(ORDO NEWS) — Four of the five mass extinctions of the past coincide with sharp bursts of volcanic activity. They threw out so much carbon dioxide and lava that they could quickly destroy all life on entire continents.
A group of scientists from Germany and the United States studied the geological and paleobiological traces of the most powerful volcanic eruptions of the distant past and came to the conclusion that their connection with the largest extinctions is beyond chance.
Apparently, it was these eruptions that “restarted” the Earth’s biosphere at least four times, including destroying the dinosaurs 66 million years ago.
The study covered five major Phanerozoic extinctions that began 539 million years ago and continue to this day.
These are the Ordovician-Syllurian extinction 440 million years ago (minus 85% of marine species), the Devonian extinction 364 million years ago (minus half of the genera of all living creatures), the Permian extinction 251 million years ago (minus 96% of marine species, 73% of terrestrial species).
Vertebrates and 83% of insect species), the Triassic extinction about 200 million years ago (minus half of all living species) and the Cretaceous-Paleogene extinction 66 million years ago (minus 47% of marine animal genera and 18% of land vertebrate families, including non-avian dinosaurs).
It turned out that at least four out of five extinctions occurred simultaneously with basalt floods. These are powerful volcanic eruptions that eject millions of cubic kilometers of basaltic magma.
In just a million years (by geological standards, this is very fast), such eruptions can cover an entire continent with a thick layer of lava. Now traces of basalt floods are visible as vast areas of stepped volcanic rock. They were also studied by experts from Germany and the USA.
Another “damaging factor” of such large-scale eruptions is the release of huge volumes of carbon dioxide and sulfur dioxide. For example, during the Triassic extinction period, volcanoes added about 100 trillion tons of CO2 to the atmosphere, which caused global climate change.
And a series of powerful eruptions in Siberia 252 million years ago literally smothered most living creatures on the planet with carbon dioxide, including insects. Now the basalt traces of those eruptions (Siberian traps) cover an area of two million square kilometers and form the famous Putorana Plateau .
Mass eruptions also occurred on the Indian subcontinent shortly before the extinction of the dinosaurs, but then the fall of the Chicxulub meteorite “confused all the cards.”
According to Brenhin Keller, one of the authors of the study, after the discovery of the Chicxulub crater, scientists swept aside all other hypotheses of the extinction of dinosaurs.
But with other extinctions, it was not possible to connect any falls of celestial bodies to Earth. This may indicate that the Chicxulub impact event was a coincidence that only accelerated the Cretaceous–Paleogene extinction event, but was not its main cause.
The researchers tested this hypothesis with numerical models. They generated 100 million patterns of climate and biosphere change, and then correlated them with extinction scenarios involving volcanoes and asteroids.
The result showed that the connection between extinctions and eruptions is clearly not accidental, while the connection with meteorite falls turned out to be much weaker and abruptly disappeared when the Chicxulub fall was removed from the model.
Moreover, the main factor that made the eruptions so deadly was the enormous rate of release of lava and CO2, which the ecosystems could not “digest”.
According to Brenhin Keller, this result does not allow ignoring the role of volcanism in mass extinctions – it seems that it was decisive.
All the conditions for the death of dinosaurs, according to scientists, were already formed as a result of eruptions in the Hindustan region, but the Chicxulub fall was only a “death knell” for the dinosaurs of the Jurassic period.
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