Ozone-depleting chemicals may have caused the largest mass extinction in history



Living organisms have not always had it easy and during their many billions of years of history they have often had it was threatened with destruction. But there was no greater challenge than the Great Dying, an event of mass extinction that took place 250 million years ago. For almost a million years, a huge volcano in Siberia continuously erupted, 90% of all types of sweep away. The scale of extinction was unprecedented, but it was never clear what made this enormous volcanic eruption so deadly – after all, it was not the first or the last event of its kind. Now a new study explains what may have driven the Grote Dying: reactive chemicals released from stocks under the crust that destroyed the ozone layer.

The Permian-Triassic extinction took place at the end of the Perm period, and at that time life on our planet was hellish: global warming, acidification of the ocean and ocean anoxia (lack of oxygen) all worked together to eradicate most of life Earth. According to a 2014 study conducted by MIT researchers, the extinction event probably lasted 60,000 years, with an uncertainty of 48,000 years. In geological terms, this is like blinking an eye – too fast for most life on earth to adapt. The samples also confirmed what was known for a while: the extinction was preceded by a strong increase in carbon dioxide in the oceans.

The protracted volcanic eruptions of the Siberian traps, a region in Russia, whose stepped hills are the result of repeated eruptions of magma, release volatile chemicals, including carbon dioxide, into the atmosphere and the oceans and cover an estimated five million cubic kilometers. Most of the carbon was absorbed by the oceans that function as huge heat drains, with sea temperatures rising by as much as 10 degrees Celsius – too warm for everything to survive. Approximately 96% of the marine species and 70% of the terrestrial species were destroyed by the extinction of the Permian Triassic and it took ten million years on earth to recover from this event.

But the conditions under which life had to set in these difficult times were perhaps even more challenging rather than a hypothesisd.

In a new study published in Nature Geoscience, Michael Broadley, a postdoctoral researcher at the Center for Petrographic and Geochemical Research in Vandoeuvre-lès-Nancy, France, together with colleagues, studied rocks of the lithosphere – the solid outer part of the Earth sandwiched between the crust and the cloak – which were caught by passing magma during the old eruption.

These examples provide a snapshot of the composition of the lithosphere prior to the event that brought them to the surface of the earth. Before the eruption of the Siberian Flood Basalts, the researchers discovered that the lithosphere contained significant amounts of chlorine, bromine and iodine. These elements, present in the halogen group on the periodic table, have since disappeared after the volcanic eruption.

The breakthrough was to identify these elements that were presented in extremely low concentrations – only a few parts per billion in the case of bromine and iodine.

"These rocks were a complete surprise, the level of halogens was much higher than we expected, and when we got these results we realized that we had something interesting: the level of enrichment is so high that we knew that even if only a small percentage would be released into the atmosphere, which could potentially have devastating effects on the Earth's ozone layer, "Broadley told ZME Science.

As soon as these elements flooded the atmosphere, they reacted with the ozone layer and destroyed it. The ozone layer dampens the surface of the planet against harmful UV radiation and exposure to higher levels of UV radiation (such as those associated with a diluted ozone layer) significantly increases the risk of developing cataract and skin cancer. Large-scale exposure to UV levels expected in the absence of the ozone layer would have drastic consequences for entire ecosystems.

Human activity has recently made a huge gaping hole in the ozone layer due to pollution with chlorofluorocarbons and chlorofluorocarbons (CHC & # 39; s and HCHC & # 39; s), chemicals used in old refrigerators and aerosols. Thanks to a remarkable international cooperation, that gap is now almost hidden. Unfortunately, those who lived more than 250 million years were not so lucky.

In combination with acid rain and gloomy sky, a thin layer of ozone at that time must have been a pretty dramatic picture of the planet.

"We knew from fossil evidence that there is a high level of mutated traces and pollen around the time of the eruption of the halogens.This high degree of mutation is considered to be related to higher levels of UV radiation at that time. Therefore, considering that the enormous amounts of halogens released from the lithosphere have led to the destruction of the ozone layer, high levels of UV radiation from the sun have reached the surface, and although not immediately noticeable, the high UV levels would DNA has been damaged and has led to sterility in the plant, so if people were nearby, they might have witnessed large-scale deforestation and the collapse of the food chain, "Broadley said.

In the future, Broadley and colleagues intend to study diamonds from the lithosphere. During their formation, the diamonds capture a number of lithospheric liquids, which can help to answer how the Siberian lithosphere was primarily enriched with halogens. In the meantime, the research serves as a grim reminder of how fragile life can be.

"This study has parallels with modern times." During the 1970s and 1980s, scientists discovered the ozone hole caused by the release of halogen containing compounds to the atmosphere, but fortunately global measures were taken to reduce the emissions of these substances, but our study demonstrates the importance of the ozone layer and the potential consequences that may result from its destruction, "Broadley said.

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