University researchers are suggesting that massive volcanic eruptions led to Earth's first environmental disaster - 190 million years before the demise of the dinosaur.
Up to 95 per cent of all marine species and 70 per cent of land vertebrates became extinct during this Permian-Triassic period. The Great Dying also caused the only known mass extinction of insects.
A University of Calgary team that worked in Canada's High Arctic believes it found evidence that volcanoes in Siberia burned through coal, which in turn produced ash clouds that damaged global oceans.
"We found layers of coal ash ... providing the first direct evidence that there was a significant coal combustion going on at the time of extinction," said Steve Grasby from the university's department of geoscience.
Mr. Grasby is also a research scientist at Natural Resources Canada.
It's widely believed that dinosaurs met their end 65 million years ago when a meteorite hit the Earth, but the reason for the Permian extinction had been less clear.
"This could literally be the smoking gun," said Mr. Grasby.
The impact of the volcanic eruption was so severe that it eliminated all "higher life" over a period of 200,000 years, he said, and it would take another five million years for those life forms to reappear.
The volcanoes covered an area just less than the size of Europe. The ash plumes drifted to regions now in Canada's Arctic where the researchers found the coal-ash layers.
"We saw layers with abundant organic matter ... exactly like that produced by modern coal-burning power plants," said Benoit Beauchamp, also with the university's geoscience department.
Mr. Grasby said the Earth at the time was one big land mass and was similar to the planet we know today. Environments ranged from desert to lush forests and included primitive amphibians, reptiles and a group that would eventually include mammals.
The university team's research article is being published in the magazine Nature Geoscience today.
Mr. Grasby said geological events as recent as last spring have given the world a taste of the disruption volcanoes can trigger.
"Large eruptions can cause some global atmospheric effects, just like the Icelandic volcano shutting down air travel," he said.
"But this was on a scale far beyond that. It was one of the largest in Earth history."