The Campania Plain, Part 6: Facing Neapolitan Volcanic Risk

We started this series with a view of the Campania Plain and Naples as a sort of “living Pompeii” before that city’s burial in AD 79.

Now it’s time to look at the interface between modern Campanians and their volcanoes.

What can be done to protect these millions, at risk from Vesuvius, Campi Flegrei, and Ischia?

Is there an emergency plan?

Short answer: For Vesuvius, yes, and one is in the works for Campi Flegrei. Ischia has real-time seismic monitoring, since the most likely hazards there right now are earthquakes and landslides.

Details: A shallow local earthquake on the island of Ischia (related to volcano-tectonic movements of Mount Epomeo) leveled much of the resort town of Casamicciola in July 1883, killing over 2,200 people.

Giulio Grablovitz, via Wikimedia

Two years later, Giulio Grablovitz established an observatory there, spurring research into the island’s complicated geophysics and structure. However, the next deadly quake — the first big one to be studied by modern methods — didn’t happen until August 2017.

For Earth, those 134 years were too brief to even be called a blink of the eye. The 2017 quake happened immediately after the one in 1883.

To us, the interval between two big seismic events was a long enough span of time for most of the scientific discipline called Geology seismology to develop, as well as several technological and intellectual revolutions that have made the present monitoring networks on Ischia and elsewhere possible.

That’s the problem with planning for geological hazards — our planet operates on a much longer time scale than what we’re used to.

And we’re still learning. Despite all of that human progress in 134 years, we still don’t know when the next big temblor will hit Ischia.

Geocientists can only monitor this attractive little Neapolitan caldera volcano for swarms of seismic activity or other potential signs of trouble.

It’s necessary to be more proactive with Ischia’s bigger, livelier neighbors: Campi Flegrei and Vesuvius.

In terms of eruptions, Campi Flegrei was quiet for thousands of years (except for constant sulfurous fuming and bubbling mud pots at La Solfatara Crater on the outskirts of Pozzuoli) until September 29, 1538, when the ground split open in the nearby town of Tripergole and lava fountained and poured out.

It was exactly like this but in Europe and resulting in a somewhat smaller cone. Imagine it occurring in a world where no one knows how volcanoes work!

You won’t find Tripergole on the map now — its 16th-century homes, streets, spa, and hospital are buried underneath the 440-foot-high Monte Nuovo spatter cone built by that eruption.

In retrospect, the precursors were obvious.

Scarth describes the details well in Chapter 6. For example, rising magma pushed up the floor of Pozzuoli Bay so much that the monarchy granted new land edicts to the town of Pozzuoli in 1501, 1503, and 1511.

There were earthquakes, too, starting at least as early as 1469. Some of them were very damaging, and a few people died in them when buildings collapsed.

Today’s sensitive monitoring equipment could pick up much more subtle seismicity from underground magma movement, long before an eruption.

The quakes got worse in the early 1530s and especially in 1538. By September 27th and 28th, the town of Pozzuoli was rocking, and at noon, the ground rose some 16 feet, according to reliable eyewitnesses.

No one understood how volcanoes work yet, so no one knew what to think of it all. When fireworks erupted out of the ground that evening, people asked themselves if it was the end of the world? God’s wrath? A portent of some major world change?

Who knew?

Most of Tipergole’s residents probably left during the preliminary earthquakes. No casualties there are mentioned by observers, according to Scarth, even though the first fissure actually opened next to the town’s spa.

The people of Pozzuoli also fled, many of them to Naples where about an inch of muddy ash covered the streets, thanks to the city’s location downwind from Campi Flegrei.

Monte Nuovo went quiet after one last explosion on October 3rd that killed over 20 people, who had ventured onto its flanks out of curiosity, in a small pyroclastic flow.

When the eruption obviously was over, the residents of Pozzuoli refused to go home. This was not acceptable to the authorities.

The viceroy, according to his biographer (as quoted in Scarth):

. . . was unwilling to consent to the desolation of such an ancient city that was of such use to the world [and] decreed that all the citizens should be repatriated and exempted from taxes for many years.

The Pozzuoli area was not quite as pretty back in 1538 after the eruption. (Roberto de Martino via Wikimedia, public domain)

So the people were forced to return and this city was put to use again, setting the scene for modern Pozzuoli’s volcanic troubles and risk.

Meanwhile, across the Gulf of Naples, Vesuvius had been dormant in 1538, but it soon fired up again.

The volcano’s “throat” had reopened with the Pompeii eruption in 79, after centuries of blockage, and it stayed open. Whenever batches of magma reached the surface, they erupted in lava flows, fountains, and mostly mild (for Vesuvius) explosions.

“Mild” is a relative term. This 1944 eruption was mild, compared to what Pompeii faced in 79 AD. (US Army)

All of this fiery but comparatively safe activity drew scientists as well as tourists, and the world’s first volcano observatory was built on Vesuvius in the mid-19th century.

Research there and elsewhere in the world laid the foundation for our modern understanding of how volcanoes work.

Which is why it seems a little odd that no one called an evacuation of Pozzuoli in 1969 when the ground there suddenly began to rise, over 400 years after the Monte Nuovo eruption.

There’s that time-scale difference again. Four centuries is not very long in geologic terms.

But to us, Monte Nuovo had been cold for a long time. People also may have overlooked the changes at first because odd things do happen in Campi Flegrei.

The ground there slowly rises and falls. This more or less constant movement, called bradyseism, is large enough to, among other things, submerge Roman ruins and other structures in the bay and then raise them back up as dry land again.

The Roman Port Julius, for example, is now underwater, thanks to bradyseism. So are those square things out in the water in that small image of Pozzuoli on the left up above — those are the tops of columns in a former Roman marketplace.

Geologic evidence suggests that bradyseism has probably has been going on in Campi Flegrei since the last big ash-flow eruption here some 15,000 years ago, which disgorged the Neapolitan Yellow Tuff that Naples now sits on and is partly constructed with.

With bradyseism just business as usual in Campi Flegrei, and without any volcanic activity there other than La Solfatara for centuries, no one expected a crisis in Pozzuoli in 1969.

But it happened anyway — a much bigger uplift of the ground than usual that played out over a few years, almost instantaneously in geologic terms.

Seismographs, of course, were a thing now. They recorded thousands of small earthquakes, most of which residents did not feel. The instruments did not reveal any clues about what was causing the crisis.

In the midst of building damage, railway breaks, and changes in the configuration of Pozzuoli Bay and its shore, thousands left the area for fear of an impending eruption or large quake.

But neither disaster happened, and most people returned after the uplift stopped in 1974.

This episode was a wakeup call for the authorities, though.

Apparently Campi Flegrei bradyseism wasn’t merely an academic curiosity. It could suddenly escalate in dangerous ways, and it might also be masking precursory volcanic activity.

This was not good.

Now planning began. And geoscientists at the Vesuvius Observatory instituted systematic seismic, geophysical and geochemical monitoring of the area.

When the next bradyseism crisis came in 1982, they also set up shop on Posillipo Hill (part of the caldera) to study events in more detail.

As it had done in the late Sixties and early Seventies, the ground again continued upwards, more or less consistently. In 1983, after a couple of moderately strong earthquakes, authorities evacuated 40,000 people from Pozzuoli, resettling some of them permanently at Monte Rusciello, a newly built town.

Then uplift stopped in December 1984 and the floor of the caldera once more began to slowly subside.

No eruption happened during either crisis.

By now, volcanologists were aware that Campi Flegrei belongs to a class of volcanoes called “restless calderas.”

All told, more than 130 restless calderas have been recognized around the world. Fifteen or twenty of them show some vertical ground motion and earthquakes each year. Usually there is no eruption.

What makes calderas restless? Volcanologists are still trying to work this out.

Whatever causes it — magma movement, perhaps, or heated water and other fluids — works miles underground, in a very complex caldera structure, and can only be studied indirectly.

In southern Italy, after two decades of quiet, the ground in Campi Flegrei once more started to rise in 2005, though this third crisis has been much less intense than the previous two – only about 10 inches in nine years. (Chiodini et al., 2015)

That’s not much, compared to the net uplift of 15 feet between 1969 and 1984.

But the rate of change might be accelerating a bit. And againist a geological background of increased fumarole activity and changing gas composition at La Solfatara, this third crisis convinced Italian Civil Protection authorities to raise Campi Flegrei’s alert status in 2012 from Green (normal) to Yellow (scientific attention). (Chiodini et al., 2015, 2016)

So, here’s how things stand with the major Neapolitan volcanoes right now:

  • Vesuvius: Ninth most deadly volcano in the world, per Oppenheimer, but alert status is green; possibly dormant; at any rate, with no signs of worrisome activity since 1944. Latest updates (Italian).
  • Campi Flegrei: Quiet since 1538 but restless; alert status is yellow. It might be warming up, but no one knows for sure what will happen, or when (Chiodini et al, 2015; Klemetti). Some are concerned about increased risk of an eruption during the 21st century. (Bellucci et al., 2006b) A recent probability study suggested that the most likely eruption size would be a VEI 3; next most likely, either VEI 2 (Monte Nuovo sized) or VEI 5 (maximum expected scenario). (Mastrolorenzo et al., 2006, 2015) VEI 5 is a plinian eruption (rare at Campi Flegrei), not a supereruption (VEI 8); for comparison, most estimates of the Campanian Ignimbrite eruption put it at VEI 7, and the Neapolitan Yellow Tuff eruption at VEI 6 (10 times bigger than a VEI 5). Latest Campi Flegrei updates (Italian).
  • Ischia: Alert status green; seismic monitoring in real time from Naples. Earthquakes here are not from magma movements, per De Novellis. Latest updates (Italian).

So, with that background in mind, how would you go about protecting the 6 million Campanians who live and work alongside these volcanoes?

At Vesuvius, Italian authorities first set up hazard zones in 1995. These are based on events during the volcano’s deadly 1631 subplinian eruption.

There are many details, of course, but here’s the basic zone setup:

  • Red: This includes the volcano itself as well as neighboring areas that are vulnerable to pyroclastic flows (Red Zone 1) and totally destructive mudflows and/or heavy tephra fall (Red Zone 2).

    MalKo via Wikimedia, CC BY-SA 4.0.

    Up to 1 million people are directly threatened by these hazards. (Tardini et al.) Since no one knows exactly where the next vent will open up, the entire zone must be evacuated before an eruption begins; plans are to settle everyone temporarily outside Campania.
  • Yellow: Mudflows and tephra fall thick enough to collapse roofs and cause other infrastructure damage (with associated injuries and deaths) is the hazard of concern here. Because predominant winds here are from the west, this zone is located mostly east of Vesuvius.

    Italy’s Civil Protection

    Per Scarth, over a million people live here in the provinces of Naples (not including the city, which is to the west), Avellino, Benevento, and Salerno. Since they’re farther from the volcano, they will be evacuated after an eruption begins and head to shelters in safer parts of Campania.

  • Blue: In May 1998, heavy rains led to debris flows of volcanoclastic material that devastated this region, comprising the Nola plain northeast of Vesuvius. Bad flooding from condensed steam and rain also happened here during the 1631 eruption. About 180,000 people will need to be evacuated. (Rolandi; Scarth)

There are cogent criticisms of the Vesuvius plan, the main one being that authorities should plan for a bigger eruption, just in case, like the plinian Pompeii eruption in 79 AD or the Avellino eruption around 1780 BC.

Other criticisms include the fact that detailed evacuation plans are based on a time window and expected precursors that no one can be sure will actually happen.

Also, the city of Naples is in serious trouble if the wind happens to be blowing from the east on Eruption Day. It’s not currently in the Yellow Zone.

Still, Italy has a plan for Vesuvius and it’s official, which is more than you can say for the only Neapolitan volcano that’s currently at an elevated alert level.

Campi Flegrei presents more problems for planners, though.

That mysterious bradyseism, which volcanologists must understand fully if they are going to accurately forecast Campi Flegrei’s behavior, is only one of the complications.


As you might expect from looking at it, this volcano’s eruptive history is amazingly diverse. No one can say for sure what form the next spasm of activity will take.

Eruptions here have included everything from relatively small steam explosions, like the one that excavated what is now Lake Averno, to the plain-burying Campanian Ignimbrite ash hurricane (if you don’t subscribe to the hypothesis that this caldera was only a peripheral vent for that 39,000-year-old eruption).

And they have occurred just about everywhere in the almost circular caldera that formed after the Neapolitan Yellow Tuff eruption.

Lava, pyroclastic flows, and tephra fall (ash, stones of various sizes, and big blocks of rock/blobs of lava) are the main hazards at any eruption.

Fortunately, lava from subduction zone volcanoes like Campi Flegrei and Vesuvius doesn’t flow as far as it does in Hawaii, since it contains more silica and more water and is therefore very “sticky.”

While the 1944 eruption showed how readily lava travelled down the steep slopes of Vesuvius, flows in Campi Flegrei’s pock-marked landscape will probably not leave the caldera. (Mastrolorenzo and others, 2006)

That’s good news. But such “sticky” lava also is explosive, and that means pyroclastic flows.

There’s a little more good news. The caldera’s eastern rim (the hills that stand between Pozzuoli and Naples), as well as its northern wall, could probably contain flows from anything up to and including a VEI 4 eruption. (Mastrolorenzo et al., 2006, 2017)

That’s why Campi Flegrei’s proposed Red Zone is basically the caldera. This area, home to about 1.8 million people (Freire et al.), would need to be evacuated before an eruption.

The proposed Yellow Zone includes the City of Naples and other points downwind of Campi Flegrei. Here, tephra fall that can wreck the infrastructure is the main problem.

Italys Civil Protection

Are you having difficulty wrapping your mind about trying to evacuate the millions in that yellow zone — which includes downtown Naples — on roads that weren’t designed to handle such traffic, after an eruption has begun in the Red Zone? Me, too. (The blue line marks the outer limits of the expected area of strongest ash fall in the modeled eruption.)

Still, it’s a plan. But it’s not yet in place, as far as I can tell, though it appears from online sources to have a lot of official backing.

There are two major problems with it. The first — false alarms — is also present at Vesuvius. People in the Red Zone will get some. It’s unavoidable.

The need to evacuate people before an eruption begins is obvious. Things happen fast, as this amazing footage captured by Photovolcania at the Santiaguito Volcano Complex in Latin America shows:

But there will be false alarms, perhaps several of them as rising magma stalls and then restarts its journey to the surface.

Already tens of thousands of Pozzuoli residents can testify about the upheaval and hardships just one false-alarm evacuation can cause.

When it involves the evacuation of 1 to 2 million people, resulting social, economic, and political reactions from a false alarm are going to be much more severe. At the very least, careers will be ruined; it could even have national repercussions.

Just one false alarm.

Yet who would want to gamble with so many lives when the monitors clearly point to an impending eruption (of unpredictable size/characteristics/energy)?

Another problem with false alarms is that people who have been through one then ignore future warnings and are caught when the volcano does erupt.

And in Campania, a long human history of conquest, political turmoil, autocracy, plutocracy, bureaucracy, poverty, and crime has conditioned people to challenge authority and to doubt all official announcements and actions.

Will the plan work?

Short answer: “In theory, the theory will work,” Scarth writes, but human nature cannot be reliably modeled. No one will ever really know how effective the plans are until the eruption comes.

Details: Those poor 16th-century Pozzuolians, forced to go back to ruined homes and rebuild their lives next to the still smoking Monte Nuovo cone that had just killed tens of people and buried the neighboring town!

That’s the sort of heavy-handed authoritarian treatment Campanians had to put up with back in the day.

But the viceroy did cancel their taxes, reducing his own income (and, to his credit, he also built a home in Pozzuoli after the eruption and lived in it).

He knew the balancing point of power between Campanians and their rulers, and he was careful not to upset it and cause a revolution.

Whole libraries could probably be filled with books about the cat-and-mouse games between the people who live on the Italian Peninsula and their governments down through the centuries.

For those who must live with Vesuvius, Campi Flegrei, and Ischia, all this, of course, is a very personal part of local and family history. It affects their attitude toward official emergency plans in many ways.

All Neapolitans know about San Gennaro (Saint Januarius), too.

Religion is relevant in Campania, not because it’s Italy, but because people here have been using faith to deal with volcanoes for millennia.

That’s a span of time that at least gives humanity a wee bit of footing on the geologic scale.

Gennaro was an early Christian bishop who was martyred near La Solfatara in the early 300s. His head, some of his blood, and a few other relics were saved by faithful followers, who soon began to report miracles from them.

In early November 472, Vesuvius was in the throes of a VEI 5 eruption and mudflows were pouring into Naples.

Neapolitans who had taken refuge in catacombs called on San Gennaro for help — the ash reportedly stopped falling and daylight returned to the area.

San Gennaro was now officially the protector of Naples!

His relics reportedly tamed other eruptions, including the 1631 event that today’s emergency plans are based upon as well as the Monte Nuovo eruption, which happened near the site of the saint’s martrydom a thousand years earlier.

San Gennaro was called on during the 1906 eruption, too.

Other local saints are invoked as needed — the image of San Sebastiano, for example, was carried through the town named after him as lava from the 1944 eruption rolled in and demolished buildings — but San Gennaro is always available as backup, so to speak.

Even now, the saint’s preserved blood is displayed in church on certain days, and its vial gently rocked back and forth by hand. If the blood liquefies (it usually does), Naples can expect to enjoy continued protection.

When the age of science dawned, more secular heroes appeared for Neapolitans to put their trust in, including early directors of the Vesuvius Observatory like Luigi Palmieri and Raffaele Matteucci (link is in Italian).

For most of us, dealing with the local volcano is not a zero-sum situation. You’re going to rely on government officials as much as possible but also keep options open on saints and scientists.

All three could prove helpful, if and when the Day of Fire comes.

Volcanic hazard managers expect religious processions as part of the social reaction in Naples to the next bout of activity at Campi Flegrei or Vesuvius (these two apparently don’t erupt in unison).

But Neapolitans are also 21st-century urbanites. They’re known for their hustle and excellent survival instincts in the face of problems ranging from insane traffic conditions to the city’s “parallel government” by organized crime.

And they fill out questionnaires, just like everybody else.

In 2008, Barberi et al. reported on the results of a survey of Red Zone residents around Vesuvius.

Despite creeping urbanization, usually unauthorized, up the volcano’s flanks, everyone knew that Vesuvius was dangerous. They just were more focused on day-to-day problems like public services, crime, pollution, traffic, and unemployment.

Over half of the respondents admitted not being familiar with the evacuation plan, but 63% said they had little to no confidence in it.

That’s cynicism in action!

About half of the people who returned the survey had no idea where they were supposed to go in an emergency, and almost everybody doubted their ability to personally take steps needed to survive a volcano emergency.

Another 2008 survey of 400 high school students who live near Vesuvius found the same lack of self-confidence.

Just as speculation, this might be an artifact on modern global culture, which encourages passivity in consumers to some extent. During an actual eruption, adrenaline and tens of thousands of years of built-in instinct would probably take over quickly, saving many individual lives no matter how the plan itself performed in action.

One can hope so, anyway.

But what about Campania?

Lately, archaeologists and anthropologists have been working with volcanologists to get more information out of the geological record on how human society has coped with volcanoes down through the millennia.

It’s not easy, and the data often can be interpreted in different ways. Some insights are developing, though.

  • Vulnerability to short-term impacts. Campania’s highly urbanized setting makes it very susceptible to eruption effects lasting from days to a few years.
  • The ability to withstand an eruption without social and physical collapse. Campanians massively outnumber their volcanoes, and they have complex social and physical networks, too. Volcanic hazards can’t be everywhere at once unless it’s another Campanian Ignimbrite or, perhaps, Neapolitan Yellow Tuff scenario. While local parts suffer, the rest of the region’s vital infrastructure, perhaps most of it, will remain intact. And Campanians, in their daily lives as well as through their history, have already demonstrated remarkable human resilience. They’ll make it through whatever Vesuvius, Campi Flegrei, or Ischia throw at them.
  • Adaptation. Down through the centuries, war, political instability, and economic problems have forced residents of this region to make the best of altered circumstances, just as an eruption would. Perhaps Italians generally have an advantage in this respect over some other societies.

In a study of the human consequences of the Bronze Age Avellino Pumice eruption at Vesuvius, Torrence noted that most societies do get themselves back together after an eruption has flattened them.

They re-form and move forward on the same paths followed before the catastrophe. However, adaptation and innovation often eventually move the society in a new direction.

It’s the same human story that has played out in many ways over geological amounts of time, not always in ways connected to volcanoes.

We may some day witness something like this happen in Campania. I hope not. It will be heartbreaking to watch, let alone experience.

But it will also be a sublime example of what people can and do survive. After much suffering, and at great cost, they eventually prosper again and carry humanity forward into an unknowable future.

Featured image: Church officials displaying the blood of San Gennaro on his holiday. Paola Magni, CC BY 2.0

Sources: All of those listed for earlier posts in this series, plus:

Barberi, F.; Davis, M. S.; Isaia, R.; Nave, R.; and Ricci, T. 2008. Volcanic risk perception in the Vesuvius population. Journal of Volcanology and Geothermal Research, 172(3-4): 244-258.

Carlino, S.; Somma, R.; and Mayberry, G. C. 2008. Volcanic risk perception of young people in the urban areas of Vesuvius: Comparisons with other volcanic areas and implications for emergency management. Journal of Volcanology and Geothermal Research, 172(3-4): 229-243.

Chester, D.; Duncan, A.; Kilburn, C.; Sangster, H.; and Solana, C. 2015. Human responses to the 1906 eruption of Vesuvius, southern Italy. Journal of Volcanology and Geothermal Research, 296: 1-18.

Chiodini, G.; Vandemeulebrouck, J.; Caliro, S.; D’Auria, L.; and others. 2015. Evidence of thermal-driven processes triggering the 2005–2014 unrest at Campi Flegrei caldera. Earth and Planetary Science Letters, 414: 58-67.

Chiodini, G.; Paonita, A.; Aiuppa, A.; Costa, A.; and others. 2016. Magmas near the critical degassing pressure drive volcanic unrest towards a critical state. Nature Communications, 7: 13712.

Mastrolorenzo, G.; Palladino, D. M.; Pappalardo, L.; and Rossano, S. 2017. Probabilistic-numerical assessment of pyroclastic current hazard at Campi Flegrei and Naples city: Multi-VEI scenarios as a tool for “full-scale” risk management. PloS One, 12(10): e0185756.

Rolandi, G. 2010. Volcanic hazard at Vesuvius: An analysis for the revision of the current emergency plan. Journal of Volcanology and Geothermal Research, 189(3-4): 347-362.

Tadini, A.; Bevilacqua, A.; Neri, A.; Cioni, R.; and others. 2017. Assessing future vent opening locations at the Somma‐Vesuvio volcanic complex: 2. Probability maps of the caldera for a future Plinian/sub‐Plinian event with uncertainty quantification. Journal of Geophysical Research: Solid Earth, 122(6): 4357-4376.


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