Around 250 million years ago, most life on Earth was wiped out in an extinction known as the “Great Dying.” A team led by University of Cincinnati geologist Thomas J. Algeo finds that the end came slowly from thousands of centuries of volcanic activity.

The cataclysmic events that marked the end of the Permian Period some 252 million years ago were a watershed moment in the history of life on Earth.

Earth's largest mass extinction event, the end-Permian mass extinction, occurred some 252 million years ago. An estimated 90 percent of Earth's marine life was eradicated.

While the cause of the mass extinction that occurred between the Permian and Triassic periods is still uncertain, two University of Rhode Island researchers collected data that show that terrestrial biodiversity recovered much faster than previously thought, potentially contradicting several theories for the cause of the extinction.

Harsh living conditions caused by major fluctuations in the carbon content and sea levels, overacidification and oxygen deficiency in the seas triggered the largest mass extinction of all time at the end of the Permian era 252 million years ago.