Geologists and paleontologists have been kicking around an idea for the past several decades which threatens to overturn the scientific canon surrounding the demise of the dinosaurs. Rather than an asteroid impact, say a growing number of researchers, it was extreme volcanic activity that drove the dinosaurs to extinction. Critics complain that there isn't enough evidence to support such a wild hypothesis — but new data is emerging in support of the claim.
The going theory, of course, is that a giant asteroid struck the Yucatan region of Mexico during the late Cretaceous period — a cataclysmic event that instigated a mass extinction across the entire globe. This theory, which gained popular acceptance several decades ago, supplanted the pre-existing notion that it was an ice age that drove the dinosaurs to extinction.
But it also cast aside the theory that volcanism might have been responsible.
The Deccan Traps
But now, the idea is resurfacing — and new evidence is shedding light on the possibility.
Back in 2008, Princeton geoscientist Gerta Keller rekindled the discussion by hypothesizing that dinosaurs died out gradually from climate change — what was caused by a series of severe volcanic eruptions in India at the end of the Cretaceous period.
Interestingly, this happened about 300,000 years after the Chicxulub impact in the Yucatan. Keller claims that the asteroid was too small, and that it had little to no effect on life. The real extinction action, argues Keller, didn't happen until a vast mountain range in India unleashed its pent-up fury.
Called the Deccan Traps, it's a rocky area that still covers much of India today. During the time of its eruptions — a phase that lasted tens of thousands of years — it spewed lava over an area the size of France, if not larger.
And indeed, the geological evidence points to a staggering geological event. According to Keller, these massive volcanic mountains poured out a relentless stream of lava that started to layer upon itself. Keller suggests that the total volume in cubic miles was greater than the Rockies and the Sierras combined.
Work by other researchers affirm Keller's claim; volcanologists Vincent Courtillot, Steve Self, Mike Widdowson, and Anne Lise Chenet have suggested that the lava eruptions occurred in pulses, with each lasting for about 10 to 100 years and in a phase that lasted anywhere from 10,000 to 100,000 years. During the eruptions, the volcanoes would have shot sulphur dioxide and carbon dioxide into the atmosphere, while the lava would have encroached on an area up to 650 miles (1,045 km) across.
So in addition to local destruction, the gasses would have caused climate cooling and eventual ocean acidification.
As LiveScience is reporting, Keller's team recently analyzed ancient lava-filled sediments buried nearly two miles (3.3 km) below the ocean surface — samples that contained fossils from the K-T Boundary period, the time when the dinosaurs went extinct.
What the researchers discovered was that plankton species began to dwindle over the course of this time. The environmental stresses exerted on marine life resulted in plankton that were smaller and less elaborate — trends that were happening in the years after the eruptions.
Most species became extinct during this time, but a tough new plankton called Guembilitria exploded onto the scene. Keller's team found evidence of this species in marine sediments from Egypt, Israel, Spain, Italy, and Texas. During this time, Guembilitria represented between 80 to 98% of the fossils.
Tia Ghose explains the implications:
"We call it a disaster opportunist," Keller told LiveScience. "It's like a cockroach - whenever things go bad, it will be the one that survives and thrives."
Guembilitria may have come to dominance worldwide when the huge amounts of sulfur (in the form of acid rain) released by the Deccan Traps fell into the oceans. There, it would've chemically binded with calcium, making that calcium unavailable to sea creatures that needed the element to build their shells and skeletons.
Around the same time in India, fossil evidence of land animals and plants vanished, suggesting the volcanoes caused mass extinctions on both land and in the sea there.
Keller's research also suggests that it took the Earth about half a million years to recover, mostly on of account of at least four additional Deccan eruptions, which occurred about 280,000 years after the initial mass extinction.
Read more at LiveScience.
Other source: National Science Foundation.
Top image via. Image: Credit: National Science Foundation, Zina Deretsky & Gerta Keller.