A mass extinction that wiped out three quarters of all life on Earth just before the dinosaurs took over may have been caused by a global rapid cooling rather than a warming climate, scientists say
How extreme cold, not heat, triggered the mass extinction 200 million years ago – paving the way for the rise of the dinosaurs…
The mass extinction before the dinosaurs took over may have been caused by extreme cold rather than extreme warmth, as originally thought.
It’s widely believed that the End Triassic Extinction, which wiped out three-quarters of all life on Earth over 200 million years ago, was caused by the build up of carbon dioxide from eruptions over many millennia, raising temperatures to unsustainable levels for many creatures, and acidifying the oceans.
- The Sixth Extinction: what it is, what is causing it – and how many species we are losing
- “99 per cent of the species that have ever lived have gone extinct”: Why life needs extinction and how it can be a force for good
However, a new paper in the Proceedings of the National Academy of Sciences says the opposite: that early, rapid cooling, not warming, was the main culprit.
The study by Columbia Climate School researchers presents evidence that that instead of stretching over hundreds of thousands of years, the first pulses of lava that ended the Triassic were short but intense events lasting less than a century each.
For the study, the researchers compared Central Atlantic Magmatic Province (CAMP) volcanic rocks from Morocco, the Bay of Fundy in eastern Canada/US, and the Newark Basin in New Jersey, US.
Studying the magnetic properties of the rocks that would have been affected by Earth’s drifting magnetic pole, they determined that the CAMP lava deposits were spread over just 40,000 years.
Because the magnetic particles in individual rock layers were aligned in a single direction, they deduced that they were laid down in pulses lasting less than a century.
These concentrated eruptions released so many sulfates so quickly that the sun was largely blocked out, causing temperatures to plunge. These volcanic winters may have killed off many of the world’s species long before the temperatures eventually started to rise due to CO2 released in subsequent eruptions.
“Carbon dioxide and sulphates act not just in opposite ways, but opposite time frames,” says lead author Dennis Kent of the Columbia Climate School in New York. “It takes a long time for carbon dioxide to build up and heat things, but the effect of sulphates is pretty much instant. These events happened in the span of a lifetime.”
Similar volcanic winter conditions have occurred in the aftermath of the eruption of Iceland’s Laki volcano in 1783, which resulted in one of the coldest winters ever recorded and crop failures around the world.
“The magnitude of the environmental effects are related to how concentrated the events are,” study co-author Paul Olsen, a palaeontologist at Lamont-Doherty, said in the paper.
“Small events spread out over [tens of thousands of years] produce much less of an effect than the same total volume of volcanism concentrated in less than a century. The overarching implication being that the CAMP lavas represent extraordinarily concentrated events.”
According to the study, these concentrated events over 200 million years ago were instrumental in bringing about the end of the Triassic period and the beginning of the Jurassic – the period when dinosaurs arose to dominate the planet.
Discover more fascinating dinosaur facts
- Dinosaur teeth: what were they like, how ferocious were they – and what do they tell us about a dinosaur’s diet?
- Were dinosaurs good parents – and how on earth do we know?
- Dinosaur sex: how these huge animals mated with all those dangerous spikes, claws and plates
- Do we know what dinosaurs sounded like?
- Best dinosaur documentaries to watch