London, Sep 22 (IANS) Scientists are planning to bore deep into the heart of an active volcano to try and protect Naples from a devastating eruption.

They will be placing sensors inside Campi Flegrei, a volcano in southern Italy, by drilling a 4,000-metre hole into its side early next year.

They will measure the difference in temperature of the rocks to find out where the red-hot magma lies inside the mountains.

Campi Flegrei caldera lies around eight km west of Naples. More than 1.5 million people live near the low-lying volcano, reports the Daily Mail.

It has had periods of unrest in 1969-1972, and 1982-1984 but it last erupted in 1538, reports the journal Nature.

Movement in the ground over the past 40 years has made geologists fear that another massive eruption is likely.

Scientists estimate that magma lies at least 7,000 metres below the surface of the caldera. But little is known about Campi Flegrei, or similar volcanoes.

‘Calderas are the only volcanoes that can cause truly catastrophic eruptions with global consequences, yet they are still poorly understood,’ says Giuseppe De Natale, project coordinator and a geophysicist at Italy’s National Institute for Geophysics and Volcanology in Naples.

Scientists also expect to hit high temperature liquids (up to over 900 degrees F) which, could be used to generate geothermal energy.

But local critics say the drilling is too close to the city and could even trigger an explosion, which could be catastrophic if it took place close Naples.

‘No similar project has ever faced such temperatures,’ De Natale told Nature magazine.

Borehole fibre-optic sensors will help scientists know where the magma is stored.