Most doomsday enthusiasts are aware of the Yellowstone supervolcano. Right now, it's just waiting for the right moment to plunge almost all of North America into darkness.
At this point, it isn't a matter of if this will happen, but when. According to some researchers, it could erupt any day now. Geologists are constantly monitoring Yellowstone for signs of volcanic activity that could indicate an eruption. Last month, they made an unsettling discovery.