Roughly 252 million years ago, an extreme animal die-off occurred: 70% of land animals and 96% of marine life were obliterated, in what's known as the Permian mass extinction. What scientists still don't exactly know is why (an asteroid? volcanic eruptions?), but they now know how long it took. And the answer is ... really, really fast. MIT researchers say the extinction period's duration clocked in at 60,000 years, plus or minus 48,000 years. As Phys.org puts it, that's "practically instantaneous, from a geological perspective." To get your geological periods and catastrophic disasters straight: The die-off signified the end of the Permian period and launched the start of the Triassic; the mass die-off of the dinosaurs happened much later, 66 million years ago at the Cretaceous period's close, when LiveScience reports 85% of life was wiped out.
The researchers came to their conclusion by using cutting-edge dating techniques on tiny minerals known as zircons found in rocks in Meishan, China, that date to the period. But the rocks also held carbon dioxide data; from there, the researchers determined that a surge of the gas occurred 10,000 to 20,000 years before the die-off: Ocean acidification may have have occurred, and sea temps could have jumped as much as 50 degrees. But what was the source of the increased carbon dioxide that marked the beginning of the end? MIT researchers are now dating rocks from the Siberian Traps to determine if volcanic eruptions there could have been the culprit. (Read more discoveries stories.)