THE “culprit” is the meteorite. The major suspects for the fifth mass extinction that wiped out the dinosaurs, along with via three-quarters of the life forms on Earth, has always been two. And even if the more suspicious, for several years, hang on the spectacular impact of a bolide that struck the Earth 66 million years ago, another hypothesis, less popular, gives an exceptional volcanic activity, and the event known as the extinction of the Cretaceous-Paleocene. A new study, published in Science by a large group of scientists, puts, if not a gravestone, an important seal on the first and most well-known theory.
volcanoes are not enough
let’s go Back to 66 million years ago, on Earth, a volcanic activity is very intense, covering the Indian subcontinent, and the lava model, the geological formations known as “Trappi of the Deccan”. An upheaval so intense to trigger climate change on a global scale. And so it happens, but not with such intensity as to cause a mass extinction. The proof is, as always, in the fossil record and in the analysis of the geological layers that date back to that period, the pages of a book that tell almost everything of this story. The volcanic eruptions, in addition to spew into the atmosphere clouds of black soot, they usually also release large amounts of carbon dioxide, a gas, and we realise in these years, which causes the greenhouse effect traps solar radiation and then heats the atmosphere.
the purpose of The study was therefore to determine when it took place, the phenomena that are more intense to try or rule out a connection with the death of the living species. The survey conducted by Pincelli Hull , geologist, department of Geology and geophysics at Yale university, has analysed the carbon isotopes contained in fossil marine kept us up, drilling the bottom of the Atlantic ocean, not far away from where the wreck of the Titanic. And he has compared the different models of the temperature. The result is that the effects of the eruptions were much earlier: “the volcanic activity of The late Cretaceous caused a global warming gradually to about two degrees,” explains Michael Henehan , a former researcher at Yale and one of the first signatures of research – but not a mass extinction. Several species moved to the north Pole and the south, but turned back well before the impact with the asteroid”. The all happened about 200,000 years before the extinction, the temperatures were too low because they were the volcanoes responsible.
it Remains, therefore, only the meteorite, caught with the “smoking gun”, the one that was on the scene of the crime at the time of the disaster. And this is not a speculation. Recently some paleontologists and geologists have discovered the “Pompeii of the dinosaurs, the carcasses fossils of those that may have been the first victims of the impact, swept away by the tsunami and rain of fire. And the crater of Chicxulub now identified and probed. Even if the researchers are convinced that it is still early to put the word end to the debate within the scientific environment.
The volcanism in India, however, continued even after the impact. This also suggests that the eruptions were not associated with a large emission of CO2 or that the sea has contributed to absorb a large part, acidificandosi. The other great impact that they may have had regarding the recovery and proliferation of life after the dinosaurs. A phenomenon that they admit the same researchers, it has not yet been thoroughly investigated. But it came to pass quickly, as evidenced by other studies, and that finally led to the great expansion of the mammals. And finally, in the last short paragraph of the story, to the appearance of the man.
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