The bulge first appeared in 1996 and has now returned, but Yellowstone Volcano Observatory says there's no cause for alarm.

Earth has some massive volcanoes called "supervolcanoes" that can cause huge eruptions, way bigger than anything we’ve ever seen in modern times. Some of these, like Yellowstone in the U.S. and Campi ...

Earthquakes rattle the ground while cannon-like explosions shoot burning rock and ash into the air at speeds upwards of 600 miles per hour. The burning rocks crash to the earth, setting the grass and ...