Chicxulub, an asteroid that collided with the Earth 66 million years ago and is believed to wipe out the dinosaurs, may have triggered a global firestorm that would have burned every twig, bush and tree on Earth and led to the extinction of 80 percent of all Earth’s species, according to a recent research published online in the Journal of Geophysical Research-Biogeosciences.
A research team led by Dr Owen Toon from the University of Colorado Boulder used models that show the collision would have vaporized huge amounts of rock that were then blown high above Earth’s atmosphere. The re-entering ejected material would have heated the upper atmosphere enough to glow red for several hours at roughly 2,700 degrees Fahrenheit killing every living thing not sheltered underground or underwater.
The team developed an alternate explanation for the fact that there is little charcoal found at the Cretaceous-Paleogene, or K-Pg, boundary some 66 million years ago when the Chicxulub asteroid struck Earth and the cataclysmic fires are believed to have occurred. The researchers found that similar studies had corrected their data for changing sedimentation rates.
“When the charcoal data were corrected for the same changing sedimentation rates they show an excess of charcoal, not a deficiency,” said Dr Douglas Robertson of the Cooperative Institute for Research in Environmental Sciences.
“Our data show the conditions back then are consistent with widespread fires across the planet. Those conditions resulted in 100 percent extinction rates for about 80 percent of all life on Earth.”
Geological evidence indicates the asteroid collided with Earth about 66 million years ago and carved the Chicxulub crater in Mexico’s Yucatan Peninsula that is more than 110 miles in diameter. In 2010, experts from 33 institutions worldwide issued a report that concluded the impact at Chicxulub triggered mass extinctions, including dinosaurs, at the K-Pg boundary.
“The conditions leading to the global firestorm were set up by the vaporization of rock following the impact, which condensed into sand-grain-sized spheres as they rose above the atmosphere. As the ejected material re-entered Earth’s atmosphere, it dumped enough heat in the upper atmosphere to trigger an infrared ‘heat pulse’ so hot it caused the sky to glow red for several hours, even though part of the radiation was blocked from Earth by the falling material,” Dr Robertson said.
“But there was enough infrared radiation from the upper atmosphere that reached Earth’s surface to create searing conditions that likely ignited tinder, including dead leaves and pine needles. If a person was on Earth back then, it would have been like sitting in a broiler oven for two or three hours.”
“The amount of energy created by the infrared radiation the day of the asteroid-Earth collision is mind-boggling. It’s likely that the total amount of infrared heat was equal to a 1 megaton bomb exploding every four miles over the entire Earth.”
“A 1-megaton hydrogen bomb has about the same explosive power as 80 Hiroshima-type nuclear bombs,” he said. “The asteroid-Earth collision is thought to have generated about 100 million megatons of energy.”
Some researchers have suggested that a layer of soot found at the K-Pg boundary layer roughly 66 million years ago was created by the impact itself. But the team calculated that the amount of soot was too high to have been created during the massive impact event and was consistent with the amount that would be expected from global fires.
Bibliographic information: Douglas S. Robertson et al. K-Pg extinction: Reevaluation of the heat-fire hypothesis. Journal of Geophysical Research: Biogeosciences, published online March 26, 2013; doi: 10.1002/jgrg.20018