The Biggest Extinction on Earth

Around 250 million years ago, a huge volcanic eruption triggered a deadly series of events that wiped out 95% of all species on Earth. Scientists have been piecing together the story of what happened.

Our planet has a troubled and turbulent past: five catastrophic natural events have caused mass extinctions of life on Earth. Perhaps the most famous one is the asteroid impact that caused the demise of the dinosaurs. But the most extensive extinction event occurred even before dinosaurs were around. In the Permian era, about 250 million years ago, a destructive volcanic eruption radically altered conditions on Earth and scientists are still piecing together evidence in an attempt to understand its devastating impact.

Credit: Dominic Morel

 

A view of the barren landscape in Karoo, South Africa.

Clues in the earth

Paleontologist Roger Smith from the Museum of South Africa has been searching for hints about the extinction in the Karoo basin in South Africa. Today, it’s hard to imagine life ever thrived in this barren, inhospitable landscape where living things struggle to survive. But by examining rock strata in the area, layers of rock that have built up over time, he has built up an impression of what existed here in the past.

Smith has been studying a layer of blue-green mud-rock laid down 300 million years ago. Analysis of the layer has revealed that it is made up of sediments deposited by frequent floods. “These blue-green mud rocks of the Permian represent lush wet flood plains. Lots of life, lots of flourishing vegetation, and many types of mammal-like reptiles,” explains Smith. Above the lush mud-rock layer sits rock that Smith describes as the “death zone” since it is completely devoid of life. The rocks contain no evidence of animal life, let alone plants or even soil.

For over 150 years, the reason for the lifeless conditions in the Karoo basin has been a mystery. But in the early 1990s, some researchers stumbled on an exciting clue thousands of miles away in Siberia.