Scientists Reveal Exactly What Killed the Dinosaurs

Dust was a major contributor to the extinction of the dinosaurs, scientists revealed in a new study.

Dinosaurs became extinct due to a series of chain reactions triggered by an asteroid that hit Earth 66 million years ago. It plunged Earth into a brutal winter, which led to the downfall of about 75 percent of all life on the planet. Vegetation was also starved of sunlight—this meant no more food, for herbivores or carnivores.

A study published in Nature Geoscience found that huge amounts of fine, silicate dust, produced from pulverized rock following the asteroid collision, could have played a more significant role in their extinction than originally thought.

"The fine silicate dust from pulverized rock generated by the Chicxulub impact most likely drove the last mass extinction event through the disruption of photosynthetic activity in land and ocean realms," Cem Berk Senel, lead author of the study and researcher at the Royal Observatory of Belgium, told Newsweek.

A huge amount of debris was released following the Chicxulub impact, but the exact impact of each kind has long been debated by scientists. Before now, researchers believed the sulfur released following the asteroid landing, as well as soot produced by wildfires that followed, were the main causes for this global winter.

But now, it looks like the dust was also a major contributor.

Researchers who evaluated a well-preserved amount of impact deposit, extracted from a site in North Dakota, found that there was a larger amount of dust released on impact than previously thought. The dust could have remained in the atmosphere for as long as15 years, contributing to Earth's cooling by as much as 15 degrees Celsius (59 degrees Fahrenheit).

The dust could also have impacted solar radiation, which in turn would have shut down photosynthesis for two years following the impact.

"For the first time, we produce a paleoclimate model that takes into account the real measurement size of the dust, obtained in North Dakota," Philippe Claeys, a geologist, planetary scientist and geochemist and professor at the Free University of Brussels, told Newsweek.

"The very fine particles we detected have a very long residence time in the atmosphere, up to 15 years, which is longer than that of [sulfur] components in fact. So fine pulverized silicate-rich dust, generated from the deeper layers within the rock, also played a major role [in cooling] the climate and [stopping] photosynthesis, leading to the demise of non-avian dinosaurs."

Claeys, who also worked on the study, said the findings weren't particularly surprising to the study authors, as the sheer volume of dust released following the Chicxulub impact was "gigantic."

The volume of dust was huge, Claeys said, measuring as much as 2000 [gross tonnage]. He said it was the most efficient element of blocking photosynthesis on land and oceans for two years.

"The earth cools significantly under the combined effect of [sulfur], soot and dust, after five years, effect of [sulfur] becomes less significant, however dust and soot [from wildfire] remain active for 15 years at least," he said. "Silicate dust is demonstrated in our paper to be the most efficient "blocker" of photosynthesis. It renders the atmosphere opaque to sunlight, hampering the plants photosynthetic process. So no more food for herbivores and carnivores....Our model shows that it takes two years for photosynthesis to return."

The extinction of the dinosaurs continues to fascinate scientists as it has always been unclear how the energy was released by the impact, and how it transferred to the biosphere, Claeys said.

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