When you think about volcanoes, several descriptions come to mind. Awe-inspiring. Beautiful. Dangerous. Destructive. You might think that volcanos that erupt frequently are the ones that should worry everybody the most, but in fact the volcanoes that haven’t erupted in centuries pose the highest risk, especially if they’re located in heavily populated areas. The reason for this? When they go a long time without exploding, the mounting pressure builds up, so when it does occur, the results are especially devastating.