A large volcanic eruption may have triggered the first mass extinction of life, in which nearly 80 per cent of the species were lost, a study has shown. A researchers team led by David S. Jones of Amherst College in Massachusetts and Professor Kunio Kaiho of Tohoku University took sedimentary rock samples from two places -- North America and southern China.
They analysed mercury (Hg) in the samples and found that mercury enrichment coincided with the mass extinction in both areas.
"This is the product of large volcanic eruptions because a Hg anomaly was also observed in other large igneous province volcanisms," Jones observed in the paper published in the journal Geology.
Huge volcanic eruptions can produce sulfate aerosols in the stratosphere. Sulfate aerosols are strong, light-reflecting aerosols and cause global cooling. This rapid climate change is believed to be behind the loss of marine creatures, the researchers said.
There have been five mass extinctions since the divergent evolution of early animals 600 million-450 million years ago. The cause of the third and fourth was volcanic activity, while an asteroid impact led to the fifth, but the cause of the first and second mass extinctions had, until now, been unknown.
The first mass extinction occurred at the end of the Ordovician -- lasted almost 45 million years, beginning 488.3 million years ago and ending 443.7 million years ago.
This age is between the divergence of the Ordovician and land invasion of vascular land plant and animals comprising marine animals like corals, trilobites, sea scorpion, orthoceras, brachiopods, graptolite, crinoid and jawless fish. Approximately 80 per cent of the species disappeared at the end of the Ordovician, the researchers noted.
Kaiho's team is now studying the second mass extinction in the hope of further understanding the cause and processes behind it.