“This cooling caused major changes in the climate that made things difficult for dinosaurs, but the meteorite was the best thing that happened,” said study co-author Don Baker, a geochemist at McGill University. “This was the last extinction event, but their condition was not good until the time of the meteorite impact.”
According to some studies, Earth’s temperature was dropping long before the meteorite impact. But scientists hadn’t pinpointed a cause, so Baker and his team focused on a volcanic explanation.
While meteorites are the common explanation for the demise of dinosaurs (apart from birds), volcanic eruptions are also a controversial explanation. The evidence lies in one of the world’s largest volcanic regions known as the Deccan Traps. This region, located in what is now central and central India, was the site of a massive eruption of lava around the time the dinosaurs went extinct.
If you visit the site today, you can see layers of lava from past eruptions. In some areas, the layer is more than a mile thick and covers an area of about 200,000 square miles (an area the size of Oregon and Washington combined).
An eruption of that magnitude would have dramatically changed the environment, releasing gases like sulfur dioxide, reflecting sunlight back into space, and causing massive surface cooling.
“Our dating shows that the eruptions continued one after the other for hundreds of thousands of years,” co-author Paul Rennes, a geochronologist at the University of California, Berkeley, said in an email. “This level of volcanic activity over hundreds of thousands of square miles is rare in geological history.”
To study the gases released during these ancient lava flows, the team hammered out rocks within the Deccan Traps. Most of the elements are lost to the atmosphere during the eruption, but a small portion becomes trapped in minerals as the lava cools at the end of the eruption.
The research team has developed a new technique to measure the amount of sulfur and fluorine in minerals. They also recreated the conditions in the lab to determine how much sulfur or fluorine would be needed in the environment to get that amount into the crystal..
Just before the meteorite that killed the dinosaurs hit Earth, researchers found that lava flows contained significant concentrations of fluorine, which may have had local effects such as acid rain, plant damage, and animal poisoning. I discovered that there is a sex. However, the sulfur concentration in the lava flows was so high that it was enough to cause a significant temperature drop around the world.
The volcanic eruption would have been unprecedented in human history. A related but highly inappropriate comparison is the powerful eruption from Mount Pinatubo in 1991. The eruption spewed out 10 cubic kilometers of magma and caused global temperatures to drop by about 0.5 degrees in one year.
By comparison, some of these ancient eruptions produced up to 100 cubic kilometers of ejecta, Baker said. The drop in temperatures will be even more dramatic and persistent, making it like an eternal winter (inspired by Game of Thrones music). He points to several studies that suggest temperatures may have fallen an additional 10 degrees Celsius over the decade.
“When you have a big eruption like this, the temperature drops every 10 years and it stays cold,” Baker said. “Once you change temperature, it’s a global change that goes far beyond temperature…it includes changes in wind patterns, rain patterns, and everything else.”
If so, dinosaurs probably didn’t have time to adapt. The first drop in temperatures will probably occur within a decade, with each year becoming a little colder than the previous, Baker said.
It’s difficult to know definitively what was happening to dinosaurs during that period, but scientists are always trying to solve the mystery. Ultimately, Baker said, there is probably no simple explanation, and perhaps no single explanation, for why the dinosaurs went extinct. But let’s use dinosaurs as an example of what happens when the Earth changes too quickly. This is today’s climate change warning.
“Rapid climate change, no matter how it occurs, could be extremely dangerous to species on Earth,” Baker said. “Rapid changes that exceed evolutionary or immigrant adaptation would be problematic.”