Vesuvius is East of Naples, Italy. It has erupted on numerous occasions, most famously in AD 79 when it destroyed the cities of Pompeii and Herculaneum. In a letter to Tacitus, Pliny the Younger described the start of the eruption:

“The cloud (the spectators could not distinguish at a distance from what mountain it arose, but it was afterwards found to be Vesuvius) advanced in height; nor can I give you a more just representation of it than the form of a pine-tree, for springing up in a direct line, like a tall trunk , the branches were widely distended. I believe, while the vapour was fresh, it more easily ascended; but when that vapour was wasted the cloud became loose or, perhaps oppressed by its own gravity, dilated itself into a greater breadth. It sometimes appeared bright, and sometimes black, or spotted, according to the quantities of earth and ashes mixed with it.” (From Mount Vesuvius : a descriptive, historical, and geological account of the volcano by J L Lobley, 1868 [400-GEO])

• J V Stephens