Italy and Sicily, regions of high seismic activity
Italy is located on a subduction zone in perpetual tectonic motion: the African and Eurasian plates collide here, with the rotating Adriatic micro-plate in the middle. In Sicily, the ocean floor is breaking up and transforming into a volcanic rift. Why does this happen? Sicily's south-eastern regions are in the midst of a rotation. The island's surface is constantly being compressed and stretched, forming volcanoes on the surface and underwater. There are underwater volcanoes in the Sicilian Channel, one of which erupted in 1831, creating the short-lived island of Ferdinandea. Scientists recently discovered six new undersea volcanoes in the Sicilian Channel while mapping the seabed. The chain of volcanoes stretches from 6 to 22 km off the Sicilian coast, in the north-western part of the channel. A discovery that could lead to a review of the safety of ships transiting over it: the Sicilian Channel is a veritable maritime highway.
Etna: an explosive but also effusive activity
Etna, also known as "the mountain of mountains" or Mongibello (a blend of Latin and Arabic), is Europe's highest active volcano. The giant peaks at 3,350 m and has been in existence for almost 300,000 years. The first ascent of the volcano was undertaken by the Greek philosopher Empedocles between 490 and 430 BC. The story goes that his sandals were found near the crater. Strabo (1st century AD) was the first geographer to write about the giant's physiognomy. His descriptions are precise. They include information on the volcano's vegetation, shapes and slopes.
From a seismic point of view, the volcano alternates between explosive eruptions (called strombolian, after its turbulent neighbor) and effusive eruptions. Explosive eruptions are far more frequent and far more spectacular. These are the summit craters that spew molten lava, sometimes in incredible lava fountains. Effusive eruptions are triggered by fissures in the volcano's flank, from which very fluid lava escapes to form basalt flows as it cools. Lava flows sometimes flow into the sea, and Etna's summit is constantly changing with time and activity. The growth of Etna's current summit was halted almost 2,000 years ago by the collapse of the Piano caldera. However, successive eruptions have formed craters at the summit. Etna's summit is occupied by five summit craters: the North-East crater (1911), the Central crater (1945), the Bocca Nuova (1968) and the South-East crater (1971), the most recent of which, the South-East cone, appeared in 2007.
According to a study published in the research magazine Bulletin of Volcanology, Etna is sliding very slowly towards the Mediterranean Sea, at a constant rate of 14 millimetres per year. The studies were carried out by researchers from the Open University in the UK and the Magmas et Volcans Laboratory at the Observatoire de Physique du Globe in Clermont-Ferrand. The volcano's weakest point is its seaward-facing eastern flank, resting on a base of slippery sediments. Earthquakes are therefore mainly felt in this zone. Magma thrusts play a role in the sinking of the volcano. But this is essentially gravitational, i.e. linked to gravity. But rest assured, Etna won't be sinking into the Mediterranean for thousands of years!
One of the most active volcanoes in the world that fascinated Tazieff
With around 100 eruptions in the 20th century, Etna is considered one of the world's most active volcanoes. In 1972, the vulcanologist Haroun Tazieff described Etna as "a very exceptional and at the same time classic volcano, its type of eruption is the most frequent (...). What sets Etna apart is that it is in almost continuous eruptive activity [...], there are only half a dozen in the world, including Etna, and next to it, Stromboli, in permanent eruptive activity". According to vulcanologists at the Institut national de géophysique et de vulcanologie (INGV), the appearance of two eruptive fractures on the volcano with its five dormant craters is causing the giant to awaken. The first fracture is located at the foot of the volcano's southeast crater, while the second is located on the northeast flank of the second crater to the southeast, which appeared in 2007. These fractures have generated two lava flows and a thick ash cloud. In December 2018, a large ash column forced the authorities to close local airspace, and small earthquakes were felt, the largest of which, with a magnitude of 4.8, collapsed houses and injured around 30 people. Then there were a few eruptions in 2018 and 2019, and above all a massive one in 2021: Etna erupted seven times in less than a month, from February 16 to March 7. The southeast crater was the scene of an incredible 100-metre-high lava fountain, lava flows and an eruptive column several kilometers long in the Valle del Bove. A shower of "lapilli" - fragments of lava that fly and explode on contact with the ground, turning into black dust - covered all the surrounding villages, Catania and even as far away as Syracuse! We saw images of Sicilians, shovels in hand, trying to clear away the ash. A state of regional emergency was declared, with some residents experiencing breathing difficulties. The locals put things into perspective: they've been used to living with the monster for centuries and aren't overly alarmed by its mood swings. In fact, in May and June 2022, a lava flow emerged from the flank of the southeast crater, while in July 2024, lava erupted from the Voragine crater.
Stromboli, a particularly explosive and dangerous volcano
It is without doubt the most dangerous volcano in Italy, more active than Etna because of its permanent eruption, and because it is smaller, it is particularly explosive and unpredictable. It has even given its name to its type of eruption, "strombolian", as it is a textbook case of what are known as red volcanoes: those erupting fluid lava that flows down the sides of the volcano to form lava fountains.
The volcano has been active for almost 3,000 years, so imagine! The recent New Year's eruption in 2003 caused a panic evacuation of the island. After the lava flows of 2007 and the explosions of 2009, the summer of 2014 saw the opening of a new fissure on the eastern slope and the observation of new lava flows up to 1.6 km long. The mouths of the current craters are located at an altitude of 700 m on the western slope. They overlook the sciara del Fuoco, a steep slope bounded by the filo del Fuoco and the filo di Baraona, two enormous fissures that serve as paths for the volcano's ejecta towards the sea. 2017 and 2018 were particularly busy: no major eruptions, but very strong volcanic activity. And then came the eruption in the form of paroxysmal explosions in July 2019. And it took everyone by surprise, especially the tourists on the crater rim who were forced to retreat, including one man who suffered a heart attack. An accident that calls into question the conditions of access. Until further notice, it is no longer possible to climb to the rim of the crater at 924 m, but only 400 m with a guide. However, you can take a boat out at night to see the lava flowing down the side of the Sciara del Fuoco- what a sight! On your return at around 8 p.m., climb up to the observatory to eat a pizza and see the volcanic movement from another angle, and then continue on foot to get closer to the highest point authorized without a guide (290 m). Vulcanologists have opened an interesting information center where you can ask scientists questions.
Vulcano, a "pressure cooker" island
In Homer's mythological tales, Aeolus chose Vulcano as his home. Bubbling Vulcano, with its sulfurous waters, yellow sulfur vapors and fumaroles, bare hills and wild corners, is the most volcanic of the seven islands, but also the most dangerous. Its 21 km2 are home to two active volcanoes: Vulcanello and Fossa di Vulcano. Fossa di Vulcano, which rises to an altitude of 499 metres, produces significant sulphur fumaroles. Vulcanologists often compare it to a pressure cooker. It too has given its name to a type of "Vulcanian" eruption. Less impressive because the lava is less fluid, they are nonetheless extremely dangerous. The lava flows with greater difficulty, and the projections create downward flows that can reach homes. Fallout from lapillivolcanic bombs and pumice stones are dangerous for local populations. The most recent eruptions date back to 1739 and 1888. On August 3, 1888, shortly after midday, an extremely violent eruption took place here. The Fossa crater ejected huge rocks (locals will tell you they were as big as buses), incandescent bombs with a peculiar "bread crust" appearance, and clouds of hot ash. This inferno lasted almost two years, ending in March 1890. The recent increase in fumarole activity on the flanks and rim of the crater justifies the continuing attention paid by vulcanologists to this particular volcano.
Lipari, a concentration of small volcanoes
Of all the Aeolian archipelago, it is the best playground for volcanologists and geologists. Considered the most volcanically concentrated of the Aeolian Islands, its soils and subsoils still bear the scars of successive eruptions. A veritable open-air laboratory, with the Bagnosecco fumaroles, the largest on the island, and thermal springs, the most famous of which, San Calogero, near the port, was used for therapeutic purposes in ancient times. Today, Lipari's volcanic activity is thought to have gone through three periods. The first is illustrated by the various volcanic layers in the west of the island, which today make up the Timponi or Monterosa. The second period led to the formation of Mount Sant'Angelo. Finally, during the last period, volcanoes expelled obsidian and pumice, which also modified the landscape, as in the case of Mount Galliana. The island probably experienced its last eruption in the 8th century, that of Mount Pelato, not without incident, as it covered the5th and 6th century Roman ruins with pumice (visible in the Diance district of Lipari's acropolis). Today, this magnetism is not felt on Lipari, but only observed by scientists.
