Overlooking the bay of Naples, Mount Vesuvius is today part of one of the most recognized skylines in the world. But how did Vesuvius Mons (Latin for Mount Vesuvius) look on the day of its famous eruption in the August of 79 AD?
The appearance of Mount Vesuvius and its surrounding area before that catastrophic eruption has been – and still is – a debated topic for geologists and archaeologists alike. We have some geological clues, written descriptions and even some contemporary drawings. Roman authors who cite Vesuvius in their works include Strabo, Vitruvius and Diodorus Siculus.
In his Geographia, Strabo describes the "burned" rocks of the mountain and compares Vesuvius to the more active Mt. Etna. Additionally, Diodorus and Vitruvius seem to have grasped the volcanic origin of the mountain:
It is said, that once a fire burned below Vesuvius and spilled out a boiling flood, inundating the nearby countryside: so that the rock now called Pompeian Pumice, once was another sort of rock, reduced by fire to its actual quality.
Though some naturalists at the time recognized and described Vesuvius' volcanic nature, the quiet mountain was not considered a real danger anymore. Pliny the Elder, a naturalist who owned a villa near the gulf of Naples and who died during the eruption, never even mentioned the volcano in his works. Additionally, despite many fresco paintings were found in the ruins of the city of Pompeii, drawings of Vesuvius are exceptionally rare. Just one preserved fresco, discovered between 1879 and 1881 in the "House of the Centenary", probably shows Mount Vesuvius. This fresco of Bacchus and Vesuvius shows the mountain with steep slopes and a single crater (unlike today).
Bacchus, god of pleasure and vine, shown with a mountain covered by vineyards. Soils of volcanic... [+]
That fresco, however, doesn't quite match contemporary accounts. Indeed, Strabo described the slopes of Vesuvius as being covered by vineyards and forests, but he also mentioned a flat top or a volcanic dome (?) without vegetation - a detail not shown in the fresco.
Vesuvius Mons overlooks these cities, covered entirely, with the exception of the summit, by cultivated fields. The top is mostly flat, without vegetation and of grayish color, it shows deep fissures, whose reddish rocks seems have been eroded by time.
Another, lesser-known drawing from Pompeii seems to support Strabo’s description. In the background of a (today lost) fresco from the "House of the Citharist", discovered between 1853 and 1868, a couple (identified as either Aeneas and Dido or Mars and Venus) is shown relaxing in the shade of a flat-topped mountain.
Historian Dio Cassius, who gives the most detailed description, wrote:
... Mount Vesuvius overlooks the sea … and contains copious sources of fire, the summit is of regular shape, so that the fire is found in the center.. the fire consumes the rocks in the middle, however the peaks around retain their ancient height, but the inner part, consumed by fire and time, has become hollow and was refilled by sediments, so that the entire mountain looks like an amphitheater. The higher ground of that mountain is covered by many trees and vines…
It is strange that Cassius mentions a large crate instead of a flat summit as other contemporary historians. Maybe this description was made after Mount Vesuvius erupted. Available geological data isn't good enough to settle this debate, but it also suggests that Vesuvius was probably a flat-topped, unimpressive mountain before the 79 AD eruption.
The crater that formed during the 79 AD eruption was later destroyed by an eruption in 472 AD. Since 1631, though, pictures of Vesuvius show today's familiar outline, with its two peaks formed by the outer caldera rim of Monte Somma, surrounding the inner central crater or Gran Cono.
“View of Vesuvius and surrounding area after the destruction by the eruption of the year 1631” by... [+]
But it may surprise you to learn that the date of the 79 AD eruption itself is disputed.
Pretty much all textbooks mention August 24, as the beginning of the eruption. This day is based on two letters the Roman author Pliny the Younger (nephew of Pliny the Elder) send to Tacitus, a historian who had asked his friend for information about the death of his uncle.
However, the original letters by Pliny didn’t survive into modern times, so their text is only known from transcriptions from the Medieval era. By that point, various versions of the letters existed, showing dates ranging from August to November (and some without any reference to a date at all). This discrepancy can be explained by various translation and transcription errors occurring over time, almost inevitable considering that the eruption happened almost 19 centuries ago.
Some circumstantial evidence suggests the eruption occurred later than August:
- The famous gypsum-casts found in Pompeii show people wearing thick cloths, unusual for August but appropriate for the cool temperatures of early autumn. Portable stoves, many ready to use, were also discovered in many buildings.
- Despite the fact that the volcanic sediments preserved organic remains very well, fruits typically found in summer are rare. However, autumn fruits, like olives and figs, are common. This could suggest that those stores were buried some time after the harvest, perhaps late October.
- Large jars, used to ferment wine, were discovered already sealed in Pompeii. Considering that grapes are harvested in early autumn, the fermenting wine could also suggest an eruption in late October.
- A coin, a Capricorn Silver Denarius issued by emperor Titus in July-June 79 AD, was discovered buried in the ashes of Pompeii. This also suggests that the eruption occurred late in summer/early autumn. However, as the inscriptions on the coin are difficult to decipher, the age of the coin is still disputed.
- Archaeologists have uncovered the preserved remains of garum, a spicy fish sauce made using the fish species Boops boops (bogue), which abounds in the Mediterranean Sea from July to August. This could also point to a time of the eruption sometime between late August-September, given the time needed for fishermen to provide fresh fish to manufacturers, who in turn needed about a month to produce the garum.
In addition to the above, there's also some geological evidence - such as the distribution of ash deposits - that casts doubt on the August date. The mapped ash layers suggest that during the eruption, the wind came from the east. This wind pattern is unusual for summers in Naples, but common in the rest of the year.
Though we know more about the 79 AD eruption of Mount Vesuvius than other historic eruptions, it's still a cold case in the history of volcanic investigations.
Interested in reading more? Try:
NAZZARO, A. (1999): The shape of Vesuvius before the 79 A.D. eruption according to a new finding from a Pompei fresco and Vesuvius central cone history in the last 2000 years. Annali di Geofisica, Vol.42(4): 715-723
