Krakatoa, Indonesia 1883 and Mount Saint Helens, United States 1980. Two of the scariest eruptions in history, gigantic, destructive. Both caused by volcanoes that had remained inactive and silent for a long time and then suddenly exploded as if they were immense deposits of dynamite. And this is what happened with Vesuvius, when it erupted in 79 AD, devastating Pompeii and Herculaneum.