by Maria Chiara Rosace, Filippo Toscano, Antonino Napoleone | November 19, 2020.

The most restless volcano in Europe, a UNESCO World Heritage Site, has once again been in the international spotlight. Thanks to an incredible shot, the photographer Luciano Gaudenzio won the prestigious “Wildlife Photographer of the Year” award, for the “Earth’s environment” category, a photo contest organised by the Natural History Museum of London. The photo was noticed and awarded, for the category “Landscapes”, also at the GDT (German Society for Nature Photography) contest considered as one of the most prestigious “wildlife” photography competition in the world. 

Gaudenzio decided to entitle his photo “Etna’s River of Fire”; a title that, looking at the shot (Figure 1), seems to be very appropriate.

Figure 1: “Etna’s River of Fire“, Luciano Gaudenzio, winner of the “Wildlife photographer of the year” award for the Earth’s environment category.
Waiting for “the perfect moment

The beautiful picture immortalises a real glowing river flowing from a large opening on the side of the volcano.
In order to witness this surreal show, Gaudenzio climbed the Etna’s north face for several hours and with a skilful play of lights, he captured what he described as “the perfect moment”. The eruptive side vent, star of the shot, had appeared on the volcano’ southside and then collapsed a few days after the wonderful and unique picture was taken. Taking this photo was certainly not a stroke of luck. It took patience and perseverance, qualities that characterise the work of the Italian photographer. Gaudenzio has worked for six years in a project named “L’altro Versante” (i.e. “The other side”) together with two colleagues, Maurizio Biancarelli and Bruno D’Amicis: the aim of the project was to capture the most beautiful peaks and mountains of Italy and use photography as a powerful tool of universal communication.

This amazing picture, taken with a Canon EOS 5D Mark III, allowed Gaudenzio to win the coveted international award.

A bit of geology

Italy is a country with many volcanoes: Etna, Stromboli and Vesuvius are certainly the most famous, but at least ten volcanoes are still considered active nowadays. Etna is the most active volcano in Europe and has been erupting continuously for almost 30 years. What we see today is only the most recent phase of a volcano with an eruptive history of over half a million years1.

In Italy, however, there are not only active volcanoes. In addition to those with persistent activity, there are dormant ones and volcanoes considered extinct, as their eruptive activity has been interrupted for several thousand years so far. In Italy, at least 70 volcanoes have been counted, most of which spread through the seabed between Tuscany and Sicily2. The Palinuro volcanic chain, for example, extends in depth from about 3200 m to 80 m below the sea level and it shows magma rising activity at times3

But what are volcanoes, and how are they formed? Let’s start from the assumption that we live on the surface of a thin layer thick 35 km only and called the Earth’s crust. The radius of the Earth is approximately 6000 km. Volcanoes are openings in Earth’s crust, through which materials come out in a liquid, solid and gaseous state. Movements that take place under the Earth’s surface are at the basis of the whole process: when an Earth’s plate collides with another plate, there are hot materials rising from the contact area towards the surface (Figure 2). The Mediterranean area is characterized by the collision between two lithospheric plates: the African Plate and the Eurasian Plate, responsible for the volcanic activity of the Italian peninsula.

Figure 2: The model shows oceanic ridge volcanism where magma is brought to the surface by convection, cools and forms new oceanic crust. Source; http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/chaps/chapter07-05.html

Depending on their external structure, volcanoes can be divided into cone volcanoes, such as Etna, or shield volcanoes such as Mauna Loa in Hawaii islands. Etna is a stratovolcano, 3,324 m high1, the largest in Europe and among the most active volcanoes in the world. Etna’s height is actually variable because of eruptions that can cause its lowering or raising. Etna erupts both from the four summit craters and from the sides, at intervals that can last from a few months to tens of years (Figure 3). Today its eruptive activity is mainly effusive, characterised by the emission of lava flows that flow along the slopes of the volcano (with basaltic magma flows, very liquid), just as illustrated in Gaudenzio’s shot. However, there is also a type of explosive activity (named Strombolian eruptions): thick columns of ash and gases, visible even from space, as well as various rocky fragments produced by the eruptions and thrown in every direction (up to several km away) often emerge from Etna.

Figure 3: Scheme showing different types of volcanic eruptions and related Etna powering systems (Geological Scheme of M. Neri, INGV-OE). Adapted from: http://www.ingv.it/it/etna

In quiet periods, the volcano presents a continuous and persistent degassing activity from the summit craters.

A monitoring system has been installed on Etna to capture the sound signals preceding the eruptions: seismographs, thermal cameras, satellite data, gravitational field sensors. From the online website of the INGV (Istituto Nazionale di Geofisica e Vulcanologia, i.e. the Italian National Institute of Geophysics and Volcanology) it is possible to see images from video surveillance stations located on the volcano: http://www.ct.ingv.it/index.php/monitoraggio-e-sorveglianza/segnali-in-tempo-reale/video-sorveglianza-vulcanica-etna

The genesis of magma

Magma is a molten mass, mainly of silicate composition (silicates are a class of minerals consisting of silicon and oxygen and present inside magmatic rocks), rich in dissolved gases and suspended crystals. Primary or basaltic magma (of basic composition) originates from the melting of the mantle. If the magma is produced from the continental crust, it is called granitic magma, as it has a predominantly acidic composition. Basic magma is very fluid and has very high temperatures (up to 1200°C!). It generally comes out on the surface with moderate effusions and originates the so-called shield volcanoes. If the magma is acidic the eruption is more violent and explosive5. The emission of lava and the throwing of pyroclasts (literally “fire fragments” originated from the shattering of rocks coming from the volcanic mountain) can alternate, resulting in a stratovolcano, as it happened for Etna after millions of years!

Conclusions

Since ancient times, Greek and Latin writers composed descriptive and illustrative manuscripts which had as their main subject Etna’s eruptions. There is no man who cannot be bewitched by the grandeur of this volcano: breath-taking views, an extraordinary example of continuous geological processes, an undisputed educational value that attracts people from every corner of the planet. Some writings dating back to 1886 describe it as follows:

“Majestic in height and size, splendid in its singular beauty of colour and shape, superbly calm when it does not show itself frighteningly irate, Etna is not only the subject sympathetic to poets and painters, but it is the mysterious sphinx that has tempted the scientist at all times, it is one of the most attractive themes that have deserved the attention and study of the naturalist”.6

Bibliografia:
  1. INGV (Istituto Nazionale di Geofisica e Vulcanologia), online. Etna. https://bit.ly/3kyvrPp. Accessed 15 November, 2020
  2. Pezzella F. Focus sui vulcani italiani, parola all’esperto. http://www.ingv.it/it/newsletter-ingv-n-1-gennaio-2020-anno-xiv/focus-sui-vulcani-italiani-parola-all-esperto. Accessed 10 November, 2020
  3. INGV (Istituto nazionale di geofisica e vulcanologia). Una famiglia di vulcani nel Mar Tirreno. 2017. ingv.it/it/stampa-e-urp/stampa/comunicati-stampa/2831-una-famiglia-di-vulcani-nel-mar-tirreno?highlight=WyJwYWxpbnVybyJd. Accessed 8 November, 2020
  4. Guide vulcanologiche Etna nord. Vulcano Etna – Storia evolutiva.  https://www.guidevulcanologicheetna.it/vulcano-etna-geologia-storia-evolutiva/. Accessed 8 November, 2020
  5. Peretti RC. Il processo magmatico. In: Baldini D, ed. Geosfera, La terra e lo spazio. Editore Bulgarini, Firenze.
  6. Gentile-Cusa B. Sulla eruzione dell’Etna di Maggio-Giugno 1886. 1886. New York Public Library
Tags: , , , , , , , , ,