Geologists have suggested that Earth’s most severe mass-extinction was caused by a huge pulse of magma which released deadly levels of greenhouse gases into the atmosphere.
Read more: Earth has entered into a sixth mass extinction event
In a Nature Communications paper entitled “Initial Pulse of Siberian Traps Sills as the Trigger of the End-Permian Mass Extinction,” the team suggests that a huge magma pulse wiped out 95 per cent of marine species and 70 per cent of land species 252 million years ago.
The end of the Permian period coincided with an abrupt change from dominantly flood lavas to sill intrusions, a type of intrusive igneous rock (rock that has solidified from lava or magma).
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In a region known as the “Siberian Traps”, a huge pulse of magma rose up through the Earth, and instead of erupting on the surface, it spread throughout the Earth’s crust, creating a vast network of rock stretching across almost one million square miles.
The magma then solidified between older layers of sedimentary rock into geological formations known as ‘sills’.
Extreme heat from these sills led to ‘contact metamorphism’ (alteration of the composition or structure of a rock by heat or pressure) of carbon-rich rocks.
This released dangerous levels of carbon dioxide, methane and sulphur dioxide into the environment and triggered the end of the Permian period.
Michael Benton, the Professor of Vertebrate Palaeontology at the University of Bristol, says: “This paper is important in matching the phase of volcanic eruption to peak extinction.
“The Siberian Traps were erupting for a million years or more, and yet the bulk of the extinction happened in 50,000 years or less. It coincides with an episode of sill formation, when horizontal sheets of magma were being emplaced in the rocks around the eruption site. The key is that this coincide with the maximum level of carbon dioxide production, which led to extreme global warming and extinction.”
Mass-extinctions are usually blamed on volcanic eruptions, but this report studied the timings and found that lava eruptions on the Earth’s surface happened too early to be the cause.
Seth Burgess, a geologist at the US Geological Survey, Samuel Bowring, the Robert R Shock professor of geology at the Massachusetts Institute of Technology and James Muirhead, a research associate in the department of Earth sciences, studied the Russian Siberian Traps, a large igneous province (LIP) which spanned 500,00 square miles, for their report.
Made up of an extremely large accumulation of igneous rocks, this was the site of nearly a million years of epic volcanic activity.
“Heating of sediments over the large area encompassed by the sill complex… likely liberated massive volumes of greenhouse gasses,” the paper reads. “The model presented here suggests that LIPs (large igneous province) characterised by a pulse of widespread sill emplacement into a volatile-fertile basin are lethal on a global scale.”
Sills in Siberia’s Tunguska Basin likely pushed their way through limestone, coal, and clastic rocks.
This paper gives an insight into millennia-old conditions which have impacted our environment today. During the end-Permian, the biosphere couldn’t protect itself against the sudden, large emission of greenhouse gases, leading to a continual elevation in sea surface temperature across the globe.
