Mount Etna, one of the world’s most active volcanoes, is giving one of its periodic series of rumbles. This time, however, volcanologists are concerned that something seismic could be about to happen

Where is it?

Mount Etna is on the east coast of Sicily. It is over twice the height of Ben Nevis and lies between two of the island’s three most populous cities: Messina, which is the one you sail into if you’re arriving in Sicily from the mainland, and Catania, which is where Italy’s National Institute of Geophysics and Volcanology (INGV) has a base and for very good reason. The INGV has 100 scientists there watching and monitoring Etna around the clock, helped by data from 150 monitoring stations on the volcano’s slopes. These provide information about everything from ground temperature and gas emissions to seismic activity and should give an early warning of any potential eruption.

Is there anything to see?

There certainly is. Since February Etna has been putting on quite a show, with typical lava fountains reaching 1500 metres and lighting up the night sky for miles around. It isn’t just lava, either. Volcanic rock (known as lapilli) is being thrown several kilometres into the air and ash is falling on nearby towns, sometimes endangering health. All over the area locals have taken to walking out with umbrellas, even when it isn’t raining, and diggers have been used to clear the volcanic ash, which is piling up like so much weird, black snow.

Are volcanologist worried?

Volcanologists are always worried, it goes with the territory. So far the lava fountains, lapilli, smoke and ash are within the range of normal activities for a volcano of Etna’s size. But as INGV chief Giuseppe Salerno told one newspaper: “What is really peculiar is that the volcano is behaving like a machine, with rhythms that have almost mathematical precision. This is why we’ve been monitoring its every breath, rumble and quiver in recent months.” He makes it sound uncannily like a ticking bomb ...

And will there be a bang?

Possibly. Analysis of the ash shows that it is has come from what’s known as ‘primitive magma’, the stuff that lies six or seven miles down under the earth’s crust. That’s not good, which is the second reason the volcanologists are worried.

Is there a third?

There is. The current eruptions have been coming from Etna’s south crater, which acts as a sort of safety valve. But if there is a major release of ‘primitive magma’ and the valve can’t accommodate it, then it could cause a so-called ‘lateral eruption’. One such event happened 40 years ago this month and very nearly buried the town of Randazzo, while another in 1669 lasted five weeks, destroyed a dozen or so villages and produced a lava flow which eventually reached Catania itself, where the city walls diverted most of it into the harbour.