The Gulf of Naples - One of the most dangerous places in the world | DW Documentary
The Gulf of Naples on the west coast of Italy — a breathtakingly beautiful bay. But the tranquility here is deceptive. This is one of the most dangerous places on the planet. The Naples region is dominated by volcanoes, such as Vesuvius. In ancient times, it was the cause of a massive natural catastrophe that left thousands of people dead. The volcano’s direct neighbors...
some four million people living in the Naples metropolitan area. Today, Vesuvius appears quiet. But the volcano could erupt again at any moment. We don’t know when, or how strong it’ll be, but we do know for certain that it will happen.
The city is exposed to further threats: a gigantic network of dangerous, almost invisible volcanoes. Any eruption would have devastating consequences. Volcanologists and researchers are in a race against time.
Using up-to-the-minute technology, they analyze any variation that could signal an imminent eruption. Can they stay a step ahead of the volcano? Vesuvius — one of history’s most notorious volcanoes. In the year 79 AD, its destructive flames engulfed the city of Pompeii and killed its inhabitants. Further eruptions followed. But today, Vesuvius is not the most potent threat.
20 kilometers to the west lies an even greater danger. Beneath this expanse of lowland is a group of developing volcanoes: historically named the Phlegraean Fields, or ‘the burning fields’. There are more than 50 of them across 150 square kilometers, on land and under the sea. On the surface, they’re almost invisible. This network is classified as a “super volcano” — the only one in Europe.
An eruption would be devastating. So far, scientists have discovered around 20 such super volcanoes worldwide. And there are signs that this one could erupt soon. Volcanologists are especially interested in the intense activity in the Solfatara crater.
Every day, more than two thousand five hundred tons of CO2 and sulfur are released here from the depths of the earth. In the year 2017, an entire family died after walking on the crater’s unstable surface. If you walk on the crater floor, you can actually feel the chasms, because the molten rock is porous, and chasms are created underneath by the emission of gases. Under concentrated high-pressure, the gases can erode the fine particles of the rock and create chasms below the crater level. Despite this permanent danger, thousands of people live on the edge of the Solfatara. On its northeastern flank is the Pisciarelli fumarole field.
A nearby tennis hotel was forced to close. Extremely hot and intense steam is being emitted, the temperature must be above 100 degrees, and these emissions are what’s producing all this salt. The emissions cover the walls and floors with a thick whitish coating and smell of sulfur.
A few years ago, the Pisciarelli fumarole was just a small hole. The thermic area now measures around four thousand eight hundred square meters and emits more than 600 tons of carbon dioxide every day. If, for example, there’s an increase in one component compared to another, this could mean that magma is moving towards the surface. So, any variations will give us an indication about how the system is evolving and whether an eruption is imminent.
After detailed analysis, the scientists come to a conclusion: the Phlegraean Fields could potentially erupt very soon. Around forty thousand years ago, a volcanic eruption from this very same site, laid waste to a large area of Europe. What’s known as the Campanian Ignimbrite eruption spewed more than 300 cubic kilometers of magma. A second eruption 15 thousand years ago ejected a particular kind of volcanic rock, Neapolitan Yellow Tuff.
To this day, the stone is a defining feature of the city of Naples. Here, we have some splendid examples. The Gesù Nuovo church is composed of fragments, blocks of stone extracted from the Campanian Ignimbrite, whereas behind me is the Santa Chiara church, which you can see is entirely built from blocks of Neapolitan Yellow Tuff. To some extent, you could say that, thanks to the extraction of this material from beneath the city, the outline of Naples is the positive image of a negative. One structure in particular highlights the ingenuity of the Romans. A cistern built using volcanic rock.
We’re in a huge fresh-water reservoir, it’s an impressive technological feat: the pillars are fifteen meters tall. The reservoir contained 12 million liters of water. This enormous ancient cistern was dug entirely out of a tuff hill. But Neapolitan Yellow Tuff does have one major drawback: it’s porous. In order to water-proof the walls, they had a clever idea: they made a special kind of mortar.
It’s a cement-based mortar, called cocciopesto. It’s basically made of three elements: brick fragments, limestone, and the most important element - pouzzolane — volcanic ash, of which is there is an abundance in this area. They mixed these three things together, and once set, it made the walls totally waterproof. This then enabled the reservoir to contain huge quantities of water.
Today, the Phlegraean Fields threaten to destroy what the Neapolitans have built over centuries. All the while, Naples’ most famous volcano looms ominously over the city. Vesuvius has maintained a brooding and highly visible presence for centuries. Its last eruption in 1944 was devastating. The lava flows destroyed entire villages. 26 people died. Vesuvius has been dormant ever since.
But volcanologists continue to monitor it, just as they’ve been doing since the 19th century. For us Neapolitans, Vesuvius is the ultimate volcano. It has dominated our culture, and I’ve always been strongly attracted to it. And for those of us who work a lot in this domain, it’s important to note that we find out something new about it every day.
Mauro di Vito studies the stratigraphy — the geological layers of the volcano. When volcanologists study stratigraphy, it’s as if we’re reading a written account, turning page after page of the history of the volcano’s eruptions. Vesuvius remains dangerous to this day. More than 700 earthquakes occur here every year. Some seven hundred thousand people live in close proximity to the volcano.
Scientists register every tremor and change. This instrument measures the flow of CO2 and the temperature of the gas emissions. It also enables us to have a more general idea about the evolution of the volcano. It’s very important to understand the system, because it can give us an indication about the possible movements of magmatic currents. This is one instrument, among many others, which enables us to listen to the volcano’s breathing. The volcano’s “breath” is the gases dissolved in the magma.
When they rise to the surface of the crater, the pressure drops and the gases expand. They form bubbles which spread over the surface. It’s a bit like what happens in this bottle which contains a gas-rich liquid: as soon as you alter the pressure, by removing the cap, you can see the gas separating from the liquid and rising to the surface. A look back at the history of Earth reveals more about the origin of volcanoes and magma. 250 million years ago there was a huge land mass called the Pangaea.
Geological activity broke up this super-continent into several tectonic plates. These separated and drifted apart to form today’s continents. The geological trigger for these movements can be found beneath the Earth’s crust. This layer is around 30 kilometers thick, nothing compared to the radius of the planet, which is around six thousand kilometers. Between this crust and the Earth’s core, there’s an upper mantle around 650 kilometers deep.
This mantle consists of currents of molten rocks circulating around each other. They act like a conveyor belt displacing the plates of the Earth’s crust: this is called convective movement. For millions of years, these plates have been drifting apart by several centimeters per year. They slide, separate and collide. In Italy, the African plate slides under the Eurasian plate.
The contact points can reach such high temperatures that part of the mantle’s rock fuses: bringing about what’s known as subduction. The molten rock, or magma, builds up in the crevices of the Earth’s crust, and forms magma chambers. Eventually, magma combined with gas will rise to the surface and form a volcano. To balance the structure of the Earth’s crust, surplus heat and energy is discharged and magma ejected — triggering a volcanic eruption. One of the world’s most active volcanoes is located around 600 kilometers south of Naples. Mount Etna in Sicily.
This volcano, which is more than three thousand meters above sea level, is nicknamed Mongibello, or the mountain of mountains. In contrast to the Neapolitan volcanoes, Etna erupts on a regular basis. Almost 80 times during the last century, in fact.
Eugenio Privitera has been analyzing it for many years. We can find all these lapilli, which is debris from explosions. The pieces are small and very light: this is because they’re full of air bubbles, or originally, gas. We can also find volcanic ash, and as you can see, it’s like very fine, black sand. And here is a lovely volcanic bomb.
It’s quite big, but not as big as some produced by Etna. Some bombs can be the size of small cars. This rock was produced from within a magma column, and when the gas bubbles reach the surface and expand, they project into the air the part of the magma situated above the gas bubble. Etna is constantly creating new craters. Bocca Nuova is the youngest of the four craters on the summit. It appeared in 1968 to the west of the central crater cone.
Unlike the volcanoes of the Bay of Naples, Etna is situated at the crossroads of several tectonic plates. It’s in contact not only with the Eurasian and African plates, also with the micro-plates of the Tyrrhenian and Ionian seas. These geological confrontations produce huge quantities of magma, which in turn generate intense activity.
The magma is relatively fluid and the gas bubbles move freely. Therefore, they rise to the surface quicker than the magmatic fluid. In contrast, the magma within Vesuvius and the Phlegraean Fields is much more viscous. This means it’s harder for the gas bubbles to escape, causing a build-up of pressure. This could generate explosive eruptions with huge destructive power. The prevailing theory to date has been that in the case of Mount Etna, small gas bubbles merge to make larger ones.
These rise in the vents faster than the magmatic fluid. When they reach the surface, they burst, creating mini-explosions that project the magma into the air. Once separated from the gas, the magma spreads and forms relatively slow lava flows, known as effusive eruptions. But volcanologists are unsettled by some of the latest findings: One of the most recent discoveries we made about Etna, is that the chemical composition of the magma has been changing over the last few decades. There is now an increase in potassium, compared to before when there was more sodium.
This chemical variation could explain the rise in explosive activity that we’ve noticed over the last few years, and the fall in effusive activity. So, how is it today? Hi Eugenio, I’m in the middle of checking the signals, but for the moment, I can’t see any significant variations. Despite its huge surface area of around one thousand two hundred square kilometers, Etna is one of the most monitored volcanos in the world.
Researchers track its activity in numerous laboratories. The tiniest variations could be precursors of an imminent eruption. And there’s another danger lurking not far away. Several kilometers north of Etna, in the Mediterranean, is Europe’s largest active volcano. The underwater volcano Marsili is situated at a depth of around three thousand five hundred meters.
There’s another underwater volcano near the Aeolian Island chain, off the island of Panarea. Francesco Italiano and his team have been observing it since it was discovered in 2002. Arnaldo, can you see? Look, you can really see the bubbles that are rising to the surface. These are the most intense hydrothermal emissions that we’ve seen here in Panarea. It’s all carbon dioxide and a lot of hydrogen sulfide, you can smell the sulfur in the air.
That’s the first thing we noticed, when we came to study Panarea. What we didn’t expect at the time, was that under the sea there was a whole world we couldn’t see from above. This underwater volcano has actually been extinguished for millennia. It was a huge surprise to discover that the fluids were rising to the surface in chimneys, three to four meters high. It was such a surprise, because it meant that the fluids were finding their way upwards through these ancient structures, all fed by a volcano.
So we deduced that there was a major hydrothermal system that we needed to take a closer look at. Over the centuries, these fluids forged more than 200 chimneys. They consist of iron oxide and have a red-orange color.
This mineral forest is only 70 meters below the surface, which makes it an exceptional observation site for scientists. Elsewhere in the world, this type of geological formation is only found at much greater ocean depths. It was here that Francesco Italiano made an extraordinary discovery. These are grains from iron oxide shells, which form around each other, creating what we call ‘ooids.’ It’s the same type of deposit that has been photographed on Mars.
We know that on Earth, the origin of life is linked to hydrothermal systems, in which life-forms use chemical elements to survive. Seeing that we have the same underwater hydrothermal system on Mars could mean that there are forms of life on the red planet, too. The submarine volcano of Panarea is now a giant laboratory.
And scientists are only just beginning their investigation. In the Tyrrhenian Sea, the volcanoes are anything but quiet. Across the water from the island of Panarea there’s another volcano feared by humans for centuries: the Stromboli. It’s one of the most active volcanoes on the planet. It spews its incandescent lava day and night, earning the nickname ‘lighthouse of the Mediterranean.’ At 926 meters high, it’s classified as a stratovolcano — built up by many layers of hardened lava.
Volcanologists explore the northern flank of the island, the Sciara del Fuoco - the stream of fire. It’s a horseshoe-shaped depression with a highly unstable 36-degree slope. In December 2002, the stream of fire was the scene of a spectacular event. 20 million cubic meters of rock crashed into the sea, triggering a tsunami with waves of up to 10 meters high.
Scientists now know what caused this dramatic event: as magma rose to the surface it warped this section of the volcano, which began to swell. The rock began to crack in numerous places, triggering the landslide ... which in turn brought on a tidal wave.
Volcanologist Mauro Rosi and his team have developed a new technology to bring this unstable flank under control. What’s the radar reading? All is stable on the Sciara. Thanks to this high-resolution radar, the scientists can now track the slightest movements in the ground 24 hours a day.
To produce images of the movements of the Sciara del Fuoco, the machine works like a photocopier. If there have been any shifts of land, these will be picked up by comparing two images and it could mean that there’s a risk of the Sciara del Fuoco collapsing. The 2002 tsunami reminds Mauro Rosi of a terrible event that took place in the 14th century, as described by the Italian writer, Petrarch. There was a huge tremor in Naples, a loud noise during the night which woke everyone up. In the morning, down at the port, corpses and wounded people were scattered in the water. He wrote: ‘broken like soft eggs, floating on the water.’
When the theory was put forward that Iddu could have been the cause of this deadly tsunami, that’s when I decided to come to Stromboli, to look for evidence that a tidal wave had indeed taken place at that precise time. On the island of Stromboli, the volcanologist found traces of this disaster buried one meter underground. We found this brown coloured volcanic material. The most interesting part is this sand layer. It contains round pebbles and is irrefutable proof that it was indeed created by a tsunami. By measuring the radiocarbon in the underlying layer, we were able to date it to the mid-14th century.
The age coincides with the tsunami observed by Petrarch in Naples. By measuring the thickness of this layer and its distribution across the island, Mauro Rosi was able to prove that the tidal wave reached a height of over 20 meters. In 2019, tourists were nearly drowned by a similar wave. Since then, the whole island has been under a permanent tsunami alert.
Mauro is convinced that we might very well see a repeat of the deadly tidal wave that hit Naples in the 14th century. If another tsunami was formed because of a landslide on the Sciara del Fuoco, the resulting wave would travel northwards and reach the port of Naples in about twenty minutes. It wouldn’t take long for the port of Naples and the surrounding area to be completely destroyed by a giant wave. Another potential threat for the region. Given the threat of the Phlegraean Fields, Vesuvius, Etna, the undersea volcano of Panarea and Stromboli, some four million inhabitants of the Gulf of Naples have had to learn to live with omnipresent danger.
The catastrophe that devastated the city of Pompeii two thousand years ago shows what an eruption might do. In August of the year 79 AD, Pompeii, a city thirty kilometers south of Naples, was consumed by ash. Vesuvius had been dormant for 800 years. But that night, the volcano came to life. Today, after many centuries of excavation, the remains of Pompeii are a unique treasure trove for scientists. This exceptional archaeological site has enabled Claudio Scarpati to conduct a detailed examination of the evolution of the eruption and its destructive impact on the human population. What we can see here, is the whole sequence of events that occurred in 79 AD. There are two main layers —
a lower layer which is made up of pumice, with stones of different sizes, then there’s a clear separation, and the upper stratum is composed of layers of ash. These are the two main phases of the eruption. These observations have enabled scientists to partially reconstruct the first phase of the eruption. A massive column, from deep inside the volcano, rose at an average speed of 400 meters per second. It contained millions of tons of ash and pumice. The energy released was one hundred thousand times greater than that of the Hiroshima bomb.
According to the scientists’ calculations, the eruption ejected around four cubic kilometers of stone and lava. The plume of smoke reached 32 kilometers into the sky. That’s almost 30 times higher than Vesuvius itself. At this altitude, the column assumed the form of a pine tree.
Witnessed by the writer Pliny, this kind of eruption is now known as a Plinian eruption. Pumice and ash then rained down on Pompeii. People had no time to flee and were buried in an instant.
The corpses eventually decomposed leaving a hollow imprint in the compacted ash. Scientists later filled the cavities with plaster. These plaster casts of the people of Pompeii show their desperate attempts to escape the deadly ash. You can see the expression on the face and the position of the body. This is vitally important, because it allows us to capture the person’s last moments, and to understand what actually caused their death. After 19 hours of this devastating ash rain, the eruption entered its second, even more deadly phase.
As the gas pressure dropped, the 32-kilometer plume of smoke imploded. This triggered an avalanche of fire — called pyroclastic flows — traveling down the sides of the volcano at hundreds of kilometers an hour. In the ruins of this Roman villa, archaeologists discovered victims from the second phase of the eruption. One person seemed to be desperately trying to protect another by putting an arm around them. These victims found themselves inside a cloud, which was probably dozens, if not hundreds of meters thick. A cloud of ash, pumice, and volcanic gases, probably reaching temperatures of 100 degrees.
They were undoubtedly suffocated by the density of the ash, which was found in the pyroclastic flows, and they would have died within minutes. Claudio Scarpati’s scientific approach is to examine the remains of the past in order to anticipate the future. And he’s not the only scientist to ask the worrying question: could Naples ever become another Pompeii? What’s interesting is that generations born after the last eruption in 1944 have never seen the volcano erupt, they’ve never seen the famous plume of smoke above Vesuvius, and so they see a volcano which is calm, dormant and that doesn’t need to be feared.
But on the contrary, it’s a very active volcano, which could erupt intensely at any time. We don’t know when, or with how much force, but we know for certain that it will happen. In the Bay of Naples, the highest priority remains the surveillance of the Phlegraean Fields. After sunset, scientists begin their monitoring work. They’re looking for the slightest tremors — changes that could affect the lives of millions. Tonight, Enrica Marotta and her assistant are observing the Pisciarelli fumarole with a thermal camera.
It’s vital that the sun’s rays don’t influence the temperature of the magmatic chamber, so that’s why we work at night. At the moment, we can see the maximum temperature is 85 degrees. If we move the camera and focus on the fumarole zone, we can see that there’s a huge amount of energy, and considerable gas emissions, something which wasn’t happening ten years ago.
It’s impossible to go there now, so that’s why we use drones. This drone can fly up to an altitude of 100 meters and cover the entire Pisciarelli area. Which is growing rapidly. Here, for example, we have a surface area of around a kilometer. We can see straight away which are the zones with the greatest thermal anomalies. Over time, we can work out if these abnormal zones are rising or falling in temperature. This then gives us an idea of the situation of the magmatic system.
Enrica now repeats these procedures every month, as the signs of volcanic activity become more concerning. But eruptions aren’t the only dangers linked to volcanoes. The town of Pozzuoli is located close to the Pisciarelli fumarole. A very rare geological event occurred here in the 1980s: known as bradyseism. Bradyseism means that the ground rises and falls very slowly. When magmatic fluids in flat layers of rock rise, the rock is warped and lifted upwards. This deformation creates cracks.
If these reach the surface, they can cause earthquakes. The heat from the magma can then escape through the fumaroles. When the magmatic fluids subside, the rock is warped in the opposite direction and the ground collapses...Almost as though the volcano is breathing. Volcanologist Mauro di Vito believes the situation has become even more dangerous since the 1980s. A very slow uplift began in 2006, stage by stage, accompanied by seismic activity, and then from 2018, the rhythm has been more or less constant, with an important increase which is still going on today. The total deformation from 2006 to the present day is around 70 centimeters in the central zone of Pozzuoli.
This is certainly one of the reasons that I’m worried, but I can’t give it a timescale: we can’t know or say if the next eruption will take place tomorrow, in six months or in twenty years. Scientists believe that if an eruption did take place, it could look like this. An eruptive column around 15 to 20 kilometers high, ejecting huge plumes of magma and tons of ashes, which the wind would carry to Naples and beyond.
It’s estimated that there would be just 30 minutes to evacuate the four million people living nearby. At the Pozzuoli Civil Protection Centre, security teams are on maximum alert. In the event of an eruption of the Phlegraean Fields, this is the area facing the greatest threat. Thank you everyone for your assessment of the situation.
The Stromboli volcanologist Mauro Rosi is also responsible for monitoring operations in the region. Every two months, he meets civil protection professionals and volunteers to plan for the potential evacuation of thousands of people. Obviously, if the conditions were such that we had to pass to a level orange alert, the evacuation plan for the whole of the Phlegraean zone could happen in two ways: either autonomously, using their own vehicles, or by assisted evacuation for those physically incapable of leaving on their own. Although everything’s ready on paper, so far the plans haven’t been put to the test in towns with winding, frequently congested streets. This isn’t simply a logistical problem.
Despite the ever-present danger, locals feel a deep sense of attachment to their land. I’d prefer to die here, where I was born and where all my ancestors were born, because I’m an old Puteolano, it’s in my blood. It’s not something you can explain. You’re born, you live and you die here. What the scientists say is both true and worrying, but we’re staying here and what will be, will be. Humans have always lived here, alongside the volcanoes.
The burning mountains are an integral part of their culture. If an eruption does one day appear imminent, scientists want to be able to issue a timely warning. In the Panarea region with its active underwater volcano, they’ve made an unexpected discovery. We’re on the fault line. This time, biologists are exploring the area. Simone, can you see where we are? We should be there, shouldn’t we? Yes, this is the chimney zone we saw in 2015.
To better understand this zone with 200 chimneys, scientists are using a remote-controlled underwater vehicle or ROV. It’s equipped with a high-definition camera and an articulated arm which can be operated from the ship. The device enables unprecedented exploration of the hydrothermal vents. These are the chimneys that we discovered five years ago.
What’s striking, is all the living creatures surrounding them. Because around the chimneys, there are fairly extreme conditions, for example a very acidic pH level, and CO2 emissions, which are higher than in other zones. The entire area is full of life, and so it seems organisms have adapted to their environment. It’s an astonishing ecosystem. In such extreme conditions with high gas levels, life ought not to be viable. The biologists explain this by the presence of bacteria which feed on the minerals produced by the gas.
By transforming them into energy, the bacteria sustain the whole area. A clear sign that in a volcanic environment where explosions can be deadly, new life can emerge again. One of the scientists’ primary goals is to continue research into this paradox of nature. The Bay of Naples: an area of volcanic turbulence where the end of one world could mean the beginning of another....