201 million years ago, Earth experienced a severe mass extinction. The fossil records tell us that around three quarters of living species suddenly disappeared. This major event in terrestrial history is thus used to mark the end of the Triassic and the entry into a new geological period: the JurassicJurassic.
Among the survivors of this biological crisis are the dinosaursdinosaurs. They will also take advantage of the vacancy of numerous ecological niches to diversify and begin a reign which will last 160 million years.
The triggering of intense volcanic activity involved
The analysis of stratastrata sedimentary dating from this period reveals that the Triassic-Jurassic extinction coincides with the outbreak ofvolcanic eruptionsvolcanic eruptions massive. THE supercontinentsupercontinent PangeaPangea is indeed entering a phase of fragmentation. There continental crustcontinental crust stretches and refines, creating a gap ofcollapsecollapse which will later open up to give birth to the South Atlantic Ocean. THE magmamagma which rises along this zone of fragility will thus give rise to an immense magmatic province extending over 11 million km2 ! For 600,000 years, eruptions continued. It is estimated between 2 and 6 million km3 the volumevolume of is madeis made issued during this period.
However, such volcanic activity is not without consequences on the climateclimate terrestrial. The enormous quantities of CO2 issued by the volcanoesvolcanoes reinforce thegreenhousegreenhousecausing the average temperature of the globe to rise. The main cause of the Triassic-Jurassic extinction has long been attributed to a global warmingglobal warming drama leading to an imbalance in the oceans. And yet, a new study published in the journal Pnas suggests that this would not be the heatheatbut the cold which would have got the better of many species.
A terrible volcanic winter would have preceded slow global warming
Scientists have in fact discovered that the first pulses of magmatic activity would have been much briefer. Instead of spanning several hundred thousand years, they would have only lasted a few decades! Their impact would therefore have been concentrated over a much shorter time, and that changes everything. Because in addition to releasing CO2the eruptions inject sulfate compounds into theatmosphereatmosphere. However, if the increase in the CO rate2 causes a greenhouse effect in the long term, the presence of large quantities ofaerosolsaerosols sulfates in the atmosphere will have an immediate, and inverse, effect on the climate.
By blocking the penetration of solar rays, they will cause the temperature to drop, creating what is called a volcanic wintervolcanic winter. If the effect does not last long, the extremely brutal climate change thus induced can be very devastating for terrestrial life. For researchers, it would therefore be this short phase of falling temperatures which would be mainly responsible for the biological crisis, and not the warming which followed. There wildlifewildlife and flora adapted to a tropical climatetropical climate would indeed have had a hard time supporting this brutal cooling, with the exception of the dinosaurs!
The latter, which only appeared a few tens of millions of years ago, were mostly small and probably equipped with feathers. Characteristics that would have allowed them to better withstand the cold, just like the small mammals already present.
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