When a magnitude 8.5 mega-earthquake struck off the Indonesian island of Sumatra in February 1861, it caused the land to convulse, stirring up a wall of water that crashed on nearby shores and killed thousands of people. 

Now, it seems that tragic event was no isolated incident: It actually marked the end of the longest earthquake ever recorded, which crept through the subsurface for a whopping 32 years. Known as a slow-slip event, these kinds of quakes have been known to unfurl over days, months, or years. But the newly described event lasted more than twice as long as the past record-holder, scientists report in Nature Geoscience.

"I wouldn’t have believed that we would find a slow-slip event