicts that you should have the impact and the beginning of the extinction, and within 100,000 years or so you should have these massive eruptions coming out, which is about how long it might take for the magma to reach the surface,” he added.
While the Deccan lava flows probably spewed immense amounts of carbon dioxide and other noxious gases into the atmosphere, it is not clear if this contributed to the demise of most of life on the Earth at the end of the age of dinosaurs.
“This connection between the impact and the Deccan lava flows is a great story and might even be true, but it doesn’t yet take us closer to understanding what actually killed the dinosaurs and the ‘forams’,” Richards added.
The forams were tiny sea creatures, many of which disappeared from the fossil record virtually overnight at the boundary between the Cretaceous and Tertiary periods, called the KT boundary.
The Deccan lava from before the impact is chemically different from that after the impact, indicating a faster rise to the surface after the impact. Richards and his team visited India in April 2014 to obtain lava samples for dating.
“This was an existing massive volcanic system that had been there probably several million years, and the impact gave this thing a shake and it mobilized a huge amount of magma over a short amount of time,” Richards noted.
A group from Princeton University has recently published new radio-isotopic dates for the Deccan Traps lava that are consistent with these predictions.
The study is due to be published in The Geological Society of America Bulletin.