Vesuvius eruption

Vesuvius is one of the most famous active volcanoes in the world and, during its 10,000 years of existence, it has been the protagonist of about seventy eruptions: the most tragically famous was in 79 AD, when lava and ash buried the Roman cities of Pompeii and Herculaneum.

When will Vesuvius next erupt?

Studies by the American volcanologist Flavio Dobran of New York University confirm that a 15-minute eruption of Vesuvius would devastate the entire Gulf of Naples and kill a million inhabitants.

The American volcanologist is certain that Vesuvius, which has been ‘dormant’ since 1944, will explode with unprecedented power and, in just four minutes, swallow up five or six municipalities in the red zone (of the evacuation plan).

His latest report is even more tragic than the previous ones.

The American volcanologist claims that the next time Vesuvius erupts, a column of gas, ash and lapilli will rise three thousand metres above the crater and avalanches of fire will roll down the sides of the volcano at a speed of 100 metres per second at a temperature of 1,000 degrees centigrade, destroying the entire landscape within a radius of 7 kilometres, sweeping away roads and houses and burning trees, asphyxiating animals and killing perhaps a million human beings in just 15 minutes.

This is a documented hypothesis, the result of extensive studies. The only unknown is when the next eruption of Vesuvius will occur.

Dobran has designed a global volcanic simulator, a computer model capable of reconstructing the past eruptions of various volcanoes in order to describe future ones. After analysing the data, Dobran’s global volcanic simulator drew up a hellish scenario: just 20 seconds after the explosion, the mushroom cloud of gas and incandescent ash had already reached a height of 3,000 metres. One minute later, the burning avalanche will already be two kilometres from the crater. In three minutes it will reach the towns of Ottaviano, Somma Vesuviana and Boscoreale. In four minutes it will reach Torre del Greco and Ercolano. Sixty seconds later it will reach Torre Annunziata.

Vesuvius is the most dangerous volcano in the world because of the size of the population living in the surrounding area (three million). It is a natural wonder and, at the same time, a loaded gun pointed at your head.

It is hoped that experts will be able to recognise the warning signs early enough to save the hundreds of thousands of people living in the danger zone. If not, and if the next eruption of Vesuvius is devastating, the city of Naples could be the next Pompeii.

The most violent eruptions of Vesuvius are called Plinian eruptions. They can kill thousands of people in a matter of seconds because of the deadly killer, the pyroclastic flow.

According to scientists, when the moment comes when the column of hot air above the volcano can no longer contain the large amount of incandescent ash and gas escaping from the crater, the column collapses downwards, creating a kind of immense avalanche. An avalanche of incandescent material that can exceed 1000 degrees Celsius and move at hundreds of kilometres per hour. Anyone unfortunate enough to be near a pyroclastic flow would barely have time to notice it before dying.

To get a concrete idea of how violent a pyroclastic flow from a Plinian eruption can be, let us compare it to the collapse of the “Twin Towers” in the New York tragedy of September 11, 2001. The eruption of Vesuvius in 79 AD produced a shock wave with a force ten thousand times greater.

Plinian eruptions of Vesuvius are often separated by thousands of years, but in the meantime minor eruptions occur, which are referred to by scholars as ‘sub-Plinian’ eruptions.

The difference between a Plinian and a Sub-Plinian eruption is only the scale. Plinian eruptions of Vesuvius project a mountain of incandescent material into the sky, which then collapses to the ground over an enormous area. Sub-Plinian eruptions, on the other hand, are the same but on a smaller scale, i.e. they affect a smaller area. Sub-Plinian eruptions are therefore less severe than Plinian eruptions, but can still cause casualties. The most recent sub-Plinian eruption of Vesuvius was in 1944. This eruption is not comparable to the one that destroyed Pompeii in 79 AD, but it was still a dangerous event that claimed 26 lives. This is why it is important to understand when the catastrophe will strike. No volcano in the world can really be predicted far in advance and predicting the next eruption of Vesuvius is impossible. Scholars must look for clues hidden in the volcano’s past to determine its future. For this reason, past eruptions of Vesuvius are of vital importance.

In the event of the next eruption, the only way to save the population is to evacuate it completely within a radius of 20 km from the crater. An enormous distance, which would involve the entire city of Naples, and therefore 3 million people. This would be an essential safety measure because it is impossible to make predictions about the type of eruption that will take place, just as it is impossible to predict the minimum safety distance that would guarantee that people would be rescued.

The city of Naples has already been hit in the past: in 1780 BC there was a very violent eruption of Vesuvius (Plinian), called the Avellino eruption.

Recent discoveries have brought to light the remains of a Bronze Age population about 15 kilometres from Vesuvius. Here two skeletons of a young woman of about 19 years and a man of about 45 years were found, roughly dating back to 1780 BC.

These two people died covered by about 1 metre of pumice. The victims did not have time to escape and suffocated to death in the first moments of the eruption.

The most surprising thing is the location of the devastated village, which lies within the metropolitan area of Naples; an area that had always been considered safe. The discovery of these remains is proof that Vesuvius can produce an eruption that can reach the city of Naples. This makes Vesuvius a potentially much more dangerous volcano than previously thought. Today, 3 million people live in the Naples metropolitan area and would be at great risk if another eruption like the one in the Bronze Age occurred. Obviously the Avellino eruption represents the worst-case scenario that could occur in a future eruption, but it is still a real hypothesis to be considered.

As mentioned, scholars must look for clues hidden in the volcano’s past to determine its future.

Will the next eruption of Vesuvius be anticipated by a major earthquake?

We know that this has happened in the past, but it is not certain that the next eruption of Vesuvius will be preceded by a major earthquake. Volcanoes cause different earthquakes from those emanating from tectonic areas. Indeed, some scientists fear that the most likely warning sign could be a seismic swarm concentrated in a short period of time.

This type of phenomenon is constantly monitored by the Vesuvius Observatory.

Will the next eruption of Vesuvius be anticipated by a ground swell?

Historians have made a surprising discovery, a phenomenon that occurred before the violent earthquake of 1979. The entire area around the Gulf of Naples swelled and deflated, following the movements of the magma chamber. Changes in the pressure of the magma below Vesuvius had this effect: when the pressure went up, the ground level went up, when the pressure went down the ground level went down.

This phenomenon is called bradyseism; in Greek it means slow earthquake.

Over the years it is no longer perceived as a movement of the earth but of the sea. The sea seems to suddenly rise in level and then recede, and this phenomenon is repeated for years.

Before the eruption of 79 AD, the coastline underwent serious variations and advanced and receded several times, renewing itself continuously.

A change in the ground level could be another anticipatory sign of the next eruption of Vesuvius.

Although it is impossible to say when the next eruption will occur, scholars agree that it will be a devastating event because the size of the magma chamber beneath the volcano is comparable to those of the last two major eruptions.

Studies have shown that in AD 79, before the eruption, the magma was trapped at a depth of about 8 km. Unfortunately, this is the same depth that instruments detect today. There is currently enough magma under Vesuvius to produce a violent eruption, and sooner or later that magma will rise to the surface.

In the worst-case scenario, if the next eruption of Vesuvius were to be violent, it would cause pyroclastic flows that would devastate the region and leave no escape for anyone hit by such a wave. The heat would immediately invade the body, which would react by bending all four limbs in an automatic reaction. One moment and you die. Considering that the propagation of the incandescent wave would travel at a speed of hundreds of kilometres per hour, the only possible salvation would be not to be run over, and therefore to have already escaped. And with millions of people fleeing, the area would immediately fall into chaos and the evacuation problems would be enormous.

Evacuation plan in case of Vesuvius eruption

Civil protection experts have to deal with this issue and prepare for the inevitable.

Theoretically, up to a week should pass from the appearance of the first symptoms to the actual eruption, and the evacuation plan should be completed within three or four days.

The current emergency and evacuation plan is based on a sub-Plinian eruption and would involve evacuating 600,000 people in three or four days.

But what if this does not happen and there are no 3 or 4 days? What if the eruption is not sub-Plinian? The emergency plan for the next eruption of Vesuvius does not take into account the evacuation of 3 million people; this difference could be the cause of a great tragedy.

There are 18 towns in the Vesuvius area that are included in the risk zone in the event of a Vesuvius eruption, known as the red zone. This is where evacuation manoeuvres will be concentrated at the first signs of instability from Vesuvius. Napolin is not included in this zone. The boundaries of the red zone, among other things, have been drawn on the basis of municipal boundaries. This is a harshly criticised and illogical choice, because when the pyroclastic flow hits the area it will certainly not stop just because it has arrived at a city boundary. In some cases the boundaries of the red zone are up to 7 kilometres away from the crater, in others up to 12. A 15-kilometre radius circumference should probably have been drawn to identify the high-risk areas.

In any case, Vesuvius, regardless of its destructive force, and perhaps partly because of it, remains one of the most fascinating natural resources of the Campania region.