Our recent discussion of the Cretaceous extinction event included comments on the heat generated by the asteroid/comet that ended the reign of the dinosaurs. An article published in Geology Times earlier this month is very much to the point on that subject:
Study provides new evidence ancient asteroid caused global firestorm on Earth (4/1/2013)
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| A new CU-Boulder study shows that an asteroid believed to have smacked Earth some 66 million years ago likely caused a global firestorm that led to extensive plant and animal extinctions. - Illustration courtesy NASA/JPL |
A new look at conditions after a Manhattan-sized asteroid slammed into a region of Mexico in the dinosaur days indicates the event could 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, says a new University of Colorado Boulder study.
Led by Douglas Robertson of the Cooperative Institute for Research in Environmental Sciences, or CIRES, the team 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 -- about the temperature of an oven broiler element -- killing every living thing not sheltered underground or underwater.
The CU-led 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 asteroid struck Earth and the cataclysmic fires are believed to have occurred. The CU 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, Robertson said.
"Our data show the conditions back then are consistent with widespread fires across the planet," said Robertson, a research scientist at CIRES, which is a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration. "Those conditions resulted in 100 percent extinction rates for about 80 percent of all life on Earth."
The full article can be found at http://www.geologytimes.com/research/Study_provides_new_evidence_ancient_asteroid_caused_global_firestorm_on_Earth.asp
Earlier descriptions of the event have hypothesized temperature swings moving from heat to cold, and a more extended period of die-off lasting months or more, but under this scenario the mass extinctions may have been completed in a matter of hours or a few days. What strikes me as as significant here is the statement that everything would be killed that was not sheltered underground or under water. This is potentially a testable idea. Were the animals that survived the extinction the type of creatures that could find such shelter? As I understand it, the dinosaurs so thoroughly dominated the environment that the mammals of the day did tend to live in burrows,. Some other survivors come to mind, like the frogs that could bury themselves in mud. The dinosaurs live on in our present day birds, and I suppose their mobility would have allowed at least a few of them to seek refuge in caves.
One animal that has been held up as an argument against the idea that only the burrowers and shelter living animals survived is the crocodile, which must surely have lived in the open without any options for finding shelter in its limited environment. But there was a documentary a few years ago on one of the science channels showing how the diverse animal community around a water hole in Africa was effected when the stream began to dry up, and it showed something remarkable about the crocodiles. As the stream dwindled and the pond dried, the hippos wandered off to die, the antelope and lions disappeared, the monkeys becaome skeletons and the dry pond was the final resting place for almost all of the crocs. But just a few of the crocodiles dug into the embankments and created holes where they could live with some minimal moisture in a near hibernation mode. They were the only survivors when the water returned.
Just wondering if people had thoughts on this or knew of research.
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