I'll let someone else tell you about Pliny the Elder and the Younger, the only surviving accounts of Pompeii's 79AD destruction. Cassius Dio, a historian in the second and third centuries AD, recounts the infamous eruption of Mount Vesuvius with some added details, perhaps the details you're seeking.

Cassius tells that some believed that the Titans had awakened from the earth and were preparing to rebel again. He reports that "many of their forms could be discerned in the smoke and, moreover, a sound as of trumpets was heard" (Book 66 23.1). He describes how the giants went from the mountain to the cities and left drought and earthquakes in their wake. He reports that others believed the universe to be dissolving into fire. Cassius tells that the reaction in Rome was that the sun was fleeing the earth and that the earth was being raised into the sky (along with the end of the world and Titanomachy Redux).

All of this is important because, while Cassius doesn't go to any great lengths to tell about it, Vesuvius erupted during his lifetime. With Pompeii still in relatively recent memory (only two or three generations removed), another eruption wouldn't be met with as much doomsday panic.

Another thing, Romans didn't have a word for "volcano." Our word "volcano" comes from the Roman god of fire, Vulcan. To give you an idea of how important the fiery mountain was, they did not feel the need to invent a word for it nor is it given any special epithet.

[Here's a link] (http://faculty.cua.edu/pennington/pompeii/plinyletters.htm) to Cynthia Damon's translations of Pliny the Younger's eyewitness accounts (the only ones) describing the eruption. The first (VI, 16) describes the death of his uncle, Pliny the Elder. The second (VI, 20) describes the experience of his mother and Pliny 20 miles across the bay at Misenum. Both were written some years after the fact at the request of his friend, the historian Tacitus, who wanted to include the accounts in his Histories, though the section that would have included them is lost.

[Suetonius' Lives of the Caesars] (http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Suetonius/12Caesars/Titus*.html) includes this information in his life of Titus (79-81) about his efforts to aid the stricken cities:

There were some dreadful disasters during his reign, such as the eruption of Mount Vesuvius in Campania, a fire at Rome which continued three days and as many nights, and a plague the like of which had hardly ever been known before. In these many great calamities he showed not merely the concern of an emperor, but even a father's surpassing love, now offering consolation in edicts, and now lending aid so far as his means allowed. He chose commissioners by lot from among the ex-consuls for the relief of Campania; and the property of those who lost their lives by Vesuvius and had no heirs left alive he applied to the rebuilding of the buried cities.

Edit: Fixed the Pliny link.