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Sixty-six million years ago, a 5-mile (8km) wide asteroid crashed into the Earth at 70,000 miles per hour (112,600 km/h), vapourising upon impact.

Scientists have long believed that heavy dust from the impact blocked out the sun, setting off a disastrous chain of events that led to the extinction of the dinosaurs.

But now researchers in the US have found more evidence for the theory that major volcanic eruption began just before the impact, possibly also playing a role in the extinction.

Researchers in the US have found more evidence for the theory that major volcanic eruption began just before the impact, possibly also playing a role in the extinction

The team precisely dated rocks from the Deccan Traps - a region of west-central India that preserves remnants of one of the largest volcanic eruptions on Earth.

They looked for rock that might contain zircon - a uranium-containing mineral that forms in magma after an eruption, and that can be used as a very precise dating tool.

The researchers collected more than 50 samples of rocks from the region representing the largest pulse of volcanism.

Samples from both the bottom and top of this volcanic layer contained zircon, allowing the team to pinpoint the timing of the beginning and end of the Deccan Traps eruptions.

The team precisely dated rocks from the Deccan Traps - a region of west-central India that preserves remnants of one of the largest volcanic eruptions on Earth

Based on their analysis, the researchers determined that the eruption began 250,000 years before the asteroid strike and continued for 500,000 years after the giant impact.

Scientists at MIT and Princeton University calculated that the volcano spewed out a total of 932,000 square miles (2.4 million square km) of lava.

The immense volcanism may have released dangerous levels of volatile chemicals into the air, poisoning the atmosphere and oceans, they say.

'If models of volatile release are correct, we're talking about something similar to what's happening today: lots of carbon dioxide being emitted into the atmosphere very rapidly,' said Michael Eddy, a graduate student at MIT.

'Ultimately what that can do is lead to ocean acidification, killing a significant portion of plankton — the base of the food chain. If you wipe them out, then you'd have catastrophic effects.'

It's long been known that a major eruption occurred in India around the time of the end-Cretaceous extinction, but this event had never been precisely dated.

Based on the new, more precise dates for the Deccan Traps, the researchers believe the massive eruptions may have played a significant role in extinguishing the dinosaurs.

'I don't think the debate will ever go away,' said Sam Bowring, a Professor of Earth and Planetary Sciences at MIT.

'The [asteroid] impact may have caused the extinction. But perhaps its effect was enhanced because things were softened up a bit by the eruption of these volcanoes.'

Before 1980, the exact cause of dinosaurs' demise was unknown; one hypothesis proposed that they were killed off by massive volcanic eruptions.

But the 1980 discovery in Italy of iridium, a rare element primarily found in extra-terrestrial materials, suggested otherwise.

'The story that is emerging is that perhaps both might have been involved,' Professor Bowring says. 'Perhaps the end of the dinosaurs was caused by a one-two punch.'

The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India and one of the largest volcanic features on Earth