The cataclysmic asteroid that wiped out the dinosaurs might have also triggered massive volcanic eruptions deep beneath the ocean, new research says. It’s yet another way the extraterrestrial impact could have killed off more than 70 percent of life on Earth — that is, if the timing isn’t just a coincidence.
Roughly 66 millions years ago, a 6-mile-wide asteroid crashed into Mexico’s Yucatán Peninsula — causing a massive, worldwide earthquake. That Earth-shaking impact might have made underwater volcanoes spit up magma even more ferociously than usual, according to a study published today in the journal Science Advances. These events might have added to the asteroid’s apocalyptic aftershocks — which include wildfires, global cooling, and acid rain — that caused the mass extinction of roughly three quarters of Earth’s species, including dinos.
The findings back up earlier reports of more intense volcanic eruptions in India also roughly 66 million years ago. But other scientists are skeptical about the link between the asteroid and the underwater volcanic eruptions, because the paper doesn’t propose exactly how they happened. “Why would that much earthquake energy cause eruptions like that?” says Sean Gulick, a geophysicist at the University of Texas at Austin who did not participate in the study. “It’s an interesting idea, but where’s the model that backs up the physics that would allow that to happen?”
For decades, scientists have been arguing about whether volcanoes or an asteroid caused the massive climate shifts that spelled doom for the dinosaurs. The evidence supporting the asteroid hypothesis kept mounting. But then, a few years ago, scientists at UC Berkeley asked, why pick one flavor of apocalypse? Both might have been on the menu 66 million years ago: the asteroid, for instance, might have intensified eruptions from a particularly volcanic region in India called the Deccan Traps. So Earth scientists Joseph Byrnes at the University of Minnesota and Leif Karlstrom at the University of Oregon went looking for more signs of ancient eruptions, in easy-to-spot stretches of the seafloor.
Gaps in the Earth’s crust called mid-ocean ridges weep magma to create the ocean floor, churning out material at a pretty even pace of up to several inches each year. That allowed Karlstrom and Byrnes to pinpoint the sections produced roughly 66 million years ago. But searching for signs of volcanic eruptions isn’t as easy as looking for bumpy tracts of hardened lava on the bottom of the ocean. “It’s hard to get to the sea floor because the ocean is sitting on it,” Byrnes says. Instead, the team turned to satellite maps of the peaks and valleys in the ocean’s surface. These bumpy spots produced by, say, an underwater volcano belching out magma have more mass, and therefore a bigger gravitational pull, than valleys or flat regions. So underwater peaks pull more ocean around them, creating wrinkles in the surface that can be seen from space.
Karlstrom and Byrnes found two bumps in stretches of the Earth’s crust in the Pacific and Indian Oceans that were produced within a million years of that 66 million-year-old impact. These bumps were made up of between 23,000 and 240,000 cubic miles (100,000 to 1 million cubic kilometers) of magma, Byrnes says — which means that the mid-ocean ridges had suddenly started erupting more intensely than at any other point in 100 million years. “No normal process makes those bumps, otherwise we’d see it more than once,” he says. ”If it’s just a random burp of magma, it happened at a very coincidental time.”
Byrnes and Karlstrom suspect that when the infamous asteroid crashed into the Yucatán, it hit the Earth like the clapper on a bell. The impact sent powerful vibrations ringing through the Earth at roughly the intensity of a magnitude 10 or 11 quake. This massive jolt might have made these mid-ocean ridges squirt out more magma, the authors say — although the exact mechanisms remain a mystery.
“It validates our prediction that other magma systems were affected, too — which is kind of cool!” says Paul Renne, a planetary scientist at UC Berkeley who co-authored a paper about those intense eruptions in India 66 million years ago. His team proposed that the seismic shakeup from the asteroid’s impact could have made magma fizz out of volcanoes “kind of like when you shake a can of coke,” he says.
But Gulick isn’t as convinced. For one thing, the dates are a little fuzzy — the increased volcanic activity the study reports happened within a million years of when the asteroid touched down in the Yucatán: that could have been before the impact, or long after. “So how do we really know that something within those million years is directly related to an event that happened on a specific day?” Gulick says. “The resolution isn’t good enough to say that.” He also wishes the study had been clearer about exactly how the asteroid’s impact increased volcanic eruptions at these mid-ocean ridges. “It’s an interesting observation, but I’m a little skeptical.”
Byrnes says that’s a fair critique. But, he adds, they only see the evidence of increased eruptions at one point in time. “And it just so happens it lines up with the impact’s age,” he says. In the future, he and Karlstrom intend to investigate how these eruptions may have caused changes in ocean chemistry. But for now, they’re excited by the responses to the research they’ve been getting from the rest of the scientific community. “You get really good at failing and bouncing back from that,” Karlstrom says. “But every now and then when something does work, it’s nice to see that people are also excited about it.”