Researchers Explain What Happened When Dinosaur-Killing Asteroid Hit Earth

James Marshall
September 10, 2019

"We interpret this section to represent the first day post impact, which by the definition of the geologic time scale, makes it the first day of the Cenozoic since the Cretaceous ended the moment the asteroid struck", Gulick says.

This is an artist's interpretation of the asteroid impact.

First, the impact site was a fiery hellscape.

"It's so rare in geology that we get to look at the rocks and read a story on the timescale of hours", Sean Guelick, the study's first author from the University of Texas at Austin, told Gizmodo.

Most of the material that filled the crater within hours of impact was produced at the impact site or was swept in by seawater pouring back into the crater from the surrounding Gulf of Mexico. As the water from the sea rushed back into the hole, it created a layer of melted stone over the layer of accumulated rock at the bottom of the crater.

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The melted rock indicates that the asteroid hit with the force of 10 billion atomic bombs, setting forests aflame for thousands of kilometres, and triggering a tsunami that reached as far as current IL. The blast ignited trees and plants that were thousands of miles away and triggered a massive tsunami that reached as far inland as IL.

Perhaps most surprising were the soil and charcoal particles they found in the rock, evidence that a tsunami returned to the site of the impact from shore. This suggests that the charred landscape was pulled into the crater with the receding waters of the tsunami. Scientists found melted and broken rocks such as sandstone, limestone and granite - but no sulfur-bearing minerals, despite the area's high concentration of sulfur containing rocks.

Three quarters of animal species were wiped out - including the dinosaurs. The impact triggered wildfires which were then doused by the waves of the tsunami and the burnt charcoal was carried to the crater.

Commenting on the findings, Jay Melosh, from Purdue University and who was not involved in the study, said this research helps expand our understanding of what happened when the asteroid hit. But he pointed out that this is just one paper about one core. This suggests that these rocks were vaporised by the impact, expelling tremendous amounts of sulphate aerosols into the atmosphere, where they blocked the light of the Sun, dramatically cooling Earth's temperatures for years after. The impact did cause devastation in the locality of the impact but the global extinction took place due to the climate change caused by the release of massive volumes of sulphur, nearly 325 billion metric tonnes. This caused an unprecedented cooling event which, in turn, led to the extinction of the (non-avian) dinosaurs.

The impact blasted so much sulphur into the atmosphere it blocked out the sun, say the British and USA led team. To put that in perspective, that's about four orders of magnitude greater than the sulfur that was spewed during the 1883 eruption of Krakatoa - which cooled the Earth's climate by an average of 2.2 degrees Fahrenheit for five years. If you were elsewhere on Earth the first effect might well be the natural disaster energy arriving through the ground from the impact or perhaps the arrival of ejecta from the crater raining down and causing heating and wildfires.

The research was funded by a number of global and national support organizations, including the National Science Foundation.

Other reports by Click Lancashire

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