London: Toxic coal ash produced as a result of massive volcanic eruptions may have led to the largest extinction event in Earth`s history, according to Canadian researchers.
The Permian extinction is believed to have occurred about 250 million years ago — back even before dinosaurs roamed the planet — and wiped out 95 percent of life in the sea and 75 percent of life on land.
Researchers at the University of Calgary have now discovered evidence suggesting massive volcanic eruptions at the time burnt significant volumes of coal, producing ash clouds that had broad impact on global oceans.
“This could literally be the smoking gun that explains the latest Permian extinction,” said Steve Grasby, a research scientist at Natural Resources Canada (NRC) and adjunct professor in the University of Calgary`s Geoscience department.
Unlike the extinction of the dinosaurs - which happened 65 million years ago and widely believed to have been caused, at least in part, by the impact of a meteorite – it was unclear what caused the Permian extinction.
Previous researches have suggested massive volcanic eruptions through coal beds in Siberia could have generated significant greenhouse gases to set off global warming.
Now, Grasby and his colleagues Benoit Beauchamp and Hamed Sanei said coal ash layers found in Canada`s High Arctic suggested the first direct confirmation ash might have played a role in the extinction.
“Our research is the first to show direct evidence that massive volcanic eruptions – the largest the world has ever witnessed – caused massive coal combustion thus supporting models for significant generation of greenhouse gases at this time,” said Grasby.
At the time of the extinction, the Earth only had one large land mass called Pangaea.
The volcanoes, known as the Siberian Traps, are now found in northern Russia, covering an area just under two million sq km. The ash plumes from these volcanoes are said to have travelled to regions including Canada`s arctic.
“Our discovery provides the first direct confirmation for coal ash during this extinction as it may not have been recognized before,” said Sanei.
The Earth was already heating up at the time, suffocating its oceans because of decreasing oxygen levels, the researchers suggested. And the ash may have contributed to that effect, they found.
“It was a really bad time on Earth. In addition to these volcanoes causing fires through coal, the ash it spewed was highly toxic and was released in the land and water, potentially contributing to the worst extinction event in earth history,” said Grasby.
The findings have been published in Nature Geoscience.