[Extinction]Geochemical Study Links Earth’s Worst Mass Extinction To Volcanism

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  The early ancestors of modern mammals were among the victims of the mass extinction at the end of … [+] the Permian when an estimated 96% of all species became extinct.

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  The most severe mass extinction event in the past 540 million years eliminated more than 90 percent of Earth’s marine species and 75 percent of terrestrial species. Although scientists had previously hypothesized that the end-Permian mass extinction, which took place 251 million years ago, was triggered by voluminous volcanic eruptions in a region of what is now Siberia, they were not able to explain the mechanism by which the eruptions resulted in the extinction of so many different species, both in the oceans and on land.

  Associate professor Laura Wasylenki of Northern Arizona University’s School of Earth and Sustainability and Department of Chemistry and Biochemistry is co-author on a new paper in Nature Communications entitled, “Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction,” in collaboration with Chinese, Canadian and Swiss scientists. The paper presents the results of nickel isotope analyses performed in Wasylenki’s lab on Late Permian sedimentary rocks collected in Arctic Canada.

  The samples have a nickel isotope ratio not found in sedimentary rocks, and the only plausible explanation is that the nickel comes from a volcanic source, very likely carried by aerosol particles and deposited in the ocean, where it dramatically changed the chemistry of seawater and severely disrupted the marine ecosystem.

  ”The study results provide strong evidence that nickel-rich particles were aerosolized and dispersed widely, both through the atmosphere and into the ocean,” Wasylenki said in the study’s announcement published by Northern Arizona University.

  According to the study, flood-basalt eruptions, like the one that formed the Siberian Traps, last several millennia and release large quantities of nickel-rich ash into Earth’s atmosphere. Atmospheric currents will distribute the ash all over the planet, poisoning the land and the sea, as the discovery of the nickel-rich sediments in Canada show.

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  Nickel is an essential trace metal for many organisms, but an increase in nickel abundance would have driven an unusual surge in productivity of methanogens, microorganisms that produce methane gas. An increased methane level would have been tremendously harmful to all oxygen-dependent life, causing extreme warming and – as gases are washed by rain into the sea – acidification of the oceans. In a warmer world, extreme droughts and widespread deoxygenation and sulfide poisoning of the oceans will cause an environmental collapse, wiping out a wide variety of animal and plant groups, the study concludes.

  Geologists also noted a periodicity in such catastrophic events, happening every 25 to 30 million years, as they could result from long-term volcanism linked to magma plumes rising up in Earth’s mantle.

  Flood-basalts(red areas) and corresponding hotspots (yellow dots). Hotspots are stationary regions … [+] of increased igneous activity; the spatial discrepancy of these spots and lava deposits is explained by the slow movement of the tectonic plates. The radiometric ages of some of the igneous provinces correlate with major mass extinction events during Earth’s history, as shown by the number of families recognized in the geological record.

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  ”Our data provide a direct link between global dispersion of nickel-rich aerosols, ocean chemistry changes and the mass extinction event,” Wasylenki said. “The data also demonstrate that environmental degradation likely began well before the extinction event—perhaps starting as early as 300,000 years before then. Prior to this study, the connection between Siberian Traps flood basalt volcanism, marine anoxia and mass extinction was rather vague, but now we have evidence of a specific kill mechanism. This finding demonstrates the power of nickel isotope analyses, which are relatively new, to solve long-standing problems in the geosciences.”

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