Dinosaur-killing asteroid started wildfires, triggered tsunamis: Study

PTI, Sep 11, 2019, 2:10 PM IST

Houston: The asteroid that wiped out the dinosaurs about 65 million years ago slammed into the Earth with the equivalent power of 10 billion atomic bombs, charred trees thousands of miles away, and triggered a mega-tsunami, according to a study.

The research, published in the journal Proceedings of the National Academy of Science, looks at hundreds of feet of rocks that filled the impact crater within the first 24 hours after impact.

Scientists believed that the asteroid impact in the Yucatan Peninsula in Mexico started wildfires, triggered tsunamis, and sent out so much sulphur into the planet’s atmosphere that it blocked out the sun, and caused global cooling which ultimately killed the dinosaurs, the study noted.

Inspecting the Chicxulub impact crater in the peninsula, researchers from the University of Texas Institute for Geophysics (UTIG) in the US found bits of charcoal, rock piles brought in by the tsunami’s backflow, and oddly absent sulphur — adding evidence to the suspected aftermath events.

The study noted that within hours of the asteroid impact, much of the material filling the crater was either produced at the impact site, or was swept in by seawater drawn into the crater by the mega-tsunami.

Commenting on the research, Antoine Bercovici of the Smithsonian National Museum of Natural History, who was not related to the team, told PTI in an email that the important discovery to note was the vast amount of sediments that back-filled the impact crater.

According to the researchers, about 425 feet of material — among the highest ever encountered in the geologic record — filled the crater within a day.

Sean Gulick, lead author of the study, said that these evidences are all part of a rock record that offers the most detailed look yet into the aftermath of the catastrophe.

Gulick described the impact as a short-lived inferno at the local level, followed by a long period of global cooling.

“We fried them and then we froze them. Not all the dinosaurs died that day, but many dinosaurs did,” Gulick said.

The researchers found charcoal and evidence of soil fungi within or just above layers of sand, showing signs that they were deposited by waters resurging in the mega-tsunami.

According to the study, this could indicate that the charred landscape was pulled into the crater with the receding waters of the tsunami.

The most important point to note from the analysis, the researchers say, is that the area surrounding the impact crater is full of sulphur-rich rocks while there was no sulphur in the core.

This, according to the researchers, could be because the impact vaporized the sulphur-bearing minerals at the impact site, releasing it into the atmosphere.

They noted that at least 325 billion metric tons of material would have been released into the atmosphere due to the impact.

The changes made to the atmosphere triggered global climate change, causing a mass extinction that killed off the dinosaurs along with nearly 75 per cent of life on the planet at the time, according to the researchers.

According to Bercovici, the study further supports that both darkness and cooling happened after the impact, and that the timing of the events was very short, on the scale of several years.

Another important thing to note from the study is the identification of charcoal and polyaromatic hydrocarbons (PAHs), which the researchers claimed as indicative of wildfire, Bercovici said.

He cautioned that while PAH is good evidence of wildfire, charcoal does not necessary support the hypothesis.

The research team “describe a major impact-induced tsunami, and the backwash of that wave would bring a lot of material from the continent (erosion and run-off). It is very possible that the charcoal/wood fragments are coming from reworked material from land, as these particles are extremely common in soil and terrestrial rock of that time period,” Bercovici added.