Europe's biggest and most active volcano is sliding into the Mediterranean Sea and could suffer catastrophic failure one day—even if that day is far away, the BBC reports. Scientists who studied Mount Etna on the Italian island of Sicily say it is sliding just over half an inch annually thanks to weak sediment and a modest slope of 1-to-3 degrees. Moving east-south-east, Etna should reach the coastal town of Giarre nine miles away in just over a million years. Of greater concern: Etna could endure catastrophic failure on her lead flank, as experts have seen in extinct volcanoes that went adrift. "I would say there is currently no cause for alarm, but it is something we need to keep an eye on, especially to see if there is an acceleration in this motion," says lead author John Murray.
"Around one million people live on Etna and its immediate surroundings, so the destruction of property and loss of life could be catastrophic," says Murray, per the Telegraph. "Clearly even the mention of such a dangerous event would be very unnerving for the people who live on Etna, so I am anxious that they don't get the wrong impression." Murray suggests measuring Etna's slide in 10 years to see if it has doubled—which "would be a warning," he notes. His team's 11-year study marks the first time experts have seen an entire active volcano sliding on its base. Standing nearly 11,000 feet high between the cities of Catania and Messina, Etna spewed lava three times over just three weeks last March, the Sun reports. (Another volcano's eruption recently "annihilated" a mountain peak.)