Mount Vesuvio or Mount Vesuvius is one of the most famous volcanoes to exist on earth. In 79 AD, Vesuvius made its first deadly spew and reduced the bustling Pompeii and Ercolano into ashes. In geological terms, Vesuvio is particularly “versatile”, its activity ranging from Hawaiian-style emission of very liquid lava, fountaining and lava lakes, over Strombolian and Vulcanian activity to violently explosive, Plinian events that produce pyroclastic flows and surges.
The following article on Mount Vesuvius is courtesy of Boris Behncke's,:
"Italy's Volcanoes: The Cradle of Volcanology" Web site.
The interesting aspect of Vesuvio's eminence among Earth's volcanoes is the dense population surrounding it and its climb to higher slopes every year. Half a million people live in a near-continuous belt of towns and villages around the volcano, in the zone immediately threatened by future eruptions.
The situation is still more peculiar as Vesuvio is not the only volcano looming above that area and its people - there is, on the other side of the city of Napoli (Naples), the caldera of Campi Flegrei, renowned for some cataclysmic ash-flow forming eruptions in the all-too-recent geologic past and signs of unrest during the past three decades.
There is also the historically active volcanic complex of Ischia, not threatening to Vesuvio inhabitants but to those on Ischia island itself. To be able to complete this ensemble of geologic hazards, the area forms the nucleus of a much vaster zone that is seismically vulnerable; its most recent disastrous earthquake, on 23 November 1980, killed more than 3,000 people.
Amidst an enchanting landscape with beautiful islands, magnificent mountain ranges, marvellous coasts and historically famed cities, Vesuvio is the focal point, lying in the center of a plain in the Gulf of Napoli. It's steepness, the abrupt way it rises from its placid surroundings, that render it so impressive. It is the imagination of how that thing must have looked like when it was erupting and how it must have been to those living close to it that give it such a feel of power.
The last eruption was in 1944. Since then, the population in the immediate surroundings has had a very great increase. Take the bus up to the “quota mille” (the terminus that is 1000 meters elevation on the historically active cone) from Ercolano or Torre del Greco, and for the first 25 minutes, you don't get out of the sea of houses. Upwards, the homes get more and more luxurious, accompanied by tens and more tens of hotels and pensioni.
After being stricken by the massive way the volcano dominates that area, the second surprise is how green it is. Reforestation has been carried out vigorously in the 50 plus years since the most recent eruption. Even the lava flow of 1944 on the caldera floor of Atrio del Cavallo, still barren in most places and still a distinct reminder of the volcano's potential, carries small trees that have appeared only during the past few years. Small trees are even beginning to grow within the crater, and parts of the crater rim have a cover of green grass.
Preparing for the Next Eruption
Preventing a disaster of such dimensions that would baffle all imagination depends essentially on the occurrence of premonitory phenomena, their correct interpretation, timely warnings and evacuations. The latter steps in turn depend heavily on contingency planning and smooth and accurate communication between scientists, authorities, and the public. The issue of mitigating volcanic desasters has been widely publicized in the past decade, and there have been major achievements which resulted in successful warnings and evacuations at Pinatubo in 1991 and Rabaul in 1994.
In the case of Mount Vesuvio, the issue seems to be more complex, though. First, Vesuvio is far more densely populated than any other volcano on Earth, and the area around it is a major economic and cultural center. Second, communication in an emergency situation would involve many more, and possibly in part counter-acting, groups of people than in the cases named above, as well as the media.
Starting with premonitory phenomena, there seems to be a certain likelihood that an imminent eruption could be foreseen and be warned of. The major historical eruptions of Mount Vesuvio have been preceded by increased seismicity and other phenomena which, given the updated and sophisticated monitoring equipment now installed on the volcano, would surely be well registered. However, not all such "premonitory phenomena" are necessarily followed by eruptive activity. It would therefore be difficult for the scientists monitoring such phenomena to decide whether they are genuine forerunners of eruption or not. Certainly, the extreme danger from any eruption at Mount Vesuvio would justify an alarm even in the case of doubt. However, a false alarm and evacuation without an eruption would have severe consequences, first regarding the credibility of the volcanologists (and authorities), and second, socioeconomic.
The disruption of business and social life and the displacement of hundreds of thousands of people for a period of undetermined duration would probably cause ravaging controversies all across the country. Worse, in the case of another alarm, maybe only a few years after the first, false one, volcanologists would encounter much more difficulty to convince the authorities, which in turn would encounter similar problems convincing the public. In other words, would anyone leave after a false alarm?
The same question applies, though, for the case of a warning without a preceding false alarm. Logistically, the evacuation of at least 600,000 people would be a problem almost impossible to solve even in an industrialized country like Italy. A plan prepared recently by a special commission, contingency plan, inother words, of scientists assumed that warning could be given up to 20 days before an eruption (see a news article taken from Nature).
The commission further assumed that 600,000 people could be evacuated within a week, using trains and buses. Who ever has been in the Napoli area or has even only used trains or buses anywhere in Italy will probably imagine that this would be an extremely difficult task.