Introduction
The 79 AD volcanic eruption of Mount Vesuvius is one of the greatest natural disasters in recorded history. Accurate accounts of the day's events survived from antiquity thanks to documents and histories maintained by Roman citizens living at the time of the eruption.
The devastation caused by Mount Vesuvius preserved the nearby cities of Pompeii and Herculaneum in layers of ash and sediment. While catastrophic for those caught up in the disaster, the cities were frozen in time, providing researchers with a literal snapshot of daily life during the time of the early Roman Empire.
Location
Mount Vesuvius is located just south of modern-day Naples, in Italy's Campania region, which is in the southwest of the peninsula. The volcano's summit is 4,203 feet tall, and its' western slope reaches the Bay of Naples. The surrounding area is densely wooded with oak trees. Today, there are multiple vineyards on the mountain slope due to the soil's high fertility.
Nearer the summit, the area is barren and rocky. Vesuvius does not feature a peak; instead, the volcano has a flat top with a wide cone featuring steep sides forming a surrounding rim. Over time, eruptions and the intense heat from lava caused the rock that formed the peak to break down, creating the concave depression from which the cone rises. Vesuvius' height changes over time due to the constant eruptions and subsequent rock resettlement.
Name
There is some debate between historians over the origin of Vesuvius' name. Some propose that the volcano's namesake is Hercules. Zeus was sometimes referred to as "Ves," so Vesuvius translates to "Son of Ves." Others speculate that it's derived from the Oscan word "fes," which means smoke. Another group of scholars contends its name comes from "ves," a Proto-Indo-European root word meaning "hearth."
Formation and Geology
Mount Somma, the mountain Vesuvius sprang from, began forming when the African and Eurasian tectonic plates collided, creating a subduction zone. During the convergence, the African plate went under the Eurasian plate. This collision heated the trapped water, which lowered the upper mantle's melting point. The trapped heat melted the subterranean rocks to create magma, which rose between the remaining rock due to its lower density.
About 17,000 years ago, the cone of Vesuvius formed within the caldera, or pit, at the top of Mount Somma that developed when a surge of magma broke through the crust in an eruption and began the volcano's formation. Over thousands of years, the volcano grew as lava eruptions spewed, flowed, hardened, and added to the mountain. Based on its evolution, Vesuvius is classified as a somma-stratovolcano.
Along with other volcanoes formed between the plates, Vesuvius is part of the Campanian Volcanic Arc that includes Mount Etna and Stromboli. Rocks that erupt from Vesuvius are andesite, a silica-rich stone. Their chemical makeup makes Vesuvian eruptions especially volatile.
Settlement
Archaeologists have uncovered remnants of settlements formed around Vesuvius dating to around 1,800 BC. Strabo, the Greek historian and author of Geographica, discussed Vesuvius and its flat top, speculating about its volcanic activity. Based on Roman accounts, residents were well accustomed to the ongoing earthquakes in the region. While unable to predict eruptions, multiple ancient civilizations understood the region's volatility.
Despite the uncertainty, people chose to settle there thanks to the highly fertile soil produced by the volcanic rock. The land around Vesuvius allowed orchards and crops to thrive. The region's proximity to the water also made it a sensible place to settle, especially as Greek dominance gave way to Rome, who dominated the seas.
Life During Ancient Rome and the 79 AD Eruption
Researchers reconstructed the timeline of Vesuvius' most famous eruption thanks to records left behind by Pliny the Younger, who was staying in Neapolis (Naples) at the time, scientific analysis of the stone, and excavation of Pompeii and Herculaneum.
The Eruption
Volcanic activity is often preceded by shifts in seismic activity, some that are barely perceptible and some that are significant. Today, seismologists monitor areas around active volcanoes for insight into potential eruptions. The ancient Romans expected minor earthquakes, and indeed were used to them. There is documentation from Pliny the Younger indicating residents accepted seismic activity as a part of their daily life.
In 62 AD, a massive earthquake struck the region around Vesuvius. There is documentation of the death of livestock residing near Vesuvius, likely indicating asphyxiation from a release of toxic gas. The earthquake was likely a precursor to Vesuvius' eruption as underground lava movement intensified.
The two-day eruption event began on 17 October 79 AD. According to surviving records, there was a loud explosion in the afternoon. A high-altitude column formed directly above the volcano's center, sending ash into the sky. Magma and gas were also part of the cloud. They chemically combined and formed pumice, a fine and porous volcanic rock.
This mixture of ash and pumice began to fall. The sight of the initial eruption gave citizens of the nearby cities who realized the impending danger time to flee. The prevailing winds took the cloud of gas, ash, and pumice southeast, coating Pompeii. The accumulation was so significant that it crushed structures and buried items left behind.
The next day, the accumulation of rock and debris in the air became too heavy for the gas cloud to support. The column put out by the volcano crashed back down onto it, dropping an intensely hot mixture of gas, rock, and ash called pyroclastic material onto the mountain top. This initial mixture then flowed downhill to the east, sparing Pompeii but submerging Herculaneum.
Unlike lava, pyroclastic surge travels rapidly and is relatively cool. The eruptions continued, reconstituting the column and creating more pyroclastic accumulation. Three additional surges then buried Pompeii and continued covering Herculaneum.
Loss of Life
Pompeii was an economic hub for trade and commerce, making it a densely populated urban center. Excavations have uncovered the remains of over 1,000 individuals who died because of Vesuvius' eruption. As mentioned above, the initial eruption gave citizens some warning to escape, but there is no way to estimate the true extent of the casualties. Pompeii's large population would have made a mass exodus difficult.
In addition, most of the recovered remains were found indoors. These people either died in roof collapses due to the ash's weight, exposure to the high heat, or suffocation due to the combination of gas and heat depressing the oxygen supply.
Herculaneum was a lower population rural area, believed to be a seasonal resort community for wealthy Romans. The residents of Herculaneum had more time to flee because they were spared from the initial downfall of ash and rock.
Even so, 300 bodies were discovered at the shore and inside the city's boathouse. Presumably, these individuals were waiting for rescue ships but couldn't depart before the pyroclastic surges began.
Pliny the Elder
While historians used Pliny the Younger's written accounts to reconstruct the events of the eruptions, Pliny the Elder provided much of his information. The uncle and nephew were in Misenum, 22 miles away across the Bay of Naples, when Vesuvius erupted. Seeing the column rise, Pliny the Elder, who commanded the Roman navy at Misenum, began considering a rescue effort.
That same day, a messenger arrived with a request for rescue from Rectina, a friend of Pliny the Elder who resided at the base of Vesuvius. He departed for Pompeii with five galleys. While his forces went on, he broke off with a crew in a light vessel to rescue his friend.
The rescue party encountered ash, pumice, and falling rock as they neared the shore. They were unable to make a landing and diverted to the nearby town of Stabiae. They sheltered there overnight, but the accumulation of ash and rock necessitated their escape. Unfortunately, they were unable to depart by sea. Pliny died on the shore, likely from exposure to the toxic gas produced by the eruption.
The remainder of the rescue party escaped by land and reported their experiences and the nature of his uncle's death to Pliny the Younger. Reports of the fallout of the eruption and fire observed at the top of Vesuvius were documented in two letters sent on by the younger Pliny.
Aftermath
The surge decimated plant and animal life in the area. The release of toxic gases and residual heat initially made the surrounding land uninhabitable. The ash and pyroclastic flow that buried Pompeii and Herculaneum cooled and hardened over time.
The exposure to extreme heat petrified many items, locking the cities as they were during the eruption. As the layers of sediment solidified, they protected the cities' ruins from natural erosion and theft over the centuries.
Other Notable Eruptions
Vesuvius remains the only active volcano in continental Europe. While no subsequent eruptions have matched the 79 AD event's output or destruction, there have been numerous eruptions in the last 2,000 years. They include:
- A significant eruption in 203.
- Eruption in 472 that produced enough ash that it spread over 750 miles, reaching Constantinople.
- A series of eruptions in 512.
- A 1036 eruption that had the first recorded lava flow.
- After about 400 years of inactivity, Vesuvius erupted in December 1631, producing significant lava flows that killed 3,000 people and destroyed everything in its path.
- There were 22 more eruptions over the following 400 years.
- A 1944 eruption, the most recent, lasted from March 13 to 18. Lava filled the volcano's rim, which eventually overflowed and destroyed the villages of San Sebastiano al Vesuvio, Massa di Somma, and Ottaviano. The ash and ejected rock fragments destroyed at least 80 planes the United States Air Force stationed at the nearby Pompeii Airfield. To see footage of this eruption on YouTube, click here
Vesuvius Today
Vesuvius remains active today. The question for scientists is when, not if, the volcano will erupt again. The longer the volcano goes between eruptions, the greater the buildup of gases from the magma heating rock. The resulting increase in pressure means the next event will likely be more severe.
The current projection predicts that the next eruption will be comparable to the 1631 event, meaning significant pyroclastic surges and large amounts of ash and rock pumped into the air.
Today, the area around Vesuvius is densely populated. Naples is a major urban center in southwest Italy and the region is a hub for tourism. Italian officials estimate 600,000 people live in the "red zone"; the area most likely to experience a pyroclastic flow.
Evacuating these residents would require at least 20 days' notice to protect everyone. Italians living outside the "red zone" will also need to be evacuated to avoid falling rocks, ash, and toxic gases that could spread based on wind direction and kill residents.
Frighteningly, over 3 million Italians live within the radius that would be impacted by a significant eruption.
Proactive Steps
Evacuations are costly, time-consuming and distressing for people. If an evacuation is called too early and an eruption does not occur, then a lot of time, money and disruption will have been for nothing (although some people would argue it was better to be safe than sorry!). Conversely, if an evacuation is called too late, people will not have enough time to escape by boat, car, or train, which could result in many deaths. The national and regional governments continually monitor the volcano for potential activity and have formal egress plans.
However, their key strategy is to depopulate the region. In 1995, they declared the area immediately surrounding Vesuvius a national park. The government has also stopped new construction nearby, and introduced measures to persuade and incentivize nearby residents to relocate.
Visiting Vesuvius
Tourism in and around the volcano of Mount Vesuvius drives the economy in Naples. Visitors can travel by bus into the park and take a short hike up to Vesuvius' crater. Steam almost always appears at the top of the volcano. At this elevation, visitors can enjoy spectacular views of the Bay of Naples to the west and the Catalagonia plain to the east.
The ruins of Herculaneum and Pompeii are to the west and south of Vesuvius. Both are UNESCO-protected sites. Visitors can tour each excavation and view preserved Roman homes, temples, streets, goods, and tools from ancient Rome. Both sites provide a striking glimpse into the Romans' highly-developed urban planning, architectural and engineering ingenuity.
Did you know...
Eruptions of high levels of gas, heat, and rock that create a tall vertical column above a volcano are called Plinian Eruptions, after Pliny the Younger, whose written account documented the disaster.
Did you know...
Pompeii was founded around the 6th century BCE by the Osci or Oscans, a people of central Italy, on a hill near the mouth of the Sarno River or Sarnus River, already in use as a safe port by Greek and Phoenician sailors.
Did you know...
Pliny the Younger had three wives but no sons. Only his last wife, Calpurnia, occasioned emotional words in the letters. He was quite wealthy and owned several villas in Italy; the two villas in Como, his native town, were named "Tragedy" and "Comedy".
