Mount Etna is an ever-evolving mystery. One of the most interesting volcanoes in the world, it never ceases to amaze. This has been said time and again by the same Catania volcanologists who know it like the back of their hands and admire it every day. Yet a “turning point” is just around the corner, and unexpected news could arrive at any moment. The latest is described in a study published in the Journal of Geophysical Research by the University of Lausanne, to which Catania-born Dr. Anna Rosa Corsaro of the INGV also contributed. It seems the origin of Etna may have been something… unique!
How Etna was born
Until now, we’ve always known that Etna was born about half a million years ago, from the bottom of the Ionian Sea. Once upon a time, where the volcano stands today, there was only a large gulf filled with seawater. However, the sea was continually shaken by earthquakes caused by the friction between the enormous African and Eurasian plates; the lava from the first underwater eruptions began to flow from the fractures caused by these shifts.
In Aci Trezza, splendid columnar lavas can still be admired today, testifying to these first “rising” of the volcano. And the Timpa plateau, in Acireale, likely dates back to that “timpe” period, when eruptions occurred through fissures. Over the following centuries, the eruptive conduits slowly moved further and further west, leading Etna to rise to its current location. The volcano’s movement appears to still be westward, as evidenced by the changes to its summit over the last century.
But studies on Etna have never stopped, and today new scenarios are being hypothesized regarding its origin. The study by the University of Lausanne even calls it a “unique origin.” Why?
Why a “unique” origin?
Etna’s formation process appears to fall outside of any of the three major known mechanisms for the classic formation of terrestrial volcanoes. It is not located exactly where plates rub against each other, nor is it located on a subduction zone, but merely “nearby.” Despite being a “land” volcano, it nevertheless has a chemical composition similar to that of so-called submarine “hotspots” (areas of ascent of very hot mantle material). Finally, the material erupted over its long life remains virtually unchanged.
In short, Etna exhibits the formation mechanism of small submarine volcanoes despite being a gigantic terrestrial volcano. Researchers therefore hypothesize that it belongs to a fourth, lesser-known category of volcanoes, known as “petit spots”.
The first identification of this type of volcano dates back to 2006 and described isolated “pockets” of magma that are filled thanks to periodic stresses from seismic faults, which allow the material to rise to the surface. A phenomenon previously observed only in submerged volcanoes, first in the Pacific and then in the Mediterranean. If confirmed, this discovery would change many things about the way we study and experience our volcano.
Etna is more and more special
The science of risk prediction—especially related to earthquakes—is still very imperfect, and the road to achieving high levels of safety is long. But understanding precisely how a volcano behaves could help add new pieces to this type of research as well.
Understanding that Etna belongs to a very specific type of volcanism—and different from others—can open the door for the INGV to better assess risk, while also changing locals’ attitudes toward the volcano. But that’s not all. The study of this new type of volcano, facilitated by Etna’s sheer size, could help investigate the origin and hidden nature of other similar systems around the world. (PHOTOS BY G. MUSUMECI)