Deadly Mass Extinctions Need Not Happen Immediately
Studies looking into the how and why of the Permian–Triassic extinction event – also known as ‘The Great Dying” – have come thick and fast recently, and a new study has again shifted our thinking on just how long the extinction event took to wipe out so much of our planet’s life.
Published earlier this month in the journal Geological Society of American Bulletin, the study, led by Thomas Algeo of the University of Cincinnati, depicts a high-resolution look at the geology of the Permian-Triassic boundary section on Ellesmere Island in the Canadian Arctic.
What they found suggests that instead of an abrupt kill-off that saw 96 percent of marine species and 70% of terrestrial animals wiped from the face of the Earth, the mass-extinctions took place in stages over hundreds of thousands of years.
Their research depicts a world that is entirely barren of vegetation, scarred by erosion from showers of acid rain, huge dead-zones throughout the oceans, and runaway greenhouse warming leading to increased temperatures. And their research points to massive volcanism in Siberia as one factor for the cause of this die-off.
Planetsave has addressed the Great Dying several times in the past year, check out past news below:
Biggest Extinction Event Caused by Volcanoes
CO2 Increase Linked to World’s Largest Extinction
Permian Extinction Disastrous for Land-based Animals
Were Siberian Volcanoes Responsible for Permian Extinction Event?
“The scientists relate this extinction to Siberian Traps volcanic eruptions, which likely first affected boreal life through toxic gas and ashes,” said H. Richard Lane, program director in the National Science Foundation’s (NSF) Division of Earth Sciences, which funded the research.
“The eruption released lots of methane when it burned through the coal,” Algeo said. “Methane is 30 times more effective as a greenhouse gas than carbon dioxide.
“We’re not sure how long the greenhouse effect lasted, but it seems to have been tens or hundreds of thousands of years.”
Unsurprisingly, much of the evidence of the Permian–Triassic extinction event is not where it once was, with much of it having washed into the oceans. That is why Algeo and his colleagues look for it among fossilised marine deposits. However this has been the cause for what appears to be a misinterpretation of what actually took place.
Previous investigations have looked at deposits created the ancient ocean Tethys, specifically those deposits now found in South China. These deposits record a sudden extinction at the end of the Permian.
“In shallow marine deposits, the latest Permian mass extinction was generally abrupt,” Algeo said. “Based on such observations, it has been widely inferred that the extinction was a globally synchronous event.”
Recent studies, such as Algeo’s, are beginning to shift that view around.
Bu studying rock layers at West Blind Fjord on Ellesmere Island in the Canadian Arctic, a location that – at the end of the Permian – would have been much closer to the Siberian volcanoes than sites in South China – the researchers found a total die-off of siliceous sponges approximately 100,000 years earlier than the marine mass extinction event recorded at Tethyan sites (such as those in South China).
According to Algeo and his colleagues, who looked at how the type of rock changed from the bottom to the top in the sedimentary rock layers from Ellesmere Island, what appears to have happened is that the effects of early Siberian volcano activity were confined to the northern latitudes of the planet. Such effects included toxic gases and ash, which only after some time did they reach south enough to affect the Tethys Ocean.
Source: National Science Foundation