Difficult to lie: the enigma of the disappearance of the dinosaurs, 66 million years ago, lives all budding paleontologist, much more than the necessary thirst to discover new fossils – like this giant pterosaur ten meters wingspan for the first time described by Canadian paleontologists. However, thanks to the work of geologist Paul Renne, who put an end to the controversy between "volcanic" and "meteorite" on the great extinction of the Cretaceous, it is the fall in the current Gulf of Mexico of a meteorite at least 10 kilometers in diameter which is the cause. But what happened to the seconds, minutes or hours after the impact? And what was the chronology of this catastrophe with devastating consequences? Published Monday in the prestigious scientific journal PNAS, a study of Texan geologists and other scientists traces in an unprecedented way this last day of the dinosaurs, which we consider especially as the first day of our geological era, the Cenozoic.

To draw the scenario of this dark day, responsible for the extinction of 75% of life on Earth, the researchers have indeed mounted in 2016 an expedition – which also gave rise to a documentary broadcast on France 5 last week – in order to drill several hundred meters underwater the crater of Chicxulub, off the Yucatan Peninsula. The idea was that by analyzing the composition of the cores extracted from the impact zone, it was possible to obtain a whole bunch of geological information that would make it possible to reconstruct the cataclysmic event. What we know very well because the formation of craters, well studied, follows well-defined physical laws.

This gives the following conclusions: in the seconds and minutes following the fall of the meteorite, whose impact with the earth's crust released an energy equivalent to 10 billion bombs A (that of Hiroshima), molten rocks have formed a ring 40 meters high. This shock was accompanied by several thousand kilometers of giant barbecue that burned the unfortunate dinosaurs that were there. Almost instantly. At the other end of the world, friction fires caused by molten rocks ejected into the atmosphere have been the cause of the living beings the following hours. Not to mention mega tsunamis in all the oceans or acid rain harmful to the marine fauna and flora. The absence of evaporites, sulphide-rich rocks, in the heart of the crater suggests that these rocks have vaporized, releasing 325 gigatonnes of sulphide into the atmosphere, sufficient to ward off the sun's rays. This night long of several years then caused a cooling of the terrestrial temperatures and a collapse of the food chain fatal to the rare survivors (there were in Patagonia) of this apocalypse.

Florian Bardou

(tagsToTranslate) Meteorite (t) Cretaceous-Tertiary Extinction (t) Crater d

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