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Dinosaurs 'victims of double disaster'

Press AssociationPress Association 5/07/2016

A double dose of cataclysmic bad luck killed off the dinosaurs, new evidence appears to confirm.

Evidence of ancient climate change suggests the creatures were first weakened by massive volcanic eruptions and then finished off by a giant meteor smashing into the Earth 150,000 years later.

The two events led to a mass extinction 66 million years ago that wiped out all the dinosaurs apart from those that later evolved into birds.

In total, roughly three-quarters of the Earth's plant and animal species disappeared.

Scientists have debated the cause of the catastrophe at the end of the Cretaceous period for decades.

Many believe a six mile-wide asteroid or comet striking the Earth off the coast of Yucatan, Mexico, was responsible.

Others have pointed to a series of powerful volcanic eruptions in India that poured sulphurous gas into the atmosphere, poisoning the air and oceans and altering the climate.

The new evidence supports a third theory that both events were to blame.

Lead scientist Dr Sierra Petersen, from the University of Michigan, said: "We find that the end-Cretaceous mass extinction was caused by a combination of the volcanism and meteorite impact, delivering a theoretical 'one-two punch'."

The scientists analysed the composition of fossil shells to reconstruct ocean temperatures in Antarctica around the time of the dinosaurs' extinction.

They found two abrupt warming spikes - the first coinciding with eruptions from the Deccan Traps volcanic region in India and the second with the Mexican meteor impact.

Antarctic ocean temperatures jumped by about 7.8C during the eruption event, probably because of enormous amounts of heat-trapping carbon dioxide being released into the atmosphere, said the researchers writing in the journal Nature Communications.

The second warming spike was smaller and occurred roughly 150,000 years later, around the time the meteor struck.

"This new temperature record provides a direct link between the volcanism and impact events and the extinction pulses - that link being climate change," said Dr Petersen.

A "press-pulse" mechanism was likely to have killed off the dinosaurs, the research suggests.

First came the "press" of gradual climate change due to the Deccan Traps eruptions. This was followed by the instantaneous "pulse" of an object several miles wide slamming into the Earth.

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