Canadian researchers say massive volcanic eruptions, burning coal and accelerated greenhouse gas “could literally be the smoking gun” that explains the Earth's most severe extinction event - latest Permian extinction, also known as the Great Dying.

Described as the “mother of all mass extinctions”, the Permian extinction wiped out 95 percent of life in the sea and 75 percent of life on land about 250 million years ago but it has never been clear what caused the extinction.

Researchers at the University of Calgary say they have discovered evidence of what happened at that time - massive volcanic eruptions burnt significant volumes of coal, producing ash clouds that had huge impact on global oceans.

The ash plumes from the volcanoes in Siberia traveled to regions now in Canada's Arctic where coal-ash layers where found.

Earlier research has suggested massive volcanic eruptions through coal beds in Siberia would generate significant greenhouse gases causing run away global warming.

The research team say they have now discovered layers of coal ash in rocks from the extinction boundary at Buchanan Lake, Axel Heiberg Island, Nunavut - similar to that spewed by modern coal burning power plants - and that provide the first direct proof of significant coal fires at the latest Permian 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, says Steve Grasby of University of Calgary.

The ash, the researchers say, may have caused even more trouble for a planet that was already heating up with its oceans starting to suffocate because of decreasing oxygen levels.

“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,” says Grasby.