Etna at risk of catastrophic collapse

Etna, one of the most active and iconic volcanoes in the world, is about to collapse sharply into the sea, potentially leading to a devastating tsunami, according to new research.

In an article published in the journal Progress of science, a team led by Morelia Urlaub of the EOMAR Helmholtz Ocean Research Center in Kiel, Germany, presents findings that explain why the southeastern flank of the volcano slides into the sea at a rate of three to five centimeters each year. phenomenon documented for the first time in the 1980s.

It turns out that the cause is not the increase of the pressure of the magma that swells in the pipework of Etna, but gravity.

The conclusion is of paramount importance for the assessment of the risk posed by the volcano located between two densely populated cities, Messina and Catania. The movements caused by magma and the movements due to gravity, Urlaub and his colleagues report, "have fundamentally different risk implications".

"While magma dynamics can cause slope breaks near magmatic pathways, progressive and deep gravitational deformation can lead to catastrophic collapse."

The difference is significant. With the deformations due to the magma, the pressure is maximum at the heart of the volcano, it decreases as it progresses to the outside. With the gravitational change, the pressure is greatest on the sidewall itself when it is dragged into the sea – an effect that occurs regardless of any activity triggered by the magma.

Until now, the researchers report that "the general consensus for Etna was that it was mainly the magnetic plumbing system that was causing the movement of the southeast flank unstable, rather than the gravitational or tectonic forces."

This assessment – and therefore a large number of public safety action protocols – is about to change.

To obtain their result, the researchers installed a network of five transponders equipped with pressure sensors on the flowing flank of Etna, about 1,200 meters below sea level. The transponders were able to gather information precise on the smallest change of location of the volcano by constantly exchanging signals between them.

The system was able to detect any change in vertical or horizontal alignment at distances less than one centimeter. The results clearly revealed that part of the flank is moving relative to stable formations on both sides.

Mount Etna is an extremely active volcano, erupting at varying degrees of severity every two years. On December 3, 2015, it erupted into life, sending a plume of ash within seven kilometers. In March 2017, a much smaller eruption injured 10 people, including members of a British television crew, who were circling near the summit.

However, the findings of Urlaub and his colleagues strongly suggest that the explosion of magma plumes and ash clouds are not the only – or perhaps even the greatest danger – posed by the well-known landmark. Sicily.

"We can not exclude that the flanking movement turns into a catastrophic collapse, implying that the flanking movement of Etna poses a much greater risk than previously thought," concludes they.