Ground deformations in active volcanoes are considered precursors of eruptions according to the most tested models; therefore monitoring networks of ground deformations are installed on inhabited dangerous volcanoes. Direct measurements of such deformations are carried out since 1861 when Luigi Palmieri monitored the eruption at Mt. Vesuvius with levelings along the shoreline near the town of Torre del Greco.
Relative sea level changes were measured at Serapeo in Pozzuoli in the middle of 19th century to record soil uplifts which are locally known as bradyseism. To enlarge the time series of data on these phenomena it is necessary to utilize historical and prehistorical informations on the location of shore-line of human settlements. 
As regards the regions of active volcanoes as the Neapolitan one three processes contribute to sea level changes as eustatism, regional tectonics and local intrusive and effusive phenomena. Therefore at the same time the relative sea level should be different at far-away places only few kilometres according to the volcanic activity. In fact eustatic and tectonic processes contribute to sea level changes with very lesser rates than volcanic activity.
The Neapolitan region for its geological history is an excellent laboratory for testing the validation of new paradigms for some natural phenomena

Cubellis, E.

Delizia, I.

Luongo, G.

Obrizzo, F.

Earth-prints Repository


Rend. Online Soc. Geol. It., Vol. 21 (2012), pp. 743-745, 5 figs.  
© Società Geologica Italiana, Roma 2012 
          
 743 
Key words: Bay of Naples, Ground deformations, Human 
settlements, Sea level changes, Neapolitan volcanoes.  
 
Ground deformations (soil uplifts) in active volcanoes are 
considered precursors of eruptions according to the most tested 
models; therefore monitoring networks of ground deformations 
are installed on inhabited dangerous volcanoes. Direct 
measurements of such deformations are carried out since 1861 
when Luigi Palmieri monitored the eruption at Mt. Vesuvius with 
levelings along the shoreline near the town of Torre del Greco. 
Relative sea level changes were measured at Serapeo in Pozzuoli 
in the middle of 19
th
 century to record soil uplifts which are 
locally known as bradyseism. To enlarge the time series of data 
on these phenomena it is necessary to utilize historical and 
prehistorical informations on the location of shore-line of human 
settlements. It is common practice to spread to research on 
earthquakes, tsunamis, eruptions, by analyzing documentary 
fonts  and relics left by ancient peoples. When the historical data 
are poor, to enlarge the time series of events for deeper 
knowledge of the natural history of investigated sites, the 
research is devoted to geological processes and particularly to the 
location of marine terraces in respect to present sea level. 
As regards the regions of active volcanoes as the Neapolitan 
one three processes contribute to sea level changes as eustatism 
(LAMBECK et alii, 2004), regional tectonics and local intrusive 
and effusive phenomena. Therefore at the same time the relative 
sea level should be different at far-away places only few 
kilometres according to the volcanic activity. In fact eustatic and 
tectonic processes contribute to sea level changes with very 
lesser rates than volcanic activity.  
The Neapolitan region for its geological history is an 
excellent laboratory for testing the validation of new paradigms 
for some natural phenomena. The geological structure of the 
Neapolitan area, located in Campania Plain, at the margin of 
Tyrrhenian Basin, is formed by the succession of effusive and 
explosive rocks as lavas and pyroclastic products erupted by 
polygenic and monogenic volcanoes. Moreover this area is 
characterized by shallow seismicity capable to produce high 
intensities in small epicentre areas.   
The whole range of phenomena observed, in particular the 
present  stress field, as is amply shown by seismicity,  recent 
tectonics and chemism of magmas feeding active and recent 
volcanoes can be accounted for in relation to a local mantle 
upwelling, a lithosphere plate bending and subsequent collapse. 
The measure of tectonics contribution to relative sea level 
changes is obtained by the velocity of sedimentation of rocks 
forming Campanian Plain due to tensile processes during 
quaternary time (LUONGO et alii, 1991 a). This value is of about 
1-2 mm/yr in accordance with the results observed in other areas 
characterized by active tectonics. It is 10-10
3
 times less than that 
observed in active volcanoes (Figg.1,2).  
 
 
Fig.1 - Volcanoes of Neapolitan region (Vesuvius, Campi Flegrei, Ischia) located 
in the Campanian Plain, a like-graben structure at the continental margin of 
Italian Peninsula. 
 
Fig.2 - Half Graben structure model for Campanian Plain. The lower block spaces 
are filled by magma intrusion and the upper block spaces by volcanic rocks.   
 
Sea level changes, ground deformations, human settlements in the 
bay of Naples 
ELENA CUBELLIS (*), ILIA DELIZIA (°) GIUSEPPE LUONGO (°), FRANCESCO OBRIZZO (*)  
____________________ 
(*) Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Napoli, 
Osservatorio Vesuviano.  elena.cubellis@ov.ingv.it 
(°) Università degli Studi di Napoli “Federico II”  
86° CONGRESSO SOCIETÀ GEOLOGICA ITALIANA 
18-20 SETTEMBRE 2012, ARCAVACATA DI RENDE (CS) 
 
 
 
744 
Eruptions and earthquakes occurred in the Neapolitan area, 
have produced myths, legends, historical documents, 
archaeological findings.  
The name Campi Flegrei (Fields of fire) of the district 
including the town of Naples with its western suburbs suggests 
that manifestations of volcanism were evident in Ancient Times. 
This area was once a preferred location to the entrance to Hades. 
It is caldera complex, formed by collapse of the ground following 
two giant eruptions (Campanian Ignimbrite, 39 ka and 
Neapolitan Yellow Tuff, 15 ka). Part of the structure is 
submerged to form the Pozzuoli Bay; the landward floor is peak 
marked by tens of volcanic cones (D’ARGENIO et alii, 2004). 
Campi Flegrei attracted special attention during the nineteenth 
century, thanks to the Serapeo, ruined roman market in Pozzuoli, 
which had been submerged by slowly sinking and re-emerged 
from the sea, due to a rapid rising of the land before 1538 Mt. 
Nuovo eruption and the well known 1970-72 and 1982-84 crises 
(Bradyseism) (LYELL, 1872; BERRINO et alii, 1984; LUONGO et 
alii, 1991 b) (Figg.3,4).  
 
 
Fig.3 - View of Macellum (Temple of Serapis) in 1836. Frontispiece of 
“Principles of Geology” by Charles Lyell. 
 
The investigation of submerged roman ruins at many places 
round the bay of Pozzuoli let us to reconstruct the ancient coast 
line which had fallen some meters but it was rising to the present 
level as recorded upon columns of the Macellum (Temple of 
Serapis) by the hollows of the lithodomi in historical times, and 
by geometrical levelings in recent times. In the environs of 
Pozzuoli the land within short distance of the coast terminates in 
a cliff of moderate elevation (30-40 m). It is interpreted as an 
ancient coast line and the inland marine terrace, called “La 
Starza”, evidences a ground inflation which occurred 8-4 ka ago 
(OBRIZZO et alii, 1991). Evidences of the subsidence of the 
Phlegrean area derived also from the investigation on the ancient 
harbours of Puteoli, Avernus, Misenum, Nisida, located at short 
distance one another along the coast of the Bay of Pozzuoli. The 
largest and best known roman breakwater is that of Puteoli, 
called “The bridge of Caligola”. This consist of tall piers which 
must originally have been at a convenient height above the 
surface of water, while they were 1-2 m below it at the beginning 
of XX century (GÜNTER, 1903). Now the piers are concealed 
from view with the new breakwater of the harbour.  
 
 
Fig.4 - Coast line of Campi Flegrei in Roman times. «The discovery that one 
submerged “rock” after another showed clear signs of artificial origin was so 
fascinating, opening as it did a new field for research, that we were led to add to 
our geographical investigation a survey of the sunken antiquities» (GÜNTER, 
1903).  
   
 Vesuvius has acted like a powerful magnet from time 
immemorial, drawing people to settle on the fertile soils (Bronze 
Age), to wonder at the beauty of the landscape as tourists, or to 
undertake scientific investigations. Eruptive activity in Vesuvius 
area dates back about 400 ka according to the stratigraphic and 
radiometric data on volcanic products and paleosoils from the 
borehole drilled down to depth of 2200 m b.s.l. in the southern 
side of the volcano for geothermal exploration. The volcano 
edifice formed only in the last 25 ka when the volcano produced 
at list five large-scale plinian eruptions and smaller scale 
subplinan eruptions. Some archeological relics of the Bronze Age 
in the eastern part of the Campanian Plain are covered by fall 
products of the plinian eruption of 3800 yrs BP, known as 
Avellino eruption. Instead the eruption of 79 AD, is described in 
the letters of Pliny the Young; at present quantitative analysis 
models of the mechanism of this eruption utilize the detailed  
descriptions of Pliny. Before the 79 A.D. eruption Tacitus and 
Seneca wrote about the damage caused by the strong earthquake 
which struck the town of Pompeii and surroundings in A.D. 62 
(CUBELLIS et alii, 2007). In light of recent archaeological and 
epigraphic evidences this earthquake with the subsequent low-
moderate energy seismic swarms have been considered as 
precursors of the A.D. 79 eruption, responsible for the 
destruction of Pompeii and Herculaneum and of the displacement 
of the coast line offshore, of about 400 m, by the occurrence of 
dense pyroclastic currents which reached the sea. 
86° CONGRESSO SOCIETÀ GEOLOGICA ITALIANA 
18-20 SETTEMBRE 2012, ARCAVACATA DI RENDE (CS) 
 
 
 
745 
Archaeological and geological surveys carried out onland and 
offshore between Herculaneum and Pompeii show that at present 
the coast line at the time of 79 AD eruption have sunk of about 4 
m. As the eustatism contributes to this value only for an amount 
of about 1 m, the large part of the subsidence was caused by the 
long term tectonics of Campanian Plain and volcano dynamics 
with uplift before large eruptions and sinking afterwards.  
The island of Ischia was the site of the earliest known Greek 
settlement in Italy. Strabo mentions that Greek colonies 
abandoned the island repeatedly in consequence of the violents of 
the eruptions, earthquakes and tsunamis that took place in 
Pythecusa since the 6
th
 century BC. Pliny the Elder, in his  
Naturalis Historia writes that on the island of Ischia, the earth 
swallowed up a town and that after this catastrophe a lake was 
formed (Lago del Bagno?). This eruption was dated by the 6
th
-5
th
 
century BC pottery remains (BUCHNER, 1986). About historical 
seismicity more comprehensive accounts are available for Ischia 
island since 1228.  
We have considered a possible relationship between volcanic 
activity in the island and large sea level changes during the late 
Quaternary. Eruptions may be triggered by loading and 
unloading the crust owing to change in sea mass. Seven phases of 
activity have been distinguished in the Island since 150 ka B.P. 
Two major activity phases (1 and 7 in fig.5) occurred between 
140 and 123 ka and in the last 18 ka when there was a continuous 
sea level rise of about 130 m and 125 m, respectively. Instead at 
55 ka B.P., when the catastrophic caldera forming Mount 
Epomeo Green Tuff (MEGT) eruption occurred, the sea level 
showed some oscillations up to 50 m (4 in Fig.5). 
  
 
Fig.5 - Late Quaternary sea-level variations (after SHACKLETON, 1987, modified) 
and volcanic activity of Ischia Island since 140 ka B.P.  
 
The caldera depression was filled – at first in sub-aerial and 
subsequently in submarine conditions – by the MEGT and 
pyroclastic deposits of the eruptions occurred in the island 
between 44 and 33 ka B.P. These deposits were involved in an 
uplift process starting between 33 000 and 28 000 years ago, 
forming the Mount Epomeo block. Total uplift, deduced from the 
present height of marine deposits and eustatic variations, is 710 
m on the southern flank and 920–970 m on the northern flank, 
with an average uplift rate of 2.3 and 3 cmyr
−1
 respectively 
(BARRA et alii, 1992; TIBALDI & VEZZOLI, 2004). Today Greek 
and Roman ruins may be observed along the island coast line, 
submerged under the sea. According to archaeologist  the ruins 
have sunk by about 2 m. Geographers comparing 16
th
 century 
and current maps of the island infer coastal subsidence of about 1 
m (FRIEDLAENDER, 1938; CARLINO et alii, 2006).  
 
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Sea level changes, ground deformations, human settlements in the bay of Naples

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Sea level changes, ground deformations, human settlements in the bay of Naples

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