Some 250 million years ago, the earth suffered the greatest biological crisis in its history. Around 95% of all living species died out–a global catastrophe far greater than the dinosaurs’ demise 65 million years ago. How this happened remains a mystery. But there are many competing theories. Now, they have discovered a new culprit likely involved in the annihilation: an influx of mercury into the eco-system. “No one had ever looked to see if mercury was a potential culprit. This was a time of the greatest volcanic activity in Earth’s history and we know today that the largest source of mercury comes from volcanic eruptions,” says Dr. Steve Grasby of the University of Calgary, co-author of a paper published this month in the journal Geology. “We estimate that the mercury released then could have been up to 30 times greater than today’s volcanic activity, making the event truly catastrophic.”