It’s one of the big unsolved whodunits in history: What killed off the dinosaurs? Scientists are pretty sure that something awfully big slammed into the planet about 66 million years ago, but many suggest that headlong volcanic activity may also have played a major role in the demise of our giant, feathered friends.
New exploer attempts to throw cold water on the volcanism theory – but don’t hope this single study to close the case.
The new study, revealed Monday in Nature Geoscience, uses modeling to show that the climate change caused by continental flood basalts – the massive, long-lasting volcanic eruptions that were occurring around the same time as the great asteroid effect – would have been relatively minor.
When they tried to make statements about how more volcanism contributed – it was all very qualitative,” lead study Anja Schmidt of the University of Leeds told The Post. “So I wanted to put some numbers to it.”
Schmidt and her colleagues gathered available data from last studies to calculation the sulphur dioxide that would be emitted by these eruptions, which lasted for years and could spout out 150 Olympic-size swimming pools worth of lava per minute.
In contrast to last studies, some of which suggested that really drastic cooling would occur because of these emissions, maybe even enough to kill all plants and animals, we find that perhaps the situation wasn’t that grim,” Schmidt said. We see some cooling, but I suggest that most plants and animals would have been fine in most parts of the world.
Schmidt’s model showed that global temperatures would drop by about 4.5 degrees Celsius, which is the difference between our average temperature now and during the last ice age, so some areas definitely would have got quite chilly. But according to the same model, the change would abate after just 50 years. For the cooling to last long enough and be severe enough to really cause a mass extinction, Schmidt said, the eruptions would have to last for a century or more – which is much long than anyone has ever estimated.
Princeton University’s Gerta Keller, who also studies the role of volcanism in the death of the dinosaurs, called the new study an “excellent effort” but was skeptical of its conclusions. We don’t know enough about when these eruptions occurred and how long they lasted to draw conclusions from such models.
I’m afraid that until we have more precise age data for all major lava flows preceding the mass extinction and the periods of non-activity in between lava flows, no model, however well conceived, can realistically evaluate the biotic and circumjacent impact of the large continental flood basalt provinces, Keller told The Post in an email. I bet that in a few years when this data becomes available, the same model based on high-precision age dating of lava flows will yield significantly different conclusions.
Schmidt said that a better understanding of the tempo of the eruptions is the next step. She also pointed out that her study focused on one gas – sulphur dioxide – that is known to have major climate effect. It’s possible that other, less harmful gases emitted by continental flood basalts would have a cumulative impact on the climate and contribute to a mass extinction. Some exploer have suggested that the famous asteroid impact may have actually accelerated volcanic activity, which is another avenue to investigate.
As the Earth edges toward another mass extinction – this one almost certainly caused by the discharge of human industry – Schmidt believes it’s important to pin down a culprit for the dying of the dinosaurs.
A group of really powerful and intriguing species went destructed, and it’s important to understand because it happened very fast, and we don’t have a universal agreement about how, Schmidt said. “We really have no idea.”