Rocks Provide New Information About How We Recovered From Earth's Biggest Mass Extinction

Approximately 250 million years ago, the Earth's biggest extinction event occurred.

The "Great Dying," more popularly known as the "Great Permian Extinction," is dubbed history's worst extinction event. It wiped out 90 to 96 percent of the species occupying the planet, meaning what we see today originated only from 4 percent of the species that existed before.

BBC notes that the extinction underwent two phases which occurred in a span of a million years during which marine creatures were mostly affected and insects suffered the only mass extinction of their history.

The causes of these mass extinction events remain unsolved. National Geographic notes that the most popular assumptions range from a large asteroid or comet hitting the earth and flood volcanism from the Siberian Traps, a large igneous province in Russia.

Though these mass extinctions are fatal events, they bring about an opportunity for new species to be formed. It was said that after Permian-Triassic period, dinosaurs began to exist.

It took approximately millions of years before Earth recovered from the damage inflicted by the massive extinction, such as significant atmospheric disturbances, global warming and anoxic (low-oxygen) ocean waters.

A new discovery in the oceans

In February 2016, a study revealed that the delay in recovery was primarily caused by the anoxic ocean waters. Aside from lack of oxygen, the study also said waters also contained high levels of harmful compounds, known as sulphides. The researchers said life did not bounce back until the ocean fully recovered.

Yet recently, another study has been published, saying that although the water was indeed lacking in oxygen, toxic sulphide was not present--rather, there was iron.

To come up with conclusion, the group, led by researchers at the University of Edinburgh, studied rocks that were formed in an ancient ocean around the time of the extinction.

Using precise chemical techniques, they found out that oxygen levels varied at different depths in the ocean.

"We knew that lack of oxygen in the oceans played a key role in the extinction and recovery processes, but we are still discovering how exactly it was involved. Our findings about the chemistry of the ocean at the time provide us with a clearer picture of how this complex process delayed the recovery of life for so long," Dr Matthew Clarkson, of the University of Edinburgh's School of GeoSciences told Science Daily.