Global warming 100 thousand years long and woody birds that died out along with trees - scientists have outlined new consequences, which led to the explosion of an asteroid that killed the dinosaurs.
Two articles on the consequences of the global catastrophe that killed the dinosaurs at the end of the Cretaceous period appeared simultaneously in two scientific journals. The Chicxulub crater with a diameter of 180 kilometers was discovered in 1987 on the Yucatan Peninsula - it is he who is considered the main evidence of a planetary cataclysm that happened 66 million years ago and caused the mass extinction of animals and plants on the planet.
This event had serious consequences for the evolution of fauna and flora on Earth, and therefore scientists often turn to the study of its various aspects. So, in August 2017, American scientists calculated that after the impact of a celestial body up to 10 kilometers in diameter, our planet spent about two years without sunlight. As calculations showed, about 15 trillion tons of ash and soot were thrown into the air, plunging the Earth into darkness.
In a new study published in the journal Science, scientists estimated the amount of carbon dioxide released into the atmosphere after the cataclysm and the duration of global warming caused by it.
These findings are directly related to the question of how long the planet can recover from exposure to humanity, emitting greenhouse gases, according to Kenneth McLeod, study author at the University of Missouri.
According to modern concepts, immediately after the impact of the asteroid, the temperature of the planet rose sharply, and then fell for months and years due to the fact that the raised dust prevented the penetration of sunlight.
Ultimately, the emitted carbon dioxide led to a long-term warming of the climate.
To estimate the amount of gas emitted, scientists analyzed the fossil remains of teeth, scales and bones found in Tunisia and dating back to that era.
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“This place is famous for the presence of remarkable finds dating back to the time period that we are researching - the mass extinction after the Chicxulub event,” explained MacLeod. In their work, the scientists measured the ratios of various oxygen isotopes in the found samples.
“We measure the ratio of isotopes oxygen-16 and oxygen-18. As the temperature increased, the proportion of the light isotope, oxygen-16, in the minerals increased. One thousandth in this respect corresponds to an increase in temperature of 4.5-5 degrees,”the scientist explained.
The researchers studied 40 samples: 10 belonging to the period 50 thousand years before the explosion, 20 formed in the first 100 thousand years after and 10 in the next 200 thousand years. Based on the data obtained, scientists have come to the conclusion that the emitted carbon dioxide was enough to cause global warming for 100 thousand years. According to their estimates, the average temperature on the planet during that period rose by 5 degrees.
Another study on the survival of fauna after this cataclysm was published in the journal Current Biology.
One of the questions, which until recently scientists had no answer - why did the catastrophe not kill all the birds that lived on Earth? So, among the survivors were various birds living on the surface of the earth - the ancestors of ducks, chickens, and ostriches. The birds living in the trees, who used them as shelters, died, as the forests themselves disappeared.
To prove this hypothesis, Daniel Field of the University of Bath (UK) had to collect information literally by the bones. Together with colleagues, he studied the structure of many modern birds, the bones of long-extinct birds, and samples of spores and pollen dating back to the time after the explosion.
After analyzing the structure of more than 10 thousand species of modern birds, scientists have come to the conclusion that their ancestors were land birds.
"The analysis showed that the closest ancestors of all living birds were most likely terrestrial," says Field.
The second argument in support of the hypothesis of the disappearance of the forest - from 70 to 90 percent of all spores found in the sediments of the first thousand years after the explosion come from only two species of paportonica.
“These ferns represent evidence of a 'plant catastrophe' where new species rapidly colonize open spaces, as occurs today with fern overgrowth in lava flows in Hawaii or mudslides following volcanic eruptions,” the authors of the work believe.