Coal-Burning Contributed to End-Permian Mass Extinction
An international team of geologists has found the first direct evidence that volcanic eruptions in the southern part of the Siberian Traps region 252 million years ago burned large volumes of coal and vegetation.
The end-Permian extinction, also known as the Permian-Triassic extinction event and the Great Dying, is the Earth’s most severe mass extinction that peaked about 252.3 million years ago.
The catastrophe killed off nearly 96% of all marine species and 70% of terrestrial vertebrate species on the planet over the course of thousands of years.
Calculations of sea water temperature indicate that at the peak of the extinction, the Earth underwent hot global warming, in which equatorial ocean temperatures exceeded 40 degrees Celsius (104 degrees Fahrenheit).
Among the possible causes of this event, and one of the most long-hypothesized, is that massive burning coal led to catastrophic global warming, which in turn was devastating to life.
To search for evidence to support this hypothesis, Arizona State University’s Professor Lindy Elkins-Tanton and colleagues looked at the Siberian Traps region, where it was known that the magmas and lavas from volcanic events burned a combination of vegetation and coal.
They focused on the volcaniclastic rocks — rocks created by explosive volcanic eruptions — and collected over 500 kg of samples.
“We found towering river cliffs of nothing but volcaniclastics, lining the river for hundreds of miles. It was geologically astounding,” Professor Elkins-Tanton said.
As the samples were analyzed, the authors began seeing strange fragments in the volcaniclastics that seemed like burnt wood, and in some cases, burnt coal.
Further field work turned up even more sites with charcoal, coal, and even some sticky organic-rich blobs in the rocks.
“Our study shows that Siberian Traps magmas intruded into and incorporated coal and organic material,” Professor Elkins-Tanton said.
“That gives us direct evidence that the magmas also combusted large quantities of coal and organic matter during eruption.”
And the changes at the end-Permian extinction bear remarkable parallels to what is happening on Earth today, including burning hydrocarbons and coal, acid rain from sulfur, and even ozone-destroying halocarbons.
“Seeing these similarities gives us extra impetus to take action now, and also to further understand how the Earth responds to changes like these in the longer term,” Professor Elkins-Tanton added.
The findings were published in the journal Geology.
L.T. Elkins-Tanton et al. Field evidence for coal combustion links the 252 Ma Siberian Traps with global carbon disruption. Geology, published online June 12, 2020; doi: 10.1130/G47365.1