Siberian traps. Image: jxandreani
Twenty-five million years ago, life on Earth was shattered by the Permian-Triassic event, the most devastating loss of biodiversity in the history of our planet. Over a period of only 60,000 years, about 90 percent of the marine animals and 70 percent of the land species died, which owes its macabre nickname "The Great Dying" to this event. Not even Avengers & villain Thanos ventured to dream of such a devastating biological reset button.
Scientists have long considered what made the Great Dying so much harder than other deaths. This mystery is explored through a new lens published on Monday in Nature Geoscience under the direction of Michael Broadley, a postdoc at the Center for Petrographic and Geochemical Research in Vandœuvre-lès-Nancy.
The relentless volcanic activity that formed the Siberian Traps, a region of basaltic rock that stretches over 7 million square kilometers in northern Russia, was previously established as the main driving force of the Great Dying. But Broadley's team confirmed this link by presenting the first detailed estimates of halogen abundance in the lithosphere, the outer crust, before and after the mass extinction.
Lithosphärenprobe. Image: Michael W. Broadley
Halogens are a family of elements that contain fluorine, chlorine, bromine, iodine and astatine. Some halogens are naturally toxic and some become particularly deadly when combined with other molecules. Broadley and his colleagues studied two specimens from the Siberian Traps that occurred about 100 million years ago and 100 million years after the Great Dying. Sampling indicated that the Siberian lithosphere had been rich in halogens before extinction and was exhausted after completion.
In other words, the tremendous death was possibly particularly severe because the volcanic feathers released into the atmosphere were heavily dosed with toxic halogens. Not only could these chemicals drive global climate change, they could also deplete the ozone layer and expose life on Earth to dangerous cosmic rays and sunbeams.
Read More: Mathematical formula predicts global mass extinction in 2100  "The onset of halogens in the stratosphere catalyzes ozone-depleting reactions and increases the surface temperature of biologically damaging UV radiation," the authors write. This could have triggered a chain reaction that "could potentially have released large amounts of halogens and other volatiles into the atmosphere, contributing to species extinction and extinction during the final perm crisis".
These halogen-rich clouds were just one of many influential factors that determined the ferocity of the Great Dying, but they are a crucial piece of the puzzle. As humans try to mitigate the global impact of our own industrial activity, it is useful to remember that without the help of us, the earth can be a cruel lover.
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