The worst ecological disaster in the natural history of the Earth — the Permian extinction-was caused by massive volcanic eruptions in Siberia. This was finally proved by Chinese scientists from the University of Science and Technology together with colleagues from Canada, the United States, and Switzerland. Researchers have explained for the first time how atmospheric pollution from volcanic aerosols could lead to the extinction of most species of living organisms on land and oceans. The scientists ‘ article is published in the journal Nature Communications.
The Permian extinction occurred 251 million years ago at the boundary of the Permian and Triassic periods. About 90 percent of marine species and 75 percent of terrestrial species have disappeared from the face of the Earth. It is believed that the fault lies with trap magmatism in Siberia when a huge volume of magma is poured onto the surface and a large number of aerosols are released. To determine the nature of the aerosol particles, the scientists analyzed the isotopic composition of Permian-Triassic sedimentary rocks in the Arctic part of Canada.
The researchers found that the deviation of the Ni60/Ni58 isotope signature in the test samples from the signature of the standard sample ranges from minus 1.09 to 0.25 ppm (or a tenth of a percent). The deviation of the isotopic signature of nickel, denoted as δ60Ni, is defined as the ratio of Ni60/Ni58 found in Permian sedimentary rocks to the commonly occurring ratio of nickel-60 to nickel-58 (in the formula, the ratio is still subtracted from one, which explains the “minus” sign for an excess of light isotopes).
The cause of a specific isotope signature can be different sources, characterized by their own isotope ratio. For example, it can be products of weathering of the continental crust, carried by rivers to the oceans, volcanic aerosols deposited in the oceans from the atmosphere, or hydrothermal activity. For example, the average deviation of the isotope signature for rivers is 0.84 ppm, that is, there is an excess amount of nickel-60 isotopes in the river water relative to nickel-58 (this is due to the sorption of light nickel isotopes on iron oxides). In seawater, the excess of nickel-60 increases even more (1.44 ppm). The physical and chemical conditions of different environments change the isotope signature, which allows us to determine exactly how the rocks were formed.
δ60Ni of Permian-Triassic rocks are characterized by the presence of an excessive amount of light isotopes. A similar deviation in the formation or melting of magmatic sulfides is observed at high temperatures. As scientists write, trap magmatism in Siberia melted sulfide nickel ores, and the resulting aerosols fell out, including over the Arctic part of Canada. This happened 500 thousand years before the mass extinction, but large-scale nickel emissions should have already led to environmental violations.
The increase in nickel concentration over the millennia must have been accompanied by the rapid activity of microorganisms in the ocean, which eventually led to the depletion of oxygen in the seas and the formation of giant dead zones. The extinction was accelerated by the peak of volcanic magmatism, which led to the release of carbon dioxide and methane and, as a result, to drastic climate change and almost complete oxygen depletion of the ocean. This caused the mass extinction of marine species.