Submarine volcanoes


The Tyrrhenian Basin is the deepest part of the western Mediterranean: the Tyrrhenian Trench reaches a depth of 3800 meters. The origin of the Tyrrhenian is part of a broad geological process that has affected the entire Mediterranean area, linked to the convergence of the Eurasian and African tectonic plates. The process, which began 10 million years ago at the same time as the construction of the Apennine mountain ranges, is marked by volcanism.

Thus, its seafloor is characterized by the presence of numerous submarine ridges and volcanic type reliefs.
Many island or coastal volcanoes actually have extensive submarine parts. For example, 95 percent of the surface area of Stromboli volcano is below sea level. However, there are entirely submarine volcanoes that may be similar or larger in size than those on the surface.

Submarine volcanoes are very difficult to study because of the lack of direct access. Nonetheless, studies of marine geology in recent decades have allowed a greater understanding of their nature and operation. Observations and sampling are carried out by means of oceanographic ships.

In the case of the Italian seas, submarine volcanic activity is concentrated in parts of the Tyrrhenian Sea and the Sicilian Channel, where the Earth's crust is thinner and more fractured. Some submarine volcanoes are still active and sometimes manifest their presence by releasing gas and deforming very slowly; others now extinct represent real seamounts or seamounts. Their activity turns out to be different from that of volcanoes present on dry land because they are surrounded by seawater, which rapidly cools the emitted products and sometimes fragments the magma generating small explosions, the products of which are partly deposited on the bottom and dispersed by sea currents.

In addition to the best-known Marsili, Vavilov, and Magnaghi, the submarine volcanoes Palinuro, Glaucus, Aeolus, Sisyphus, and Enarete should be mentioned, as well as the numerous volcanic apparatuses in the Sicilian Channel, where the submarine eruptions off Pantelleria in 1891 and off Sciacca in 1831 represent the only historical records of this type of activity.

The International Commission. To acquire a more complete knowledge and assessment of the current state of activity of submarine volcanoes, provided for in Article 1 of opcm No. 3873 of April 28, 2010, the Head of the Department formalized the establishment of an international technical-scientific Commission, with the decree of April 18, 2011.
The Commission, composed of national and international experts, will serve for one year. The Commission's task will be to provide, in addition to periodic progress reports, a final report with an in-depth analysis based on the state of the art of the dangerousness of submarine volcanoes present in the Tyrrhenian Sea and the Strait of Sicily, as well as indications on how to direct studies and research and implement the monitoring system, for effective civil protection action.

It is the largest volcano in Europe, with a length of about 50km and a width of 20km. It has a height of 3km above the surrounding sea floor, and its "ridge" extends linearly in a north-northeast and south-southwest direction for 20km, reaching depths of less than 1000m.

It is formed by a series of volcanic buildings of different sizes. The western flank consists of conical buildings, while the northwestern flank is characterized by several "flat-topped volcanoes" and a staircase of stacked lava terraces.

Although an ongoing eruption has never been observed, Marsili's activity is evidenced by the circulation of high-temperature fluids that deposit sulfides of lead, copper, zinc, and oxides and hydroxides of iron and manganese on the seafloor.

The submarine volcano Vavilov has a length of 30km in a north-northeast and south-southwest direction, a width of 15km and rises 2.7km above the surrounding seafloor.

The main feature of the volcano is the strong asymmetry of its eastern and western flanks: the former is characterized by numerous conical apparatuses with a morphology similar to that of Marsili volcano, while the latter is steeper and without any major morphological elements.

It is currently considered inactive.

Palinuro is a volcanic complex about 75km long, consisting of at least 8 major edifices aligned roughly east-west, while Glabro lies not far from the Palinuro volcanic complex along the same alignment. The summit of these two volcanoes is around 100m below sea level.

The Alcione volcano and the twin apparatuses of the Lametini are located intermediate between the Palinuro-Glabro alignment and the Aeolian Islands arc. They are conical volcanoes, about a thousand meters high relative to the surrounding sea floor.

In the Aeolian apparatus all the major buildings have emerged and given rise to islands, although minor apparatuses exist, particularly around the Vulcano-Lipari-Salina alignment. West of the archipelago are the three apparatuses of Aeolus, Enarete and Sisyphus. The buildings are elongated and aligned in a northwest-southeast direction and about a thousand meters high. Aeolus is distinguished by having a flat top. Finally, in the western Tyrrhenian Sea, just west of Vavilov volcano is Magnaghi volcano, similar in structure and genesis to the larger and younger Vavilov and Marsili volcanoes.

The Canale di Sicilia is an area of widespread volcanism since it is tectonically very active. This volcanism, some of which is still active, has given rise to the islands of Pantelleria and Linosa and numerous submarine volcanic edifices, such as Ferdinandea or Graham, Terrible, Unnamed, Nerita and Bannock, aligned mainly in a northwest-southeast and north-south direction.

Ferdinandea Island was originated in 1831-across from the town of Sciacca-by the accumulation of the products of volcanic activity. This small volcanic cone was destroyed by wave motion a few months later, while the Kingdom of the Two Sicilies, England and France claimed its sovereignty by assigning it different names: Ferdinandea, Graham and Giulia.

Today, the apparatus lies at a minimum depth of 20m below sea level and has an outgassing activity, developing columns of gas tens of meters in diameter.

A recent hypothesis interprets the Graham bench, along with the Terribile and Nerita benches, as the expression of a large submarine volcano, named Empedocles, similar in size to the Etna apparatus. However, definitive evidence is still lacking to confirm this hypothesis.