Plot: In 79 AD, the volcano Vesuvius exploded in one of history's deadliest eruptions, burying the city of Pompeii and other Roman towns along the Bay of Naples beneath layers of ash and pumice. Pompeii was rediscovered in the 18th century, but only recently have archaeologists and volcanologists come to understand exactly how the eruption unfolded, and why it took the people of Pompeii almost entirely by surprise