A record of volcanism preserved along ancient mid-ocean ridges provides evidence for heightened worldwide magmatic activity 66 million years ago just after the Chicxulub meteor struck Earth, according to University of Oregon scientists.
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| Coloured and black points mark the global distribution of mid-ocean ridges, with ages of 66 million years ago created at spreading rates above and below 35 millimeters a year, respectively. Colours indicate the maximum gravity anomaly within 2 degrees [Credit: Joseph Byrnes] |
Lead author Joseph Byrnes, a former UO doctoral student, says that this global volcanic activity was likely triggered by strong seismic waves radiated from the meteorite impact site. Subsequently accelerated volcanism, he said, likely would have been active during the mass extinction of the world's non-avian dinosaurs.
Volcanism, particularly a massive outpouring of basalt recorded by the Deccan Traps in India, has been in and out of the extinction debate. Rare volcanic events at such a scale are known to cause catastrophic disturbances to Earth's climate and, when they occur, they are often linked to mass extinctions.
Since evidence of the meteor strike near present day Mexico surfaced in the 1980s, scientists have debated whether the impact or the Deccan Traps volcanic eruptions was the primary driver for extinction of the dinosaurs.
Progressively more accurate dating methods indicate that while the Deccan Traps eruptions were active during the mass extinction, they actually began significantly before the Chicxulub impact, said Leif Karlstrom, a professor in the UO's Department of Earth Sciences and co-author on the study with Byrnes.
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| The amount of seafloor exhibiting small structural anomalies is plotted as a function of the age of seafloor. Trends that persist over 10 million years have been subtracted to highlight transient features, and only high spreading rates are plotted here. The highest peak, which indicates the production of 8 percent more anomalous seafloor than on average, occurs at 66 million years ago and is coincident with the age of the Chicxulub meteorite impact [Credit: Joseph Byrnes] |
In 2015, researchers at the University of California, Berkeley, proposed that the two events might be connected. They suggested that Chixculub may have modulated distant volcanism by sending seismic waves through the Earth and accelerating volcanic activity in the Deccan Traps. Similar to the impacts that normal tectonic earthquakes sometimes have on wells and streams, Karlstrom said, the study proposed that powerful shaking liberated magma stored in the mantle beneath the Deccan Traps and caused the largest eruptions there.
The new National Science Foundation-supported study at the UO adds another layer to the story, said Karlstrom, who also co-authored on the UC-Berkeley research. It suggests that other volcanic activity around the world was triggered by the meteor. Seismic waves moving through the Earth, he said, may have accelerated volcanism already occurring along mid-ocean ridges.
"Our work suggests a connection between these exceedingly rare and catastrophic events, distributed over the entire planet," Karlstrom said. "The meteorite's impact may have influenced volcanic eruptions that were already going on, making for a one-two punch."
The findings emerged as Byrnes, now a postdoctoral researcher at the University of Minnesota, discovered the evidence for volcanic activity by analyzing publicly available global datasets, including two updated in the last decade, on free-air gravity, ocean floor topography and tectonic spreading rates.