Europe’s biggest active volcano is slipping into the ocean, and it’s feared the recent discovery could trigger a tsunami.
Such an event would put neighbouring communities in Sicily at risk as debris enters the surrounding ocean, possibly causing devastating waves.
However, researchers monitoring the site say all they can do for now is “keep an eye” on the active volcano as there is no way of telling whether this acceleration will come within years or centuries.
Previous work suggested Etna’s movement was the result of magma swirling inside the volcano, meaning the movement would be confined to its summit.
However, careful monitoring of the seafloor around the site has revealed that Etna’s gradual sliding movements affected a far wider area – a finding the scientists say increases the risk of “catastrophic collapse”.
“Mount Etna is huge. It’s over 3,000m high and it rises up from below sea level,” said Dr Morelia Urlaub from Geomar Helmholtz Centre for Ocean Research. “It’s really heavy, and it grows continuously.”
Past work has only focused on Etna’s above-ground component, but gathering the new underwater measurements confirmed the movement is due to gravity acting on its growing, and unstable, flank.
“You can think of a slow landslide at the moment – we had 4cm in 15 months, so it moves really slowly, but there is a danger that it could accelerate and form a landslide that moves really fast into the sea,” Dr Urlaub told The Independent.
There are historic accounts of such collapses happening on smaller volcanoes, but the geological record has evidence of it affecting large areas in Hawaii and the Canary Islands millions of years ago.
To understand whether something similar was going on in real-time at Etna, the scientists collected data from pressure sensors over several months, publishing their results in the journal Science Advances.
While this data gives them a better idea of the volcano’s movements, Dr Urlaub said that it is difficult to calculate the risk of disaster from these measurements given its immense age.
“We have been monitoring Etna on shore for around 30 years now, but 30 years is nothing compared to the age of Etna, which is 500,000 years old,” she said.
“It could happen in 10 or 100 or 100,000 years – we can’t tell.”
With this in mind, she said for now it is very important to keep monitoring the volcano and try to get an idea of what level of movement could indicate an imminent collapse.
“There is much more research to be done,” Dr Urlaub said, noting they would try “to be aware there is a hazard, and keep an eye on Etna’s flank”.