Supervolcanoes are like the supervillains of the geologic world, as stories of their looming threat grow ever more exaggerated. Though massive eruptions do pose real dangers, misconceptions about them abound.

According to the United States Geological Survey, a volcano is considered “super” if it has had at least one explosion that released more than 240 cubic miles of material—a little more than twice the volume of Lake Erie. That places it at a magnitude of eight, the highest ranking on the Volcanic Explosivity Index, or VEI, which is used to measure the explosiveness of an eruption.

These are very large eruptions, the impacts of which would be widespread—from avalanches of hot rock and gasses racing down the volcano's flanks