About 65 million years ago, an asteroid hit our planet. We know it ended the reign of the dinosaurs on Earth, and now new research has concluded that it also instantly started forest fires up to 2,500 km from the impact zone.
A devastating impact
The about 10-kilometer-wide asteroid hit the Yucatan Peninsula in what is now Mexico at the end of the Cretaceous period. The impact crater we know as the Chicxulub crater and this event triggered the sudden mass extinction of the dinosaurs , along with nearly three quarters of the plant and animal species then living on Earth.
The circumstances behind the devastating wildfires known to have been caused by this collision have long been on, with various theories as to how and when they started, and the extent of their impact. In the new work, by analyzing various rocks dating from the time of the impact, a team of geoscientists from the UK, Mexico and Brazil has found that some of the fires broke out within minutes of the impact and spread up to 2 500 kilometers from the center of impact.
The study, published in Scientific Reports, describes how scientists from the UK, Mexico and Brazil first collected and dated shales from deposits in Baja California, Mexico.
By studying the charred and fossilized bark of the trees washed away by the mega-tsunami after the impact, the research team found that the fires had already burned the trees before they were washed away and buried in the tsunami debris. They concluded that this was due to the impact fireball or heat from droplets of molten rock that fell through the atmosphere immediately after impact.
“By bringing together this international team we were able to apply a unique combination of chemical, isotopic, paleontological, paleobotanical, chemical and spectroscopic techniques, along with geological mapping, to firstly confirm that the rocks we analyzed date precisely from the impact,” explains geoscientist Ben Kneller, co-author of the work.
The shale deposits contained a high concentration of iridium, as well as fungal and fern spores, which are indicators of a meteorite impact and resulting mega-tsunami that churned up the sediments. They also contained fossilized fragments of tree trunks, parts of which had charred at temperatures above 1,000°C.
“Until now it has been unclear whether the fires were caused as a direct result of the impact or later, as post-impact dead vegetation” and the darkness caused by debris thrown into the atmosphere was ignited by elements such as lightning. Ultimately, our research confirms how and when these devastating fires started and paints a vivid and rather frightening picture of what happened in the immediate aftermath of the meteor impact,” says Kneller.
Scientists determined that the bark was already charred when the trees were swept away by the mega-tsunami, indicating that the fires had started before the wave arrived . “This shows that the fires must have started within a few minutes, at most, of the impact ,” the expert concluded.
Referencia: Santa Catharina, A., Kneller, B.C., Marques, J.C. et al. Timing and causes of forest fire at the K–Pg boundary. Sci Rep 12, 13006 (2022). https://doi.org/10.1038/s41598-022-17292-y