Naples, the Vesuvius and the Phlegraean Fields: ...di Malko

The islands flegree

                              Naples, the Vesuvius and the Phlegraean Fields

The province of Naples is characterised by the three volcanic complexes of the Vesuvius, the Phlegraean Fields and the island of Ischia. Despite their closeness to each other, each of them has completely different characteristics as well as dissimilar form and extention.

The Vesuvius, the most famous of the three, easily recognisable by its distinctive shape and profile, gave rise to the most famous eruption in history. In 79 AD a plinian explosive eruption buried  the cities of Pompeii and Herculaneum thus providing us with a significant part of the world’s archaeological heritage. This was, however, only one of many eruptions the last of which took place in 1944.

The  island of Ischia is the upper part of a submarine volcano. About 55,000 years ago a violent explosive eruption took place known as the green tuff stone of Epomeo; the most important in terms of intensity and morphological transformation, its violence created a caldera which was invaded by the sea and later filled with the accumulation of piroclastic material that erupted from numerous eruptive vents on the island. 

Mount Epomeo is not a volcano but rather a sort of tuff stone column pushed up by the magma beneath. At an altitude of 787 metres, it is the highest point on the island. On the eastern side of its base are  numerous eruptive centres, the product of past effusive and explosive activity that has often taken place after long periods of quiescence. The last eruption was that of the Arso which took place in 1302 AD. Today, the island has important hydrothermal and fumarolic activity which is the manifestation of an uncalmed activity beneath the ground. A few years ago a loud rumble on the side of Forio caused alarm but it turned out to be only a vapour jet which had been suddenly released from beneath the hillside. 

Tuff stone is easily eroded by the elements – wind, sun and water. This explains the vast number of boulders balanced precariously on the steep slopes of Monte Epomeo. An earthquake could easily shake the ground and cause them to tumble down the mountain. Amazingly enough, one of the biggest of these did fall down in the past and was then chiselled and sculpted into a house which is now inhabited.

Monte Nuovo (1538)

The Phlegraean Fields are a particularly complex and extensive volcanic area with numerous eruptive centres. One of the most violent eruptions, the Campanian Ignimbrite, took place about 39,000 years ago while the Neapolitan Yellow Tuff Stone eruption took place 15,000 years ago. The most recent eruption was that of 1538 which in a week formed Monte Nuovo, destroying a village and transforming the landscape around it.

Classical iconography has always associated Naples with the Vesuvius. However the city’s real volcano is the Phlegraean Fields whose yellow tuff stone, the product of numerous eruptions over the centuries and millenia, lies beneath it. The construction of the city over the centuries has been characterised by the use of yellow tuff stone dug out from open air quarries, underground galleries and frequently even dug out in vertical shafts beneath the building that was then built with the extracted stone. This technique of stone extraction created large underground cavities which after being plastered served as cisterns for collecting rain water (see figure on the left). The subsoil is consequently riddled with cisterns and shafts which in the Greek and Roman period had already given rise to aqueducts with flowing water.

Cava sotterranea di tufo giallo appena scoperta
in località Piscinola (NA)

This incredible network of water canals, cisterns and wells which reached courtyards, and stairwells within houses needed maintenance from workers called the ‘pozzari’. To work in such narrow spaces they needed to be of small stature. They wore a light covering of sacking as protection from the cold and as protection for their clothes which would otherwise have been torn by scraping against the stone walls of the narrow shafts. It is likely that the figure of the ‘pozzaro’ gave rise to the legend of the ‘monaciello’ the ethereal child, generous if  at times also mischievous, so beloved by Neapolitans. The ‘monaciello’ however, is found not only in Neapolitan folk tradition but all along the Sorrento coast where there are also banks of tuff stone that have been perforated with shafts and  wells. And so we always leave a little piece of bread on the table after dinner for him…

The grey tuff stone of  Sorrento was produced by the fall of pyroclastic material from the Phlegraean Ignimbrite eruption (Archiflegreo). Surface lithoid banks are visible, above all, in cliffs overlooking the sea. Caves dug out over the centuries to extract stone for building and used as shelters or boat yards (monazeni) can also still be seen from the sea.

The figure above shows the "eye of the mountain", the initial, circular part that is dug out, widening as it descends, forming a bell shape. Stairs cut into the stone walls are also visible with signs of soot left by oil lamps.

Tratto dell'acquedotto romano sotterraneo che adduce a una
 cisterna  in zona Chiatamone (NA)

The photo on the left shows a branch of the aqueduct. In the foreground the base of the water canal in the shape of an upside down rectangle is plastered to protect it from  free flowing water (tuff stone is not impermeable) From canal to canal and cistern to cistern, the water network served the entire city. During the Greek and Roman periods the aqueduct, known as the Bolla, was second longest only to that of ancient Carthage. 

In 1629 Don Cesare Carmignano, assistant to the engineer Alessandro Ciminello, designed the enlargement of the aqueduct, by now inadequate to satisfy the increasing needs of the city. He provided it with new waters extracted from Sant'Agata dei Goti in the Benevento area. Known as the Carmignano after its planner, it remained in use until 1885 after which it was closed up following the numerous epidemies that hit the city.

The tuff stone, literally showered on the city by explosive volcanic eruptions together with lapilli and pozzolana were to be irreplaceable building materials while the incomparably fertile soils still provide nourishment for precious vines, fruit trees and tomatoes. Tuff stone has been transformed into tombs, cisterns, temples, castles, cathedrals and aqueducts. It has served to build city walls and fortifications. In the Second World War the subsoil of Naples was used for air raid shelters which saved the lives of hundreds of people.

The salubriousness of the Phlegraean Fields and the fertility of its soil still make it, together with the Bay of Naples a desirable destination for a cultured tourism that wishes to relive the splendours of Roman civilisation.

Neapolitans live out a strange relationship with their volcanoes, debateable and illogical, but also romantic and fatalistic. A bond that today is particularly difficult, given the excessive increase in population that instead of proliferating far from eruptive vents has created a demographic stranglehold around them. Like living in front of a cannon barrel; safety will depend on the length of the fuse and how early on we will be able to see the spark!

Translation: by Lisa Norall

The Phlegraean Fields Deep Drilling Project: interview with Prof. G. Mastrolorenzo

Bagnoli - Campi Flegrei

 

"The Phlegraean Fields Deep Drilling Project: interview with

Professor Giuseppe Mastrolorenzo" by MalKo

 

There has recently been apprehensive discussion of the scientific proposal for the Deep Drilling Project.  This is a probe which would be pushed to four kilometres depth  in the area of the ex-Italsider of Bagnoli.  It would begin with a “pilot” well of five hundred metres that would then advance lower down at a certain slant.

Several important scientific journals and numerous scientists have warned against drilling in a caldera that forms part of an active volcanic area since it could cause eruptions and earthquakes.  On the other hand, an equal number of prestigious scientists from the national and international scientific world believe that the drilling would not set off any reactions and on the contrary could result in the discovery of new elements useful for understanding eruptive dynamics and the phenomenon of bradisism typical of the area.  Considering that the densely populated area is located in and around the city of Naples, there are fears that another eruption would add immeasurably to the already innumerable problems that beset the city.

The uninitiated obviously ask themselves what dynamics the drilling could trigger off.  None of the scientific articles we have gone through talk about the scientific and technical details at the basis of the fears but leap immediately to the conclusions: alarm yes or no?!

We think that the problem is considerably more complex than just the pricking of a balloon… and could perhaps be similar to a B.L.E.V.E. (Boiling Liquid Expanding Vapor Explosion), a phenomenon known above all to firemen, because of the high accident rate in industry and transport.  This type of explosion takes place in confined spaces containing superheated liquids.  The substance passes so rapidly to a vapor state by means of the reduction in pressure caused by the physical breakdown of the casing, that it sets off a shock wave.  We also know, however, that the reaching of critical pressure and temperature in many substances such as water brings the entire mass to a state of total vapor at enormous temperatures.  For other thermodynamic concepts, however, it should be remembered that perforating the cylinder (of an engine) with a hole of a tiny section would not automatically cause a hiss in the jet equal to the maximum pressure created in the cylinder itself as an effect of the explosion of the combustible.  There, however, the pressures at play are cyclical.

Professor Mastrolorenzo, this story of the drilling of the Phlegaean Fields is extremely complex, above all regarding the alarm over the risk of explosion…

The physics of  gas or vapor explosions in volcanic areas (gas and steam-blast eruptions) is amply covered in the scientific literature.  Simple calculations of the energy balance lead to worrying conclusions about the high energy in play and the unpredictability of systems such as the geothermic system in the Phlegraean Fields which is highly unhomogeneous in petrographic and chemical-physical terms, both horizontally and vertically and explored only indirectly by means of indirect investigation.
Thus the behavior of the system, in the case of the application of an external disturbance such as drilling, is intrinsically unpredictable.  There is a simplistic tendency to retain that there is always a proportion between the energy applied to a system and the modifications observed: but it is not always so.  In certain systems, and the drilling may belong to this category, small stresses can produce enormous effects.
In volcanology and geophysics, one of the problems of greatest interest is the propagation of the fracturation processes in relation to mechanical and thermal applied stress.  In the case of volcanoes, there is still no universally valid theory that explains how an eruption begins, but undoubtedly the triggering off of the fracturing of the crust surface represents the first stage in the rising of the magma towards the surface.
In the past I discussed the problem of thermal fluid dynamics in the Phlegraean Fields and I pointed out the danger of fluids in critical or super critical conditions in porous rock that could potentially trigger freatic explosions or explosive eruptions. Such risks should obviously not be undervalued.

Given that the project is international, why the Phlegraean Fields?

The Phlegraean Fields were proposed several years ago by Dr Giuseppe De Natale of the INGV as it is an active volcanic area of particular scientific interest due to its significant danger as well as well as being potentially suitable for the installation of geothermal power stations.  The project discussed within the ICDP of 2009 was approved with partial financing from the INGV.  The beginning of the drilling,  postponed serveral times, was planned for last October but was suspended after the alarm launched at an international level about the risks connected to deep drilling in a highly densely populated area at high seismic and volcanic risk.  The Mayor of Naples, Rosa Russo Iervolino ordered the suspension of the project and sent a request to the Department of Civil Protection for an evaluation of the danger related to the experiment.  Last October, at a meeting in Rome the Department approved further investigation into its safety by a commission of experts before authorisation for the drilling could  be released.  Since then, all activity has ceased.

Was the area of Bagnoli chosen because of its available space?

The choice of the area of Bagnoli as the operative seat for the deep drilling project was proposed early on.  The area falls within the industrial perimeter of the ex ILVA plant which is at present being reclaimed by theBagnoli futura consortium. Geologically, it lies on the south-eastern border of the Phlegraean caldera delimited by the hill of Posillipo.

Although the project is international there are also international alarms about a possible resumption of eruptions and earthquakes set off by the deep drilling…

The alarm launched by researchers in various international scientific journals, the Italian and foreign press and in parliamentary questions concerns the seismic and volcanic risks that the drilling operation could create when the drills go through the hydrothermal system at very high temperatures and pressures.  The risk of triggering eruptions in the event of crossing through superficial magmatic reservoirs has also been pointed out and recent research has theorised the possible injection of magma at shallow depths during recent bradisism crises.
Another risk of drilling could derive from polluting agents, leftover or reworked, that have been lying in the subsoil since the steel and eternit plants of Bagnoli were closed twenty years ago.
There has also been substantial criticism over the construction of industrial plants for the exploitation of geothermal energy in an area whose urban development plan is based on research, culture and recreation.

The director of the project, Dr Giuseppe De Naple, guarantees that there will be no danger because the project will proceed in phases. Is this procedure a real guarantee?

The situation has proven to be very complex because of the coexistence of scientific, management and administrative problems.
Although, according to those responsible for the project, the risks are minor, an evaluation carried out by independent scientific authorities has been held to be indispensable.  But it has also been emphasised that the Department of Civil Protection consulted by the Mayor of Naples, could not carry out its role of privileged interlocutor given that by statute it makes use of the consultancy of the INGV which is the board that has proposed the project.
Infact, the administrative excursus on the deep drilling plan highlighted the complexities involved in relation to the assumption of responsability in the case of scientific projects or other types of intervention in areas where the population is at risk.  In reality, any deep drilling presents a certain level of risk, since it passes through systems of extremely high energy at pressures that can reach thousands of atmospheres along with temperature of hundreds of degrees as well as the presence of fluids that can also be magmatic and whose behavior is highly unpredictable.  On this subject, it is enough to recall the recent ecological disaster in the Gulf of Mexico where the undervaluation of risk had serious consequences arising from the unstoppable flow of oil from the sea bed causing massive damage to the marine and coastal environments which were scourged by the oil slicks.  The accident was caused by the inadequate technology used which probably resulted in a superficial evaluation of the risks, despite the drilling being carried out by one of the largest international industrial giants in the field.  Nevertheless, provided that there is an adequate evaluation of the risks and benefits that must be understood and accepted by the community, deep drilling can be justified as a source of further scientific information if this is not available by other means.
In reality, deep drilling in the Phlegaean Fields has been carried out since the fascist period to a depth of 3200  metres by the AGIP company.
As has been pointed by some of the researchers most critical of the drilling project in Bagnoli, this precedent renders the present project uninnovative and superfluous to any further investigation, whether related to scientific aims or the exploitation of geothermal energy.  Indeed, during the AGIP campaign imminent risks caused the rapid closure of the wells and interest in the potential for the exploitation of geothermal energy faded due to the analyses showing the subterranean fluids to be too saline.  In compensation, however, detailed information about the geological characteristics of the subsoil was obtained by means of the probing.
It is evident that times have changed together with the sensitivity relating to natural and man-made risks.  Scientists, the authorities and the population at large have by now an awareness of their right to security and it is therefore not possible to operate in a territory without giving sufficient information about the risks deriving from a particular activity even if this affects research.
The fundamental problem now in the risk management of the Phlegraean Fields is the lack of an emergency plan.  It is clear that the Civil Protection or any other authority, in the absence of any preventive evaluation of possible events and therefore of emergency plans for seismic, volcanic or environmental risk, would not be able to approve an operation presenting such risks.
At the present, there is only a risk plan concerning volcanic eruption; but despite being announced twenty years ago it is still being studied by the national commission appointed by the Department of Civil Protection. I have urged on numerous occasions, without response, that the emergency plan be made public together with the studies on the drilling project in Bagnoli in the wake of recent alarms.  There is high risk in the area of the Phlegraean Fields, as shown in our maps of volcanological danger that delineate the various possible eruptive scenarios.  These maps should be the basis for the drawing up of an emergency plan.

(As always, our thanks to Professor Giuseppe Mastrolorenzo for his kind collaboration on matters of scientific interest that are not only complex but very relevant today)

In concluding this article, we would like to add a couple of points: first of all we are well aware that a degree of risk is always inherent in man’s activities.  However, if we take for example the conquest of space, it began with the launch of teleguided missiles, followed by rockets carrying monkeys and dogs and finally man (human life) which is the highest form of life to be protected.  What do we mean by this: that where unknowns fill important spaces that we need to protect, caution should be the rule of our modus operandi.Whoever is moderately familiar with problems of security knows that an operation of this kind could lead to situations if not of alarm, of pre-alarm.  In other words, it could be necessary to activate dispositions in the emergency plan without an emergency appearing in its maximum form in energy terms as we know that unknowns do exist.  This might simply be a precautionary measure, given that the perforation of a vapor sack could produce a loud boom or a bright fumarole which though probably innocuous could panic an already deeply worried population.  Obviously, this is just an example to help us understand the situation, even if drilling technology is by now highly sophisticated.
Deep drilling in the area of the Phlegraean caldera, which will certainly be furiously debated in the near future, should be approached in the spirit of prevention given that prediction is not possible.  Prevention entails techniques to mitigate risk, moderating the danger or the value of exposure (the inhabitants) or both.  In this case the minimisation of the danger would consist in employing recognitive and drilling techniques capable of choosing a path and containing the maximum theoretical pressures, and if necessary of remedying the situation.  It is more difficult, however, to predict the fracturation of the crust deep down.  In other words the experiment would have to be able to back out in useful terms if the results should become increasingly discouraging.
Just to clarify certain concepts, it is enough to think that industries at risk are obliged to produce an emergency plan inside and outside the plant including the procedures to spread the alarm.  If we remember well, the drilling activities are regulated by the directives relating to the safety and health of workers in the industries that extract by drilling according to the dictates of D.M. 25 novembre n°624, actuated in the directive 92/91/CEE, published in the Gazzetta Ufficiale 14 dicembre 1996.  These dispositions offer an excellent departure point for understanding the problems.
In the last analysis, scientific research should not be stopped, but the risks must always be measured with the available alternatives.  To explore a caldera is of great importance but the Phlegraean caldera should be taken into consideration only if there are no other calderas in the world located in deserts or other areas of low density population.  Infact, by lowering the exposure value, the risk immediately re-enters within acceptable parameters.

Translation by Lisa Norall

(In the figures below the two danger maps drawn up for the Phlegraean Fields by Professor G. Mastrolorenzo and collaborators)

The danger map relative to the dynamical overpressure represents the pressure exerted by a burning cloud on the unity of the surface.  Damage relevant to the structure begins at values above 5 kPa while the value of demolition goes from 10 kPa to 25 kPa depending on the building typology.

Other than the risk connected to pressure is the great danger associated with the high temperature of the clouds (up to 600°C) which they can maintain even at distances greater than 15 kilometres from the eruptive centre.

The map on the left shows the danger relative to the fallout, that is to say the deposits that fall back down.  It is evident that for such a type of phenomenon the entire city of Naples would be exposed to a very high risk value.

Both the maps are the result of the combinations of all the events possible obtained by the numerical simulation of thousands of eruptive episodes with diverse properties and probability values.