Scientists have found chemical traces in Siberia that the Perm extinction, the largest disaster in Earth's history, was caused by the destruction of the ozone layer and the sterilization of all flora. Their findings were presented in the journal Nature Geoscience.
“We showed that the Siberian lithosphere at that time contained huge deposits of halogens - chlorine, bromine and iodine. All of these gases were released into the atmosphere during volcanic explosions, which virtually destroyed the ozone layer and triggered the mass extinction,”said Michael Broadley of the University of Manchester (UK).
Volcanic end of the world
Scientists have identified the five largest mass extinctions of species in the history of life on Earth. The most significant is considered the "great" Permian extinction, when more than 95% of all living beings inhabiting the planet disappeared, including bizarre beast-lizards, close relatives of mammalian ancestors, and a number of marine animals.
There is evidence that large quantities of carbon dioxide and methane were released into the atmosphere and oceans during this time, dramatically changing the climate and making the Earth extremely hot and arid. As the studies of Russian geologists show, these emissions came to the surface of the planet in Eastern Siberia, in the vicinity of the Putorana plateau and modern Norilsk, where the most powerful outpourings of magma took place about 252 million years ago.
The main mystery of the Permian extinction, as Broadley explains, today remains how exactly these volcanic ejections were associated with the disappearance of almost all flora and fauna. So far, there is no consensus among scientists on this matter.
For example, some of them believe that the extinction was caused directly by volcanic emissions. Others believe that it was triggered by environmental changes, and still others attribute this role to nickel, which got into the water of the seas and caused a violent bloom of algae.
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Scientists have recently formulated a simpler theory to explain the severity of this extinction by experimenting on dwarf pines. They found that the disappearance of the ozone layer, provoked by volcanic emissions, should have completely sterilized the entire flora of the Earth and deprived animals of their food base for several centuries.
Gas attack
Broadley and his colleagues obtained the first confirmation of this theory by studying samples of the Earth's ancient crust, "stuck" in the ejections of the mantle, found in the Yakut diamond mines Udachnaya and Naked. They were built on the territory of kimberlite pipes, through which lava flows from the depths of the mantle rose to the surface of the planet about 360 and 160 million years ago, long before and after the Perm catastrophe.
Scientists were interested in what volatiles were present in these rock samples. Serious differences in their shares will indicate which gases "escaped" from the deep layers of the Earth during the outpouring of magma and how they could affect the life of flora and fauna and the climate of the planet.
As it turned out, the rock samples from Udachnaya contained much more atoms and molecules of three important elements - chlorine, bromine and iodine. These gases are not only toxic to humans and animals, but also act today as the main component of the "harmful" types of freons that destroy the ozone layer of the Earth.
The source of these halogens, as scientists assume, were ancient rocks of the seabed of the Earth, which plunged into the depths of the mantle in the distant past, and "floated" in the vicinity of the Putorana plateau at the end of the Permian period.
The explosions of supervolcanoes, as shown by calculations by Broadley and his colleagues, "catapulted" into the upper layers of the Earth's atmosphere about 8.7 trillion tons of chlorine, 23 billion tons of bromine and 96 million tons of iodine. Such a quantity of halogens, according to geologists, was more than enough to completely destroy the ozone layer and deprive the planet of protection from ultraviolet radiation for many hundreds of years.
Such a scenario of the Perm catastrophe suggests that this cataclysm was not an isolated, unique event. It may well be repeated in the future, if the former rocks of the sea crust, containing large amounts of halogens and other volatile substances, “float up” to the surface of the Earth, the authors of the article conclude.