The force of gravity is pulling Etna out to sea, raising the possibility that the flank of the active volcano could one day suffer a catastrophic collapse. Mind you, there is no indication that such a collapse is imminent, but new research has found that the southeast flank of the Italian volcano is moving both above ground and below the sea. These movements show that the risk of collapse is greater than previously believed, explain scientists at the Helmholtz Center of GEOMAR Helmholtz in Kiel (Germany) in the journal Science Advances.
Thus, in the future, the danger of this volcano would not be fire, but water, since Mount Etna, located on the Italian island of Sicily, is slowly and inevitably sliding towards the Mediterranean Sea, a growing movement that scientists have watched for decades.
Etna is the most restless volcano in Europe. This mountain has experienced active periods since around 6,000 BC and is currently in an active eruption cycle since September 2013, according to the Smithsonian Institution’s Global Volcanism Program.
Researchers using satellite data and GPS measurements have also observed that the southeast flank of Mount Etna has drifted out to sea for at least 30 years. In March, scientists from the Open University (UK) reported that the slope moved an average of 14 millimeters each year between 2001 and 2012 alone.
The debate among experts has been whether this spread is due to magma that moves below and within the volcano or if it is mainly due to gravity, since this pushes the materials that the volcano expels, downwards.
“That is common with these large volcanoes. The materials were scattered at the base,” says Morelia Urlaub, co-author of the work.
Mount Etna also has its “feet in the water, ” Urlaub said, as its slopes continue below the Sicilian coast and into the Mediterranean. Until now, however, no one had measured how the flank moved below sea level.
Underwater landslide
Using a network of seabed sensors, the experts measured how sound traveled from one transponder to another every 90 minutes between April 2016 and July 2017 (the time it takes from one to the other reveals the distance between the transponders), being able to detect any changes in the seabed during the study period.
They found that over an eight-day period in May 2017, a fault on the submarine flank of Mount Etna changed by as much as 4 centimeters. It was not an earthquake, as the earthquake occurred as a gradual landslide.
The area where the researchers measured the landslide is far from the magma chambers in the center of Etna, meaning the movement was not due to magma surge within the volcano’s underground chambers, but to the inexorable work of gravity. “That is bad news for the risk of human life,” Urlaub said.
“We know from the geological record, that other volcanoes have catastrophically collapsed and caused really big, very big landslides, and if these landslides go into the sea, they can cause a tsunami,” Urlaub continues.
The possibility of that happening on Etna cannot yet be quantified . Scientific observations of the mountain date back only a few decades and the entire history of Etna spans 500,000 years. More monitoring is needed to detect if there is any change in the way the slope is moving and to estimate its risk of collapse, the expert concludes.
Reference: Gravitational collapse of Mount Etna’s southeastern flank. Morelia Urlaub, Florian Petersen, Felix Gross, Alessandro Bonforte, Giuseppe Puglisi, Francesco Guglielmino, Sebastian Krastel, Dietrich Lange1 and Heidrun Kopp. Science Advances10 Oct 2018: Vol. 4, no. 10, eaat9700 DOI: 10.1126 / sciadv.aat9700
