Italy and Sicily, regions of high seismic activity
Italy is located on a subduction zone in perpetual tectonic movement: 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 becoming a volcanic rift. Why is this happening? The south-eastern regions of Sicily are in full rotation. The surface of the island is constantly being compressed and stretched, forming volcanoes on the surface and underwater. There are submarine volcanoes in the Sicilian Channel, one of which erupted in 1831 and created the ephemeral island of Ferdinandea. Scientists recently discovered six new submarine volcanoes in the Sicilian Channel while mapping the seabed. The chain of volcanoes stretches from 6 to 22 km off the coast of Sicily, in the northwestern part of the channel. A discovery that could lead to a review of the safety of the ships that transit over it: the Sicilian canal is a real maritime highway.
Etna: an explosive but also effusive activity
Etna, also known as "the mountain of mountains" or Mongibello (a mixture of Latin and Arabic), is the highest active volcano in Europe. The giant rises to 3,350 m and its appearance dates back 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 about the vegetation, shapes and slopes of the volcano.
From a seismic point of view, it is a volcano that alternates explosive eruptions (called strombolian, from the name of its turbulent neighbour) and effusive eruptions. The explosive eruptions are much more frequent and much more spectacular. These are the summit craters that spew molten lava, sometimes in incredible lava fountains. Effusive eruptions are caused by cracks in the side of the volcano from which very fluid lava escapes, producing basalt flows as it cools. Lava flows sometimes flow into the sea, and Etna's summit is constantly changing as time goes by and its activity increases. The growth of Etna's current summit was halted nearly 2,000 years ago by the collapse of the Piano caldera. But summit craters were formed by successive eruptions. The summit of Etna 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 latest 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. Researchers from the Open University in the United Kingdom and the Magmas and Volcanoes Laboratory of the Observatoire de Physique du Globe in Clermont-Ferrand carried out these studies. The eastern flank of the volcano, facing the sea, is its weakest point, resting on a base of slippery sediments. Earthquakes are therefore mainly felt in this area. Magma thrusts play a role in the sinking of the volcano. But it would be essentially gravitational, i.e. linked to gravity. But let's be reassured, Etna will not collapse into the Mediterranean for thousands of years!One of the most active volcanoes in the world that fascinated Tazieff
With about 100 eruptions in the 20th century, Etna is considered one of the most active volcanoes in the world. In 1972, the vulcanologist Haroun Tazieff described Etna as follows: "a very exceptional volcano and at the same time a classic one, its type of eruption is the most frequent (...). What differentiates Etna 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 from the National Institute of Geophysics and Vulcanology (INGV), the appearance of two eruptive fractures on the volcano with five dormant craters is causing the awakening of the giant. The first fracture is located at the foot of the southeast crater of the volcano, while the second is located on the northeast flank of the second crater located to the southeast, which appeared in 2007. These fractures have generated two lava flows and a thick ash cloud. In December 2018, a large column of ash had forced the authorities to close the local airspace and small earthquakes were felt, the largest of which, with a magnitude of 4.8, led to the collapse of houses and about 30 injuries. Then there were a few eruptions in 2018 and 2019 and especially 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 spectacle of an incredible lava fountain 100 meters high, lava flows and an eruptive column for several kilometers in the Valle del Bove. A rain of "lapilli", those fragments of lava that fly and explode on contact with the ground to turn into black dust, covered all the surrounding villages, Catania and even Syracuse! We saw the images of Sicilians, shovel in hand, trying to clear the ash. A state of regional emergency was declared, and some inhabitants experienced breathing difficulties. The inhabitants put things into perspective: they are used to living with the monster for centuries and are not overly alarmed by its mood swings. Moreover, in May and June 2022, it happened again: a lava flow was born on the flank of the southeast crater.
Stromboli, a particularly explosive and dangerous volcano
It is without context the most dangerous volcano in Italy, it is more active than Etna because in permanent eruption, and as it is smaller, it is particularly explosive and unpredictable. It even gave its name to its type of eruption, "strombolian", because it is a textbook case of what is called red volcanoes: those that erupt a fluid lava that forms flows on the flanks of the volcano and form lava fountains.
It has been very active for nearly 3,000 years so imagine! Recently, the New Year's eruption of 2003 caused a panic evacuation of the island. After the lava flows of 2007 and the explosions of 2009, the summer of 2014 was marked by the opening of a new fissure on the eastern slope and the observation of new lava flows reaching up to 1.6 km in length. 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 very steep slope, bounded by the filo del Fuoco and by the filo di Baraona, two huge fissures that serve as paths for the volcano's ejections towards the sea. 2017 and 2018 were particularly lively: no characterized eruption but very strong volcanic activity. And then the eruption in the form of paroxysmal explosions came in July 2019. And it surprised everyone, especially the tourists at the edge of the crater and had to retreat, including a man who had a heart attack. An accident that calls into question the conditions of access. From now on and until further notice, it is no longer possible to climb to the edge of the crater at 924 m, only 400 meters with a guide. Nevertheless, you can go at night by boat to see the lava flowing on the side of the Sciara del Fuoco, what a spectacle! On the way back around 8 pm, go up to the observatory to eat a pizza in front of the volcanic movement seen from another angle, and finally continue on foot to get closer to the highest point allowed without a guide (290 m). The vulcanologists have opened an interesting information center where it is possible to ask questions to scientists. In December 2022, an eruption caused flaming clouds and a small tsunami without causing any damage.
Vulcano, a "pressure cooker" island
In Homer's mythological tales, it is Vulcano that Aeolus chooses to settle. Vulcano the bubbling one, with its sulphurous waters, its vapours and its yellow fumaroles of sulphur, its bare hills and its wild corners, is the most volcanic of the seven islands but also the most dangerous. On 21 km2, there are two active volcanoes: Vulcanello and Fossa di Vulcano. The latter, which rises to an altitude of 499 metres, develops significant sulphur fumaroles. Vulcanologists often compare it to a pressure cooker under pressure. It has also given its name to a type of "vulcanian" eruption. Less impressive because the lava is less fluid, they are nonetheless very dangerous. The lava flows with greater difficulty and the projections create flows below which can reach the houses. The fallout from lapilli Volcanic bombs and pumice are dangerous for the population. The last eruptions date back to 1739 and 1888. On August 3, 1888, a little after noon, an extremely violent eruption took place at this place. The Fossa crater ejected huge rocks (the locals will tell you they were as big as buses), incandescent stones, called bombs, with a particular "bread crust" appearance and clouds of hot ashes. 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 continued attention of vulcanologists to this particular volcano.
Lipari, a concentration of small volcanoes
Of all the Aeolian archipelago, it is the best playground for vulcanologists and geologists. Considered the most concentrated in volcanoes of the Aeolian Islands, its soil and subsoil still bear the scars of successive eruptions. A real open-air laboratory, with the fumaroles of Bagnosecco, the most important on the island, or thermal springs, the most famous of which, that of San Calogero, near the port, was used for therapeutic purposes in ancient times. It is thought today that the volcanic activity of Lipari would have known three periods. The first one is illustrated by the different volcanic layers in the west of the island, which would compose today the Timponi or Monterosa. The second period led to the formation of Mount Sant'Angelo. Finally, during the last period, the volcanoes expelled obsidian and pumice stones which also modified the landscape, like that of Mount Galliana for example. The island probably experienced its last eruption in the 8th century, that of Mount Pelato, not without incident since it covered with pumice the Roman ruins of the5th and 6th centuries (visible in the Diance district at the Lipari acropolis). Today, one does not feel this magnetism while staying on Lipari, only scientists observe it.
