A project to drill deep into the heart of a supervolcano in southern Italy has finally received the green light, despite claims that the drilling would put the population of Naples at risk of small earthquakes or an explosion.
Italian news agency ANSA quoted project coordinator Giuseppe De Natale of Italy's National Institute of Geophysics and Volcanology as saying that the office of Naples mayor Luigi de Magistris had approved the drilling of a pilot hole 500 metres deep.
The Campi Flegrei Deep Drilling Project was set up by an international collaboration of scientists to assess the risks posed by the Campi Flegrei caldera, a geological formation just a few kilometres to the west of Naples that formed over thousands of years following the collapse of several volcanoes.
Researchers believe that if it erupted, Campi Flegrei could have global repercussions, potentially killing millions of people and having a major effect on the climate, but that such massive eruptions were extremely rare.
The project's organisers originally intended to bore a 4-kilometre-deep well in the area of the caldera late in 2009, but the plan was put on hold by then-mayor Rosa Russo Iervolino after scientists expressed concerns about the risks.
Among the critics was Benedetto De Vivo, a geochemist at the University of Naples, who told Science in 2010 that the drilling might cause seismic activity or generate an explosion if it allowed the high-pressure supercritical fluids expected to exist at depths of about 3km or more to come into contact with magma inside the caldera.
''Nobody can say how bad this explosion would be, but it could put at risk some of the surrounding population,'' he said.
De Vivo added that he didn't understand why the well was to be located on the grounds of the former Bagnoli steel mill, on the western outskirts of Naples, and not farther west. (De Vivo did not state that the study might trigger an eruption of the supervolcano.)
Collaboration member Ulrich Harms, of the German Research Centre for Geosciences in Potsdam, said at the time that if the drilling was done in a controlled way, there was no risk to the public.
He pointed out that many multi-kilometre wells had been drilled around the world in order to extract geothermal energy, and that these had not caused explosions.
He believed the project made scientific sense: ''It's not clear if there is a volcanic risk, but it cannot be excluded, and this is why it is better to get more of an idea.''
De Natale told ANSA that work on drilling the pilot well should start within a few months and that a second well 3.5km deep should then follow.
De Natale said that information obtained from sensors placed inside the wells would help to understand the ''bradyseism'' - the rising and falling of the Earth's surface resulting from the movement of magma inside a caldera - occurring in the Campi Flegrei area and to find out whether there was a connection between the phenomenon and volcanic eruptions.
Additionally, he added, the study should provide information that could help to extract geothermal energy from the volcano in the future.