Content uploaded by Roberto Santacroce
Author content
All content in this area was uploaded by Roberto Santacroce on Feb 25, 2015
Content may be subject to copyright.
Bull Volcanol (1999) 60: 207–222 Q Springer-Verlag 1999
ORIGINAL PAPER
R. Cioni 7 R. Santacroce 7 A. Sbrana
Pyroclastic deposits as a guide for reconstructing the multi-stage
evolution of the Somma-Vesuvius Caldera
Received: 24 November 1997 / Accepted: 23 March 1999
Editorial responsibility: S. Carey
Raffaello Cioni (Y) 7 Roberto Santacroce 7 Alessandro Sbrana
Dipartimento di Scienze della Terra, Università degli Studi di
Pisa, Via S. Maria 53, I-56126 Pisa, Italy
e-mail: cionidst.unipi.it,
Fax: c39-50 500675
Abstract The evolution of the Somma-Vesuvius cal-
dera has been reconstructed based on geomorphic ob-
servations, detailed stratigraphic studies, and the distri-
bution and facies variations of pyroclastic and epiclastic
deposits produced by the past 20,000 years of volcanic
activity. The present caldera is a multicyclic, nested
structure related to the emptying of large, shallow res-
ervoirs during Plinian eruptions. The caldera cuts a
stratovolcano whose original summit was at
1600–1900 m elevation, approximately 500 m north of
the present crater. Four caldera-forming events have
been recognized, each occurring during major Plinian
eruptions (18,300 BP “Pomici di Base”, 8000 BP “Mer-
cato Pumice”, 3400 BP “Avellino Pumice” and AD 79
“Pompeii Pumice”). The timing of each caldera col-
lapse is defined by peculiar “collapse-marking” deposi-
ts, characterized by large amounts of lithic clasts from
the outer margins of the magma chamber and its apo-
physis as well as from the shallow volcanic and sedi-
mentary units. In proximal sites the deposits consist of
coarse breccias resulting from emplacement of either
dense pyroclastic flows (Pomici di Base and Pompeii
eruptions) or fall layers (Avellino eruption). During
each caldera collapse, the destabilization of the shallow
magmatic system induced decompression of hydrother-
mal–magmatic and hydrothermal fluids hosted in the
wall rocks. This process, and the magma–ground water
interaction triggered by the fracturing of the thick Me-
sozoic carbonate basement hosting the aquifer system,
strongly enhanced the explosivity of the eruptions.
Key words Caldera 7 Pyroclastic deposits 7
Depositional facies 7 Plinian eruptions 7 Vesuvius
Introduction
The Somma-Vesuvius volcanic complex consists of an
older volcano dissected by a summit caldera, Monte
Somma, and a recent cone, Vesuvius, which grew with-
in the caldera after the AD 79 “Pompeii” eruption
(Fig. 1). The original Roman name Vesuvius (or Ves-
bius) was applied to the old volcano. Starting from the
fifth century, chroniclers make mention of Mt. Somma,
as the highest (“summa”) peak of the mountain which,
at that time, referred to the older cone (M. Pagano,
pers. commun.). The new cone grew discontinuously
(with minor summit collapses) during periods of open-
conduit, persistent activity (both strombolian and effu-
sive). A combination of field and historical data indi-
cates that these periods occurred in the first to third
centuries, in the fifth to eighth centuries (after the AD
472 “Pollena” eruption), in the tenth to twelfth centu-
ries, and in 1631–1944 (Andronico et al. 1995).
Somma-type calderas are generally described as sub-
circular structures having a younger cone in their inter-
iors (Simkin and Siebert 1994). According to Williams
and McBirney (1979), the Somma-Vesuvius caldera
(SVC) is an example of a “Krakatoan” caldera, formed
by “the foundering of the top of large composite volca-
noes following explosive eruptions of siliceous pumice
from one or more vents, or in some instances, from ar-
cuate fissures on the flanks”. Until relatively recent
times, the formation of SVC was ascribed to the Pom-
peii eruption (Rittmann 1967; Macdonald 1972; Bullard
1978; Williams and McBirney 1979; Ollier 1988). The
Roman paintings from Pompeii and Herculaneum
prompted Stothers and Rampino (1983) to conclude
that, prior to AD 79, the top of the volcano was asym-
metrically shaped, indicating that a Somma-type cal-
dera was already present. The volcanologic interpreta-
tion of a Roman fresco from Pompeii (Nazzaro 1997)
leaves few doubts about the presence of a pre-existing
caldera (Fig. 2).
Lirer et al. (1973) first suggested the possibility that
the structure could have resulted from several vertical
208
Fig. 1 The Vesuvius cone and the caldera. View from south–
southwest
collapses. Delibrias et al. (1979), having recognized sev-
eral pyroclastic sequences potentially compatible with
caldera-forming Plinian eruptions, proposed a poly-
phased formation of the caldera but without a detailed
discussion. They suggested that the first collapse of the
SVC occurred during the “Pomici di Base” Plinian
eruption, recently re-dated at approximately
18,300B180 years BP (Andronico et al. 1995; Bertag-
nini et al. 1998). Walker (1984) reported SVC as an ex-
ample of a structure formed through repeated collapses
connected to medium-sized Plinian eruptions (namely
the Mercato, Avellino and Pompeii). The asymmetric
shape of the SVC, at first glance, suggests the possible
occurrence of a lateral collapse, as was postulated by
Milia et al. (1998) as the “probable” (even if totally un-
constrained) mechanism of its formation. Actually no
trace, either geologic or geophysical, has thus far been
found, on land or below the sea, of a “catastrophic
landslide ... producing the breached crater and a chaot-
ic landscape that extendted into Naples Bay” (Milia et
al. 1998). In any case the geologic data rule out that the
SVC is a “breached crater”.
This paper reconstructs the multi-stage evolution of
the SVC through the identification and timing of the
events that recurrently induced vertical collapses. The
database consists of: (a) geomorphic observations from
field surveys, topographic maps, and aerial and Landsat
images; (b) detailed stratigraphic reconstructions of the
eruptive sequences of the main Plinian-type, “caldera-
forming” eruptions; and (c) areal distribution and lat-
eral and vertical facies variations of deposits, in particu-
lar those proximal units likely to be closely related to
caldera collapse (i.e., breccias and proximal phreato-
magmatic deposits).
Morphology of the Somma-Vesuvius caldera
The SVC has a lobate, quasi-elliptical shape with a 5-
km-long, east–west major axis (Fig. 3). The northern
rim of the caldera is a well-defined steep wall, reaching
from the “Cognoli di Levante” in the east to “Cognoli
di Giacca” in the west, with an average elevation of ap-
Fig. 2 Fresco from Pompeii (now at ”Museo Archeologico Na-
zionale“ in Naples) showing the Somma-Vesuvius caldera on the
background of a mythological picture (love of Venus and Mars).
Modified from Nazzaro (1997). The inset indicates the shape of
Vesuvius prior to AD 79. Note the truncation of the volcano and
the absence of an intracaldera cone. A deep notch probably cut
the southeastern caldera rim, showing the stratified structure of
the Mt. Somma caldera wall
209
Fig. 3 a Landsat image of Somma-Vesuvius volcanic complex
with trace of the morphologic rims of the caldera; b location
map SommaV.
Pollena
1000
800
Sant'Anastasia
Vesuvius
North
projection of the
inferred apex of
the old cone
1000 m
contour line
of a perfectly
cone-shaped
old cone
200 m
contour line
of a perfectly
cone-shaped
old cone
trace of the oldest caldera collapse
Pollena fan
Sant'Anastasia
fan
1000
Sebastiano
San
Cognoli di
Sant'Anastasia
Sant'Anastasia
2 km01
Vesuvius B
A
A
B
Observatory Hill
1600 a.s.l.
1200
800
400
Fig. 4 The convergence point of straight axes (large white ar-
rows) of the modern drainage, and the semicircular 1000-m con-
tour line, allow the localization of the apex of the old volcano
proximately 1000 m. Two main arcuate lobes can be
distinguished. The western arc (A–B in Fig. 3) delimits
the Fosso della Vetrana to the north and can be traced
westward down to an altitude of approximately 600 m.
Its southward extrapolation, mantled by lava flows, in-
tersects Observatory Hill. The radius of the A–B arc is
approximately 1.5 km. The smooth mature morphology
of Monte Somma north of Fosso della Vetrana, with an
anastomosing, centripetal drainage pattern mainly cut
in pyroclastic units, characterizes the oldest portion of
the caldera structure. The drainage pattern of the high-
est portions of the volcano, unaffected by conspicuous
deposition of recent products, is clearly radial (Fig. 4).
Assuming a symmetrical original cone, the size of the
ancient Mt. Somma can be constrained by the point of
convergence of the drainage axes as well as by the sem-
icircular contour lines of the outer caldera rim (e.g.,
1000-m contour line in Fig. 4). In this way the apex of
the old volcano can be roughly located at 1900 m eleva-
tion approximately 500 m north of the present Vesuvius
crater. On such an old cone, the A–B segment of the
caldera rim (Figs. 3, 4) represents the remnant of a col-
lapse centered on the western slopes of the volcano.
This resulted in a strongly asymmetric profile of the
caldera, with a seaward rim much lower than the north-
eastern one.
The central portion of Mt. Somma ridge forms the
main lobe of the caldera, extending from Cognoli di
Trocchia to Cognoli di Levante (B–C in Fig. 3). The
subvertical wall, 150 m high, shows a lobate, scalloped
shape due to differential erosion between dyke crags.
The wall is also affected by frequent slides, as indicated
by scree fans at its foot (Ventura et al. 1995). In this
sector the morphology of the outer slopes of Mt. Som-
210
Ercolano
T. del Greco
Ottaviano
Somma Vesuviana
S.Anastasia
012 km
Rione Trieste
Pollena
1000
800
600
200
S.Giuseppe
Vesuviano
S. Sebastiano
21°
14°
7°
0°
Angle of
slope
N
400
28°
Fig. 5 Map of the angle of slope. The position of the southern
rim of the caldera is well indicated by a clear break in slope
Fig. 6 Engraving of eighteenth century (Giuseppe Aloja). The
southern rim of the caldera is clearly visible in the foreground,
with Vesuvius inside
ma is characterized by deep erosion of the pyroclastic
cover. The radial drainage pattern reveals an elliptical
shape of the stratovolcano, due to moderate northeast-
ward accretion related to an alignment of parasitic
cones along a northeast-trending fracture (Fig. 3).
A third main lobe of the caldera structure runs from
the Cognoli di Levante to the southeastern tip of Piano
delle Ginestre (C–D in Fig. 3), with a larger radius of
curvature than the B–C arc. The southern part of this
lobe is well shown by a morphologic feature, a sharp
increase in the slope of the mountain below a mean el-
evation of around 600 m (Fig. 5). Here the structure is
covered by a pile of recent lava flows and pyroclastic
deposits that, after filling the caldera, overtopped its
lowest rim. The overflowing of the southern caldera
rim probably occurred in the Middle Ages, around AD
1000, when thick lava flows flooded the southwestern
and southeastern sectors of the plain. These lava flows
crop out at Villa Inglese Quarry, 5 km southeast of
Torre del Greco, and in the area just northwest of Ter-
zigno (Arnò et al. 1987). However, in the eighteenth
century the rim was still sharply defined (Fig. 6).
The semielliptical arc delimitating the flat morpho-
logy of Piano delle Ginestre lava field (D–E in Fig. 3)
completes the multilobate shape of the SVC. This
structure forms an acute angle with the southern rim of
the caldera and appears to be linked to the crescent-
shaped relief of Observatory Hill, which forms the
northern tip of the arc. The Piano delle Ginestre there-
fore seems nested within the continuation of the A–B
lobe of the caldera. It appears as a filled depression
bounded by a “constructional” edge, which induces
asymmetric growth of the volcano toward the sea. The
outer slopes of this edge consist mostly of nonwelded
pyroclastic deposits with a parasoil-ribbing erosional
pattern still exposed in the south (Cappella Bianchini
rampart; Fig. 3). The present flat morphology of the
Piano delle Ginestre records the filling of the old de-
pression by historical lava flows that overflowed the
seaward rim in 1694–1697 (Santacroce 1987).
Plinian eruptions and caldera collapses
The deposits of four main Plinian eruptions are present
in the SVC volcanic successions: the “Pomici di Base”
(18,000 years BP); the “Mercato Pumice” (8000 years
BP); the “Avellino Pumice” (3400 years BP); and the
“Pompeii Pumice” (AD 79). In order to compare the
different eruptions, volume calculations were standar-
dized using the methods of Pyle (1989) and Fierstein
and Nathenson (1992), whose results must be consid-
ered as strongly conservative (Rose 1993; Fierstein and
Nathenson 1993; Pyle 1995). The calculated volumes of
the fall deposits (Fig. 7) range from 1.5 km
3
(0.7 km
3
DRE) for the “Avellino Pumice” (Cioni et al. 1995b) to
4.4 km
3
(2.2 km
3
DRE) for the “Pomici di Base” erup-
tion (Bertagnini et al. 1998), which represents the
SVC’s largest event. The “Mercato” and “Pompeii”
eruptions produced similar volumes of ejecta (2–3 km
3
,
ca. 1–1.5 km
3
DRE). These values are generally lower
than previous estimates (Lirer et al. 1973; Sigurdsson et
al. 1985; Santacroce 1987), due to the different methods
and data used in previous papers.
New mapping of the area provides a detailed record
of the pyroclastic flow and surge deposits associated
with the Plinian eruptions and allows estimates of the
bulk volumes of these deposits, which are approximate-
ly 0.25 km
3
for the Mercato eruption, 0.5 km
3
for the
Avellino eruption, and 0.75 km
3
for the Pompei erup-
tion. The pyroclastic flow and surge deposits of the
Pomici di Base eruption are largely subordinate to the
plinian fall deposits and are dispersed only on the vol-
cano slopes.
211
Avellino
P. Campania
Nola
T. del Greco
Pompei
SommaV.
Ottaviano
Vesuvius
Caserta
Sarno
C. di Stabia
Sorrento Salerno
Battipaglia
Nocera Inf.
10
100
P
OMICI DI
B
ASE
Avellino
P. Campania
Nola
T. del
Greco Pompei
Ottaviano
Vesuvius
Caserta
Sarno
C. di Stabia
Sorrento Salerno
Battipaglia
Nocera Inf.
M
ERCATO
P
UMICE
Avellino
P. Campania
Nola
T. del
Greco Pompei
Ottaviano
Vesuvius
Caserta
Sarno
C. di Stabia Salerno
Battipaglia
Nocera Inf.
A
VELLINO
P
UMICE
Avellino
P. Campania
Nola
T. del
Greco Pompei
SommaV.
Ottaviano
Vesuvius
Caserta
Sarno
C. di Stabia
Sorrento Salerno Battipaglia
Nocera Inf.
P
OMPEII
P
UMICE
SommaV.
100
Sorrento
10
100
SommaV.
0 5 10 15
km
N
10
100
10 km 10 km
10 km
10 km
10
Fig. 7 New reconstructed 100- and 10-cm isopachs of the total
fallout deposits from the Plinian caldera-forming eruptions of Ve-
suvius
The “Pomici di Base” eruption and the western lobe
of the caldera
The deposits of the Pomici di Base are schematically
represented in Fig. 8. An eastward, widely dispersed
fall deposit records the establishment of a Plinian co-
lumn in the first phase of the eruption (Fig. 7). The de-
posit is compositionally zoned from basal white trachyt-
ic pumice to black latitic scoriae. A coarse-grained,
white, trachytic pumice fall deposit (unit U2; Bertagnini
et al. 1998) up to 10 m thick crops out on the western
side of the volcano at the foot of Piano delle Ginestre
(Fig. 8), suggesting proximity to the Plinian vent. The
emplacement of minor ash and pumice flow deposits,
derived from collapse of the sustained column, closed
the Plinian phase of the eruption. Furthermore, Bertag-
nini et al. (1998) recognized some minor pumice and
ash surge beds interlayered with the first phase of Plin-
ian fallout.
Within the upper part of the depositional sequence,
an impressive, coarse-grained, lithic-rich breccia domi-
nates the northwestern slopes of Mt. Somma. The brec-
cia, first described by Johnston Lavis (1884), is exposed
in the Vallone Molaro and Vallone di Pollena valleys,
where it crops out at approximately 700 m elevation
and pinches out against the old Somma lava flows. The
Molaro-Pollena breccia (MPB) directly overlies Plinian
pumice fall and pyroclastic flow deposits, forming a
wedge with a maximum thickness of 100 m. It is mas-
sive, matrix supported, and contains heterogeneous
lava blocks up to 3–4 m in diameter. At Vallone Mola-
ro the deposit has a planar to convex-upward surface,
212
Ottaviano
Rione Trieste
Somma V.
Sant'Anastasia
Pollena
San
Sebastiano
Torre del
Greco
1000
800
600
400
200
0 1
2 km
Vesuvius
Phreatomagmatic &
phreatic, flow and
fallout layers.
Lthic-rich
pyroclastic flow
(MPB) and
surges deposits .
Ash and pumice flow
deposits
Black latitic pumice
and scoria fall deposit
Ash and pumice flow
deposits [partial
column collapse]
White trachytic
pumice fall deposit
P
OMICI DI
B
ASE ERUPTION
(
CA
.
18,000
BP)
inferred
caldera rim
present scarp
prox.fall deposit
Molaro Breccia
(MB)
a
b
U1
U3a
U3b
to
U5
U2
Fig. 8a,b The Pomici di Base
eruption (18,300B180 BP). a
Generalized stratigraphic sec-
tion of the eruption deposits.
b Localization of the Molaro-
Pollena Breccia (MPB) out-
crop area and of proximal
coarse fallout deposits. Units
as proposed by Bertagnini et
al. (1998)
mantled by deposits of the following subplinian erup-
tion of the “Greenish Pumice” (16,000 years BP).
As a whole, MPB is a sigmoidal-shaped body, with
its lower reaches terminating at a steep front and con-
sisting of two main beds with a gradational contact. The
basal bed is an ashy massive layer, in places faintly lam-
inated, with a thickness that varies laterally from 20 to
30 cm. It is mainly composed of reddish coarse ash with
scattered coarse lithic fragments. The juvenile compo-
nent consists of dense, porphyritic, vitrophyric scoriae;
brown to yellow glass carries clinopyroxene and plagio-
clase phenocrysts with minor olivine and leucite micro-
phenocrysts. This basal bed grades into the overlying
coarse massive deposits, which reach approximately
100 m in thickness in the topographic lows. It shows
faint coarse-tail reverse grading. Lava blocks, heteroge-
neous in composition and supported in the matrix, are
the main components of the deposit. Lithic-rich lenses
are rarely present, forming weak laminations in the
body of the deposit. The platy fragments are weakly al-
igned, with their a (largest) axis generally horizontal or
dipping downslope at a very low angle. Reddish, oxid-
ized, hydrothermally altered lava fragments are abun-
dant. The matrix is formed by a lithic-rich, brownish-
red coarse ash containing dense, black, juvenile materi-
al, with pyroxene, plagioclase, and minor leucite. Fine
ash is very scarce. The lithic component of the matrix is
represented by lava fragments and oxidized scoria, to-
gether with minor micritic limestones commonly af-
fected by thermometamorphic recrystallization.
The textural features suggest that this unusual de-
posit results from a dense pyroclastic flow characterized
by laminar motion. It derives from en masse deposition
as the head of the flow reached the foot of the volcano.
A debris avalanche origin is excluded due to the lack of
megablocks with pre-existing internal structure, the
geometry and dispersal of the deposit, and the absence
of features such as jigsaw fractures and a hummocky
surface that are characteristic of debris avalanche de-
posits (Ui 1983; Siebert 1984; Siebert et al. 1987; Glick-
en 1991; Palmer et al. 1991). These features, the pres-
ence of dense juvenile material in the matrix, and the
abundance and homogeneity of the matrix in proximal
and distal outcrops seem to rule out the possibility that
the MPB represents a slide from the upper portion of
the volcano as proposed by Bertagnini et al. (1998).
This hypothesis appears unrealistic, considering the
strong homogeneity observed in the deposits and its
very small runout (a few hundred meters) on the volca-
no slopes.
The MPB has been found only in the northwestern
sector of the volcano. Massive and cross-laminated red-
dish ash deposits, lithologically resembling MPB ma-
trix, are widely dispersed on the northern slopes of Mt.
Somma, at the same stratigraphic position as MPB, and
they are covered by the final phreatomagmatic deposi-
ts. They represent surges associated with this phase of
the eruption.
The location of both the MPB and the proximal fall
deposits suggests that the AB segment of the caldera,
between the Cognoli di Giacca and Cognoli di Trocchia
ramparts (Fig. 3), represents a remnant of the “Pomici
di Base” caldera collapse. We suggest that the MPB de-
posits resulted from the deposition just outside the cal-
dera of a syn-caldera collapse, high-density pyroclastic
flow, probably generated by a boiling-over mechanism
along the collapsing ring structure. The magma in-
volved in this phase of the eruption may represent the
volatile-poor lower portion of the shallow reservoir
squeezed up by foundering caldera blocks. The lithic
213
Ottaviano
zero thickness
line
3-6 m
6-9 m
9-12 m
>12 m
spot occurrences
of pyroclastic
flows
(thickness as above)
Pyroclastic flow deposits and minor
stratified fallout layers
Metric, massive, ash and pumice
pyroclastic flow deposits
Lithic rich fallout deposit
White phonolitic clasti pumice and
minor lithics from the plinian
fallout
Fine fallout ashe
White phonolitic pumice from the
plinian fallout
Fine fallout ashes; topographically
controlled pyroclastic flows
N
Vesuvius
02
present scarp
inferred
caldera rim
M
ERCATO
P
UMICE ERUPTION
(
CA
8,000 BP)
old
active
km
Fig. 9 The Mercato eruption (ca. 8010B45 BP). Generalized
stratigraphic section of the pyroclastic deposits and isopach map
of the pyroclastic flow units
enrichment and the large quantities of hydrothermally
altered rocks derive from shattering of the collapsing
blocks. This promoted the disruption of a shallow hy-
drothermal system, facilitating the inflow of external
fluids in the plumbing system and the onset of the final
phreatomagmatic phase of the eruption.
The northern arc of the caldera: possible role of the
Mercato Pumice eruption
The northern sector of the caldera wall extends east-
ward from Cognoli di Trocchia to Cognoli di Levante
(BC in Fig. 3). In this sector the caldera wall reaches its
maximum height (1131 m). The 8010B45 BP “Mercato
Pumice” Plinian eruption is probably linked to the for-
mation of this part of the structure. The eruption was
first recognized by Johnston Lavis (1884); the name
“Mercato”, however, was first used by Walker (1977).
The same deposits were referred to as “pomici ge-
melle” (twin pumice beds) by Delibrias et al. (1979).
More recently they were studied by Rolandi et al.
(1993), who renamed the eruption as “Ottaviano”.
Such a proliferation of names has generated confusion
and, in the absence of strict nomenclature criteria, the
oldest name “Mercato Pumice” is preferred.
The Mercato sequence contains a Plinian fall depos-
it, accounting for more than 90% of the total erupted
volume, followed by lithic-rich flow and fall deposits
(Fig. 9). The Plinian fall deposit consists of three main
units, dispersed towards the east–northeastward
(Fig. 7), separated by ash falls and strongly channeled,
low-volume pumice flow deposits. It is generally ex-
tremely rich in juvenile material, except for the third
unit (Pomici and Proietti of Delibrias et al. 1979; Lc of
Rolandi et al. 1993), which consists of alternating lithic-
rich, mainly lava, coarse and fine fall layers. Several
outcrops of proximal pyroclastic flow deposits of the
Mercato Pumice eruption occur just outside the north-
ern rim of the caldera. Very coarse-grained, thick, val-
ley-ponded deposits are present on the northern slopes
(Fig. 9). These matrix-supported pyroclastic flow de-
posits are characterized by a high proportion of juve-
nile material. The massive flow units, often showing
coarse-tail reverse grading of lithic clasts, reach a total
thickness of 15–20 m. The lower flow units are pumice
rich and generally contain ground surge deposits. The
upper units are characterized by an upward-increasing
concentration of lithic clasts from decimeters to, rarely,
1 m in diameter. Two main types of clasts are present;
lava (ca. 80–90%) and fragments of silicified carbonate
breccia, possibly from the clearing of old breccia-filled
conduit(s). These deposits continuously cover the
northern slopes of Mt. Somma and occur in several
deep quarries in the eastern and southern sectors. They
are at present mainly covered by a very thick pile of
recent deposits (younger than 3 ka). Thick Mercato py-
roclastic flow deposits were also recognized in bore-
holes drilled in the western sectors of the circum-Vesu-
vian area (Di Vito 1995).
The stratigraphic sequence of the Mercato Pumice is
dominated by the products of its Plinian phase (the
three main fallout units and some associated pumice
flow deposits), which have a homogeneous phonolitic
composition. With respect to the other Plinian erup-
tions of Vesuvius, the final phreatomagmatic activity is
less developed and is dominated by flow and surge de-
posits, alternating with fallout layers, that are restricted
to the volcano slopes. The average lithic content of
these deposits is approximately 40% by weight (Fig. 4
214
in Rolandi et al. 1993), a value greatly exceeded in all
the deposits of the final phreatomagmatic phases of
Pomici di Base and, especially, Avellino and Pompeii
Pumice (see below). No deposits exist that can be clear-
ly associated with a caldera collapse. On the other
hand, the large volume of erupted products and their
strong compositional homogeneity suggest that the top-
most part of a large, evolving magma body was tapped
during the eruption, promoting the necessary condi-
tions for a caldera collapse. As a whole, the dispersal of
the fallout tephra, centered on the volcano, and the ra-
dial distribution of the flow deposits suggest an axial
position on the old volcano for the Mercato vent. The
presence of valley-ponded, coarse flow deposits with
breccia lenses high on the outer, northern slopes of the
volcano (Fig. 8), is possible evidence that the formation
of the northern caldera wall was connected to the Mer-
cato eruption. In this view, the relative scarcity of deep-
seated lithic clasts in these deposits agrees better with
significant enlargment of the shallowest part of the col-
lapsing structure than with the squeezing up of magma
after foundering of caldera blocks into the magmatic
reservoir.
The Piano delle Ginestre and the 3400-year BP
Avellino Plinian eruption
The elliptical structure of Piano delle Ginestre enlarges
the SVC to the west and appears nested in the older
“Pomici di Base” caldera (Fig. 3). The areal distribu-
tion and facies variations of the Avellino Pumice prod-
ucts indicate that the vent area was in a position coin-
ciding with the Piano delle Ginestre on the western
slope of the volcano and probably related to the frac-
ture system of the older “Pomici di Base” caldera.
The sequence of events during the Avellino eruption
is similar to that of the other Vesuvius Plinian erup-
tions (Fig. 10). Three main phases of activity can be dis-
tinguished according to the deposits: an opening phase,
a Plinian fallout phase, and a final phreatomagmatic
phase (Cioni et al. 1995b). The opening phase (EU1 in
Fig. 10a) is marked by thin, crystal-rich fall layers dis-
persed east–northeastward, and by small, coarse-
grained, pyroclastic flow deposits. These are coarse, lit-
hic-rich, massive, topographically controlled, pumice
and ash deposits showing marked variations in local
thickness (0–2 m). Their deposition is strictly confined
to the western slopes of Piano delle Ginestre, pinching
out at approximately 150–200 m elevation. The Plinian
phase of the eruption produced a compositionally
layered fall deposit, from basal white phonolitic to gray
tephriphonolitic pumice, dispersed east–northeastward
and interrupted by an ash layer related to partial co-
lumn collapse. Close to the northern rim of Piano delle
Ginestre (sections A, B, C in Fig. 10c), the products of
the Plinian phase consist of thick (up to 10 m), coarse
pumice fall deposits. The tephriphonolitic composition
of the pumice relates these breccia layers to the EU3
unit of Cioni et al. (1995b). The strongly negatively
skewed, polymodal and poorly sorted grain-size distri-
bution (Fig. 10b) is typical of proximal fall deposits, in
agreement with the abundance of ballistic blocks.
These deposits are strongly enriched in fragments of
crystalline rocks (cumulate, skarn and syenite) as well
as in accidental clasts from the sedimentary basement
(carbonate rocks). The abundance of syenitic, metaso-
matic, and thermometamorphic blocks suggests the on-
set of the destabilization of the magma chamber roof
during the final stages of the Plinian phase. Grain size,
thickness, and lithic content decrease regularly from
the flanks of the Piano delle Ginestre eastward
(Fig. 10c), and the features of the deposit change grad-
ually from those typical of near-vent facies to those of a
“normal” pumice fall deposit (sections D and E in
Fig. 10b, c). Therefore, these deposits indicate very
clearly the Piano delle Ginestre as the Avellino vent
area.
The phreatomagmatic phase of the eruption was
characterized by high- and medium-energy explosions
related to a pulsating column (Cioni et al. 1995b). On
the western and northwestern sectors of the volcano,
the products related to this phase consist mostly of fine-
grained, lithic-rich, dune-bedded surge deposits (EU5
in Fig. 10a) overlain by a sequence of thin, massive to
cross-laminated layers with minor lithic-rich fall in-
terbeds (EU6). The deposits of the most energetic
eruptive unit of this phase (EU5) reach distances
greater than 10 km from the vent, as far as Naples. The
maximum thicknesses occur on the outer flanks of the
Piano delle Ginestre, where the EU6 deposits form
wedge-shaped bodies dipping 20–307 outward, with a
radial arrangement from the source. The southern and
eastern sectors of the volcano were reached only by wet
ash clouds, which deposited thin pisolitic ash layers. As
a whole, the dispersal of products confirms the vent lo-
cation on the seaward sector of the old volcano, in the
Piano delle Ginestre area.
The occurrence, in the opening EU1 flow deposits,
of abundant xenolithic blocks of phonolitic yellow tuff
containing reed molds from the final phases of the Mer-
cato eruption confirms that the Avellino vent was in-
side a pre-existing (probably swampy) depression filled
by Mercato deposits. The western lower rim of the de-
pression, close to the vent area, was easily surmounted
by pyroclastic flows and surges generated during the
eruption. The southward and eastward dispersal of flow
deposits was prevented by the higher rims of the pre-
existing caldera.
The morphology of the volcano after the Avellino
eruption can be inferred from the present shape of the
Piano delle Ginestre structure and from the geology of
its flanks. The EU5 and EU6 deposits form the cres-
cent-shaped relief of Observatory Hill and the pyro-
clastic wedge of Cappella Bianchini (Fig. 3). They rep-
resent remnants of a giant tuff cone constructed during
the phreatomagmatic phase of the eruption, resulting in
215
S.Anastasia
S.Sebastiano
Ercolano
Torre del
Greco
S. Vesuviana
02
km
N
> 6 meters
4-6 meters
2-4 meters
0-2 meters
B
E
a
b
cA
C
D
SectionA
marble
limestone
crystalline rocks
cognate
juvenile
Section C
Section B
Section D
Section E
0
5
10
15
20
25
0
5
10
15
20
0
10
20
30
0
10
20
30
40
0
10
20
30
-8 -4 0 4 Φ
wt %
Pulsating phreatomagmatic activity; sequence of
pyroclastic flows in some paleovalleys of the NW
sector, interlayered with lithic rich fallout beds
High energy phreatomagmatic phase; surge deposits
in the western sector. Formation of a tuff ring
Grey pumice fallout with a NE-trending dispersal.
Deposition of an ash flow due to a partial column
collapse during the final stages of the Plinian phase.
Lithic fallout breccia deposits dispersed near the vent.
Possible partial destabilization of the magma chamber
White pumice fallout with an ENE-trending dispersal
OPENING PHASE
Ash fallout and minor, valley-ponded ash flows
EU 6
EU 5
EU 3
EU 2
EU 3pf
EU 1
PLINIAN PHASE
PHREATOMAGMATIC PHASE
a
b
EU3 PROXIMAL DEPOSITS AVELLINO PUMICE ERUPTION (3,400 BP)
P. delle
Ginestre
EU 4 transient resuming of the column
b
present scarp
inferred
caldera rim
old
active
Vesuvius
Fig. 10a–c The Avellino eruption (3360B40 BP). a Generalized
stratigraphic section of the pyroclastic deposits. b Grain-size and
component analyses of proximal gray pumice fall deposits. c Iso-
pach map of the pyroclastic flow deposits and inferred caldera
rim
a seaward growth of the volcano. These deposits could
have mantled the rim of a caldera depression formed
during the final stages of the Plinian phase, nested in-
side the Pomici di Base caldera. A similar situation has
been described at Santorini volcano (Sparks and Wil-
son 1990) and at Ambrym volcano (Robin et al.
1993).
216
The caldera of the 79 AD Pompeii eruption
General consensus exists presently on the stratigraphy
of the 79 AD eruption deposits (Sigurdsson et al. 1985;
Cioni et al. 1992; Lirer et al. 1993), but little attention
has been focused on the timing of formation of the cal-
dera. Sigurdsson et al. (1985) proposed a caldera col-
lapse phase in association with the deposition of a very
coarse debris flow on the southern flanks of the volca-
no. Cioni et al. (1992) subdivided the deposits of the
eruption into three phases with eight main eruption
units (Fig. 11a). The opening phase, leaving only a few
centimeters of pisolitic ash fall and minor surge beds
(EU1), was followed by the Plinian phase, mostly con-
sisting of tephra fallout (white and gray pumice layers,
EU2 and EU3) from a sustained column. According to
Pliny the Younger’s letters to Tacitus and the chronolo-
gy proposed by Sigurdsson et al. (1982), the Plinian
phase lasted no longer than 20 h. At least four partial
column collapses occurred during this phase the end of
which was marked by a total column collapse leading to
the deposition of high aspect ratio (HARI-type) pu-
mice flows channeled in several valleys. The eruption
renewed (EU4) with a short-lived plinian column that
ended with the generation of a pyroclastic flow the
widespread deposits of which have sedimentologic fea-
tures suggesting emplacement by a turbulent cloud.
This event coincided with the beginning of the caldera
collapse (Cioni et al. 1992). The EU4 deposit is strongly
enriched in deep lithic components, such as skarn and
marble from the thermometamorphic and metasomatic
halo of the magma chamber, and cumulates. On the
morning of 25 August, as reported by Pliny the Young-
er in his second letter, a very strong earthquake oc-
curred, coincident with the descent of some ash clouds
as far as Cape Misenum and Stabiae. This event proba-
bly marked the start of the collapse of the magma
chamber roofs. All the deposits following the Plinian
phase (EU4 to EU8) are characterized by a sharp in-
crease in the proportion of ejected lithic clasts (cognate
and accidental) and by a shift from dry to wet textural
features, related by Barberi et al. (1989) to the onset
and progressive increase of magma–water interaction.
As for the Pomici di Base eruption, we propose that the
interaction was induced by caldera collapse, after the
destabilization of the shallow plumbing system and the
consequent fracturing of the wall rocks of the cham-
ber.
The lithic ejecta from the chamber halo (skarn, mar-
ble, and subvolcanic rocks) generally show high porosi-
ties with miarolitic structures and were affected by
high-temperature hydrothermal circulation (300–
600 7C; Fulignati et al. 1995). The petrography of the
volcanic and sedimentary lithic clasts indicates the de-
velopment, over the roof of the magma chamber, of
only medium- and low-temperature hydrothermal sys-
tems (from argillic to phillic and rarely to calc-alumi-
nium silicate, indicating temperatures of 100–300 7C;
Fulignati et al. 1995).
Some proximal coarse, lithic-rich pyroclastic flow
deposits (EU6) are interlayered in the generally fine-
grained products of the final phreatomagmatic phases.
These deposits, discontinuously exposed on the south-
eastern slopes of the volcano, mark the shift from “dry”
(EU4, EU5) to “wet” (EU7, EU8) phreatomagmatic
products. At least three main EU6 flow lobes exist,
channeled inside paleovalleys in the Boscoreale-Terzig-
no area and in the Cappella Bianchini area. The field
features of EU6 deposits are quite peculiar. At Pozzelle
Quarry (B in Fig. 11b,c) they are represented by a very
thick (up to 10 m) massive to faintly laminated, matrix-
supported pyroclastic breccia, made mainly of block-
sized lithic ejecta (up to 60 vol.%). This corresponds to
the pyroclastic debris flow deposit described by Si-
gurdsson et al. (1985). The xenolithic fragments are
representative of at least 2000 m of subsurface litholo-
gy, as drilled by the geothermal well Trecase 1 (Bernas-
coni et al. 1981). Such a huge variety suggests that the
eruptive mixture, during its rise to the surface, sampled
practically all the stratigraphic levels cut by the conduit.
This cannot be the result of strong, constant erosive ca-
pability of the rising magma mixture during its transit
through the volcanic conduit (also excluded by the cal-
culations of Macedonio et al. 1994) but instead reflects
the extensive fracturing, associated with caldera col-
lapse, of the rocks overlying the magma chamber.
The three different EU6 flow lobes are not homoge-
neous in composition. The easternmost lobe (Zabatta
quarry, A in Fig. 11b,c) is markedly enriched in cumu-
late and intrusive fragments, whereas the western lobe
is very poor in deep lithic clasts as well as in juvenile
fragments. These lithologic differences and the spatial
arrangement of the EU6 deposits are suggestive of the
emission from an annular multi-vent system, which
could coincide with the C–D lobe of the caldera
(Fig. 3).
The isopach map of the AD 79 pyroclastic flow de-
posits gives some indications about the pre-eruptive to-
pography of the volcano. Most of the pyroclastic flows
related to the Plinian column collapse overrode the
present Somma ridge, leaving deposits with an almost
radial arrangement (Fig. 11c). Their deposition began
between 600 and 250 m elevation, generally higher on
the northern and western slopes of the volcano. The
slope angle at the onset of flow deposition was approx-
imately 157 for the western and eastern flows and at
least 207 for the northern flows. The occurrence of
northern flow deposits on such a steep slope agrees
with the presence of a topographic barrier (a Paleosom-
ma rim), which decreased the energy of the overriding
pyroclastic flows. The occurrence of pyroclastic flow
deposits at altitudes greater than 600 m on the western
slope of the volcano also suggests that the old caldera
rim was already breached on the seaward flank of the
volcano, in the area of Piano delle Ginestre (Pomici di
Base and Avellino Pumice caldera collapses). From this
breach the low surge clouds related to the EU1 exited
the caldera, while being confined in the other direc-
217
White pumice fallout with a S-trending dispersal axis. First
pyroclastic flows, which reach Herculaneum, at the end of this phase.
Grey pumice fallout with a SE-trending dispersal axis. Partial
burying of the settlements in the south. Pyroclastic flows
generated by partial column collapse, which ravage the Vesuvius
slopes, reaching and burying Herculaneum. The Plinian phase
is closed by a total column collapse.
Beginning of the caldera collapse phase. Strong earthquakes.
Turbulent, pyroclastic flow with a nearly radial dispersion.Total
ravaging of the Pompeii-Stabiae area. Dense ash clouds at Miseno.
Ash fallout and ash flows on the volcano.
Phreatomagmatic "dry" pyroclastic flows channeled onto the
slopes of the volcano.
Definitive collapse of the shallow pumbling system. Debris
flows in some main valleys on the eastern slopes of the volcano.
High energy pyroclastic flow, on the southern and eastern
sectors of the volcano. The ash cloud probably reaches Miseno.
Final phreatomagmatic "wet" phase of the eruption. Low energy
ash clouds, with a prevalent southern dispersion.
Fig. 11a–c The Pompei eruption (79 AD). a Generalized stratigraphic section of the pyroclastic deposits. b Grain-size and component
analyses of breccia deposits from A and B sections. c Isopach map of the pyroclastic flow deposits and inferred caldera rim
218
C
Terzigno
Rione Trieste
Torre del
Greco
Casilli
N
1000
800
600
400
100
1200
140
0
1600
0
200
Sant’Anastasia Somma V.
Ottaviano
2 km
Ercolano
Portici
San
Sebastiano
Cercola
Pollen
a
San Giuseppe V.
400
600
800
1200
1600
Vesuvius
A
Terzigno
Rione Trieste
Torre del
Greco
Casilli
N
1000
800
600
400
100
1200
140
0
1600
0
200
Sant’Anastasia Somma V.
Ottaviano
2 km
Ercolano
Portici
San
Sebastiano
Cercola Pollen
a
San Giuseppe V.
400
600
800
1200
1600
Vesuvius
B
2 km
ca. 18,000 BP
after Pomici di Base eruption
ca. 8,000 BP
after Mercato Pumice eruption
> 18,000 BP
the old stratocone
200
600
1000
1400
1800
m a.s.l.
200
600
1000
1400
1800
m a.s.l.
2 km
2 km
200
600
1000
1400
1800
m a.s.l.
Terzigno
Rione Trieste
Torre del
Greco
Casilli
N
1000
800
600
400
100?
1200
1400
1600
0
200
Sant’Anastasia Somma V.
Ottaviano
2 km
Ercolan
o
Portici
San
Sebastiano
Cercola Pollena
San Giuseppe V.
400
600
800
1400
1600
1400
1600
1200
Fig. 12A–F Reconstruction of the morphologic evolution of
Somma-Vesuvius caldera. A–F The ideal reconstructed topogra-
phy, a sketch of the volcano (view from west), and the morpho-
logic cross section
219
Terzigno
Rione Trieste
Torre del
Greco
Casilli
N
100
0
800
600
400
100
1200
1400
160
0
0
200
Sant’Anastasia
Somma V.
Ottaviano
2 km
Ercolano
Portici
San
Sebastian
o
Cercola
Pollena
San Giuseppe V.
400
600
800
1200
140
0
1600
1400
1600
E
D
Terzigno
Rione Trieste
Torre del
Greco
Casilli
N
1000
800
600
400
100?
120
0
1400
1600
0
200
Sant’Anastasia Somma V.
Ottaviano
2 km
Ercolan
o
Portici
San
Sebastian
o
Cercola
Pollena
San Giuseppe V.
400
600
800
1400
160
0
1400
1600
1200
F
Terzigno
San Giuseppe V.
Ottaviano
Rione Trieste
Somma V.
Sant’Anastasia
Pollena
San Sebastiano
Cercola
Portici
Torre del
Greco
Casilli
N
1000
800
600
400
200
Ercolano
0
2 km
ca. 3,400 BP
after Avellino Pumice eruption
AD 79
after Pompeii Pumice
eruption
Present
2 km
200
600
1000
1400
1800
m a.s.l.
2 km
200
600
1000
1400
1800
m a.s.l.
2 km
20
0
60
0
1000
1400
1800
m a.s.l.
220
tions. The absence of EU6 deposits on the northern
slope of the volcano can be similarly interpreted to in-
dicate a pre-existing topographic barrier (a high caldera
rim) that hampered the passage of these very dense
flows.
Summary and conclusions
The SVC results from several vertical collapses of an
old stratovolcano, the original apex of which was ap-
proximately 500 m north of the present Vesuvius crat-
er, at 1600–1900 m elevation. Caldera collapse accom-
panied the four Plinian eruptions that occurred in the
last ca.18,000 years (18,300 BP “Pomici di Base”, 8000
BP “Mercato Pumice”, 3400 BP “Avellino Pumice” and
AD 79 “Pompeii Pumice”). Figure 12 illustrates the
main steps of the morphologic evolution we have re-
constructed.
Caldera-forming Plinian eruptions of Vesuvius re-
sult from emptying of periodically refilled shallow mag-
ma chambers hosted, according the lithic clasts, in Me-
sozoic carbonate units several kilometers thick the top
of which is 2–3 km below the volcano (Cioni et al.
1995a, 1995b, 1998). Different geobarometric data
(Barberi and Leoni 1980; Barberi et al. 1981; Metrich
1985; Santacroce 1987) suggest similar depths of 3–6 km
for Pompeii and Avellino chambers. The depths of the
Pomici di Base and Mercato chambers are less con-
strained.
Conservative volume estimates of the products
ejected during each event range from 2.0 to 4.5 km
3
(1
to 2.5 km
3
DRE). The Plinian fall deposits represent
more than 75% of the total erupted volume, with a lit-
hic content of the deposits of 10–15 wt.%. These values
can be discussed in terms of minimum dimensions of
chambers emptied by the eruptions. In the most conser-
vative assumption of totally emptying the shallow res-
ervoirs, and assuming an ellipsoidal shape, the volumes
of ejected magma and the size of the collapsed area
suggest that the magma chambers had an aspect ratio
(vertical vs horizontal) of 0.25–0.3. Cioni et al. (1998)
proposed that Vesuvius magma chambers evolve, with
increasing volume and age, from prolate to subequant
while changing their internal layering:
1. Initial stage. Low-volume, high-aspect-ratio chamber
with a nearly homogeneous mafic melt
2. Young stage. Medium-volume and aspect-ratio
chamber, with continuous gradation from mildly
evolved to salic melt
3. Mature stage. High-volume, low-aspect-ratio cham-
ber, with a lower, convective, mildly evolved portion
and an upper, stratified, salic one.
In this scheme, major caldera-forming eruptions are
related to large, low-aspect-ratio mature magma cham-
bers. In the Avellino eruption, the calculated aspect ra-
tio is very low (~0.2). This could suggest that the erup-
tion left its reservoir partially untapped, as also indi-
cated by petrologic data (Civetta et al. 1991; Civetta
and Santacroce 1992; Cioni et al. 1995a).
The caldera-forming eruptions are characterized by
complex deposits that can be divided, after a phreato-
magmatic opening, into two phases: an initial magmatic
phase (sustained Plinian column associated with partial
or total column collapses) responsible for the ejection
of most of the juvenile material, followed by a complex,
phreatomagmatic phase. The onset of each caldera col-
lapse coincided with the beginning of the second phase.
As a consequence of the extensive fracturing of the
roof rocks accompanying collapse of the magma cham-
ber, many lithic clasts from the outer shell of the cham-
ber and its apophysis (syenitic rocks, skarns and ther-
mometamorphic limestone), as well as from the upper
volcanic and sedimentary pile, are generally found in
these deposits. At proximal sites they consist of coarse
breccia which results from emplacement of dense pyro-
clastic flows (Pomici di Base and Pompei eruptions),
and of coarse, lithic-rich fallout deposits (Avellino
eruption).
The mineralogic and fluid inclusion data on ejected
xenoliths indicate a complex circulation of fluids in the
wall rocks of the chambers, ranging from hydrother-
mal–magmatic (gases and brines with temperatures up
to 600 7C) to hydrothermal (liquid dominated, between
100 and 300 7C) systems. The caldera collapse events,
which reflect the destabilization of the magma cham-
ber, imply involvement of these fluids in the eruption.
Their sudden decompression, as well as the interaction
between ground water and magma induced by the frac-
turing of the chamber walls (Sheridan et al. 1981; Bar-
beri et al. 1988), enhance the explosivity of the eruption
and serve to propel the gas-particle mixture, accounting
for the extremely high energy of these stages of the
eruptions.
In the scheme proposed by Scandone (1990), Som-
ma-type (Krakatoan) calderas preferentially result
from chaotic collapses, rather than from piston-like,
block collapses typical of Valles-type calderas. The ver-
tical throws (1100 m) of the caldera blocks, all accumu-
lated along single faults, and the present morphology
(suggesting nearly circular contours for all the four col-
lapses) are in poor agreement with a completely chaotic
collapse. Moreover, the analog experiments of Marti et
al. (1994) show that the emptying of balloon-like mag-
ma chambers results in a single fault-bounded depres-
sion, whereas the repeated extraction of magma from
partially nested reservoirs could create a scalloped out-
line. Self-potential data (Di Maio et al. 1998) suggest
the presence of strong horizontal gradients near the cal-
dera boundaries, which appear in good agreement with
the existence of a single fault-bounded depression.
Seismic and gravity data are less conclusive, even if all
the seismicity (De Natale et al. 1998) is confined within
the proposed caldera volume, and the shallow, vertical
discontinuities in the wave velocity shown by the 2D
seismic tomography (Zollo et al. 1998) appear to coin-
cide with the caldera faults. We therefore conclude that
221
the present outer border of the SVC results from the
morphologic evolution of the rims of a multicyclic,
nested caldera formed by repeated collapses after an
important emptying of shallow level, mature magma
chambers during Plinian outbursts.
The lithologic homogeneity of the volcano basement
may be the main reason for the similar response (in the
sense of shape and type of collapse) shown by the Ve-
suvius magmatic systems to the large emptying events
during Plinian eruptions. The presence of a thick, high-
ly fractured and permeable carbonate basement hosting
the magma chambers probably accounts for the recur-
rent dynamics of Vesuvius caldera collapses. The capa-
bility of the host rocks to provide large masses of exter-
nal fluids inducing deep, highly efficient “magma–wa-
ter” interaction actually represents a Vesuvius peculiar-
ity, prevented in continental stratovolcanoes with low-
permeability, siliceous basements.
Acknowledgements The research was sponsored by CNR (Na-
tional Council of Research of Italy), “Gruppo Nazionale per la
Vulcanologia.” The authors are indebted to S. Carey, J. Marti and
J. Luis Marcias, whose critical reviews significantly improved the
quality of the paper, as well as to D. Andronico and R. Sulpizio
for their help during the field work.
References
Andronico D, Calderoni G, Cioni R, Sbrana A, Sulpizio R, San-
tacroce R (1995) Geological map of Somma-Vesuvius Volca-
no. Per Mineral 64: 77–78
Arnò V, Principe C, Rosi M, Santacroce R, Sbrana A, Sheridan
MF (1987) Eruptive history. In: Santacroce R (ed) Somma-
Vesuvius Quaderni de La Ricerca Scientifica 114, vol 8, CNR
Roma, pp 53–104
Barberi F, Leoni L (1980) Metamorphic carbonate ejecta from
Vesuvius plinian eruptions: evidence of the occurrence of
shallow magma chambers. Bull Volcanol 43: 107–120
Barberi F, Bizouard H, Clocchiatti R, Metrich N, Santacroce R,
Sbrana A (1981) The Somma-Vesuvius magma chamber: a pe-
trological and volcanogical approach. Bull Volcanol
44:295–315
Barberi F, Navarro JM, Rosi M, Santacroce R, Sbrana A (1988)
Explosive interaction of magma with ground water: insights
from xenoliths and geothermal drillings. Rend SIMP
43:901–926
Barberi F, Cioni R, Rosi M, Santacroce R, Sbrana A, Vecci R
(1989) Magmatic and phreatomagmatic phases in explosive
eruptions of Vesuvius as deduced by grain-size and composi-
tional analysis of pyroclastic deposits. J Volcanol Geotherm
Res 38:287–307
Bernasconi A, Bruni P, Gorla L, Principe C, Sbrana A (1981) Ri-
sultati preliminari dell’esplorazione geotermica profonda
nell’area vulcanica del Somma-Vesuvio. Rend Soc Geol It
4:237–240
Bertagnini A, Landi P, Rosi M, Vigliargio A (1998) The Pomici di
Base plinian eruption of Somma-Vesuvius. J Volcanol Geo-
therm Res 83 : 219–239
Bullard FM (1978) Volcanoes of the Earth. University of Texas
Press, Austin, pp 1–579
Cioni R, Marianelli P, Sbrana A (1992) Dynamics of the AD 79
eruption: stratigraphic, sedimentologic and geochemical data
on the successions of the Somma-Vesuvius southern and east-
ern sectors. Acta Vulcanol 2 : 109–124
Cioni R, Civetta L, Marianelli P, Metrich N, Santacroce R, Sbra-
na A (1995a) Compositional layering and syneruptive mixing
of a periodically refilled magma chamber: the AD 79 plinian
eruption of Vesuvius. J Petrol 36:739–776
Cioni R, Morandi D, Sbrana A, Sulpizio R (1995b) L’eruzione
delle Pomici di Avellino: aspetti stratigrafici e vulcanologici.
Atti del Convegno “L’eruzione vesuviana delle Pomici di Av-
ellino e la facies di Palma Campania”. Centro Univ Europeo
per i Beni Culturali, pp 41–53
Cioni R, Marianelli P, Santacroce R (1998) Reconstructing the
thermal and compositional evolution of shallow magma cham-
bers through melt inclusions in pyroxene. Examples from Ve-
suvius. J Geophys Res 103: 18277–18294
Civetta L, Santacroce R (1992) Steady-state magma supply in the
last 3400 years of Vesuvius activity. Acta Vulcanol
2:147–159
Civetta L, Galati R, Santacroce R (1991) Magma mixing and con-
vective compositional layering within the Vesuvius magma
chamber. Bull Volcanol 53: 287–300
Delibrias G, Paola GM di, Rosi M, Santacroce R (1979) La storia
eruttiva del complesso vulcanico Somma-Vesuvio ricostruita
dalle successioni piroclastiche del Monte Somma. Rend Soc It
Mineral Petrol 35 : 411–438
di Maio R, Mauriello P, Patella D, Petrillo Z, Piscitelli S, Siniscal-
chi A (1998) Electric and electro-magnetic outline of the
Mount Somma-Vesuvius structural setting. J Volcanol Geo-
therm Res 82 : 219–238
di Vito MA (1995) Distribuzione dei depositi dell’eruzione delle
Pomici di Avellino (XVII-XVIII sec aC) nell’area napoletana
e ricostruzione del paleoambiente prima e dopo l’eruzione.
Proceedings Intern Meeting “L’eruzione vesuviana delle Pom-
ici di Avellino e la facies di Palma Campania (Bronzo Antico).
Centro Studi Eur J Berard, Ravello
Fierstein J, Nathenson M (1992) Another look at the calculation
of fallout tephra volumes. Bull Volcanol 54: 156–167
Fierstein J, Nathenson M (1993) Reply to comment by W.I. Rose.
Bull Volcanol 55: 375–378
Fulignati P, Gioncada A, Sbrana A (1995) The magma chamber
related hydrothermal system of Vesuvius: first mineralogical
and fluid inclusion data on hydrothermalized subvolcanic and
lavic samples from phreatomagmatic eruptions. Per Mineral
64:185–187
Glicken H (1991) Sedimentary architecture of large volcanic-de-
bris avalanches. SEPM Spec Publ 45:99–106
Johnston Lavis HJ (1884) The geology of the Mt. Somma and Ve-
suvius: being a study of volcanology. Q J Geol Soc Lond
40:35–149
Lirer L, Pescatore T, Booth P, Walker GPL (1973) Two plinian
pumice-fall deposits from Somma-Vesuvius, Italy. Geol Soc
Am Bull 84: 759–772
Lirer L, Munno R, Petrosino P, Vinci A (1993) Tephrostratigra-
phy of the A.D.79 pyroclastic deposits in perivolcanic areas of
Mt. Vesuvio (Italy). J Volcanol Geotherm Res 58:133–149
Macdonald GA (1972) Volcanoes. Prentice-Hall, New Jersey pp
1–503
Macedonio G, Dobran F, Neri A (1994) Erosion processes in vol-
canic conduits and application to the AD 79 eruption of Vesu-
vius. Earth Planet Sci Lett 121: 137–152
Marti J, Ablay GJ, Redshaw LT, Sparks RSJ (1994) Experimental
studies of collapse calderas. J Geol Soc Lond 151 : 919–929
Metrich N (1985) Mechanismes d’evolution a l’origine des roches
volcaniques potassiques d’Italie Centrale et Meridionale. Ex-
emples du Mt. Somma-Vesuve, des Champs Phlegreens et de
l’ile de Ventotene. Thèse, Université de Paris Sud, Centre
d’Orsay
Milia A, Mirabile L, Torrente MM, Dvorak JJ (1998) Volcanism
offshore of Vesuvius volcano in Naples Bay. Bull Volcanol
50:404–413
Natale G de, Capuano P, Troise C, Zollo A (1998) Seismicity at
Somma-Vesuvius and its implications for the 3D tomography
of the volcano. J Volcanol Geotherm Res 82: 175–197
222
Nazzaro A (1997) Il Vesuvio. Storia eruttiva e teorie vulcanolog-
iche. Liguori, Napoli, pp 1–362
Ollier C (1988) Volcanoes. Blackwell, Oxford, pp 1–228
Palmer BA, Alloway BV, Neall VE (1991) Volcanic-debris-aval-
anche deposits in New Zealand: lithofacies organization in un-
confined, wet-avalanche flows. SEPM Spec Publ 45: 89–98
Pyle DM (1989) The thickness, volume and grain size of tephra
fall deposits. Bull Volcanol 51 : 1–15
Pyle DM (1995) Assessment of the minimum volume of tephra
fall deposits. J Volcanol Geotherm Res 69: 379–382
Rittmann A (1967) I vulcani e la loro attività. Cappelli, Firenze,
pp 1–359
Robin C, Eissen JP, Monzier M (1993) Giant tuff cone and 12 km
wide associated caldera at Ambrym Volcano (Vanuatu, New
Ebrides Arc). J Volcanol Geotherm Res 55: 225–238
Rolandi G, Maraffi S, Petrosino P, Lirer L (1993) The Ottaviano
eruption of Somma-Vesuvius (8000 years BP): a magmatic al-
ternating fall and flow-forming eruption. J Volcanol Geo-
therm Res 58 : 43–65
Rose WI (1993) Comment on “another look at the calculation of
tephra fallout volumes” by Judy Fierstein and Manuel Na-
thenson. Bull Volcanol 55:372–374
Santacroce R ed (1987) Somma-Vesuvius. Somma-Vesuvius
Quaderni de La Ricerca Scientifica 114, vol 8, CNR Roma, pp
1–251
Scandone R (1990) Chaotic collapse of calderas. J Volcanol Geo-
therm Res 42 : 285–302
Sheridan MF, Barberi F, Rosi M, Santacroce R (1981) A model
for Plinian eruptions of Vesuvius. Nature 298: 282–285
Siebert L (1984) Large volcanic debris avalanches: characteristics
of source areas, deposits, and associated eruptions. J Volcanol
Geotherm Res 22 : 163–197
Siebert L, Glicken H, Ui T (1987) Volcanic hazards from Bezy-
mianny-type and Bandai-type eruptions. Bull Volcanol
49:435–459
Sigurdsson H, Cashdollar S, Sparks RSJ (1982) The eruption of
Vesuvius in AD 79: reconstruction from historical and volca-
nological evidence. Am J Archaeol 86 : 39–51
Sigurdsson H, Carey S, Cornell W, Pescatore T (1985) The erup-
tion of Vesuvius in AD 79. Nat Geogr Res 1: 332–387
Simkin T, Siebert L (1994) Volcanoes of the world. Geosciences
Press, Tucson, Arizona, pp 1–349
Sparks RSJ, Wilson CJN (1990) The Minoan deposits: a review of
their characteristics and interpretation. In: Hardy DA (ed)
Thera and the Aegean World III, vol 2. Thera Foundation,
London, pp 89–99
Stothers RB, Rampino MR (1983) Volcanic eruptions in the Me-
diterranean before AD 630 from written and archaeological
sources. J Geophys Res 88: 6357–6371
Ui T (1983) Volcanic dry avalanche deposits:identification and
comparison with nonvolcanic debris stream deposits. J Volca-
nol Geotherm Res 18: 135–150
Ventura G, Vilardo G, Tammaro U (1995) The Monte Somma
earthquake-induced slides (July to August 1995, Somma Ve-
suvius volcano): an example of caldera rim recession. EOS
Trans Am Geophys Union Fall Meeting 1995 : F676
Walker GPL (1977) Metodi geologici per la valutazione del ris-
chio vulcanico. Atti del convegno ”I vulcani attivi dell’area
napoletana“ Reg Campania, Napoli, pp 53–60
Walker GPL (1984) Downsag calderas, ring faults, caldera sizes
and incremental caldera growth. J Geophys Res
89:8407–8416
Williams H, McBirney AR (1979) Volcanology. Freeman, San
Francisco, pp 1–396
Zollo A, Gasparini P, Virieux J, Biella G, Boschi E, Capuano P,
Franco R de, Dell’Aversana P, Matteis R de, Natale G de,
Iannaccone G, Guerra I, Le Meur H, Mirabile L (1998) An
image of Mt. Vesuvius obtained by 2D seimic tomography. J
Volcanol Geotherm Res 82: 161–173
