In the event of an eruption, Katla’s glacial caldera could quickly liquefy. What’s more, the resulting melt would send a colossal amount of water gushing from the island nation’s eastern shore into the Atlantic, quite possibly leading to floods of truly epic proportions. The eruption might have global climatic effects, too. National Geographic’s Ford Cochran told the BBC that a previous Katla blowout in 1783 “cooled the planet for an entire year or more,” bringing about extensive food shortages as a result. And with considerable seismic movements taking place in the vicinity, Cochran said that a fresh eruption “may be imminent.”
3. Yellowstone Caldera – Wyoming, U.S.A.
Six miles below Wyoming’s Yellowstone National Park is the lair of any fictional supervillain’s dreams – a 300-mile-wide pool of burning-hot magma; and sitting precariously on top is the cap-like Yellowstone Caldera. Together, they form part of one of the world’s biggest supervolcanoes – enormously powerful volcanoes featuring boiling subterranean magma chambers in which pressure gradually builds until they spectacularly explode. What’s more, this one is so dangerous that its eventual eruption would likely permanently change the face of the planet.