Around 104 C.E., Pliny the Younger sat down to write a letter. “Though my shocked soul recoils, my tongue shall tell,” he told the Roman historian Cornelius Tacitus. Then, Pliny began to describe what he witnessed during the Mount Vesuvius eruption about 25 years earlier, in 79 C.E.

Before its eruption that year, Mount Vesuvius had been dormant for centuries, making up part of the idyllic natural landscape surrounding the Roman cities of Pompeii and Herculaneum, both of which were located in southern Italy near Naples. Herculaneum was a popular resort town for wealthy Romans; Pompeii was a prosperous and bustling city with opulent villas, bars, cafes, and bathhouses, and an arena that could seat 20,000.

Though people living in the region suffered through the occasional earthquake, they were unaware of how dangerous Mount Vesuvius was. Sources vary on whether the Romans thought it was extinct — or merely a large mountain — but at the time, chillingly, locals had no word for “volcano.”

Everything changed one day in 79 C.E., when the “mountain” started to rumble and shake. The Mount Vesuvius volcano eruption would devastate the region, kill thousands, and freeze Pompeii and Herculaneum in time.

The Lead-Up To The Mount Vesuvius Eruption

Museo Archeologico Nazionale di Napoli/Public DomainA fresco found in Pompeii’s House of the Centenary, which seems to depict the Mount Vesuvius volcano.

The story of the 79 C.E. Mount Vesuvius eruption actually began about 300,000 years ago, when the volcano first began to form. In the millennia leading up to the destruction of Pompeii and Herculaneum, it erupted several times — sometimes catastrophically. The “Avellino eruption” of 1995 B.C.E., for example, destroyed every Bronze Age settlement within 15 miles.

But that frightful history was soon largely lost. Pompeii was settled by the Greeks in the 8th century B.C.E. and was loosely under Roman rule after the Samnite Wars (a series of conflicts that lasted between 343 B.C.E. and 290 B.C.E.). Then, in 80 B.C.E., Pompeii officially became a Roman colony.

Pompeii — and nearby Herculaneum — soon flourished. As many as 20,000 people lived in Pompeii, and about 5,000 people lived in Herculaneum, which became a popular resort town for elite Romans.

Public DomainA depiction of how Pompeii may have looked before its destruction during the Mount Vesuvius volcano eruption.

The cities benefited from the rich soil, which was a huge help to farmers. In Pompeii, wealthy citizens built impressive villas, and people of all classes enjoyed the city’s bustling squares, marketplaces, and amphitheater.

The first known harbinger of the Mount Vesuvius eruption came in 62 or 63 C.E., when a large earthquake struck the Campania region. A number of smaller quakes later followed, but many citizens shrugged them off. Such quakes were seen as normal. But they were actually warning signs.

The eruption of Mount Vesuvius would soon begin.