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Journal of Research and Didactics in Geography (J-READING), 0, 1, Dec., 2012, pp. 25-33
DOI: 10.4458/1005-04
The reduction of volcanic risk in the Neapolitan area
Roberto Scandonea, Lisetta Giacomellia
a
Dipartimento di Matematica e Fisica, Università di “Roma Tre”, Rome, Italy
Email: [email protected]
Received: October 2012 – Accepted: November 2012
Abstract
The Neapolitan area may be affected by the activity of the two volcanoes of Vesuvius and Campi Flegrei.
Contingency plans have been formulated for Vesuvius and should be implemented in case of observations
of anomalous precursory signals. The high population density makes the success of any large scale
evacuation plans unlikely. We revise the effect of past historical eruptions which occurred in the area, and
suggest possible alternative measures that can be taken by individuals also during the course of an eruption.
Keywords: Volcanic Risk, Vesuvius, Campi Flegrei, Eruption
1. Introduction
Volcanic Risk has been defined (Fournier,
1979) as the product
R = Value x Vulnerability x Hazard
where the Value is the total amount of lives
or properties at risk of a volcanic eruption, the
Vulnerability is the percent of value at risk for a
given volcanic event, and the Hazard is the
probability that a given area be interested by a
certain volcanic phenomenology.
The reduction of volcanic risk can be
obtained by diminishing the number of
inhabitants and the properties at risk of a
volcanic eruption. The first objective can be
achieved by evacuation plans that should be
implemented before the imminence of an
eruption. The second objective is more difficult
as it requires a long term planning of the urban
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development of a volcanic area.
The general experience in Italy, as well as in
other parts of the world, has shown that an
increasing number of people, as well as
industrial and urban development are occupying
larger areas exposed to different natural hazards
(Wharton Risk Management and Decision
Processes Center, 2008).
This general tendency is difficult to be
countered as it is driven by strong economic
interests. Furthermore, large numbers of people
living in endangered areas make it difficult to
work out large scale evacuation plans as has
been seen during the Katrina event in New
Orleans (Cigler, 2009).
The Neapolitan area is characterized by a
very high population density (Pesaresi et al.,
2008), and may be affected by the activity of the
active volcanoes of Vesuvius, (Figure 1) and
Italian Association of Geography Teachers
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Roberto Scandone, Lisetta Giacomelli
Campi Flegrei (Figure 2) (Scandone et al.,
1993). Studies on the volcanic hazard of the area
started 40 years ago (Scandone, 1977), but have
been unable to prevent an irregular and massive
urbanization of the area. The large growth of
population after the 50s has resulted in more
than 850,000 people now living in the close
proximities of the two active, but quiescent
volcanoes.
Figure 1. Transverse aerial view of the summit cone of Mt Vesuvius. In the background the settlements on the
flanks of the volcano and the city of Naples.
Photo: Roberto Scandone, Lisetta Giacomelli.
Figure 2. Transverse aerial view of the western area of Napoli (Agnano) within Campi Flegrei. The craters of
Solfatara , (on the right) and Nisida (in the background) were formed in pre-historical time.
Photo: Roberto Scandone, Lisetta Giacomelli.
Copyright© Nuova Cultura
Italian Association of Geography Teachers
Roberto Scandone, Lisetta Giacomelli
In case of volcanic unrest, emergency plans,
available only for Vesuvius, enforce the
evacuation of about 500,000 inhabitants from
the communities surrounding the volcano. Given
the unknown pattern of possible precursors, and
the high number of people that would be
affected by such measures, it is likely that the
pre-planned contingency measures may not
work. There is a similar situation also in the area
of Campi Flegrei with more than 350,000 people
residing in zones that may be affected by
volcanic phenomena.
In this paper we examine several historical
volcanic eruptions in the area and identify some
critical issues that may jeopardize the measures
taken to reduce the impact of volcanic
phenomena.
2. Historical explosive eruptions in the
Neapolitan area and their impact on
human environment
The first problem to understand during a
volcanic crisis is the character of the eruption, as
an effusive event with the emission of lava flows
will affect only the buildings and agricultural
land, but not human life. On the contrary, an
explosive eruption destroys everything around
the volcano up to a distance, depending on the
violence, of 10-25 km. Neapolitan volcanoes
have mixed styles of activity: Campi Flegrei
displays a predominant explosive activity,
whereas Vesuvius has had a predominant
effusive style in the last 300 years, but
predominant explosive activity after long
quiescence periods, like those which preceded
the violent eruptions of 79 A.D., and 1631, or
the present one.
In the following we will examine the three
explosive eruptions that occurred at Vesuvius
and Campi Flegrei after long quiescence periods.
3. The eruption of Vesuvius of 79 A.D.
Vesuvius is a volcano well known for its
devastating eruption during Roman time in 79
A.D., which destroyed the cities of Pompeii and
Herculaneum killing thousands inhabitants
(Giacomelli et al., 2003). Pliny the Younger
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27
described the eruption, and the attempted rescue
of the inhabitants made by his uncle Pliny the
Elder, the admiral of the Roman fleet. The
description closely fits the reconstruction of the
eruption based on the interpretation of volcanic
deposits (Sigurdsson et al., 1985). The eruption
was preceded by earthquakes that lasted for
many days, with several crises occurring also
decades before (Cubellis et al., 2007). The early
phase started at midday of 24 August of 79
A.D., and was characterized by a sustained
eruption plume formed by the eruption of a
mixture of fragmented magma and gas rising to
a height of 24 to 32 kilometers above the crater.
The prevailing stratospheric wind caused the
dispersion of the plume toward SE and the
deposition of a thick layer of pumice with a
thickness of up to 3 meters in Pompeii. It is
likely that, during this phase, the area to the east
of the volcano was in a total darkness.
Herculaneum, to the SW, was relatively less
affected in the early phase. During the night
between the 25 and 26, the violence of the
eruption increased and there was the
emplacement of several pyroclastic flows caused
by the collapse of the eruption plume and the
sliding along the flank of the volcano of a dense
mixture of hot gas, ashes and pumice which
determined the complete destruction of all
buildings, and living creatures within a radius of
10-15 kilometers from the volcano (Figure 3). A
total of about 5 km3 of magma were erupted in
less than 48 hours (Sigurdsson et al., 1985).
In Pompeii, 394 corpses were found in the
pumice fall deposits and 650 in the pyroclastic
flows (Figure 4). About 90% of the first group
were found in houses, and were probably killed
by the collapse of roofs because of the pumice
weight; a smaller number of victims were found
outside of buildings, probably killed by falling
roof slates or by larger rocks thrown out by the
volcano. An equal number of corpses, in the
pyroclastic flows, were found inside and outside
the houses (Giacomelli et al., 2003). A total of
about 1,500 victims was estimated taking into
account also the unburied part of the town. The
total number of people living in Pompeii was
between 10,000 and 20,000 which gives a
percent ranging between 15 and 7.5% of people
who remained in town and were killed by the
eruption.
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Roberto Scandone, Lisetta Giacomelli
Figure 3. The ruins of Pompeii lie at a distance of 8 kilometers from Vesuvius.
Photo: Roberto Scandone, Lisetta Giacomelli.
Such percentages are surprisingly low for
people who did not know that the mountain
above their city was an active volcano or did not
know anything about volcanoes. We do not
know whether those that escaped were killed or
not by the eruption, but however they reacted to
the events and attempted an escape to their fate.
A similar percentage of victims versus total
number of inhabitants is found in Herculaneum
4. The eruption of Monte Nuovo in
Campi Flegrei in 1538
The eruption started on 29 September 1538 after
more than two years of occasional earthquakes
and ground deformation. On the day before the
eruption, the seismic activity dramatically
increased along with the rapid uplift of the
ground, which rapidly dried the beach near the
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Figure 4. Cast of one of the victims of the eruption of
79 A.D. of Vesuvius.
Photo: Roberto Scandone, Lisetta Giacomelli.
site of the eruption (Parascandola, 1947). The
eruption began with explosions driven by the
interaction between the magma and sea-water,
Italian Association of Geography Teachers
Roberto Scandone, Lisetta Giacomelli
and progressed to a typical Strombolian
eruption with mild explosion ejecting scoria
and rapidly building a small cone because of
the accumulation of scoria and cinder, and
forming a new hill (Monte Nuovo). The
eruption lasted several days and caused
destruction in the immediate surrounding of the
eruption site destroying the village of
Tripergola along with a hospital and ten
thermal baths. The seismic activity caused
widespread damage in the nearby city of
Pozzuoli that was almost all leveled to the
ground (Parascandola, 1947). A group of about
15 people, who had climbed the cone during a
period of relative calm on 10 October, was
killed by a sudden explosion.
Most of the people living in Tripergola and
Pozzuoli escaped from the villages in the night
before the eruption, because of the strong
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seismic activity which terrorized everyone. A
testimony reported:
“In the year 1538, in the day of St Jerome (28
September) a big earthquake was felt in the city,
which was shaking up and down, and all the city
revolted and was all evacuated, and everyone
was going to Naples or in the fields and it
seemed as the all world was falling down.
People were running naked, and while I was
running with my wife and children, I saw, in the
proximity of the city doors of Pozzuoli, a lady
named Zizula, wife of master Geronimo
Barbiero, who, vested of only one shirt and
wildly uncombed, was riding a horse like a man,
and everyone was crying and asking the
remissions of sins.
At one hour in the night, a fire vent opened
near the hospital in the place called ‘La fumosa’
in the middle of the sea, ejecting a great amount
Figure 5. The cone of Monte Nuovo was formed during the 1538 eruption of Campi Flegrei, and destroyed the
village of Tripergola. Presently it is completely surrounded by buildings.
Photo: Roberto Scandone, Lisetta Giacomelli.
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Italian Association of Geography Teachers
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Roberto Scandone, Lisetta Giacomelli
of pumices and rocks. Such vent then progressed
toward land and completely destroyed the castle
of Tripergola, which was, then filled with sand
and rocks making a new mountain, as is seen
today (30 July of 1587)”1.
The eruption of Monte Nuovo erupted less
than 0.1 km3 of magma but substantially
changed the morphology of the area and affected
an area in the order of tens of square kilometers
(Figure 5). Overall the eruption may be
classified as a mild explosive eruption.
5. The eruption of Vesuvius in 1631
The great eruption of 1631 is the largest
explosive eruption of Vesuvius since those of 79
A.D., and 472 A.D. It occurred after at least 131
years of quiescence. Large trees covered the
Gran Cono, the cone within the Somma Caldera,
and local people did not remember it being a
volcano. The mountain was called “La
Montagna di Somma” (the Mountain of Somma,
a small town on its northern side).
Several months before the beginning of the
eruption, people near the volcano felt some
earthquakes (Braccini, 1632). They were not
particularly scared because earthquakes from the
nearby Apennine chain were often felt in the
area (a large one had occurred three years before
in Apulia, in 1628). The seismic activity became
more severe in the few days before the eruption.
A violent seismic crisis was felt during the night
between 15 and 16 December 1631.
A strong explosive eruption started in the
morning of 16 December 1631 with a sustained
eruption plume, which dispersed pumice and
ashes to the NE. The paroxysmal occurred on
the following day with the emission of
pyroclastic flows, and mud-flows that destroyed
all the villages in the immediate surrounding of
the volcano. The number of casualties is
reported as 4,000 deaths and a lesser number of
injuries. Besides the overall destruction of
numerous villages and people, also extensive
loss of cattle, and arable land is reported.
The relative large number of casualties
(approximately 10% of the overall population) is
to be ascribed to the poor planning of rescue
operations. Actually in the night before the
eruption, the seismic crisis scared most people in
the vicinity of the volcano and also in Naples
(Figure 6). Most people around the volcano fled
toward Naples, but were forbidden to enter the
city because of fear of the plague. Even if the
order was revoked, and more than 40,000 people
were allowed to enter into Naples, more than
4,000 were reported killed during the major
paroxysmal stage and were engulfed in the
pyroclastic flows (Giuliani, 1632).
1
L’anno 1538 nel giorno di San Geronimo (28
settembre) si sentì in detta città un gran terremoto, il
quale allo spesso pigliava e lasciava, e tutta la città si
mise in rivolta e quasi tutta disabitata, andando a
Napoli e per le campagne chi fuggiva in un luogo, e
chi in un altro e pareva che il mondo volesse
subissare, e la gente fuggiva etiam nuda e fuggendo
esso testimonio coi suoi figli, e sua moglie, ritrovò
alla porta di Pozzuoli una donna nominata Zizula,
moglie di mastro Geronimo Barbiero, la quale andava
in camicia a cavallo di un somiero alla maniera
mascolina scapellata e tutti piangevano e gridavano
misericordia. E come fu verso un'ora in due di notte
uscì una bocca di fuoco vicino al detto ospidale, nel
largo nominato ‘La Fumosa’ da centro mare, e
menava gran moltitudine di pietre pomici e di arena,
e venne detta bocca di fuoco così aperta ad accostarsi
al castello di Tripergola e tutto lo sconquassò, e
rovinò, e poi lo riempì di arena, di pietre e vi fece una
montagna nuova in 24 ore dove in fino ad oggi si
vede” (30 luglio, 1587).
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Figure 6. Drawings of the eruption of Vesuvius of
1631 with people escaping from the volcano crossing
the Maddalena bridge in the proximity of Naples.
Source: Private collection.
It is apparent from the short review of
historical eruptions in Italy occurring after long
periods of quiescence that they caused casualties
Italian Association of Geography Teachers
Roberto Scandone, Lisetta Giacomelli
mostly because of the ignorance of the volcanic
phenomena, and even in this case the casualties
were only a minor fraction of the total
population. Most people had sufficient time to
flee from the area endangered by the volcano
because of the earthquake activity before the
beginning of the eruption. The escape to a
distance of 10 to 15 kilometers from the
volcanoes was sufficient to prevent any loss of
life.
The awareness of precursors and the gradual
buildup of volcanic activity are the reasons why,
also on a planetary scale, volcanic eruptions
have caused a limited number of casualties
unlike earthquakes, tsunamis and floods. In
many cases, the escape from the effect of a
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volcanic eruption has been made also during the
early phase of the activity.
In the last 300 years only a few eruptions
have caused a large number of casualties as
shown in Table 1 (after Blong, 1984, Simkin and
Siebert, 1994). In one case (Tambora), the
eruption was of an extremely large size and
caused extensive damage on a local scale on the
island of Sumbawa, and prolonged climatic
effects on the planetary scale like also the Laki
eruption. The eruptions of Krakatau and Unzen
caused a tsunami that was responsible for the
majority of casualties. The casualties in the
relative lesser magnitude events of Pelée and
Ruiz were caused by an under-evaluation of the
effects of the eruption.
Volcano
Year
Casualties Cause
Laki (Iceland)
1783
Unzen (Japan)
1792
14,524 70% Landslide, 30% Tsunami
Tambora (Indonesia)
1815
92,000 90% Famine
Krakatau (Indonesia)
1883
36,417 90% Tsunami
Pelée (Martinique)
1902
29,025 Pyroclastic Flows
Ruiz (Colombia)
1985
23,080 Mudflows
9,350 Famine
Table 1. Eruptions responsible for the largest number of casualties in the last 300 years 2010.
Source: Scandone and Giacomelli, 1998.
6. Education and planning for a volcanic
emergency
In Italy, the current planning of the
Department of Civil Protection for a volcanic
emergency (available at http://www.protezione
civile.gov.it/jcms/it/view_pde.wp?contentId=PD
E12771 for Vesuvius volcano), is based on the
evacuation of the endangered areas as soon as
the monitoring network detects any unrest which
is likely to lead to an eruption. Unfortunately
there is no specific formula that makes it
possible to work out a realistic threshold above
which an eruption is absolutely certain.
Furthermore, the high number of people living
in the area makes the evacuation order unlikely
to be issued long in advance, because of the
economic costs in case of failure of the forecast.
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Most past and recent examples suggest that clear
signs of an impending eruption may be observed
only in the hours before the outbreak, thus
making any planned, large scale, evacuation
unlikely to succeed. Moreover, the size and
character of an impending eruption are
completely unknown, and, at the moment, there
is no known relationship between the character
of precursors and the character of the following
event if any (explosive or effusive) so there is
great uncertainty as to whether the total
evacuation of the area surrounding the volcano
is necessary or is underestimated.
The current planning has a second major
flaw, as the alleged capability of State Agencies
to deal with disasters generates a false sense of
security in people thus reducing the individual
response to natural hazards, as for example, has
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Roberto Scandone, Lisetta Giacomelli
been observed during the seismic crisis of 2009
at L’Aquila in Abruzzo (Italy). The result of this
has been a growth of the urban settlements in the
volcanic area without any self-control.
For many years scientists have warned the
civil authorities of the potential risk of volcanic
activity in the Neapolitan area, even if in their
efforts they may have over-emphasized the true
relevance of volcanic phenomena, thus creating
a syndrome of an inescapable catastrophe and
the need for strict measures to prevent it.
Planning for emergency should be carried out
by State Agencies, which should clearly state the
real effect of volcanic activity, and the measures
that can be taken by individuals to reduce the
risk. At the same time, the possible failure of
emergency planning has to be presumed, and the
rules for behavior be suggested for individuals
that may find themselves within an area already
affected by volcanic phenomena. This line is far
from being attained, as it requires a specific
preparation not only of citizens, but also of Civil
Protection officials and scientists, with an open
admission of the limits of knowledge regarding
forecasts on natural hazards.
Environmental education in primary and
secondary school may help to overcome this
divide, but it is often difficult to maintain a
balance between the credibility of public
institutions and individual actions, as the two
may sometime conflict, especially during a
crisis.
7. Conclusions
The basic principles that should be conveyed
to the people living in a volcanic area are about
the nature of volcanic phenomena, their effects
and the distance at which they are relevant.
People should have knowledge of the area where
they live and of the necessary measures that
should be taken in case of unrest, not only by the
Civil Protection, but also by individuals. They
should know the forecast limits and be ready to
adopt individual escape measures in case of
failure of prediction.
Preventive measures taken by State Agencies
should convey the clear limits of forecasts
concerning the size of an impending event, the
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duration of precursors and the timing of
evacuation. Alternative plans should allow not
only a mass evacuation of the area before the
eruption, but also the possibility of the total
failure of the planned measures, and the rescue
of a disordered mass of refugees during the early
phases of the eruption.
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Italian Association of Geography Teachers