Mount Vesuvius is part of a volcanic province running from Sicily in the south with frequently erupting Mt Etna, northwards through the Lipari/Aeolian Islands in the Tyrrhenian Sea. The floor of which is “littered” with extinct volcanic cones and seamounts. The volcanism continues to the Bay of Naples, the Phlegrian Fields at Pozzuoli, and northwards through the Province of Campania to Tuscany. These are all along the western flank of the Apennines. In addition, there are isolated outposts in Sardinia, the Euganian Hills of the Po valley, Monte Vultura in Basilicata and the island of Pantelleria between North Africa and Sicily.
It seems that volcanic activity in Italy, started in the north and spread southwards. The northern outposts are now completely extinct, whilst activity continues in the south.
TUSCAN – Here the volcanoes are small,scattered and extensively eroded. They date to about between 5 and 2.3 million years old. However, Monte Amiata dates from only 400,000 years ago. The magma is still close enough to the surface for the geothermal heat to be “tapped” at Lardarello and Mount Amiata, producing one of Europe’s most important sources of geothermal energy.
LATIUM – Here the volcanoes are larger and generally more recent, forming distinct stratovolcanoes, calderas and vast sheets of pumice, as well as maars, domes and cinder cones. The eruptions often formed lakes such as Bolsena, Vico, Bracciano, Albano and Nemi. Just to the south of Rome, Colli Albasni (Alban Hills), were active up to only 19,000 years ago.
CAMPANIA – The volcanoes here are concentrated around the northern shores of the Bay of Naples, with outliers at Monte Vultura in Basilicata and Roccamonfina. Vesuvius is still active, and last erupted in March1944 when magma overflowed from the crater northwards and southwards, followed by explosive Strombolian type activity. Altogether the eruption expelled about 35-40 million cubic metres of magma, mostly in the first 4.5 days. Forty seven people were killed from crushed roofs, hits from large scoria and steam blasts at San Sebastiano village, which was over-run by a stream of lava. Volcanic carbon dioxide escaping through the soil, especially from dry wells continued to collect in pockets until the end of 1944. Many animals were killed after wandering into pockets of the gas accumulating close to the ground. Two people were suffocated on 24th March 1944 at Ercolano as they were sheltering in an air raid shelter within their basement.
The island of Ischia on the western flank of the Bay of Naples is a volcano, but the Phleaegrian Fields form the heart of the volcanicity in this region.
PHLEGRAEAN FIELDS – This active location lies within the Campanian Ignimbrite Caldera, which erupted cataclysmically 36,000-37,000 years ago, with smaller eruptions about 38,700 and 24,000 years ago. One of the latest eruption was about 12,000 years ago, but the most recent was from 4800 to 3800 years ago when there were 16 explosive and 4 effusive eruptions. There are many vents – such as Astroni, Spaccata, Gauri and Agno-Monte Spina. They are concentrated at this location and have emitted mainly trachytes and phonolites, often in explosive eruptions that produced extensive ash flows and blankets of pumice. Hydrothermal eruptions at Solfataras and fumaroles have taken place in historical times. In the 1980’s there was considerable vertical elevation in the Pozzuoli area giving rise to fears of an imminent eruption. This has happened several times in the past and the famous Temple of Serapis (actually a Roman market), has been up and down several times, even below sea level! As recorded by the boring of molluscs through the solid pillars, now high and dry.
By Gordon Hensman
Dudley, West Midlands