Double whammy: Dinosaurs wiped out by one-two death punch delivered by colossal volcanic eruptions AND meteorite impacts
A single massive meteorite strike has always been considered responsible for wiping out the dinosaurs, but now scientists believe most of the creatures had already been killed by colossal eruptions from a volcano range three times bigger than France by the time it struck.
Researchers from Princeton University have found evidence that eruptions from the Deccan Traps, a primeval volcanic range in western India, devastated the Earth 65million years ago producing the largest lava flows in Earth’s history and filling the atmosphere with climate-altering carbon dioxide and sulphur dioxide.
As if this wasn’t bad enough, there were several more meteor strikes and, 300,000 years later, more eruptions that would ultimately make the Earth uninhabitable for 500,000 years.
Hell on Earth: The dinosaurs weren't killed off by a single meteorite strike, but by massive volcanic eruptions
Evidence for the mass extinction being caused by volcanoes comes from a trail of dead plankton the researchers found that spanned half a million years.
The team, led by led by Princeton Professor of Geosciences Gerta Keller, report this month in the Journal of the Geological Society of India that marine sediments from Deccan lava flows show that the population of a plankton species widely used to gauge the fallout of prehistoric catastrophes plummeted nearly 100 per cent in the thousands of years leading up to the mass extinction.
This eradication occurred in sync with the largest eruption phase of the Deccan Traps - the second of three - when the volcanoes pumped the atmosphere full of climate-altering carbon dioxide and sulphur dioxide, the researchers report.
The Deccan Traps: Ancient volcanoes here killed off most of the dinosaurs, according to scientists
TIME-LINE OF DESTRUCTION
67.5million years ago
Moderate eruptions from Deccan Traps make Earth a difficult place for dinosaurs to live on.
65million years ago
Massive volcanic eruptions kill 80 per cent of life on Earth – then a meteor the size of Everest strikes, along with several other large space rocks.
300,000 years later
Yet more volcanic eruptions render Earth's environment so hostile that it would take half a million years for life to flourish again.
The less severe third phase of Deccan activity kept the Earth nearly uninhabitable for the next 500,000 years, the researchers report. A substantially weaker first phase occurred roughly 2.5 million years before the second-phase eruptions.
Another group based in Keller's lab found evidence in Indian sediment of a meteorite strike from the time of the mass extinction that would have been sufficient to finish off the few but weakened species that survived the Deccan eruptions, according to a report in the journal Earth and Planetary Science Letters in October.
From this sediment - located in Meghalaya, India, more than 600 miles east of the Deccan Traps – scientists have deduced that Earth during this period was a harsh environment of acid rain and erratic global temperatures.
Taken together, Keller said, the Princeton findings could finally put to rest the theory that the mass-extinction event - known as the Cretaceous-Tertiary, or KT, for the periods it straddles - was triggered solely by a large meteorite impact near Chicxulub in present-day Mexico.
That impact - which occurred around the time of the second-phase Deccan eruptions - is thought to have been two million times more powerful than a hydrogen bomb and generated an enormous dust cloud and gases that radically altered the climate.
Keller has long held that the Chicxulub impact was not catastrophic enough to cause the KT mass extinction - the newest work from her lab, however, shows that the largest Deccan eruptions were.
Once three-times larger than France, the Deccan Traps were a primeval volcanic range in western India that pumped Earth's atmosphere full of climate-altering carbon dioxide and Sulphur dioxide
‘Our work in Meghalaya and the Deccan Traps provides the first one-to-one correlation between the mass extinction and Deccan volcanism,’ said Keller.
‘We demonstrate a clear cause-and-effect relationship that these massive volcanic eruptions were far more destructive than previously thought and could have caused the KT mass extinction even without the addition of large meteorite impacts.
‘But given the environmental instability caused by the massive Deccan eruptions, an impact could easily have killed off the few survivor species at the end of the Cretaceous. It would have been a double whammy.’