The Mediterranean: FIRE BENEATH THE SEA

We are here for deep dives at a unique site called ‘THE VALLEY OF 200 VOLCANOES’.

The night is beautiful and so is the sea. The air on the other hand is cold, despite an early start to spring, which is a warning of hot weather to come. That’s just how it is, the seasons are always a little late at sea. The paradox of water – changeable and restless, yet slow to warm up. The Victoria is slowly gliding south-wards. For once, I am at the helm. This is the first and last time I will be relieving our captain. Once the mission has started, the deep divers will, as usual, be exempted from the night watch in order to get a good night’s sleep between the long and tiring immersions.

I could easily follow my course by observing the sophisticated instruments on the bridge, let the autopilot do its thing, but how can I resist ancestral navigation guided by a small glowing light on the far-distant horizon? Known as the lighthouse of the Mediterranean, it is not the work of men, but rather that of the Earth’s fiery entrails: it is the crater of the Stromboli volcanic island in the Aeolian archipelago north of Sicily. While this flickering glow is barely perceptible from a distance, it has persisted for thousands of years.

We are due to meet up with Italian volcanologist Francesco Italiano. It was he who discovered – and then revealed to my diver friend Roberto Rinaldi – the existence of deep volcanic phenomena. After diving there once, Roberto in turn told me about this incredible place and the seeds were thus sown. Two years passed, the time required to put together a mission that made sense, i.e. that could be useful to local scientists and help them in their research. I have never really been satisfied with simply heading somewhere just to ‘go and see’. Our journey must serve to unlock some secrets, and so much the better if beautiful images ensue. The beauty of the world is definitely important, yet it is less fascinating than its mysteries.

We are in the middle of a pandemic. The last G7 summit was held by video conference. They are confident, or so they say, that the global economy will pick up again strongly once the vaccines are perfected. Nothing more is said – as if there were no other lessons to be learned from a small virus that is bringing the whole of human-kind to its knees. The heads of state are on remote, and we are at sea beneath the sky, on a Mediterranean empty of tourists. After four days of sailing and a stopover in Naples to pick up Roberto, we still haven’t seen a single yacht, barely any ferries and no cruisers. Gliding past the high cliffs of Capri and passing only a fisherman’s boat is more than a privilege – it is like a journey back in time. The surroundings of this limestone castle appear as they were a few centuries ago, devoid of visitors.

The Victoria on its way to Stromboli, the most active volcano in the Aeolian Islands that erupts regularly. Men and women live on its flanks, under the permanent threat of a lava flow, a fiery cloud or a tsunami. — The Victoria on its way to Stromboli, the most active volcano in the Aeolian Islands that erupts regularly. Men and women live on its flanks, under the permanent threat of a lava flow, a fiery cloud or a tsunami.

For now, we continue on our way, past the lights of Stromboli to which we will return later and arrive at Panarea. This island is a dormant volcano and its humming reminds us of this: bubbling up to the surface here and there are natural whirlpools giving off a sulphur-like smell. We cast anchor nearby and our first dives are in shallow yet acidic water! The bubbles rise as the rain falls. This upside-down storm is so corrosive that the Romans once used it as a cleaning station. They would deliberately anchor their ships above these curtains of bubbles so that the acidic gases would clean the hulls attacked by ‘aquatic vermin’: algae that slowed down navigation, as well as boring worms that ate the wood of the planks. Today, I can still see the effect of this acidity on biodiversity, as there are no calcareous organisms, shells or coral growing in the vicinity. A careless marine worm attempted the suicidal adventure of settling too close to the bubbles: its calcareous tube is already slowly dissolving. Elsewhere, meadows of Neptune grass display whitened, burnt leaves. Only the anaerobic bacteria, greedy for CO2 and sulphurous material, appear to flourish. They form a thick, immaculate felt covering on the rocky walls that undulates in time with the acidic caress of the ocean. After a few hours in this pungent atmosphere, it is with chapped cheeks and lips that we return to the Victoria. Even the chrome of the taps on our diving suits has oxidised.

This dive just below the surface was a test for our equipment and we thus move on without any material concerns. We are here for deep dives at a unique site called ‘The Valley of 200 Volcanoes’, a discovery made by Francesco Italiano during a mapping campaign. Along a slight depression measuring 100 metres long and 15 metres wide, thin, high chimneys appeared on the screen of his side-scan sonar more than 10 years ago. A line situated in a strangely perfect axis between Panarea and the Stromboli volcano, whose smoking summit can be seen in the distance.

On reaching the bottom, the depth gauge indicates -78 metres, but the scenery is reminiscent of an oceanic ridge located -3,000 metres down at the bottom of the Atlantic. A strange impression emanates from this forbidding place, as if the sea down here were suffocating from excess activity. It exhales, grumbles and spits. Gas and hot water escape from the top of the narrow chimneys formed by the crystallisation of ferrous and ferric matter that precipitates on contact with the deep cold water. The surrounding colours are Martian: red, ochre, yellow. While one chimney is being built, another seems to be dying out and a third is already collapsing. There is a great sense of precariousness here, but underwater life is like that – at once fragile and obstinate. A small flatworm, like a creeping fingerprint, slides incognito across the leaves of the udotea, a small pioneer algae covering the red slopes of the chimneys of a small forest, green with hope. This flatworm is quite daring: it ventures to the top of the spitting hydrothermal vents. It is hard to imagine what interest it might have in walking on iron oxides in acidic water loaded with carbon dioxide.

Here and there, acidic bubbles escape from the bottom of the sea around the island of Panarea. Nothing can live in contact with these acidic and sulphurous waters. Only anaerobic bacteria seem to flourish, forming a white felt covering that undulates on the walls caressed by the bubbles.

In Panarea, these natural jacuzzis are extremely corrosive. Located just a few metres below the surface, they have been known since antiquity. The Romans deliberately anchored their ships above these bubbles so that the acidic gases would clean the hulls attacked by ‘aquatic vermin’: a whole flora of algae that slowed down navigation, and a whole fauna of invertebrate borers that ate or dug into the wooden planks of their ships. — In Panarea, these natural jacuzzis are extremely corrosive. Located just a few metres below the surface, they have been known since antiquity. The Romans deliberately anchored their ships above these bubbles so that the acidic gases would clean the hulls attacked by ‘aquatic vermin’: a whole flora of algae that slowed down navigation, and a whole fauna of invertebrate borers that ate or dug into the wooden planks of their ships.

At a depth of 80 m lies ‘The Valley of 200 Volcanoes’, so named by the volcanologists who detected this site in 2006 during a multibeam sounder campaign. It is characterised by hydrothermal vents spitting out boiling water, CO2 bubbles and sulphurous gases. Their alignment creates a strangely perfect axis between nearby Panarea and Stromboli, which is much further away. Researchers do not see this as a mere coincidence, but rather as a phenomenon caused by emanations from a fault line linking the two islands. — At a depth of 80 m lies ‘The Valley of 200 Volcanoes’, so named by the volcanologists who detected this site in 2006 during a multibeam sounder campaign. It is characterised by hydrothermal vents spitting out boiling water, CO2 bubbles and sulphurous gases. Their alignment creates a strangely perfect axis between nearby Panarea and Stromboli, which is much further away. Researchers do not see this as a mere coincidence, but rather as a phenomenon caused by emanations from a fault line linking the two islands.

It is amid this same inhospitable environment that the pantopod wanders. A marine arthropod, its long legs converge towards a body which appears to be so small that it is almost inexistent. So tiny, in fact, that due to the lack of space in its abdomen, part of its digestive tract is located inside its legs. On closer inspection, we can make out its four periscope eyes at the top of a small head that lends a semblance of coherence to this improbable creature.

Contemplation gives way to observation. The time we have left is entirely devoted to the scientific protocols that Francesco has asked us to carry out. At each chimney, a thermometer is inserted into the small crater to take a sample of hot water and another of gas, before moving on to the next. There are 200 of them and we will only do about 20. We have been at the bottom for an hour already; three more are waiting for us on the way up for decompression. Our samples also have to decompress. As we ascend, the pressure of the water on the test tubes decreases. The gas inside is trapped at high pressure because it was drawn at almost 80 metres. Care must therefore be taken to purge the test tubes every 10 metres to prevent the glass from exploding. By analysing these samples, Francesco Italiano will soon demonstrate that there is a direct link between the three main volcanoes of the archipelago. Stromboli, Panarea and Etna thus appear to be linked to the same giant magma chamber.

Aboard the Victoria, our journey continues. We have followed the direction indicated by the line of The Valley of 200 Volcanoes, and here we are at the foot of the immense Stromboli. From its 900-metre summit, we hear the regular thud of the explosions and the light of the red lava sprays. We land on the island just below the village for a stopover. After the privilege of solitary navigation comes that of an ascent: no one has climbed to the top for two years. Our guide is delighted to inform us that the last part, near the crater and constantly reshaped by eruptions, has never yet been trodden.

Gombessa team divers Antonin Guilbert and Thibault Rauby are taking gas and freshwater samples from the active chimneys in The Valley of 200 Volcanoes. At a depth of 80 m, the divers only allow themselves one hour of work on the bottom, as this in turn will involve an ascent lasting more than three hours because of the mandatory decompression stops. The reddish-yellow colour of the chimneys is caused by the iron oxides, which crystallise upon contact with the cold water of the depths.

This red-tipped sea slug, Diaphorodoris papillata, is a nomad that roams the desert left after a lava flow or a fresh deposit of volcanic dust. The black rock is bare except for a few colonies of Bryozoans – pioneer invertebrates that recolonise the virgin rock. This slug will be their first predator... — This red-tipped sea slug, Diaphorodoris papillata, is a nomad that roams the desert left after a lava flow or a fresh deposit of volcanic dust. The black rock is bare except for a few colonies of Bryozoans – pioneer invertebrates that recolonise the virgin rock. This slug will be their first predator...

At a depth of 80 m, gas and boiling water escape from the top of the narrow chimneys. While one chimney is being built, another seems to be dying out and a third is already collapsing. There is a great sense of precariousness here, but underwater life is like that – at once fragile and obstinate. Rare pantopods wander here, a kind of pseudo-spider whose body appears to be so narrow that most of its vital organs are located inside its long legs. Elsewhere, one finds a small flatworm, like a creeping fingerprint, that slides incognito across the leaves of the udotea, a small pioneer algae covering the red slopes of the chimneys of a small forest, green with hope. This flatworm is quite daring: it ventures to the top of the spitting hydrothermal vents. It is hard to imagine what interest it might have in walking on iron oxides in acidic water loaded with carbon dioxide! — At a depth of 80 m, gas and boiling water escape from the top of the narrow chimneys. While one chimney is being built, another seems to be dying out and a third is already collapsing. There is a great sense of precariousness here, but underwater life is like that – at once fragile and obstinate. Rare pantopods wander here, a kind of pseudo-spider whose body appears to be so narrow that most of its vital organs are located inside its long legs. Elsewhere, one finds a small flatworm, like a creeping fingerprint, that slides incognito across the leaves of the udotea, a small pioneer algae covering the red slopes of the chimneys of a small forest, green with hope. This flatworm is quite daring: it ventures to the top of the spitting hydrothermal vents. It is hard to imagine what interest it might have in walking on iron oxides in acidic water loaded with carbon dioxide!

From the smoky heights, we take in the sights. On one side, there is the village set on fairly green slopes, dotted with a few vines as well as olive and fig trees; and on the other, the devastated slope. This is the Sciara (meaning ‘road of fire’ in Arabic), the vast black vertical and entirely mineral corridor through which lava flows, and from whence rocks and ashes pour tirelessly. It is easy to imagine that the pouring of matter is likewise incessant underwater and destroys everything in its path. Yet life underwater is more stubbornly resilient than on land. I am curious to see how the ecosystem restarts with each new landslide. The last one was four years ago. Following a tremor, a huge section of Stromboli – from 400 metres above sea level to 1,500 metres below – broke away from the island and slid into the abyss. Roberto has already dived there more than 30 years ago. He remembers a superb pinnacle of volcanic rock, like an upright needle towering 40 metres high. Will this majestic edifice, covered with marine life, still be there after all this time despite successive disasters?

The diving conditions are problematic and boats are forbidden to remain beneath the Sciara. An explosion is always possible and the fiery clouds that roll down the slope like an avalanche at 500°C burn everything in their path. A boat is not fast enough to escape if it is on the ‘road of fire’. Paradoxically, there is less danger underwater as there is no risk of being asphyxiated by burning gases. The decision has thus been taken to leave the boat close to the coast but far from the Sciara: that means we will slip into the water far from the dive site and begin by swimming about two kilometres along the coast just below the surface.

Once we arrive in the middle of the Sciara corridor, then, and only then, will the descent to the depths begin. With our thrusters, the trip to the tipping point will take us about 30 to 40 minutes, and then the descent to 80 metres, barely one more.

There is no need to calculate the distance travelled. The scenery has just changed abruptly. The fields of cystoseira – bushes of yellow algae brimming with hidden fauna – come to a sudden halt. The transition is brutal and now there is only black sand and jagged stones. The descent begins. Everything is devastated. I can sense that Roberto has not yet found his bearings from his dive 30 years ago. That is hardly surprising, since the seabed here is remodelled with each new eruption. You might think you were on a barren planet if the silhouette of an anglerfish didn’t appear amid the anthracite dust raised by our fins. Underwater Nature is even less fond of emptiness than its terrestrial counterpart. On closer inspection, a whole series of pioneering species – tiny Bryozoans, known as ‘moss animals’ – have begun reclaiming the area. Life stubbornly persists in settling between two catastrophes. Giant sea squirts – invertebrates shaped like crystal bottles – seem to find what they need to flourish here despite the constant threat of eruptions.

The Victoria, the Gombessa team’s trimaran, anchored in front of Stromboli. Behind, you can clearly see the boundary between the Sciara (or ‘road of fire’ in Arabic) and the green slopes covered with vegetation that the lava flows have spared. — The Victoria, the Gombessa team’s trimaran, anchored in front of Stromboli. Behind, you can clearly see the boundary between the Sciara (or ‘road of fire’ in Arabic) and the green slopes covered with vegetation that the lava flows have spared.

In front of the divers is a brutal slope break. No doubt about it: the divers are about to enter the underwater corridor of the Sciara, where regular landslides prevent marine life from settling.

This picture is almost life-size: it shows a young dogfish (or baby shark), Scyliorhinus stellaris, measuring just 20 cm long. We can see by the shiny flashes of its skin that it is covered with placoid scales made from enamel and dentine, like its teeth. — This picture is almost life-size: it shows a young dogfish (or baby shark), Scyliorhinus stellaris, measuring just 20 cm long. We can see by the shiny flashes of its skin that it is covered with placoid scales made from enamel and dentine, like its teeth.

It’s still there, 40 METRES HIGH, INTACT AND SOLID, hosting more flourishing underwater life precisely because it has been spared.

No matter how precarious the undertaking, one day their constantly renewed work will cover all these mineral and monochrome foundations with an organic and multicoloured varnish. A little further on, a field of white gorgonians has had a close call: it is half buried in the black sand of a recent lava flow. A 20 cm-long juvenile dogfish is cruising around here. This baby shark, whose fate is uncertain, is a perfect symbol of this reborn ecosystem.

After a few days of dives and side-scan sonar imaging to better understand the topography, we finally find the pinnacle that Roberto remembered. The petrified lava composing it is so hard that it has resisted the multiple eruptions that have ravaged the surrounding area. It’s still there, 40 metres high, intact and solid, hosting more flourishing underwater life precisely because it has been spared. Here we are at the top of this lava tower. I leave my companions there, taking a moment to move back and take in this immense volcanic cathedral in its entirety. All around, the animal city has disappeared... but Our Lady of Stromboli has not burned.

Back to civilisation. A few days later, our boat is on the outskirts of Naples. Three million men and women live here between the sea and the volcano. The Neapolitans know that the Pompeii disaster that occurred in 79 AD can happen again tomorrow. Whether carefree or reckless, they accept their situation as hostages of Vesuvius, caught in a vice-like grip between water and fire.

We are here because a friend of Roberto’s (he has many of them in Italy) is looking for ways to explore and study a strange formation. “It’s a hole in the bottom of the sea”, say the researchers who know little more than that and who have come in great numbers to watch our dive. Each one hopes to collect samples and data specific to their discipline: pieces of rock or sediment for the volcanologists and geologists; temperature, acidity, current and luminosity records for the oceanologists; and potentially samples of life, if there is any, for the biologists.

On the underwater slopes of Stromboli, this enormous volcanic rock pinnacle located between a depth of 80 and 20 m is the result of a dazzling eruption from a distant era. The petrified lava that constitutes it is so hard that it has resisted the eruptions of the main crater at an altitude of 900 m, which nevertheless generate regular lava flows and even powerful landslides. — On the underwater slopes of Stromboli, this enormous volcanic rock pinnacle located between a depth of 80 and 20 m is the result of a dazzling eruption from a distant era. The petrified lava that constitutes it is so hard that it has resisted the eruptions of the main crater at an altitude of 900 m, which nevertheless generate regular lava flows and even powerful landslides.

Looking up, WE CAN STILL MAKE OUT A SMALL GREEN GLOW: the large entrance shaft has become a tiny mouse hole.

To say this dive is appealing would be an outright lie. There is nothing there to make you want to dive: the water is green, murky and cold. As for the seabed, it is flat and muddy, littered with waste from the nearby megalopolis. We are in the Bay of Naples, less than a mile from the coast. There is nothing to see, but there is a sense of curiosity to be satisfied. Can it really be possible that on this seabed, which is soft and flat for miles around, lies the entrance to a vertical, rocky cave of which no instrument has yet been able to probe the depths? The fishermen have a legend involving a ‘mouth’ at the bottom of the bay that swallows their nets, lines and traps. It is said that things they put in the water do not always come back.

That’s why we are in the water just a few hours after our arrival. As we approach the indicated point amid the dark fog that our lamps try in vain to pierce, fishing lines and remnants of nets indeed appear to converge on the same point, towards which we are also heading. Suddenly we reach the edge of the ‘mouth’. The soft mud gives way to black rock. I feel as if I am at the edge of a well. The water is too murky to see the whole perimeter, but from the curvature, one can imagine a large well measuring probably more than 10 metres in diameter. My depth gauge already shows 50 metres when we tip into the black hole. It is an almost perfect cylinder. We sink slowly and encounter a first surprise: the water is clearer here than outside. As we descend to 55, 60, 65 and 70 metres, one might think that this gigantic well would sooner or later shrink and then completely close up, yet the opposite occurs. At 75 metres, a space that is no longer a shaft but instead an abyss opens up before us. It is so big thatthe beam of our lamps is lost in the dark before it is able to hit a wall. The descent continues to 80, 85, 90, 96 metres... We finally reach the bottom, littered with fishing gear. Looking up, we can still make out a small green glow: the large entrance shaft has become a tiny mouse hole.

At 96 metres, we don’t have much time left. Once the measuring instruments are installed (they will remain there for six months), the decision is made not to go back up towards the little green light, but instead to try to locate the walls of the abyss. We have a major advantage: one of our thrusters is equipped with sonar technology that compensates for our blindness. It informs us that the walls are within 25 metres of us. We are thus in the centre of a huge circular chamber. The image of the cave begins to take shape in our minds, looking like a gigantic wine carafe with a long narrow neck suddenly widening without any transition into a large basin. It is probably an ancient magma chamber emptied of its lava and which, sooner or later, will collapse inwards, generating a sort of small tsunami that will gently lap against the beaches of Naples.

Just 2 km off the coast of Naples, at the foot of Mount Vesuvius, lies what researchers have dubbed the ‘black hole of Naples’. The Gombessa team has carried out the first exploration of what appears to have been a magma chamber. The entrance, barely 12 m in diameter, is located on a muddy seabed at a depth of 50 m. The hole is vertical like a perfect cylinder, but at 75 m, the divers discovered that the shaft widened to the point where they could no longer distinguish the walls. This vertical cave is shaped like a giant wine carafe, and the divers finally reached the bottom at a depth of 96 m.

The walls of the vertical cave in the Bay of Naples, an ancient magma chamber, are covered with small filter-feeding invertebrates and are crossed by rare long-clawed crustaceans. Amongst these creatures living on borrowed time is a rare species, described only at the end of the 20th century in another Mediterranean cave: the carnivorous sponge! While the name might make you shudder, its appearance is less worrying as it is immaculately white and shaped like a miniature swab. Its hooks trap small crustaceans that get too close, and then the sponge’s tissues grow around the prey until they are engulfed in its flesh. There is no lightning attack, no violent combat; this is a simple and slow assimilation of one being by another in a matter of a few days. This turned out to be a new species for scientists that is currently being catalogued. The exotic and the unknown are not always far away, yet gaining access to them can be difficult! — The walls of the vertical cave in the Bay of Naples, an ancient magma chamber, are covered with small filter-feeding invertebrates and are crossed by rare long-clawed crustaceans. Amongst these creatures living on borrowed time is a rare species, described only at the end of the 20th century in another Mediterranean cave: the carnivorous sponge! While the name might make you shudder, its appearance is less worrying as it is immaculately white and shaped like a miniature swab. Its hooks trap small crustaceans that get too close, and then the sponge’s tissues grow around the prey until they are engulfed in its flesh. There is no lightning attack, no violent combat; this is a simple and slow assimilation of one being by another in a matter of a few days. This turned out to be a new species for scientists that is currently being catalogued. The exotic and the unknown are not always far away, yet gaining access to them can be difficult!

In the meantime, an ecosystem has become established inside. The walls that we have finally reached are covered with small filter-feeding invertebrates and crossed by rare long-clawed crustaceans. Amongst these creatures living on borrowed time, we identify a rare species, described only at the end of the 20th century in another Mediterranean cave: the carnivorous sponge! While the name might make you shudder, its appearance is less worrying as it is immaculately white and shaped like a miniature swab. Its hooks trap small crustaceans that get too close, and then the sponge’s tissues grow around the prey until they are engulfed in its flesh. There is no lightning attack, no violent combat; this is a simple and slow assimilation of one being by another in a matter of a few days.

The ascent finally begins. What a strange sensation: we did not dive to the bottom of the sea, but rather under the bottom of the sea. We have dived into the heart of a dive. An abyss within the abyss! Although we didn’t feel very enthusiastic initially, we nevertheless returned three times the following days, with immersions of more than four hours on each occasion, as it takes time to observe the imperceptible predation of the carnivorous sponge!

A few months later, we learned from the few individuals collected that this was a new species for scientists and that it is currently being catalogued. Once again, the exotic and the unknown were not far away, making the discoveries even more fascinating.

Three weeks have passed and the Victoria is already leaving southern Italy, heading north-west towards Corsica. There are still no other boats on the horizon, except for the occasional fishing craft. We are sailing on the Mediterranean of a bygone era and it is frankly a pleasurable experience. I don’t remember ever seeing as many dolphins as in this particular year. Fisherman friends have told me that they have had their best catches in decades. We often hear about the fragility of Nature, but this trip opened my eyes to the condescending attitude implied by this expression. Nature is not fragile, in fact quite the opposite: although it is attacked and injured, despised and reduced, it clings on, resists and bides its time. Three weeks spent at the foot of volcanoes that devastate civilisations remind us of our vulnerability. Nature is not fragile, we are: poor runners and bad swimmers, doomed to perish if our antibiotics, supermarkets and high-speed connections vanish. All it takes is for the Earth to start coughing to remind us of our insignificance. A small volcanic sneeze is nothing at all for the planet, but an apocalypse for us, resulting in explosions, flaming clouds, tsunamis, etc.

Instead of videoconferencing or staying in large hotels around the world, the G7 summits should be held at the foot of these active volcanoes. Not in the hope of seeing our arrogant leaders disappear in a lava flow, but rather so that they can measure their own fragility, like that of all humankind, and relativise their power that is so pitifully small in the face of these colossal forces. If the beauty of the world no longer moves them, if its horrors no longer outrage them, we can safely wager that the demonstration of the omnipotence of Nature will teach them the lesson of humility and respect that humankind too often lacks.