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Scientists find more answers on 66 million-year-old meteorite wildfire mystery

Scientists have discovered the meteorite that wiped out Earth’s dinosaurs instantly ignited forest wildfires up to thousands of kilometres from its impact zone.

 

September 7, 2022
By Katharine Hay
7 September 2022

The meteorite that wiped out Earth’s dinosaurs instantly ignited forest wildfires up to thousands of kilometres from its impact zone, scientists have discovered.

The roughly six-mile-wide meteorite struck the Yucatan peninsula in what is now Mexico at the end of the Cretaceous Period 66 million years ago.

Its devastating impact brought the reign of the dinosaurs to an abrupt end by triggering their sudden mass extinction, along with the end of almost three-quarters of the plant and animal species then living on Earth, scientists say.

Debate has surrounded the circumstances behind the devastating wildfires known to have been caused by the strike, with several theories as to how and when they started, and the extent of their impact.

By analysing rocks dating to the time of the strike, a team of geoscientists from the UK, Mexico and Brazil has recently discovered that some of the fires broke out within minutes, at most, of the impact, in areas stretching up to 2,500km (1,553 miles) or more from where Earth was hit.

In a newly published study, they said wildfires that broke out in coastal areas were short-lived, as the backwash from the mega-tsunami caused by the impact swept charred trees offshore.

And by studying the fossilised tree bark, the geoscientists discovered that fires had already begun by the time the trees were washed away soon after the initial impact.

They concluded this was either due to a fireball of epic magnitude, or by the heat from droplets of melted rock falling back through the atmosphere in the immediate aftermath of impact.

Professor Ben Kneller, from the University of Aberdeen’s School of Geosciences, is among the co-authors of the latest study, which included scientists from the Autonomous University of Mexico, Federal University of Rio Grande do Sul, University of Leeds and University of Manchester.

He said: “Until now it has not been clear whether the fires were caused as a direct result of the impact or subsequently, as vegetation killed by the post-impact darkness caused by the debris thrown up into the atmosphere was set ablaze by things such as lightning strikes.

“By assembling this international team we were able to apply a unique combination of chemical, isotopic, palaeontological, palaeobotanical, chemical and spectroscopic techniques, along with geological mapping, firstly to confirm that the rocks we analysed date precisely from the impact.

“We then analysed fossilised bark still attached to the tree trunks to determine the extent of the burning, finding that the bark was already charred as the trees were washed away by the impact-related tsunami. This shows that the fires must have begun within minutes, at most, of impact.

“Ultimately our research confirms how and when these devastating fires were begun and paints a vivid and quite terrifying picture of what happened in the immediate aftermath of the meteorite strike.”

The study was supported by Shell Brazil under the Brazilian Government’s Science without Borders programme, and published in the journal Scientific Reports.

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