Undoubtedly one of the most spectacular volcanic eruptions ever recorded in ancient history was that of Mount Vesuvius in 79 A.D. It was described by one of Rome's most famous writers and observers of natural phenomena, Pliny the Elder. As the eruption began, he viewed it from a distance but then asked his nephew, Pliny the Younger, who was writing down his uncle's notes, to take him towards the erupting mountain so that he could help evacuate the people.
For most of the inhabitants of the two towns at the base of Mt. Vesuvius help came too late. Some were able to flee towards the peninsula, which is now the site of the town of Sorrento, but these were relatively few. In fact, Pliny the Elder himself died on the shores of the Bay of Naples. His nephew survived with the precious notes his uncle had dictated. Pliny's efforts at studying Vesuvius were immortalized by the term "plinian" or "plinean", which describes a huge volcanic eruption.
In 1975, I was able to take a car up to Mt. Vesuvius. It was an awesome sight to see the caldera bubbling with magma here and there. I had already seen similar manifestations in Yellowstone Park, Wyoming some years previously. I don't know how wide the caldera of Mt. Vesuvius is but it was a truly awe-inspiring site. It looked fairly peaceful, but one could never forget that the next eruption might not be too far away.