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Remember that cartoon where Noah’s Ark is floating off and a T Rex couple is watching it? “Oh crap,” one of them says. “Was that today?” And while there’s no way that bit of humor explains how dinosaurs met their end, some ancient artifacts unearthed in recent studies may add to the theories. What went on 65 million years ago? Two studies took different approaches to determine when ancient volcanoes erupted. Both studies cleared up a few aspects but also added new layers to the dinosaur extinction mystery.
What we know about dinosaur extinction
Scientists generally agree that dinosaur extinction happened about 66 million years ago, during the Cretaceous-Paleogene (K-Pg). Centuries of examining ancient artifacts and other scientific paths of study have supported the conclusion that about three-quarters of all living species on earth were wiped out then. One exception was birds, and even that was probably only the ground dwellers since the asteroid obliterated so many trees. They thrived and descended into the hummingbirds, ostriches, and chickadees some 18,000 other species we know today. But the extinction of the other dinosaurs has led to much head-scratching and immense study from modern science, and the mystery is still with us.
With evidence discovered by gauging the high levels of iridium in the layer of rock, most geologists agree a 6-mile-wide asteroid hit the earth at Chicxulub, Mexico. It’s widely accepted that this asteroid caused many natural disasters that could have doomed the dinosaurs, from destroying trees over a 930-mile radius to starting wildfires over much of the earth’s surface. If that wasn’t enough (and it probably was), the asteroid was also thought to have caused so much soot and ash it obliterated sunlight that even ancient plants required to live and provide food for dinosaurs. But that wasn’t the whole explanation, as two new studies have at least partly proven.
What new studies of ancient lava have added
Those generally accepted extinction dates don’t correspond only to an asteroid, however. It’s possible that near the same time the dinosaurs died out, a burst of volcanic activity formed massive rocks. These “Deccan Traps” in western India are just the sort linked to other mass extinctions. The way it works: The hot lava warms the climate with an overload of greenhouse gases. At the same time, volcanic eruptions can put mass quantities of aerosols high into the atmosphere. And just like the 70s, when modern aerosol sprays were blamed for atmospheric damage, this Deccan Trap lava could have produced enough aerosols to effectively block the sun and cool the earth, driving certain species to extinction.
Two teams of scientist have recently attempted to narrow the timing of the Deccan Traps’ formation. Each team was trying to determine if the lava also played a part in dinosaur extinction. Ancient artifacts and temperature records show that climate change and accompanying indicators of stress on the ecosystem both started about the same time as the lava bursts.
Both groups’ findings supported the idea that the Deccan eruptions happened over the course of about one million years, starting around 400,000 years before the dinosaurs met their doom 66 million years ago. But after that essential agreement, their research methods led them to different conclusions.
Two teams take on lava dating
The first team, led by Courtney Sprain of the University of California, Berkeley, employed argon-argon dating of Deccan Trap volcanic ash. Sprain and her colleagues concluded that three-quarters of the lava volume at Deccan erupted after the mass extinction and that the eruption rate ramped up after the Chicxulub impact.
The team still linked the lava flow of the Deccan Traps to the dinosaur’s eventual demise, however. Sprain theorized that the traps weakened the ecosystem overall late in the Cretaceous period leading up to the asteroid’s impact, which might have made the entire planet more susceptible to the soot blackout and raging wildfires. She also points to the earliest eruptions as a possible source of the gases that changed the climate, though most of the lava the team studied didn’t issue forth until well after the Chicxulub asteroid.
A second group of sleuths with lead author Blair Schoene of Princeton University tried to align (or disprove) the link between the Deccan Trap lava and dinosaur extinction using uranium-lead dating of the ash bed zircons formed in the lava. It reached the conclusion that four large magmatic pulses had happened, with the second lava burst being the most rapid. The team didn’t link these bursts to the timeline of the asteroid’s impact, though. Instead, the Princeton team’s findings supported that lava burst began tens of thousands of years ahead of the asteroid slam. Schoene thought the biggest value-add to potentially solving the mystery was having a timeline for the lava bursts that could be used to compare to climate change findings. He thought reasonable next questions would revolve around the gases present on the timeline leading up to the extinction event, particularly C02 and sulfur releases.
How long till the mystery’s solved?
The researchers on both studies seem heartened that the findings have brought us closer to solving the mystery of dinosaur extinction. Part of the emphasis in studying the mystery extends to what past mass extinctions can teach the world’s current population about what could happen to us as a result of climate change. While it may not happen before yet another Jurassic Park movie helps us understand why we don’t necessarily want the non-bird dinosaurs back in our midst, the clearer picture of dinosaur extinction is definitely on the way.