An asteroid was to blame for the extinction of the dinosaurs rather than a volcano, a new study of ancient gas release has found.
The dinosaurs were wiped out by the asteroid strike around 66 million years ago when the city-sized rock crashed into the coast of Mexico near the town of Chicxulub.
It kicked up a colossal dust and soot cloud which caused climate change and wiped out an estimated 75 percent of all animal and plant life.
It has been suggested that lava spewing out of a volcanic region in India known as the Deccan Traps had released greenhouse gases and fatally raised global temperatures.
However, US researchers found that most of the gas release occurred long before the mass extinction, which is known as the Cretaceous-Paleogene (K–Pg) event.
Given this, the environmental impacts of the volcanism likely did not contribute to the death of the dinosaurs, the international team has concluded.
‘A lot of people have speculated volcanoes mattered to [the]K–Pg, and we’re saying, “No, they didn’t”,’ said geologist Pincelli Hull of Yale University in Connecticut.
It is commonly accepted by the scientific community that the extinction at the end of the Cretaceous happened after a six-mile-wide asteroid slammed into the Earth.
At least 75 per cent of all species on Earth at the time vanished — including the dinosaurs — a mass dying that is said to have coincided with the volcanic activity.
‘Volcanoes can drive mass extinctions because they release lots of gases, like sulphur and carbon dioxide, that can alter the climate and acidify the world,’ Dr Hull said.
‘But recent work has focused on the timing of lava eruption rather than gas release.’
Instead, Dr Hull and colleagues compared global temperature changes and the record of carbon chemicals from marine fossils with models of the climatic effect of massive-scale carbon dioxide release.
They found that at least 50 per cent of the gas release occurred well before the asteroid impact — suggesting that the latter had to be the sole driver of the extinction.
‘Volcanic activity in the late Cretaceous caused a gradual global warming event of about two degrees, but not mass extinction,’ said paper co-author and Yale geochemist Michael Henehan, who compiled the temperature records.
‘A number of species moved toward the North and South poles, but moved back well before the asteroid impact,’ he added.
Recent work on the Deccan Traps in west-central India — the largest volcanic feature on the face of the Earth — have also pointed to massive eruptions having occurred in the immediate aftermath of the K–Pg mass extinction.
These results have puzzled scientists because there is no warming event to match this activity.
However, the new study suggests an answer to this puzzle, as well.
‘The K–Pg extinction was a mass extinction and this profoundly altered the global carbon cycle,’ added paper author and Yale geochemist Donald Penman.
‘Our results show these changes would allow the ocean to absorb an enormous amount of CO2 on long time scales — perhaps hiding the warming effects of volcanism in the aftermath of the event.’
However, the researchers said that the volcanic gases may have played an important role in shaping the rise of different species after the extinction, rather than driving the initial event.
The full findings of the study were published in the journal Science.