Tuesday, August 16

Two years of darkness and soot that complicated photosynthesis: this is how these scientists describe the apocalypse of the dinosaurs

The decline of the dinosaurs resembled the title of that collection of poems by Celso Emilio Ferreiro: a “long night of stone”. Although scientists have known for decades that the darkness that followed the meteorite that struck Earth 66 million years ago played a key role in the extinction of the dinosaurs, it has been in recent times that – thanks to the use of models – they have been able to get a rough idea of ​​how long it lasted and how dark the gloom was. Research presented at the American Geophysical Union (AGU) Annual Meeting, held in New Orleans, yields accurate data and a surprising conclusion: the darkness caused by the asteroid. it could have persisted for two years.

Following the impact of the asteroid, about 12 kilometers in diameter, clouds of pulverized rock and sulfuric acid darkened the skies and triggered a drop in temperatures, acid rain and forest fires. Stage –remember Live Science– it has been known for more than three decades; but the key is … How did it affect life on Earth?

As Peter Roopnarine of the California Academy of Sciences and a participant in the AGU annual summit details to Live Science, one of the keys is in the fires that followed the asteroid, which generated soot that was suspended in the upper atmosphere. Its quantity was abundant enough to reduce the sunlight that reached the Earth and thus complicate photosynthesis, key to life. “The concentration during the first days or weeks of the fires would have been high enough to reduce the amount of incoming sunlight to a low enough level to prevent photosynthesis,” the expert abounds.

Hell Creek, the “testing ground”

How long did that gloom last? Roopnaire and his team modeled 300 species of Hell Creek, a geological formation rich in fossils from the last part of the Cretaceous located in the USA and especially well documented. So much, in fact, that researchers “They reliably rebuilt the paleocommunity” and they developed various scenarios to calculate how they affected periods of darkness between 100 and 700 days – more or less, the equivalent of three months and two years. Their goal: to determine which interval corresponded to a 73% vertebrate extinction rate, which is the one that is conserved in the fossil record. The study started from the assumption that the darkness was generated quickly and had spread in just a few weeks.

The conclusions of the study are revealing. When the twilight lasted “only” 150 days, the ecosystems seemed to recover, but things change more or less after 200 days. Overcome that critical point, reseña Live Science, “Some species became extinct and dominance patterns changed.” If the simulation lasted until 650 or 700 days of darkness, the extinction rate was already hovering around a range between 65 and 81%, which would show that the Hell Creek communities faced about two years of darkness.

“Conditions varied around the world due to atmospheric flow and temperature variation, but we estimate that darkness could have persisted in the Hell Creek area for up to two years”, Clarifies Roopnarine. Once the tipping point has been reached, ecosystems can recover with a new balance of species that requires decades. The same study concludes, for example, that once the darkness dissipated, the ecosystem took four decades to begin to recover.

Via | Live Science


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